Carbonfiberboy 

They're about the same thing. The Krylions haven't been made in some time but are still available NOS. PRO4 25mm tires run huge, ~28mm on my 23mm rims. I'd go with the 23mm PRO4. Haven't run them, so don't know what they measure, inflated on the bike.

Lazyass

They are being made again, for at least the last year and a half when I got my first set with a March '14 date on them. Michelin just doesn't have them on their website. I think they struck a deal with Nashbar/Performance. Much better deal than the Pro4's.

Carbonfiberboy 

Interesting. I wonder what the differences between them and the PRO4 are? For some time Performance had Vredestein SE tires made for them and sold at a much lower price. They were most definitely not the same as the regular Vredestein models of the time. Terrible rubber.

Jakedatc

23's are about 25 on my rims. I haven't had any issues with them.

berner

I use a 25mm tire in front and a 28mm aft. My experience is that any decent tire will be fine most of the time, though quality tires will be faster. I'm slow so that being fractionally faster is of little consequence. Where I do see a significant difference with, say Conti 4000s type tires is on chip seal. Quality tires make chip seal road surfaces endurable.

dr_lha

It really depends on the rim I think, especially as you have wide 23mm rims.

I run 23mm Pro4s (I've had both Service Course and Endurance V2 versions) on Velocity Deep-V rims, and they measure almost exactly 23mm, measured with digital calipers.

Lazyass

The only difference I ever read about was a claimed 15% traction increase with the Pro4. IMO that's pure marketing, I don't think there's a single difference. It's probably the exact same tire with a different name. I put almost 5000 miles on the Krylions, with zero flats, and then put them on a spare bike. Never had a traction issue.

Carbonfiberboy 

Thanks, I was curious about that. But the 25mm size really is big - it's not just the rim which might make a 1mm difference.

floridamtb

I hear all this talk about 25mm, is there really that much of a difference? I find it hard to believe that 2mm could impact your ride so much. I have always rode on 23mm since coming over from MTB 2.5 years ago. Just put on a set of Conti Gran Prix's that I won in a ride raffle. I like them but I'm wondering about trying the GP4000S but not sure if I should try this 25mm thing or not.

Jakedatc

it's not necessarily the width.. it is the added tire volume that gives you a softer ride at appropriate PSI. you can run lower pressure with larger tire.

bbbean 

Yes. Cornering and ride quality are substantially better on 25s. Some say aero is better as well.

BB

Tubernator

I am still a newb with all of this, but have tried several tires over the past few months. The Conti 4000s are nice tires, and my bike came with the Bontrager Race 3s, which are really not bad either, but my favorite to date are the Panaracer GravelKing tires, running 26 in back and 28 in front. The traction is absolutely killer, works great on the road, holds up well and seems durable. Would do 28 in the back, but brake track wouldn't take it.

Very underated road tire, don't let the name fool you, although they can also do some gravel riding with no problem.

dagray

Schwalbe One tubeless tires... you can choose from 23mm all the way to 28mm.