Recommend a quick release bolt for Brompton handlebar /stem

DIscuss anything relating to non-standard cycles and their equipment.
snaz
Posts: 15
Joined: 6 Nov 2019, 7:35pm

Recommend a quick release bolt for Brompton handlebar /stem

Postby snaz » 7 Nov 2019, 5:25pm

Hi
Newbie question here; sorry – most probably really obvious to others…..
Can anyone recommend a quick release bolt which will fit the standard Brompton folding bike stem handlebar clamp bolt hole sizes - - does anyone know what diameter those bolt hole sizes are ?
Recommends, links and pics welcome
Cheers
sp
Image Attachments
brompton-shandle bar bolt 2.jpg
brompton handlebar bolt 1.jpg

Brucey
Posts: 35937
Joined: 4 Jan 2012, 6:25pm

Re: Recommend a quick release bolt for Brompton handlebar /stem

Postby Brucey » 8 Nov 2019, 1:14pm

listed as M7 x 20mm here

https://www.sjscycles.co.uk/brompton-accessories-other/?page=4

M7 bolts of any kind are rare, leave alone QR binders in that size.

I'd suggest that you use a standard seat pin QR binder bolt, with modified collars so that it fits the Brompton stem without damaging the M7 thread tapped in it.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

snaz
Posts: 15
Joined: 6 Nov 2019, 7:35pm

Re: Recommend a quick release bolt for Brompton handlebar /stem

Postby snaz » 8 Nov 2019, 3:42pm

Hi
Thanks for your reply.

The product you mention - M7 20mm;
https://www.sjscycles.co.uk/frames/ti-p ... -mm-black/

Does the 20mm refer to the diameter of the thread or the head ?
I'm not sure what a 'collar' is and how it would need to be modified if i purchased a seat post qr if that's what you mean by 'standard seat pin qr binder bolt'. Actually i'm not sure what a binder bolt is either or the M-grade: M7 is referring to.

I was looking in google images and i found these 2 images which look something like what i want.
They also look something like what you mention about adapting a seat post qr bolt if i understand you correctly
I've added a pic of the generic brompton seat post qr - is this something like what you mean ?
There's a few listed here:
https://www.sjscycles.co.uk/search/?ter ... %20release

How can i replicate that as hassle free as possible ? I like the red one because of it's small size but i'd quite like a handle that tucks in a bit more. Also i'm into lightweight.
Regard me as clueless and we'll get on just fine 8)
Thanks again folks

sp :D
Image Attachments
brommie qr seatpost 1.jpg
brommie qr handlebar 1.jpg
brommie qr 3.jpg

Brucey
Posts: 35937
Joined: 4 Jan 2012, 6:25pm

Re: Recommend a quick release bolt for Brompton handlebar /stem

Postby Brucey » 8 Nov 2019, 9:21pm

M7 = 7mm dia metric thread.

In point of fact the thread specification in this case is M7x1 i.e. 1mm pitch.

When you see a bolt specified as M7 x 20 then if the second number is higher than the first it invariably means it is a length, because it is extremely uncommon for bolts to be shorter than the diameter. However you can be caught out with this method of specifying bolts because there is often more than one thread pitch that is commonly used and this isn't indicated.

Anyway that the bolt is the 7x20mm size should have been b.obvious had you bothered to actually look at it.


This is a typical QR seat binder bolt

Image
the white bits are collars or shouldered spacers. The binder bolt is usually threaded M6 and the collars are usually 8mm diameter where they fit into the frame. I think that if you use this in your stem you will be able to fit one collar (modified ) but also that you will quickly ruin the M7 threading in the stem and (because this fitting isn't designed to be releatedly tightened and loosened) you may easily damage the stem itself.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

nez
Posts: 1623
Joined: 19 Jun 2008, 12:11am

Re: Recommend a quick release bolt for Brompton handlebar /stem

Postby nez » 9 Nov 2019, 4:08pm

I hope you won’t find me rude if I say that if you can’t tell the difference between a 7mm bolt and a 20mm bolt by sight it suggests your spanner skills are such that this sort of project is much better farmed out to a bike shop - though they might tell you qr fittings if available may not be suitable in this application. :shock:

snaz
Posts: 15
Joined: 6 Nov 2019, 7:35pm

Re: Recommend a quick release bolt for Brompton handlebar /stem

Postby snaz » 9 Nov 2019, 7:20pm

Hi
thanks for further info - sorry to cause offence - but i dont have any bike to refer to - the brommie is on order and will arrive next month. and clearly im new to bike-shed banter so it's all Swahili but willing to learn the basics. :D

Thanks Brucey for taking the time to hand-hold me through the dissection. v. helpful.
1. I've just been told to get a 6mm diameter 30mm length lever as this is the one that fits a brommie.
You're giving a warning the 6mm will over time mangle the 7mm thread in the brommie stem - does a 6mm thread even screw into a 7mm thread ?
2. I am not sure what a 'pitch' is ? Does that mean lee-way ie - fits a 6mm and an 8mm or something ?
3. 20mm seems terribly short for a bolt - is that really the length of the stem handlebar bolt on a brommie or is that referring to the length of the thread section only ?
4. Whats the mod on the collar about - what am i modifying it to - is this about shaving the plastic to a particular shape or something ? When it's attached is it one white collar either side of the handlebar or does it sit between the stem threads and needs 'fitting' in that space ??
5. Whats the difference between a 'QR seat binder bolt' and a 'cam lever' - what's the generic name for this part / to put into google search ?

thanks again - v helpful. appreciato

sp

nez
Posts: 1623
Joined: 19 Jun 2008, 12:11am

Re: Recommend a quick release bolt for Brompton handlebar /stem

Postby nez » 9 Nov 2019, 11:18pm

I didn't think you were causing offence and I didn't want to cause any to you. I was thinking of your safety. I have an early brommie which had the original handlebars which flexed and broke and could easily have killed my son who was riding. It was a known problem Brompton later solved with a handlebar brace. Not a problem you are likely to encounter but it certainly taught me how dangerous bars can be and how little room there is for mistakes in them. I hope you enjoy the bike. I've had mine since the early 90s and love it, though I don't have a lot of call to use it now.

By the way if you want to learn a few skills you might find there is a 'bike kitchen' or similar near you. It's a dead cheap way of learning a few skills and terms. Try googling that.

Good luck

L+1
Posts: 8
Joined: 7 Jul 2017, 5:47pm

Re: Recommend a quick release bolt for Brompton handlebar /stem

Postby L+1 » 10 Nov 2019, 11:06am

Can I ask why you want to change the handlebar clamp to quick release?
I’ve never heard of that as a modification before you posted those images and never thought of loosening the handlebars as an aid to folding for general use ( on and off public transport). For me, a loose handlebar would hinder carrying.

I agree with nez - even a modestly strong rider can stress Brompton handlebars when riding hard or uphill.
Personally I would want that area to be very much ‘non release’ on my Brompton.

snaz
Posts: 15
Joined: 6 Nov 2019, 7:35pm

Re: Recommend a quick release bolt for Brompton handlebar /stem

Postby snaz » 10 Nov 2019, 3:41pm

Hi

Nez - Thanks for advice - appreciated - i think you may be right about sourcing a local bike kitchen :)

L=1 - The quick release would support the installation of a new handle bar with swept backed grips. I would need to lower the grips to a downward position when storing. - see image.

Brucey: Hoping you will clarify that final set of questions.

thanks to all :wink:
sp
Image Attachments
vph.jpg