A good, Fast, 25c tire?
 

I tried a set of 25c and really liked the ride quality but they seemed sluggish. Is there such a thing as a fast 25c tire?

Any overinflated 25c will roll well, but there goes the ride. All 25c tires are heavier than if they were the same design in a 23c, so they'll feel sluggish when you're swinging the bike around.

Of course everyone else on BF can "feel" that kind of weight difference when riding normally, even though the physics doesn't add up to a perceptible difference.

Conti GP4000s work for me.

+1
People are more influenced by marketing than they let on. With tires inflated to similar pressures, there's no perceptible difference in energy efficiency/performance.

If you're looking for good all-purpose tires, Michelin tires seem to do very well. The continentals I've had are great for carving apart corners, but they seem to wear much faster than every other brand I've tried.

Here`s where I`m at now. Loved the Michelin 25c tires that came on my new wheels but they were like magnets for stones and got cut too easily. I have conti ultra sports now. They dont pick up stone,glass,etc.. but I swear its like riding with a brake pad dragging.

Under normal riding conditions on reasonably smooth, straight roads, you shouldn't notice any difference. Unless, of course, the recommended inflations are different. The contis are probably recommended for 100-120 psi. I usually run my tires just over recommended inflation by 2-3 psi, and inflate my tires every couple few rides.

ribmo's

In general a 25mm tire will have lower rolling resistance than a 23mm tire. The reason is the contact patch is not as "long" and therefore the tire deforms less.

The Continentals are probably a significantly worse rolling tire than your Michelins. Most continental tires tested with fairly high rolling resistance prior to Conti using black chili, now they are more middle of the line. If you look at the chart I linked to below, the 23 version of the Ultra Sports is about 5 watts slower rolling than GP4000s and Michelin Pro Race 3s PER tire. Which is definitely something a person could feel.

I find Bontrager's lower end tires roll fairly well without being prone to flatting and come in 25 widths.

Here is a very comprehensive set of rolling resistance data, look to the column of crr - which means coefficient of rolling resistance, lower is better. (Also, keep in mind the person collecting the data is doing so for the purposes of time trialing mostly, but also as a service to people and companies. So while a .00300 tire may seem like a "high" rolling resistance, it's quite reasonable for a day in day out training tire) :

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

Al, who does the above testing, is a very competent tester of tires. He uses a powermeter which he checks calibration on, accounts for changes in temperature and pumps them up to the same pressure every time.

I have been very impressed with Michelin's Pro Optimums. Best balance of ride, stability, traction, and speed that I've found.

I like the Conti GP4000 in 25mm. I have a set on my FG and they have a nice feel.

Well, that's the key there. 25s are rated at a lower psi than 23s. When you inflate to a given tire's max/recommended psi, the 23s are usually a touch lower crr. That makes a difference because a 25 will blow off the rim before a 23 at higher pressures because of the increased surface area straining against the same bead contact area/hook strength.

I thought that was the point of fatter tires. I'll pump my 25s to 85-95 and it's like a Town Car in comparison to 23s at 120.

I think this is an instance of looking at the trees not the forest.

So, there are two ways you can increase rolling resistance:

The first, is to run a pressure so low which allows for additional hysteresis in between the tube, tire and road.

The second, and more consequential form of rolling resistance, is the speed lost to surface irregularities with a tire pressure which can not deform to road surface changes. By running too high of a tire pressure, you are in effect "bouncing" over the road and not letting the tires do their job of shock absorption.

Typically for a perfect balance between the two forms of rolling resistance you should be nowhere near a tire's max PSI. For many riders, you should be in the 100-110psi range. Such that your tire can deform to road irregularities but that you don't have a significant loss of hysteresis between the tube/tire/road interface.

Most rolling resistance data shows that a wider tire rolls faster even in a laboratory sense. And additionally, most on road tire testing shows that above 120psi a person sees significant loss on any road that is less than ideal.

It is counter intuitive that 25mm tires pumped to a moderate pressure roll faster than 20mm tires pumped to their gills, but it's not opinion. It's data.

Where's that data? Even the link you posted suggests otherwise.

Wider tyres roll better but are, obviously, heavier and less aerodynamic. However, unless your "feel" is much more sensitive than mine, I defy you to find a 25 conti 4000 or schwalbe ultremo "sluggish".

Well the data I've linked to is for the first type of rolling resistance, hysteresis losses between tube/tire/road. And yes, higher pressure yields lower crr on rollers.

What the link doesn't address is losses from varied surfaces.

Below you'll see a graph from some testing, though not completely dispositive of the issue, it shows the trend I've seen in the past:
http://www.slowtwitch.com/articles/i...ium_tires3.jpg

Also, I believe Schwalbe used to have on road data. Members over at biketechreview.com have done some testing. Al(collector of first data set) tried working with a "bumpy" roller but it never seemed to work the way he wanted.