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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 12-25-07, 08:48 AM   #1
dvs cycles
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Lighter tires: What a difference!

My Santana came with wire bead 28c Gatorskins and after just over 2200 miles the rear looked worn enough to replace. Put on GP-4000's in 25c and took off over 100grams per tire. Gatorskins were bombproof but these have better ride, rollout. Even my wife noticed and she usually has no feel for changes.
I know these won't last as long and will be more flat prone but I think it's worth it, especially with the smooth usually clean roads here in SoCal.
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Old 12-25-07, 11:21 AM   #2
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Suspect a degree of placebo effect here , as lighter tires will mostly mean you accelerate
a little faster which would translate into cerca 0.2% increase in accel for a 300# team.
I can recall a similar exhiliration when I switched my wheels in the '70s from 360 gram
rims with 350gram tubulars to 290gram rims with 250gram tubulars for racing. Nowadays
I don't feel a huge difference riding the 29# uber tandem compared with the 45# predecessor.
We definitely go up hills faster, accelerate noticeably faster but steady state speeds are
"about the same", rats!! It still doesn't allow us to keep up with 350watt singletons who
are 20yrs (or sometimes less) younger than we are on hills.

A difficult to evaluate, and more important factor is rolling resistance, which
can be fairly significant, but IIRC the Gatorskins were not slouches in this
area and were within 10% of the lowest RR rated tires and noticeably better
than others by 20%. If you want another potential wow tire, try some
Michelin Pro2 racers in 25mm next set. That is what came on our uber
tandem and they are quite nice. Be aware they measure out at 27.8mm.

Last edited by sch; 12-25-07 at 11:28 AM.
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Old 12-25-07, 11:24 AM   #3
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Where do I get more of this PLACEBO you mention?
Got any hookups?
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Old 12-25-07, 12:56 PM   #4
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I'd say that going from 28's to 25's made more of the difference that you feel than changing between tire models.

In my experience, 28's cannot be pumped up tight enough to give really precise handling, and whenever I have used them, they always feel squashy and sloppy to me. I pretty much always use Continental 700x25's because they seem to be the only ones you can find that are rated for 120psi (regardless of the model).

I'm using Gatorskins now in 700x25, and IMO, they have a lively and precise feel.

Rick
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Old 12-25-07, 02:29 PM   #5
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I'd say that going from 28's to 25's made more of the difference that you feel than changing between tire models.

In my experience, 28's cannot be pumped up tight enough to give really precise handling, and whenever I have used them, they always feel squashy and sloppy to me. I pretty much always use Continental 700x25's because they seem to be the only ones you can find that are rated for 120psi (regardless of the model).

I'm using Gatorskins now in 700x25, and IMO, they have a lively and precise feel.

Rick
Any online sources for folding Gatorskins in 25 you want to share? I thought that if the GP-4000's were to prove too fragile I would try some smaller Gatorskins.
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Old 12-25-07, 02:36 PM   #6
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Fortezza 25c has a lovely ride.
http://biketiresdirect.com/productde...=ci_VRFOR&tn=0
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Old 12-25-07, 02:37 PM   #7
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Any online sources for folding Gatorskins in 25 you want to share? I thought that if the GP-4000's were to prove too fragile I would try some smaller Gatorskins.
BikeTiresDirect.com has the the Ultra Gatorskins in 700x25mm for $26.95. They have a clone site called Western Bikes.com or something like that where you'll find similar pricing. I've used BTD as the source for our Vredestein tires for several seasons now and with a few exceptions, BTD seems to offer very competitive pricing all the time. No affliliation other than being a pretty happy customer.

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Fortezza 25c has a lovely ride.
We've used the Vredestein Fortezza's in 700x23 and 25 on our tandems exclusively since '97: great tires for our local conditions / riding style / team weight. I just ordered 4 of the 700x25 in tan sidewall and 4 in the black sidewall to cover a few of the bikes and tandems for the '08 season, as our current home inventory is down to 3 tires. I also took a flyer and picked up 6 the 700x23 Fortezza SE's being offered by Jenson USA for $18/ea. Performance has offered these in a blue sidewall model for $24 the past couple of seasons which led me to think SE meant Smurf Edition. Some folks up in New Jersey who we know have reported pretty good results with the SE models and seeing these in a black sidewall model for $18, I figured what the heck. They only use a 50 tpi casing vs. the 120 tpi used on the regular Fortezza and seem to be a bit heavier but the cost difference was too hard to pass up. Will advise on their performance compared to the regular Fortezza's after we log some mileage.

Last edited by TandemGeek; 12-25-07 at 03:05 PM.
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Old 12-25-07, 04:15 PM   #8
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BikeTiresDirect.com has the the Ultra Gatorskins in 700x25mm for $26.95. They have a clone site called Western Bikes.com or something like that where you'll find similar pricing. I've used BTD as the source for our Vredestein tires for several seasons now and with a few exceptions, BTD seems to offer very competitive pricing all the time. No affliliation other than being a pretty happy customer.


.
Bought my Ksyrium Elites from them this year. Tire pricing isn't as good as http://www.probikekit.com/
At least for my choices of tires. Bike tires direct only has the Conti Gatorskin in wire bead and so it is with Pro Bike. I checked the Conti website and they do make them in 25.
As for other brands. I've had such great results from Conti GP-4000 on my single riding 10000 miles a year that I am very loyal to Conti. The Gp-4000 in 25 will probably be just a good on the tandem.
There are several people in the local clubs that run 23's with out problems though I think that might be just a tad small.
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Old 12-25-07, 04:57 PM   #9
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I've run the 23's but finally decided that a bit more rubber on the road is a good thing with a tandem. Any variety of Conti's seems to give a good ride as long as you can pump them to 120psi.

As far as the folding tires go- I don't use them unless I find a really good price. I don't believe that the weight of a wire bead vs. kevlar bead makes that much difference compared to the overall weight of a tandem. I do carry a folding tire as a spare on the bike if we wreck one on a ride, but otherwise, I don't care if they fold or not.

Rick
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Old 12-25-07, 07:08 PM   #10
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I've run the 23's but finally decided that a bit more rubber on the road is a good thing with a tandem. Any variety of Conti's seems to give a good ride as long as you can pump them to 120psi.

As far as the folding tires go- I don't use them unless I find a really good price. I don't believe that the weight of a wire bead vs. kevlar bead makes that much difference compared to the overall weight of a tandem. I do carry a folding tire as a spare on the bike if we wreck one on a ride, but otherwise, I don't care if they fold or not.

Rick
Let see. 25 folder I just weighed 208gr. Wirebead 28, 318gr. That's 220gr or almost half a pound. Not just weight rotating weight. To this weight weinie it a difference worth a few bucks more.
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Old 12-26-07, 07:53 AM   #11
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Let see. 25 folder I just weighed 208gr. Wirebead 28, 318gr. That's 220gr or almost half a pound. Not just weight rotating weight. To this weight weinie it a difference worth a few bucks more.

That's mostly the difference in the amount of rubber you're seeing- 28's are heavier than 25's. I didn't look far, but the difference between a folding 700x23 Gatorskin and a non-folder of the same size and type is 47 grams. Not really very much of a difference when distributed across the probably 30-40 lbs of most tandems.

My guess is that you'll see something close to what I found for the 23's if you search out the specs for the 25.

Rick
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Old 12-26-07, 08:34 AM   #12
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My Santana came with wire bead 28c Gatorskins and after just over 2200 miles the rear looked worn enough to replace. Put on GP-4000's in 25c and took off over 100grams per tire. Gatorskins were bombproof but these have better ride, rollout. Even my wife noticed and she usually has no feel for changes.
I know these won't last as long and will be more flat prone but I think it's worth it, especially with the smooth usually clean roads here in SoCal.
On my single bike I can feel a difference in a 100g per wheel. Not a big difference, but it's there for sure. As noted above, the top end speed is the same. The improvement for me comes in acceleration. Maybe a little in climbing too, but mostly acceleration. This really helps on long, fast group rides and races. You don't have to work as hard coming out of corners to stay on the wheel in front of you. This little bit of energy savings can add up over a long ride or race. I don't run stupid light stuff, so for me it's not about looking for an advantage, it's about decreasing a disadvantage.

Shayne
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Old 12-26-07, 08:37 AM   #13
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That's mostly the difference in the amount of rubber you're seeing- 28's are heavier than 25's. I didn't look far, but the difference between a folding 700x23 Gatorskin and a non-folder of the same size and type is 47 grams. Not really very much of a difference when distributed across the probably 30-40 lbs of most tandems.

My guess is that you'll see something close to what I found for the 23's if you search out the specs for the 25.

Rick
From Conti site:
UltraGatorskin 700x28 320g --------------------My original tires
Grand Prix 4000 700x25 215g ------------------New tires

UltraGatorskin 700x25 300g
UltraGatorskin folding 700x25 250g
UltraGatorskin 700x23 280g
UltraGatorskin folding 700x23 230g

No folding 28 Gatorskin to compare but these would be close:
GP 4 Season 700x28 250g
GP 4 Season 700x25 230g


Personally enough of a weight difference for me to stick with folding tires.
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Old 12-26-07, 09:21 AM   #14
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I guess I'm confused- I thought we were comparing weights of wired bead vs. kevlar bead in the same tire.

No doubt that a folding 25 will weigh less than a folding or wire bead 28. I just don't believe that the weight difference between a wire bead 25 and a kevlar bead 25 of the same tire is enough to get excited about, and given the way that tandems wear out tires, the ~$10.00 savings between wire bead and kevlar bead is worth running the wire bead (unless, as I mentioned earlier, you can find a good sale).

I do agree that you will notice an increase in performance if you switch from a 28 to a 25 (whether it is wired or kevlar), but I think it has less to do with the weight than the fact that the 25 will be able to hold more pressure, and therefore give you a livelier feeling ride and more precise handling.

Whatever the reason, I'll bet you'll like it better. I can't stand 28's on my tandem.

Rick
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Old 12-26-07, 09:44 AM   #15
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I would love to compare wire to folded straight across but Gators don't come in folded and Gp-4000 don't come with wires. But using the info above it looks like wire adds 50g. 25 to 28 adds 20g.
As for tire pressure I run 120 in bothe th 28 and the 25 and the 23 on my single.
I think part of the comfort and rollout factor also comes from the casing on the GP-4000 being less ridgid than the Gatorskins.
Yes, so far 100 miles in 2 days and I'm sold.
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Old 12-26-07, 06:10 PM   #16
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Another bonus for kevlar beaded tires: easier mount/dismounting of tire.
Can mount/dismount most kevlar tires without use of tire tool(s).
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Old 12-26-07, 07:29 PM   #17
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Another bonus for kevlar beaded tires: easier mount/dismounting of tire.
Can mount/dismount most kevlar tires without use of tire tool(s).
very true. The wire bead Gators were a bear. These 25 GP-4000's were not as easy as my 23's on my single, but I suspect that is rim differences. Ksyrium vs Fir w400.

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Old 05-30-08, 07:05 PM   #18
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Has anyone here used both the 700x23 Gatorskins at 110psi and the 700x25 Gatorskins at 110psi and noticed any difference in ride quality?

I've got the 700x23's now and like them but want to try the 700x25's in the folding version which Continental advises the user to inflate them to 110-120psi. That being, I'd be running the 25's at the same pressure as the 23's and I wonder if I'd notice a difference in ride quality or protection to my rim.
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Old 05-31-08, 02:41 PM   #19
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Re. 23mm vs 25mm pressure, the pressure drives the amount of rubber that touches the road to support your weight. The tyre will deflect until the force from the pressure inside the tyre onto the road equals the force of rider plus tandem.

So if you each weigh 140lbs and put 140psi into each tyre, one square inch of rubber will touch the road per tyre. The important thing is that if you keep 1 square inch of rubber on the road and vary the width of the tyres, the shape of the contact patch will vary.

With a narrow tyre you get a long thin patch, requiring much deflection of the tyre wall and therefore high rolling resistance. With a wider tyre the patch is rounder, requiring less deflection and giving lower rolling resistance.

Coming back to the original question of what pressure you should run, the answer is that it depends what you wish to keep the same. If you run the same pressure in a 25mm tyre the contact patch shape will change, lowering rolling resistance. If you run a 8% lower pressure in a 25mm tyre [(25mm-23mm)/25mm], then the length of the contact patch and therefore sidewall deflection will be roughly similar meaning you will get similar rolling resistance and better comfort.

I recall that Christopher Timm has a couple of useful graphs on his site showing this effect.

Regarding the difference between cheap/robust and high end racing tyres, this is the single biggest difference you can make to a bike. The nasty hardwearing Bontrager wire bead, kevlar, sidewall like a flak jacket tyres that came on my Trek T2000 were swapped for Michelin Pro Race IIs and the tandem began to fly. We also ditched the stoker suspension post. Just to ensure it wasn't a placebo effect I put the Bontragers onto my commuter bike. Yup, boneshaking ride and poor roadholding is there again.

My second advice is to use Conti supersonics or other 50g inner tubes. Saving 100g from your wheels makes another noticeable difference. Yes they require care to avoid punctures when installing (and perhaps ruin an evening if you're trying to install onto Campag rims), but in my experience they puncture and go deflate in exactly the same way that other inner tubes do.
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