In Praise of 25's.

Duffer65

Just wanted to say that since switching to 700 x 25 tyres my ride comfort has increased, my cornering has improved, women want me and men want to be me, I have been promoted at work - as a result I work less hours and have a higher salary, my children think I'm a God and I have found a cure for all known diseases...thought you'd like to know .

apreading

Dont try 28s then - might be too much for you to handle!

declan1

I think I might make them my next upgrade then!!!

Grill

Yes but how do you feel about the other roadies who point and laugh at your fat tyres? :P

25's for the winter bike to be sure (we all put on weight in the colder months!)

notlongnow

Ive got 23's and 25's dont mind either but prefer 25's :?

rolf_f

Grill wrote:

Yes but how do you feel about the other roadies who point and laugh at your fat tyres? :P

Your lower rolling resistance on the 25s will mean that you can't hear the laughter as it will be behind you!

Grill

Rolf F wrote:

Grill wrote:

Yes but how do you feel about the other roadies who point and laugh at your fat tyres? :P

Your higher rolling resistance on the 25s will mean that you can't hear the laughter as it will be behind you!

Fixed. :P

declan1

Grill wrote:

Rolf F wrote:

Grill wrote:

Yes but how do you feel about the other roadies who point and laugh at your fat tyres? :P

Your LOWER rolling resistance on the 25s will mean that you can't hear the laughter as it will be behind you!

Fixed. :P

Double fixed

rolf_f

Grill wrote:

Rolf F wrote:

Grill wrote:

Yes but how do you feel about the other roadies who point and laugh at your fat tyres? :P

Your higher rolling resistance on the 25s will mean that you can't hear the laughter as it will be behind you!

Fixed. :P

Oh dear

Duffer65

Grill wrote:

Yes but how do you feel about the other roadies who point and laugh at your fat tyres? :P

25's for the winter bike to be sure (we all put on weight in the colder months!)

I don't notice the laughter as I'm in such a rapturous state as I roll comfortably along .

Grill

declan1 wrote:

Grill wrote:

Rolf F wrote:

Grill wrote:

Yes but how do you feel about the other roadies who point and laugh at your fat tyres? :P

Your LOWER rolling resistance on the 25s will mean that you can't hear the laughter as it will be behind you!

Fixed. :P

Double fixed

Seriously, now I'm confused. How does a greater contact patch LOWER rolling resistance? More surface area = more friction... :?

declan1

Grill wrote:

declan1 wrote:

Grill wrote:

Rolf F wrote:

Grill wrote:

Yes but how do you feel about the other roadies who point and laugh at your fat tyres? :P

Your LOWER rolling resistance on the 25s will mean that you can't hear the laughter as it will be behind you!

Fixed. :P

Double fixed

Seriously, now I'm confused. How does a greater contact patch LOWER rolling resistance? More surface area = more friction... :?

25mm tyres don't deform as much as 23mm ones, therefore the actual amount of tyre in contact with the ground is less.

rolf_f

Grill wrote:

Seriously, now I'm confused. How does a greater contact patch LOWER rolling resistance? More surface area = more friction... :?

The contact area is defined by tyre pressure and the load upon the tyre (which is constant) - not carcass size. So, for a given pressure (and of course, this is where results may vary), the contact area is the same size - what differs is its shape. As the contact area on a wider tyre is wider than that of a narrow tyre, in order for the contact areas to be the same size, the wider tyre has a shorter contact area in the direction of movement. It is the length of the contact area in the direction of movement that determines rolling resistance rather than width.

Of course, if you run your wider tyre at a lower pressure, then it's rolling resistance will be higher. I just default to 100psi all the time as I can remember that number!

Grill

I see, thanks for the explanation. As I'm quite light running at 115psi I'll stick to 23s to shave a few grams!

napoleond

But the extra air at 115 psi will mean that they weigh the same as 25s at 100...

Grill

Latex tube + Nitrogen? :P

How come pros don't use 25s if there so much better? Surely the added width would be less reactive on corners.

rolf_f

Grill wrote:

Latex tube + Nitrogen? :P

How come pros don't use 25s if there so much better? Surely the added width would be less reactive on corners.

Often not helpful comparing us with the pros. They are faster so aero comes in and they are generally riding on high quality road surfaces. Move to those races where they aren't (eg Paris Roubaix) and riders might go as wide as 27.

Grill

Aero! That's what I meant!

Good point though, same reason they use more compliant frames on the cobbles.

Duffer65

I also run my tyres at around 100 psi. My bike is alu and possibly not one of the best frames (carbon fork) and the ride can be a bit jarring at times on the shoddy roads of SW London. I don't pretend to be au fait with the science behind it, but I have noticed a positive change in ride quality since I've switched to 25s.

Duffer65

Grill wrote:

Latex tube + Nitrogen? :P

How come pros don't use 25s if there so much better? Surely the added width would be less reactive on corners.

Although not the reason I switched, but it seems some Pros are using 25s now.


http://velonews.competitor.com/2012/05/ ... ire_218011

declan1

My dad's awesome old Peugeot Racer (from the 80's we think) has 28mm tyres and a steel frame. I have never ridden a road bike that is as comfortable as the Peugeot is. The tyres have a max pressure of 70PSi, and it's such a comfy bike!!!

springtide9

In addition, the ideal width of tyre will depend on the road surface.

I have 24mm and 23mm at the moment... but will try 25mm's next. The 23mm are faster on the smooth, but you get more scrubs off (through vibration) with the 23mm on most of the roads around here compared to 24mm's.

drlodge

25mm tyres will be more comfy than 23mm as there is a bit more contact area, and hence you run a slightly lower pressure, and hence a little bit more power loss. If you compare 23c and 25c tyres at the at the same pressure, then 25c might have lower rolling resistance but then either (a) the 25c are over inflated or (b) the 23c tyres are under inflated.

All things being equal (including inflation to the appropriate level) 23c will have lower rolling resistance, and 25c will be more comfy. Its a trade off between efficiency and comfort.

Grill

Duffer65 wrote:

Grill wrote:

Latex tube + Nitrogen? :P

How come pros don't use 25s if there so much better? Surely the added width would be less reactive on corners.

Although not the reason I switched, but it seems some Pros are using 25s now.


http://velonews.competitor.com/2012/05/ ... ire_218011

Certainly makes sense on the wheels they're using (24mm+).

Raffles

25`s all the way for me, would never go back to 23`s as crummy uk road surfaces and that size tyre are just so uncomfortable.

hulla the hulla

I too find 25's more comfy but as they are on my old / now winter rims which are heavier I find the extra effort required to push the bike along puts me off using them, it sometimes feels like I'm riding trough treacle !
My summer wheels which are a good 700gms lighter have 23's and lighter tubes and feel much faster, leading to a more enjoyable, less taxing, albeit probably more bumpy ride so it's difficult to tell which is best.....

Can't do 28's as frame clearance won't allow

Monty Dog

drlodge wrote:

All things being equal (including inflation to the appropriate level) 23c will have lower rolling resistance, and 25c will be more comfy. Its a trade off between efficiency and comfort.

Wrong again!
There's a Wikipedia article on rolling resistance if you want to understand the science - it's both down to the size/pressure of the contact patch and energy losses due to the flexing of the tyre carcass. Tyre pressure becomes immaterial after about 5 bar because the determinant factor is the roughness of the road surface.

As for pros using 25mm tyres, the latest carbon rims are optimized for use with a wider tyre so expect to see a lot more. 28mm tyres are very popular for racing the Northern Classics, just that lots of diehards refuse to believe the benefits of running wider tyres.

de_sisti

Rolf F wrote:

Grill wrote:

Latex tube + Nitrogen? :P

How come pros don't use 25s if there so much better?

Often not helpful comparing us with the pros. They are faster so aero comes in and they are generally riding on high quality road surfaces.

I didn't realise pros raced on roads that the general public weren't allowed to cycle on. :shock:

rolf_f

De Sisti wrote:

Rolf F wrote:

Grill wrote:

Latex tube + Nitrogen? :P

How come pros don't use 25s if there so much better?

Often not helpful comparing us with the pros. They are faster so aero comes in and they are generally riding on high quality road surfaces.

I didn't realise pros raced on roads that the general public weren't allowed to cycle on. :shock:

The road surfaces in Europe tend to be better than here (probably because here there is a lot of freeze thaw action over winter - in Europe there is probably much less due to the more consistently cold winters) and also poor surfaces on the Grand Tours tend to be re surfaced in advance of the race. Todays Vuelta stage features several kilometres of road that were metalled for the first time for the race.

de_sisti

I stand corrected.

nickel

Just stuck some 25s on my Alu bike, but only because they were cheaper than a set of 23s. Can't say I can notice much difference but psychologically they give me more confidence descending, especially in the wet.