just got my suspension bushes today and with the help of a little grease and the bench vice I pressed them into one tube of a wishbone

then pressed the crush tube home, however once I fitted the bolt and washers etc I was appalled at how much play/slop there appears to be until its done up tight? is this normal

also the fact that the bolt kit that I purchased has the full size shank of the bolt in one hole of the bracket, but at the other end of the bracket its on the threaded portion


I work to very high tolerances with my job and things are either right or wrong in my opinion.

Im far from happy with this to be honest, but is it normal

fear of this situation was why I wanted to make it all myself with rosejoints.

[Edited on 24/5/10 by tony-devon]

Can you define where the slop is? Is it the crush tube in the bush, the bush in the tube etc etc.

Are you talking lateral or radial play? I assume you are fitting nylon bushes as you say you wanted to fit rosejoints to prevent play... am I correct?

The bushes should be a nice fit between the sleeve and the bush but the bolt should have some play. Its not the bolt that acts as a (plain) bearing surface.

Tolerances - reminds me of a joke about an engineer and a carpenter...

There will be some movement before the bolt is tightened; the crush tube and suspension bracket both have a clearance sized holes for the bolt, both of which will add up.

Because of the thin suspension bracket, it's almost inevitable that one end will be on the bolt thread rather than the shoulder, otherwise you'd be in danger of running out of thread before it was fully tightened. IOf course you could use a longer bolt and a very thick washer to work around this.

Once the bolt is fully tightened the crush tube will be firmly held by the suspension bracket itself, so provided the play isn't so large as to significantly affect the suspension geometry next time it's dismantled and reassembled I wouldn't worry too much.

quote:

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Originally posted by tony-devon

I work to very high tolerances with my job and things are either right or wrong in my opinion.

---

I have heard of some dealer/suppliers selling 1/2" crush tubes as 12mm which could explain the slop as 1/2" is actually 12.7mm????

Obviously could be fixed by using the correct bolt but would mean the u brackets to be redrilled to 1/2".

Cheers

Rich

ah aha

now then the bush was a tight press fit into the tube of the wishbone

the crush tube is a tight press fit into the black bushes

BUT when I offered up a bracket and slide the bolt through, I was horrified at the movement available

hard to describe, but

if the bracket was mounted firmly to the chassis as it will be then I reckon I could moved the wishbone inboard and outboard by a good bit

in my opinion it will be possible to slightly alter the geometry just by holding the wishbone in a certain place while tightening the bolt up

it looks like the problem lies with the ID of the crush tubes, the size of the shank of the bolt, and the size of the hole in the bracket

12mm dia bolt, 12.5mm hole in the mounting bracket and 13mm hole in the crush tube

so not a lot then LOL

it was always my thought that the bolt should be in the brackets on the full diameter shank at both ends, not on the threaded portion, surely thats just asking for problems?

quote:

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Originally posted by tony-devon
it was always my thought that the bolt should be in the brackets on the full diameter shank at both ends, not on the threaded portion,

---

once it's all tightened up, there should be NO movement between the crush tube or the bracket so it doesn't matter about the threaded shank in the bracket.

initial alignment will be hit and miss, but how tightly toleranced do you think the wishbone brackets are?

sounds like you have 1/2" crush tubes fwiw
tom

the tensile force in the bolt holding the crush tube against the bracket is what resists movement. The bolts can be threaded all along it will make little difference, but not preffered.

+/- 0.5mm on each bush isnt much. think how flexible the rubber tyre gripping the road is.

edit: wish i could type faster lol.

[Edited on 24/5/10 by dinosaurjuice]

If it was me I'd be buying some 1/2" bolts and redrilling the U brackets.

Richie tip, use normal nuts whilst faffing about, keep nylocs until the end of your build.

Cheers

Rich

yeah I have just checked and crush tubes are 1/2", holes in suspension brackets are 1/2" as well, so the cure is simple, lob the M12 bolt kit in the" it will come in usefull one day " box and visit the local fastners supplier

thanks guys for the swift and concise replies

I just trusted that all the bits would work together, can see that this is going to be just like any other build that I have done

make it up as I go along LOL

[Edited on 24/5/10 by tony-devon]

First mistake " Trust a supplier to get it right"!!! Theres not many that do that!

Great, easy fix, I can feel a bolt kit appearing on the bay! Glad you're sorted.

Take care

Rich

[Edited on 24/5/10 by RichardK]

Just make sure you get HT imperial bolts (grade S)

Namrick sell them if you struggle.
http://www.namrick.co.uk/acatalog/Home_U_N_F__HT_Hex_Head_Bolts_18.html (though I'm sure you know that if working in high precision engineering)

ETA: Not many suppliers in the 7 market get everything right first time - on the whole the prices have been driven so low by competition that corners get cut.



[Edited on 24/5/10 by iank]

You may want to get aircraft grade bolts which can be purchased with the full shank portion not threaded, only a small portion of the bolt has threads at the end. Refered to as AN, look at Aircraft Spruce and Specialty website.