Suspension Mount Bolts

[2HP]

[attachment=2]Full bolt c.JPG



Hello there, grateful for any pointers on how to rectify a problem I have with rattling front suspension. Noise traced to wobbly front suspension mount bolts. Both sides same problem. The chassis is a 1990s galvo job from 'Wheels' who are no longer with us and therefore can provide no advice. The mount on the chassis comprises a steel tube with a hole threaded the full length in something resembling M14 1.25 pitch (or thereabouts), but it may have been tapped sloppily or they used the wrong tap. The male threads on the OEM bolt do not use the full depth of the threaded hole in the chassis mount - there's about a further 30mm of thread available in the hole, so in theory it would take a bolt 30mm longer. With the tapped threads being sloppy the shoulder on the bolt wobbled & delivered a hammering to the outer 15mm or so of the hole, which, being also tapped (but really should not have been), resulted in the outer part of the hole (which mates with the bolt shoulder) becoming worn & ovalled.

See attached pics.

As with many bodgers no doubt i was proud of my initial low effort zen-like repair. It was quick, easy & stopped the rattling. 1/4" copper pipe tapped with a M14 tap and screwed up the bolt and persuaded over the shoulder. i may have also given the crude copper sleeve, when on the bolt shoulder, a quick shave or sand on the lathe to make it fit the hole, i can't quite remember now. then the bolt was screwed back into the chassis and the copper squashed up , successfully taking up the play. This bodge worked for about 1000/1500 miles before the dreaded rattle returned. The copper on the bolt shoulder in the pic appears threaded only because it has been screwed into a threaded hole - it's still not far off m14 at the shoulder.

I have various ideas for a better class of repair this time around and am dithering as to which one to go for:

[1] i could ream out the outer 15mm of the hole and turn up a brass sleeve - this is a variant on the original bodge but requires me to ream the hole accurately and fully central to the remaining m14 hole, which i'm not convinced i can do without messing up the remaining serviceable female thread.

[2] i could ask an engineering firm to make me up a pair of bolts to the same spec (high tensile), but with the m14 long part 30mm longer, thereby using up all the available thread in the mount hole. (i had considered trying to source some high tensile threaded rod but fear the shouldered part of the bolt is shouldered for good reason and if threaded instead it would just shear.

[3] i could buy a m14 1.25 pitch spark plug repair kit. these come with an M16 tap and threaded inserts about the depth of the shoulder. some of the inserts are heli (which i'd never get out if i needed to) and others are available in copper. pretty sure this would work for a while, but of course the bolt shoulder would be mated into a tapped m14 hole rather than an ideally untapped m14 hole, so not convinced it would be a lasting repair.

[4] cut a wee slot in the out end of the mount hole, screw in the bolt, and weld up the slot. i know this would take up the play but fear the heat may weaken the bolt and i'd never get it out again if it sheared.

All and any pointers gratefully received. thanks very much

[AlanM]

New shouldered bolts are available from ECAS 2CV Parts, albeit a bit pricy. You could clean off the galvanising, screw the bolts in then tack them in place

[Davidm]

A couple of weld tacks should secure the bolt and if the tacks are in an accessible position could be ground or filed off if you need to remove the bolt ?
I can only think of one idea to add to your list of options -
Turn a shallow shoulder on the bolt where it mates with the threaded hole with a diameter of say 15mm. The depth of the shoulder would be limited by how much you are prepared to reduce the depth of the hexagon for fitting/removing the bolt.
Make a spacer of the same thickness as the shoulder machined on the bolt and weld this spacer to the tube with the threaded hole. This spacer would have a hole to give a good fit with the shallow shoulder you made.
Davidm

[Davidm]

Just having another look at ECAS part 6252A and your chassis bolt photos. There looks to be quite a step change in OD from the threaded end of your bolt to your copper sleeve. The ECAS picture shows the chassis end should be M14x1.5 so I wonder, as you mentioned, could the chassis have been tapped the wrong size - perhaps M15x1.5 or even M16x1.5 ? Have you got taps or bolts or thread gauge to confirm what the chassis thread is ?
Davidm

[2HP]

Thanks for your advice and comments Alan & David.

Got me thinking all right. I'd assumed that with the bolt being hi-tensile steel and the chassis mount mild, that the bolt was essentially 'good as new', despite looking old. I will certainly check out other bolts to see if they're any bigger - I have a few other 2nd hand bolts from a scrapped low mileage deuche somewhere in a box of bits and if there's any perceptible difference then I'd certainly look to either using them or buying new bolts as part of the fix.

The suggestion of a few tacks of weld is also good. If i tack the end of the chassis mount onto the built-in 'nut' (hex shoulder thing) on the middle of the bolt, then those would be easily removed if required.

For belt and braces I think I may, as the part of the hole in which the shoulder sits is worn ovally and oversize, in addition to a new/newer bolt and a few weld tacks, still make a sleeve for the shoulder of the bolt and bore the shoulder out nice and round to fit.

I suspect probably the best and simplest fix would be to bore out the entire hole, drive in and then weld in place a steel pipe tapped correctly to M14 except for where it mates with the bolt shoulder, and of course use a new/decent bolt. But I can't bear the thought of making a dog's dinner of it and ending up with something that's beyond my bodging skill level to remedy.

I do think the original hole was probably tapped incorrectly, at least for the OEM bolt, not least because they did not leave an untapped m14 section to mate with the bolt shoulder, i.e., in just the area where it was going to get a hammering when damping the suspension. It could well have been tapped to m15 too, or some imperial equivalent larger than m14. The thread pitch is however definitely 1.25mm, i.e., the same as on the OEM bolt. I wondered whether Wheels (the chassis makers) used a bespoke bolt, but we'll never know as they have ceased trading.

Once again thanks for your thoughts/advice. I'll hopefully be posting up some pics of the fix in a few weeks.

Cheers

[billdavies]

2HP
Ive just looked at your photos and counted the threads per 10mm, there appears to be 5 or 5.5 which would would equate to a thread pitch around 2mm plus. Do they make 14x2mm?
It could be an imperial size but my tables are in the frozen garage just now.
I think they used a non standard bolt
Bill

[Ken Hanna]

2HP,
perhaps it's time to clear up a few inacccuracies?

First, the thread size on a damper stud is M14 x 1.50 on the chassis side ( and M12 x 1.25 on the damper side).

Next, the damper mounting sleeve should be counterbored 15mm diameter to a depth of 'about' 19mm.

I do have some history with these items, having sold 2,700 replacement chassis, each one usually having 4 damper mounts...

https://flic.kr/p/2o64pGs

https://flic.kr/p/7Cy3YR

Ken
p.s. Welding the studs in place is invariably a futile exercise.

[2HP]

Thanks Ken/Bill.

I am blind, measured the pitch on the wrong side, can't count or possibly all of the above! I've just remeasured between 11 peaks (ten gaps) on the M14 side and they total 15mm, & no idea what i did previously to arrive at 1.25mm pitch but it was clearly wrong.

So would a 19mm deep 15mm ID brass or steel sleeve work for any length of time? Or go for partially boring out the Wheels mounting sleeve and welding into what remains of it a full depth cylinder/sleeve with the correctly tapped hole (M14 x 1.5) and 15mm ID 19mm deep hole for the bolt shoulder ?

Wondering why the shoulder area of the original Wheels sleeve hole was threaded at all then, hardly matters now though. Wheels had a good reputation at the time if i recall correctly, but that was presumably before SLC. I bought a Falcon chassis from Bird at one point (late 80s). Weighed an absolute ton, didn't use it in the end, & sold it on after reports they were using an inaccurate jig, much fettling/cajoling required to fit bumpers, etc.

[Ken Hanna]

2HP,
re. "I do think the original hole was probably tapped incorrectly, at least for the OEM bolt, not least because they did not leave an untapped m14 section to mate with the bolt shoulder, i.e., in just the area where it was going to get a hammering when damping the suspension."
.
I've double-checked the clearance between the counterbored section of an original damper mounting and a stud, which is 'about' 0.75mm, so there's no way it needs to be a close fit.
As long the studs are tightened to the correct torque ( 21.5 kgf.m / 152 lbf.ft ) there should be no tendency for it to 'shuffle' under the cyclical loads imposed by the damper.
Note that because Citroen did not mention whether that specified torque was with 'dry' threads and I have always installed those studs with plenty of grease, a reduction in torque of 20% was used.
Ken