Centre Pull v V Brakes

[Tiberius]

I have a bike I'm working on and it has centre pull brakes.

I've got the rear one working well, but the front one is still dodgy. Its corroded and needs new pads.

Is it worth persevering with these or changing to the more common V brakes?
Would V brake require new brake levers - isn't the travel different?

What do you think?

Nick

 

[Mussels]

You would need new levers, otherwise they will hardly work.

 

[flecc]

You may need new brake arm mounting posts as well, different lengths etc for various types and makes. That can be tricky for two reasons, getting them can be difficult, many bike outlets looking blank at their mention, and the post mounting bolts can sometimes be firmly seized in the forks.

That said I'd still prefer a V brake, especially at the front.
.

 

[wurly]

I swapped from centre pull to V brakes as soon as i'd finished making mine electric. Extra weight from the batteries eventually made it necessary. I bought a cheap 'tekro' kit from ebay (less than £15). There was enough adjustment to make the V levers fit the frame on the original mounts, but the handlebar levers (you will need for greater travel) made clearing my gearchange mechanism a problem. Finally fixed that by repositioning and 'modifying'.

Ebay
Item number: 270344554622

Looking at your picture i see no reason why these won't fit.
I'd change them, i'm sure you won't regret it.
Mel

 

[Tiberius]

Flecc, Mel,

Out of interest, why are V brakes considered better? It strikes me that the centre pulls allow lots of scope for adjusting the leverage, by altering the cable angles, etc. OK, that also allows scope for getting them wrong, and the leverage will change as the brake blocks wear.

Is there a performance difference, or is it just a question of easier to set up?

Nick

 

[Mussels]

Flecc, Mel,

Out of interest, why are V brakes considered better? It strikes me that the centre pulls allow lots of scope for adjusting the leverage, by altering the cable angles, etc. OK, that also allows scope for getting them wrong, and the leverage will change as the brake blocks wear.

Is there a performance difference, or is it just a question of easier to set up?

Nick

I think it's just a matter of efficiency. In your photo maximum efficiency is with the linking cable as straight as possible, as the cable is pulled and the blocks come into contact with the rim then the brake cable is trying to pull at an angle and is not so efficient. In V Brakes the cable is always straight between the arms and you can exert the same effort over the whole pull.
I think I could have put that a bit better, clear as mud?

 

[Tiberius]

Hi Mussels,

I think the term you are after is "mechanical advantage", what I loosely called leverage - basically the ratio between lever travel and brake block travel.

Yes, one of the things the V brake design does is to keep that relatively constant through the pull. It also doesn't change when the blocks wear and you adjust the cable to compensate.

Sounds like I've answered my own question, but is there another difference between the two types? What's the history of them? Will they fit on the same bosses on the frame/forks?

Nick

 

[Mussels]

Hi Mussels,

I think the term you are after is "mechanical advantage"

I knew that but I couldn't think of it. At least you understood what I was on about.

 

[flecc]

Sounds like I've answered my own question, but is there another difference between the two types? What's the history of them? Will they fit on the same bosses on the frame/forks?

Nick

I think the main difference is that centre pull were cheaper than the calipers that were the alternative, often seen on budget bikes. As you say, thay don't have the same mechanical advantage of some other types.

mkc1 says he was lucky enough to find that posts were ok for the ebay V brake set he bought, but quite often they don't match, different lengths etc between makes and types. One way I've dealt with this on the less critical rear brakes when they act in compression against the frame is to turn a new post and bolt straight through to the frame, securing post and brake as one. The old post thread section can be left on the frame to do that. I wouldn't advise that on forward mounted front brakes though for obvious reasons.
.

 

[wurly]

As has been explained already, it is the angle the cable pulls from. Centre pull is 90 degrees to the action of the levers. The V brake cable pull the levers together in the same plane. The handlebars levers have more travel to compensate, so it is best to get the whole kit, cables and all.

Whether the ebay ones will fit? i ordered them not expecting to have any problems....guess i was lucky (for once ). I can easily measure the relationship between the posts and the rim if you decide to get the ebay ones. I have PM'd you Nick
Mel

 

[Tiberius]

Thanks Mel,

Could you go ahead and measure them up, please. I've just looked up that ebay number you gave and at that price it would be rude not to standardise on V brakes. I probably couldn't even get new blocks for the old system for that.

Nick

 

[wurly]

Nick
I put a straight edge across the mounting bolts and measured up to the edge of the rim, where the brake blocks touch.
16mm for the rear and 19mm for the front. (Different make rims front and back). Treat those measurements as minimum, as you can see from the photo, i don't have much adjustment left.

At least this is a starting point for you.

 

[Tiberius]

Thanks Mel,

I've just been out and measured mine. I also tried trial swapping some bits around between bikes. It looks like my posts are in the right place and are the right size, thread, etc to take standard V brakes. This is suspiciously good, I'm worried. I'm sure I'll end up fabricating an adaptor.

Nick