Grumbling Brompton "freehub"

[wafter]

I've noticed some roughness and noise when freewheeling on the (6sp) Brompton. This happens in all of the three hub gears so I assume is something to do with the freewheel setup.

I was under the impression that these had some weird dual-freewheel setup whereby this facility exists in both the hub and a freehub onto which the sprockets are fitted - can anyone please confirm that this is correct?

I'm reasonably happy stripping / inspecting / cleaning / relubing a freehub; less-so the 3sp hub itself...

Any resources on this would be much appreciated

Ta!

 

[gom]

It is my understanding & experience that S-A hubs are just noisy, and maybe do sound as if all is not well. The three ratios may sound different to each other, but none is silent when freewheeling. I fairly recently got a new 6-speed, replacing an old 5-speed, and feared something was up, but I had a service and advice (from a shop other than where it came from) and am assured all is fine.

 

[wafter]

It is my understanding & experience that S-A hubs are just noisy, and maybe do sound as if all is not well. The three ratios may sound different to each other, but none is silent when freewheeling. I fairly recently got a new 6-speed, replacing an old 5-speed, and feared something was up, but I had a service and advice (from a shop other than where it came from) and am assured all is fine.

Thanks - when I first got the bike I was startled by all the noise coming from the back whilst pedalling, however having covered about 5.5k miles on it now I'm pretty accustomed to these.

What I'm referring to however sounds / feels decidedly different with a roughness being transmitted through the pedals when coasting / back-pedalling. It feels like roughness in whatever bearing allows the wheel to rotate relative to the drive input, rather than the usual noise from the pawls when pedalling in 1st or 3rd. It's only detectable when coasting and (with the exception of the distinctly different clatter from the pawls) is absent when pedalling.

I'm surprised there's not more on this tbh; although I'll do a more generic search for SA hubs rather than Brompton-specific items. I would like to strip, clean and re-grease it given the distance it's covered; however this seems like a pretty daunting task and I'd prefer to wait until it's out of service as the daily commuter..

 

[Kell]

The wheels use cones and bearings. It's possible that if you've removed the wheel at some point then these have got over-tightened or worked too loose and you're getting the grumbling because of that.

 

[wafter]

The wheels use cones and bearings. It's possible that if you've removed the wheel at some point then these have got over-tightened or worked too loose and you're getting the grumbling because of that.

Thanks - are you able to expand on the bearing arrangement at all? I don't think it's a problem with the "main" wheel bearings as it's only present when coasting and not under load from the pedals..

I'm guessing there's a bearing on each side of the axle to allow the wheel to rotate about the axle, then another bearing assembly somewhere to allow the hub to coast relative to the input / sprocket assembly when free-wheeling; which is where it seems the issue lies.

I found this video which appears to offer a decent overview of the hub's operation, however it doesn't explicitly cover coasting and my tired, especially-dulled morning brain is struggling to work this out from the rest of the content..

 

[Chris S]

I'm guessing there's a bearing on each side of the axle to allow the wheel to rotate about the axle, then another bearing assembly somewhere to allow the hub to coast relative to the input / sprocket assembly when free-wheeling; which is where it seems the issue lies.

The hub has two sets of pawls. One is for the bottom gear, they're at the end of the axle assembly and are dual pronged. The other is towards the middle of the axle assembly, they're shared by the middle and top gears. When you coast the hub body is moving faster than the axle assembly, it just ratchets over the pawls like an ordinary freewheel would.

PS I was amazed by the clatter that comes from my SFR hub when I'm coasting. The older AW hub just makes a gentle tick.

 

[Kell]

Thanks - are you able to expand on the bearing arrangement at all? I don't think it's a problem with the "main" wheel bearings as it's only present when coasting and not under load from the pedals..

I'm guessing there's a bearing on each side of the axle to allow the wheel to rotate about the axle, then another bearing assembly somewhere to allow the hub to coast relative to the input / sprocket assembly when free-wheeling; which is where it seems the issue lies.

Basically this ^^^

i'm sure I read over the years that when you're working with cups and bearings like these there's a fine line between being too loose and too tight. I just feel it's easy to accidentally adjust the tightness of the bearings when trying to tighten up the wheel nuts - especially when your bike is covered in grime.

Last weekend, I had to bin all my wheel buts as they were rusted on. At the same time, I put in some effort to try and correct the play in the rear wheel. Some is OK (it's that fine line I mentioned) but anything more than a mm side-to-side is too much.

I only brought it up as my bike wasn't freewheeling properly after I put everything back together and sounds like it was doing the same as yours - ie the chain being pushed forwards as the freewheel wasn't freewheeling enough. Undid everything and played about with it a couple of time to get everything working OK.

Trying to set up the wheel with no play in it meant it didn't rotate at all. Putting too much play in feels a bit disconcerting.

 

[wafter]

The hub has two sets of pawls. One is for the bottom gear, they're at the end of the axle assembly and are dual pronged. The other is towards the middle of the axle assembly, they're shared by the middle and top gears. When you coast the hub body is moving faster than the axle assembly, it just ratchets over the pawls like an ordinary freewheel would.

PS I was amazed by the clatter that comes from my SFR hub when I'm coasting. The older AW hub just makes a gentle tick.

Thanks - and to confirm other than the axle bearings there are no other bearings in the hub assembly because all of the relative rotational motion between the three main parts of the hub are controlled by the epicyclic gear setup, correct..?

This would imply that the noise / roughness is coming from the pawls (maybe due to poor lubrication / contamination when riding up their ramps?) or the gears themselves (in which case shouldn't it be present when pedalling too..?).

I fully accept that these hubs are noisy, however this seems new; with a disctinct roughness felt through the pedals that seems to remain even when pedalling forward with no load so as to prevent the hub making the usual "coasting" noise..

Basically this ^^^

i'm sure I read over the years that when you're working with cups and bearings like these there's a fine line between being too loose and too tight. I just feel it's easy to accidentally adjust the tightness of the bearings when trying to tighten up the wheel nuts - especially when your bike is covered in grime.

Last weekend, I had to bin all my wheel buts as they were rusted on. At the same time, I put in some effort to try and correct the play in the rear wheel. Some is OK (it's that fine line I mentioned) but anything more than a mm side-to-side is too much.

I only brought it up as my bike wasn't freewheeling properly after I put everything back together and sounds like it was doing the same as yours - ie the chain being pushed forwards as the freewheel wasn't freewheeling enough. Undid everything and played about with it a couple of time to get everything working OK.

Trying to set up the wheel with no play in it meant it didn't rotate at all. Putting too much play in feels a bit disconcerting.

Thanks - again if it's the wheel bearings surely the roughness should be there when both coasting and pedalling, rather than when just coasting?

I wonder if loading up the crank could somehow dampen vibrations coming from the back end...

When I next get the opportunity I'll check the rear wheel for lateral slop in an effort to get a better idea of what the bearing preload is like.

 

[Chris S]

Thanks - and to confirm other than the axle bearings there are no other bearings in the hub assembly because all of the relative rotational motion between the three main parts of the hub are controlled by the epicyclic gear setup, correct..?

That's right.

 

[wafter]

That's right.

Cheers - looking increasingly like it wants a strip, flush and re-grease... which I suppose is reasonable after the distance it's covered.

Something else to add to the ever-growing "sources of demand-driven anxety" pile...

 

[oldandslow]

I've got problems with noise on my BWR. It happens both pedalling and freewheeling, so is unlikely to be the transmission. The advice I've had is to check the HSA470 actuator plate on the driver assembly. Whilst not officially listed as a BWR spare, it's apparently the right one.

The spare plate arrived this week, but I haven't had time to strip the hub again and try it.

https://www.brommieplus.com/portal_b1_page.php?owner_num=b1_408821&button_num=b1&cnt_id=62068
https://www.sjscycles.co.uk/hub-spares/sturmey-archer-actuator-plate-for-driver-hsa470/
https://yacf.co.uk/forum/index.php?topic=83805 (final posts, this March onwards)

 

[Chris S]

I've got problems with noise on my BWR. It happens both pedalling and freewheeling, so is unlikely to be the transmission. The advice I've had is to check the HSA470 actuator plate on the driver assembly. Whilst not officially listed as a BWR spare, it's apparently the right one.

The spare plate arrived this week, but I haven't had time to strip the hub again and try it.

https://www.brommieplus.com/portal_b1_page.php?owner_num=b1_408821&button_num=b1&cnt_id=62068
https://www.sjscycles.co.uk/hub-spares/sturmey-archer-actuator-plate-for-driver-hsa470/
https://yacf.co.uk/forum/index.php?topic=83805 (final posts, this March onwards)

A lose actuator plate will make a rattling noise. You don't need to strip the hub to replace it. Just remove the drive-side cone and drop the driver out.

Twist the new actuator plate over the driver so that the pawls are recessed before you put it back in. If you don't it may not seat properly and you will have excess free-play on that side.

 

[oldandslow]

Thanks. I'll get onto it as soon as I have a free evening. September 2026 then...

 

[wafter]

I've got problems with noise on my BWR. It happens both pedalling and freewheeling, so is unlikely to be the transmission. The advice I've had is to check the HSA470 actuator plate on the driver assembly. Whilst not officially listed as a BWR spare, it's apparently the right one.

The spare plate arrived this week, but I haven't had time to strip the hub again and try it.

https://www.brommieplus.com/portal_b1_page.php?owner_num=b1_408821&button_num=b1&cnt_id=62068
https://www.sjscycles.co.uk/hub-spares/sturmey-archer-actuator-plate-for-driver-hsa470/
https://yacf.co.uk/forum/index.php?topic=83805 (final posts, this March onwards)

Thanks - not sure that this is the issue in my case though; unfortunately can't see the YACF link either. Good luck getting it sorted

I've done a bit more digging and come across the very useful video below which shows pretty much complete disassembly of the hub:



This shows three sets of ball races in the hub (irritatingly working chronologically backwards for the sake of this exercise):

2:45 - hub assy to axle - NDS
2:37 - freewheel body to axle - DS
0:53 - freewheel body to hub assy

Since the noise I'm getting occurs when coasting / there is relative motion between the static freewheel body and rotating hub assy it appears that the bearing separating the two is likely the issue.

Access to this bit appears relatively straightforward; although potentially requires the removal of the hub's DS end / cover to allow access to disengage the pawls on the freehub body and allow it to be withdrawn. This will evidently require the purchase of the special SA 4-lugged spanner; assuming I don't want to butcher it with a hammer and screwdriver as recommended by some bellend in another video..

Since I'm going this far I wonder if it's worth stripping, cleaning and re-lubing the rest of the unit since it's now covered over 5.5k miles... I've heard that landrover hub grease approximates the thixotropic grease used in these hubs but am unsure of application method or amount.

I'm tempted to strip down to sub- assemblies and soak these in paraffin, however have doubts about getting a decent amount of lube back in there.

I suppose if the hub is properly stripped down to bugger all I could potentially apply the grease liberally to all individual components to ensure complete coverage...

 

[wafter]

Another (largely) nice video on reassembly from the same source:



Having seen how it all goes together I'm not 100% convinced it needs the special thixotopric grease recommended elsewhere; and wonder if it wouldn't be fine reassembled with good old bog-standard moly grease.

In other news I had a look for appropriate spanners and it appears that the HTR145 is the correct one - available from SJS for £38.

Really itching to get this done now; although I'd rather wait to order the tool until I need other bits from SJS to justify the postage, while I don't really want to pull the bike to bits until I have a suitable replacement - although worst-case I suppose I could always use the Fuji.