i've been doing some searching on the locost site and have unnerved myself a little.

I am fitting a sump guard to the bottom of the car using 4 rubber exhaust bobbins as spacers to allow a cushioning effect of any knocks the sump guard takes.

The bobbins have an M8 size bolt and so my plan was to use four 8 mm rivnuts in the bottom of the chassis. Is this a bad idea?!!? some say the hole is too large and weaken the tube. Of course any drilled holes will weaken the tube a bit but will an it weaken it enough to cause problems?

thanks matt

Well an M6 rivnut needs a 9.4mm hole drilling for it, so I wouldn't like to go for an M8 rivnut in a chassis tube!

I only use M5 rivnut's for the same reason!!! (7.2mm hole)

[Edited on 31/8/09 by Steve Hignett]

hmm, this is what i was thinking, i think it going to need an 11mm hole maybe i'll get some other bobbins!!

Why not just weld a 3mm plate to the bottom of the chassis, that's what I did

can you not weld some mounting plates to the chassis tubes then bolt the sump guard to the plates?

andy

[Edited on 31/8/09 by handyandy]

unfortunately i dont have a welder or the skills to weld! i did think about the plates though i think i'm going to go with the m6 rivnuts as i have used these before with other things like the scuttle and have never had a problem, many thanks though for you kind suggestions, always good to air the problem to clear your mind!!

can you not get someone to weld the plates onto the chassis rails?
if you were closer i would do it for you.

andy

If you are using exhaust bobbins, will the other side of the bobbin (which I assume is also M8) not pass through the chassis tube? If so, then it's just an 8mm clearance hole that you need...

steve, would it realistically be safe to do this? not sure of the length just now but i could test it out

If you have the bobin on the bottom of the chassis hanging down then the sump guard. Are you going to have enough clearence between the gaurd and the road....

I put a sump gaurd on mine and found it scraped even goinind down the drive - reduced my clearence to 55mm.....

Gave up and spent the money on a tiger sump and never looked back.

A sump guard mounted on rubber bobbins will get ripped off as soon as it hits something substantial. Best to mount it solid to the chassis and put some rubber between it and the sump.

mad 4x4 - my sump is higher than a tiger sump but need that extra protection as the roads around me seem to be particully bad!

Phil.J - I dont think this is true, a sump guard offers you a glancing blow, if you hit something so hard that it would rip the bobbins off, imagine what it would have done to your sump!! i'd rater pay for 4 more bobbins than a new sump and a possible bottom end rebuild!