Chainring bolts

Kell

Über Member
Hi all,

Somehow managed to lose the single bolt that attaches round the back of the crank rather than one of the ones for the holes on the spider.

Without wishing to purchase an entire new set just for one bolt (especially as I have a spare set of the other four) does anyone know where I can get hold of just the one I need?

It's the longer one in this picture:

31176.jpg
 

wisdom

Veteran
Location
Blackpool
Hi all,

Somehow managed to lose the single bolt that attaches round the back of the crank rather than one of the ones for the holes on the spider.

Without wishing to purchase an entire new set just for one bolt (especially as I have a spare set of the other four) does anyone know where I can get hold of just the one I need?

It's the longer one in this picture:

View attachment 465513
Try your lbs.
They may have 1 knocking about.
 
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OP
Kell

Kell

Über Member
I've just ordered another set.

And some more threadloc.

Interestingly, one of the comments on Brilliant Bikes (where I've ordered them from) is about these dropping out. Tighten too much and they strip, do them up too loose and they drop out.

The comment on the site also references that this is the only bike this has happened on.

Just another Brompton quirk.
 
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Tenkaykev

Veteran
Location
Poole
I recently changed the chainrings on my and my wife's bromptons.
The chainrings bolt threads were greased and not locktited.
 

mitchibob

Well-Known Member
Location
London, UK
I've just ordered another set.

And some more threadloc.

Interestingly, one of the comments on Brompton Bikes is about these dropping out. Tighten too much and they strip, do them up too loose and they drop out.

The comment on the site also references that this is the only bike this has happened on.

Just another Brompton quirk.
I really wouldn't use threadlock as this is an item that needs changing from time to time, sometimes mid-trip if I'm cycling to Wales and need the 44T for when I get there.

Just use grease, tighten appropriately, and keep an eye on them for the first few rides.
 
OP
Kell

Kell

Über Member
Well, a little while ago, I had to hacksaw off my chainring because one of the bolts had seized. And I change chainrings, sprockets and chain every six months, so it's not like it was on there for ages.

Since then, I've used copper slip to stop them seizing and kept an eye on them. But back in the autumn, I lost three bolts and mashed my chainring. Given the two options, I'd rather have one that didn't come out as that doesn't stop me riding in the same way that this did:

fc057d2c-39ff-423e-9602-4fedd5f25c58-jpeg.jpg
85b33bba-803b-42f8-ba32-8d0377fd663c-jpeg.jpg


It's a fine balance between over-tightening them and stripping the threads and leaving them too loose and having them come out.

I'm convinced that many of the Brompton problems come as an indirect result of the small wheels and the long stem and seat post. It all combines to make the bike vibrate a lot - if you don't believe that, try riding with no hands and see how much the bars shake. Those vibrations seems to shake stuff loose a lot more than on a 'traditional' bike with larger wheels, a triangular frame and shorter stems and posts.
 

Tenkaykev

Veteran
Location
Poole
Hi Kell,
I saw some info that said the chain ring bolts should be tightened to 10Nm.

I suppose that a torque wrench is not something most people would have.
When I fitted mine I did the usual tightening the diagonals and moving across one until they are just tight, then go round again cranking them up until I thought they were tight enough, then going back after a few minutes for a final tweak as they do seem to ease themselves back off a tad.

Just wondering if blue loctite may be an option though I do like coppaslip, I had a big tin of it next to a big bottle of Loctite 638 when I was working.
 

ukoldschool

Well-Known Member
I'm convinced that many of the Brompton problems come as an indirect result of the small wheels and the long stem and seat post. It all combines to make the bike vibrate a lot - if you don't believe that, try riding with no hands and see how much the bars shake. Those vibrations seems to shake stuff loose a lot more than on a 'traditional' bike with larger wheels, a triangular frame and shorter stems and posts.
Do you have a 'super firm' suspension block and Marathon plus at 100psi?
 

rogerzilla

Legendary Member
I have a firm suspension block with a jubilee clip round it and 100psi Kojak tyres. Nothing comes loose. Mind you, I have a Shimano BB and Sugino cranks!
 

12boy

Veteran
Location
Casper WY USA
I've always used grease or anti-sieze compound, tightened the bolts with a t-type allen and a nut holder on the inside as tight as I could get them, and did the opposite bolt as I worked around the chain ring. This usually takes 4-5 circuits. Every 1000 miles or so I check the crank arm and chainring bolts and usually find they are not loose at all. Getting the chainring bolts/nuts free when corroded together can be a real pain in the patoot, hence lubing the bolt and nut . Ive only used the swaged crankset that came on the bike or sugino crankarms but the bolts were all the same length.
 
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