Road Cycling - Anyone have an opinion on....

Michelin Axial Bi-Sport tires? The Vittorias that came on my Bianchi Campione are looking worn after only 450 miles, and I was thinking of getting the Axial Bi-Sports. I know it's heavier than the Axial carbon, but I'm more concerned with durability than speed, unless the difference is huge. I also like the look of the tire. In addition, I'm thinking of going from a x23 to x25 tire, as I've read that the rolling resistance is actually less than the 23. Is this true? Thanks for the help.

Go with the Performance GT2Kevlar for less than $8 !

unless I read your post wrong, there is more rolling resistance with a x25 than a x23.

Originally posted by Syd's bike
In addition, I'm thinking of going from a x23 to x25 tire, as I've read that the rolling resistance is actually less than the 23. Is this true?
I read that somewhere too, but cannot confirm the source. Does anyone know if it is true? It may be somewhere in this board, or a magizine or some other website, but I remember reading 25 has less rolling resistance than 23. Is that possible????

I don't see how it would. More rubber touching the road equals more friction. But of course there is probably some freakish phiysics formula proving me wrong somewhere out there :).

I think I read somewhere that there is more tire flex with a 23, so there is actually more rubber in contact with the road than a 25. Sounds strange, though.

Knifun,

Is that $8 tire any good? How long did it last you? How many flats? You always hear you get what you pay for, it's hard to believe an $8 tire is any good.

I'm running the bi-sports right now, and like them. Good wear, looks like I will get about 2500 miles out of them. Good in the wet, as well.

I'm a Clydsdale, at about 220 lbs, and run 25 mm tires. Feel like they are faster for me than 23 mm.

Now for the physics part: for a given weight and tire pressure, your tire footprint is such that tire pressure x area of tire contact patch = total bike weight. A wider tire has to flex less to get the same size contact patch. Less flex means less energy lost to hysterisis in the tire. But, as you go wider, you get more air drag, cannot run as high a tire pressure, so there are tradeoffs all around. Wider tires mean lower air pressure, softer ride.

How about a 23 in the front and a 25 in the back?
:thumbup:

SYD,
I have over 2,000 miles on the tire. I use the new SpinSkins Dura Liner, no flats! A little heavier than the racing tires, but I use these for the training bike, which is 10 pounds heavier than the racing bike anyway. Besides, at $8, if you are not happy, Performance will take it back.

If you are really concerned about rolling resistance, use tubulars.

Originally posted by Da Tinker
How about a 23 in the front and a 25 in the back?
:thumbup:
Well, maybe Conti was listening, how about 22/23?:
Conti Attack/Force (http://www.cyclingnews.com/tech/2002/tradeshows02/?id=eurobike02/conti)

Thanks for the info, everyone! I've learned a few things...still not sure if I'll go with the bi-sports, gatorskins, or those $8 jobs. Tinker, are there any disadvantages with running different size tires front & rear?

Originally posted by kewlrunningz
I don't see how it would. More rubber touching the road equals more friction. But of course there is probably some freakish phiysics formula proving me wrong somewhere out there :).
It is the shape of the contact patch and deflection. 23c tires have less rolling resistance than 20c.

edit #1:
oops, datinker said the same thing-sorry. Anyway, it's all true!:D

edit #2
About the only significant way tires lose eneergy is in flex. All tires deform at the contact patch...The tire does spring back to its round shape, but not with 100% efficiency. Some of the energy is lost as heat- not really noticeable by us on bicycle tires, but place a hand on your car's tire tread next time you park and feel the warmth. That heat comes from tire flex (and a bit of friction between the tire and the road), and the eneregy that goes into heating that tire is energy that deos nothing for us as far as going down the road. It's lost energy.
contact area= tire pressure/ weight. 100psi tire supporting 100lbs has a contact patch of 1 sq inch.
width has nothing to do with how big the contact patch is, but it does influence the shape of that contact patch. to make a 1 sq inch patch, for instance, a narrow tire winds up with a long contact patch while a wider tire ends up with a shorter one. The shorter footprint means you end up flatening less of the tire's casing to achieve it, which means you're flexing less tire and consuming less energy rolling down the road.
Additionally, a wider tire corners better due to the shape of the contact patch (which presents a more stable better-balanced profile to the road).
So why aren't Tour de France racers on 35-mm wide tires? Tooo wide means more aero drag- plus a bigger tire is heavier, which hurts climbing and acceleration...
No I am not this smart- this was written by Garrett Lai

Go with the Michelin tires. You can't beat the performance or the endurance of the Michelins. I rode the same set of Axials from the beginning of June 2001 to August 2002. I just changed them out to Michelin Pro Race--excellent tires.

I used the Performance tires last year on my hybrid. They royally sucked. They were nice for the first month and deteriorated quickly after that.

Good luck!

SYD,
Only problem I've found with running two sizes is that you can't rotate tires fore/aft. When I'm running same size, when the back wears thin, I will rotate the front to the back, and but a new in the front. Yeah, sometimes I act like the tight-wad old Scot I may yet become.
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