Odd V-brakes how do you set the tension evenly

[TechnoTim2011]

I have been lent a bike, it is apparantly a Raleigh M-TRAX mountain bike of late 1990's vintage. The deal is that I fix the lendors Apple Mac G5 in return. But the bike needed some TLC.

Degreasing cleaning and reindexing the gears was straightforward. But the brakes were odd.

We took both front and back V-brakes off the cables were all in good nick but these are unlike any V-brakes I have seen before. there is no tension adjustment screw and the tension spring sits in a kind of lug that does not locate in any of the holes in the braze-on fittings on the frame.
Photo from this angle and from this angle

and

from another angle

The only way tension it is to get an adjustable wrench and hold the lug (angled downwards on the photos) at an angle and tighten the brake actually slides on. But getting both sides the same seems to be impossible, symmetrical doesn't work and because it springs back wen the allen screw in the centre of the brake pivot is released it seems to be all luck rather than judgement.

I am going to replace this brake system with shimano acera when funds allow, but right now I want to ajust them properly.

Can anyone point to a service manual/howto/tutorial or otherwise advise.

 

[RecordAceFromNew]

Someone might well come along with a much better idea, but whatever tensioning mechanism a V brake has ime the easiest way to roughly equalise tension on both sides initially is to firstly unclamp/loosen the noodle so that each side can move independently, before setting the tensioning mechanism (e.g. the usual choice of 3 sockets on frame, plus screw, which in your case seems to be just a lug) by making tension at each arm at the equivalent point on the top of the arm the same by feel with the finger.

In other words I think it is impossible to assess each tension when the arms are coupled, but relatively easy to assess and roughly equalise by feel when they aren't. However adjusting the tensioning screw* (if there is one, which sadly doesn't seem to be the case here) is certainly the usual way to fine tune towards the same 2mm target gap between pad and rim on each side (when the tensions are roughly equivalent).

Unless I have misunderstood it completely, once tension on each side is about right by feel it seems you will have to make fine adjustment by remembering what angle the lug is at and correct it incrementally by increasing/decreasing the angle.

* the tensioning screw (in your case perhaps the lug too) is also much easier to adjust with the noodle disengaged, because the screw is in compression otherwise.

 

[Zoiders]

I have a suspicion as to how they tension, I think the little tab sticking out moves around and drops onto the correct pin hole to let you preload them without unbolting the arms, I don't think you have to mess with the springs in the arms.

That washer with the tab on, see if you can compress it toward the boss.

 

[TechnoTim2011]

I have a suspicion as to how they tension, I think the little tab sticking out moves around and drops onto the correct pin hole to let you preload them without unbolting the arms, I don't think you have to mess with the springs in the arms.

That washer with the tab on, see if you can compress it toward the boss.

After a 14 mile ride to luvverly pub in the countryside, I met someone who told me the secret. These were the first generation of v-brakes and the whlle it would seem reasonable to judge whether the tension on both sides is the same and then set the brakes, the real issue is that the springs in the assembly tension at different rates, they may start the same but will change over time. What this means is that you get good tension on one side and try and get the same tension on the other but when it all is reconnected it doesn't work, the fix is to relieve some of the tension on the first side to compensate for deterioration in tension on the other side. This is in some ways counterintuitive, Ths spring on the second side will never hold the same tension as the first side because it has deteriorated.

Gold star to bloke down pub I reckon.

Oh he was riding a Cube full suspension (he came accross the fields)

Cheers for all your input anyway.

 

[Zoiders]

After a 14 mile ride to luvverly pub in the countryside, I met someone who told me the secret. These were the first generation of v-brakes and the whlle it would seem reasonable to judge whether the tension on both sides is the same and then set the brakes, the real issue is that the springs in the assembly tension at different rates, they may start the same but will change over time. What this means is that you get good tension on one side and try and get the same tension on the other but when it all is reconnected it doesn't work, the fix is to relieve some of the tension on the first side to compensate for deterioration in tension on the other side. This is in some ways counterintuitive, Ths spring on the second side will never hold the same tension as the first side because it has deteriorated.

Gold star to bloke down pub I reckon.

Oh he was riding a Cube full suspension (he came accross the fields)

Cheers for all your input anyway.

A lot of canti-levers work that way and so do some early V's, it's no secret.

The V's you have have some other feature though, most canti's and early V's had an adjuster screw on just the one side and yes you would have to tweak the spring on other side to balance them but I don't think that's he case with ones you have.

Back the main bolts out, have a look at the springs and the brake boss pins and see how they go together, it doesn't seem to be the same as bog standard canti's or early V's on what you have.

 

[TechnoTim2011]

A lot of canti-levers work that way and so do some early V's, it's no secret.

The V's you have have some other feature though, most canti's and early V's had an adjuster screw on just the one side and yes you would have to tweak the spring on other side to balance them but I don't think that's he case with ones you have.

Back the main bolts out, have a look at the springs and the brake boss pins and see how they go together, it doesn't seem to be the same as bog standard canti's or early V's on what you have.

Done that, stripped it down and checked and regreased it all.

You are right, there is no tension adjustment screw. Adjustment is apparantly a two man job, 1 to squeeze lever so pads hit the rim then one to loosen bolt and pull lug down with pliers or wrench to get tension on one side retighten bolt, then repeat other side and repeat until even. This is way more fiddly than either cantis or normal v-brakes. The concept of balancing the springs seems sound enough to me though and I will test it and report back

This brake system defeated the lendor who has built 2 bikes and owned scores and bamboozled me and a mate (I built my first bike in 1980) I can see why.

Cheers for your input

 

[TechnoTim2011]

Bloke in pub was quite right, reduced the tension on the chain side and this evened up the tension. The v-brake now pulls on both sides much more evenly.

I am still going to change these brakes when funds allow to a more modern Shimano Acera.