thorn brevet 2003 brakes & nominal tyre clearances??

[Lord Grelevel]

hi everyone,
   i hv a brevet 2003it's a gorgeous frame, the brakes originally fitted are shimano deep drop calipers & the tyres are pasela 32s (which look much smaller). because the tyres are old i'm fitting marathon 28s.

but if i wish to use the bike for minimalist camping it wd need heavier rubber than these, so i'm considering the option of changing the brakes for some tektro 559s or other brake. sjs say that these will  allow a 35.
however are all 35s equal, is a panaracer 35 really the same as a marathon?
and even if the tyres fit, will the frame clearances allow it (i think it looks likely).
also is it possible to use a centrepull long drop brake like the dia comptes rather than the dual pivots on one of these frames?

any advice & answers much appreciated!

[PH]

It's a can of worms!  Not all tyre sizes are what they say, even sometimes the same brands and occasionally even sometimes the same models, then of course they measure differently on different rims and that's before we discuss what people consider acceptable mudguard clearance.  Panaracer used to be notorious for being undersized, but they corrected that some years ago.
My favorite narrower touring tyre for deep drop brakes is the Marathon Racer, they come up a bit small so the 35mm would probably be OK where some 35's wouldn't. 
Good luck

 

[RonS]

however are all 35s equal, is a panaracer 35 really the same as a marathon?
and even if the tyres fit, will the frame clearances allow it (i think it looks likely).

Before ISO standards, tire sizing was a free for all. My wife’s bike from the heyday of false advertising had a set of Specialized tires marked 700-35 that measured 25mm. That’s how they could be “the lightest 35mm tire on the market”!

Thanks to the ISO it’s a little easier to pick a tire nowadays. Jan Heine of Rene Herse Bicycles wrote a good article on tire sizing. I’ll try to condense it to answer your question.
ISO requirements allow a minus tolerance, but not a plus tolerance, and here’s why.

A normal cyclist like you or me want the most bang (width) for the buck. 35s that are really 38s? Great! Imagine now that you’re the designer at Trek or Giant. You’ve just designed a bike that takes 35mm tires “max”, and you’re going to make 10,000 of them. Panaracer now sends you 20,000 38mm “35s” that don’t fit. You’re upset, and Panaracer have egg on their face. And they would lose their ISO certification.

This is an oversimplification, but I hope it conveys the idea.

So, to answer the question, not all 35s will be the same, but none will be over 35, so if SJS/Thorn say you can fit 35s, any tire with ISO size 35-622 will fit.

Hope this helps

[mickeg]

...
Thanks to the ISO it’s a little easier to pick a tire nowadays. Jan Heine of Rene Herse Bicycles wrote a good article on tire sizing. I’ll try to condense it to answer your question.
ISO requirements allow a minus tolerance, but not a plus tolerance, and here’s why.

A normal cyclist like you or me want the most bang (width) for the buck. 35s that are really 38s? Great! Imagine now that you’re the designer at Trek or Giant. You’ve just designed a bike that takes 35mm tires “max”, and you’re going to make 10,000 of them. Panaracer now sends you 20,000 38mm “35s” that don’t fit. You’re upset, and Panaracer have egg on their face. And they would lose their ISO certification.

This is an oversimplification, but I hope it conveys the idea.

So, to answer the question, not all 35s will be the same, but none will be over 35, so if SJS/Thorn say you can fit 35s, any tire with ISO size 35-622 will fit.

Hope this helps

Thank you, I learned something here.

But, I should point out that if extra wide rims are used, I would not be surprised if a tire grows an extra mm or two.