Brakes are not working - help

[Ainsley]

I'm almost finished restoring my Sherpa T 250 circa 1966.

New rims, new tyres, new spokes.  Just had new brass bushings put in the brake plate.  New shoes, new cable inner and outer.  Brake arm works fine, shoes contact the inside of the drum fine.

However, with the brake lever fully pulled I can still roll the bike forwards.  Oddly it locks up the wheel if I pull the bike back, but forwards no chance.

Stopping would be nice before I attempt to ride the bike.  Has anyone some suggestions to what I can do next to make it work ?

 

[timdog]

One of the ways to centre the brakes is to leave everything finger tight then pull brake lever. Hold it on then tighten up spindle etc. 

I always have break shoes relined by villiers services using a much softer compound. Makes a big difference, order online its not expensive.

[Ainsley]

Ah, that's a good idea.  I will give them a call.  Thanks

[woody]

When you say the shoes contact the drums fine, how much contact is there. Usually with EBC or Newfren etc  you get minimal contact around the pivot but not much else. Oversize linings machined down to fit snugly in the hub give almost full contact and there are different materials to choose from. As above Villiers Services can reline old shoes to whatever thickness you want, as do Saftek

[Ainsley]

I'm not completely sure how much contact there is.

However I suspect the real issue is that my hubs don't have a proper lining, they were just chromed and that's long since worn out.  Apparently even when they were new they were rubbish.

So I will get them relined properly then get some higher friction shoes.  Everything else is good / new / refurbished.  Shame, as the wheels have just been laced up with new spokes and rims.  I will have to have that done again, but basically without working brakes there is no point riding it.  I will speak to Villiers and Saftek and see who can sort me out the fastest.  Its so close to being fully renovated and now the sun is out I'm desperate to ride the bike now.

[motovita]

52 minutes ago, Ainsley said:

I'm not completely sure how much contact there is.

However I suspect the real issue is that my hubs don't have a proper lining, they were just chromed and that's long since worn out.  Apparently even when they were new they were rubbish.

So I will get them relined properly then get some higher friction shoes.  Everything else is good / new / refurbished.  Shame, as the wheels have just been laced up with new spokes and rims.  I will have to have that done again, but basically without working brakes there is no point riding it.  I will speak to Villiers and Saftek and see who can sort me out the fastest.  Its so close to being fully renovated and now the sun is out I'm desperate to ride the bike now.

 Back in the day the local Bultaco dealer turned and relined the drums without removing the rim. I think he even did it with a tire in place.

[Ainsley]

Ah, well that would be good. I will see if that's possible now.

[woody]

3 hours ago, Ainsley said:

I'm not completely sure how much contact there is.

However I suspect the real issue is that my hubs don't have a proper lining, they were just chromed and that's long since worn out.  Apparently even when they were new they were rubbish.

So I will get them relined properly then get some higher friction shoes.  Everything else is good / new / refurbished.  Shame, as the wheels have just been laced up with new spokes and rims.  I will have to have that done again, but basically without working brakes there is no point riding it.  I will speak to Villiers and Saftek and see who can sort me out the fastest.  Its so close to being fully renovated and now the sun is out I'm desperate to ride the bike now.

The hubs on yours weren't chrome lined assuming the  wheels are the originals, they are just normal liners, chrome came around 1972. If the chrome is in good condition the brakes work fine with modern shoe linings

Easy to determine contact patch, just ride around with the brakes hard on and see the rub marks on the shoes. It's a lot less expensinve to get some oversize shoes and turn them down and try them before having hubs relined for no reason

[Ainsley]

I'm not sure my wheels are originals.  They don't have any liners in them.  Im assuming the lining will be very obvious when looking. 

I think they are from possibly an M80 model, as that's the frame my M27 engine is in.

The hubs inside just look like bear metal, that perhaps was chromed once.  

[feetupfun]

On 5/16/2023 at 2:22 AM, Ainsley said:

I'm almost finished restoring my Sherpa T 250 circa 1966.

New rims, new tyres, new spokes.  Just had new brass bushings put in the brake plate.  New shoes, new cable inner and outer.  Brake arm works fine, shoes contact the inside of the drum fine.

However, with the brake lever fully pulled I can still roll the bike forwards.  Oddly it locks up the wheel if I pull the bike back, but forwards no chance.

Stopping would be nice before I attempt to ride the bike.  Has anyone some suggestions to what I can do next to make it work ?

 

Model 27/49/80 brake hubs are cast aluminium with a cast iron friction surface. The front 27/49/80 hub also has equal diameter spoke flanges. There are many things you can do to make the brakes work very well. As you already have mentioned that some of them have been done, here are other things that are important.

Wheel bearings have no play.

Drum friction surface is smooth (not grooved), parallel (not tapered) and round. Bikes that old usually are woeful in these areas unless the drum has been re-machined or resleeved.

The friction material is of a modern high friction type, available from specialist shoe relining people. A thinker lining than off-the-shelf shoes have is usually required to achieve a big enough diameter for the lining OD on the backing plate to match a worn or remachined drum.

I'd be surprised if the radius of off-the-shelf new brake shoes matches the drum curvature of such an old bike, unless the drum has been releeved back to original diameter. If you can pull the lever all the way in, then a likely cause of this is that the radius of the linings does not match the curvature of the drum. The springiness that allows you to pull the lever in is probably the shoes being flexed away from their relaxed shape. This flexing may well provide a contact witness on the shoes but makes the brakes useless.

So my suggestion is to have the drum machined smooth and parallel and the shoes relined thicker and machined back to match them to the new drum diameter.

[b40rt]

A magnet will tell you if the lining is steel.

[Ainsley]

Ah, good point about a magnet.  Will try that later.  

Wheel bearings are new, no grooves in the drum, but it is worn.  The new rear shoes hardly touch the drum.

I will find someone who can re machine the drums and see what they reckon, either re machine + thicker shoes or re line them.

I spoke to Villiers Services and he recommended someone in / near Kidderminster who relines / re machines hubs, apparently he is a Bultaco fan.  Anyone know of him ?

[b40rt]

Inmotion Bultaco used to do this, might be worth giving them a call.

[Ainsley]

Yeah, I spoke to them, they don't do that service, but have been very helpful.  They told me that the chromed hubs when the bikes were new were rubbish, so suggested re machining / lining.  I'm off to take the hubs to some bloke up near Bewdley who can sort them.  After I've removed the rims and spokes

[b40rt]

There is a guy Bill ? that can do this with the wheel complete, someone will chime in with his contact details.