Any of you mechanical experts ready to educate this sparky as to which bolt I can use where. Just need a quick lesson in bolt steel grades.... I want to use stainless where I can but know that in high load areas I need to use high tensile bolts. Which areas in particular must have these bolts?

Dave Bailey

Mainly, suspension, prop bolts and if you have them, roll bar bolts. Suspension will do with 8.8, since most are 1/2". Prop bolts will depend upon type, but again, I'd guess 8.8 to be ok. For the roll bar, I'd rather use 12.9 where possible. Sure there's some places I've missed, and just to be sure, I'd also use a min of 8.8 grade everywhere.

I wouldn't use Stainless onanything thast structural (suspension,prop,brakes etc)use minimum 8.8 grade

i;d also use 12.9 grade for the prop not 8.8

Ry

I did say it was a guess!

Seat belts need high tensile too. Cant remeber which but mr SVA will check.

thanks guys.....

once again more valuable info supplied...

this site is A1.

Dave B.

8.8 grade bolts are far more than adequate in most areas of the car. It takes 7 tonnes tensile, 4.6 tonnes in single shear and 9.2 tonnes in double shear to break an M12 8.8 grade bolt...

David

What is also important is the manufacturer of the bolts. I would prefer to use a 8.8 grade bolt from someone like Unbrako than an un-name cheapo 12.9 grade. Anyone can stamp a number on a bolt and pass it off as a "quality" fastener.

So I would also recommend getting bolts from Unbrako, Allen etc.

Alternatively use airframe spec bolts (AN series). These are available in all grip lengths in increments of 1/16" (no more cutting threads off), are plated and a known quality. Mr Skidmore on here sells them.

Borrow from your local library Nuts, Bolts and Fasteners Handbook by Carroll Smith. It will tell you everything.

John

Hi,
I would agree that 8.8 grade fasteners are perfectly good for virtually all areas of the vehicle. Seat belt mounts are supposed to be "S" grade or better which is the non-metric way of saying 8.8 grade. Remember that 8.8 grade are what most people call "high tensile" and that 10.9 and 12.9 are even higher and usually just an expensive extravagance. Also remember that a 12.9 grade bolt does not make up for using an undersized fastener.

I think the only places I have used higher than 8.8 grade is:
1. Steering pinch bolt on the Ford Escort steering rack which is 12.9 grade and the other pinch bolt on the steering column is also 12.9 grade.

2. Driveshaft to diff retaining bolts - 12.9 grade socket caps.

3. Propshaft to diff bolts - 10.9 grade from burton power. Interestingly the ones from the gearbox to propshaft were bought from Rimmer Bros and they are only 8.8 grade. I think the main difference is that they are nut and bolt whereas the prop to diff are set screws and perhaps more likely to strip threads.

4. Lower front balljoint retaining bolts. There are 2 M6 12.9grade bolts and 2 larger (est M10 or M12) 10.9 grade bolts.

I think that's all.

Cheers,
Craig.

thanks again guys!
Dave B

I did not really think to much about the bolts i have used screw fix ones http://www.screwfix.com/app/sfd/cat/pro.jsp?ts=76383&id=11232 are these ok or will i need better ones ?

They will be fine