Brompton owners

Just won a set of ultegra 6601 ht2 130bcd cranks on eBay. Should go nicely on the Brompton! What chainring bolts will I need? Single chainring, right?

Yeah looking at the spider, just single chainring bolts should do the trick. It's voucher month for me! Going to start planning my mods.

Take care if you decide to do this. It isn't necessarily as straightforward as it might seem.

As I'm currently 'in negotiations' over a dispute with a major retailer, PM me if you want to know the details.
FWIW the Alfine chainset has a steel (Unlike Ultegra / DA aluminium) spindle.
I guess you get what you pay for.....
So the weight savings may be less than expected - I'll post the numbers once all the components have been delivered.

I may have dreamt this, but did I read somewhere that you can use individual SRAM 9 speed sprockets on a SRAM 3 speed hub (as supplied with a 6 speed Brommy)?

I believe you can but you have to tak a dremmel to the sprocket to remove some lugs.

Ok, thanks.

Well, I fitted the ultegra cranks. They're 10 speed 130bcd hollowtech 2, 172.5 length. Model is 6601.

The only issue I came across was that the tabs for the inner ring touches the chainstay when the bike's folded, like so.

With careful placement of the cranks prior to folding, I can avoid it hitting it, but I can see it being a ballache worrying about it every time. I guess my options are either drive side spacer between BB shell and BB, or somehow filing/grinding those lips off the cranks.

The chain line with the ring on the outside is 1mm further out that with the standard cranks, pretty pleased with that and would rather not space it if I can avoid it.

Unfolded, the cranks are fine, nowhere near hitting anything and the full fold works fine as long as the first stage of the fold is done a bit more carefully than usual.

I guess my options are either drive side spacer between BB shell and BB, or somehow filing/grinding those lips off the cranks.

With the ring on the outer position you wouldn't be using those lips, so I'd fire up the angle grinder and makes some sparks.

Yeah, I think that's gotta be the way to do it. If only I had an angle grinder...

Guess it's always nice to increase my tool collection. Would a cheap angle grinder do it? If so, any recommendations?

Yeah, I think that's gotta be the way to do it. If only I had an angle grinder...

You can always file it by hand.

It doesn't need to be completely removed, just enough for it to fold.

I can't see it as a problem, unless you choose not to get the rear hinge serviced when the time come.

I do have a file somewhere. I'll have a go and see if it looks like it'll be 300 hours work.

It won't take 300 hours, the crank is made from aluminum, they're easy to files down, maybe 20 minutes, half an hour max (I did this for a customer bike who have similar problem).

It will be especially quicker if your files isn't too badly worn.

The only file I have is only a bit bigger than a nail file. Last used it to file the wooden bridge on my double bass to fit a pickup, I think.

Anyway, after several hours of filing it's working. Gonna nip out and buy some proper files tomorrow and get them flush, but the spider just about clears the chainstay when folded now.

I have now noticed that the slightly longer crank means that if I spin the cranks after tucking the rear wheel under, the end of the right crank will just about clonk the nearest part of the rear derailleur.

Not really a huge issue, but something worth bearing in mind if you're changing cranks and have a choice of different lengths.

Guess it's always nice to increase my tool collection. Would a cheap angle grinder do it? If so, any recommendations?

Cheap is good when it comes to angle grinders IME. They're the kind of tools which invariably end up being abused. They're awesomely noisy though, so get the cheapest angle grinder you can, and spend some money on some safety specs and decent ear defenders...

Haha, sounds exciting! My plan thus far tomorrow is:

Get 2 straight pull bladed spokes from my mate's bike shop and also get him to face the Brompton BB shell. I noticed when the Brompton was upside down that it definitely needs it, I guess they weren't expecting people to use external BBs.

Buy either file(s) or angle grinder.

Fix the broken spoke on my road bike.

Chop bits off cranks.

Nice. Sounds like a good plan. The only potential improvement I could suggest is buying your own BB chasing and facing set and using that. I have one. It's a very satisfying tool to use.

Files are good enough.
Dremel is a bit quicker.
Angle grinders start around £25 from screwfix/B&Q/tool station/Machine mart and will go through a crank tab in seconds.......... followed by a big fuck off gouge into the crank arm if you slip or a bit heavy handed :)

Fantastic tools, thin cutting discs are best for thin steel, sanding pads are more gentle than grinding discs, and a wire brush disc is rather good for cleaning up steel frames and forks.
Alu dust is not good for you, so if you power tool it wear a mask/be out doors and wear safety glasses.
And practice before attacking a bike part as angle grinders can be a bit savage/quick at removing material.

Oh and a vice is handy if you dont want to try and hold onto what your attacking and trim your finger nails or finger tips too :)

Fantastic tools, thin cutting discs are best for thin steel, sanding pads are more gentle than grinding discs, and a wire brush disc is rather good for cleaning up steel frames and forks.

Flap disc for a job like this. Aggressive but not stupidly so. Of course, a bench grinder is what you really need for a job like this. Or a milling machine and rotary table.

Ah I'm back in herts these days, but cheers for the offer! I've got a dremel kicking about somewhere, I'll try to dig it out and see if that's quicker than the file at getting rid of the rest of the tabs.

Failing that, I'll try to get a bigger file. If that's too slow, I'll go for a cheapo angle grinder and try not to chop clean through the crank.

Cheers for the advice everyone! Oh and @danstuff, I'd love to get a facing/chasing kit but I don't do it enough to justify the price :(

Oh and @danstuff, I'd love to get a facing/chasing kit but I don't do it enough to justify the price :(

Easy way to solve that - buy or build more frames that need facing and chasing. Purchase justified. Job done. ;)

Well...... i think you can still get dual wheel grinders around £25 as well.
Got mine from B&Q years ago still going strong.
So many tools :)

(was better when i worked in a blacksmiths/fabrication, power forging hammer, forge, anvils, gas cutters, folders, formers, an old lathe that would thread round bar, miller etc etc etc, and around 3 old motorbikes in bits upstairs :) )

i miss my old work place :(

Don't have a power hammer or old motorbike yet, the rest is sorted. Power hammer is on the list, old motorbike is a warning sign meaning I've gone too far...

2x bantams and a Gilera with WP forks stuffed upstairs, amongst the old fire engine ladder and other bike bits.
All the heavy equipment was proper old school heavy cast frames and we had a little ford tractor for lifting pallets and girders off the steel delivery lorry. :)
They have gone a bit modern and got a fork lift now.

Which is nothing to do with Bromptons, but my old boss was going to get me brazing again in case i ever got round to making a frame.

So I took the Brompton to my mate's shop yesterday. Chased and faced the BB and borrowed his big man-sized files to reduce the tabs even further. Problem is, the clearance I gained by filing was lost to the facing, so there's a bit of contact again. His suggestion was to stick a shim on the driveside.

I may well do that, but I said I'd give it a try as it is, see how much of a ballache it'll be.

I've only had the quick ride to the station thus far, but it feels nice. Immediately noticeable is the reduced q-factor. Not sure how much by, but it feels like my legs are tracking a bit straighter. It'd be a shame to ruin that by sticking a spacer in between BB and shell...

Also, it seemed to feel a bit stiffer but it's hard to say with only one little out of the saddle bit so far.

Oh and of course it looks cooler, which is the main thing 🤗