New bike issue....Tyre clearance on Cervelo S3

awnow

Hi, I recently bought a new Cervelo S3. It came with 25c tyres on basic alloy Mavic wheels. I put on my own Prime RR-28 carbon rims and GP4000 25c tyres and I noticed after a couple of spins some wheel rub on the inside of one of the chain stays. (No problem with the front wheel.) I noticed there was very very little clearance between the tyres and the seat- post, seat-stays and chain-stays and there were actually some light scratches starting to appear on the back of the cut-out seat post where debris or grit had brushed past on the wheel.

I went back to the supplier who said there should be no issue with running 25c GP4000s on this frame and that perhaps it was down to my own wheels and that I could try running 23c tyres until I upgraded my carbon wheels to a better brand in the future.

I then carried out a few trials by trying different wheel and tire combinations on the bike. I even tried the 25c GP4000 tyre on the wheel that came with the bike but still no significant difference.

Anyone had any experience with this? I'm a bit disappointed having to consider going back to 23c tyres.

secman

I've a similar problem with a winter bike, a planet x pro carbon. The rear zonda with 25 conti GP4000 just will not clear frame whilst fully inflated, have to deflate it to get wheel back on, no rub when on and inflated. A set of Fulcrum 3 with Michelin 25's no issue getting it on. Height of side wall on conti's is causing my problem.

Alek

25mm GP4000SII are more like 27-28mm on most rims, aren't they?

awnow

Alek wrote: »

25mm GP4000SII are more like 27-28mm on most rims, aren't they?

Yes, that seems to be the case. On the wheel/tyre combinations I tried, the width measured 28mm to 28.5mm average.

awnow

I also contacted Cervelo directly with the query who said the max tyre/wheel volume the S3 frame could accommodate was 26mm!

I then provided them with the measurements I had taken using different wheels combinations and they agreed that i would have to go back to 23c tyres! A bit disappointing considering the bike was advertised as being compatible with 25c tyres. I wish they had said that some 25c tyres were not compatible e.g. Conti GP4000s!

monkeyslayer

The width of the rim could be a factor too, 28mm conti's are fine on my frame with my Zipps but not with my Zondas, has to be 25 max with them, the Zipps are pretty wide so the height is spread.

Alek

It's rather the case that Continental is mislabeling their tyres, Cervelo seems to be holding to their promises

awnow

monkeyslayer wrote: »

The width of the rim could be a factor too, 28mm conti's are fine on my frame with my Zipps but not with my Zondas, has to be 25 max with them, the Zipps are pretty wide so the height is spread.

The Cosmic alloy rims that came with the bike measure 23.5mm (outer dimensions) while my own Prime carbon rims actually measure wider at 25.4mm. The result with using the 25c GP4000 tyre on either wheel is a width of about 28.5mm....

awnow

Alek wrote: »

It's rather the case that Continental is mislabeling their tyres, Cervelo seems to be holding to their promises

There could be a bit of truth in that Alek. From my recent reading online, GP4000s are well known to be a more bulbous tyre, it is frustrating that the supplier/Cervelo agent who sold me the bike knew I was going to run 25c GP4000s on it and said they'd work fine.

C3PO

Alek wrote: »

25mm GP4000SII are more like 27-28mm on most rims, aren't they?

That would explain why the 28c GP4000s I put on the new bike look huge! ðŸ˜႒

irishrover99

GP4000’s 25mm on both my bikes are not the same width. One is on zondas which are about 27 mm and the other is on Aksiums and they are 25 mm.

Noticeably different overall volume and I’ve tried both wheels on the same bike.
Recently I switched the GP4000’s that I had on the aksiums to my zondas and it was still the same as before so it’s not down to wrong tire size.
Obviously something to do with the rim width/height.


https://fitwerx.com/how-bicycle-rim-width-effects-tire-width-and-contact-patch/

Lumen

monkeyslayer wrote: »

The width of the rim could be a factor too, 28mm conti's are fine on my frame with my Zipps but not with my Zondas, has to be 25 max with them, the Zipps are pretty wide so the height is spread.

That's an interesting point. Using wider rims won't result in more tyre volume despite the extra width, it just flattens the tyre.