Hub Drum Brakes

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fausto99
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Hub Drum Brakes

Postby fausto99 » 1 Aug 2018, 8:20am

Have built up a pair of wheels with brand new S-A hubs with drum brakes. Tried out the bike yesterday and so far am not impressed with the brakes. They come on far too slowly - just like wet rims, in fact! Exactly what I wanted to avoid for a winter bike.

As they're brand new, should I take the hubs apart and rough up the braking surfaces?

Greystoke
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Re: Hub Drum Brakes

Postby Greystoke » 1 Aug 2018, 9:36am

See the supercommuter thread

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fausto99
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Re: Hub Drum Brakes

Postby fausto99 » 1 Aug 2018, 5:13pm

Greystoke wrote:See the supercommuter thread


Searched this forum for "supercommuter" - zilch. Could you post a link please?

Brucey
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Re: Hub Drum Brakes

Postby Brucey » 1 Aug 2018, 5:17pm

if you are looking at this forum in 'recent postings' view, the supercommuter thread is currently about 15 down on the first page.

cheers
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gaz
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Re: Hub Drum Brakes

Postby gaz » 1 Aug 2018, 5:30pm

fausto99 wrote:Could you post a link please?

Link.

cycle tramp
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Re: Hub Drum Brakes

Postby cycle tramp » 1 Aug 2018, 7:09pm

fausto99 wrote:Have built up a pair of wheels with brand new S-A hubs with drum brakes. Tried out the bike yesterday and so far am not impressed with the brakes. They come on far too slowly - just like wet rims, in fact! Exactly what I wanted to avoid for a winter bike.

As they're brand new, should I take the hubs apart and rough up the braking surfaces?


Personally i wouldn't worry.... i'd just try and use the bike as much as possible..... drum brakes get better the more miles they do.
Other than that, what brake levers and cables are you using?

PT1029
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Re: Hub Drum Brakes

Postby PT1029 » 1 Aug 2018, 7:42pm

In my experience, drum brakes - even when they work well - come on in a slightly liesurely way, no instant grab like you might get on some other brake types.
As cycle tramp says, check the other bits. A draggy cable can lose you a lot of braking power, checking for a quick release when you let go of the brake lever isn't a very good test here, as drum brakes often have quite strong release springs that over come a draggy cable.
Definately check you are not using brake kevers designed for V brakes or ATB disc brakes, V brake levers have a lower mechanical advantage compared to levers designed for drum brakes/cantilever brakes and the rest, putting you on a losing streak from the start.

Brucey
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Re: Hub Drum Brakes

Postby Brucey » 1 Aug 2018, 8:14pm

PT1029 wrote:In my experience, drum brakes - even when they work well - come on in a slightly liesurely way, no instant grab like you might get on some other brake types....


before they are bedded in, they can be like this. After they have been bedded in, as common a complaint is that the brakes are a bit grabby, and the shoes need to be chamfered to reduce the intitial bite.

Unless you are riding often on slippery surfaces, and think you might want to use the front brake thereon, there is arguably a good tolerance to high initial 'bite'. I find that in an emergency, with well set up hub brakes, I can stop more quickly than with pretty much any other kind of brake; they can be such that they won't quite manage a stoppie, which means you can apply them fully, instantly, knowing you won't go over the bars.


As per the above post (and as detailed elsewhere), the brakes will be rubbish if you use V-brake levers with them; you need to use brake levers that pull a smaller amount of cable with higher force.

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fausto99
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Re: Hub Drum Brakes

Postby fausto99 » 1 Aug 2018, 10:11pm

cycle tramp wrote:Personally i wouldn't worry.... i'd just try and use the bike as much as possible..... drum brakes get better the more miles they do. Other than that, what brake levers and cables are you using?


I'm using new Shimano BL-R400 levers atm. The front cable is the SA cable that came with the rear hub, shortened, with the barrel end cut off (so I could thread it through the lever and the the shortened outer) and a SA solderless barrel nipple. The rear cable is one of the ones that came with the levers (pear end) + a SA long adjuster and solderless barrel nipple
Last edited by fausto99 on 1 Aug 2018, 10:17pm, edited 1 time in total.

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fausto99
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Re: Hub Drum Brakes

Postby fausto99 » 1 Aug 2018, 10:16pm

Brucey wrote:before they are bedded in, they can be like this. After they have been bedded in, as common a complaint is that the brakes are a bit grabby, and the shoes need to be chamfered to reduce the intitial bite.

Unless you are riding often on slippery surfaces, and think you might want to use the front brake thereon, there is arguably a good tolerance to high initial 'bite'. I find that in an emergency, with well set up hub brakes, I can stop more quickly than with pretty much any other kind of brake; they can be such that they won't quite manage a stoppie, which means you can apply them fully, instantly, knowing you won't go over the bars.


Thanks for that. I personally like a high initial bite - I'll look forward to it developing. ATM it feels like rubber blocks on chromed steel rims on a wet day. I'll go and try the local long downhills.

alexnharvey
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Re: Hub Drum Brakes

Postby alexnharvey » 2 Aug 2018, 10:04am

Which levers are you using?

Brucey
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Re: Hub Drum Brakes

Postby Brucey » 2 Aug 2018, 10:37am

BTW the SA cables have one major flaw; they are usually utterly devoid of any lubricant and this often causes the brakes not to work that well. If you are using a solderless nipple at one end, you can pull the inner and lube the cable properly before the solderless nipple is fitted. However once the nipple is fitted, the cable end is so kinked it will not be possible to re-feed it into the housing unless it is trimmed. So if you have not lubed the cables yet, at least one new inner is required (the rear can be shortened and used at the front).

If the cables are used on flat bars, they can be left double-ended. To lube them you need the patience of a saint (dribbling oil in from one end) or to use a hydraulic cable lubricator.

The SA cables, once lubed, are OK; good enough, but nothing special. You can do better with a polished stainless steel inner and careful lubrication.


The BL-R400 levers should be OK but you may get more power yet from slightly older levers that were meant for use with SP brakes; these often have a slightly higher MA value. Probably best to wait until the brakes are bedded in first.

If the brakes are bedded in over a short period, it is possible for brake dust to build up more than normal inside the drum. Normally it comes out as fast as it is generated, but only up to a point. If you get a dust build up, the brake plate can be removed for cleaning. [NB modern SA brakes use linings that merely generate a nuisance dust. However older ones (pre 1970, maybe a bit later than that) contain asbestos; approach with caution.]

Once the linings are bedded in, the brake can usually be adjusted so that the linings run very close to the drum surface without any rubbing. This means that even with levers that pull the least amount of cable, you are in little danger of pulling the lever back to the handlebars, and a higher MA could be used. This being the case, it would be simple enough to trade the brake arms (on the brake plate) for longer ones; they just unbolt. Longer ones are not available to buy, but could easily be made by extending standard ones.

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fausto99
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Re: Hub Drum Brakes

Postby fausto99 » 2 Aug 2018, 2:07pm

Brucey wrote:BTW the SA cables have one major flaw; they are usually utterly devoid of any lubricant and this often causes the brakes not to work that well.


I used "Rock N Roll Cable Magic" lubricant as I was re-assembling inners to outers. Many thanks for all the useful info re bedding-in. I do so hope it improves.

I won't be able to try anything for a while as I'm waiting for the rapidfire clamps to come back from being turned out to fit the bulged centre section of my drop handlebars (I have a fellow biking friend who has a lathe).

If It doesn't work out or I don't like it, I'll re-think and probably get some 8-speed sti levers. I'm trying this out, for the moment, as I quite like the existing rapidshift thumb shifters and I had a set of brand new BL-R400 levers left over from some other project.

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fausto99
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Re: Hub Drum Brakes

Postby fausto99 » 2 Aug 2018, 2:13pm

One other thing about hub drum brakes. I don't like the way the rear reaction arm has to be bolted to the chainstay with a clip. The front arrangement where the reaction arm slides into a slot on the fork clip is much better. I'm going to see if I can duplicate that arrangement at the rear (the frame has vertical drop-outs).

Brucey
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Re: Hub Drum Brakes

Postby Brucey » 2 Aug 2018, 3:58pm

the only thing is that chainstays are more nearly -if not actually- parallel-sided, unlike most forks. This means that a clip which has a slot in for the reaction arm could (if it loosens) slide along the length of the chainstay, leaving you with no rear brake, or more likely, a brake that spins round the first time it is used, pulls ever harder on the cable, and locks the wheel.

The same thing isn't likely to happen at the front; if the clip should comes loose it can't very well slide up the fork, because of the taper, and in fact gravity will tend to pull it downwards, a direction it can't go far in because of the step on the tang. When setting the height of the front clip, set it as low as possible; this will enable the tang to be started in the clip before the wheel enters the dropouts, greatly easing refitment of the wheel.

So at the rear you can have tang into a slot provided there is absolutely no chance of the clip moving. A braze-on for the slot is probably best. There are other schemes involving a clip with two bolts in, and/or a slotted (keyhole slot) brake plate such that the reaction arm is secured In a tool-free fashion.

cheers
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