byrd48

Hi,
I am building up a touring bike from a vintage Miyata 310 frame. I have 32mm tires and Tektro r539 brakes. No problem on the rear, but when the front caliper is open, the right arm goes into the tire about 3mm. I have to squeeze the caliper to mount the tire. That being said, they will work once the cable is installed. They can open enough without contacting the tire, but I guess the obvious concern is if the cable brakes while in motion, it could result in an endover I suppose. I tried the Tektro r559 and they do the same thing, but the brake arm only goes maybe a millimeter into the tire.
Does anyone have a setup with such tight tolerances? The rim is Mavic Open Pro, so it is narrow for that tire, and I presume a narrow rim makes a taller tire? Three Rivendell website mentions using 32mm tires with the 539s, but I know there are lots of variables from the tire to the rim to the fork, etc. The tires are Conti GP 4 season. I haven't found a good way to compare tire height across different brands or models. I found a folding 30mm tire (Challenge Strada), but I suppose even those may not fit. I was going to avoid doing to 28mm. Any advice?
Thanks!

maddog34

go to the 28's.... or smaller....

CliffordK

It is not uncommon to have too narrow of calipers when mounting tires, and sometimes one has to deflate a tire to mount it, or remove a brake pad. But, that generally doesn't affect it during normal operation.

Perhaps post a photo of where the brake and tires are contacting. It may be an adjustment issue.

byrd48

The front most caliper arm hits the top of the tire on the tread. I'm not too worried about the inconvenience of tire changes, the larger concern is if the cable broke or disconnected while in motion, the calipers would open up and engage the tire. The best outcome would be shredding the tire and the worst would be head over heels. Having said that, in 12k miles of riding, I have never had a brake cable failure.

CliffordK

How much tread do you have on the tire? What does it feel like to remove the straddle cable and turn the wheel?

The front tire should pull the brakes forward, so less likelihood to get parts jammed under the fork crown.

Cables do break from time to time. I think the last couple of shifter cables I broke came apart cleanly. The last brake cable that broke may have disintegrated and stretched, and was even partly functional for the rest of the ride. I think the vintage split cable keeper at the brake lever also had widened, so that may have been part of the issue.

byrd48

The tires are new. In fact it's a new build other than the frame. Here is a video
https://https://goo.gl/photos/MKxJ5ngA1ZqFLF82A

cycledogg

Photo please.

byrd48

I posted a video link above

CliffordK

That looks tight.

You should be able to figure out how to simulate a total brake failure. Perhaps if you have Tektro levers with a release button, see what happens when you release the button.

I'm doubting it will cause a crash. Probably more like unexpected braking (which you may be able to pedal through).

However, the bike will likely also be generally unrideable without the brake cable. Thus you'll be hunting for some method to keep it locked open if you have broken cable and need to keep riding.

Have you used the GP 4 Season tires? I have a rear on one bike (23mm or 25mm) that is looking mighty bald, quicker than I expected, maybe around 2000 miles or so. I'm not sure how many punctures I've gotten. Nothing too unexpected so flat protection seems to be fine, but wear is short.

woodcraft

I think it's risky to use that tight of a set up in any case,

as road debris could jam the wheel.

Iride01 

That's not very much space. That is what a 27" wheelset in a frame meant for 700C's will look like or a 700C wheelset in a frame meant for 650b's or 650c's.

One of the other things that makes me think this is that your brake pads appear to be adjusted to the max diameter they can handle, instead of about midway in the adjustment setting.

Iride01 

I just went out and looked at my '78 Raleigh and '91 Paramount. Just looking at the front fork it looks like I'd have at least a 1/2 inch of space if I had a 33x622 tire on mine.

My brakes are normal reach brakes, but if yours requires short reach brakes then that changes things quite a bit.

andr0id

I always say allow at least 1/4". Sometimes that's not enough.

I rode over a section of road earlier this summer between Kamas and Park City that had been freshly paved and tar coated pebbles kept sticking to my tires and jamming in the brake bridge and fork crown. It was really annoying as it was lot of climbing and it would bring me almost to a stop, then I'd have to hop off, clear the tires and go again.

byrd48

I saw in another thread where someone used campy skeleton brakes with 32s. Looking at them, the arms do seem higher, both are pretty much level with the mounting bolt. It would be a little pricey to order them just to find out....

CliffordK

It is a good point that not all brake calipers are the same. The modern Shimano dual pivot calipers are symmetrical, so a single side won't droop, but I'm not convinced clearance would be any better.

Vintage center pivot side-pull brakes are also symmetrical, and shouldn't have the issue. And, are often a bit more slender in design.

It might take some sleuth work to find the best brake combination for that fork.

corrado33

Yes, if the cable broke between the two arms of the brake it would contact the tire, but all you'd have to do is wrap the cable around one arm then mount both sides with the mounting bolt to hold the brake in a semi-open, semi-closed position. (By "arm" i mean where the cable runs through)

In theory, your tires are too big for your bike. In reality, it's not as bit of a deal as you'd think.

Brake cables don't really break... unless neglected for decades. Just make sure to inspect the cable every once in a while.

byrd48

I made some progress. I found a pair of short reach brakes that still contact the tire when open, but not as much as the mid reach ones I was using. I'll try to find a few more models to test and post what I find.

Iride01 

And you are sure you have the correct wheel size? 1985 and previous Miyata 310's were spec'd with a 27 inch wheel. 1986 Miyata 310's were spec'd with a 700C wheel according to the catalogs scans I viewed.