Author Topic: Brompton front axle thread?  (Read 3945 times)

LittleWheelsandBig

  • Whimsy Rider
Brompton front axle thread?
« on: 11 February, 2023, 10:31:52 pm »
Does anybody know the dimensions for Brompton’s standard front axle? Is it 5/16" 26tpi or M8? If M8, is it fine (seems more likely) or standard?

There is some surface rust on the front axle nuts on my Brompton but not on the bling Ti nuts on the rear axle of my B. Swapping the front nuts to Ti (from a non-bike supplier) would solve that problem forever.
Wheel meet again, don't know where, don't know when...

rogerzilla

  • When n+1 gets out of hand
Re: Brompton front axle thread?
« Reply #1 on: 12 February, 2023, 07:18:11 am »
Many stem expander bolts are M8 x 1.25, if you have one to try. 
Hard work sometimes pays off in the end, but laziness ALWAYS pays off NOW.

Re: Brompton front axle thread?
« Reply #2 on: 13 February, 2023, 04:39:07 pm »
Many stem expander bolts are M8 x 1.25, if you have one to try.

ISTR M8x1.25 is the bog standard M8 thread. I would guess (but don't have the humongous thread tables on this box to check) that M8 fine would be 1mm pitch (like M7 and M6 standard).
Surely the OP has access to metric and imperial thread gauges and a vernier caliper? Of course you would need as much thread showing as possible, 25.4(mm) is very close to 26 (tpi).

LittleWheelsandBig

  • Whimsy Rider
Re: Brompton front axle thread?
« Reply #3 on: 13 February, 2023, 04:50:12 pm »
Calipers, both digital and vernier, but no thread gauges. I have found that thread ODs can be a little undersize than their nominal dimension, due to rounding of the thread peaks.

I am pretty lazy about measuring it since I would have to remove the wheel. I hoped that this information would actually be recorded somewhere as just about every other thread dimension on a Brompton is.
Wheel meet again, don't know where, don't know when...

rogerzilla

  • When n+1 gets out of hand
Re: Brompton front axle thread?
« Reply #4 on: 13 February, 2023, 04:55:36 pm »
Thread ODs are always undersize...counter-intuitively, an M8 bolt will always drop through an 8mm hole.
Hard work sometimes pays off in the end, but laziness ALWAYS pays off NOW.

Re: Brompton front axle thread?
« Reply #5 on: 13 February, 2023, 05:20:25 pm »

LittleWheelsandBig

  • Whimsy Rider
Re: Brompton front axle thread?
« Reply #6 on: 13 February, 2023, 05:30:16 pm »
So you found that too.
Wheel meet again, don't know where, don't know when...

Re: Brompton front axle thread?
« Reply #7 on: 13 February, 2023, 05:40:17 pm »
5/16" is definitely looking promising:  https://josephkuosac.com/product/brompton/hub-nut/

LittleWheelsandBig

  • Whimsy Rider
Re: Brompton front axle thread?
« Reply #8 on: 13 February, 2023, 06:05:23 pm »
Bugger. That means I need to get the expensive aftermarket nuts, rather than off-the-shelf metric Ti nuts.
Wheel meet again, don't know where, don't know when...