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Brake Secrets


brt650
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A deep clean and roughten surfaces of the pads will help. Using new and soft pad material will help again.

BUT ... it's a drum brake and will be a drum brake in future.

Any drum brake is in comparison to todays disk brakes not efficient.

You might look up test from the past were these bikes where brand new, there where no complaints about the brakes back then, (I keep this in mind too).

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hello pschrauber,

I don't doubt what you say , but I have a drum brake Honda and it;s very good.

There are other's that would back me on that. And it's 110mm in diameter and the bully is 125mm. Doesn't make sense.I'm still going with David on this one and pursue the Fantic shoe/anchor design. I'll keep you posted.I think maybe the riding style in twinshock is different here to what they do in England. We don't have flowing as much , as stop and attack an obstacle. Much like modern style riding is.But a long way away from that.If you watch the guy's on Honda's at our club days at what they can do with there brakes that work. It would nearly make you think about changing brands. Heaven forbid.

Thanks

brt650

Edited by brt650
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Mmmh ... It is possible to lock the rear and front wheel while riding on the road, but I need a lot of power to do so.

I have new pads mounted, the pad linings are centred and the chrome surface inside the hubs are in a good shape?

The brakes have long steel brake arms mounted, on the rear and front brakes, they were mounted by Bultaco, (Bultaco design but made out of steel, not alloy! Probably because of road registration):

(Even back then the brakes must had the possibility to lock the wheel as a part of practical testing the suitability of vehicle registration here in Germany).

Then I use new cables on the rear and front brake with oversized innercable to avoid any streching under load of the cable, (made by O. Colander).

Rearbrake foot lever is the original for the 199b made out of aluminium, a little bit thicker and shorter as the one for the former 199a.

Frontbreak hand lever is standard.

Edited by pschrauber
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I had a bult and the front brake was excellent. It had new shoes and a cast iron liner. I now have another bult with the original chrome plate and it is nowhere near as good.

I think you need to get the cast iron liner to get a high performing brake.

I also rode at a trial with ex world champ Mr Vesterinen recently - I noticed his front brake arma was longer than standard - looked about 1" longer - I guess this would give more force on the cams/shoes at the expense of a spongy feel mayeb..

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Just fitted over size shoes from Villiers Services to my Cota 200, as the drum measured nearly 126mm rather than 125mm (I should have had a new liner fitted before I had the wheel rebuilt!!),

Any way the new shoes fitted just a but too snugly so I machined a tiny bit off them and all looks fine, an initial test seemed good easily locking the front wheel on wet block paving with out any bedding in. The real test will be when they are fully wet!!!

I think what helps is that the shoes are a very close match to the drum diameter and the linings are a soft trials specific lining.

I normally use a longer arm but due to the tightness of the new shoes I couldn't get the cable to reach but all works well with the standard arm.

I have been using EBC pads and have only swapped cos I have ran out of adjustment, the standard brakes work fine in most sections and very rarely cost me marks.....I must be thinking ahead!!!!!

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May be some older motorcycles have a brake cam issue and the brake cams are not working properly any more due to wear.

As one side of the pads is always leading the other trailing in connection with the direction of rotation of the front wheel.

The term "leading/trailing" ("auflaufend/ablaufend" in German) is used for drum brakes.

One brake shoe is "leading", which means moving with the direction of rotation of the drum and thus exhibiting a self-applying, or self-servo effect, which means being dragged into the friction surface of the drum and therfore producing a greater braking force.

The other shoe is "trailing", moving against the direction of rotation, being thrown off the friction surface of the drum and not retarding the drum quite so effectively.

If the brake came is bend or the shaft / cam bearing worn or the bearing surfaces worn out the brake will have less breaking power too. You can test this by mounting the brake cam 180° turned around.

You can too force the breaking power of the leading shoe by grinding off a little bit of the brake cam side that is actuating the brake shoe that is trailing while the wheel is moving forward. Then more breaking power will be transferd to the leading shoe and produce a greater braking power. But then you will loose a lot of breaking power while going backwards.

(I will not recommend this because this is not road legal, (this is often discussed by German MZ riders)).

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OK Mark brought over the SWM TL320 front shoes tonight. They are pretty close but some issues were visible comparing the shoes side by side. It looks like the PCD of the shoe pivot and camshaft centres on the backing plate are slightly different with the SWM centres being slightly closer to the axle. It also looks like the SWM cam is a different thickness to the bultaco cam. It would be pretty easy to get the pivot end of the shoes to fit, and get the pivot centre of the shoes in the right place at the same time. I might be able to get a bit more info by trying to fit them to the Bultaco but that will be a job for Later Ron - probably next weekend

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OK Mark brought over the SWM TL320 front shoes tonight. They are pretty close but some issues were visible comparing the shoes side by side. It looks like the PCD of the shoe pivot and camshaft centres on the backing plate are slightly different with the SWM centres being slightly closer to the axle. It also looks like the SWM cam is a different thickness to the bultaco cam. It would be pretty easy to get the pivot end of the shoes to fit, and get the pivot centre of the shoes in the right place at the same time. I might be able to get a bit more info by trying to fit them to the Bultaco but that will be a job for Later Ron - probably next weekend

Thank you David and Mark for your efforts so far. I'll wait if you don't mind David, till you have tried them on your backing plate.

When you sit the shoes into the brake drum , can you measure the gap at the cam end please? When the shoes are butted together at the anchor end.

Thanks again

Cheers

Brian

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Thank you David and Mark for your efforts so far. I'll wait if you don't mind David, till you have tried them on your backing plate.

When you sit the shoes into the brake drum , can you measure the gap at the cam end please? When the shoes are butted together at the anchor end.

Thanks again

Cheers

Brian

Will do

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Here are the SWM shoes in the front drum of my M198. This drum has just been resleeved and then machined to standard diameter.

I took two photos - one as Brian asked for with the pivot ends touching and in that position the cam followers are not parallel and are 16mm apart at the narrowest part.

The other photo is with the same SWM shoes held so the faces of the cam followers are parallel with each other

In case anyone is wondering no they are not my hands in the photos

post-325-0-99559800-1355387422_thumb.jpg

post-325-0-03384700-1355387632_thumb.jpg

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Brakes

As you have said earlyer the secret is buy the HONDA as i can lock my frount and back wheel with its brakes but it will be interesting to see how the Monty brakes match up when i finish rebuilding the 247 cota over christmas

Part of the fun is droping off a bank and guessing if you will stop in time to turn before you hit the tape, unless you ride a honda then you know you will stop

keep up the tinkering as i may need help with the monty brakes :xmas:

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