Brompton chain tensioner...

[srw]

...can it be cleaned and greased?

I've got an annoying grindy thing going on with my transmission. It's not the BB because that spins very freely when I take the chain off. It's not inside the wheel or freewheel because that spins very freely (more freely than any of my derailleur bikes) when I lift it off the ground and give the pedals a hoick. I don't think it's the chain - it seems to be pretty clean. So I think it must be the jockey wheels on the tensioner. If it's not, that's the easiest thing to get at and eliminate.

In the past I've taken it off and looked at it and thought that there must be some way of making it run more smoothly, but I've never found the way. Has anyone else?

 

[Brommyboy]

The tensioner should last for ever unless it gradually warps. It can collect a lot of gunge but this does not normally make a grinding noise, unless it is pushing the chain out of line over the sprocket. The small sprockets do wear out quite quickly so, despite having a straight chain line, I have found that the sprocket and chain have a relatively short lifespan. See if the sprocket teeth are starting to become hooked in appearance. It may be that they are due for replacement. If worn, this usually gives a rough feeling to the pedals while riding. It could also be that the hub gear driver has run dry. The simplest way to lubricate the hub is to remove the indicator rod (the thing that connects the gear to the cable at the axle) and trickle some oil down the hole while lying the bike on its side. A few drops should help. but do not flood it!

 

[Amanda P]

I've found that the idler cogs in the tensioner can get very gungy indeed. In wet, salty weather, bits of muck and grit get caught in the gaps between the tensioner frame and the cogs and it can make them stiff and grindy. Over-oiling the chain makes this worse, as everything gets sticky - use the Mickle method to keep things reasonably clean down there.

As for the idlers themselves, with everything made of plastic, I've been a bit reluctant to use degreasers on it. But white spirit doesn't seem to do much harm, and it softens the greasy gunge enough to scrub it out with an old toothbrush and a rag. Things run a bit smoother after that.

Oh yes, chains and sprockets do have a limited life on a Brommy, and if the two aren't meshing smoothly, BB's right; it'll feel grindy.

 

[AKA Bob]

Yes it can be cleaned! Its designed to run dry so should be cleaned regularly to avoid problems

Every couple of months I take mine off and give it a good dig with a screwdriver before soaking it in petrol or similar. This removes all the grease before being finished off with soap and water or if you are feeling brave a session in the dishwasher!!!!

You may find the 'grinding' is coming from the rear gear changer rocker ( the small square box on the frame) if this gets too dirty it stops travelling fully and won't allow the chain to 'jump' fully. I find a good wiggle and a little exploration with a small screwdriver normally sorts the problem before being sprayed with some GT85.

 

[Crankarm]

Yes, it can all be stripped down degreased, cleaned, dried and re-lubed to run like new. Check components for wear and replace if necessary.

 

[Rohloff_Brompton_Rider]

Have you set the gear chain indicator? You can get weird noises if the rod's not set properly.

 

[Bromptonaut]

I took mine to bits and serviced it while sorting a puncture a couple of weeks ago. On 6 speed the tension/jockey wheels run on roller bearings. Remove rubber dust cap and use small allen key to remove each idler. Clean, apply a smear of grease to the bearing surfaces and re-assemble. Spare idler wheels or full replacement kits including bearings and dustcups are available from dealers.

Cannot remember how they worked on old five speed but similar principle.

In neither type would I lightly dismantle the sprung joint. Did it once on five speed and it was hell's delight to get right again.

 

[Rohloff_Brompton_Rider]

Mine fell to bits on the canal once, what a ball ache finding the bits and reinstalling that was....I put extra tension on....

 

[srw]

Thanks for all the advice. I've given the whole transmission a good clean - after the last couple of weeks of mess the chain was beginning to feel it too. It's running a lot more smoothly, and the fact it was still getting smoother this morning leads me to suspect that it was mainly a dry hub, as Brommyboy suggests. I'll give it another week or two and then add more oil if it needs it.

Coincidentally I also suffered a broken folding pedal last week. Fortunately it happened in Hyde Park rather than as I was going round Parliament Square. And Brompton have at long last seen sense and replaced the obscure 24mm socket-driven pedal fastening with a sensible 8mm/6mm allen key-driven alternative.

The last remaining bits of fiddling (when I get round to them) for the moment will be to try and clean the main frame hinge a bit - it's getting stiff - and see if swapping out the rear LED enables the standlight properly. On darker roads I feel a bit vulnerable at traffic lights without a back light.

 

[Bromptonaut]

The last remaining bits of fiddling (when I get round to them) for the moment will be to try and clean the main frame hinge a bit - it's getting stiff .

I had that trouble too. A spray of GT85 flushed out a lot of rusty carp. Need to try something more viscous so it clings and protects better.

 

[Rohloff_Brompton_Rider]

The main bearing carrier and driver are quite open and as such do get full of grit and grime, the grease also comes out easily. When the main driver bearings are dry they do get Grundy under load.

It's one of the easiest jobs to do on the BSR or BWR 3/6 speed hubs. There are YouTube vids showing how to do this, I'm not familiar with the SRAM hubs.