Fitting larger profile tyres to road bike - seatpost clearance

retrovet

Retro Newbie
As seems to be the trend at the moment I decided to try some larger profile tyres on my road bike. The bike is a Peugeot Competition Circa 1997/8 (I never managed to fully identify the exact model), which I stripped down, had the chainstays (which were rusted through) replaced, and then repainted and rebuilt. My question is regarding tyre clearance at the seatpost (frontmost part of rear tyre). Clearance everywhere else is fine, but at the seatpost it is possibly 3mm at most. Is this too little or, as there is a gap albeit small then it's acceptable/safe?

The bike was quite a harsh ride on 23mm tyres so my old arthritic joints were looking forward to the 28mm balloons.
 

jim haseltine

Old School Hero
That's pretty much a 'fag paper' clearance as was popular back in the days when I was testing. You don't need to pick up much grit for that gap to disappear. I had a Falcon track frame set up for fixed wheel events (shortest possible drop Weinmann side pull mounted behind the fork crown was the only brake I could fit - very aero though) which had a similar gap between the tread and the bottom of crown - after a couple of events there was no paint left there.
 

retrovet

Retro Newbie
Thanks Jim. I had considered putting some clear frame protector tape on the back of the seat tube to see if it marked up after a ride or two. Probably best to try that and if there is too much rubbing then switch to 25mm tyres instead.
 

foz

Gold Trader
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If the tyre's not rubbing then there's no problem, but if you value your paint then I'd go with a thinner tyre, or stick to the track!
 

retrovet

Retro Newbie
Thanks Foz, just as a thought and I know this is not going to be aesthetically pleasing, is there anything inherently wrong in fitting a 28mm tyre at the front and a 25mm at the rear? So at least if I have to ditch the rear 28mm if it causes paint damage then I retain some softness at the front. Or is this really stupid thinking ...
 

rikster

Retro Guru
Just wondering if the new chainstays are a little shorter than the originals which would account for the close clearance? I think tyre profile can differ from one brand to another, as I've found some tyres can sit a little higher than others.
 

mattr

Old School Grand Master
Current road bike has ~3mm under the crown, I've had no issues with that other than a few scratches in the paint.
All long as you're not planning to ride crappy roads covered in mud.
 

retrovet

Retro Newbie
Yes, I was wondering if the chainstays could be fractionally shorter, and I am a fairweather cyclist these days!
 
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