Keen to have a 44t Brompton Chain Wheel. To buy or to trade with my 52t.

berlinonaut

Senior Member
Location
Berlin Germany
https://www.spacycles.co.uk/m8b0s109p2188/STRONGLIGHT-ST55-Single-Chainset
(...) This might be the answer.
Does anyone think this replacement would be a good/perfect match or indeed have reservations?
I'd say totally valid. You should be aware that the current Stronglight 55S seems to be designed for a JIS bottom bracket rather than for an ISO bottom bracket like you have now. It will however still work (with a slightly changed chainline) but personally I'd change the bottom bracket along the line as this is neither a difficult nor an expensive exercise. In fact there are many many 3rd party cranks that you could use.
I think @u_i has a point rearding the chainguard - always possible to add one aftermarket, but typically needs tinkering and adds to the cost. So in the end you may overall end up not that much cheaper than the original actual Brompton crankset with the disadvantage of still having a fixed chainwheel and the advantage of the 55S looking relatively similar to the original. One advantage of the original Brompton cranks since 2008 is that the non-drive-side crank has a little nob on the inside which successfully hinders the folding pedal from rubbing agains the frame. Older cranks as well as 3rd party cranks lack that feature and furthermore often enough the non-drive-side crank has to be treated with an angle grinder at the outer edge to make the folding pedal do what it is supposed to.

Going Stronglight you could i.e. also consider i.e. the "Mygal S" or one of the Impact ones, depending on the price. All three do offer various sizes of the chainwheel and the ability to change it, the Mygal is a 130 one which means typically for chainwheels 39t and bigger whereas the Impact ones are 110 ones which means getting chainwheels with more than like 46t is possible but those are hard to find and typically expensive. For small chainwheels no issues (and easier to find than 130 ones).

You could even go for a double crank set like i.e. the Impact Compact or Impact E Compact and, with a combination of i.e. 50/34t, 50/36 or 46/34 gain a granny gear that will take you up most hills, referencing to your original problem. Downshift goes with a heelstrike, upshifting is manual - no need for a derailler on the front and easier than it sounds. You could even simply add a i.e. 39t or 34t to your existing chainwheel, massively saving on cost, and achieving the same effect. Has been relatively common with Bromptons for a while as the old crankset offers the possibility (though not officially) through the holes in the chainwheel.

You may check the effects here: http://xldev.co.uk/bgc.html

So many options... :smile:
 
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shingwell

Active Member
If you replace the chainring it needs to have a chainguard, unless you do not care about stained clothes.
I would go further and say it is a safety issue. If clothing gets caught in chain/chainwheel the outcome is not good. It happened to me as a youngster (non-Brompton bike), luckily no cars around at the time or I would have been run over.
 

12boy

Veteran
Location
Casper WY USA
I am one of those guys that has 2 chainrings...110 BCD crank arms and 58 and 38 chainrings. Only problem so far has been the chain falls off if folded with the 38. I primarily use the 38 for 10% grades but it's nice to know it is there. My 38 is on the inside BTW.
 

u_i

Well-Known Member
Location
Michigan
I am one of those guys that has 2 chainrings...110 BCD crank arms and 58 and 38 chainrings. Only problem so far has been the chain falls off if folded with the 38. I primarily use the 38 for 10% grades but it's nice to know it is there. My 38 is on the inside BTW.
That is interesting. I have 50-34-20, so 30T difference and I can leave it in 20 for folding with no fear of the chain falling off. I wonder what makes a difference. Not that I wanted for the chain to come off, but even from my perspective it is good to understand how the system works. Are you using any front derailleur? Maybe it is the cage that helps to keep the chain in. I also added an inner .cage guard, but this was to prevent the chain dropping during vigorous shifts in, not when folding - the problem was just not there :unsure:
 
OP
Mr Cotter Pin

Mr Cotter Pin

Regular
Hello all

Just a quick note to say that I came across what looks to me like a pretty decent 44t old style Brompton chainset.

Hopefully I'll have it by next week.

I may deploy 12boy's idea of changing the sprocket from a 13 to 15 (or even a 16 if that is possible) if the 44t does not do the trick but I'm hoping it will.

Thanks for the calculator berlinonaut and the alternative Stronglight chainwheel suggestions, I was actually warming to the idea of getting a new Stronglight chainset and BB, until I saw the 44t Brompton.

And I totally agree with the chainwheel guard, a mandatory device.
 
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