Front tire clearance
 

I came across this early 70s Windsor and it's super cool, fits me perfectly, and the frame takes wide tires (~35mm). The rear tire clearance is fine but the front just barely rubs the caliper. I really want to use these tires but I can't think of any way to gain some clearance. I don't think filing the caliper is the way to go. Anyone have any brilliant ideas?

https://cimg7.ibsrv.net/gimg/bikefor...92b1f2b03b.jpg
Cross posted in Mechanics section too.

Drum brake hub.

If you don't change anything, I would expect the knobs on that tire to pick up sand and small rocks and file away at your caliper anyway.

I bet it makes "Zzt! Zzt!" sounds when you ride out of the saddle. ;)

1. Install a drop bolt, upside down.
2. Make crescent shaped spacers for the dropouts.
3. Decrease the rake in the fork
4. Search out some of the old, clamp-on cantilever bosses.
5. Install a 27" fork
6. convert to drum brakes per JDT

Not everyone will consider a new fork, but it is a viable solution. I installed a semi-custom lugged fork on my Cyclocross bike. I wanted a crown mounted hanger for the brake cable and the original fork was insufficiently stiff.

I have a threaded fork from a 1978ish Trek 900, it's build from Columbus SP. I'd have to check to see if it will take a 35, but I know it will fit a 32 with ample clearance. The threaded fork steerer is extra long and should fit a headtube up to 200mm long. PM me if interested.

It makes all kinds of noises! No out of saddle required lol.

Man, I really hadn't considered a new fork but that might be the best solution.

Loosen the mounting bolt nut and see if there is any play that could be exploited to raise the caliper slightly.

Some play could perhaps be added in the "up" direction using a chainsaw file or Dremel carbide bit (be prepared for a thousand sharp steel shards to get into all of the wrong places like your eyes, clothing and skin, so best done outdoors, over a grassy surface, while using suitable protection).

Another bit of improvement might be gained by using a centerpull caliper.

I hadn't thought of this.

Related question: what's the minimum amount of clearance needed between tire and caliper to be safe?

There is no "standard" for clearance as the entire matter is is statistical in terms of what objects are around that might stick to a particular tire.

I've had a sizeable chunk of bark stick to a smooth rear tire and lock up the works, but it's impossible to predict all of the circumstances that could cause such an event.

650B conversion? I guess that would mean you can't use those exact tires you have. But it would be the least "hacky" way of solving the issue.

Yeah, and pricey too unfortunately. But that is something to consider for sure.

T-Mars's suggestion of a drop bolt mounted upside down seems easy, cheap, and effective to me.
Brent

If it runs the calliper, not the frame, try some different calipers?

I know you said you like the tires, but likely the simplest and least expensive fix is go down to a 32mm wide tire. Do they offer it in a narrower width?

I'd go by T-Mar's suggestion of using crescent shaped spacers on the dropouts. Easy, inexpensive and reversible.

That looks like a Continental Cyclocross Speed. Great tire but available only in one size, 700x35. Not sure about the replacement (renamed) Speed King CX. The similar but wider Conti Speed Ride is my favorite hybrid tire, but also available only in 700x42 (nominally -- actually measures closer to 700x38). The Speed Ride is the smoothest rolling wide tire I've ridden, plush at lower pressure without feeling sluggish, and a great design for anything from smooth pavement to most gravel and some dry grass (it's not a mudder).

There are other brands of dry condition cyclocross tires with similar file tread and vestigial side knobbies in narrower widths, but I don't know if they're as pleasant to ride as the Contis.

Occasionally I've mixed wider rear and narrower front tires of similar designs to get around the fork/brake clearance problem. No handling problems with the bikes.

The only person I've ever seen hazard a guess on that would be Jan Heine, who suggests 3mm. When I saw that I wondered if that was to help sell his wide tires and if he was ready to face potential liability. Even in a place like this I'd never give a number. But more than three millimeters. If you follow up on suggestion to respace forkends with some kind of washer, secure those washers with some braze. If you can find a framebuilder who'd cooperate with that scheme.

The other way to ask the question is how much clearance would be useful? And the answer is a lot. For the terrain that tire was built for you could hardly have too much clearance. A full centimeter would be a good starting point. For a fat road tire you'd not want that much clearance unless hoping to use fenders. For offroading the more the better.

A longer fork will slacken both head angle and seat angle. You can adjust the saddle. There will be slightly reduced standover and a non-horizontal toptube. Horizontal toptube is part of the charm of a bike like that. Slack headtube gives higher trail if the fork rake is not increased at same time. Lots of riders like high trail for offroad. Bending the fork to shorter rake will also give higher trail but you'd have to bend a lot to get a little bit of clearance. And then others of us want low trail.

It's going to be much easier to find a different bike than to mess around with altering or swapping forks. Those were nice bikes. Keep it as a road bike. Lots of terrain is possible on 28s and 30s. Look for a frame with clearance. Older road bikes - older as in early 70s and even 60s - have clearance. Touring frames built for 27x1-1/4 have clearance and many of them have geometry useful for what you are attempting. Some have canti mounts too. Old frames are very cheap. Patience and keep your eyes open.

Lots of solid advice here, thank you for taking the time to put it in writing.

Actually they do offer a 31mm tire. Not cheap though :/

Actually it's a 33mm Vittoria Terreno Dry. I may try the 31mm version at some point in the future.This is mostly an experiment as I have other bikes I can ride with more clearance. I just love this old steel frame.

Nifty. Even better specs than the Conti Speed Ride. I'll put that Vittoria on my wish list.

It really is a fantastic tire. Fast, grippy, durable. Hard to fault it.

I have done 2 things; Firts was to grind the brake caliper on three bike and one of those bikes, the fork also. and second I have also taken a block of wood and whacked the brake caliper to bend the shaft of the brake up a bit.

And you openly admit it in this forum:thumb: