27" to 700c tire size...
 

Alright, knowing that I'm losing 8mm on the diameter of the wheel, I'm looking for predictions on available tire size. I've got a '90 Fuji Palisade that, with 27" tires was originally spec'd with 28c width tires, and can't go any larger than 32c (27X1-1/4) without rubbing something. Even with the 32's, it's a feat to get fenders in there without rubbing. I'd like to go with 700c wheels and tires for a wider tire and more fender clearance, but do you think that 38's would work? I'm only going up 6mm at most (and more likely 4-5, given that these tires are a bit narrower than 38c)...whaddaya think? I've already got new brakes that will handle it, and was wondering what the general consensus is on swapping them before actually doing it.

Tire's diameter can vary, even from the same mfr. The only way you'll know for sure is to buy the tire and mount it on the bike.

I doubt you'll be able to fit 38mm tires on an older road frame, it all depends on your chainstay width. Measure the width of the chainstays with the existing 27" wheels at the point where the wheels passes by the chainstays. You'll need at least 3mm per side, 38mm tires will be closer to 35mm on road rims with a 25mm outside dimension (like Mavic a319 etc).

I have given up on 38mm tires on an older frame, even when I mash the stays to fit wider tires, the tire is too tall and I need to let the air out of the tire to install the wheel in the dropouts. Now I run 35mm tires, no need the "clearence" the frame, still have to let some air out of the tire to install the wheel in the frame.

+1 I doubt it as well. But width clearance is all about stay spacing, and fork spacing (and also brake caliper clearance/spacing). Borrow a wheel/tire combo from another bike/friend/etc.

Dollars to doughnuts 38mm tires aren't going to fit. For reference, I have run 700c wheels with Panaracer Jack Brown tires (33mm) on my '81 Schwinn Voyageur. They were SUPER comfy, but I had to abandon them for the Ruffy Tuffys (27mm) to use fenders.

I doubt you'll have room for fenders wider than 45mm, which barely gives you proper clearance on 38mm tires anyhow. That said, with a Dremel tool you can modify aluminum fenders to your heart's content.

You never know for sure until you try, but I imagine your best scenario is 43-45mm fenders with 700c wheels and 28-32mm tires.

If 700 x 38 won't fit, it might be possible to fit 650B x 38 on an older frame and still have fender clearance. There are certain critical meaurements to be considered: Brake reach, bottom bracket drop , and fork and stay spacing. The Rivendell site, www.rivbike.com has instructions for converting to 650B.

I converted an old Univega and the Col de la Vie tires are very comfortable on the lousy roads around here.

I don't know about the fenders I think on a Palisades a 700x38 tire should fit, but as thrifty bill points out the brake reach will be the critical issue.

as the others said find a set of wheels to try it.

Not all 38mm tires are equal in width -- a "narrow" 38 just might fit. My Bianchi can handle only up to 700Cx25, but the callout size on my Continentals is 700Cx28. There is no way I could put 700Cx28 Specialized tires on it.