VeloBrox

I've searched for days for an answer to this.

How big fenders and tires can one fit to a 1983 Trek 620 converted to 700c wheels? My dream is hammered VOs or Honjos and the fattest tires possible.

Best regards,

Johan

Amesja

28-32c should be quite attainable I think. More than that, maybe... The fenders shouldn't be the problem -there is plenty of room for them after the 700 swap. The width of the tires between the stays will be the issue I think before the diameter of the tires becomes a problem. Wider fenders are rarely a problem with a little bit of easy trimming at the stays.

JohnDThompson 

An '83 frame ought to have the seat stays attached to the sides of the seat lug, rather than the "fastback" style that appeared later with the cast seat lugs, so there should be plenty of fender clearance.

VeloBrox

So... should I go for 45 mm fenders and 32 mm tires?

Charles Wahl

I would wait until you have the frame, and then measure things. I like to fit wider tires and fenders, and what I've found is that on the front, it's obviously fork crown clearance (both height of crown over axle, and width between blades or crown tangs) that limits how large a tire will fit -- however on the rear it's generally not the brake bridge that's a problem, but the clearance between the chain stays near the BB. A lot of the old touring bikes weren't designed for particularly wide tires; it wasn't the fashion back in the 70s and 80s.

Also, you can fit more tire beneath plastic or composite fenders than beneath metal ones. The metal ones wrap under, and require greater width (overhang) for the same width tire, and a bit more height (clearance) too.

Finally, the wider the bead seat on your rims (wider extrusion), the lower profile (wheel diameter) and greater actual width tires of a given "width" will deliver.

The Golden Boy 

Did you buy that frame?

Orrery

It might depend partially on what brakes you use. On the '83 620 I used to own (~21''/54cm) I used the long reach Tektro's with 28mm tires and 35mm fenders (SKS) and it was a bit tight, if I recall correctly. It was a really nice bike!

Road Fan

I know (have done it) that one can run 700x32c tires on that frame, but not with plastic (SKS or the older Zefal fenders). So there should be no issue with 650x32b tires.

You can actualy make some pretty useful measurements, if you like, then make your own decision. 32 mm tires need an internal chainstay/fork/seatstay clearance of around 44 to 48 mm to allow for rim wobble due to road riding occurrences (bumps, potholes, and other sources of rim damage while on a tour) and possible spoke breakage. Take a ruler and find the position along the chainstays (probably the narrowest point) where the width between the chainstays is 48 mm. Perfect precision is not necessary. Mark it and measure the distance from that point to where your rear axle center would be. If that distance is greater than 584/2 + 32/2 = 292 + 16 = 308 mm. For a 32 mm tire in 650b that would be the lateral clearance criterion.

The fender needs to be about 8 mm wider than the tire on each side for really good rain coverage, so for 32 mm tires that's again 48 mm. This width is needed at some point farther "up" the chainstay and seatstay than the 308 mm criterion, but not higher up than the radius of the tire/wheel (estimated 292+32 = 330 mm).

If you make some measurements and post the numbers here, I can help you interpret them. Some other numbers needed are the distance from the axle to the inner edge of the chainstay bridge and similarly for seatstay bridge and the fork crown. There should be about 18 mm minimum clearance from these bridges to the tire in order to be able to install plastic 45 mm fenders and have good (10 mm) tire - fender clearance.

At some point it would be good to find a 650x32b mounted to a wheel and inflated, and measure the actual wheel radius and the radius to the widest point. My numbers are estimates, not actuals.

VeloBrox

Orrery:

I'm going to put my old Dia Compe 610's to use, don't think they will be the limiting factor.

Road Fan:

Great info, thanks! Not going the 650b route, however. Getting new 700c's built with pretty wide rims (Mavic A-319). I need fenders and prefer 700x32c tires.

Road Fan

I was not successful at fitting 700x32c with 45 mm zefal plastic fenders on either a 1983 620 or a 1984 610. There just wasn't enough room between the tire and the fender. I could not prevent interference between the two, on the back wheel.

I was able to run 700x32's without fenders on either of those frames.

All these attempts were with Sun CR18 rims, the next step wider than a racing rim such as a Mavic Open Pro.

jr59

28 with fenders is all I could fit!

32-35 tires w/o.

VeloBrox

Anybody try SKS P45 fenders? Seems weird to me that a 45 mm fender shouldn't accomodate 32s on a 700c wheel.

VeloBrox

All right, I give up. Going for Panaracer White Paselas in 28c and SKS P45s. Thanks for helping me out!