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Brake Secrets


brt650
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I have read some of the old posts about brakes and even contacted some of the members here on TT. But I haven't yet read were a Bultaco owner has brakes that work as efficiently as a Honda. I know that is upsetting , but come on how hard can it be?

Bully brakes are 125mm and my Honda has 110mm. Is it purely the lining material? Is it design? Is it mechanical leverage?

I have tried 1 Relining the brake drum

2 Bushing the cam pivot

3 Newfren shoes

4 Machining shoes to match drums

5 Centralising the backing plate when tensioning the axle

6 Venhill nylocable

7 Suzuki cam and 100mm brake arm

Someone has the secret and I want it.

Thank you for your thought's.

brt650

P.S. Don't tell the Honda riders that there brakes are better.

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I suspect that having the offset pivot ends on the Bultaco is not helpful because it twists the shoe. They make it tricky to adjust the shoes outwards too! I moved the pivot holes inwards on my M49 to move the shoes out, by making bigger holes on a new centre and fitting bushes in those holes. Lots of work compared with the more common rocking pivot design.

Also I think the material that the linings are made from is important. There is a big range of friction material in the market. One of the best I have found is whatever my local brake shop used to reline my KT250 shoes with. It works brilliantly.

Another thing is that not all Hondas have brakes that work. I rode an otherwise beautifully set-up TL125 and it had a nice solid feel to the brake lever, but absolutely no retardation. We had swapped bikes and when the other rider came back with my bike he commented on the way my brakes had worked. I don't know how he even rode that Honda in sections.

Just thought of another thing. My OSSA MAR now has great brakes after lots of attention, and there was one thing quite unusual I had to do to get them so good. The axle hole in the backing plate was not concentric with the shoe OD, and there was not enough clearance between the axle and the backing plate hole to get them concentric in service. A bit of filing to enlarge the axle hole in the backing plate was just what the Doctor ordered. Maybe some Bultaco backing plates are also not perfectly concentric?

ps your Mother is looking very good tonight

Edited by feetupfun
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Just out of interst I run a175 sherpa The front brake is great It uses Newfren linings on the original alloy drum lining If not carefull will lock up on gravel The rear is a differant story It was fitted with the same linings but on a steel lined hub The new shoes were fitted just before the MOTand if it failed on poor brakes Repaired it but they are not very good but never have been since the bike was new. I ride vintage bikes so some of there brakes are immmm I might stop

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I think it has mostly to do with the material of the brake pads the material has to be as soft as possible. As newer the pads and as more softer the material combination is as better the breaking power.

The softest brake pad material is organic the filling for organic brake pads is btw temperatur-resistant resin which will harden with the time, as harder the pad as less braking power you get. I think this is the main reason especially in combination with the chromed lining a soft brake pad workes much better then a hard one.

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From what I have read the spanish PUMA and VAZQUEZ prepared bultacos have excellent brakes, do the spanish have a different lining material or are they doing something else as they appear to be running the original hubs.

Greg

A steel insert makes somewhat of an improvement on the stock hub.

Seems to me a Yam. TY rear hub which moved the brake to the right (and sprocket on left) side thereby eliminating the crossover cable for better braking power.

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A steel insert makes somewhat of an improvement on the stock hub.

Seems to me a Yam. TY rear hub which moved the brake to the right (and sprocket on left) side thereby eliminating the crossover cable for better braking power.

I think Brian is asking about the front brake

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I think Brian is asking about the front brake

The front brake first and then I'll get onto the rear.

I did read David that you were considering the Fantic 240 shoes in a post from 2008.

(http://www.trialscentral.com/forums/topic/17506-sherpa-t-brake-shoe-pivot-arrangement/ )

Did you end up trying that? I was considering the offset anchor end maybe causing some side effects. I made a ring 125mm round and fitted over the brake to see what was happening. The shoes under varying pressure move all over the place. I believe your comments from 2008 would help alleviate this.

Cheers

Brian

P.S. Mum sends her love

Edited by brt650
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Mmmh, looked up the post from 2008

When I look at the pic's from this posting:

post-325-1201523796.jpg

I see a drum brake with pads that are not friction linings, instead sliding linings. These pads have a glazed surface by the left over/debris of brake pad material. So no wonder that they don't work properly.

Maybe this is forgotten wisdom as drum brakes on trials bikes where less and less fitted with the mid eighties ...

Drum brakes has to be maintainced regulary here:

- the hollow space,

- the pads and

- the mechanism

should be cleaned regulary from the remains of the brake pad's and other debris

as this will clogg the surfaces of the pads.

The pads of a drum brake has so much surface if you compare them to the pads of a disc brake you can't produce the same amount of pressure, (also due to the mechanical operation) and therby you have not the self cleaning effects on drum brakes as with modern disc brakes.

When you clean up the brake pads with a wire brush by hand or with a coarse abrasive cloth (again by hand) you will get a much better brake effency.

I hope this wasn't too instructive but it has to be said, regular maintaince and cleaning and you will discover a much better brake effency, even with a Bultaco.

I have ridden my SWM which has likewise drum brakes in design and performance in the Alpes and there where some really steep "downhill" sections and it worked (Not as good as with disc brakes, next time I will use a modern bike for sure ...).

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Hello David,

That would be great if you could try those shoes to see if they closely fit the Bultaco backing plate. I don't mind buying a set .I can modify the anchor end if need be.Maybe you could ask Mark to service his brakes and while there apart, see how close a fit they are.

Thanks

Brian

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SWM brake shoe also fitted

Brake Shoes EBC for Aprilia Beta Fantic SWM

[841G] pixel_trans.gif

Will fit all of the following models, where a 125mm diameter and 25mm width hub is used.

APRILIA

250 86 R

TX 125/240/311 86-88 R

ARMSTRONG

250 Trial/320 Trial F&R

BETA MODELS

124 TR 80-83 F&R

TR 125 80-83 F&R

125 TR 32/33 86-87 R

240 TR 80-83 F&R

240 TR 32 84-85 R

240 TR 33 86 R

FANTIC

50 Strada -82 F&R

50 Repl./Enduro Repl. -85 F&R

50 Enduro Compet. -82 F&R

50 Casa/Competition 75- F&R

50 Fast 88- R

80 Enduro 80- F

80 Cross Compet. -81 F&R

80 Cross Compet. 81- F

Trial 125 F&R

200 F&R

201 Monoshock 86 R

240 F&R

300 Trial R

301 Monoshock 86 R

GARELLI

Trial 320 -85 F&R

SWM

50/80 MK/GS/RBS Enduro 83- F&R

50/80 MK/MC Cross 83- F&R

125/240/320/350 HM/MWTL Trial -83 F&R

125/250 S1/S2 83- R

323 Trial 85- F&R

350 XP Sahara 83- R

Edited by b40rt
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