verktyg 

I picked up this all original 1967 Peugeot PX10 barn bike at the end of 2007. It came with the original sewup wheels plus a set of 27" wheels with 27" x 1" clinchers. It sat that way for a number of years before I got around to riding it.



The original 27" x 1" clinchers were shot. Silly me, I went out and bought a set of 27" x 1 1/4" tires, the kind of setup we did in the early 70's when someone wanted to switch their bike from sewups to clincher wheels.

Even deflated, the rear wheel wouldn't fit between the dropouts and seat tube much less clear the brake bridge. Same problem in the front.

I was able to barely fit 27" x 1 1/8" tires on the bike and rode it for a while before it went back into storage. When I dragged it out and cleaned it up last year it turned out to be a decent riding bike.



I've since switched to a set of 700c wheels with 25mm tires. Problem solved!

From the mid 70's on after the introduction of Mavic Module E rims and 27" x 3/4" or 700 x 20c tires there has been a tendency for bike manufacturers to reduce the frame clearance on performance oriented bikes especially ones that would NEVER see fenders.

... But it didn't start there. Most of my "racing bikes" going back to the 1960's have low tire clearance.

On my early 60's Paragon frame built for sewups, 23mm tires are a close fit in the rear and 25mm ones will just squeak by.



verktyg

Chombi1 

You have to consider that the frame was designed in a time when race bikes were typically using tires at 23mm section or less. Really no surprise that the ginormous 32mms will not fit under the brake bridge and fork crown.

niliraga 

have bumped into this kinda thing before and I've considered some sort of spacer/shim washer that forces the front axle to sit 2-3mm lower in the dropouts. if you took great care to ensure QR or nuts were still firmly clamping onto the dropouts, why wouldnt this work? i'm assuming that effective changes to geometry etc. would be as negligible as running a different tire size...?

Wildwood 

Some frames don't fit 650b without contortions.
I would agree that this is one of those.
Wise choice.

seedsbelize 

It's the rare bike, in my collection, on which I can mount the rear wheel without deflating.

jadocs

I’m running 25mm Schwalbe One TLE’s that measure out to 27mm on my 1992 frame. That’s the largest I can go in the rear. Any bigger and it will rub the brake bridge. I have more room up front than the rear.

verktyg 

Looking back over this thread, I remembered a trick I've used over the years to solve rear wheel fit on some bikes with tight rear triangles.

The rear triangle on my 1983 Colnago Super is so tight that I had to deflate any tire over 22mm to get a wheel to fit into the dropouts. Since the frame wasn't pristine, I built it up as a frankenbike with a mishmash of parts I had on hand.



I was running 700x25c Paselas. I modified the dropouts slightly by filing back the leading edges about 3mm (1/8"). After dressing them up the modification isn't visible. Now the rear wheel goes in and out smoothly.



verktyg

Lemond1985

Another trick, for increasing rear wheel clearance, is to turn the brake calipers around. Depending on the angle that the hole in the brake bridge is drilled, I have found I can gain a couple mm's on some frames. I love my 28's on 80's frames, what can i say?