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  1. #1
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    Broken spoke AC 420

    Just an FYI for any AC 420 wheel users. We were on the fast group ride this morning, on point 31 mph and "PING", broken rear spoke.

    Luckily, the wheel did not implode. There was a group of about forty riders behind us.

    We are a 260 lb team. I bought the wheels used on e bay. So I don't know how many miles were already on them. They were perfectly true when I got them. We rode them for just over 2k miles on the tandem. These AC 420 wheels will now be relegated to a single bike use only.


    Time for new wheels.

  2. #2
    Senior Member Homeyba's Avatar
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    That can happen to any wheel. It all depends on who and how it was built. I wouldn't throw the baby out with the bathwater here, find a competent wheel builder and have them rebuild it properly. Truing a wheel is only part of the process. More importantly, wheels have to be tensioned properly. I've had 36 spoke wheels brake on me because they weren't built properly. On a tandem, properly built wheels are more important than on the single because of the additional weight and torque you are putting on them
    It doesn't get harder, you just go slower.

  3. #3
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    Quote Originally Posted by Homeyba View Post
    That can happen to any wheel.
    I second this. A spoke breaking doesn't mean much other than that spoke needs to be replaced, and the wheel trued and checked for tension. But if that wheel continues to eat spokes, I might limit it to the half-bikes.

  4. #4
    Senior Member waynesulak's Avatar
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    Was this a 130mm rear wheel on a tandem?

    Wayne

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    If you send an email to AC, they do not "Recommend" the AC 420 for use on a tandem. I sent a note and asked them. Not many wheel builders have wheels that are specifically designed for tandems. I would say there is a good reason for that.

  6. #6
    PMK
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    Heck with send an email to AC, take a day to ride, go visit AC, have them fix it, then go ride. Call first to make sure they will fix it while you wait. Good way to see if their good customer service rep is true.

    They are near Tampa I thought, find some place new to ride and make a day of it.

    PK
    2006 Co-Motion Roadster, flat bars, discs and carbon fibre fork, size 22 / 19
    2006 Ventana ECDM full suspension mountain tandem
    Some single bikes and a couple of KTM's
    And most important, someone special that enjoys them with me (except the KTM's)

  7. #7
    Senior Member diabloridr's Avatar
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    Quote Originally Posted by swamptandem View Post
    Time for new wheels.
    Given the unknown number of miles of these wheels, I'd consider looking into whether AC will rebuild the wheels with all new spokes.

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    Senior Member JTGraphics's Avatar
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    So you were running AC 420's on a tandem and a 260lb team? thats some task for those wheels.
    I have a set and even at 165lbs when I used them I fiund them to be a little flexy.
    I have rebuilt the rear with some DT Swiss Comps and the seemed a little better but no longer use them since I have other wheelsets that get used on my bikes now.
    But they were great wheels on my single light and fast, best on a bike with a 160lb rider I fill.
    It may not be fancy but it gets me were I need to go.
    http://www.jtgraphics.net/cyclist_bicycles.htm

  9. #9
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    Quote Originally Posted by diabloridr View Post
    Given the unknown number of miles of these wheels, I'd consider looking into whether AC will rebuild the wheels with all new spokes.
    I would believe that if he contacts AC and tells them they were being used on a tandem they will tell him they were being used in a wrong application.

  10. #10
    Senior Member diabloridr's Avatar
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    Quote Originally Posted by DubT View Post
    I would believe that if he contacts AC and tells them they were being used on a tandem they will tell him they were being used in a wrong application.
    Who said anything about telling them that?

    Just tell 'em you bought on eBay, have busted a spoke, and are interested in a complete rebuild.

  11. #11
    Senior Member JTGraphics's Avatar
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    F.Y.I.
    I rebuilt my wheels all you need are the correct spoke lengths.
    AC 420 using Bladed or Round Spokes with AC nipples (Note using other nipples subtract 2mm from length.)
    Front 18H 273 273
    Rear 24H 273 273
    It may not be fancy but it gets me were I need to go.
    http://www.jtgraphics.net/cyclist_bicycles.htm

  12. #12
    Tandem Vincitur Ritterview's Avatar
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    The AC 420 has been touted as a "a nice compromise for light weight, stiffness, strength, and durability."

    It appears the AC 420 isn't particularly stiff, strong or durable, but they are lightweight.

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    What about this from "sixtiescycles" in a previous thread.
    http://www.bikeforums.net/showthread...=#post12328670

  14. #14
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    Are your wheels built with bladed or round spokes?
    no signature

  15. #15
    Senior Member waynesulak's Avatar
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    Quote Originally Posted by Dean V View Post
    What about this from "sixtiescycles" in a previous thread.
    http://www.bikeforums.net/showthread...=#post12328670
    Sixtiescycles says:
    "In answer to your question, though, I'll start by reiterating that we have a couple dozen Paketa tandems on the road with American Classic 420 wheels on them going back six years now, and so far haven't had a single failure. Not one broken spoke, a nipple pulling through the rim, or a bearing or axle failure. Knock on wood."

    It appears that sixitiecycles sells Paketas with AC 420 wheels. While it may be true that he has not heard of a single spoke break or other failure mentioned. I am not sure what that really tells us. I know that I would not complain to the shop or CoMotion or Santana if my five year old bike broke a spoke or had a rim failure. Certainly not on a full on race bike like a Paketa with light wheels. Not having heard of a problem does not mean no problem existed.

    AC420s may be great wheels. I certainly don't know. We have one failure on wheels with an unknown history. Anyone else on the list have a lot of tandem miles on them? If so what is your team weight?

    Everybody want faster wheels. Are these a good tandem alternative?

    Wayne, who has learned "don't strand the stoker on the side of the road" comes right after "the stoker is always right"

  16. #16
    Senior Member diabloridr's Avatar
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    Quote Originally Posted by waynesulak View Post
    Wayne, who has learned "don't strand the stoker on the side of the road" comes right after "the stoker is always right"
    I'm less worried about being stranded on the side of the road than I am about a wheel comng unglued at 40+ MPH.

    That's why a high-performance tandem-rated wheel is a far as we're willing to push the envelope, but to each his own.

  17. #17
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    Quote Originally Posted by diabloridr View Post
    I'm less worried about being stranded on the side of the road than I am about a wheel comng unglued at 40+ MPH.

    That's why a high-performance tandem-rated wheel is a far as we're willing to push the envelope, but to each his own.
    Has anyone ever had a catastophic wheel failure with a spoked wheel? We have broken a number of spokes over the years but never something that would make a wheel collapse or stop rotating to cause a crash.

  18. #18
    Senior Member diabloridr's Avatar
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    Quote Originally Posted by Dean V View Post
    Has anyone ever had a catastophic wheel failure with a spoked wheel? We have broken a number of spokes over the years but never something that would make a wheel collapse or stop rotating to cause a crash.
    Got close once: Had a front hub flange start to crack on the Rolfs. I caught it before it completely came apart. If that had happened we would have lost 2 out of 10 spokes providing support in one direction.

    At a minimum, the bike would have been unrideable, at worst the wheel would have locked up at a bad time.

    The newer Rolf hubs have much beefier flanges

  19. #19
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    Quote Originally Posted by waynesulak View Post
    Was this a 130mm rear wheel on a tandem?

    Wayne
    Our bike is 130mm spacing.

    I know breaking a spoke is not out of the ordinary. However, I'm not willing to take any chances on the tandem. If the spoke broke while in a hard turn, the wheel could fail.

    I will have the wheel repaired by Chris at Maggie Rose's bike shop here in Jacksonville. He's a competent wheel builder. The wheel will only be used for the single bike from here on out.

    I'll have to find a new set of climbing wheels, or have Chris build us some. We're going with the HED H3 for the flat speedy rides around here. No spoke issues to worry about. Plus, they look really cool!

  20. #20
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    Quote Originally Posted by swamptandem View Post
    Our bike is 130mm spacing.

    I know breaking a spoke is not out of the ordinary. However, I'm not willing to take any chances on the tandem. If the spoke broke while in a hard turn, the wheel could fail.

    I will have the wheel repaired by Chris at Maggie Rose's bike shop here in Jacksonville. He's a competent wheel builder. The wheel will only be used for the single bike from here on out.

    I'll have to find a new set of climbing wheels, or have Chris build us some. We're going with the HED H3 for the flat speedy rides around here. No spoke issues to worry about. Plus, they look really cool!
    The HED H3 is also not rated for Tandem use. I have a set on my road bike and would love to use them on the tandem but have not.

  21. #21
    Senior Member Homeyba's Avatar
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    I've used the Hed H3's on my tandem. They work great for slower speeds but not so well at high speed. They were just too stiff and actually upset the handling of the tandem at high speeds (really bad in fast corners). If your frame has more flex than my Calfee that might not be a problem for you. They do make that cool "wooping" sound though.
    It doesn't get harder, you just go slower.

  22. #22
    Senior Member diabloridr's Avatar
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    Quote Originally Posted by DubT View Post
    The HED H3 is also not rated for Tandem use. I have a set on my road bike and would love to use them on the tandem but have not.
    My observation is the HED H3/Specialized Trispoke have been widely used as an "event wheel" for time trialing with tandems. We certainly saw enough of them when we attended Masters Natz many years ago.

    Don't take that as an endorsement to use them as your "daily driver" wheels, however.

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    Hi,

    I have some older AC 420's (second generation I think) and would never attempt to put them on the tandem.

    Your team is really light on the scale but 260 is still quite a bit for those tiny hubs and light rims.

    There a nice smooth single wheel.

    rob

  24. #24
    Tandem Vincitur Ritterview's Avatar
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    Since my carbon rimmed wheels have been reliable for over a year now, I was thinking that a deep carbon rim may be the answer to the problem this thread highlights, of gaining wheel strength without making the wheels too heavy. But since my experience is anecdotal, I thought I would run this idea by Jason Wozniak at Fairwheel bikes. He built my wheels, and had recommended a deep rim for strength. He also was quite worried about braking heat, and was barely mollified by my insistence I would heat up the disc, not the rims. Jason's knowledge of these parts is encyclopedic. He is the author of the definitive Fairwheel hub review, a perusal of which should convince that Jason knows whereof he speaks.

    I told Jason about the AC420 here, related that I have had a good experience with my ENVE wheels, and asked if he would recommend carbon clincher wheels as an everyday substitute for lightweight, but failure prone tandem wheels such as the Bontrager, Rolf, etc.

    His response:


    Quote Originally Posted by Jason
    Hi Ritterview,

    Sorry about the delay, things are really crazy getting ready for Interbike.

    Iíd not use the AC420 on a tandem ever. 34mm deep and less than 18mm wide. 130 spacing means still a difference in tension ratios (with a wider spacing this can be evened more.)

    If the hub were 145 you could build a wheel with less dish and therefore more even spoke tension. More even spoke tension means less likely to see a spoke failure.

    I think 145 is better for tandems, but it doesnít mean you have to go crazy. I think something like a Kinlin XR380 rim with a 32 spoke, 145 spaced Chris King hub would be sufficient for most pairs, though I wouldnít say all. Iíve done some pretty light tandem wheels, the lightest being a King 145 on Enve 45 tubulars with 28 DB spokes in the rear. This is for a pair weighing about 280 pounds. But again these I wouldnít recommend for most people.

    I also wouldnít feel comfortable recommending your wheels [ENVE carbon clinchers] to others. Itís not necessarily a strength issue that I have with them so much as a braking issue. I still really think carbon clinchers with rim brakes is not a good thing on a single bike, but can be really dangerous on a tandem. The King/Enve 45 set we built was tubular rather than clincher and used disc brakes rather than rim brakes.

    There are lots of things you could do for wheels, but really I think it comes down to two camps.

    Group one uses stock wheels and really doesnít have a lot of choices as stock wheels have to be over built for most riders so that they work for everyone. These are going to be heavy wheels.

    The other group is the custom group and there is nothing that Iíd recommend other than talking to a well informed builder. There are a ton of options in bike wheels and even more for tandems. Everything from brakes, to course, to riding style, weight, and hub spacing matters. Then of course thereís spokes, spoke count, rim depth, bracing angle, axle diameter, bearing sizes, and still more. The lightest stock tandem wheelset that I know of is the Topolino Ax3.0 at 1520 grams. Rim brake, 145mm spacing. Not sure Iíd call it a wheel for everyone, but it seems at least decently well thought out.

    So for your direct questions.

    Q: Given the positive experience I have had with the ENVE 65 mm carbon clinchers, and leaving aside the brake heat issue, would you recommend these as an everyday do-all wheel as an alternative to lightweight tandem wheels such as the Rolf? What hub would you recommend the 100 mm front, and for 130 mm, 135 mm and 145 mm? Is 145 mm too wide for a 65 mm carbon rim?

    1. No I wouldnít recommend 65 Enve clinchers as an everyday alternative to Rolfs. The main reason is the brake heat which I canít ignore. But ignoring that Iíd still say no because of the cost to replace when you pothole them. Road hazards are far harder to avoid on a tandem than a single and with the extra weight you are far more likely to destroy them on a train track, pothole etc... Iím not saying they wonít work, but for most of my customers, Iím going to recommend an alloy rim.

    2. For the front Iíd probably look at something like the Chris King Classic. I think bracing angle is good on the Alchemy, but not a main consideration on tandem. Higher spoke count is better and with the small flanges and high bracing angle of the Alchemy there may be flange failure issues after time.

    3. For rear 130 mm hubs, Iím probably again going to look at Chris King, with a steel freehub body. Again flange spacing is that big of a deal with high spoke counts and also introduces more difference in tension ratios.

    4. For rear 135, again the king. As would probably be for 145 as well.

    5. A 145 may not necessarily be too wide for a 65. It isnít necessarily wider flange spacing than a 130, it just has to do with the hub design and how the get to 145. Often the flange spacing is the same but axle ends are changed which moves the hub further center and evens tension without changing bracing angle.



    Cheers

    Jason Woznick
    Fair Wheel Bikes
    1110 E. 6th St
    Tucson, Az. 85719

    520-624-3045
    fairwheelbikes.com
    __________________

  25. #25
    Senior Member waynesulak's Avatar
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    Some good points were made above. I have been thinking about single bike wheels on a tandem:

    Different teams have their own goals and expectations. Race wheels really only need to last the distance of the race and highly competitive athletes are willing to take risks for the rewards of their best possible performance. We all make this type of choice every time we set up for a fast corner. How much risk are we willing to take vs our required margin of error. Selecting a critical component like wheels or a fork forces us to choose. Light weight vs margin of error. Speed vs reliability.

    With that in mind I have been thinking about light weight wheels, their stated weight limits and using them on a tandem. Consider wheels that have a stated 180 weight limit. Designers usually build in a safety margin in any load bearing component and for this purpose i assume it is 100% of the 180 limit. On the other hand when I am asked my or my team's weight I answer the undressed weight. After all that is what I weigh - but I ride wearing shoes, a helmet, jersey and bib shorts. I assume no follow car so 1 tube, a CO2 cartridge and a small bag are included. Water is a heavy load and one full bottle weighs 1.7 pounds. Two bottles are included even though in 100+ heat that would make for a short ride. With these assumptions I made the following calculations:

    thinking.pdf


    The attachment shows that with my assumptions using those wheels are within the assumed design however the saftey margin is drastically reduced from 77% TO 19% . Of course my assumptions could be way off but this is just an illustration. Not considered are some great points mode by others including the inability of a tandem to avoid pot holes and other road hazards. Also to consider is the effect of inertia in braking and cornering a tandem.

    For us I want a greater margin of safety than single wheels provide however if I were riding a flat 20 mile time trial on a good road and we were highly motivated I can see taking the risk to buy just a little more speed. The questions are: what is your risk tolerance and at what price speed?

    Wayne

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