Brompton rear mudguard hack help


Active Member
London UK

Please refer to pics..

In the middle of my non-rack rear brompton bespoke custom-made alloy powder black mudguard are two screw holes, as is the case for plastic brommie mudguards supplied on purchase. I want to attach a small u-shape hook loop to as in pics.

1. Does anyone know the M-size or other generic size coding of the screw holes on the brommie mudguard ?
2. I'm also a bit uncertain about the sizings of the u-shape hook loops - they also seem to be catagoised by M-sizings too. eg:
Does anyone know which M-size or other generic size code i would need for these too ?

Thanks for your guidance. - Appreciated



They're M4 machine screws, (3.9mm outside dia.), through 4.5mm holes at 35.25mm centres. I just dismantled mine and put a digital vernier caliper on it! The spacing is dictated by the mounting plate on the inside, which clamps the mudguard stays to the inside of the mudguard, so if you can't find a saddle hook with suitable spacing it should be relatively easy to redrill and hack/bodge!

Very curious to know what the modification is - are you dragging an outlaw through town by the ankles? ^_^

Edit to add: that's for the rear roller plate holes. The threads are the same but the spacing is different for the top two, which just have the metal plate attached.
Last edited:


Active Member
London UK
Hi - thanks - i hadn't looked at the guard in situe and realised that central plate holds the stays. So looks like my screws may need to be longer than those to accommodate the depth of the u-shaped loop plate.

The u shape loop is because i want to utilise a QR seat-post rack when i do have a rack mounted so the panniers hang above the mudguard and the loop will act as a secure point to stop the panniers flapping around too much .... if that makes sense.

I toying with this rack solution because 1. it enables the rack to be optional and also 2. when you fold the bike up, you can just reverse the QR seat post rack, undo the secure point and drape the attached panniers over the folded bike attached as a single unit.
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