Basic TT Tire Setup
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  1. #1
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    Basic TT Tire Setup

    Folks,

    I'm going to try my hand at some time trials next season and have pieced together a bike for the job. My question is: What is a good basic tire setup?

    I'm 160 lbs on a 56 cm frame with 700c wheels (not deep dish). I will be doing some time trials on a track (Lowe's Motor Speedway) and some on the open road (20-40k).

    From reading previous threads and looking over other information, it seems to me that a 700x20 front and a 700x23 rear would be a reasonable setup. I'll train on whatever I can get my hands on cheaply, but would be happy to change tires to something lighter if it would be of any benefit (relatively) without greatly increasing the risk of flatting.

    So, what would be a good basic setup?

    Thanks,
    Greg

  2. #2
    wim
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    Quote Originally Posted by VinPaysDoc
    From reading previous threads and looking over other information, it seems to me that a 700x20 front and a 700x23 rear would be a reasonable setup.
    Yes, it's a good setup. A 700x20 front setup is slightly more aerodynamic than having a larger tire up there, especially if the 20 tire is the same width as the rim. At its recommended pressure, the 20 also has less rolling resistance than a 23 at its recommended pressure.* While these gains are relatively small, preparing your equipment for a time trial is all about gathering as many small advantages as you can.

    *Larger tires have less rolling resistance than smaller tires only at identical pressures. But you don't ride a smaller tire at the same pressure as you would a larger one, so that bigger = better argumentation is simplistic as far as rolling resistance is concerned.

  3. #3
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    I would go 23 front and rear unless all you TTs are one Lowes (which got resufraced last year and I hear is super nice). I use to run a 21 on the front in road TTs but I found that the handling and ability to ride over rough stuff (esp in the aero bars) was much better with a 23, that is at least for me at 6'4" and 178lbs. However you could have both tires an just switch preping your bike for TTs is part of the game I def switch stuff up sometime esp if I know the roads are bad or its going to be raining.

  4. #4
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    it depends

    For most time trials, weight is the last thing to consider vs. aerodynamics, rolling resistance, and reliability.

    It sounds like in your case a 23 rear and 20/21front would be a great choice. A trustworthy-but-still-fast 23mm Michelin Pro2Race would work well for the rear, and then maybe run a 21 Michelin ProRace Light up front. I actually don't like the feel of Michelins all that much, but it's hard to argue with their rolling resistance data, price & availability, and reliability. This combo will be marginally slower than a pair of Veloflex Records or Pro Lights for example, but significantly more reliable, especially on the rear wheel. Flatting is a bummer, especially in a stage race. Anything else along these lines will work fine. But beware, as someone else alluded to, a lot of newer rims are relatively wide, so a 20/21 front tire may actually be far worse aerodynamically than a 23.

    Part of it comes down to practice riding a tt bike with a narrow front tire, but for courses with tricky corners and/or rough chipseal, I'd use a 23 tire. The average speeds are slower on these types of courses to begin with, so the aero benefits of the narrow front tire are smaller (and were never that profound to begin with). Being able to run lower pressures and race comfortably, and rail corners instead of chattering through them will more than make up for any aerodynamic or arguable rolling resistance loss. Some courses are sort of in between in which case it becomes a judgement call based on your preference and available tires. If in doubt, it's never wrong to use a pair of standard-weight 23's.

    Latex tubes are also worth considering, especially if you can get a pro deal on them. The next best place is www.probikekit.com. Get the 18/20's. The 22's are quite large and hard to stuff into my 22 mm Veloflexes. Current latex tubes aren't any lighter than butyl tubes, but every resistance test I've seen says they're faster than the thinnest butyl tubes out there. They lose pressure overnight and cost more, but I have also found them to offer slightly better puncture resistance. Also, when they do go flat, it's always been a slow pressure letdown rather than sudden loss, at least in my experience. This is in stark contrast to those 50-75 gram butyl tubes that explode if they get within 10 feet of broken glass. Small sample size, perhaps, but I still think they're worth using. They certainly don't hurt if you're already pushing the envelope with thin tires.

    All that said, don't over-think the tire thing. Spend more time obsessing over your position and training.
    Last edited by BenR; 11-17-2007 at 04:08 PM.

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    Thanks for the reply. The only road TT I plan on doing next year will be at the Asheville Omnium. I'm going to try out a Michelin Pro 20 front on the Nimble Spider rim I've got on some of the roads around here. The course in Asheville is an out and back along the French Broad River and I don't remember it as being too rough. Of course, I was anaerobic for most of that journey and things remain a bit fuzzy.

    Greg

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    Ben,

    Thanks for your reply. Wim too, for that matter.

    I had read about the latex tubes on Michelin's web site. I had also thought that a lighter front tire would not present as much of a puncture hazard as a light rear. Your choice of the 23 Pro2 for the rear and 20 ProLight for the front sounds very reasonable. The slow leak of the latex tubes should not be a problem when airing the tires just before the TT.

    Thanks for your input.
    Greg

  7. #7
    Juanmoretime
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    A 20 is a pretty narrow tire. You also have greater rolling resistance with a much smaller contact patch on the road with a 20mm tire. With the rims you are using you will need to go pretty fast to have the aerodynamics be more beneficial over the less rolling resistance of a 23mm tire.
    For my next trick I will now set myself on fire!

  8. #8
    wim
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    Quote Originally Posted by Juanmoretime
    A 20 is a pretty narrow tire. You also have greater rolling resistance with a much smaller contact patch on the road with a 20mm tire. With the rims you are using you will need to go pretty fast to have the aerodynamics be more beneficial over the less rolling resistance of a 23mm tire.
    Actually, you have less rolling resistance with a smaller tire if you inflate it to its recommended pressure. The hard-to-kill smaller tire = more rolling resistance cycling lore is based on a notion that doesn't apply out on the road.

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    Talking an alternative philosophy

    Perhaps the best advice I ever heard was from a friend/mentor who raced for Prime Alliance. He told me that placebo is a wonderful thing, and given a choice, he'd use whatever gear gave him the biggest hardon! There's probably more truth to this than anyone wants to admit.

    Best of luck and happy suffering!

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