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raleighnut
Legendary Member
- Location
- One of the 'Elite'
OP
OP
srw
It's a bit more complicated than that...
The Brompton chain I bought (stamped SRAM PC-10) is Brompton branded on the packagin, with one of their extremely long code numbers.
I've fitted a 1/8" chain (SRAM PC-1), and it all works.
1/8" chain - OK
3/32" chain - not OK.
THe chain tensioner jockey wheels look as if they shouldn't work with a 1/8" chain, but actually do.
OP
OP
srw
It's a bit more complicated than that...
Here are a couple more photos.
The folded package
The rack
The handlebar. It's a bit more squished than is comfortable, but there's plenty of room in the folded package, so I might find a different brake lever that will let me get the twist shifter further towards the centre. As well as needing to fix the rear mudguard properly I'm also planning to replace the grips, probably for something Ergony with bar ends.
The folded package
The rack
The handlebar. It's a bit more squished than is comfortable, but there's plenty of room in the folded package, so I might find a different brake lever that will let me get the twist shifter further towards the centre. As well as needing to fix the rear mudguard properly I'm also planning to replace the grips, probably for something Ergony with bar ends.
cisamcgu
Legendary Member
- Location
- Merseyside-ish
I was considering this myself, but with all the "bodges" and "fixes" that you have had to do, I think I will leave well enough alone and continue on my merry, 6-speeded, way.
Excellent thread though, many thanks for sharing
Excellent thread though, many thanks for sharing
OP
OP
srw
It's a bit more complicated than that...
To be fair to Ben, the bodges and fixes are more to do with my klutziness and the other stuff I'm doing at the same time as with the 8-speed conversion. Here's his instructions, with my comments. Based on the kit itself I'd recommend the adaptation. I'm going to go out on the bike this afternoon after which I'll report back again.
http://www.kinetics-online.co.uk/uncategorized/brompton-8-spd-instructions/
Fitting the back wheel:
– Take off your old back wheel, and swap the tyre, tube and rim tape onto the new wheel.
– Take off the original tensioner, and all gear cables, including the pulley for the gear cable on the right side.
– Slide the new wheel into the dropouts – it should go with the cable guide pointing upwards – it can only go in one of two ways, so it should be obvious which way is right.
@srw: I found it a bit more of a close fit than I'm used to with the three speed, but it was easy enough once I'd worked out that using gravity to help made life easier.
– Slide the two tabbed washers onto the axle, with the tabs going in to the slots in the dropouts. Important: use the new washers supplied with the kit, not the original ones from your old wheel. Fit a Sturmey nut on the left side, and the plain nut on the right, and tighten.
– Slide the chain tensioner on on the right, then fit the thin washer, and the other Sturmey nut. Only do this nut up hand-tight, you’ll want to take it off again when you fit the cable.
– Pump up the tyre.
Fitting the chainset and chain:
– Take off the pedals and chainset.
– Fit the new chainset, and fit the pedals.
– the chain may not be the right length – with the standard 20t sprocket, 33t chainring, and latest tensioner, the chain should be 100 links long.
– if you fit a new chain, fit either a 7/8-speed derailleur chain, or a narrow single-speed one like the SRAM PC-1.
@srw: if the chainwheel is the same as the one I got then you want a 1/8" single-speed chain. The SRAM PC-1 works perfectly.
Fitting the shifter and cables:
– Fit the shifter to the right handlebar – you’ll need to cut down the handlebar grip a bit, and it should go with the cable to the front of the brake lever, not behind. If space is cramped, you can usually move the brake lever inboard a bit too. Make sure the shifter doesn’t restrict movement of the brake lever.
@srw: I found that having the whole thing inboard of the brake works best. I don't know whether that's in front or behind!
– Thread the outer gear cable through the plastic cable gatherer behind the stem, down alongside the other cables, behind the chainset and through the cable guide there, through the cable guide on the chainstay (going from outside to inside, like the brake cable) and up through the square tube that used to hold the plastic pulley, before curving down towards the cable guide on the hub – depending on your handlebars, you will probably need to cut a bit off the cable to make it the right length.
– Thread the gear cable through the outer cable. It’s easiest if you don’t put the outer cable into the cable guide on the hub yet, you can do this later.
– Fit the cable clamp as in the Sturmey instructions – put the shifter into 8th, and fit the clamp 105mm along from the end of the outer cable. Cut off the spare cable.
– It’s easiest if you take the tensioner off again for this bit – push the plastic cable clip on the hub backwards so you have some slack, and clip the cable clamp in place. Try operating the shifter to make sure the cable clip rotates around the hub correctly.
@srw: if you're unlucky (I was), there's a round lockring which constrains the gear-changing gizmo in place and which can pop off. The Sturmey instructions cover this, but are very unclear. Also, when Ben says "push the plastic cable clip backwards", that's what he means. Pushing it backwards (against a spring) provides some slack to get the cable retainer into its slot. The cable retainer goes with the nut outwards.
– Adjust the gears as per the Sturmey instructions – in 4th gear, make sure the yellow dot is in the centre of the window, on the back of the hub on the right-hand side.
– Re-fit the tensioner, and try again – operate the shifter a few times while pedaling, and check again that the yellow dot is in the centre of the window – adjust the barrel adjuster on the gear shifter if necessary.
OP
OP
srw
It's a bit more complicated than that...
Report after first ride: good. Very good. I don't know why Brompton don't use the 8-speed SA hub as the basis for a standard model. With the standard 33-tooth chainring, 7th gear is a decent slowish cruising gear and 8th is fine for downhill. 1st is incredible. I changed down to 3rd and then 1st on an uphill and almost pulled a wheelie because 1st is so low. Sheldon's gear calculator suggest that it's about equivalent to a 1:1 ratio on a conventional road bike.
OP
OP
srw
It's a bit more complicated than that...
The folding pedal folds absolutely fine.
The chain tensioner appears to be (similar to) the one that's used for the derailleur version of the Brompton. I'm used to a conventional setup like a standard derailleur system, where the chain rides on wheels inside a frame. Instead the chain rides around the wheels, and the wheels have very shallow teeth.
OP
OP
srw
It's a bit more complicated than that...
The imagination to realise that a nut acts as a perfectly good spacer for an overlong bolt!
All sorted now, thanks.
CopperBrompton
Bicycle: a means of transport between cake-stops
- Location
- London
I had to swap the bars to get Ergon grips to fit (you still have to cut down the right-hand one, but it leaves all of the supported section so that's not an issue).
cisamcgu
Legendary Member
- Location
- Merseyside-ish
GrumpyGregry
Here for rides.
rudimentary skillz iz all you need.
Rohloff_Brompton_Rider
Formerly just_fixed
I like those bars, what are they n where from please.I had to swap the bars to get Ergon grips to fit (you still have to cut down the right-hand one, but it leaves all of the supported section so that's not an issue).
