Rain and the Sturmey Archer x-fdd hub brake

[chrismcg]

I've been using a Sturmey Archer x-fdd front hub brake / dynamo (that's the 70mm version) for the last 18 months and it's performed well.. except in heavy rain. 10 minutes of heavy rain and the brake stops working properly until it's dried out, which can take a day or more inside the house.

Haven't seen anyone else report this so not sure if it's a particular issue with the one I have.

I wondered if anyone else has experienced this, any potential fixes? Been wondering about whether it's possible to improve the sealing around the brake plate somehow, or otherwise protect it from the weather.

One other interesting "feature" has been the brake reaction arm clip rusting through and letting go mid emergency stop, with the loss of front braking as the reaction arm came loose.. No injuries luckily but the reaction arm now has a new clip and also *two* hose clips around the arm /fork (over a bit of old inner tube) as a backup. I do ride in all weathers and it was on its second winter, will be replacing that clip annually from now on...!

[rogerzilla]

That's what drum brakes do, unfortunately; when they get wet, they take a long time to dry out. It's usually deep puddles or fords that are the problem, though, not mere rain.

What kind of brake do you have on the back? Coaster brakes are immune to rain (except for reduced tyre grip) and discs or rim brakes generally dry out afterca couple of wheel revolutions.

[Phileas]

I use the same hub and get the same issue. When I set off the next day after a wet commute home, the brake takes a few goes before it works properly.

[cycle tramp]

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[cycle tramp]

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[cycle tramp]

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[chrismcg]

Thanks for the replies! It's not generally left standing in the rain, only ridden, so I don't think it's that it's left leaning at an angle so rain gets in that way. I've seen others say these are fairly weatherproof so I had opened it up to check nothing was forcing the brake plate out, and couldn't see anything wrong. I'd had the same thought about manufacturing variances maybe leading to a bigger gap on this particular one.

A bit of grease over the reaction arm clip sounds a good idea to slow the rust, will do that!

I have a canti brake on the back so that still works in all weathers, eventually..

[cycle tramp]

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[chrismcg]

Interesting idea! The loss of braking does always seem to coincide with having been out in heavy rain for 10 minutes or so though, so my guess would be that it's rainwater that's getting in rather than just dampness from the air.

[jimlews]

Back in the days when cars had drum brakes all round, it was the practise after traversing a ford or deep puddle, to apply slight pressure to the brake pedal ( just enough for the brake shoes to contact the drum ) to dry them out. The heat generated by friction would expel any water.
It may be worth trying similar technique with your SA. eg. As you approach your destination apply slight pressure to the brake lever until you feel a slight retardation. A couple of hundred yards of this should be sufficient.

EDIT:
BTW when were the drums last serviced ? Do the shoes need to be relined ? replaced ?

[cycle tramp]

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[LuckyLuke]

Hi, another SA drum dynamo fan here.
I have the 70mm and 90mm versions.
Have not experienced water getting inside and braking suffering yet, even on a commuter bike and an mtb that see all weathers. The commuter stands outside when at work too. I wonder if you’ve just been unlucky? Maybe a service will sort it out? Cycle Tramps’ hypothesis above re the reaction arm sounds plausible too.

Sorry to hear about the reaction arm clip failing. Could have been nasty!
I’m deffo going to check mine and start replacing periodically, ta for the idea.

Best wishes,

Luke

[Brucey]

I would favour a reaction am clip made of stainless steel or a proper braze-on.

I have used and worked on SA brakes extensively and this is only the second time that I've heard of anything getting into the hub when the bike is in use. Normally the labyrinth seal on the brake plate is enough to deter water ingress. However, if the brake plate is set slightly further to the left than normal, this would let water in more easily. It should not be possible to see any part of the brake plate OD sticking out beyond the hubshell; if the brake plate protrudes leftwards slightly, it (or the other things on the axle which determine brake plate position) may need to be machined back.

btw the FDD hub (like lots of hub generators, including all shimano) boasts a trapped volume and the best thing you can do is to add a vent. If you don't, it is probably only a matter of time (and dumb luck) until water gets into the hub bearings.

[chrismcg]

I've had a close look at the brake plate and the outside face sticks out a little all round from the hubshell, maybe 1mm, so maybe that's the issue. It looks similar to the picture cycle tramp posted above though (if less pristine!)

I'll take the brake plate off and see if it can be adjusted to sit any further in. It's definitely in need of a clean anyway and the brake pivot needs lubing too as that's sticking a bit.

Thanks for the tip on the brake arm potentially forcing it out of line - given that the brake plate doesn't stick out further at the top or bottom I don't think that's the cause of the problem in this case, but definitely worth checking.

The clip that failed was the original SA one - the hose clips are stainless but a bit of a bodge so assuming I can get the weatherproofness sorted I'll look into getting a braze-on fitted. The hub is great when the brake is working so it would be good to solve these issues!

[Brucey]

btw if you convert the brake so the brake plate 'floats' too, the brake will (IME) be better behaved and more powerful. IIRC there should be a spacer behind the brake plate; it is easy enough to SG the spacer so the brake plate can sit further in. You can always add spacers again if you overdo it. If the spacer is removed and the brake plate offered up to the hub, you may get some idea of how far you can go.