Modding a Brompton B75

DBrown67

Well-Known Member
I've been hankering after a Brompton for a while now. My daily commuter is a Cube mtb that I put an electric kit on. I can go anywhere on it and won't be getting rid of it but it is a heavy lump to take in the car. So for summer use when I go away for weekends I want a folder.

Saw the B75 this summer and loved the colour. Having looked into it I see it as a blank canvas to mod to what you want. But it already comes with stuff I'd want anyway like extended seat post and 44T chainring for lower gearing. Mud guards are a must add.

One thing I disliked about an M that I test rode was the bars seem quote narrow which would be the same for any model. Found it a bit twitchy. I suppose I'd get used to it but I don't see why I couldn't swap out the M-bar and fit a mid riser with around 80mm rise. It should in theory put the bar to the height of an S and the wider bar should still fold OK. The cables will become slacker by lowering the height but some would be taken up if the brakes etc. move further out a touch on the extended bar.

I was in Halfords at the weekend and sat on a Dahon Uno. It just looked so simplistic (though single speed no good for me), the bar height felt perfect and was wider than the Brompton. That measured 1000mm from ground to bar so not too far from that should be fine.

If I do take the plunge it will deffo be a B75. Anything else is just too expensive and I can't even get that colour unless I buy a B75. So I see this as the best option for me if I'm doing a few mods.

Just wondered what others might have done with the bar on a pre-2017 3 speed (as that is effectively what the B75 is)
 
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Cycleops

Guru
Location
Accra, Ghana
@chriscross1966 is our resident Brompton modder here.
 

12boy

Über Member
Location
Casper WY USA
I have tried a number of things on my S of which some were good and some not:
Bar ends for a break from the normal flat bar hand position. Cut short didn't affect the fold.
Ergon cork grips which were nice but especially with bar ends use a lot of space.
Ergon rubber grips with tiny bar ends. Those bar ends were too small to help me.
Velo Orange Porteur bars as 480 mm width. Great hand position but their narrowness seemed too twitchy for safety.
Velo Orange Milan bars which rotated in the clamp but otherwise comfy.
Salsa moustache bars flipped down, currently in place and used with DuraComp drop bar brakes. Also used with a QR on the stem clamp so folding is possible. Those bars will accept Sturmey bar end shifters if that is your pleasure.
Probably more than you want to know but my 2 cents worth.
 

Geedubbayoo

Regular
One thing I disliked about an M that I test rode was the bars seem quote narrow which would be the same for any model. Found it a bit twitchy.
Did you have a front bag with some weight in it attached to the Brompton during your test ride? I did not the first time I tried one and walked away unimpressed. It did feel twitchy, unlike the “regular” bikes I was used to riding with larger wheels. But a few weeks later, after trying a few other folders, I went back and this time the clerk put a weighted bag in the front. It was a much better experience. I could be wrong but the problem might not be the width of the bars.

And yes, after buying one I have since become accustomed to riding it in its “twitchier” configuration (no weight in front). While I can tell a difference it’s not a negative experience at all, at least for me.

Greg W
 

Kell

Über Member
First off, Bromptons are very twitchy - even more so coming from an MTB.

I remember trying a road bike for the first time in years after being on an MTB and that felt twitchy. Now, going back to that after being on the Brompton it feels so stable. Going back on the MTB, it feels like it's never going to turn at all.

I modded mine with a set of Ritchey low rise bars. Although I did end up sawing (badly) the ends off to make them a little narrower.

I’ve just ordered another set as mine are now a few years old, and I’m replacing all the alu parts as my cranks recently snapped.

You’re welcome to have the old bars to try out if you’re anywhere near High Wycombe. I’d offer to post them to you, but suspect the cost of postage would make it prohibitive and you may as well just order a new set.

I ordered an H type originally and fitted these because the S type was just too low and the M type felt too high.

Luckily my rough calculations proved correct and the bars ended up somewhere between M and S and the added height of the fold in the H stem meant they still have ground clearance.

I’ll add some pics to this post when I get to work.
 
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Kell

Über Member
Pics:

My bike as I ordered it:

yhxYr0pB__GL08iG4Mqp0Dy8sSQ&_nc_ht=scontent-lht6-1.jpg


Immediately after adding the bars...

aMcUc5LqgplFtABnAQWyumjGYkA&_nc_ht=scontent-lht6-1.jpg


4ukbiFgvVfOF0j6Y5AArohfpPEg&_nc_ht=scontent-lht6-1.jpg


How it folds:

zbeIjKWVCuZYWMqhWMc9m7fhTag&_nc_ht=scontent-lht6-1.jpg


This was the diagram I used to work out relative bar heights, but I don't think it applies to the new bikes as they tried to standardise the stems.

QKR_XxMJInLKXc0W9J1cAJipovA&_nc_ht=scontent-lht6-1.jpg


As I think you should be able to see from the diagram above, the length of the stem differs (or differed) when I ordered my bike. The M-Type and P-type are different parts, but look to be a similar length. Whereas the S-Type and H-Type are also different parts and also look to be of a similar length. So putting 80mm riser bars on a M-type would make it about the same height, if not lower, than an S-type.

If you assume the clamp of the H-type and S-type are the same height, then my 30mm riser bars should give a grip height of around 954. I did measure the height of mine at one point for someone else, but didn't record the figure.

Works for me. The only thing that is a slight issue, is that when you turn the steering all the way to the right, it does pull on the front brake cable and activate the front brake, but this is only when maneuvering the bike rather than when cycling.

I've often wondered if you could run the brake cable the other side of the main tube to help prevent this, but have not investigated it yet.

YMMV.
 
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Tenkaykev

Senior Member
Location
Poole
I purchased those for my C3 Kell. I have a 2015 Orange Black "M" as my everyday Brompton, and my C3 has been "blinged" up a bit.
I find the "M" more suited to my bimbling about, and the riding position more comfortable and so had planned to fit the Joseph Kuosac bars to the C3 to bring it up to "M" handlebar height but I just can't bring myself to do it yet, I think I like the S bar aesthetic on the C3.

I suppose that there is nothing to stop me fitting the bars and new "M" brake and gear shifter cables to give it a go, I could then just swap them back if it doesn't work for me.

Incidentally I fitted the Joseph Kuosac Brompton "M" bars to my Orange / Black bike and cut the bars to take a 130mm Ergon grip. It folds ( just about ) without the handlebar hitting the ground but it is very close.


494576
 

Kell

Über Member
Unless I’ve misunderstood (probably) why would the JK bars be nearer to the ground than standard M bars?

is it the width rather than the height?
 

12boy

Über Member
Location
Casper WY USA
I installed a v-brake noodle on the last part of cabling to the front and run my cables as I wish, having dispensed with the piece that spits the front cable and has a loop to gather the rear. Someday I'll put a top pull side pull brake and make it even simpler.
 

Tenkaykev

Senior Member
Location
Poole
Unless I’ve misunderstood (probably) why would the JK bars be nearer to the ground than standard M bars?

is it the width rather than the height?
The JK bars are the same height as my ( 2015) M bars but wider, you can fit standard 130mm grips. I used a plumbers pipe cutter to trim them down. They have mm markings either side of the bars to assist measurement.
You could have them assymetric and leave a bit extra for your Garmin / light / mirror on the right hand side if you wished.
 
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OP
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DBrown67

Well-Known Member
Thanks for the advice guys... and specially to Kell for the offer of the bar. I'm in Leeds but I think a flat bar on a B75 would be too low at 933mm high overall. Remember the B75 uses the older (shorter) stem and older bar (150mm rise) even though the height is still the same as current M models at 1083mm. But an 80mm riser will at least get it to 1013mm which is between the S and M and very close to that Dahon Uno I sat on, while at the same time allowing a slightly wider bar not affecting the fold.

This is all on paper of course. Provided the measurements on Brompton and SJS websites are accurate I don't see why it wouldn't work out.

I'd be getting it from Halfords as well for the 10% British Cycling discount. Cycle Republic exempts Bromptons (you only see this in the small print) and Evans is 10% off accessories only.
 
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Kell

Über Member
Not sure where you got the 1083 from.

The current M type height (according to Brompton) is 1015. In fact, most of the heights of the new models are within a mm or two of the pic I posted above.

I just found this online that gives the heights of the current bikes.

brompton-handlebars.jpg


According to the link for the JK 80mm handlebars, it says that fitted to the older S-type stem would give a bar height which is the same as the current M type. This can't be quite right, as in both the new and older versions of the bike the difference between S and M is 90 mm.

The Ritchey bars I have have a low rise of 30mm putting them at about 955.

Of course, the height of the bars is only relevant if the seat height on the Dahon is the same - which would depend on BB height and crank length.

Good luck.
 
OP
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DBrown67

Well-Known Member
Yeah that was my bad. It's not 1083mm... it's 1015mm as you pointed out. But fitting the 80mm riser still puts it at 945mm on the older stem which is 20mm over the current S model. Fitting the later Brompton bar (120mm rise) does not widen them, so pointless really.

EDIT: Just found this at 100mm rise x 600mm wide and someone in the review section confirms they are great for the B75 with no cutting required. https://www.sjscycles.co.uk/handlebars/joseph-kuosac-handlebar-for-bromptons-mid-rise-254mm-clamp-silver/
 
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Kell

Über Member
They sound perfect.

Hope it works out

Out of interest, which stem is on the B75. I couldn’t find out online, but had assumed it was the old S type.
 
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