jkretsch

Crashed my Fuji road bike last weekend and had to replace the fork. Bought an Alpha Q CS-20 off of eBay. Nice fork, looks nice on the bike and fits great EXCEPT that the bridge is significantly lower than the original Fuji fork and now my 28c tires are rubbing on the underside of the fork. I have another set of wheels with 25c tires and they fit fine but I'd like to have the extra width of the 28s. Any recommendations for a low-profile 28c road tire or a 25c that runs a little wider? Thanks.

CliffordK

Bicycle tires are essentially a balloon with the shape determined by the rim and tire size (plus a bit of tread glued on top).

This is unlike car tires that are designed to be wide and flat.

One option you might have is to try different rim sizes.

A 23 to 25mm wide rim might maximize the height of the tire.

A narrow rim (19mm?) might be a low spot in the height of the tire, as well as a very wide rim (30mm?)

If I was you, and you wish to keep your new fork, then just go with a 25mm or 26mm tire.

Oh, here is an older diagram.


There is lots of data on there. Note, not all 23/25 tires are the same. So, you could look for a tire that runs small... but that might be similar to hunting for an acceptable 25/26 tire.

But, follow the 25mm GP4000.

It is shortest on the narrowest rim, and tallest on the widest rim.

dan911

Veloflex tires are pretty smalls "for there size" . I just have install my 25mm Veloflex Master and is 2mm less than my previous tire (Vittoria Corsa 25mm) on the same rim (Ardennes +) .

Lemond1985

If you don't mind voiding the warranty on your new forks, you could grind off the "lawyer lips" from the fork tips, then mount the wheel about 1/8" lower in the fork. Quick release skewer should bite in securely if you clamp it down nice and tight. This should give you enough room to clear a 28mm tire.

Or a slightly narrower rim might work.

CliffordK

I wouldn't do that. Inevitably with a few road bumps, the axle will settle back to the dropouts, perhaps tilting enough to induce brake rub.

If you're only slightly large, it would probably just cause tires to rub. Go really big, and perhaps do a hard brake and ender.

One would at least scratch up the bottom of the brakes or fork crown.

If it was a steel crown, I'd suggest potentially reshaping parts of the bottom of the crown to give a touch more space, keeping away from welds and joints.

Possibly one could contour a carbon fiber fork with an aluminum crown, but it probably wouldn't be a good idea to recontour a carbon fork with a carbon crown (which I think the OP has).

Tire sizes aren't exact, and somewhere there was a list of actual measured tire sizes, but I'd probably just find a 25mm or 26mm tire that you liked.

Or, hunt down a new fork. Perhaps a cyclocross fork?

Aubergine 

superdex

just buy 1 25mm tire and move on (leave the 28 you have on the back)

jkretsch

I ended up buying a Schwalbe Lugano 700x28 tire and it measures 26mm actual width on my Ksyrium wheel. Fits perfectly in the new fork.

McBTC

Pretty much what I've got going except on the rear, which won't accept 28s-- but, the 25 is pretty close to a 27.

JohnJ80

Carbonfiberboy 

The drawing is D validity. It's very easy to measure (and see) that the carcase sizes (unmounted width, as drawn but obviously not in reality) are very different for the 25mm mounted on the wide and narrow rims. Plus the much larger carcase is supposedly shown at a much lower pressure then the smaller carcase. I don't know why people keep posting this drawing. Print it out and step it off with a divider if you doubt your eyes.

Simple solution for the OP is smaller tire or different brand.

McBTC

True, true... that a 23 and a 25 have the same height on a 19mm rim (even the same pressure) is easy to see and obviously erroneous.

fietsbob

Spread out on a wide rim does lower tire profile ..

Not Road .. But my Studded tires are a D cross profile because I mounted them on rather wide rims

bbattle

Sounds like an excellent reason to buy a new bike!

jkretsch

Originally saw the post about grinding off the lawyer lips and mounting the wheel lower down in the dropout slots and brushed it off as craziness ... then I got to thinking about and all I needed was an additional millimeter or two of clearance. So I cleaned up the dropouts, turned the bike upside down, and put some epoxy in each of the dropout slots. I let it dry and then filed it down so it was even on both sides, filling in about 2 millimeters of the dropout slot. I put my big, fat 28c tire in there and clamped it down and wah lah!! Perfect!! Plenty of clearance now/ I filed down the epoxy so as to give just enough clearance that the quick release still fits without having to file off the lawyer lips.

McBTC

Genius idea... I've thought about ways to do that as well as just a 'lil bit of room is all I'd need on the rear to run a 28 and still fall within the range of the brake calipers. Definitely a market for a precision part-- i.e., a crescent-shaped spacer that would take 1-2mm out of the dropouts.