Questions about purchasing bicycles and parts
So - I'm currently on 25C rubinos/contis, but am in the process of buying a frame that really has a really tight clearance on 23Cs - I suspect I know the answer already, but is there a discernible difference in ride quality (hardness) between a 25C and these options? Commuting 25km daily, primarily bike paths.
I read the same thing, so I run 35s
Thanks guys - I already run 25s for that exact reason.
However, given I have next to no clearance for 23s on the new frame, discussion on the rolling resistance or otherwise of 25s seems largely irrelevant, don't you think?
Yes, I did, as well as indicating that I'm currently on 25s (and thus, most likely aware of their particular ride qualities).
I also asked specifically about the ride quality of 20C through 22C tyres - right there in the title.
Did the english article mention any of the smaller diameter tyres by any chance? Id be interested to read if so.
No, they explained why a bigger tyre will have less rolling resistance and more comfort than a smaller tyre at the same pressure though there must be some upper limit and they did not go bigger than 25s. I raised this as most common belief is that the thinner the tyre, the less rolling resistance.
Bigger tyres roll faster (for the same pressure) but IMHO (all things being equal) they are slower. This is due to aero and power transfer losses (thicker casing, more bob at lower pressure). However this assumes a smooth surface. As the surface gets rougher, bigger tyres (at lower pressure) get faster due to the reduction of shock/bounce. Probably why you won't see too many CX tyres in XC MTB races (where there are no tyre restrictions to my knowledge).
See the "TYRE PRESSURE" section in the link below for a better explanation.
http://www.slowtwitch.com/Tech/What_s_i ... _1034.html
Good article thanks.
What you are saying about narrower being faster appears to be supported by what is being raced on. The larger 25c tyres only seem to be used where the road is rough eg Paris-Roubaix.
You don't see 25c used in tts to my knowledge, where every time gain possible is sought.
Can't fit a 25 in the rear of my S5, a 23 is already a close fit.
That may be a bit out of date - in the Giro, my info is that Greenedge used 25mm Conti Competition, Rabobank 25mm Vittorias and Sky 24mm Veloflex which actually measure 24.9mm. Rims are also going wider - Zipps Firecrest 23.48mm up from 21mm, Hed and Bontrager going to 27mm, Mavic 24.2mm and Shimanos latest (used by Sky) are also up in size. A 23mm on these rims will be no more aero than a 25mm. All above courtesy of Cycling Plus.
The wider tyre does not mean a thicker casing and the point is that at the same pressure "bob"will be less on a wider tyre as there is a bigger volume of air to support the weight. A narrow tyre has more deformation at the same pressure and therefore greater rolling resistance.
What part of the logic is out of date?
I've been riding on wider touring rims for years. I use 23mm tyres but they measure 24.8mm when used with these rims.
True, but once over 28mm, it usually does as the target market is different.
True. Obviously tried to simplify too much. What I overlooked writing was for the ideal pressure for each tyre, a bigger tyre should have more bob. Of course at the same pressure the bigger tyre is going to be harder, but then either the bigger is over-inflated or the smaller is under-inflated.
True, but I just can't get my 2.35" Big Apples to go faster than my 23mm Rubino Pros.
Last edited by Nobody on Fri Sep 28, 2012 2:45 pm, edited 1 time in total.
Well, since it's trashed anyway...
Thanks for the reply. Not being able to fit a 25 into a new S5 says a lot. If Cervelo really thought 25s were actually faster for road racing, I'm sure they would allow the space. You would think that Schwalbe would know something about tyres. They think narrow tyres are faster too.
http://www.schwalbetires.com/tech_info/ ... nce#narrow
It's funny me arguing this point as it was only a couple of years ago that I'd be arguing the opposite. I've had more time to read, think and experiment since then.
Last edited by Nobody on Fri Sep 28, 2012 7:46 pm, edited 1 time in total.
What is being raced on at the top level doesn't really translate to the general population... as they are all very light ( very few riders over 75kgs ) so can use the optimum tyre pressures for their weight * & they are all riding on tubular tyres which have better rolling resistance ( although running a latex tube will greatly reduce your clinchers rolling resistance ).
* Part of the advantage for bigger riders running 25's is they run lower pressures compared to what you run in 23's.
Personally I run 150 psi in front 19mm tubular, 160 psi in rear 22mm tubular on my tt bike ( much more weight over the front wheel on a tt bike ). 100-115 psi in my 23mm front clincher & 100 psi in the 25mm rear on the road bike ( 120 psi on the rear with a 23mm ). 28psi on the front 32mm & 32 psi rear on my cyclocross clinchers... would love to run much lower but need tubulars for that.
Horses for courses.
160-180 in my 22mm tubulars on my tt bike. No idea if that is faster than a lower pressure. I tend to wonder why they build such high pressure capability into the tyres if lower is faster though.
Was that on the rougher stages, and is that the measured width or specified width of the tyre?
It's similar to the theory that clinchers are as fast as tubulars. Most of the photos of the bikes in the peleton that I see show tubulars.
I'll also reiterate my point about tt tyre widths. When I see them running 25 - 28 mm tyres on tt bikes I'll accept they are as fast.
How much what?... It will be more comfortable as you will run lower pressures in the 25mm compared to the 22mm( so it will soak up more bumps )...apart from that you won't notice any difference in speed and handling. I prefer just a 25 on the rear.
If you run a latex tube in them they are even better.
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