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Tandem Cycling A bicycle built for two. Want to find out more about this wonderful world of tandems? Check out this forum to talk with other tandem enthusiasts. Captains and stokers welcome!

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Old 05-23-10, 11:30 PM   #1
lhbernhardt
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Why I don't use Contis

Well, it happened again, another Conti sidewall failure. I noticed a small bulge on the side of the Ultra Gatorskin after 4,523 km. There's a cut in the sidewall and the tube is just starting to press its way out. Fortunately I spotted this in time, especially since it's on the front wheel of the tandem. The tire has been in use since late 2008 and regularly pumped to 120 lbs. It is a 700x23, 230 gram clincher, and team weight is 320 lbs. It was replaced with what I think is the best 23mm performance tire you can get today, the 220-gram Vredestein Fortezza TriComp.

Anyway, every Conti I've ever owned that hasn't died of a cut tread has died of a sidewall failure (sometimes catastrophically!). I had heard lots of good things about the Gatorskin on this board so I thought I would give it a try. I must say I am quite disappointed, it's just like any other tire Conti makes; they still haven't gotten the sidewalls right, and I'm even a big fan of German products. So much for Conti. Here's the photo:


Luis
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Old 05-24-10, 06:44 AM   #2
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Good luck with the Vredestein Fortezza TriComps. I gave up on them after I couldn't get more than 1000 miles on them. (They do have great customer service and replaced the ones that had manufacturing defects.) I would think that 4500km on any tire is pretty spectacular.
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Old 05-24-10, 07:53 AM   #3
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Been on Conti 4-seasons for years and never had that happen and I can get 3K on the rear and I've only ever had 1 flat.
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Old 05-24-10, 07:56 AM   #4
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Agreed 2800+ miles on a bicycle tire is pretty good, I would suspect that there was some cord showing on the tread or else all those miles where on some super smooth surfaces. We are very happy to get 2500 miles (4000 km) on a tire!
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Old 05-24-10, 07:58 AM   #5
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Sure hate to see tire issues like that from any brand/model tire particularly on a tandem. FWIW we have run Conti Grand Prix 4 Season tires for tens of thounsands of miles with absolutely no such issues. We are a 305 pound team on 28c's. The rear tread life is usually 1500 or less but no side wall issues to date. You are a much braver soul than I am because I can't bring myself to go down to 25's much less all the way down to 23's, particularly at our weight and road conditions.. Hope you find some combination that takes the worry out of your situation.

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Old 05-24-10, 08:04 AM   #6
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Do you leave the bike sitting on the tires all winter? That could do that in a couple of years, on a very thin sidewall racing type tire.
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Old 05-24-10, 08:05 AM   #7
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I was about to say what bill said why be on 23's at that weight?

25's will ride smoother more comfortable with a very insignificant weight addition, just as fast or faster then 23's too.

Chad
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Old 05-24-10, 08:23 AM   #8
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Quote:
Originally Posted by lhbernhardt View Post
I noticed a small bulge on the side of the Ultra Gatorskin after 4,523 km. There's a cut in the sidewall and the tube is just starting to press its way out. Fortunately I spotted this in time, especially since it's on the front wheel of the tandem. The tire has been in use since late 2008 and regularly pumped to 120 lbs.
Sounds like it died of natural causes, i.e., symptoms associated with the natural aging process... to include becoming more succeptible to cuts and nicks as the tire materials become less pliable.

This is the primary reason that when a rear tire wears out on our tandems, typically the front tire goes on the rear and the new tire goes on the front. Rear tires get chewed up where we live in 1,000 - 1,500 miles given that we spend 1/2 our time climbing grades between 2% and 12%, and the other half of the time going downhill... with very little flat and level terrain in between. So, it's not at all unusual to go through 3 - 4 tires a season, which means the tires are typically pretty fresh all the time... with the front tire being the newest.

In fact, with as many miles as you've put on the tire, I'd say it looks pretty darn good for it's age.
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Old 05-24-10, 08:30 AM   #9
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We had a virtually brand new 28mm Conti GP 4 Seasons fail along the same chord line as in the OP's picture. Walked out to the bike after getting some coffee and the tire was flat to the rim, but fine moments prior. Still using the tires, however. We probably get 1500 miles on the rear tire as well. I'm thinking of trying Schwalbe's (Marathon Racers or Marathon Supremes) in a large size just for comparison. We're a 350 lb. team.
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Old 05-24-10, 09:37 AM   #10
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I have used Gatorskins in the past and did notice some sidewall disintegration over time.
The GP4000(s) doesn't seem to be as bad and so far no sidewall problems.
Tons of riders use these on their single bikes.
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Old 05-24-10, 12:22 PM   #11
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A 320 lb team riding > 2800 miles on 700 x 23 tires I would say is a pretty good endorsement.

If you find some tires that do better than that, let us know.
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Old 05-24-10, 01:02 PM   #12
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Or dangerous!
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Old 05-24-10, 01:04 PM   #13
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Quote:
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I was about to say what bill said why be on 23's at that weight?

25's will ride smoother more comfortable with a very insignificant weight addition, just as fast or faster then 23's too.

Chad
You mean if I go from 23's to 28's that's even faster?
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Old 05-24-10, 01:42 PM   #14
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Or dangerous!
Really?
  • How long have you been riding tandems?
  • What type of tandem(s) do you ride?
  • What problems have you had with tires on your tandems that lead you to that conclusion?

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Old 05-24-10, 01:48 PM   #15
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Really?
  • How long have you been riding tandems?
  • What type of tandem(s) do you ride?
  • What problems have you had with tires on your tandems that lead you to that conclusion?
Just threw that out there. Don't get a saddle up your a$$.
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Old 05-24-10, 01:49 PM   #16
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You've done well to get that many miles out of a tire. I'm betting you had to replace the rear sooner, and as TG said, at that point the front should have been rotated to the rear and the new tire put up front.

I'm a pretty big fan of the gatorskins for both my tandem and single bikes, but I always make sure I have the newest tire up front because they are prone to side-wall failure as pictured when they start getting a lot of miles on them.
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Old 05-24-10, 02:32 PM   #17
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are there tandem-specific tires out there? i planned on using those exact tires, except in 25 or 28 size.

2 years old and 4.5km seems like a good run before tossing, especially on a rear on a tandem, but don't quote me on that since what the heck do i know!?!?

by the way, i'd be happy with that mileage on my single bike, where i do run those exact tires in a 23. i get about 1.5k miles +/- before something happens or they get too smooth for comfort (after which, in the latter case, they become indoor trainer duty tires).
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Old 05-24-10, 03:55 PM   #18
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are there tandem-specific tires out there?
Not really. There have been "trekking" tires that have been marketed for tandems in much the same way as certain rims are, but that's about it.

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2 years old and 4.5km seems like a good run before tossing, especially on a rear on a tandem
It was a front tire, not a rear: "Fortunately I spotted this in time, especially since it's on the front wheel of the tandem."

Tires for tandems have the same constraints that all other tires do: long-tire life = stiffer/heavier/less grippy tread. Higher performance = shorter tread life and increased susceptibility to punctures or cuts. Best bet is always to search out other riders in your local area or region with similar riding habits / weight to see what works best in terms of brand / model / size. What may be a great tire on the smooth, asphalt roads of Georgia is often times awful in places like Texas with it's Texas-size chip-seal or anywhere in the rust belt where roads are filled with expansion joints or cracked asphalt due to the weather-related wear and tear.
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Old 05-24-10, 08:06 PM   #19
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I was about to say what bill said why be on 23's at that weight?

25's will ride smoother more comfortable with a very insignificant weight addition, just as fast or faster then 23's too.

Chad
Maybe. You've got 2 factors to consider, rolling resistence and aerodynamics. There's a an argument back and forth about rolling resistence, with the data being at best inconclusive.

With regard to areodyanmics, though, its pretty clear that the wider tire is going to have more wind resistence, potentially substantially so, depending on the width of the rim. We time trial on 23 mm tires based on data from Zipp that it saves 7 watts per wheel versus 25mm with our wheels.

Other than TT situation we'll ride 25mm for more comfort, flat protection, and more confidence cornering. But for a TT 14 watts is a pretty big deal.
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Old 05-24-10, 11:00 PM   #20
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Thanks for the responses; you people are a fabulous fount of knowledge. The advice to go to a 25mm tire is starting to roll around in the back of my mind. I'm strictly a 23mm kind of guy (lots of racing experience, so I've got deep prejudices!), but I remember when we used to use 19 and 20mm tires, and we pinch-punctured regularly, or lost control on fast, tight turns, or felt the rim bottom out on tight turns (that's scary!) and when we switched to 23mm it was a revelation. But now, when you consider the added weight of a tandem on basically the same tire footprint, I start to see where it might make sense to increase the air chamber slightly to accommodate the additional weight. Anyway, you've got me thinking again, even after nearly 40 years of cycling experience!

Luis
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Old 05-25-10, 12:26 AM   #21
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Thanks for the responses; you people are a fabulous fount of knowledge. The advice to go to a 25mm tire is starting to roll around in the back of my mind. I'm strictly a 23mm kind of guy (lots of racing experience, so I've got deep prejudices!), but I remember when we used to use 19 and 20mm tires, and we pinch-punctured regularly, or lost control on fast, tight turns, or felt the rim bottom out on tight turns (that's scary!) and when we switched to 23mm it was a revelation. But now, when you consider the added weight of a tandem on basically the same tire footprint, I start to see where it might make sense to increase the air chamber slightly to accommodate the additional weight. Anyway, you've got me thinking again, even after nearly 40 years of cycling experience!

Luis
at least you are willing to try new things! I bet you'll love them let us know what you decide. I'm a bigger guy and was recommended to move to them when riders noticed how low my back tire would look @ 105-110 psi moved to the 25's and its literally a world of difference in how the bike feels, I weigh in at 205 and 6'5.

Chad
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Old 05-25-10, 09:53 AM   #22
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I have found (by accident) that 23 on the front and 25 on rear works well for us, but our combined weight is around 250lbs.
There is more weight and stress on the rear tire. I find the 23 feels more nimble and easier to steer than a 25.
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Old 05-25-10, 11:10 PM   #23
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I have been watching this thread wondering if someone was going to mention a problem we seem to have with the Conti 4 season with Vectran belt 700/28's. They dont seem to run round, I thought it was just in my head but this past weekend the stoker mentioned she noticed it also. I have noticed this on the back tire only on 3 seperate tires. I examined the tire and found no damage to sidewall or tread and the tire pattern is still visible (it has not "squared" off). My crude measuremnts show that it is out of round by about 25/1000 of an inch does not sound like much but you can see it and feel it.

I have been happy with the feel and flat resistance of the tire but I think I am about ready to try a new tire.
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Old 05-26-10, 08:09 AM   #24
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I wonder if this out-of-round condition isn't the wheel. Could some minor variance in spoke tension when the tire is fully inflated cause this to happen? I would try rotating the tire on the rim 90 degrees and see if the high/low spot moves with the tire or stays with the wheel position.
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Old 05-26-10, 01:46 PM   #25
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Some tires are made with the belt casing off center a little. It does happen.
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