Board logo

Front End Wishbone Bolts
Barkalarr - 24/11/13 at 07:53 PM

I'm replacing all the front end wishbone bolts

What size (diameter) are the bolts for the the poly bushes?

I've tried these's (pic below), but they're a bit floppy. Are these a UNF?

Description
Description
Description
Description

The ones that came out were not right because they were threaded all the way down, they were regular bolts and not the partially threaded ones.

HowardB - 24/11/13 at 07:59 PM

I may be wrong, but as you have bolts that say 8.8 and A2 you have shown us the grade of the steel used and not the thread form. In order to determine if it is UNF, measure the bolt diameter and count the threads per inch,.

If they are metric say M10 then they will be metric pitch,... M10 1.5mm pitch, M12 1.75mm pitch. etc

a 5/16UNF if my memory serves me correctly is a seatbelt mounting bolt,. so you may have one to hand to compare

hth

[Edited on 24/11/13 by HowardB]

designer - 24/11/13 at 08:01 PM

If you're replacing bolts, just measure the shank.

Barkalarr - 24/11/13 at 08:12 PM

I'm replacing the bolts because they're the wrong diameter. They're all floppy in the poly bush (floppy is a bit of an exaggeration, but you get the idea)

Don't worry about the length, it's the diameter of the poly bush I really need.
If I had one of those funky tools for measuring the internal diameter of the poly bush, this wouldn't be a problem.

Any ideas?

avagolen - 24/11/13 at 08:32 PM

Try using drills as gauges.

SPYDER - 24/11/13 at 08:47 PM

Seatbelt bolts are 7/16 not 5/16. Bolts marked A2 are stainless and not normally recommended for wishbone use.
I suspect that you have 12mm bolts and half inch poly bushes.

rusty nuts - 24/11/13 at 08:52 PM

quote:
Originally posted by avagolen
Try using drills as gauges.


Seconded! A cheap digital vernier from Maplins cost about a tenner and a thread gauge, a couple of quid would help or take a crush tube to your local fastener supplier. Suspect 8.8 will be a metric thread, probably 12mm a half inch UNF bolt would be 12.7mm, approx 0.028" difference. Also a bolt that is threaded for it's entire length is not a bolt it is a set screw, IIRC Kit Car mag did an article on fastenings a few years ago (and knowing them a few times since) in which they got it wrong showing a set screw as a bolt. Seat belt bolts are seven sixteenths UNF on just about everything I can think of

designer - 24/11/13 at 09:05 PM

8.8 is metric, but medium strength. You need 10.9 or 12.9 in metric for suspension bushes.

robocog - 24/11/13 at 09:53 PM

indeed - this has caught me out on one of my MOT's

I ended up ordering new bushes for my shocks - only to find out its was a metric bolt in an imperial hole causing the issues
I just bought imperial bolts n nuts to solve the issue

I still have the new bushes in a bag somewhere - shame as the shocks are due for replacement as they possibly wont go through another MOT (rusty piston showing)

Regards
Rob

nick205 - 24/11/13 at 10:29 PM

The MK suspension brackets are M12 from the factory, so unless they've been drilled out, that should be your start point. MK supplied crush tubes (the metal tube inside the poly bushes) are also M12 clearance to suit, so again unless they've been changed or modified the bolts should be M12.

Although not best practice, fully threaded set screws will be ok provided they are sufficiently rated. 8.8 tensile rating is OK for suspension bolts and will pass IVA and MOT. Best practice is to use bolts with a plain shank just long enough to clear the suspension bracket and a washer and locking nut to fasten. From memory, the closest you'll get to this with off the shelf bolts on the MK suspension brackets is M12x70mm. Also best practice to replace nylon type locking nuts after they've been undone.

HTH

[Edited on 24/11/13 by nick205]

simon cofield - 24/11/13 at 10:30 PM

Metric bolts will have a blue nylon insert on the nut and imperial ones will have a white insert.