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199a Front Brake

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Having trouble with my front brake I just can't get it to work, it has new shoes and a new cable. It looks like the the hub has already been sleeved. What I'm after is the diameter of the standard brake drum so I can check for wear, does anyone know it ??

Thanks in advance for any replies.

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125mm, if its the same as the slightly earlier Sherpas.

I got so fed up with the front brake on my 199 I ended up replacing it with a Yamaha DT/MX/YZ/IT hub. I stripped the paint off and polished it so it looks sorta-kinda like the original, but now I can stand the bike on its nose with one or two fingers; something I could never get the Bul brake to do.

Edited by oldjohn
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yes, I what you mean, we struggled all the time we had bultos put grimeca brakes in one.  ours were relined but the material was stainless steel (basically to shiney)  solved it in the end bought some large diameter cast steel pipe (schedule 80 i think).  i then machined the stainless liner out and put my non stainless liner in.  this worked well, but to completely solve the brake issue i had the shoes lined by Villiers services.  hey presto a brilliant brake that is progressive, but will stop you on a 5 pence piece if you want it to.

we also made sure all pivots and cams were in good condition and no slop in the b/plate.  

on a subsequent build, i did not want to strip the wheel to reline with cast steel, so i left the stainless liner and just used Villiers services lined shoes and this was good.

as 'oldjohn' suggests by far the easiest, most reliable and probably cheapest method is to use a different hub.

hope this helps.

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Which brake lining material did you get from VS for your Bultaco hubs, I am about to send some shoes to them.

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Don't forget to spin the wheel, lock it up and keep the pressure on the brake lever, ( snap tie ), this will centre the shoes in the hub and then tighten up the spindle and pinch bolts.

Hope this helps.

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8 hours ago, hencam said:

yes, I what you mean, we struggled all the time we had bultos put grimeca brakes in one.  ours were relined but the material was stainless steel (basically to shiney)  solved it in the end bought some large diameter cast steel pipe (schedule 80 i think).  i then machined the stainless liner out and put my non stainless liner in.  this worked well, but to completely solve the brake issue i had the shoes lined by Villiers services.  hey presto a brilliant brake that is progressive, but will stop you on a 5 pence piece if you want it to.

we also made sure all pivots and cams were in good condition and no slop in the b/plate.  

on a subsequent build, i did not want to strip the wheel to reline with cast steel, so i left the stainless liner and just used Villiers services lined shoes and this was good.

as 'oldjohn' suggests by far the easiest, most reliable and probably cheapest method is to use a different hub.

hope this helps.

Agree, the main problem seems to be the chrome drum lining used on the later bikes, along with the grey cardboard that most manufacturers pass off as lining material these days. I'm not suggesting that we return to carcinogenic lining materials but I've never found the grey stuff to perform very well in any application. Even with the Yamaha brake, it didn't achieve full power until I fitted a set of NOS factory linings - none of the aftermarket shoes came close. 

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Thanks for all the replies, not had a look at it yet but when my bits arrive from inmotion i'll drag it on to the bench and do some fettling and investigations.

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8 hours ago, trialsrfun said:

Which brake lining material did you get from VS for your Bultaco hubs, I am about to send some shoes to them.

Hi TrF, 

i went with the recommendation of Steve at VS, it is a brown material, very fibrous and has like a very thin brass weave in it.  he will know, I think he does a grey material which is slightly harder but still better than the hard, polished grey shiney $hit that comes on replacement shoes. I made an error in my calcs to Steve and given time constraints, I wanted them for the weekend and this was Thursday I had to machine them, it is a bugger to machine, nice sharp HSS lathe tool eventually did the trick.

I had the same trouble with my cub hubs in a Drayton C15 and my Whitton Hubs in a Drayton Bantam, even with new aftermarket brake shoes and the top quality Whitton hub the brakes could best be described as mediocre,  a quick call to Steve at VS and 2 pairs of shoes in the post arriving next day, before my exchange shoes and cheque could have got to him.  they are slightly more expensive than off the shelf ones that don't work but they transform the bike and give you a steady progressive brake that will bite if you want it to.   VS are knowledgeable and the service is 2nd to none

 

  

Edited by hencam
grammar and spelling
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Oldjohn,

I have a few spare IT175 front wheels(one of my favorite bikes) and would like to use one of those on my 199a.How did you secure the backing plate to the fork? The only other thing that I have not checked out are axle sizes to see if I could get the correct bearings in it for the Sherpa axle.

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I have a 199b and have recently fitted the VS fibrous , woven ,( smelly )brake shoes to front and rear.

The rear is great but I can't get the front to work past about 50% effectiveness.

The front hub even looks to have a steel liner in it, not the old chrome type.

People talk about having the shoes matched to the drum, how is that done please??

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21 hours ago, scot taco said:

Oldjohn,

I have a few spare IT175 front wheels(one of my favorite bikes) and would like to use one of those on my 199a.How did you secure the backing plate to the fork? The only other thing that I have not checked out are axle sizes to see if I could get the correct bearings in it for the Sherpa axle.

I'll put up a photo or two later. I couldn't get bearings that fit the Sherpa axle directly so ended up using ones with a bigger ID with stepped spacers that sleeve the ID down to the axle.

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4 hours ago, chappo said:

I have a 199b and have recently fitted the VS fibrous , woven ,( smelly )brake shoes to front and rear.

The rear is great but I can't get the front to work past about 50% effectiveness.

The front hub even looks to have a steel liner in it, not the old chrome type.

People talk about having the shoes matched to the drum, how is that done please??

There are a few methods. One is to have the shoes radius ground by your local brake place to match the drum diameter. Another is to chuck the backing plate with shoes attached in a lathe and turn the linings down to match the drum. You need to have the shoes shimmed out a little from the cam when you do this. Yet another old-school method was to chalk the surface of the drum then spin the wheel and apply the brakes. The chalk shows where the high and low spots are so you can then file the high spots down. If you repeat the process enough times you'll eventually get a pretty good fit.

But I've found that no matter what method you use it still takes quite a few hours of riding time to really bed them in properly on the bike. They generally improve quite a lot once they're fully bedded in.

My highly unscientific testing process consisted of riding on my concrete driveway and seeing how much pressure it took to lock up the front wheel (sitting down). I could never really get the Bul brake to fully lock even squeezing hard with four fingers. With the modified Yam brake I can lock it with two.

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4 hours ago, chappo said:

I have a 199b and have recently fitted the VS fibrous , woven ,( smelly )brake shoes to front and rear.

The rear is great but I can't get the front to work past about 50% effectiveness.

The front hub even looks to have a steel liner in it, not the old chrome type.

People talk about having the shoes matched to the drum, how is that done please??

is it a stainless liner, most that were relined by well known Bulto specialist were, as i said this was better than the useless grey linings on a stainless liner but still not great, i appreciate dismantling the wheel and machining the stainless liner out (some come out with warming to 200°c and tig tacking something to get hold of onto it) is a bit extreme but having a plain mild steel liner really does make all the difference.  a mate of mine went a step further and used cast Iron, hey presto the mutts nuts of drum brakes.  stainless is used because it is cheaper and easier to get hold of than cast mild steel tube of a similar size!

also have you replaced the brake arm with the longer clutch one?? if so my recommendation would be to swap it back for the shorter original type, as the long one flexes too much.  better still use a steel one!  sacrifice the look and lightness for something that works.

to match the shoes to the drum which i did on one set because of the error i made when giving Steve at VS my dimensions was to machine a mandrel the size of the wheel spindle place the brake plate with shoes fitted on the mandrel and skim to the correct size 125.00mm using the sharp HSS tool bit.  once at the correct size they should slide nicely into the hub.  i leave them a sliding fit no clearance as they very soon wear in!!!!

this is just my way of doing it, not saying it is correct and i am sure plenty will have a different view.

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hey Oldjohn, there seems to be a bit of telepathy going on here ......................  what are this weeks lottery numbers??

 

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A source of material for cast iron drum sleeves is cylinder liners for diesel engines. If you know someone in the engine reconditioning business they may be able to get you an old liner from a larger diesel that you could use, but even new liners aren't that expensive and one cylinder sleeve will have enough material to line a few drums.

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