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  1. #1
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    Tire size vs Weight vs Speed

    Hi from Montreal,
    We are still riding our single bikes on trainer as winter here is far from being over. We should pull out the tandem probably around mid-april. We bought the tandem late last summer so we only rode it 6-7 times. We still have things to learn but I can say that both my wife and I are really pleased with the tandem. Hopefully this year we will have more time for tandem rides.

    I got few questions regarding tires size for tandem. But first some data. I am weighting 165 lbs, my wife 125 lbs, the bike 38 lbs and with water bottles, some tools and a lunch, the total weight is propably close to 340 lbs. Right now the tandem is rolling on specialized armadillo 700 x 28 tire inflated at 125 psi. With those tire, the flat spot look to be around 5/8-3/4 of an inch. Because of that, I am a bit affraid of snake bite. I don't have much experience with tandem so I don't know if this size/kind of tire is appropriate for us. Is it worthed to go with a larger tire. How speed is going to be affected with a larger one. May be another type of 28 will be better? I am a bit confuse, tires are not cheap and last thing I want is to have a collection of tandem tires in my garage.

    One more thing I have observed is our speed. I was in the impression that tandem were much faster than single road bike. Well it is faster but not what I expected. May be because my wife and I are not yet fully synchrone. I don't know, but downhill speed are just a bit faster than a single. Could it be the rolling resistance of the armadillo??? If you have some comments on all this it will be well appreciated.

    Thank you to all for your help. Have a nice day.

    Michel

  2. #2
    Senior Member Retro Grouch's Avatar
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    Quote Originally Posted by onroule
    Hi from Montreal,
    We are still riding our single bikes on trainer as winter here is far from being over. We should pull out the tandem probably around mid-april. We bought the tandem late last summer so we only rode it 6-7 times. We still have things to learn but I can say that both my wife and I are really pleased with the tandem. Hopefully this year we will have more time for tandem rides.

    I got few questions regarding tires size for tandem. But first some data. I am weighting 165 lbs, my wife 125 lbs, the bike 38 lbs and with water bottles, some tools and a lunch, the total weight is propably close to 340 lbs. Right now the tandem is rolling on specialized armadillo 700 x 28 tire inflated at 125 psi. With those tire, the flat spot look to be around 5/8-3/4 of an inch. Because of that, I am a bit affraid of snake bite. I don't have much experience with tandem so I don't know if this size/kind of tire is appropriate for us. Is it worthed to go with a larger tire. How speed is going to be affected with a larger one. May be another type of 28 will be better? I am a bit confuse, tires are not cheap and last thing I want is to have a collection of tandem tires in my garage.

    One more thing I have observed is our speed. I was in the impression that tandem were much faster than single road bike. Well it is faster but not what I expected. May be because my wife and I are not yet fully synchrone. I don't know, but downhill speed are just a bit faster than a single. Could it be the rolling resistance of the armadillo??? If you have some comments on all this it will be well appreciated.

    Thank you to all for your help. Have a nice day.

    Michel
    First, I don't think you have any worries about impact flats. My wife and I use 700x25c Armadillos on our tandem at 110psi. We don't have any problems and we weigh more than you do.

    Second, Armadillos are great for flat resistance - they are nearly bullet proof- but they are NOT high performance tires. If your goal is to go fast, I'd recommend something with a more supple sidewall.

    Third, to go faster you need to get your wife to pedal harder. If you figure out how to do that, please share it with the rest of us.

  3. #3
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    My team is much more gravity enhanced than you. We've used 700x23's at 130 psi and had no problems w/pinches. The tire wear was the factor that caused us to move up to x25's. We now use Hutchinson distance tires 700x25c at 125 psi.
    It goes without saying that the smaller you go the more "captaining" you have to do to keep your team out of road hazzards.

  4. #4
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    Quote Originally Posted by onroule
    Hi from Montreal,


    One more thing I have observed is our speed. I was in the impression that tandem were much faster than single road bike. Well it is faster but not what I expected. May be because my wife and I are not yet fully synchrone. I don't know, but downhill speed are just a bit faster than a single. Could it be the rolling resistance of the armadillo??? If you have some comments on all this it will be well appreciated.

    Michel
    Can't advise you on the tyre front as I am offroad with Knobblies on 26". One point I have noticed though, is that Off road, we can achieve higher speeds when Gravity takes over, than on road. I.E. Offroad downhills, where we just let the bike go, and hold on, we can achieve 40/45 mph without really trying. On road the highest speed we have ever got up to is 41mph. and that was on a long steep hill, and really going for it and on slicks, On Solo Mountain bikes, with Knobblies we can get 37mph on the same hill.
    The only thing I can put it down to is the quality of tyre, or rubber. Investigate the tyres as one way to increase speed.

    On the riding front, I wonder why it is always the stoker that gets the blame? I am the weak one on our team, and am the stoker. I have just mentioned the one thing that will definitely make the tandem go faster, and that is "team" It takes time for the two of you to start to work together, but when it comes in, boy will you be shifting. Probably not uphills, as that is still hard work for most tandems, Downhill may be faster, if you manage to sort the tyres, but the big increase in speed will be on the bits in between. Even off road we find that we lose the faster solos, and that is when they are flat out, and we are cruising. This took around 400 miles to aquire, over the space of about 3 months, but when it comes in you will notice the difference

    By the way, our overral weight is around 420lbs, so do not worry too much about your overral weight. Weight is not as critical on a tandem as much on a solo, unless you carry too much in your panniers, too much surplus weight on the body,or stop for too many Cake stops en route.

  5. #5
    Senior Member zonatandem's Avatar
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    tandem tires

    Howdy from Tucson!
    The narrower the tire and higher the pressure rating on a tire the easier it will roll; however, it will not be quite as cushy a ride as on wider tires.
    Speed will come with practice and teamwork. We've hit 53 mph (coasting) in the White Mountains of Arizona under ideal conditions: good road/weather, little traffic and a heck of a downhill at 7,000 ft. elevation! Tuck in and coast on downhills and watch your speed pick up!
    Just put a few thousand miles on Maxxis Detonnator tires, 120 lbs pressure and excellent tire wear, Ran 23mm front, 25mm rear. Do inflate your tires to the listed max pressure! Your weight should not be an issue!
    Laissez les bon temps rouler! Bon chance Michel!

  6. #6
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    Bonjour Michel,

    Rendus à 700x28, je pense que le choix des pneus est plutôt une question de confort qu'une question de résistance aux crevaisons.

    *****

    With the weight you have, the 700x28 could probably be ridden at 100 psi without fearing snake bites. After all, the weight you have on each tire is not much more than what a typical 200-225 lb guy would have on his rear wheel. Only you have that weight on both wheels.

    So it's then a question of comfort. I don't know where you are in Montréal, but I ride a lot near home, that is around the mountain, downtown, Mile End, Saint-Henri, Westmount and the like, and I feel I need 700x37 at 75-80 psi to make the bumps and potholes comfortable. it's less of a problem outside the city, but then I carry more stuff.

    I am new to tandeming on a bona fide tandem, as we got our Co-Motion on December 6th 2003. We did a tryout that day in Mississauga and then travelled a few kilometres tonight, with oldest daughter (7) on the back seat and youngest one (4) on the trailercycle. Let's say I want more practice before riding on ice!

    The previous years, however, we have been riding a lot on a single bike + trailercycle + child trailer: maybe 2000-2500 km with the whole contraption, and another 1500 km (including an 11-day tour) with only single bike + trailercycle, so I am used to company...

    Regards
    Michel Gagnon
    Montréal (Québec, Canada)

  7. #7
    hors category TandemGeek's Avatar
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    Quote Originally Posted by onroule
    Right now the tandem is rolling on specialized armadillo 700 x 28 tire inflated at 125 psi. With those tire, the flat spot look to be around 5/8-3/4 of an inch. Because of that, I am a bit affraid of snake bite. I don't have much experience with tandem so I don't know if this size/kind of tire is appropriate for us. Is it worthed to go with a larger tire. How speed is going to be affected with a larger one. May be another type of 28 will be better? I am a bit confuse, tires are not cheap and last thing I want is to have a collection of tandem tires in my garage.
    Tire pressure in general: Sidewall numbers are nice, but don't always yield the right answer for how much air pressure to use for a personal bike, let alone a tandem. Therefore, I think you're on the right track in looking at the shape and contact patch with respect to determining if your tires are properly inflated. As for how to determine if you have the right amount of air pressure in your tires, the general rule of thumb for any road bicycle -- tandems included -- is that there should be a very slight bulge in the tires when everyone's on-board the bike.

    Over Inflation: If there is no bulge when rider weight is put on the bike, the tire(s) is/are over-inflated. With an over-inflated tire you'll end up with a harsh ride, are more likely to get a puncture from road debris than you would on a properly inflated tire, and may actually end up with more rolling resistance than a properly inflated tire if your roads aren't relatively smooth, e.g., chip seal / oiled gravel versus smooth asphalt.

    Under Inflation: If the tire has a pronounced bulge, the tire(s) is/are under-inflated. An under inflated tire might make for a more "cushy" ride but tends to make for poor road feel, poor handling, higher rolling resistance, and will be susceptible to pinch flats.

    You can read more about tire inflation in general at Sheldon Brown's web site: http://www.sheldonbrown.com/tires.html#pressure

    With respect to tire sizes and tandems, you can use just about any size tire on a tandem so long as you adjust the psi to manage the weight. Performance oriented riders will normally opt for smaller diameter tires that mimic the road feel of their racing bikes whereas touring and recreational riders will most likely want larger diameter tires for greater comfort. As for speed performance, as already noted, if you have very smooth asphalt road surfaces, running higher psi numbers on any tire will tend to lower your rolling resistance and it's possible to get good performance out of a larger diameter / high volume tire. Just use the tire's shape to establish the proper inflation levels vs. just the psi recommendation on the sidewall, even if that means using a higher psi number than a tire is labeled for, e.g., if it says 110psi you may find you need to use 125psi to get the proper shape -- remembering that the rating was created for the "average" cyclist (i.e., one person) using the tire on a personal bike.

    If you can achieve the slight bulge with a 700x28 or larger diameter tire at 10 psi below the recommended max pressure for the tire on your tandems rear tire, then that's the right tire pressure. If you can't, put in more air until you get the right shape. Take your cues for front tire pressure from the rear tire.

    As for us, we are about your same team weight and distribution and have never used anything larger than a 700x25 high performance training/ racing tire on our tandems because I like our tandems to handle just like my personal road bikes which are all racing bikes. However, we're also blessed with very smooth roads here in the Southeast US which is what allows us to use the narrow tires without much of a penalty in terms of confort for most of the places we ride. We pay dearly for our rock-hard racing tires when we encounter "shake and bake" chip sealed roads, but that's the exception and not the rule. We also see reduced tire life -- perhaps getting between 2k - 2.5k at best if I run them on the front for the first 1k - 1.5k miles before condeming them to the rear -- compared to the harder tread compounds used on a tire like the Armadillo or a Panaracer Pasela. Then of course there are the economics that go along with go-fast tires since they tend to cost more and wear out their softer tread compounds must faster than touring tires, never mind being more susceptible to casing damage that can require premature replacement (superglue works wonders for closing minor tread cuts). But, at least for now, that's what 'works for us'. I like the quality of the ride we get with our tires and just accept the downsides of higher cost and reduced wear as "the cost of doing business". Who knows, we may one day end up on larger volume tires... either because we move to a place where chip-sealed roads are the norm or a colder climate where expansion joints or cracked and patched road surfaces are a fact of life.

    Ultimately, the best thing you can do is to try and hook-up with tandem riders in your local area or region who are of similar size and who ride the way you ride, to find out what types of tires they have used and their impressions. Tire suitability is not universal.

    Finally, as for not ending up with a bunch of tires laying around from testing, if you have 700x23 or 700x25 tires on your personal bike and your tandems rims aren't super-wide, you could certainly do some experimentation and fit them to your tandem for a ride. In fact, that was the first thing I did after we took our first tandem out for its maiden ride on home turf. In fact, we may have even had the same 700x28 Armadillos on our '96 Santana and I was very unhappy with how they made the bike feel and handle. When we returned from the first ride I took the 700x23 / 145psi Vredestein Fortezzas off of my personal bike and rode with those the next day and it literally transformed the tandem's handling. We have ridden the 23's almost exclusively ever since, only adopting the 25s now that we find ourselves traveling to places where the roads aren't as smooth as what we're accustomed to here at home. Again, if you do experiment be sure to run enough air pressure to compensate for your higher team weight to prevent a pinch flat.

    One more thing I have observed is our speed. I was in the impression that tandem were much faster than single road bike. Well it is faster but not what I expected. May be because my wife and I are not yet fully synchrone. I don't know, but downhill speed are just a bit faster than a single. Could it be the rolling resistance of the armadillo?
    How are you measuring / quantifying the difference in speed? Are you riding with a regular group and finding that you aren't decending faster or is it based on a cyclo-computer readout? If it's the cyclo-computer, have you recalibrated it for the size of the tires on the tandem?

    For downhill speeds, and with all other things being equal, you can pretty much use a mathematical formula to determine just how much faster a tandem with an additional 140lbs of rolling weight (125lb stoker + 15lbs of added bike weight) should descend a given grade vs a lone rider on a bike. A larger, underinflated tire on your tandem would certainly create a lot more drag than a more narrow, possibly overinflated tire on your personal bike so, yes, your tires could be robing you of some velocity. Same thing goes for riding on flat and smooth roads, just run the numbers on increased power output without increased wind resistance and you'll see that a tandem team where both riders are of average ability and fitness should carry more speed than an average, lone cyclist. I did find that when we first started riding the tandem I was faster on my personal bike, both climbing and on the flats. Over time, as we became more efficient as a team and as Debbie's cycling fitness improved (Noting that she was in good physical shape but she was not a cyclist when we started riding the tandem), our overall performance exceeded what I could achieve on my personal bike on all but the most hilly rides. Speaking of climbing, all bets are off. Most tandem teams can't climb at 100% efficiency. That said, there are a lot of strong tandem teams that can easily out climb a lot of riders on personal bikes which surprises most of the folks who get passed, but it takes a lot of teamwork to get to parity on hill climbs with your regular, go-fast single bike riding partners.
    Last edited by livngood; 02-21-04 at 02:20 AM.

  8. #8
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    Good info about tire inflation for tandems:
    http://www.precisiontandems.com/arttiresbymark.htm

  9. #9
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    Thank you to all for your help. I will try to answer all questions that my original post has opened.

    For Michel; I am living in the north of Montreal. I mostly ride in Laval or up north (Laurentian). I try to choose my course for the best asphalt but....because of our winter (you know about it too) there is nothing perfect around here. We have to be carefull. Specially early in the season.

    On our single, both my wife and I are riding on Vredestein Fortezza 700 X 23 inflated at 90 psi for my wife and around 100 psi for me. We have found that higher pressure do not reduce rolling resistance and also at higher pressure bikes have a tendency to bounce to much. That make them scary at high speed like going done long hill with sharp curve when the road is not very good. At too high pressure, the front tire don't stay in contact with the ground and the direction of the bike become erratic. We realy like those Fortezza. One set has over 8000 km (5000 milles) and the other around 4000km. Of course I would like to get the same feeling on the tandem that I have on my single.

    The Armadillo 700 X 28 were recommended to us by the LBS. Since we were new to tandem I took is advice. After few rides, I was not so sure if those tires where the best for us. But the season was almost over so I did not bother. Now, we are back training and I would like to fix this before the beginning of the season. I have 2 set of wheels for the tandem. One is build on a wide Mavic rim. Minimum size tire that could go on those rim is 28 mm. It is the one with the armadillo tire. The other one is built with Ambrosio balance narrow rim and can be fit with anything from 19 to 25 mm. I would like to give a try with the Fortezza but I am a bit concerned to have a 23 mm install on the back wheel and riding around here. I don't think there is a 25 in the Fortezza serie. What would be your recommendation for a performant 25 mm? The way is going we will probably end up with a set of "performance" wheels and a set of "Touring" wheels

    As for speed measurement goes, we use a speedometer. It is calibrated for the right size of tire. Because we are training basically on the same course with the singles or with the tandem. With time I can see that both the average and the top speed are just a bit higher with the tandem compare to me on my single. One thing I forgot to say: When we stop pedaling, the tandem is slowing down much faster than a single. And no, it is not brake rubbing or tight bearing. It is rolling resistance. On the other end, all this is not only a question of speed. On very long ride, any percentage of the available power spend on rolling resistance is a pure loss of energy. Why spend it if it could be use the right way!!! Thank you Mark to indirectly remember me the site www.analyticcycling.com. I am going to figure out how much more speed I could expect from the tandem in a perfect world.

    Thanks also for the advises about tandem training. Right now Maryse is working on her RPM. I am usally spinnig around 95 rpm and she is more around 85. Last summer we kind of compromise around 90 rpm but with her training it will be easier for her next summer. I also understand it will take some time for us to synchronize our power stroke, specially for climbing. We should be fix (hopefully) with that at the beginning of the summer.

    Again, thanks to all of you for your recommendation. If you could guide me on a nice 25 mm tire I am ready to give it a try.

    Bonne journée à tous, (Have a nice day)
    Michel

  10. #10
    hors category TandemGeek's Avatar
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    Quote Originally Posted by onroule
    I don't think there is a 25 in the Fortezza serie. What would be your recommendation for a performant 25 mm?
    The Fortezza "did" come in 700x25 as we've been using them for about 4 years; however, they were a special order item. I no longer see them listed on their Web site so perhaps they've been dropped (drats).

    Nonetheless, there must still be some inventory floating around out there as a few Etailers are still listing the 700x25's, some with only the black/tan models but at a great price and others with listing the black/black models at an obscenely high $44.

    http://www.bicycletires.com/tek9.asp...oducts&grp=188
    http://www.biketiresdirect.com/vredestein.htm

    Another 25mm tire to consider would be the Avoct Fasgrip K20 Carbons; almost everyone we ride with runs this particular tire and we have used them a few times with good results. I suspect that's what we'll begin to run when we need a 25mm tire once the last of my '25mm Fortezza's are used up.

    The Continental Gatorskins come in a 700x25 and are purportedly a descent tire; I've never used it so can't comment based on personal experience.
    Last edited by livngood; 02-21-04 at 02:10 PM.

  11. #11
    Cat 6 Steve Katzman's Avatar
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    What a difference tires make

    We just changed tires this past weekend from the 700x28 Continental Gatorskins that came on the tandem to 700x25 Vredstein Fortezzas. This took a while since the Velocity Dyad rims that come with the bike are not recommended for tires narrower than 28 mm. So we got new wheels with narrower rims and mounted the Vreds. We pumped the tires to 120 psi - same as we had been with the Gatorskins. Big difference!!! The tires are much more resilient and it feels like they permit the bike to roll with less resistance. The Gatorskins felt dead by comparison. This is obviously all subjective since I don't have any way of making objective measurements. We rode a flat ride of 47 miles on Sunday and our average was a full 1 mph faster than any other ride we have ever done. Was it all due to the tires? I can't say for sure but it sure seemed like most of it was. From word of mouth info that I have heard from friends, the Armadillo tires are even deader feeling and roll slower than the Gatorskins. I'd bet that you would be able to tell a big difference between them and a tire like the Fortezza. By the way the combined weight of our team is a little under 325 lbs, not including the bike.

    As far as your question about tandems being faster than single bikes, I'd say that they coast down hills faster than a single but on flat ground it is a different story. I would say that the average speed for a given ride will be the average of the average speeds of the captain and the stoker + maybe a .5 mph bonus because the stoker always in the draft. So if my average speed for a given ride is 20 mph and my stoker's average speed is 14 mph for the same ride, chances are our combined speed on the tandem will be about 17 mph + the .5 mph drafting bonus, giving us a combined average of 17.5 mph. Again this is not mathematically derived - just my observations. So for me tandem riding is considerably slower than riding a single, while for my stoker it's considerably faster. If you happen to have a captain and stoker that both average 20 mph on single bikes then they would probably have a combined average of ~20.5, so it would be a bit faster for them.

    Steve

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    Thank you Mark and Steve for your comments on different tires. Too bad Vredestein is getting rid of the 25 mm. Look likes it is a good performer for tandem. May be they are not aware of that.

    If others have comments on 25 mm tires please go on. Also may be somebody know if TPI is an important factor in tire specification??

    Thanks,
    Michel

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