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  1. #1
    just another gosling Carbonfiberboy's Avatar
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    CoMo Speedster rear dropout spacing

    I purchased a used Speedster, supposedly a 2004 (I don't know how to tell), about 18 months ago. It's a great bike. It has Chris King hubs with STI 9-speed cogs. The rear hub engagement became sticky so we had trouble sometimes getting the captain's pedal in exactly right spot to start off. I downloaded the CK owners manual and pulled off the rear wheel. The CK manual said that my axle had to be 160mm. I was more than a little surprised to hold the wheel up and look at it, and sure enough, it's symmetrical and has a 160mm dropout spacing. I thought all CoMo tandems were built with 145 rear dropout spacing. What's the deal?

  2. #2
    hors category TandemGeek's Avatar
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    Quote Originally Posted by Carbonfiberboy View Post
    I downloaded the CK owners manual and pulled off the rear wheel. The CK manual said that my axle had to be 160mm. I was more than a little surprised to hold the wheel up and look at it, and sure enough, it's symmetrical and has a 160mm dropout spacing. I thought all CoMo tandems were built with 145 rear dropout spacing. What's the deal?
    Co-Motion specs all of their stock tandems with 145mm rear spacing; however, that's not to say someone didn't custom-spec a 160mm rear spaced model or -- heaven forbid -- cold set the frame to accommodate a 160mm rear hub.

    However, I guess I'd want to confirm that you have measured the drop-outs and aren't just assuming because the wheel is symetric that you have a 160mm rear hub / drop-outs. That's because Chris King's 145mm and 160mm rear-spaced hubs both build-up dishless, symetrical rear wheels: http://chrisking.com/hubs/hbs_tandem

  3. #3
    just another gosling Carbonfiberboy's Avatar
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    Quote Originally Posted by TandemGeek View Post
    Co-Motion specs all of their stock tandems with 145mm rear spacing; however, that's not to say someone didn't custom-spec a 160mm rear spaced model or -- heaven forbid -- cold set the frame to accommodate a 160mm rear hub.

    However, I guess I'd want to confirm that you have measured the drop-outs and aren't just assuming because the wheel is symetric that you have a 160mm rear hub / drop-outs. That's because Chris King's 145mm and 160mm rear-spaced hubs both build-up dishless, symetrical rear wheels: http://chrisking.com/hubs/hbs_tandem
    Ah, you got it. I was just so shocked to see the dishless wheel that I didn't measure it. Yup, 145mm. So are there any advantages to a 145mm dishless wheel build? Now I'm trying to figure out which CK hub I've got, because it does have a one-piece axle.

  4. #4
    hors category TandemGeek's Avatar
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    Quote Originally Posted by Carbonfiberboy View Post
    Ah, you got it. I was just so shocked to see the dishless wheel that I didn't measure it. Yup, 145mm. So are there any advantages to a 145mm dishless wheel build? Now I'm trying to figure out which CK hub I've got, because it does have a one-piece axle.
    In theory, a dishless wheel will be stronger and less prone to spoke breakage than an asymmetrical, dished wheel since the spokes on both sides of the wheel will have the same bracing angles and equal tension. In practice, the strongest wheels tend to be the ones that are simply built well using quality components.

    As for which hub, it can sometimes be a bit of a crap-shoot with the CK hubs. Your best bet is to look at both the Universal and ISO features and then compare them to what you're seeing on your hub. For example, the 135mm Chris King rear hub on our Ventana isn't what it's supposed to be so I had the same quandry when I first went to service the hub.

  5. #5
    just another gosling Carbonfiberboy's Avatar
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    The inside of the hub looked really good. Just needed a little clean and lube. However the outside of the hubshell (I think that's the correct terminology) was not so good. The cogset is a Shimano 11-34. The inner six cogs are on a carrier, but the outer three are separate. These outer three have dug into the hub splines a bit. The lock ring seems to have been installed with about the right torque. Never had the Shimano hub on my singles damaged like this. Though those are just singles, I'm fairly strong. Are the CK hubs softer? Is there a better cogset I should run?
    Last edited by Carbonfiberboy; 11-16-08 at 09:35 PM.

  6. #6
    hors category TandemGeek's Avatar
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    Quote Originally Posted by Carbonfiberboy View Post
    These outer three have dug into the hub splines a bit. Never had the Shimano hub on my singles damaged like this. Though those are just singles, I'm fairly strong. Are the CK hubs softer? Is there a better cogset I should run?
    The CK tandem hubs are supposed to have the stainless steel driveshell and, even then, you'll still sometimes find minor indentations in the splines. If the gouges are really bad you'll want to check and make sure the driveshell isn't aluminum; stranger things have happened.

    For reference purposes, I stepped out to the garage and took a photo of the stainless steel splines on our CK hub which, as you can see, have some minor indentations from the four smallest, individual sprockets. Now, keep in mind, these smaller cogs don't see nearly has much high-load use as they do on road tandems. Therefore, I also took a photo of the stainless steel splines on a Phil Wood hub that has about 15k miles of road use with similar XT cassettes (5 fixed / 4 loose or 4 fixed / 5 loose) to the ones used on the off-road tandem. As you can see, the indentations are a bit worse but still not that bad.

    Assuming it's just some minor gouging the best you can hope for are the LX and XT Shimano cassettes where the really high-torque-loaded larger rear sprockets are on the carrier.
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    Last edited by TandemGeek; 11-16-08 at 10:07 PM.

  7. #7
    just another gosling Carbonfiberboy's Avatar
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    Quote Originally Posted by TandemGeek View Post
    The CK tandem hubs are supposed to have the stainless steel driveshell and, even then, you'll still sometimes find minor indentations in the splines. If the gouges are really bad you'll want to check and make sure the driveshell isn't aluminum; stranger things have happened.

    For reference purposes, I stepped out to the garage and took a photo of the stainless steel splines on our CK hub which, as you can see, have some minor indentations from the four smallest, individual sprockets. Now, keep in mind, these smaller cogs don't see nearly has much high-load use as they do on road tandems. Therefore, I also took a photo of the stainless steel splines on a Phil Wood hub that has about 15k miles of road use with similar XT cassettes (5 fixed / 4 loose or 4 fixed / 5 loose) to the ones used on the off-road tandem. As you can see, the indentations are a bit worse but still not that bad.

    Assuming it's just some minor gouging the best you can hope for are the LX and XT Shimano cassettes where the really high-torque-loaded larger rear sprockets are on the carrier.
    Thanks so much! The new world of tandem maintenance. My gouges are quite a bit more substantial than yours, but still only about 1/32" deep at the most. I think it is an XT cassette. Perhaps some time in the past, the lock ring wasn't tightened enough. Everytime I have hub work done on one of my bikes, I check the lock ring with my torque wrench. It's almost never tightened to spec. I started doing that when my cassette came loose on a group ride. That's no fun!

    I do like the CK hubs. They are so smooth and beautifully made. I couldn't care less about the sound.

    While I'm yakking with you, I noticed that I need to replace my rear rim. I have 36H Aeroheads. I already replaced the front one. With the front rim, it looked like the previous owner had taken quite a hit, which had deformed the rim a bit, and then the pads had worn the deformed section (8" long?) until it had gotten quite thin, at which point it really started to deform from tire pressure.

    It looks like a similar thing is beginning to happen to the rear rim. There's an area on one side, maybe 6" long, that's definitely out of round - pushed in toward the hub by maybe 1/32" - and the shoes on that side are starting to wear it. We're a 300lb team. Do you think these rims are just not up to it, or can we put this down to damage from the previous owner? We've put about 1000 miles on the bike, almost all of it in dry conditions. I replaced the front rim after about 100 miles and we had definitely not taken any big hits. Now we've been over numerous RR tracks, etc, though no pinch flats or rim denting, at least of the sort that I'm used to seeing.

    We live in the PNW and it's totally normal for an Open Pro rim to wear through in one season. Thus I run ceramic rims on my rain bike. Thanks.

  8. #8
    hors category TandemGeek's Avatar
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    Quote Originally Posted by Carbonfiberboy View Post
    I have 36H Aeroheads. I already replaced the front one. We're a 300lb team. Do you think these rims are just not up to it, or can we put this down to damage from the previous owner?
    This is just my take, but the Velocity Aerohead would not be my first choice for an all-around tandem rim. They're probably OK for superlight teams, building up a set of very light wheels for the sake of building up a set of very light wheels, and casual / occasional use by lightweight teams but IMHO, that's about it and even then I'd want to build them up with high-flange hubs.

    The Velocity Fusion and rims of similiar proportions / design is probably the best all-around rim for a tandem that will be used for sport riding with 23mm - 28mm tires and it's no secret that I'm actually partial to the deeper section Velocity Deep-V type rims for my own road tandems: it's basically a belt and suspenders thing as the Deep-Vs build up to very robust wheels.

    For all-around use and touring the Velocity Dyad is a very good choice unless you plan to run tires that are less than 28mm wide. 25mm can be used, but tire shape begins to become less than ideal. However, for teams that run 28mm or larger tires, i.e., OEM rim spdc, larger teams, teams that will do loaded touring, etc... they're a great rim choice.

    So, back to your wheels, clearly any excessive rim wear or deformation came as a result of the previous team's use, be it due to their size or inability to avoid road hazards.

  9. #9
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    Chris King

    The gouging on your CK isn't that bad. I had a set of topolinos that were practically indexed. High torque and high weight are hell on softer metals.
    I got my new rear wheel and am thrilled with it's performance thus far. The belt and suspenders approach previously mentioned was my final decision. Chris King hub and a Velocity Deep V. I'm excited and hopefull that it won't be cursed like our DT/Hugi and Velocity Dyad wheel.

  10. #10
    hors category TandemGeek's Avatar
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    Quote Originally Posted by Murf524 View Post
    The gouging on your CK isn't that bad. I had a set of topolinos that were practically indexed. High torque and high weight are hell on softer metals.
    No, I agree: the CK hub is nearly pristine. Again, stainless steel and because the hub is used on our off-road tandem the smaller 4 sprockets see very little high-torque use as the chain stays in the middle of the cassette or on the taller sprockets most of the time.

    I'll be interested to see how the drive shells on our Topolino wheelset, as well as the ones on our Rolf's and our White Ind / Deep-V hubs hold up; at least the White Ind / Rolf's shell housings are titanium.
    Last edited by TandemGeek; 11-17-08 at 06:18 PM.

  11. #11
    just another gosling Carbonfiberboy's Avatar
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    Quote Originally Posted by TandemGeek View Post
    This is just my take, but the Velocity Aerohead would not be my first choice for an all-around tandem rim. They're probably OK for superlight teams, building up a set of very light wheels for the sake of building up a set of very light wheels, and casual / occasional use by lightweight teams but IMHO, that's about it and even then I'd want to build them up with high-flange hubs.

    The Velocity Fusion and rims of similiar proportions / design is probably the best all-around rim for a tandem that will be used for sport riding with 23mm - 28mm tires and it's no secret that I'm actually partial to the deeper section Velocity Deep-V type rims for my own road tandems: it's basically a belt and suspenders thing as the Deep-Vs build up to very robust wheels.

    For all-around use and touring the Velocity Dyad is a very good choice unless you plan to run tires that are less than 28mm wide. 25mm can be used, but tire shape begins to become less than ideal. However, for teams that run 28mm or larger tires, i.e., OEM rim spdc, larger teams, teams that will do loaded touring, etc... they're a great rim choice.

    So, back to your wheels, clearly any excessive rim wear or deformation came as a result of the previous team's use, be it due to their size or inability to avoid road hazards.
    We're running 23c Vredestein TriComps as I've seen suggested on this forum, extra good because that's the same tire I run on my singles so I only need to keep one kind of spare on hand. With a rear wheel/tire weight of almost 3.5 lbs, I don't see that the 45g difference between the Fusion and Deep-V makes much difference. One can save that much on tube weight! I'll order a Deep-V and a set of new spokes and nipples.

    Yeah sure, it had to be the previous team!

    Color is a problem. My current Aeroheads are black. The frame is blue and the TriComps also blue. Electric blue might look nice, but then I'd have two different rim colors for a couple of years!

  12. #12
    hors category TandemGeek's Avatar
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    Quote Originally Posted by Murf524 View Post
    I had a set of topolinos that were practically indexed. High torque and high weight are hell on softer metals.
    Sure enough.... Just pulled them out of the wheel bag, pulled off the cassette and checked.

    I had a Shimano Ultegra 12x27t 10 speed cassette on our Topolino's that have only the 3 top sprockets groupped together, with the 19t - 12t being loose. The 19t cassette embedded itself in the "forged, heat-treated and hard anodized 7075-T6 aluminum freehub body shell housing" and had to be knocked loose to free it and the 21-24-27t group of sprockets from the carrier. Moreover, there aren't a whole lot of miles on the hub with this cassette.... like under 300 miles.

    Most of the wear and tear was put on the Topolino's with the aforementioned XT 12x32t cassette with 5 fused sprockets and 4 loose ones or an Ultegra 9 speed 12x27t that has 3 + 2 sprocket groupings with 4 loose ones. Can't recall seeing any gouges after using the XT cassette for 1k miles or so, but do recall that the Ultegra 9 speed's 19/21 sprocket combo needed a tap to get off.

    Might have to rethink my cassette selections to make sure I'm using the ones that have the largest groupings of sprockets on carriers...
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    Last edited by TandemGeek; 11-17-08 at 06:35 PM.

  13. #13
    just another gosling Carbonfiberboy's Avatar
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    Quote Originally Posted by TandemGeek View Post
    <snip>
    Might have to rethink my cassette selections to make sure I'm using the ones that have the largest groupings of sprockets on carriers...
    And I'm rethinking my chainring choices under way. I'm used to a 12-25 cassette on my single, which gives me the 4 smallest cogs just one tooth apart, so I'm almost always in the middle ring. But with the 11-34 cassette on the CoMo with only the smallest three cogs separate, I'm going to try using the big ring more to keep the chain on the carrier cogs. Lowers chain tension, too.

    Stoker and I did our first pass climb today, wonderful to do in the middle of November in the PNW. Lovely weather and destroyed legs due to the hard single speed group ride on my single yesterday. A perfect combination. Stoker also tired but happy. Rear rim did OK. I'll have the Deep-V mounted by next weekend.

    When I lubed my Chris King rear hub, I didn't have any special $10 CK Ring Drive Grease, so I just used a few drops of Finish Line Cross Country Wet Lube, which is my winter chain lube. Works perfectly. Nice engagement and a slightly muted buzz.

  14. #14
    Terri's Captain RickinFl's Avatar
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    TandemGeek-

    Returning to a comment you made earlier in this thread about CK 145 dishless wheels being stronger-

    I haven't seen any of these, but I'm assuming that they make them dishless by moving the non-drive side spoke flange inboard to place it the same distance from the dropout as the flange on the drive side.

    If this is the case, it seems logical that the wheel would be less strong and less stiff because the aspect ratio of the isosceles triangle formed by the spokes with the spacing between the flanges as its base is reduced. This is the same problem I've heard of with 29" wheels where the triangle is made taller without proportionally increasing its base by moving the flanges apart, thereby decreasing the aspect ratio. This is done, presumably, so that manufacturers can continue to use standard hubs, axles and so forth. In some circles, it's well known that it's easier to taco a 29" wheel than a 26" wheel due to this effect. Because of that, I always find myself wondering why folks are so excited about putting 29" wheels on off-road tandems when the possible side loads on the front wheel are even greater than on a single. But that's a side issue since my question really involve dishless rear wheels.

    So- how are the CK rear hub made dishless?

    Rick

  15. #15
    hors category TandemGeek's Avatar
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    Returning to a comment you made earlier in this thread about CK 145 dishless wheels being stronger-

    Sort of... I hedged a bit and actually wrote: "In theory, a dishless wheel will be stronger and less prone to spoke breakage than an asymmetrical, dished wheel since the spokes on both sides of the wheel will have the same bracing angles and equal tension. In practice, the strongest wheels tend to be the ones that are simply built well using quality components."

    I hedge because aside from our first tandem -- the '96 Santana Arriva -- none of our tandems have had symmetric rear wheels, although some come pretty close. The mountain tandems have used 135mm and 140mm rear hubs that had very shallow bracing angles and lots of dishing. The Ericksons and the Calfee have had 145mm rear spacing with a variety of different degrees of dish, dependent on the hubs.


    I haven't seen any of these, but I'm assuming that they make them dishless by moving the non-drive side spoke flange inboard to place it the same distance from the dropout as the flange on the drive side.

    Yes and, actually, Chris King cheats a bit with their marketing: If you check their specs you can see they're so close that they look asymmetical but really aren't. They use their ISO hub which has a flange-to-flange width of 55mm and offset the hub 29/26 for the 145mm tandem hub.

    Now, 29mm doesn't look all that great but White Industry's rear tandem hubs are pretty darn close: The 145mm MI6 rear disc tandem hub uses the same 53.5mm flange width MI6 disc hub found on their 135mm mountain bike hubs and off-sets the flanges 30/23.5. The 145mm Daisy tandem hub with left side threading has a 55.5mm flange width and uses a 30/25.5 off-set.

    Phil Wood's 145mm tandem hub has a 57mm flange width and they use a 32/25 off-set, which is probably more in keeping with traditional whel building and looks to be the widest hub of the bunch. However, and interestingly enough, our Topolino's have nearly a 60mm flange-to-flange width and are pretty close to being symmetrical, but not quite and use 18 drive-side spokes with only 12 non-drive side. The Rolf's, on the other hand, are the most narrow of the bunch with at best maybe 48mm between the flanges and single-bike-like off-set.

    Then there are of course the 160mm symmetric wheels and, well, despite having gobs of off-set still break spokes about as often as their 145mm counterparts.

    So, as I said, I hedge my bet on tandem wheel building theory because it's tempered by what I've seen and experienced in practice... and in practice any of these different hubs can be used to build up some really nice wheels where stability and durability are influenced more by the build than anything else, at least for teams of average size and weight.
    Last edited by TandemGeek; 11-17-08 at 08:56 PM.

  16. #16
    Terri's Captain RickinFl's Avatar
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    I seem to recall that the rational for the 160mm spacing was that you could build a dishless wheel that had, more or less, the same flange spacing as a dished 145mm wheel. No stronger laterally than a 145, just less prone to spoke breakage. The 160 design does leave a lot of unsupported axle length hanging out compared to a dished 145 or even 140 (which I still use). It wouldn't surprise me to hear that they break fewer spokes but more axles.

    I do agree that dishless wheels are less prone to spoke breakage if correctly built.

    Rick

  17. #17
    hors category TandemGeek's Avatar
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    Quote Originally Posted by RickinFl View Post
    I seem to recall that the rational for the 160mm spacing was that you could build a dishless wheel that had, more or less, the same flange spacing as a dished 145mm wheel.
    From a posting by Bill to Hobbes back in 1994, this was Bill's first mention of 160mm rear spacing on the list:

    WHY DID SANTANA CHOOSE 160mm?

    DISHED vs. DISHLESS. Maybe some engineer out there can determine the exact
    percentage difference, but in our experience dishless wheels (where all the
    spokes have the same load) are nearly twice as durable as standard dished
    wheels (where half the spokes carry a majority of the load).

    WIDE BRACING ANGLES. Further, if the hub is dishless, moving the flanges
    further apart provides an improved bracing angle (the primary reason 26"
    wheels are stronger than otherwise identical 700c wheels).

    MORE COGS. Back in the mid-70s, when over 99% of all "ten speeds" featured
    5-speed freewheels and 120mm spacing, Santana asked Phil Wood to produce
    symmetric (dishless) hubs with a wider space between the flanges. These hubs,
    the first built with 140mm spacing, became standard equipment on Santana's
    original tandems-and other tandem builders soon followed Santana's lead. A
    few years later, when the first tandem-strength 6-speed freewheels became
    available (also at Santana's request), we moved the hub flanges closer
    together. The resulting 6-speed wheels were weaker, yet still adequate. A few
    years after that, 7-speed freewheels became available and, to obtain the
    necessary additional clearance, we filed away part of the right chainstay and
    re-introduced a "smidgen" of dish. The resulting 7-speed wheels (and the
    frame), were weaker, but still adequate for most riders.

    In the meantime, single bike spacing evolved from 120mm to 126mm to 130mm to
    135mm.

    Three years ago customers started requesting eight cogs. And while it is not
    impossible to shoehorn an extra cog into a 140mm tandem frame, the resulting
    dished wheels will be considerably weaker (no matter who builds the hubs or
    how many spokes are used).

    Why 160? We could have made an incremental change to 150mm, but 160mm is the
    minimum spacing that gets us back to our original uncompromised design;
    completely dishless wheels, increased bracing angles, and unimpaired
    chainstays. Within two or three years a majority of tandems will be built to
    our new standard-it's the best way to combine reliability with today's
    8-speed cogsets.

    --------------

    For those who would like to read more about the origin, rationale, and expections for 160mm rear hubs, this is a link to a 1996 post by Bill where he gets into all of the details some 2 years after the first posting in '94: http://search.bikelist.org/getmsg.as....9604.0451.eml

  18. #18
    Senior Member zonatandem's Avatar
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    On Velocity Aerohead wheels:
    Just replaced rear rim (36H) after wobberknocking it severely on some road debris after 23,000+ miles of riding.
    Front wheel, 32H: have broken 2 alloy spoke nipples (NOT spokes). One at around 19,000 and the next +/- 20,000 miles. The 2nd broken nipple was after hitting a chunk of steel at an intersection we were hustling through in Utah.
    We are a light team (just under 250 total).

  19. #19
    just another gosling Carbonfiberboy's Avatar
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    Quote Originally Posted by zonatandem View Post
    On Velocity Aerohead wheels:
    Just replaced rear rim (36H) after wobberknocking it severely on some road debris after 23,000+ miles of riding.
    Front wheel, 32H: have broken 2 alloy spoke nipples (NOT spokes). One at around 19,000 and the next +/- 20,000 miles. The 2nd broken nipple was after hitting a chunk of steel at an intersection we were hustling through in Utah.
    We are a light team (just under 250 total).
    Our new Aerohead front rim is doing just fine. Maybe we'll stay with that and go with a Deep-V in back. My understanding is that the front wheel stresses on a tandem are not much greater than those on a single. The captain is 160 of our 300. My guess is that your stoker might be a little lighter.

  20. #20
    Senior Member WebsterBikeMan's Avatar
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    Quote Originally Posted by Carbonfiberboy View Post
    My understanding is that the front wheel stresses on a tandem are not much greater than those on a single.
    Not my understanding. On a single, the rider's weight is substantially biased toward the rear. Possibly as much as 80/20. Will depend on riding stance, bike geometry, etc. On a tandem, the captain's weight is mostly on the front wheel, while the stoker's is mostly on the rear wheel. So the weight on the front wheel can easily be a multiple of what it would be on a single.

    Not only that, but you can't unload the wheel when you see a bump.

  21. #21
    hors category TandemGeek's Avatar
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    Quote Originally Posted by Carbonfiberboy View Post
    My understanding is that the front wheel stresses on a tandem are not much greater than those on a single.
    Quote Originally Posted by WebsterBikeMan View Post
    Not my understanding. On a tandem, the captain's weight is mostly on the front wheel, while the stoker's is mostly on the rear wheel. So the weight on the front wheel can easily be a multiple of what it would be on a single.
    Gotta go with Webster on this one.... It's not my understanding either.

    It's pretty much a function of the total weight distributed over the wheels where you can assume somewhere between 40% and 50% of the tandem's total weight is sitting on the front wheel, depending on the weight differential between captain and stoker. A physics teacher and tandem enthusiast actually did some farm boy analysis of this and posted it to hobbes eons ago: http://search.bikelist.org/getmsg.as....9405.0176.eml

    In short, Ed found the captain's weight was split about 64/36 front to rear and the stoker's weight was split about 26/74 front to rear... and, well, you can do the math for a notional team of 300 lbs where the captain is 160 lbs and a 40 lb tandem where the weight is split 45/55 front to rear.

    160 lb captain = 102.4 lbs front & 57.6 lbs rear
    140 lb stoker = 36.4 lbs front & 103.6 lbs rear
    40 lb tandem = 18 lbs front & 22 lbs rear
    340 lb loaded tandem = 156.8 lbs front & 183.2 lbs rear

    Now, compare that to your notional single bike where the bike weighs 20 lbs and the loaded bike has a weight distribution of about 40/60 front to rear:

    180 lb loaded single bike = 72 lbs front & 108 lbs rear.

    Others have done the same types of comparisons and found similar weight distributions on loaded tandems, e.g., 40/60 - 45/55 and even 50/50 when the captain is twice the size of the stoker, so I don't have a problem with Ed's model.

    Just some food for thought.... Hey, 36h single bike wheels aren't that different than 36h tandem wheels and will do fine in a pinch for average size tandem teams. However, you really start eating up the safety margin that's inherent in all bicycle wheels when you start playing around with the superlight or reduced spoke count single bike wheels given how much loading they must deal with when used on a tandem, particularly when it comes to cornering and stopping.

    Again, the ability of a standard 32h or 36h bicycle wheel to hold up under the added stress and strain of a tandem is pretty amazing and stands as a testament to the strength of the basic bicycle wheel design, and hopefully this little exercise had demonstrated just how much added stress and strain we're talking about for a tandem.
    Last edited by TandemGeek; 11-19-08 at 08:03 AM.

  22. #22
    just another gosling Carbonfiberboy's Avatar
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    Quote Originally Posted by TandemGeek View Post
    <snip>
    In short, Ed found the captain's weight was split about 64/36 front to rear and the stoker's weight was split about 26/74 front to rear... and, well, you can do the math for a notional team of 300 lbs where the captain is 160 lbs and a 40 lb tandem where the weight is split 45/55 front to rear.

    160 lb captain = 102.4 lbs front & 57.6 lbs rear
    140 lb stoker = 36.4 lbs front & 103.6 lbs rear
    40 lb tandem = 18 lbs front & 22 lbs rear
    340 lb loaded tandem = 156.8 lbs front & 183.2 lbs rear

    Now, compare that to your notional single bike where the bike weighs 20 lbs and the loaded bike has a weight distribution of about 40/60 front to rear:

    180 lb loaded single bike = 72 lbs front & 108 lbs rear.
    <snip>
    Again, the ability of a standard 32h or 36h bicycle wheel to hold up under the added stress and strain of a tandem is pretty amazing and stands as a testament to the strength of the basic bicycle wheel design, and hopefully this little exercise had demonstrated just how much added stress and strain we're talking about for a tandem.
    That post of Ed's is very interesting, particularly in view of what I said about the front wheel, vs. the reality that the front wheel has the biggest difference on a tandem.

    On the subject of tension, Ed thought we should go to 48 spokes to keep the load similar to that of a single. However most folks build their rear wheels with spoke tensions of 110 kgf, so 3.8 lbs. rear spoke load from weight is only 2% of the unloaded tension. Of course this is an oversimplification, because the spokes carry the load very unequally. Still, 10% of static tension is probably in the ballpark. Perhaps we should double that to allow for accelerations on bumps. So 20%.

    I believe the purpose of the 110 kgf preload is to stretch the spoke so that it stays loaded throughout the rotation, and is also the reason that double butted spokes are less likely to fail than spokes which are not necked down in the center. Be all that as it may, in 1000 miles I've now replaced two tandem rims but have not had a broken spoke. 36H rims. In fact, I've never broken a spoke, though I'm just starting out with only maybe 50,000 miles of modern biking. OTOH, I tension my own wheels, but I suppose so do most participants here.

    But this brings up another interesting point. I've been told when building rear wheels to install the "pulling" spokes so they come out of the outside of the flange. But if one has disk brakes, especially on a tandem, should one reverse that, since braking forces will be much greater than drive forces?

    And one more question about tandem wheels. I have friends with a new (to them) tandem. They are so fast that they can drop all but the strongest singles on the climbs. But he won't come out on it in the wet because he's afraid of wearing his rims. Thus his stoker misses our wet rides, which is really too bad since she's up for it. So he's a little OCD. Big deal.

    The solution would be to run Open Pro Ceramic rims like the rest of us in the PNW who got tired of replacing rims every year on our singles. Except they're about the same 300 lb. team weight as we are and we seem to have messed up at least one of our 425g Aerohead rims. Open Pros weigh about the same. Except that with a ceramic, there's no rim wear, so the wall thickness will always be the same. Both our Aeroheads had slightly dished brake tracks when they began to fail. Neither of our Aeroheads had any tendency to come out of true. What do you think?

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    hors category TandemGeek's Avatar
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    On the subject of tension, Ed thought we should go to 48 spokes to keep the load similar to that of a single.

    Yes and no; Ed was kind of thinking out loud after seeing the weight distribution for the first time. Later in the same thread he ponders the basic question: just how overbuilt are regular bicycle wheels? This gets back to the basic premise that you can probably find well-spec'd and well-built 36h wheels that are stronger than 48h wheels using a box rim, a low flange, 3x vs. 4x or 5x lacing, and that simply weren't built as well. Note: If you click on the subject line when you're in the Hobbes archives all of the other posts from that thread (or posts with the same words) will pop-up. Again, it was an interesting thread and there are hundreds of other insightful, thoughtful and very technical posts buried in the Hobbes archives... unfortunately, most of the really great contributors have moved on. But I digress....

    I've been told when building rear wheels to install the "pulling" spokes so they come out of the outside of the flange. But if one has disk brakes, especially on a tandem, should one reverse that, since braking forces will be much greater than drive forces?

    I wouldn't, not on a rear wheel. After all, the biggest limitation on just how much force that rear brake is going to exert on the rear wheel is limited by the same thing a rim brake is: the rear tire's grip. In regard to the latter, I'm sure you've discovered that grip ain't all that great once you apply the front brake with any real force. Front disc brake equipped wheels are a bit different in that a disc brake can generate higher torsion loads at the hub than a rim brake so the argument to build a front wheel with more attention to the direction and orientation of the "pulling spokes" has some merit.

    But he won't come out on it in the wet because he's afraid of wearing his rims. The solution would be to run Open Pro Ceramic rims like the rest of us in the PNW who got tired of replacing rims every year on our singles. What do you think?

    You know, there was a time when the Velocity Aerohead was only 19mm tall and weighed an astounding 405 grams. I believe the current extrusion yields a 21mm tall rim that weighs 425 grams. The Mavic Open Pro is only 18.3mm tall and a tad more narrow than the Aerohead but weighs 435 grams, most likely due to the use of eyelets whereas the Velocity rims are all just drilled. Frankly, I'd be hard pressed to make a case that an Open Pro CD was any less durable than an Aerohead all other things being equal. Anyway, I thought I'd throw that out there for anyone following this thread to chew on once again noting I still maintain it's a small and select group of tandem teams that will be better served by the very lightweight single-bike rims on a tandem. However, for those who can... what ever works best for you IS what's best for you.

    Anyway, if I was looking to extend the life of my rims in a harsh world like the PNW I'd first look to a rear disc and make a point of over-using it for most routine braking to scrub off speed short of actual stops or any panic braking since it takes like 5 minutes to replace a set of pads, they're a lot cheaper than rims, and -- well -- they actually work pretty darn well even on a rear wheel. In fact, I'd almost forgotten just how dramatic the difference in braking power is compared to even a dual-pivot rear caliper now that I've got the disc on our Calfee for the winter.

    I'd also consider going with a rim that doesn't have a machined side wall, like a Velocity Fusion. I've never seen any added value to a rim with machined side walls for consumers who aren't fitting these rims to race bikes anyway... and in a harsh environment like the PWN you'll have the equivalent of machined side walls in a few months. All machining side walls does for you and me is artificially lower the weight of a rim while cutting its useful service life by 1/3 or 1/2. Rivendell has some words about this on their Website as well: http://www.rivbike.com/article/components/rims

    Anyway, if we lived and rode in the PNW I'd probably follow my own advise and have a set of non-machined Velocity Fusion rims laced up to a set of (pick your favorite hubs) and rear disc + mud guards on our Calfee if we were inclined to ride when it was wet. In fact, right now our Calfee's actually sporting both the disc and full SKS mud guards. The mud guards will likely come off once I'm satisfied they'll work without rubbing or rattling but will be put right back on when it looks like rain will coincide with a ride: tain't nothing better than full-coverage mud guards. The disc will also come off in the spring when the Topolino's and Rolf's go back on.
    Last edited by TandemGeek; 11-19-08 at 08:24 PM.

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    just another gosling Carbonfiberboy's Avatar
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    Quote Originally Posted by TandemGeek View Post
    <snip>
    Anyway, if I was looking to extend the life of my rims in a harsh world like the PNW I'd first look to a rear disc and make a point of over-using it for most routine braking to scrub off speed short of actual stops or any panic braking since it takes like 5 minutes to replace a set of pads, they're a lot cheaper than rims, and -- well -- they actually work pretty darn well even on a rear wheel. In fact, I'd almost forgotten just how dramatic the difference in braking power is compared to even a dual-pivot rear caliper now that I've got the disc on our Calfee for the winter.

    I'd also consider going with a rim that doesn't have a machined side wall, like a Velocity Fusion. I've never seen any added value to a rim with machined side walls for consumers who aren't fitting these rims to race bikes anyway... and in a harsh environment like the PWN you'll have the equivalent of machined side walls in a few months. All machining side walls does for you and me is artificially lower the weight of a rim while cutting its useful service life by 1/3 or 1/2. Rivendell has some words about this on their Website as well: http://www.rivbike.com/article/components/rims

    Anyway, if we lived and rode in the PNW I'd probably follow my own advise and have a set of non-machined Velocity Fusion rims laced up to a set of (pick your favorite hubs) and rear disc + mud guards on our Calfee if we were inclined to ride when it was wet. In fact, right now our Calfee's actually sporting both the disc and full SKS mud guards. The mud guards will likely come off once I'm satisfied they'll work without rubbing or rattling but will be put right back on when it looks like rain will coincide with a ride: tain't nothing better than full-coverage mud guards. The disc will also come off in the spring when the Topolino's and Rolf's go back on.
    Well, I'm gettin' my wheel larnin' done. The first set of rain rims I laced up were MA2's because they weren't machined and had a lot of metal in 'em. Lasted 2 seasons on my rain single. Mavic doesn't make them anymore. I use the ceramics now on my rain single. For a year I just had a ceramic rear, so I did like you say and only put on the rear unless I had to use the front.

    I stoked for a local racer-boy on his Cannondale with rear disc. I was impressed with the stopping power.

    My friend's 7-speed Davidson of course has no provision for a disc. I think the braze-on on my Speedster chainstay is for a drum rather than a disc. I also don't know how to tell if my CK rear hub is disc ready. The CK website says the new tandem rears are for disc, but mine is several years old. Oh well.

    Open Pro CD is not the same as the Ceramic. Built wheels with ceramic rims don't seem to exist. Have to lace your own or buy custom. Open Pros are the only ceramic rims I know of. Have to trade pads with the wheels, because ceramic pads will go through an aluminum track pretty quickly. But they are perfect. Like perfect. No "scrub" time when wet and they don't wear.

    I'll have to see if I can find salmon Kool Stop pads for my V-brakes. That'll help, I think. I just put a set of Dura-Ace pads on my single with Rolf Vectors and I'm taking them right back off. I can hear the metal going away, even in the dry. I'd rather pull a little harder and keep those legacy Rolfs going.

  25. #25
    hors category TandemGeek's Avatar
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    My friend's 7-speed Davidson of course has no provision for a disc. I think the braze-on on my Speedster chainstay is for a drum rather than a disc.

    Back to plan B: rims with meaty brake tracks or running that ceramic rim up front instead of the Aerohead... for anyone who might otherwise be inclined to run the Aerohead (not me and we only weigh 280lbs). However, back to your Speedster, if all you have is a "pac-man" (backwards C shaped tab) on the underside of your left chainstay and no I.S. disc tab sitting on the upper back half of the rear drop-out and seat stay then yes, you're frame is not disc compatible.

    I also don't know how to tell if my CK rear hub is disc ready. The CK website says the new tandem rears are for disc, but mine is several years old. Oh well.

    I'm pretty sure all of the 145mm CK tandem hubs are disc brake compatible; they're just not drum brake compatible. The left-side of the hub should look pretty much like this one... and you just bolt-on the correct disc rotor adapter:





    Open Pro CD is not the same as the Ceramic.

    Yeah, but you mean what I know.... I've lost track of all the acronyms that MAVIC uses; heck, MAVIC's even an acronym: Manufacture d'Articles Vélocopediques Idoux et Chanel

    Open Pros are the only ceramic rims I know of.

    There have been / are some other MAVIC rims that have the ceramic coating (X517, XC717) and a few other rim/wheel makers use it, e.g., Zipp.
    Last edited by TandemGeek; 11-20-08 at 07:54 AM.

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