emhava

Hi, I am replacing my old Tektro V brakes with new Shimano Deore V brakes and I am noticing they don't slide completely and make the posts look shorter and the arms are not flush like the old ones. The difference is significant, adds up to half of the width of the busher of the Shimano brakes. I am worried that with time and hard breaking the bolt might snap

Is there any solution to this? Should I buy Tektro to replace my old ones? Again, I am worried that new new Tektros would have the same problem if they changed at some point the standards for the brake posts/bosses some time ago

I tried them on a very old bike and looks like the same problem.


Many thanks

fietsbob

modify the boss or modify the brake..

cobba

Take the old short posts/studs off, get new longer ones and put them on.

The posts/studs should unscrew from the bosses.

Andrew R Stewart 

Not if the bike is a steel one and the very common/classic post has been braze/welded on the frame. But we don't know what kind of bike the OP has so we can't say what can or can't be done to change the post length.

To the OP's question- Some V brakes are made with their own pivot bushing internal to the post mount. So the arm doesn't need to fully slide onto the post. The post bolt will snug down against the built in bushing on the arm and all will work well. I have never seen a post bolt break other then from being over tightened. Andy.

fietsbob

One Can file the shoulder of the boss to make it 'longer', and file off some of the bushing on the brake to make it thinner..

if you can't a skilled mechanic can.

emhava

Thanks Andy, you are right in both statements. The brake posts/bosses are steel and welded. And also the V brakes have their own bushing but they have a round steel core that slides incompeletely over the brake post.

I don't think it would be safe to alter the brakes or the posts, I will get some pictures so that is more clear what I mean

Thanks guys!

Andrew R Stewart 

I've done a lot of post repairs and some brake arm bushing mods over the years as a shop wrench. Since I could, but haven't yet had to for a shop bike, be able to replace a post if I damaged it I am not worried about what I've done to them. But I've never found the need for a longer post. Sometimes the very end of the post gets a bit mushroomed from over tightening the bolt and causes some binding within the bushing. Sometimes enough rust builds up on the post to do the same. Simple shoe shinning with production cloth brings the post down to working diameters. A few times I've had to slightly shorten the arm's bushing length so the post would extend past the bushing, but again not much more then a few strokes with a file was needed. All these mods only are needed when the arm doesn't have it's own rotating bushing in it, or to say another way when the arm's brass sleeve rotates directly on the post. Never when the arm has it's own rotating bushing.

The dimensions of posts haven't changed for a few decades. During the 1970s and 1980s there were a few different lengths of post and spring capturing plates orientations but with the taking over by Asian made parts and bikes this has settled into the standard we see today. I have never seen modern posts of differing lengths, brazed on or threaded being made available.

Now if you're talking about U brake (roller cams) or direct mounted center pulls things change. But that's not what the OP is talking about. Andy.

emhava

The first one is trying to show from the side that the brake does not slide completely don the break post - I don't mind this

The second is showing what's the gap between the end of the brake post and the brake itself my worry being that the bolt might start having a play and snap one day.

Andy explained that this is not possible but don't know if is still ok with so MUCH difference

dabac

I'd be a tiny bit concerned about the brake arm not bottoming out on the base of the boss. But the boss not continuing all the way through the brake arm wouldn't bother me at all.
As it's a brake arm with an integral bushing, the pinch from the torque of the screw/bolt holding the brake arm should effectively block out any bending of the boss. (there'll be some bending stress at the base, but almost none along the length of the boss.

But I would research why it won't slide on a bit more. Is there a wider recess at the fork/frame side of the brake arm bushing that won't quite fit the wider base of the boss? Could the base of the boss be filed down(made thinner) a tiny bit to allow for a better fit?

dr1445

sorry to hijack the thread. i have a 1982 steel frame that has the spring capture located on the the outside of the frame, opposite of the op's pic which is on the wheel side or inside of the frame. any idea which brake set would fit, could be canti or v. right now i have an unknown vbrake that has the option to flip the coil spring 180 degrees, which appears to be cast not forged.

tomacropod

OP, have you actually tried fitting the thing? It will be fine, seriously. The force does not try to slide the brake off the post when you apply the lever, the force on the pads lever the caliper forwards, applying downward force on the post. The bolt will not break. If the brake pivots you're golden.

- Joel.

Andrew R Stewart 

dr1445- Your posts are one style that I was referring to, in my post #7 . I suspect that you have posts meant for either Mafac or early Dia Comp canties. Andy.

nfmisso

I would be more concerned about the first picture. I am guessing that it is hanging up on the spring, and would slightly enlarge the spring holes next to the post.

As long as the brake arm is fully seated against the post, no worries. Not fully seated is bad, very bad. A fully seated arm will transmit the forces to the base of post, as intended. Transmitting the force higher up the post can lead to post failure.

dr1445

thanks andy, the current set works but i will try ebay for a set of the mafac or early d/c cantie brakes. i do have an old set of canties maybe i will try drilling an extra spring capture hole and see what happens, for sure the new style vbrakes will not work.

emhava

Thank you kindly all for the responses and explanations, you all have been very helpful!

nfmisso

I have a Corsaro Mountaineer frame with the same opportunity My solution was to drill another hole in the body of a cantilever brake arm so that I could rotate the spring 180°. On the Mountaineer, there is not enough meat next the post to drill a hole 180° from the original. I used Amazon.com : Tektro Alloy Brake Cable Triangle w/Cable Black : Bike Brake Cables And Housing : Sports & Outdoors to make the arm alignment more reliable with the lack of spring adjustment.

dr1445

the exage canties i have do not have any adjustments for the springs. i drilled the holes in the canti lever ok, but i think i will look for a better set. thanks for the tip on the triangle.

trailangel

I had same problem changing V brakes. I put a 3/8 inch galvanized washer in between to take up the space. Drilled a small hole in the washer for the spring to go through to locating hole. It just looked better.

Also, I believe that space is there because some racks mount on the brake boss.

Alanlw

I have a similar problem. The Tektro brake has a 6mm wider collar on the pin side of the brake so slides all the way over the brake boss. The Avid brake collar is only 3mm deep so leaves a 3mm gap. So the pin is inserted 3mm less deeply into the hole in the boss as well as increasing the strain further up the post.

Brake bosses seem to be hard to come by and those I found didn't seem to show any variation in collar depth.

Are there multiple standards?

ChrisBrewer

I just tried to fit new Shimano brakes to my old Giant hybrid. Same issue.

I think the brakes that were on before were Tektro but I can't see the logos 12+ years later and anyway the ones on the rear had already been replaced with something else.

The part of the post that is wider at the base and has spanner flats to screw into the boss, is too LONG for the recess inside the Shimano brake body. So the whole thing wobbles around too much and the pin for the spring doesn't quite fit snugly.

I put the old unit back on having used the cable bits from these brakes, so sadly can't send the brake unit back. They're useless unless I find replacement bosses -- maybe useful as a spare one day.

JoeC33

I'm having the same issue trying to replace some generic v-brakes on my daughter's specialized hotrock 24. Ordered some Avid sd30s and they don't snug down all the way. I found some replacement stud posts on eBay that say they're specifically for Avid and Shimano, but for the price it's cheaper to buy different brakes. I'm probably going to bring it to my lbs and see if they have a decent solution.