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Roll bar bolts
rodgling - 3/6/10 at 02:49 PM

I'm about to attach my roll bar and am wondering about bolts. The kit I'm using supplies 12 M8 class 8.8 bolts, but I have bought some M8 class 12.9 bolts - is it sensible to use the highest grade available, or are there other factors to consider that make 8.8 a better choice?

BenB - 3/6/10 at 02:57 PM

12.9 every time in my book. 8.8s are cheaper. The only other advantage of 8.8s are a wider range of bolts available. But if you can swap a 8.8 bolt for an identical 12.9 one then I would every time.

nick205 - 3/6/10 at 03:25 PM

One question...what is the roll bar bolted to?

Most bolt on roll bars I've seen are bolted into rivnuts, which IMO would fail long before an 8.8 bolt.

Danozeman - 3/6/10 at 03:26 PM

As nick says whats it bolting to? Theres no point putting decent bolts in if it bolts to sod all.

flak monkey - 3/6/10 at 03:29 PM

quote:
Originally posted by Danozeman
As nick says whats it bolting to? Theres no point putting decent bolts in if it bolts to sod all.


Theres no point in fitting one if it bolts to sod all....

snakebelly - 3/6/10 at 03:45 PM

have to say i have never seen a roll bar bolted into rivnuts, you would have to be nuts to even consider that!

rodgling - 3/6/10 at 04:00 PM

It bots through four substantial (i got through several drill bits drilling the holes) steel plates welded onto the chassis, so I think that aspect is fine. No rivnuts I'm happy to say :-)

LBMEFM - 3/6/10 at 09:20 PM

I would also say it does need struts to brace it.

sdh2903 - 3/6/10 at 09:53 PM

Took mine up to M10 12.9 spec, just didnt think that the M8's looked beefy enough.

Maybe a bit overkill but not a bad thing with a roll bar!

iank - 4/6/10 at 07:42 AM

quote:
Originally posted by BenB
12.9 every time in my book. 8.8s are cheaper. The only other advantage of 8.8s are a wider range of bolts available. But if you can swap a 8.8 bolt for an identical 12.9 one then I would every time.


Not completely true. When they finally overstress 12.9 snap 8.8 bend. That can make the difference between losing a wheel/the front brakes so suspension shouldn't use stronger than 8.8. For a roll cage it shouldn't matter though.

This is the same reason crane hooks aren't made of high carbon steel, you want them to start straightening rather than snapping like a carrot.

[Edited on 4/6/10 by iank]

rodgling - 4/6/10 at 10:10 AM

hmm, that sounds like a strong argument for using 8.8 - I wouldn't want them snapping off in a crash. I'm confused...