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Road race front wheel size(18 posts)

Road race front wheel sizetandem
Dec 10, 2002 6:11 AM
I have a 700 x 19 tubular mounted on a Zipp 404 that I use for time trials, I was wondering if it would be safe to use it on a road course or crit. I feel fine with it on the TT course but there aren't a lot of turns. I've had some guys tell me that they would not feel comfortable with such a narrow tire up front on a fast curvy descent or a tight crit course. What do you think?
I wouldn'tDougSloan
Dec 10, 2002 7:16 AM
I've done the same thing. With less than 20 mm's, it seems you lose some grip and feel. The transitions are more abrupt, and you usually run more pressure to avoid pinchflats (or rim damage, in the case of tubulars). The handling goes all to hell.

I've switched to Tufo 21 mm tubular tires for everything. It more closely matches the width of the 404 rim, anyway, which is what you want, right?

I always do crits on 19'sSherpa23
Dec 10, 2002 7:31 AM
Prior to May, when I received some carbon rims made specifically for 22mm tires, I used 19mm tubular tires exclusively for road racing and crits. There is no difference in cornering and grip between 19's and 22's. The only place where you give something up is when you are riding on a rough road. I wouldn't worry about it. If you are using a 19mm something as clunky as a 404, however, make sure that the tire goes all the way to edge of the rim.
re: Road race front wheel sizetandem
Dec 10, 2002 10:59 AM
My mistake the front wheel is from a 909 wheelset which is narrower than the 404, that's why I went with the 19mm tire.
Dec 10, 2002 4:31 PM
I think the front wheel of a 909 set is a 404. At least mine is. The width of a 22mm Tufo is almost identical to the rim.

I don't understand why bikes would be different than motorcycles or cars, this is, that more rubber means more grip. The transition from upright to leaning will be less abrupt with a wider tire, and you'll have more shock absorption, which might be critical if you hit a bump in turn if you are near the adhesion limit.

Let's clear up some thingsSherpa23
Dec 11, 2002 7:13 AM
You cannot compare 19mm tubular to 19mm clinchers, which is what you might be doing, Doug. Clinchers are totally different. Clinchers are elliptical by nature while tubulars are round. If you are trying to post advice about 19mm tubulars based on your experience with 19mm clinchers, please say so because it would be very misleading to some if you are. And I am unclear what you mean about "rim damage" with 19mm tires. The transitions are just as smooth with 19mm tubulars as they are with 22mm tubulars. And not all 19mm or 18mm are equal. A Continental 19mm is close to a TUFO 21mm, for instance. In my experience, in all of my years or racing, you cannot feel any difference cornering between 19mm and 21mm tubulars.
I assumed we are talking about tubularsDougSloan
Dec 11, 2002 7:59 AM
I would never, ever, use a 19 mm clincher. The risk of pinch flats is just too great.

I agree that we might be talking apples and oranges if we are not talking about the same brand (or air pressures). My experience is limited to Contis, Vittorias, and Tufos, and lately mostly Tufo's. In the last year I've probably put several thousand miles on tubulars, as I've gotten much bolder in choosing to use them with the Tufos with sealant installed.

A larger diameter tire will roll over less suddenly, in effect, more smoothly but more slowly. While we are talking about small differences here, it's sort of one of those physical properties of tires. The extreme example of where this can be readily seen is in motorcycle riding, in which I've done a whole lot of.

I'll agree that air pressure may make more of a difference in feel and grip than the size of the tire. A 19 at 130 psi may feel like a 22 at 150. So, again, apples and oranges.

If you are sold on 19's, can you offer any justification for 22's or larger?

The rim damage concerns hitting objects or potholes. A larger tire gives a greater cushion between the object and the rim. I actually did dent a tubular rim, once. Can't recall the size tire or pressure I was using, though.

I'll certainly defer to your experience for recommendations; however, I think I can tell the difference, and this is based on a whole lot of twisty mountain descents on these various tires. If my life depends on it, I'll choose the 22 width tire every time. YMMV.

Let's keep clearing things up...shirt
Dec 11, 2002 9:49 AM
First, I don't think clinchers are elliptical. I don't even agree that tubulars are effectively round. Both get 'squashed' as soon as there's weight on them, creating a mostly flat surface (even on your 19s) that then curves away from the contact point with the pavement.

Additionally, the "un-squashed" profile of a clicher varies greatly depending on the width of the tire AND the rim. Depending on this combination, your tire can look like either end of an egg in profile.

Regarding Doug's comments about motorcycle tire technology, I don't think there's much in common between the two. When I take my racebike out onto the track, the difference between 29 lbs and 31 lbs of pressure is tremendous. Heat (determined by tire pressure) is the most critical component of motorcycle race tire technology, and we don't deal with this at all on pushies.

The only point there that is valid is that the more rubber you have in contact with the road, the better grip you're going to have (ignoring rubber compounds for a moment.) This is why a 22 tubular will have more grip, better ride, and more rolling resistance than a 19 tubular. For clinchers, there are too many other variables to consider in this discussion. Clinchers suck anyway. :-)

If anybody wants to continue talking about compounds and carbon/silica content and how they relate to grip, I'd be happy to start another thread.


(ps: I know I don't usually post anything thoughtful to this forum, but tire technology is my hot button. Getting high-sided off racebikes at a ton and a quarter because of grip problems tends to generate interest in rubber...)
tire talkDougSloan
Dec 11, 2002 10:23 AM
I have shifted my tire priorities from weight, grip, and drag to primarily flat resistance. I have lost so much time in various events and training to flats that it justifies that as the primary consideration. It does no good whatsoever to be able to finish a road race, time trial, or crit 2 seconds quicker if there is a substantial risk, about 50/50 in my experience, in flatting. I spend far too much time and money preparing for events to risk effectively being knocked out from a simple thorn. That's why the Tufos with sealant; they are respectibly light, yet somewhat flat resistant, at least better than any tubular I've found.

tire talkSherpa23
Dec 11, 2002 11:38 AM
Doug, I see now that we are definitely on the same page. I was confused by the pinch flat reference. You are definitely entitled to feel a difference with the 19's vs 22's and it's not to say that I don't feel a difference - it's just that the difference does not translate into negative performance for me.

as far as riding Tufos: The sealant kicks ass, but the tires suck. I used Tufos exclusively for 2 seasons. They are the roundest, lightest, and most durable tire for sure and they deserve serious credit for that. The downside is that they ride terribly and have, by far, the highest rolling resistance of any tubular. I mean the rolling resistance in itself can cost you a race, if you add up the amount KJs used over the course of a race. Now I use Continental Comps or Sprinters with the Tufo sealant, and it works fine.

As far as the contact area goes, how much more contact area do you get with a 22mm? 2mm? I don't know, I am posing the question. However, I personally have never felt that it's significant enough to say that it performs better in ALL conditions.

Shirt, the round vs. elliptical thing: A bicycle clincher tire hooks on a rim making a not completely round shape. When you have significant pressure from an oblique angle, i.e. turn, the tire deforms more than if it were perfectly round, like a tubular. That is why clinchers do not transition quite as well in turns as tubulars do, especially at lower pressures.
BTW, this is a pretty cool discussionSherpa23
Dec 11, 2002 11:39 AM
I guess I am using a 19, after allDougSloan
Dec 11, 2002 11:58 AM
I realized that I am using a 19 Tufo on my Velomax Ascent Pro (Lew carbon) front wheel; I use this only on my "climbing bike", in which weight is the primary consideration, far above handling, comfort, or flat resistance (having a crew car); I pump the crap out of it, too. It almost feels like solid steel. Hard out of the saddle climbing, a rock solid tire feels great. No power loss.

The reason is that the Lew rim is so narrow anyway, that a 20 or wider sticks way out, so far I fear it could roll, and plus you don't get any aero benefit from a tire sticking out past the rim. So, I suppose I am using a 19, but in a very limited application.

Oh, I did use this wheelset on the nearby Climb to Kaiser (13,500 ft climbing, and descending, in 155 miles) a couple years ago, I think with 19mm Conti Sprinters. The handling totally sucked, as the front wheel slid on me twice on hairy mountain descents, which might easily have cost me my life. But, I did have them pumped to around 150. High pressure feels great climbing, but totally sucks descending/cornering. The tire felt like solid steel, with about as much grip. Corners I had routinely taken at breakneck speed I had to be very careful on, almost as if the road was wet. This may have been mostly caused by the pressure, though.

Dec 12, 2002 11:49 AM
Bikes are like cars, more rubber doesn't mean more grip. Traction is friction. Friction is area x CF x force

In pneumatic tires, force per unit area is the same as the pressure inside the tire. If the pressure goes up the area in contact goes down, the traction stays relativly the same, to a first order approximation.

Don't start with dragster, they have second and third order effects that are significant.
other phenomenaDougSloan
Dec 12, 2002 1:42 PM
You are speaking in a theoretical sense. I studied the heck out of this issue in my auto racing days. They discovered that the formula does not reflect reality. Rubber tires act like little fingers that grab irregularities in the pavement, not like perfectly smooth on smooth surfaces. Wider tires equals more little fingers, therefore better grip, all else equal. Ask anyone who races cars if wider tires equals better grip, and the answer is universally yes.

Nonetheless, wider and better grip is not always faster, as drag will increase, too. Formula V (Volkswagen) uses tiny little tires about 4 inches wide; the cars are so light and under powered that any performance gained in the corners would be lost on the straights in drag. At some point, bicycles would suffer the same effect. Put 2 inch slicks on your time trial bike, and it would corner incredibly well, but would be slow as hell in a straight line. 19mm vs. 22mm tires are the same, just on a much smaller scale.

bingo. (nm)shirt
Dec 12, 2002 3:54 PM
What did you think...53T
Dec 18, 2002 12:03 PM
...I meant when I said not to bring up dragsters? The issues you raise still do not apply to bikes, whose traction response closely follows first order approximations (theory as you say).
Save them for the TTLC
Dec 10, 2002 4:11 PM
You want more rubber on the front tire to handle any sharp corner or sudden movements (like having to slam on the brakes!) in a mass start event. I have had to jam on the brakes during the neutral rollouts amny times. Think about trying to stop at 25+ MPH when there is a crash and the road is full of scraped up bodies on your 19's! The course does not even need to be curvy, the crashes happen so fast and often along a straight stretch of road when you least suspect it.
How much do you weigh?Kerry
Dec 10, 2002 5:30 PM
This is a key determinant. The amount of rubber on the road is the weight your wheel is carrying divided by the pressure in that tire. If you are light weight, then you can reduce pressure and get a decent sized rubber patch on the road at reasonable pressure. If you're heavy, then you need to crank up the pressure and the tire becomes hard as solid rubber, with an adverse effect on traction and handling.