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Brompton geeks - will this work?

(18 posts)
  • Started 7 years ago by rbrtwtmn
  • Latest reply from wee folding bike
  • This topic is not resolved

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  1. rbrtwtmn
    Member

    Am I missing anything? I think the following will work - but I thought I'd ask...

    Year 2000(ish) Brompton (plus or minus a few years). 5 Speed hub. Chain, sprocket, chainwheel all badly worn - and rear rim now dead. Hub doesn't select hardest gear so may be a little in need of attention. Has been gathering dust for 5 years but is being called back into service.

    Bike shop option requires new rim - and new chain/sprocket/chainwheel... but chainwheel of that size no longer available. So then not just chainwheel required but because of new design therefore cranks, and various other bits... whereupon it looks like we may as well just invest in a new wheel and maybe even a new bike for the rapidly mounting costs.

    But a new solution has appeared. My parents bought Bromptons not long after ours - so maybe 2003-6?? They had three speeds and used them sparingly - and not so long ago had these converted to something newfangled. The result is that we now have from them an old rear wheel, 3 speed, chain tensioner, sealed bottom bracket, chainwheel and cranks. So a full power train.

    My assumption is that if we clean these up (they are in good condition) and drop them into the shop (or fit myself for that matter) the bike will be nearly as good as new (other than that now 3 speed). Only thing I don't have is the chain.

    Anything I'm missing? Odd spacing differences? Chain size no longer available? Differences in bottom bracket size? Can't get the bolts to attach the cranks to the bb?

    Thanks for your thoughts.

    Posted 7 years ago #

  2. chdot
    Admin

    "chainwheel of that size no longer available"

    You mean at front?

    Seems unlikely.

    Posted 7 years ago #

  3. Roibeard
    Member

    I think Brompton parts are indeed swappable in this fashion.

    The issue may be that your five speed shifter may also need to be swapped for a three speed.

    The "chainwheel no longer available" may refer to the fact that Brompton have moved to a spider for the right hand crank, with a removable chainwheel, and have discontinued the single piece part.

    I'm sure someone more knowledgeable than I will be along shortly...

    Robert

    Posted 7 years ago #

  4. wee folding bike
    Member

    The front end of the transmission changed in 2013 so if your front end transplant is between 2000 and 2012 it should not cause any issues.

    The rear end might. 2000-2001 was when the rear end changed. I got an early mk III around April 2001. This change was partly to accommodate the SRAM hub, SA being temporarily unavailable, and partly to allow the future installation of the 2 speed changers.

    If yours came with the SA 5 speed I suspect it's likely to have the older mk II rear end. Have a look under the right chain stay. If there is a hexagonal braze on about half a centimetre across on the underside of the chain stay just in front of the drop out then it's a mk III rear end. If there is no braze on then it's mk ii. The mk III can use reversible anti rotation washers. These allowed you to fit either a SA or SRAM hub. If you're getting a second hand SRAM hub then you need to get the anti rotation washers with it. They are tabbed and slot into the frame. If you have the older rear end you might be able to fit anti rotation washers for SRAM hubs but I don't know as I've never done it.

    The rear wheel went back to SA around 2009 depending on which model you got. I think the 3 speeds took longer to switch because the BWR (wide range) was available before the BSR (standard) and the 3s use the BSR.

    Posted 7 years ago #

  5. rbrtwtmn
    Member

    Roibeard I think is describing the situation as regards the chainwheel as I understand it.

    wee folding bike - thanks - I think I need to work through your post when I'm fully awake to give it full attention.

    Roibeard - you're right, I'd forgotten the changer. Is the spacing on the settings different on the 5 and 3 speed? Is this different from modern spacings in some way? Would any older 3 speed lever work?

    Posted 7 years ago #

  6. chdot
    Admin

    If you have a three speed hub you can also use a standard left hand STI lever - much slicker gear changes!

    Handlebars on Brompton likely to be smaller diameter so will need a shim (the plastic ones that come with light and computer fittings will do).

    Posted 7 years ago #

  7. wee folding bike
    Member

    Any Brompton 3 speed shifter (and indeed any three speed shifter AFAIK) will be fine.

    The connection to the hub is different.

    SRAM hubs (2001 - 2008 ish) used a rod with ridges on it and a spring on the cable anchorage. Push the rod into the cable anchorage and the spring will grip on the ridges or squeeze the spring to get it back out. Adjustment is by changing it till it works. If the indicator chain just falls loose in top then it's probably right.

    SA hubs use a threaded rod. The male thread is on the end of the indicator and the female on the cable anchorage. Make sure to screw the lock ring into place or the anchorage will vibrate and drop out of adjustment. Adjustment is by putting it in 2nd gear and checking that the flat top of the indicator rod is level with the inner edge of the circular window on the axle nut.

    ADDENDUM

    You can't swap the SA and SRAM indicator rods as the sliding key thread is different inside the hub. If it's an SRAM hub you're going to fit then make sure you get the cable anchorage too. SRAMs don't have a windowed nut on the RHS. The left hand side has a big cover plate over the huge cone and two 22mm lock nuts. SA have a normal size cone/lock ring 16/17mm. The SRAM has oval dimples in the shell where the pawls engage on the inside of the hub. Their long axis is a right angles to the direction of rotation.

    Posted 7 years ago #

  8. rbrtwtmn
    Member

    Just for fun we have a different combination... the existing old 5 speed is a SA and the potential replacement 3 speed is a Sachs 3 speed... and there's no adjustment chain/rod/other attached to it. Currently researching this on Google...

    (and yes I think it'll be a mkII)

    EDIT: Ahh... Sachs was taken over by SRAM so presumably roughly the same as an older SRAM 3 speed.

    Posted 7 years ago #

  9. wee folding bike
    Member

    Yes, it's a Sachs Torpedo.

    You can still get the bits,

    http://brilliantbikes.co.uk/brompton-hub-gear-parts-and-cables/527-brompton-qgich3-sr.html

    http://brilliantbikes.co.uk/brompton-hub-gear-parts-and-cables/2491-brompton-qgcabanc-sr.html

    You'd need to ask someone like Brilliant Bikes, Ben Cooper at Kinetics or Dave Halliday about the anti rotation washers. I've never had a mk 2 frame so I don't know what you use with those drop outs and SRAM hubs.

    The Torpedo is a bit less refined than the SA. It works OK but isn't as pleasing when you take all the bits out. There is also something of a water ingress issue on the left hand side and I never found it easy getting the ball races. The cone is BIG and once it gets a bit of free play it can cause damage to the cage. I sometimes got ball races from Germany. Loose balls are tricky to use because the cone/cup is so big.

    You need the short wheel base cable if you're replacing that too and it's usually a good idea as the cables get bend and break under the bottom bracket.

    Brake cables will take some thought as you probably have an old model of brake lever. I think you're three models out of date. The dual pivot brakes are much better than the older ones so it might be worth considering replacing the whole brake calliper/ cable/ lever for both wheels.

    Rims wear out faster on Bromptons. I don't think the mk II came with rim wear indicators and if it did it would be the older, not very good, kind.

    Much of this you can ignore if you're not going to be using it for lots of miles.

    Posted 7 years ago #

  10. rbrtwtmn
    Member

    Thanks. Bike shop now investigating but generally seemed positive.

    Posted 7 years ago #

  11. Greenroofer
    Member

    Has anyone tried Marathon Winter tyres on a Brompton? Do you know if they fit under the standard Brompton mudguards?

    Given the way that our climate seems to be going, it's feeling like an extravagance to fit studded tyres to my 700c commuter bike now. All they do for 90% of the time is generate noise, cost and dissatisfaction. Due to having hub gears and a dynamo, I can't keep a spare pare of wheels, and swapping the tyres takes enough time to make it unpalatable to be doing regularly.

    I was wondering about having my Brompton be-studded in the cupboard for those rare occasions when studs are needed.

    What do you reckon?

    Posted 7 years ago #

  12. gembo
    Member

    @greenroofer, what about an ice bike? Get a single speed old banger and put spikes on it? Obviously cost component but would not take time. You would need space for the banger? Assuming Brompton option not possible

    Posted 7 years ago #

  13. sallyhinch
    Member

    Hmm, you're probably stronger than me, but I wouldn't like to try and carry a studded Brompton! And it's got quite lively steering at the best of times, so I don't know whether even with studs I'd want to ride it on ice.

    Posted 7 years ago #

  14. biketrain
    Member

    You may need to check that the studs do not come into contact with the steel frame. Probably not a great if the frame gets scratched and then salt get rubbed into the wounds, so the speak. When I fold my Brompton the rear tyre (original) rests against the frame.

    Posted 7 years ago #

  15. Greenroofer
    Member

    Hmm. Good points all. Maybe an ice bike is the answer. I can but dream...
    https://www.evanscycles.com/pinnacle-dolomite-singlespeed-2017-road-bike-EV264164

    Posted 7 years ago #

  16. Arellcat
    Moderator

    Greenroofer/Biketrain, there was some discussion about the Schwalbe Winter tyres for Bromptons on the BromptonTalk group about two years ago. The tyre was new out at the time.

    There shouldn't be any clearance issues with the spikes in riding - but yes, when you fold the bike the frame could get scratched. Kettering Leather Workshop makes a rather deluxe frame protector, as do a few sellers on Etsy; you could use the Off Yer Bike carry handle; you can get patches made from carbon fibre, or you could wrap the frame in handlebar tape. A cheaper alternative is self-adhesive Velcro. Stick the hooky side to the bike, and stick the fluffy side onto it.

    Posted 7 years ago #

  17. Greenroofer
    Member

    Ooh. Maybe there is hope.

    Posted 7 years ago #

  18. wee folding bike
    Member

    I put Marathon Winters on my S6L over the winter. There are no clearance problems and it doesn't seem to scratch the underside of the main frame tube as the studs are offset from the centre of the tyre.

    I think I've only taken it out once since I put them on around October. Most of the winter I'm on an M6R with Marathon Plus tyres.

    I'm a wee bit suspicious about the inside of the studs causing punctures.

    When you need them they are fantastic.

    Posted 7 years ago #

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