PGillin

That just sounds like such a fun title, right?
Well, to make a long story short I have an '87 Bianchi that originally had (I think, I bought the frame recently, wheel-less) 650 wheels. I want it to run 700cc wheels, which will fit the frame (I checked, the wheels off my allez fit). The problem is this-
It has Canti braze-ons. The existing brakes won't reach high enough for a 700c rim. Is it possible to get brakes that will fit the existing braze-ons without breaking the bank or lowering myself to a V-brake?
The Bianchi is my project bike, FWIW.

fietsbob

Pauls Comp of Chico Cal has a BMX V brake that slides the brake shoe holding part up a round lever,
so you can move the brake shoe closer to the end of the arm.. and clamp it there.

deermouse

It sounds like you're trying to run road wheels on a mountain frame. I've considered doing this and decided that it is unlikely that you will have a good result unless you have a torch and can move the brake bosses (if the frame is steel). I have a torch and have built frames, but thought that moving the brake bosses was more trouble than it was worth. A more reasonable solution would be to run 26 inch wheels with either slicks or semi slicks for the road.

PGillin

Fietsbob-
Those would work, yes, BUT Paul's comp is expensive and it's a V-brake, which I've heard can be rather weak. Maybe I'm wrong.

Deermouse-
It's a cross frame, so very close. It is a steel frame, but the torching is a bit out of my league and would kill the paint. The bolt-holes for caliper brakes exist, so I could always go that route, but then I would be left with brake bosses on the front fork and seat stay, and I'm not sure how I would cover those.

Abe Froman

https://www.dreambike.com/69.htm

LesterOfPuppets

V-brakes are plenty strong. Won't be quite as strong with the pads way out on the end, but they'll get you slowed down just fine. Not sure if there are any non-boutique long reach Vees and I've never heard of any long reach Cantis.

There are some that are about $15 cheaper than Pauls, Little Dude Components makes them for the BMX market.

What bike you got? Any chance of caliper fitment? They'll be a little weaker than Cantis and Vees, but will still stop you plenty well.

Jeff Wills

That's really, really weird. The distance from the pivot to the brake shoe on cantilever brakes has been pretty consistent as long as I've been working on bikes... basically the last 35 years. Any chance you can post a photo or two of the bike, showing the front and rear brakes with the wheels installed? Or at least tell us which model Bianchi you have?

deermouse

Yes at $125 per wheel, Pauls comp is expensive. I thought the Mavic units at $60 per wheel were expensive. I guess everything is relative.

I don't quite understand. A cross bike with 650c wheels doesn't make sense. The larger 700c wheels would be easier going over obstacles. I guess that is why you want to convert to the larger wheels. The 26 inch mountain bike wheels get the added diameter by using fat tires so the outer diameter is about the same as 700c. I don't think you can even get 650c cross tires. Is this a ladies or kids bike? Are you sure it's a cross bike? Do you intend on using it for cross or on the road? If it really is a cross bike you will change the geometry by putting larger wheels on. Mostly you will raise the bottom bracket which on a cross bike will already be on the high side.

One possible option for removing the brake bosses is that on some of them the posts unscrew. You would have to leave the bases, but you may be able to unscrew the posts. You can tell if they are screwed on because they will have flats near the base to put a wrench on.

deermouse

You obviously have a lot of expereance and I don't mean to be condescending, but it isn't the distance from the pivot to the brake shoe that's a problem. It's the distance from the axle to the rim. With a 650c wheel, the brake bosses are mounted closer to the axle than with a 700c wheel.

I would also like to know what model Bianchi it is.

FBinNY 

Mavic makes - or used to make - a sort of brake booster horseshoe, which also raises the pivot bolt specifically to convert mtn fork/canti bosses to 700c rim height. I don't know if they still exist, but if you search around you might find a pair. I know a number of people that used them to convert 26" mtn bikes to 29s (700c in mtn lingo) & they do the job very well.

deermouse

If you decide to use caliper brakes, be sure you can find some with the correct reach. If this is really a 650c cross bike, you may end up needing some very short calipers. I still question if this conversion is worth the effort.

Jeff Wills

I think we're on the same wavelength, so please don't take this as snippy:

The OP posted that he bought the frame wheel-less and put 700C wheels on it. With a picture I can diagnose the issue in a couple seconds. Since he's looking for cantilever brakes with greater-than-normal offset from the pivot to the brake shoe, it could be the wrong type of brake, the wrong wheels, or something equally simple. A picture is worth a thousand posts on a forum.

fietsbob

Ditto :cannot think of a cantilever that adjusts more than 10 MM in a slot,
for the pad holder bolt.


If it is 650B they are popular now, rims and excelent tires are offered again
so why not built the right size wheels ?
a drawing with the dimensions measured and written in the drawing, is even better ..


V brakes properly adjusted are plenty strong .. but

In the forces math of levers, a V brake being a class 2 lever ,
the further away from the fulcrum the work is applied , the lesser the leverage..
leverage is the mechanical advantage of V brakes ..

absent real data..
I would suggest solving the whole issue and build up wheels with Drum Brake hubs.
then where those frame fittings are doesn't matter since you wont be using any of them, and unlike disc brake you dont need any special fram fittings

build up the right sized wheels is probably best , or admit you goofed,
bought the wrong stuff for what you wanted to do,
and sell the frame again and get the right stuff.

you sure , it might be an old touring frame /. [for 27" wheels?] ..

Raleigh Portage went wit 650B, but they went out on a limb and
only a couple decades later did the non domestic, French market, start
paying attention to the demi ballon tire 650b wheel.

.. still pretty much blind guesses.. though

You might even have bought a U brake frame, I have no clues , really..

good luck ..

LesterOfPuppets

The 1987 Bianchi catalog is up on VeloBase and it has a Volpe model for CX and touring which came stock with 700c rims and Shimano AT-50 cantilever brakes.

Greyryder

The Paul brakes will work, but with the pads that far up the arm, you might need to use a short pull lever, instead the long pull Vees normally take. If the posts can be unscrewed, they make things will bolt into the brake bosses and basically move the posts up or down depending on how you install them.

These are the ones I've seen. They'd be cheaper than the Paul brakes, if you're bike can use them.

Medic Zero

Thanks for posting that!

I've been toying with the idea of running a 700cc wheel on the front of one of my commuters, this:
https://www.dreamride.com/bikestore/i...product_id=143
will make that possible!



In regards to one aspect of the OP's conundrum - I've seen little caps to plug unused brake bosses which helps a little if you end up not using them. I'm considering going drum brake rear on my MTB tourer that originally had the U-brake, I've got the item bookmarked somewhere around here...

fietsbob

I noted at the time , once the adjustment of the shoe height was in the brake caliper .
the latitude for siting the brake boss , got to be a looser dimension , in MTB frames
than with the old Mafacs, which had to be right, in the first place,
because they had all 3 points fixed.

cyccommute 

Are you sure it's a cross frame? The '87 road bike catalog from Bianchi lists only the Volpe for cyclocross and that takes 700C wheels as LesterofPuppets points out. 650C wheeled bikes were very rare in that era. Are you sure it's not a mountain bike which takes 26" wheels (559mm ISO)? That would make your life a whole lot easier.

On the other hand, you could look for a set of Tektro 872 brakes



instead of Paul's Motos. They have some height adjustment. Not as much as the Paul's and you have a long distance to cover but they are good brakes.

Another alternative is an Avid Trialign



Again, they have significant height adjustment.

Both brakes are no longer made but they do show up on Fleabay.

PGillin

The bike is a Volpe. It's supposed to have been stocked with the 700c rims?
I have the canti brakes sitting on my work bench (Next to some metal polish and chamois cloth), but if I take a 700c rim of my allez, ease it into the Volpe frame, and put the Cantis on, I see no way to make them reach.
It is possible that I'm doing something wrong with the cantis, though, and don't have them aligned properly. I thought it was a cross frame, but it might be touring. I got the frame for DIRT cheap, so I'd really like to be able to work with it and get it properly set up. I'll try and get some pictures up later on.
Thanks for the advice, there's a whole laundry list of valid points to consider in this thread.

FBinNY 

This is one of those instances where a bit of measurement might eliminate lots of guess work.

Measure from the canti boss (center at the base) to the center of the axle.

for a 26" (559) mtb wheel this will be roughly 253mm
for a 700c (622) rim the boss will be 33mm higher, or roughly 286mm from the axle.
for a 650b (584) rim it's 265mm

I say roughly because there's a bit of parallax error depending on the fork rake, and the depth of the boss, but it's good within a few millimeters in either direction (that's why the brakes have a shoe height adjustment).

If the bosses are at the right height for the wheel, than you're doing something wrong.


Also be aware that there were a variety of brake designs over the years with different boss heights with respect to the rims, including some where the boss was above the rim. The relative height of the boss to the rim will confirm wheel size and the required brake design.

nfmisso

Hi PG;

One possibility that no one has mentioned is that the frame could be for ISO590 (26 x 1 3/8) rims. My SR Sierra Sport (mid '80's "mountain bike") was made with canti's and ISO590 rims. For more on my bike: https://forums.bicycletutor.com/thread-3036.html

I orginally tried fitting a ISO559 (mtb 26") rim, brake pads were way off; measured decided ISO571 (650c) was the way to go. The pads are as far down as they can go on the brakes, work well. 20-20 hindsight, I should have gone with ISO590. ISO584 (650B) is another possibility, but tires are expensive, and not higher pressure.

The brake bosses are too close to the axle for ISO622 (700c) to work, but anything from ISO571 to ISO590 would line up fine.

Suggestion: mount up on arm of a canti or V-brake, measure the distance from the pad center (which is extremely close to the bead seat diameter on most rims) to the axle center. Do this for the min and max for the pad location on the brake arm. Convert to millimeters and multiple by 2 to get the ISO rim bead seat diameter range that will work with the brakes you have on that frame.

Personally, I have found V-brakes to have much stronger braking action that cantis; and much easier to set up. I converted both the SR and T50 from cantis to Avid V-brakes. The T50 was scary with the OEM Shimano cantis; and became confidence inspiring with the Avid SD5 V brakes.

PGillin

If I said the bosses were at 268mm, what would you tell me?

Jeff Wills

OK, so: https://www.sheldonbrown.com/volpe.html

Again, a picture of your setup would help immensely. It sounds like you have the correct diameter wheels, but they're much narrower than what came stock on the bike. This will make cantilever setup either impossible or a royal pain, depending on which cantilevers you're trying to install.

BTW: it's "700C", not "700cc". It's a size designation, not a measurement of anything real: https://www.sheldonbrown.com/tire-sizing.html#french

FBinNY 

I would say that your Volpe originally came with 650b wheels, and you will not be able to use 700c wheels and standard canti brakes.

This is exactly why I suggested measuring the canti boss to axle distance. Now you have the information needed to make a decision about the options, new 650b wheels, caliper brakes, brake boss adaptor (if one exists), new fork for 700c wheels, or some combination of the above.

catmandew52

A single picture is worth a thousand words.
Are you checking front and rear canti bosses or just the front?
If you are only checking front, maybe fork has been changed to MTB fork.