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25 or 23 Tyres

by louisadams
Sun, Feb 27, 2011 19:36
7

Hi All,
I'm pretty new to road cycling and was wondering what the pros and cons were for 700x25 and 700x23 tyres. I am currently using Michelin Pro race3 700x25 and think they are awsome.

If you're new please join in and if you have questions pop them below and the forum regulars will answer as best we can.

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7 comments

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Simon E | 13 years ago
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Chris, Michelin's graph is much simpler.

Latex tubes are known for not retaining pressure, even losing a significant amount overnight, but a good butyl tube shouldn't lose much over a week and certainly not 20 psi. I'd be swapping mine out if they did that.

If you're riding over cats eyes on a bicycle you're a braver man than me!

3

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dave atkinson | 13 years ago
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Quote:

I'm only 64kg (10 stones) so perhaps it is more of an issue for heavier riders but how do you get pinch punctures on tarmac?

normally from potholes or other imperfections you don't see; i've had plenty in my time and i'm one of those heavier riders, it's certainly more of an issue the heavier you get.

I run 25s minimum as a matter of course on all my bikes, i find them more comfortable and versatile and the weight difference is negligible for a 98kg rider like me. the difference in rolling resistance between the two is pretty negligible too.

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cat1commuter | 13 years ago
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I much prefer 25s. They roll better and with greater comfort over rough tarmac. You have to pump up narrower tyres harder to avoid pinch flats, which reduces the contact patch with the road, and hence available grip.

Most 25s I have tried are actually 23 mm wide. I have a pair of Schwalbe Ultremo 700x28, and they are 25 mm wide, a pair of Ultremo 700x25 which are 23 mm wide, and don't have any in 700x23!

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KirinChris | 13 years ago
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Very little difference between 25 and 23 AFAIK. To get a noticeable difference I think you'd need to go up to 28mm.

In fact I think I read somewhere that the rolling resistance on 25mm tyres is slightly less - just you have a bit more weight in rubber.

The only note I would add to Simon E's points above is that lower PSI increases the risk of pinch flats and picking up road debris. Maybe not at 80 but you can lose 10-20psi over the course of a week if you aren't checking them daily. I find it also adversely affects handling as well and prefer the feel over 100.

A trade off against the softer ride I guess so take your pick on that one.

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Simon E replied to KirinChris | 13 years ago
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abudhabiChris wrote:

lower PSI increases the risk of pinch flats and picking up road debris. Maybe not at 80 but you can lose 10-20psi over the course of a week if you aren't checking them daily. I find it also adversely affects handling as well and prefer the feel over 100.

I have done time trials and later found I only had 40 psi in the rear tyre yet I went about the same speed as normal. The only time I've had a pinch flat was hitting a pothole riding along an old railway trackbed. I'm only 64kg (10 stones) so perhaps it is more of an issue for heavier riders but how do you get pinch punctures on tarmac? 7

Losing 10-20 psi in a week means either a slow puncture or leaking valve, which needs to be sorted.

Found a graph and some awkward calculations at the bottom of this page on the CTC website. Advice from Michelin (PDFs) linked from this page.

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KirinChris replied to Simon E | 13 years ago
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@Simon E
On pinch flats... what Dave said. I've had them from raised cats eye things as well.

Losing 10-20psi per week does not mean a slow puncture. It's quite normal for racing tyres. Even more if using latex tubes.

The CTC website you linked to says "Remember that narrow tyres lose pressure quite rapidly and should be ‘topped up’ every few days."

The chart there also advises that a rider of your fairly light weight running 25mm tyres should maintain a MINIMUM pressure of at least 95psi (that's assuming you have a 7-8kg bike and no additional load). Heavier riders, which will be most people, should be at 100psi or above and higher for narrower tyres.

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Simon E | 13 years ago
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If you're happy with them don't worry.

23mm seems to be the most popular size but narrower is not necessarily better - see what Schwalbe say about tyre size, rolling resistance etc:

http://smtp.schwalbetires.com/tech_info/rolling_resistance

This and other tech info is also in a PDF at Schwalbe.co.uk

Since the larger tyres offer greater comfort I've used 25 and 28mm at a range of pressures and I've not found much to complain about, other than if you pump them up too hard (for me thats beyond 100 psi) then the ride quality deteriorates excessively. I've found for general riding about 80 psi is a good compromise.

I tried some lightweight 26x1" tyres on the commuter MTB but since going back to 1.5" City Jets @ 50-60 psi riding the local lanes to and from work has become more enjoyable.

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