TJHOO

..better grip on hilly terrain with treacherous descents?
..much slower on the climbs though?

IKYR

25c are better in alll conditions IMO...

pjcampbell

I started running 25cs and so far am happy. I have been experimenting with low pressure... running something like 95 rear/85 front PSI now, but sure I could get away with 90/80. That is on a pretty skinny 19mm or so wide Zipp rim. I find the ride a bit more comfortable. I weigh 165 or so with all my crap (spare tires and co2 cartridges, cell phone, etc).

StanSeven

Depending on the brand and model, rolling resistence could be less too.

jfmckenna

I used some 25's in a race a few weeks back because it had gravel road sections.

wens

I just had to triple check whether I was reading the 41 or the 33. :facepalm:

rpeterson

I've found if I'm TTing on bad chipseal I'm about .25mph faster on 25s than I am on 21s at the same power, even without the aero rims.

zigmeister

25c GP4000s at the same pressure roll smoother, and I must be 3mph faster..haha.

Continental says they are better rollers with less resistance than their 23c. YMMV with other brands, but the grip during criteriums and tight corners are great, and ride is nice. The problem is with my forks, you really have to pay attention when putting the front wheel on to get them straight/even, otherwise, they will rub the fork.

Creakyknees

how about tubulars? what are some good 25 width toobies?

jfmckenna

FMB 25's are smooth as silk and soft as butter.

TJHOO

Anybody used Michelin pro race 3's in 25c?

rruff

1) Maybe
2) No... probably faster if the casing is the same.

Wide tires will mess up the aero properties of your wheels, so if you like solo or small group breakaways, don't go big... and consider going smaller.

carlosflanders

Yes. They roll great and handle rough corners significantly better. They actually measure 27 mm and wear somewhat better than 23s. The 23s measure 24 mm, btw.

TJHOO

maybe that's why the PR3's feel more smooth than Conti GP 4000's (imo...if they are actually wider...don't know the actual width of the 4000's)

TJHOO

[QUOTE=Wide tires will mess up the aero properties of your wheels, so if you like solo or small group breakaways, don't go big... and consider going smaller.[/QUOTE]

good point..if it's true....you pretty sure of that?

zigmeister

I think it is accepted that although there is a very slight penalty with the 2mm wider tire for drag, that is more offset by less resistance/friction, thus it rolls faster. Also, the other benefits of a smoother ride and better grip and not disputable in favor of the 25c. Having both GP4000S 23c and 25c, the difference is very obviously between the two for comfort/smoothness and grip.

AzTallRider

I wouldn't consider this to be "accepted". I used 25's for a year, but have settled on 23's, as I believe them to be faster. Every test I've read that purports to prove that wider tires have lower rolling resistance performed their tests at relatively low psi, thereby exaggerating the deflection of the tire. At 120psi, I believe a 23 has lower rolling resistance than a comparable 25. This database of test results would appear to support that:

https://www.biketechreview.com/tires_...sting_rev9.pdf

pjcampbell

no need to run 120 psi in most cases though.

Hida Yanra

my n=1

I used 25s all last year for racing. I loved it.

AzTallRider

Maximizing performance for a given tire dictates using a psi, determined by your weight, that provides optimum deflection. In my case (90kg), that is ~120psi on the rear, and ~110psi on the front. I'll be adding to that with the tubulars I'm putting together for racing, and that range also matches the pressures Vittoria recommends (using Vittorias on the racing wheels).

But then, the aero qualities of your tire/wheel combination outweigh every other consideration, for everything except very steep (slow) climbs.

rruff

Sure as my faith in the guys who have tested it...

rruff

The first part you have backwards. The tire is quite important for aero properties where you'd prefer the casing to be the same width as the rim... but there is little decrease in Crr going from 23-25mm. If you also drop pressure, it could easily go in the other direction.

If you need a bigger tire to prevent rim damage, that is certainly a consideration. There is always a chance of that in races because you often can't see far ahead.

FlashBazbo

I love the humor you find on this forum!

zigmeister

Well, it goes both ways depending on the brand. The FMB silk strada tubular wider version had less resistance. In the case of this thread, Continental claims a lower rolling resistance for the 25c than the 23c. I have no data to back that up, just taking their word for it though.


Also, many of those tires that are the same brand/tube if clincher, had values that were within .00001 to .00004 difference. And the standard deviation was often the same, nullifying any difference in many of the tires. In essence, they rolled the same for width and pressure.

So that goes back to better ride, better grip as a benefit over the narrower tires amongs same brands/setups. Aerodynamically, hard to know those numbers also with variable of forks, wheel design etc...the wider tire could be a benefit for a particular rim and width/depth over the narrower tire. That is speculation until somebody actually tests tires, different width, and different wheels.

Is there any data to show how this all translates into actual performance in a race situation? From best to worst, it shows a 10watt spread. But amongst the top 20, a few watts, which really almost translates to nothing real world.

rruff

They have... narrow tires are better for aero and generally faster overall at racing speeds... and I'm referring to 20mm vs 23mm. The reasons to go wider are rough roads, grip, etc.