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Old 11-19-11, 05:22 PM   #1
GoodShipRuffles
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Brompton Sturmey Archer 3 speed servicing

Hi,

I've been using my Brompton for daily commuting for nearly 18 months. Nothing strenuous - just 7 miles per day across London. So less than 2,500 miles.

I'm now having trouble finding low gear. Nothing wrong with the cable adjustment. Now I can strip it down (reasonable instructions here) but is it likely to have worn out at so low mileage? Is it worth stripping down or should I simply buy replacement innards. I appear to be able to do this without rebuilding the wheel.

I'm quite surprised at how much I'm spending on parts. So far I've bought 3 tyres, four sets of brake pads, three inner tubes, three right hand pedals and one chain in 18 months. So more than £150. So if the hub gear is knackered then I reckon my running costs will be approaching £200 per year! Is this normal? Dread to think how much I'd be spending if I didn't fix it myself!

Not complaint about the Brompton. Love it to bits. Just surprised at how much regular use of a bicycle costs.

Ruffles
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Old 11-19-11, 05:36 PM   #2
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Losing low is a rare failure (usually the last). To get low, the 2nd/high driving ratchet has to be disengaged. This is done by having the tips of the clutch engage a raised area on the back sides of the high gear pawls withdrawing them so they can't engage. The drive now happens via the low gear pawls on the left side of the hub.

When the clutch is a bit worn so it doesn't withdraw the pawls enough to disengage them, low and second would be the same. this is a simple, inexpensive repair involving replacing the clutch and/or (I do both) the high gear pawls.

If by losing the low, you mean that there's no drive in low (slips, no power) then the problem is that the low gear pawls are worn, dirty or gummy or that the low gear ratchet ring is worn or chipped. Then when the high gear pawls are disengaged transferring power to the low side, they slip. Usually this problem is more related to dirt or dried lube than to actual wear. Also an easy fix.

Either way, you're looking at a few easy to replace parts plus a clean and oil job, so there shouldn't be any need to replace any but the involved parts (if any).
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Old 11-19-11, 06:49 PM   #3
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Originally Posted by GoodShipRuffles View Post
Now I can strip it down (reasonable instructions here)
If the Brompton (and the hub) was new just 18 months ago, then you have the "NIG" mechanism. The correct technical info for this hub is here. Do note what it says on the "Fault Diagnosis Chart": Use this chart only if a fault persists after attention to gear adjustment, bearing adjustment and lubrication.

Quote:
...but is it likely to have worn out at so low mileage? Is it worth stripping down...?
No. Yes.

Last edited by tcs; 11-19-11 at 06:52 PM.
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Old 11-19-11, 07:29 PM   #4
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So far I've bought 3 tyres, four sets of brake pads, three inner tubes, three right hand pedals and one chain in 18 months.
I can't help with the hub, but I am curious how you went through 3 tires and 3 pedals in that time. I think I've only ever broken one pedal, and that's because it was a very old cheap pedal on my commuter that takes quite a beating. I've worn out tires before but definitely not in that kind of time span, even light weight racing tires.
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Old 11-20-11, 03:49 PM   #5
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I can't help with the hub, but I am curious how you went through 3 tires and 3 pedals in that time. I think I've only ever broken one pedal, and that's because it was a very old cheap pedal on my commuter that takes quite a beating. I've worn out tires before but definitely not in that kind of time span, even light weight racing tires.
I'm replacing the rear tyres just before the main tread disappears. The problem cycling in London is glass. I go over both tyres every couple of weeks looking for cuts. At the bottom of every cut will be a sliver of glass. Given time this penetrates the puncture proof lining. Which makes me late for work! I've only had two punctures but I'm sure I'd get more if I left the tyre to wear more.
I find the plastic on the cage pedals stretches eventually releasing the bearings. I naturally start off on the right foot - and that's a lot of starts with all those traffic lights. Without toe clips and with limited gearing I tend to start with my heel on the pedal rather than the ball of my foot. So I suspect I'm over stressing it. Mind you they're only a few quid to replace. In fact all the Brompton spares are very reasonable.
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Old 11-20-11, 03:59 PM   #6
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Originally Posted by FBinNY View Post
Losing low is a rare failure (usually the last). To get low, the 2nd/high driving ratchet has to be disengaged. This is done by having the tips of the clutch engage a raised area on the back sides of the high gear pawls withdrawing them so they can't engage. The drive now happens via the low gear pawls on the left side of the hub.

When the clutch is a bit worn so it doesn't withdraw the pawls enough to disengage them, low and second would be the same. this is a simple, inexpensive repair involving replacing the clutch and/or (I do both) the high gear pawls.

If by losing the low, you mean that there's no drive in low (slips, no power) then the problem is that the low gear pawls are worn, dirty or gummy or that the low gear ratchet ring is worn or chipped. Then when the high gear pawls are disengaged transferring power to the low side, they slip. Usually this problem is more related to dirt or dried lube than to actual wear. Also an easy fix.

Either way, you're looking at a few easy to replace parts plus a clean and oil job, so there shouldn't be any need to replace any but the involved parts (if any).
Plot thickens.
I've just changed the chain. It had stretched a little over 1/8" in 12" so I hope I'm replacing it in time. I also changed the indicator pin as a couple of the tiny links were distorted and sticking. All parts confirmed correct.
I now find something is slipping when I put a lot of pressure on the chain. Happens in all gears. Logic would suggest the chain is slipping as I've just changed it. Hard to prove though. Can't make it do it with my hand on the pedal.
I still think the hubs needs some maintenance. With second gear correctly adjusted the cable seems awfully slack in third. So I think you're diagnosis of 'gummy' is very likely!

Stop press...
I'm absolutely sure the chain isn't slipping. I can stand on the pedals and nothing moves. Only happens on the move.

Last edited by GoodShipRuffles; 11-20-11 at 05:15 PM. Reason: More info...
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Old 11-20-11, 04:02 PM   #7
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... The correct technical info for this hub is here. Do note what it says on the "Fault Diagnosis Chart": Use this chart only if a fault persists after attention to gear adjustment, bearing adjustment and lubrication.
Many thanks for the link. Looks like more than one evenings work. So I'm braving the tube tomorrow
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Old 11-20-11, 09:06 PM   #8
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Given the relative newness, Im wondering if its a cold weather and grease stiffening
is letting the pawls skip.. so, a +1 0n that.

Perhaps running some Lube oil thru the indicator chain end of the axle.
will displace the sticky grease, Or perhaps do a solvent flush.

I did this with a dry 94 UK AW3, [didn't need to flush first],
I used Phil tenacious, oil, which I had handy,
then Removed and repacked the axle bearings, them selves, with waterproof grease..
left the shell intact.

Last edited by fietsbob; 11-20-11 at 09:11 PM.
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Old 11-21-11, 08:20 AM   #9
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Fixed! And I didn't have to use the tube.

I stripped down the entire hub gear, regreased and re-assembled it. All now works fine.
As it was slipping in all gears I reckon the freewheel pawls weren't engaging. No idea why. They looked clean enough. It may be that the oil I put on the control pin has worked it's way in.

I used the pot of grease I always use for bikes. But the instructions say to use two sorts of special SA grease:

"For Bearings internal parts-SA103B
For all other internal parts-SA103A"

I suppose I need to go shopping. Will it make a difference?

Ruffles.
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Old 11-21-11, 09:47 AM   #10
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Originally Posted by GoodShipRuffles View Post
Fixed! And I didn't have to use the tube.

I stripped down the entire hub gear, regreased and re-assembled it. All now works fine.
As it was slipping in all gears I reckon the freewheel pawls weren't engaging. No idea why. They looked clean enough. It may be that the oil I put on the control pin has worked it's way in.

I used the pot of grease I always use for bikes. But the instructions say to use two sorts of special SA grease:

"For Bearings internal parts-SA103B
For all other internal parts-SA103A"

I suppose I need to go shopping. Will it make a difference?

Ruffles.
I expect it would. Gearhub manufacturers specify semi fluid grease for internal mechanisms. Regular wheel bearing grease is too thick and won't work it's way into the small parts.
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Old 11-21-11, 11:08 AM   #11
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There was a little oil cup in the S-A hubshell for decades , to add a light oil ,
at regular intervals .

then wipe it off as it seeped out.
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