Front Caliper Bolt Thread Size

[mattmalden 0]

Hi,

 

My front hub carrier needs replacing, I've a 'good' (not ovaled) 2nd hand one but one of the caliper retaining threads is completly stripped.

 

Does anyone think its a bad idea to fix this with an insert/helicoil? Off the top of your head does anyone know the thread size?

 

Cheers,

Matt.

[welshpug 1,645]

12 x 1.5

[mattmalden 0]

12 x 1.5

 

 

Cheers Welsh! Your advice has been much appreciated!

 

Do halfords sell helicoils / inserts? can't see them on the web? Ideally I need them today (not mail order) and ideally within walking distance. Don't want much do I!!!

[welshpug 1,645]

not a clue, I doubt it but you never know.

 

you would be best looking for an engineering shop, or a garage in fact, sods law most engineering shops dont do weekends, but I havent a clue about your area sorry!

[mattmalden 0]

12 x 1.5

 

 

Thats a funny thread pitch. Isn't M12 (coarse) pitch 1.75??

 

Would it be okay to insert a m12 coarse heli-coil and replace the high tensile bolt with something suitable?

I don't suppose that bolt see's much tensile loading - more sheer I'd have thought thats why its such a large diameter - in which case I assume the thread pitch is pretty irrelevant.

[Tom Fenton 1,536]

Do it properly, or buy a new hub. You don't mess about with brakes, it it was originally specified to be 12x1.5 then there will be a reason for it, most likely to stop the threads being pulled out of the hub.

[mattmalden 0]

Do it properly, or buy a new hub. You don't mess about with brakes, it it was originally specified to be 12x1.5 then there will be a reason for it, most likely to stop the threads being pulled out of the hub.

 

Hi Tom,

 

I absolutely agree with you, however in principal nobody I've spoken to has any qualms about helicoiling this thread. Agreed I should stick to the same diameter and pitch, but if you really think about what that caliper bolt is doing then is the thread engagement that essential? I'll bet there are many of us driving around with well worn caliper female threads due to how often the calipers are removed - for instance this hub seemed fine when I used to drive with it (approx 30k miles) but now I've discovered it was hanging in on two threads and stuck in place with silicon! The force on the bolt will mostly be shear I would think, I expect the diameter is so large for only that reason - the tensile loading would (i think) be relatively low.

 

I've known French cars to use all sorts of funny thread standards for no apparant reason - I wondered if this is another case?

 

I intend to Heli coil this one, ideally 12x1.5 but if not I'm going to go for metric coarse standard. If that happens I'll keep a close eye on it and mention it should it fail. It's a worry but there's a second bolt as backup - and its bound to be safer than it was for 30,000 miles before removal!.

 

Finally - have you seen the price of a Peugeot steering knuckle? Not cheap! Also 2nd hand is likely to be worn too - if not the caliper holes then the lower ball joint. If someone here could refurbish old knuckles (heat and shrink fit an insert for the ball joint, drill and slice it for the clamp, make good any threads) then I think you could be onto a good earner, not to metion a great and (from my point of view) needed service!

 

Thanks though Tom for the good point about the safety. Rest assured I'll take great care whatever happens.

Edited March 14, 2010 by mattmalden

[Tom Fenton 1,536]

I'd imagine that it is 12x1.5 to give more engagement in the hub, seeing as the length of the thread isn't much more than about 1/2".