SA front drum brake conversion

For discussions about bikes and equipment.
nigelnightmare
Posts: 624
Joined: 19 Sep 2016, 10:33pm

Re: SA front drum brake conversion

Postby nigelnightmare » 31 Jan 2020, 11:34pm

whenever I've had a drum brake sticking on my ICE Qnt it's been the cable at fault.
Water gets in at the drum end and tends to sit in the bend (rusting or freezing).
I now lubricate with 'Silicone grease' and pack the rubber worm/cover with it.
This helps to seal the lower end of the cable & also helps to keep it lubricated every time you brake.

The 105 (5500) brake levers work fine with SA drums.

HTH

cycle tramp
Posts: 609
Joined: 5 Aug 2009, 7:22pm

Re: SA front drum brake conversion

Postby cycle tramp » 1 Feb 2020, 8:34am

nigelnightmare wrote:whenever I've had a drum brake sticking on my ICE Qnt it's been the cable at fault.
Water gets in at the drum end and tends to sit in the bend (rusting or freezing).
I now lubricate with 'Silicone grease' and pack the rubber worm/cover with it.
This helps to seal the lower end of the cable & also helps to keep it lubricated every time you brake.

The 105 (5500) brake levers work fine with SA drums.

HTH


That's good to know, I'll start greasing the cable at the start of each autumn - thanks for the advice:-)

Brucey
Posts: 36644
Joined: 4 Jan 2012, 6:25pm

Re: SA front drum brake conversion

Postby Brucey » 1 Feb 2020, 1:56pm

nigelnightmare wrote:
The 105 (5500) brake levers work fine with SA drums.


for two reasons;

a) they are not NSSLR cable pull and
b) on an ICE you effectively have two front brakes, one in each hand, each working on a small diameter wheel.

Not that you have done, but I think that you can take more liberties with brake lever MA on many tadpole trikes.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Phileas
Posts: 226
Joined: 18 Feb 2009, 6:12pm
Location: Bristol

Re: SA front drum brake conversion

Postby Phileas » 1 Feb 2020, 3:07pm

So can anyone name a currently available lever with high MA (4:1)?

I notice Dia Compe make old fashioned single pivot callipers so I assume they make a lever to suit.

Brucey
Posts: 36644
Joined: 4 Jan 2012, 6:25pm

Re: SA front drum brake conversion

Postby Brucey » 1 Feb 2020, 3:13pm

drop bar levers with exposed cables (eg dia compe) will have a high MA because they are all meant for SP calipers. Brake levers which are meant for use with first generation DP calipers (launched in ~1991 to 2008) usually work reasonably well too.

If you can lay your hands on aero levers meant for SP calipers these will also have a high MA. I quite like BL-1050 but there are others.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Phileas
Posts: 226
Joined: 18 Feb 2009, 6:12pm
Location: Bristol

Re: SA front drum brake conversion

Postby Phileas » 2 Feb 2020, 9:24am

That’s what I thought, thanks. I’ve ordered the Dia Compe 204 levers.

The issue now will be what lever to use for the rear disc brake, currently TRP Spyre but I think I’ll replace it with the BB7 from the front.

I guess I could just keep the same lever.

Edit: Actually, I guess the Dia Compe 204 will probably work ok with the BB7 anyway.

niggle
Posts: 3385
Joined: 11 Mar 2009, 10:29pm
Location: Cornwall, near England

Re: SA front drum brake conversion

Postby niggle » 2 Feb 2020, 4:05pm

Is there a way to measure the MA of a brake lever? I would like to know what it is for my RL340s, but can't seem to find out.

Brucey
Posts: 36644
Joined: 4 Jan 2012, 6:25pm

Re: SA front drum brake conversion

Postby Brucey » 3 Feb 2020, 2:31pm

niggle wrote:Is there a way to measure the MA of a brake lever? I would like to know what it is for my RL340s, but can't seem to find out.


measure distance A from the pivot to the place where your fingers sit when you use 'two finger ' braking. Then measure distance B from the pivot to the cable anchorage. If distance B varies with lever pull, measure it when the brake is 'on', along a line perpendicular to the cable itself.

Divide A by B. IIRC RL340 levers should be about 3.5:1 MA.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

alexnharvey
Posts: 890
Joined: 10 Jan 2014, 8:39am

Re: SA front drum brake conversion

Postby alexnharvey » 5 Feb 2020, 7:53pm

What do you all think about compressionless outer for the brake cable and any ideas on good rims to pair with the drum brake.

Possibly the recent thread on mid-weight tourer rims covers it, Shruti of course a 'disc-only' rim could be used instead.

Brucey
Posts: 36644
Joined: 4 Jan 2012, 6:25pm

Re: SA front drum brake conversion

Postby Brucey » 6 Feb 2020, 2:24pm

compressionless outer cable is a good idea but the mechanism itself inside the drum is inherently slightly spongy anyway, so I'm not sure how much real benefit you might get that way.

One of my mad ideas is to make longer brake arms to fit SA drum brakes and then to use V-brake levers with them, keeping the system MA the same. However this again won't realise much benefit if the cable is not the source of friction/sponginess.

Rim-wise almost any rim ought to work OK. A caveat to this is that in the rear hubs meant for derailleur gears the dish in a brake hub (e.g. X-RD or X-RDC) wheel is pretty massive, and that means that the LHS spokes tend to slacken themselves in service unless locked in position. This happens more easily if the rim isn't super-stiff.

Basically very few disc brake hubs have flanges as large as the SA hub brakes, and this means that the extra spoke loadings (arising during braking) are always going to be less than in a disc brake hub. So pretty much any rim that is disc-brake compatible is also going to be OK with a SA brake. However this is of limited helpfulness, seeing as many disc brake rims are not available in 36 drilling, which is how SA brakes usually come.

FWIW I have built aluminium SA hub brakes into wheels with rims as narrow/light as 440g/13C and up from there. Asides from the spoke slackening/dish issue mentioned above I have not had any real problems. However the steelite type hubs can suffer flange warping during the build if the tension is too high/too uneven.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Phileas
Posts: 226
Joined: 18 Feb 2009, 6:12pm
Location: Bristol

Re: SA front drum brake conversion

Postby Phileas » 6 Feb 2020, 5:27pm

I built mine into a Ryde Andra rim which is disc only.

niggle
Posts: 3385
Joined: 11 Mar 2009, 10:29pm
Location: Cornwall, near England

Re: SA front drum brake conversion

Postby niggle » 6 Feb 2020, 7:35pm

I used compressionless housing for my SRAM rear drum brake and it reduces the sponginess but no real benefit other than feel, unlike wIth mini v-brakes where it allows a bit extra rim clearance due to reducing the spongy lever travel. Also good with mechanical disc brakes IME.

Des49
Posts: 645
Joined: 2 Dec 2014, 11:45am

Re: SA front drum brake conversion

Postby Des49 » 6 Feb 2020, 9:48pm

Is a Shimano V-brake lever ok for a SA drum brake?

I have recently purchased one with a dynamo to build up for someone. The bke currently has I think Shimano LX V-brakes, it would be nice to keep the same lever.

niggle
Posts: 3385
Joined: 11 Mar 2009, 10:29pm
Location: Cornwall, near England

Re: SA front drum brake conversion

Postby niggle » 6 Feb 2020, 11:28pm

Couple of reasonably priced disc rim options for 700c 36h here, though only single eyelet: https://www.taylor-wheels.com/bike-part ... d_loch=333

niggle
Posts: 3385
Joined: 11 Mar 2009, 10:29pm
Location: Cornwall, near England

Re: SA front drum brake conversion

Postby niggle » 7 Feb 2020, 11:29am

Des49 wrote:Is a Shimano V-brake lever ok for a SA drum brake?

I have recently purchased one with a dynamo to build up for someone. The bke currently has I think Shimano LX V-brakes, it would be nice to keep the same lever.

I think not, unless your levers have an adjuster in them that will let you change between v-brake and canti/roller brakes pull. Best IMO would be the genuine Sturmey Archer levers: http://practicalcycles.com/products/233 ... canti.aspx or something else designed for traditional side pull calliper or canti brakes like http://practicalcycles.com/products/334 ... ebars.aspx or http://practicalcycles.com/products/233 ... evers.aspx

EDIT: Sturmey also do a parking brake version: http://practicalcycles.com/products/107 ... lever.aspx