25c or 23c wide tyre ?

NRS_Comp1

Hi,

I've read this week on velonews an article that stated that 25c wide tyre are not only faster but more comfortable. Let's just say I'm a bit skeptical about wider tyre being faster. I'm in the process of buying new tyre and I'm pondering if I should go a try wider tyre. I'm mostly riding on the road as training for mtb marathon racing so I'm not looking for ultimate performance and won't be racing but I'd definitely wouldn't mind having a faster tyre. Have any of you guys tried a 25c wide tyre recently and how does it compare with a smaller 23c ? Thank you all for your answers !

Cheers !

alihisgreat

NRS_Comp1 wrote:

Hi,

I've read this week on velonews an article that stated that 25c wide tyre are not only faster but more comfortable. Let's just say I'm a bit skeptical about wider tyre being faster. I'm in the process of buying new tyre and I'm pondering if I should go a try wider tyre. I'm mostly riding on the road as training for mtb marathon racing so I'm not looking for ultimate performance and won't be racing but I'd definitely wouldn't mind having a faster tyre. Have any of you guys tried a 25c wide tyre recently and how does it compare with a smaller 23c ? Thank you all for your answers !

Cheers !

there is a weight penalty... but you should only be really concerned about this if you are a climber.

and some frames have might clearance problems for 25mm.

slowondefy2

Why are 25 tyres faster? If the 23 is pumped up correctly I don't see why the deformation of the tyre should cause more rolling resistance.

huuregeil

slowondefy2 wrote:

Why are 25 tyres faster? If the 23 is pumped up correctly I don't see why the deformation of the tyre should cause more rolling resistance.

Becuase the casing deforms less; because you can run them softer without pinchflatting (the reason for the comfort gain) and reduce suspension losses on rough roads.

I use 23s for racing (where weight and aero comes into play), 25s for everything else (including racing in the rain for grip reasons). The 25s feel just as fast, I really don't notice the difference; saying that, the tyre I went, wow, that feels noticeably quick, was a 25mm Michelin PR3.

For what you're doing, go 25, no disadvantages, and some meaningful advantages.

slowondefy2

But if the 23 is pumped up sufficiently, does the sidewall still deform more than the 25?

It's a given that a 23 needs more pressure than a 25, right? Except that most of the comparisons I've seen between 25 and 23 are with the tyres at the same pressure, which clearly puts the 23 at a disadvantage.

balthazar

All else even, wider tyres cause lower RR (Rolling Resistance) than narrower (within limits), for well understood and documented reasons. However, as the above comment notes, RR always reduces as pressure increases, and narrower tyres can be inflated to higher pressure, so the characteristics tend to cancel each other out. Note that RR is a technical term, not a general description of overall cycling efficiency, which has other influences. It may be that large-volume tyres allow quicker progress even if their RR is relatively high, because they smooth out the road surface.

High volume tyres weigh a tiny bit more, and present a fractionally larger surface to the air.

Apart from that, the market has its say, and tyres of light construction tend to be narrow, and chunky durable tyres are wider. Slick tyres with thin tread and finely woven casings are simply not available much above 23mm, more's the pity.

Apart from all that, the RR difference between 23 and 25 tyres is slight, outweighed by other characteristics like casing construction and tread type, and doesn't matter that much anyway. These discussions are interesting academically but have little to do with how much fun your bike rides are.

I like wider tyres for the extra grip, and I have a conceptual dislike of chi-chi tread patterns which only reduce grip and add RR, so I'm continually on the lookout for wide, fine-cased slick tyres with black carbon tread.

alihisgreat

slowondefy2 wrote:

But if the 23 is pumped up sufficiently, does the sidewall still deform more than the 25?

It's a given that a 23 needs more pressure than a 25, right? Except that most of the comparisons I've seen between 25 and 23 are with the tyres at the same pressure, which clearly puts the 23 at a disadvantage.

I'm assuming this is the reason behind the lower deformation of 25mm tyres:

@100psi the surface area of the inside of a 23mm tyre is (pulling a figure out of the air) 10inches^2

so thats 1000lbs of pressure on the tyre (100psi x10inches^2). with a contact patch of? 1/2 an inch^2

= 50pounds of pressure on the contact patch.


@100psi the surface area inside a 25mm tyre is greater, lets say 15inches^2 for the sake of the example

so thats 1500lbs of pressure across the surface of the tyre. with a contact patch of? 3/4 of an inch^2

= 75 pounds of pressure on the contact patch -> more pressure = less deformation.



I've picked the figures out of thin air; but I think the logic is sound.


So a 23mm does need more pressure? -> but then it becomes harsh as it doesn't dampen vibration as effectively (less mass of rubber), and the tire isn't as tall so doesn't roll over small bumps as easily.

Eyorerox

I use 25 tyres, less pressure required = comfort. A highly inflated tyre will on rough road surfaces have a greater rollong resistance than a less inflated tyre, the opposite would be true on a smooth velodrome.
have a look at this
http://www.bikequarterly.com/images/TireDrop.pdf

Matt Square

I went from 23 to 25 GP4000s and found them a lot more comfortable on Long rides.

NRS_Comp1

Thanx for all your replies , I will give the 25c a shot, because I think the weight difference will be offset by the better traction and especially the higher level of comfort.

Cheers !

nferrar

I used to ride 23's and now generally ride 25's although I personally can't tell the difference (and I can't even fit them + guards on the winter bike where they'd be most appreciated). If you're used to 23's I'd give 25's a go when you next need to replace but I wouldn't switch from 23's with life left in them.

lostboysaint

Matt Square wrote:

I went from 23 to 25 GP4000s and found them a lot more comfortable on Long rides.

Just done exactly the same thing on the recommendation of the LBS and found that their reasoning (comfort, feels faster rolling etc.) was exactly right.