Size of 23c Continental GP4000s

Nairnster

Are these really that much bigger than other 23c tyres?

I bought a pair as I previously ran 25c Rubino Pros, but Ribble told me 25c tyres wouldnt fit their 7005 Sportive frame.
Once fitted however, the rear tyre rubs on the front derailleur clamp.

The tyre has been reseated several times by myself, and the LBS. A different tube has been tried and it still rubs. I have even moved the clamp right down, and then the mech right up on it, to give as much clearance as possible, and it still rubs.

Does anyone who has switched to or from these tyres in this size, have any input as to whether they do actually run large?

I cant afford to throw money at trying loads of different tyres, but have ordered a 23c Rubino to try.

Is it possible the frame is out of manufacturing tolerances so much that a 23c tyre doesnt fit?

markhewitt1978

I haven't measured them but my 23c GP4000S do appear subjectively bigger than other people running 23c and seem bigger than the 23c GP 4 Seasons I have on now.

Indeed with my raceblade longs it looked like the GP4000S were rubbing on the top whereas with the GP4 Season there's plenty clearance.

bobones

My 23mm GP4000s are close to 25mm and are actually larger than my 24mm GP24s.

Nairnster

Fantastic, thanks for the help gents.

Hopefully there will be no issues with the Rubino then. The Contis will probably make a nice cheap Christmas pressie for someone then

duckson

GP4000S 23c on my wifes bike appear larger than the 25c Vittoria Open Pave i have on my best bike and are definately larger than the 23c Vredestein Fortezza Quattro Trimcomp i have on my winter bike.

Nairnster

Well fingers crossed the problem will be solved tomorrow then.

Am considering a lower profile front mech band as well just to increase clearance a little.

Nairnster

Well, fitted the 23c Rubino Pro on the rear, and I now have clearance.

Its amzing how much taller the Conti tyre was.

My next question is, given how long a front tyre may last, should I keep the Contis and run them as fronts, and just replace the rear when it needs it, or change to a matching front tyre and get rid of the Contis?

Is there any disadvantage to running a fatter front tyre?

binkybike

I wouldn't have thought it's much difference, I've run mismatched tires many times (not that combination though) and I haven't ever noticed and problems, although they might have different grip levels, I've never noticed it..

Grill

They are actually 23.8 and are identical to the old GP4000S 24c. They simply changed the packaging/branding to 23c for marketing purposes. This was confirmed in an interview with a Conti rep that I read a few months ago.

markhewitt1978

Thanks, interesting to know!

Do you know what the real size of the 25s is?

Grill

IIRC they're 25.8, but I can't find the article to confirm (may have been in an old issue of Cyclist).

Moonbiker

Seems crazy that bikes won't take 23c tyres even if they are abit oversized 23c tyres :x


With condition of roads covered in farm slurry/muck here atm 28c would be nice on my road bike if they fitted

Nairnster

Isnt it just!

Have had the frame for coming on 3 weeks, and havent even been able to get out for a test ride yet, becasue now we have snow!

caadybrompton

I put 25c GP4000s's on for the winter and am having the same problem with my back wheel. When pumped up to 110psi it rubs ever so slightly on the back brake nut in between frame and calliper on my Caad10. Very annoying. Might have to go back to 23c's as the reduced pressure to make it clear the nut seems too low.

Nairnster

IT wasnt even 25c that were rubbing on mine lol

caadybrompton

Nairnster wrote:

IT wasnt even 25c that were rubbing on mine lol

lolz! forget about it then with Gp4000 25c's , no chance.