chagzuki

You likely won't save weight changing the crankset, it's extremely light, and in fact I'm sure the new 2013 model will be heavier (you can see they've decided stiffness is a priority as the crank arms are much thicker). A titanium bottom bracket could save you 100g.

A.Danger

Ok, I'll start there. Many thanks.

Abeillaud

Further information:

I do not have much information on the relevance of a titanium axis to save some few tens grams compared to the other BB of highest quality, considering the mechanical qualities of the titanium for a bottom bracket and also considering its price.

I can add these datas (citation from this source: (Source: https://www.bromptonforum.net/t4606-l...n-mono-plateau )

"Poids du BB 7700: 175 g. Poids du pédalier dans mon cas: 538 g. Ensemble pédalier et boitier: 713 g"

"Le Dura Ace FC 7700 que j'ai choisi est un des rares pédaliers aussi léger que le Brompton Stronglight (Le FC 7701 est quasi identique au FC 7700 mais avec quelques grammes en moins). En 170 mm, le poids de manivelle de droite avec un seul plateau Dura Ace de 53 dents est de 345g et manivelle de gauche de 193 g, total: 538 g. Vous trouverez des pédaliers qui dans la même configuration ont un surpoids de 200 ou 300 g. Ce qui n'est pas négligeable car cette pièce est en rotation (tout comme les pédales et les chaussures: il faut donc sommer ces éléments)."

Translation:

"BB 7700's weight: 175 g. Crankset in my case: 538 g. Bottom bracket + crankset: 713 g"

"The Dura Ace FC 7700 I chose is one of the few crankset as light as the Brompton Stronglight (FC 7701 FC is almost identical to the 7700 but with a few grams less). For the lenght 170 mm, the weight of the right crank with only one Dura Ace 53 tooth crank is 345g and the weight of the left crank is 193 g, total: 538 g. You can find some cranksets with the same configuration with an overweight of 200 or 300 g, which is not negligible because this part is spinning [far enough from the axis] (like the pedals and the shoes*), so we have to sum these elements. "

* Pay attention to the weight of the pedal and the shoes, if not made, it's more important than 30 or 40 grams saved for the BB. Secondly, but it's my point of view, the mechanical quality of the bearing is one of the most important criterion. And the BB-7700 fills us entirely.


BB-7700

fietsbob

Chags, should keep an eye out for an Old campag style crank arms set.
those wont adversely effect the Fold width,,

lots of other companies made something similar
to get some of Campag's market share, then.

even Stronglight.

A.Danger

There is only one spindle length with the BB 7700, correct?

Or, would there be a downside to using Campy Centaur cranks? What BB would work, in that case?

Thanks for helping an enthusiastic beginner learn!

14R 

Yes, one of the last batches.

alesi

Hi, I'm using a 2-speed. Do you think these parts can replace the current sprockets:

https://harriscyclery.net/product/shi...w4668-qc49.htm

https://harriscyclery.net/product/mic...w1710-qc49.htm

Thank you.

jur

The 16T might be OK but I don't think the 12T would be right - have a look at this, you'll see it is quite different:
https://www.sjscycles.co.uk/brompton-...mno-prod22343/
The general shape is different and the teeth are taller.
That vendor's price is low so you could order from them anyway.

bmac.to

I have followed this thread with great interest. I ended up purchasing a Campy Centaur crank from ebay (as someone else in this thread did) and figured I would give it a shot. During install, I noticed the BB had a pretty good grind to it so I pulled it out - the left hand side bearing was fully rusted after only 2 years of ownership (2 winters of commuting however). So I then ordered a Phil Wood 120mm BB and replaced both the BB and crank in one go. I added a BBG guard to keep the mudguard effect of the original.

With my measurements, I dont think chainline/q-factor/etc changed much at all - definitely within the accuracy of how I was measuring the before/after.

The crank I replaced was the 54T and the Campy came with a 53T and a 39T ring (a common combination) so I moved the 53T to the inner ring. There are 54T rings and larger available but they are a bit pricey (more than the crank/rings I bought off of ebay).

The increase in stiffness was very noticeable - especially when standing. The new crank arms are 172.5mm long and I dont think I can feel any difference in length.

Overall, a great upgrade with no downside - folding works as well as ever.

chagzuki

Great stuff. I agree with earlier posts that campy chainsets do generally fit the Brompton aesthetic better than most others. Could you post a pic or two more zoomed out for a better sense of how it looks?
So the campy stuff other than record and chorus require a wider bb, 110/113 ISO taper? Is the Phil Wood bb ISO?

The current brompton BB isn't shielded on the non-drive side, water can get in easily and rust ensues. Best to fill the spindle hole in the left cup with loads of grease when installing to create a barrier.

alesi

I believe he is using ISO 120mm BB. Campy crankset is ISO tapers.



Thanks for information. Are you using symmetric Phil Wood BB?

The original Brompton BB is using 119mm + 3mm offset.

fietsbob

Phil's BBs do allow pressing the axle in the bearings, to get the chain line spot on
a 12t as the only cog on the Brompton 1 or 2 speed hub..
I think the spline is Shimano,, maybe their BMX cogs will also go on those hubs ..

bmac.to

This is the symmetric 120mm ISO Phil Wood BB - as mentioned, you can adjust the cups on the Phil Wood to get a couple of mm offset (I have the one cup about 3 threads out on the drive side, and about 1 thread on the other). However, there is a non-symmetric option to the Phil Wood BB if greater offset is required. One thing I learned long ago, if you do go for this type of BB, buy two install tools - adjusting the offset becomes much easier.
The original BB is a cartridge design that does not allow this type of adjustment (ignoring spacers).
A "better" pic (I am no photog).

chagzuki

Very nice. So is it safe to assume that the original Brompton BB would have produced the correct chainline with this crankset?

Not wanting to divert things too far OT but are those greenspeed scorchers?

bmac.to

Yeah, the original BB produced the correct chainline with this crank - it moved the chainring maybe 1mm closer to the BB than the standard Brompton crankset.

Nope, just very dirty Marathons.

fietsbob

I've stacked the 2 installation tools and a flat washer and used a crank bolt
to physically pull the BB Axle thru the bearings.. the nature of a good press fit.

this is without yet installing the BB in the frame.

the mounting rings are another fine tuning adjustment.

pollington

Hi all, am interested in nudging up the gear inches on my 2spd from the standard 74.7 (54/12) to something around 80.

The options would appear to be either to drop the rear sprocket down to 11T (but I can't find anyone that can supply such a sprocket) or swap out the chainset for a 58 or maybe 60T (I understand 60T is about as big as you can go without fouling the folding mech).

Has anyone experimented with bigger chainrings? How big can you go and which chainsets would you recommend?

Any tips gratefully received!

questionesse

Guys,

I'd like to warm this up as I'm considering changing the crank arms.
Is there a lighter option that fits the sprocket wheel and does not cost a fortune?
What's the weight of the Brompton crank arms? Anyone got an idea?

thx!

fietsbob

Yea, You could always just Upgrade to the current Brompton 130 BCD replaceable chain ring crankset .

You can look your self, they probably weigh what any other crank of similar materials and length, does .


Todd At Clever Cycles , (on Hawthorn PDX,) fit a 110 bcd 36-44t double crank on his M6L and toured the OR , N.Cal coast with it .

used it as a dual range smaller when hilly , larger when not, so the shifting was just the greasy finger technique.

There is a Blog about it on their site.

jur

If you have the latest Brompton with replaceable chain wheel, the bottom bracket is not standard taper. You will have to get a bb too.

fietsbob

ISO or JIS it has to be one of the 2..

jur

It's ISO. Most cranksets are JIS, except Euro ones like Campagnolo. The new Brompton set is Stronglight (guess) and Nigel Healey informed me recently about this when I wanted to make a quick swap when I met him in SF.

bargainguy

FWIW, Tiller Cycles in the UK have some reasonably priced options for cranksets, notably the Stronglight 40t and Alfine 39t. Shipping outside the UK might be pricey, however.

Scroll down: Brompton Gearing

emiel013

ho can help me, i gonneput a other chainset on my brompton campagnolo record model 2006 but what kind of bottom bracket do i need.
thanks

blakcloud

You will need an ISO square tapered bottom bracket, English thread with the correct spindle length. The key being the right spindle length. The chainring needs to have good chainline and the bike needs be able to fold. The original F.A.G. ISO bottom bracket was 119mm, so something close to that is what I would try first.