yellowbarber

Hello, hello.... I am swapping out the wheels on my Bike Friday tandem from the original Sun CR17 rims to RhynoLite XL rims. The problem I'm looking to solve is dues to the kind of narrow c-to-c spacing of the brake bosses. Presently running Avid SD7 v-brakes which are already set up as far out as they can go and still have correct contact with the rims' breaking surfaces. So, the question is - does a good v-brake exist with a wider profile?

fietsbob

Doubt it, because V brake pivots are on the end (Type 2 laver = fulcrum- work- effort ,in that order)

Yours is about the same as everyone else's V brake...

Shimano's CX 70 cantilever brake has an off set pivot bushing .. but its not a V brake





I have a BF Tikit with V brakes _ stock parts _ ( Similar V brake, Tektro ... they work adequately .. I changed the pads..

Can you offer measurement numbers ? width of posts C to C.. ( mine are about 72 mm )

there are a number of different arm lengths .. with resultant cable pull demand differences.. pivot to cable clamp...







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stevoo

You can configure the spacer stacks on the pads to narrow or wide. Swap the thick and thin as you like from outer to inner.
Normal stuff.
Good luck.

raria

Cantilever brakes are ideal for your situation. The challenge is that cheap cantilever is cheap cantilever brakes are far worse than cheap V brakes. Try to get an more expensive version, tektro has some pretty good ones and as a bonus they're only about a hundred and ten tohundred 20 g each

CliffordK

I wonder if one of these would work.
https://www.amazon.com/Components-Br.../dp/B0781XX9Z9
https://www.amazon.com/Cycle-Group-P.../dp/B00QICKB12




One of the issues you have with the V-Brakes is the pad mount.

You usually mount the pads as:

Nut -> 2 swivel washers -> V-Brake Slot -> 2 swivel washers -> Brake Pad

Now, the swivel washers come in fat and skinny. Make sure you use the skinny washers between the V-Brake slot and the brake pad, and the fat ones on the outside (in this case to save space).

Hunting online, I found these V-Brakes. Not seeing a lot of info on them, but perhaps the company would sell a couple of pairs, plus pads, or you can find similar ones.

https://www.ecvv.com/product/3512220.html



By using Canti-style adjustment, it should allow you to move the pads out slightly further. Will that be enough?

There have to be other companies that use this kind of side swivel mount for the pads.

yellowbarber

I realise that cantis would be the ideal solution. And I actually have a couple of really excellent sets to choose from.
The inconvenience they would present is that the Bike Friday is a break-away travel bike and cantis could potentially add a significant amount of time to the unpacking process (or not). I'd also have to find cable hanger solutions for an out-of-the ordinary frame design.

CliffordK

Oh, those V-Brakes I found. I'm seeing a few companies that seem to sell them, and may have stock.

https://www.sparksports.com.br/freio...m-macaneta-par
https://www.sparksports.com.br/kit-d...r-sem-macaneta

However, they are listed as PLASTIC or NYLON. I'm not sure I'd choose to go that route. Although, it might be interesting to experiment with.

Ahh, here we go. Alonga and Tektro both have (or had) post mount V-Brake pads.

Alonga V-Brake Post Mount Calipers Alloy Silver with Pads | Get Me Fixed
Alonga V-Brake Post Mount Calipers Alloy Silver with Pads | Get Me Fixed
Tektro 826A V-Brake Alloy Caliper Graphite Post Mount Pads | Get Me Fixed
Alonga 601P V-Brake Post Type Pads Black Plastic Caliper | Get Me Fixed

Oops, that last one may be plastic again.

yellowbarber

thanks for the lookout!

Should have been specific when I said that I have the Avids set up with the skinny swivel washers on the inside.
Also, my experience as a mechanic with those particular v-brakes (pictured) is that they are OEM on some of the ****tiest junk department store bikes I've ever had to deal with. I joke that we should have a pro-rated surcharge for servicing cheap brakes.

That said.... that Promax mod looks like it would work great with a rollercam or centerpull conversion.

CliffordK

I did realize the error in my ways finding plastic brake arms... thus the second post.

The post mount brakes give excellent 3-D adjustment, but are a bit of a pain.

However, I think you might gain 1/8" to 3/16" on each side or so by going with post mount pads. Would that be enough?

I did find some nice ones that were on a MTB I gave to a second cousin, but I don't remember if they were cantis, or V-Brakes.

Just, that mount has fallen out of favor in recent years (get the wrong holder, and finding pads can be a pain too).

fietsbob

Perhaps my pad link was subtile _ these use half a swivel washer the other half is the back of the pad holder,,

Kool Stop International - High Performance Bicycle Brake Pads Since 1977




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CliffordK

That may or may not save space, but certainly worth exploring.

I've noticed that canti pads tend to be long and skinny, while caliper pads tend to be short and fat. So, it is also possible that those pads are not particularly designed for cantis.

One advantage of road pads is that they woudn't extend between the seatstays or fork blades, if that is an issue.

sweeks

I put these on my folding commuter bike a few months ago. They are very nice for 20" wheels because they're shorter than many other pads I've tried; the middle sections of longer pads tend to hang off the inside edge of the rim, while the ends are on the braking surface. If the middle sections are on the brake tracks the ends contact the tires.These (pictured) work well. They also seem to allow the (V) brake arms to sit closer to the frame, or, equivalently, the pads can be farther apart with the brake arms in their "normal" positions. The issue was that the new wheel set has wider rims, right?

rm -rf

My TRP mini-V brakes didn't work very well with my wide rims. The arms had to angle out instead of staying quite parallel. Even the thin swivel washers were too fat. And I even tried just a very thin washer, but then the pads didn't adjust angles, and it was still too fat.

It works great now, replaced by Kool Stop Thinline pads. The brake arms are correctly positioned.
The only problem I have is these long pads touch the inside of the fork when the noodle is disconnected for wheel removal. My biggest tires (38mm) need deflating to remove the front wheel.

Like sweeks mentioned above, these pads might be too long to work with smaller diameter wheels.

Comparing pads thickness and length
My TRP CX8.4 had fairly thick pad holders, with thick rubber. And a lot shorter pad length than my Thinline pads.
The photos of SD7 v-brakes appear to have fairly low profile pads already?

yellowbarber

Yes, the main problem is that the new rims are significantly wider (29mm) than the old ones (23mm). The old rims were kinda cheapo double wall joints & the Rhynolite was the only 20" rim I could find with 40 holes.

sweeks

Another problem with narrow rims is that when they're used with wider tires, the tire gets in the way of the pads when the brakes are off. This means the pads have to be adjusted closer to the axle to clear the tire, and less pad is on the brake track. Plus the rim gets worn in places it's not supposed to be. Tricky adjustment.

fietsbob

A paper on brakes for your math & mechanical engineering majors ... https://www.circleacycles.com/cantile...i-geometry.pdf

yellowbarber

Most of that long algebra is way over my head, but the bits I can grasp are extremely useful. Thanks!
UPDATE: I'm in the middle of a job on an '88 Trek 520 which also has the same problem of the brake boss clearance.
The bike (Trek) was designed before linear pull brakes were a big thing. Was hoping to switch to V-Brakes, but nothing but a traditional type canti will work without modifying the frame itself

fietsbob

I have 2 old bikes; Mafac Cantilever Brakes work , I have some others too , mostly Cyclocross brakes ,

Modolo, SRP 'Mr.. Grumpy' & Spooky a NL made brake in Carbon Fiber ..

and From Burly while I worked for them in the tandem assembly shop.. Scott Matthauser SE.. Front & Rear

They went on my Touring bikes 2 of them ..Moved from one to the other ...








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Kimmo

Why? The only such obstacle I've come across is when there's no rear housing stop on the top tube; instead there's a little tube guiding the cable around the seat tube.

You can either just run full length housing all the way to the noodle, or get fancy and use a stepped ferrule (like those required on old school RD housing stops - a good modern source of such a part can be found inside those stupid 'anti lock' noodles containing a spring; or perhaps use an 'acorn' for old school drop bar levers, some of which have an extra step). It's tricky though, because the proximity of the end of the tube to the brake means you have to nail the geometry; the noodle needs to be trimmed and tweaked, and the bit of housing is so short that its length is critical; a couple of mm can matter a lot.

yellowbarber

Thanks for the input, but the problem I'm trying to solve has nothing to do with cable routing. Or narrow rims @sweeks
I'm a mechanic myself with a nominal amount of experience and problem solving is one of the things I dig most about my job. This, however has got me stumped. Without trying to describe how to build a watch, let's just say I understand how to setup & adjust a V-brake. Apologies if I didn't make that clear earlier.
The problem is the c-to-c spacing between the brake bosses!
When the rim is too wide, (or the spacing between the bosses is narrow) there is not enough room to set up and align the pads correctly with the V-brakes I already have (Avid SD7), plus pushing the arms out away from the pivot center, thus losing spring tension.
SO: do different models of V-brakes have a shallower profile (c-to-c) between the pivot and the pad mount than others?


The bike concerning the original post is a Bike Friday (20"/406 etro wheels) that was designed for a V-brake. That bike is in my other workshop about 3,000 miles away, will be back there in a few weeks to spin the wrenches and do a little more head-scratching.
The attached photo is the Trek I was talking about - as an example of narrow c-to-c brake bosses - and there is NO WAY one could get a V brake to work in that narrow a clearance without brazing on new bosses that were centered further away from the rim. The Trek's problem is solved. Cantis it is, just not these 1st gen Deore joints.


1988 Trek 520 - narrow brake boss clearance.

fietsbob

Millennials NB;.... pictures are not = measurements..








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yellowbarber

My bad, Bob... pretty much missed that you'd asked for measurements a while back.
But hey, I'm a 52 year old millennial!

This thread has swerved off topic.
I'll check back in about a month from now when I am at my other workshop where the Bike Friday is waiting.
There I can take appropriate measurements and resume problem solving with the suggestions already put forth.

CliffordK

I was browsing a bit today and bumped into the TRP TTV Aero V-Brakes (TTV06)

They aren't cheap, but might do what you're wanting.



It appears as if there are a couple of other similar brands of aero V-Brakes.

Fouriers

KCNC

I think many of them appear to be relatively short Mini-V (less tire clearance, less lever/cable pull).

fietsbob

for very skinny tires only.. cable across between them can't clear much , from the look of it..

I have a 30 year old Pinarello CX, ...front fork might as well be off a touring bike*, ... brake posts centers Measure 62mm apart..

I have cantilever brakes on it.. 32 to 34 tires ..

*no mudguards though.. or a place for racks..

[ I own 2 bike Fridays, both have V brakes , Tikit and a Llama .. (Llama has disc mounts , nothing on the V brake posts ..)]






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