Handlebar bolts

[pfm401]

Hello

My son has just bought a Calibre Bossnut (great bike!) to cut a long story short the handlebar bolts seem to be rounded off and I can’t get them torqued up properly (using a torque wrench) plus worry about loosening in future so I think the best thing is to replace them.

Any advice on good replacements? I’m pretty sure they’re M4 x20mm (pic attached). Does the material matter (steel / alloy) - don’t want them seizing in!

 

[Yellow Saddle]

Handlebar bolts have smaller heads than other commercial bolts, so your best place to start looking is at a bike shop.
Also, these are not just any old bolt, they are subject to plenty of strain cycles and thus have special profile thread and, the thread doesn't go all the way to the head. Get the right bolt.

Further, material matters. Aluminium (what I assume is what you mean by alloy, even though steel is also an alloy and aluminium is just, well, aluminium) is by no means suitable for the job.

 

[pfm401]

Handlebar bolts have smaller heads than other commercial bolts, so your best place to start looking is at a bike shop.
Also, these are not just any old bolt, they are subject to plenty of strain cycles and thus have special profile thread and, the thread doesn't go all the way to the head. Get the right bolt.

Further, material matters. Aluminium (what I assume is what you mean by alloy, even though steel is also an alloy and aluminium is just, well, aluminium) is by no means suitable for the job.

Thank you, yeah I agree a trip to the LBS it is. Never fan of guessing on eBay etc!

 

[fossyant]

Might be worth getting a set of assorted stainless bolts from Amazon/ebay - I purchased a used road bike a couple of years ago, and some of the bolts were rusty, so I replaced any with ones from an assortment pack. Worth having in stock.

 

[C R]

Also, these are not just any old bolt, they are subject to plenty of strain cycles and thus have special profile thread and, the thread doesn't go all the way to the head. Get the right bolt.

This caught my eye. Are they not ISO M4 threads?

 

[lostinthought]

This caught my eye. Are they not ISO M4 threads?

I suspect Yellow Saddle means that the bolts should have rolled threads (not cut) for durability's sake, despite the same size and pitch.

 

[C R]

I suspect Yellow Saddle means that the bolts should have rolled threads (not cut) for durability's sake, despite the same size and pitch.

Profile of the thread is independent from size and pitch, you could potentially have a thread with the same diameter and pitch as M4, but a profile different from ISO. This is what I understood from the post, but I suspect you are correct, they will be M4 threads with ISO profile but rolled instead of cut.

 

[pfm401]

Hmmm I'm sorry to sound stupid, but I tried an LBS plus a number of calls to Go Outdoors and Leisure Lakes bikes and so far striking a blank ...

So does the discussion about ISO and profile mean I can use a standard bolt (if push comes to shove) but it might not last as long? LBS said plain steel not stainless and recommended Screwfix!! Which ones have the galvanic corrosion issue does anyone know?

Seems a bit crazy to replace a stem for this without trying something, but safety first

 

[pfm401]

Sorry Go Outdoors stock the Calibre bikes and Leisure Lakes run concessions in the stores - they are the only sellers of Calibre bikes

 

[pfm401]

May try another LBS who seem capable of solving anything in my years with them - just a bit of a trek to get there!