Colnago Mixte

I have a Univega Gran Rally I'm working on that needs just a "skosh" more clearance in the back. I'm running 28 mm tires, and while the brake bridge has about 4 mm clearance, when I put a set of brake calipers on, they drag on the tire. I'm not running a rear brake presently, but nearly got killed while sprinting for a red light yesterday that changed at the last second and having to stop quickly with only a front brake. Not acceptable.

So I was wondering if anyone knew of a cheap road bike brakeset that has an exceptionally low profile underneath, a profile that is the same as the height of the brake bridge.

I have seen some Tektro brake calipers that might work, but tire clearance is one spec that is impossible to get unless you've bought and used the brakes. Thanks in advance for any helpful replies!

mrv 

well one option is to go single speed and add a coast brake. You'll need nearly horizontal drop outs, of course. a short google search shows photos of your brand bike that might accommodate.

I am presently setting up a SCHWINN Super LeTour 12.2 with a coaster brake. But I actually want a single speed. And if I like it I'll probably switch over to flip flop hub. I was using the wheel on a STEAMROLLER Surly, but it got sold. Too small.

You could check out a Center Pull style brake. Below are some image from a recent switch I attempted for the EXACT same reason, I was wanting to run 37mm tires in a frame that fits 32mm's fine. The 37mm would drag dual piviot side pulls, but the MAFACs did not give as much clearance as I was after. Maybe about 1mm clear - not enough for dirt road.

ALSO - keep in mind the height of your tire is affected by your rim width. If you have extra wheels you're using.
Hopefully these are helpful.



Top: 32mm w/ dual piviot Bottom: 37mm w/ Center Pull


Dual Pivot with 32mm tire - plenty of clearance


Racers with 37mm tire - TOO CLOSE FOR ME!

thumpism

Drop bolts are available for some brakes (Campy) and can lower or maybe also raise the caliper relative to the frame, but might not be available for your brake.

79pmooney

A thought, not researched: Get a block of aluminum. Drill it for your bridge diameter, Cut it at the edge of your hole, then file the hole to form a "U" that fits snugly around your brake bridge. Now chisel or file the flats to fit the bosses on the bridge. Drill for the brake bolt through the bridge drilling and again above the drilling. You now have a "drop bolt" that will raise the brake attachment point above the brake bridge. (This will have to be done carefully so the fit to the brake bridge is quite close as braking will be trying to spin this unit around the bridge.

Do some research and thinking before you start! This has had all the time it took me to type this in the concept and design phase!

Ben

mixteup

Don't know if it's possible, or even a factor, but is your wheel as far back in the dropouts as it can go?

caloso

The Ultegra 6800 calipers have the best clearance I've had, but they're not cheap.

fietsbob

In the neolithic era there were drop bolts for single pivot brakes such as campag.
to go on frames, with higher rear brake bridges.. BITD, Universal made a long reach rear sidepull ,
and a shorter reach front..

<C> had produced shorter reach brakes, so those drop bolts lowered the brake to reach the rim

In your shop. perhaps you can make something like that, as a rise rather than a drop, offset..








...

dsbrantjr

Before you go too far make certain that there are no other clearance gotchas; on two of my bikes the front derailleur mechanism is the limiting clearance for the rear tire.

squirtdad

the 5800's have good clearance also......and are a bit cheaper and work great I have a set on a 90/91 derosa frame and it looks like 28 would be no problem at all (am running a michelin pro4 25mm which is as fat as some 28's I have and there is still room)

caloso

Yep. That's exactly what those tires are. Biggest "25mm" tires I've ever run.

Colnago Mixte

Yes, I even took the adjusting screws out, but no go. Maybe I could widen the dropouts? Re derailleurs. I have several different fronts "ders" I can use, and ran into that same problem with one of them.


So no one knows of any really cheap brake calipers with good clearance?

squirtdad

under $30 5800 Shimano 105 5800 Road Brake Caliper | Chain Reaction Cycles sAgKL1g58_dc pcrid 253659801802 pkw pmt prd 419009US

under 50 the 7000 (newest version of 105) states it will handle 28mm (think the 5800 does also) https://www.competitivecyclist.com/s...kaAvc5EALw_wcB

Colnago Mixte

Yeah, those are some decent deals, I was hoping to spend under $50, thanks!


I did find a rather unconventional solution, and it's working fine so far. It's an old trick. As Maxwell Smart would say, "Ah ha! The old 'long reach front brake caliper, mounted backwards' trick. Oldest trick in the book!"





I thought at first my leg or foot would hit the calipers, but so far, so good. * knocks on wood *

Crankycrank

That will work but you could also try adding a 3-5mm spacer between the caliper and the brake bridge. The extra length from the bridge angles the caliper away from the tire possibly giving you just enough clearance.

Colnago Mixte

I tried adding about 10 mm of spacers and it was still not enough.

zacster

Well, how about a narrower tire? I had a 700x25 in my rear that didn't quite fit and I just swapped it with the 700x23 in the front. Problem solved.

Colnago Mixte

I was shopping for some 25's or 26's, but fixed the problem in the meantime, saving myself 70-80 bucks. The brakes I used are actually not "long reach" they're "mid reach", FWIW.

XXLHardrock

Colnago Mixte

You sir, are a mind reader, that's exactly what I got. Mine are supposed are be medium reach. And I was able to buy just the front brake instead of a set, for around $25. Won't win any beauty contests, but ought to do the job.

canklecat

Single wall rims may provide a bit more clearance.

My Univega Via Carisma came with single wall rims. Continental Speed Rides (nominally 700x42, actually closer to 700x38) cleared the rear with room to spare, including the front derailleur swing -- although a flatter cable clamp bolt, or grinding down the original, would help.

But after a car hit us a few months ago the wheels were replaced with double wall rims. Now the rear Speed Ride just barely clears with only an nth of an inch to spare. I tried a Michelin Protek Cross Max (nominally 700x40, closer to 700x45) and it was no-go. Wouldn't even seat between the chain stays.

Other than being hit by a car those single wall rims were fine for more than 20 years, with only occasional tweaks. It was about time to replace 'em anyway due to brake wear.

TallRider

A single-wall rim won't result in a lower tire. But a wider rim will result in a sligthly lower tire profile (and most single-wall rims are wider).

Your brake bolt is in a fixed location, and apart from drop bolts, you simply want to find a brake that has the most clearance by the brake bolt. Changing the length of your brake's arms won't help either, unless you're changing to a smaller-diameter wheel size (like 650A). Otherwise, the distance between the brake bolt and the rims won't change.

Since you're talking about the rear brake, why not use a single-pivot sidepull brake? Not as strong as a dual-pivot, but a rear brake doesn't need to be as strong anyway. This will often provide more clearance than a dual-pivot brake.

canklecat

Could be a difference between the nominal (both are nominally 622x19) and actual widths on the single and double wall rims I've used. I just found my micrometer so I'll check next time I have the tires off.

Colnago Mixte

I know I rode this bike with 28 mm tires before, but I can't remember which wheelset I was using. So yeah, rims will make a difference, surprisingly, I just can't remember which wheels they were. Everything is good now though, very happy with the bike.



Bike is fine, I just wish the powdercoaters hadn't done such a sloppy job, see that rust they left under the bottle boss? Very sloppy work, IMO, plus they put a whole bunch of new scratches in the frame while working on it. Bastards, I'm not taking any bike frames back to them again.

mrv 

- Rust under the powder ~ that's a bad scene. Maybe someone else can confirm, but I believe that will lead to longer term problems.
Powder Coating is basically like shrink wrapping your frame in plastic - the powder melts at 400F or something. At that temp the frame will be dry, especially if a pre-bake was done. But leaving rust under the power - I dunno. Water can't get to it, but if they were on conscientious enough get to bare steel, I would be worried the corrosion could continue.

I had a frame that was powder coated new ~ but took a couple of tries before the frame builder was satisfied. I think it corroded from the inside of the frame out. The powder started to show blisters in places. By the time I could afford to get a new paint job, it was too late. Too many spots corroded from the inside of the tubes out. Keep an eye on it, I guess.

Colnago Mixte

I live in a very dry area and ride in the rain about once every 4-5 years. I would like to think that if a small rust spot is deprived of both oxygen and moisture, it won't spread. But fortunately, the powdercoat is clear, so it will be no problem at all keeping an eye on it.

What worries me most is the thought of trying to remove the old powdercoating, I hear that's not a fun job.