Hi all,

Following on from my previous post about checking front bearings:

http://www.locostbuilders.co.uk/forum/3/viewthread.php?tid=165500

I have done as instructed but the front left still has more play than the right. The right has no noticable movement at all when wobbled top and bottom, not even a smidge. The left has a small amount that I dont think will effect the handling but I cant easily quantify how much it is. Almost to small to see when looking at the wheels but I can feel it. Should I tighten the retaining bolt further to take this play out or really not worry about it?

Also I am now checking the rear. I have play there aswell. It seems the long bolt that goes through the lower part of the hub and wishbone seems a smaller diameter then expected. This is allowing play that I cant wobble when its all tight, I think because it pinches it all tight, but when loose it moves, I know thats obvious but surly it should be tight around the bolt and not allow the washers biting against the edges to stop it moving? The movement may equate to 1/2deg camber. I guess this would make a difference in handling. How can I solve this? Imperial metric bolt swap? I have attached a pic below to show you. I have not measured the hole bolt size yet.



Im sure somebody with knowedge mentioned this on one of my posts before. Procomp maybe?

So to conclude. Is it ok to have some wheel movement and will it affect the handling, again obvious I know but please quantify and is wheel movement normal?

If no then what should I do about above?

Thanks again for your help. Please do give me any advice on setting up the striker better or solving little handling problems with it. I will be getting it corner weighted and geometry set up at a later date so if anybody can recommend a good place to do this in the SE London area I would be greatful.

Biz

I can't really answer the questions in regards to if it will affect the handelling. However the bolt should never be placed in shear i.e. if you can feel play from the bolt being able to move then the bolt isnt tight enough. The force supplied by the bolt against the suspension crush tubes, suspension brackets and upright should create enough friction to prevent the joint from moving. After all the crush tubes, brackets and uprights remain stationary, it is the poly bushes which move around these.

wouldn't worry about it. there is more play in the rubber bush than that hole. the only way to completely eliminate the play would be to rose joint the suspension arm and get a better fit on the bolt hole.

it really depends what you want from the car. if you only intend to track it then rose joints are fab. if you want to drive it on the road then you will be replacing the rose joints every year, like nash has just had to do on his indy after 12months of hacking about round the uk and france.

Hi

It is simply a case off 12mm bolts being used where 1/2" bolts used to be used. So that means that every suspension joint has 0.7mm of play. That will equal a huge amount of toe / camber / castor change and means that having a proper setup is pointless until the problem is rectified.

It's worth pointing out that RAW - MK ( Inc the indy R ) and Mac 1 all have this problem and all have told customers that it is perfectly acceptable and that it will not matter when the bolts are tight.
The truth is after every pothole/bump or kerb taken when trackdaying you will have very different geometry. All should be ashamed. And i also think that all the manufacturers should rectify the problem if the customer so wishes FOC.

Cheers Matt

here we go again

Seems like a straight forward comment to me, and if it is the case its a simple fix that should be expected to be done. Will certainly be checking mine for asimilar situation.

It does look like small bolts to me as well, you can see the gap!

You need a set of 1/2" UNF bolts, on mine I had to lathe up a long bolt for my rear uprights as I could not get anything long enough from a stockist.

Regards Mark

thats the nice thing about building your own car from scratch. all my 12mm holes are 12mm and i machined all my own stainless crush tubes so i know they all have 12mm holes too.

matt you are correct about things possibly moving when you hit a bump but i seriously do question if the average driver could ever tell if something had moved.

if you can get a 1/2 inch bolt to go through your rear hub carrier then thats an easy fix, if you cant then ask yourself is it worth the bother for a road car?

12mm bolts in a 1/2" hole is very poor engineering, but if the bolt is fully tightened there should be no noticeable play when the upright is moved by hand (though as Mat says, hitting bumps on the road is a different matter altogether).

Check to see if the bolt is getting 'thread bound' at the other end, this would mean the bolt could be tightened as much as you want but not provide any more clamping force. Then throw the bolts away and get some 1/2" items of a suitable length.

quote:

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Originally posted by Tatey
I can't really answer the questions in regards to if it will affect the handelling. However the bolt should never be placed in shear i.e. if you can feel play from the bolt being able to move then the bolt isnt tight enough. The force supplied by the bolt against the suspension crush tubes, suspension brackets and upright should create enough friction to prevent the joint from moving. After all the crush tubes, brackets and uprights remain stationary, it is the poly bushes which move around these.

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Another opinion from a friend of mine when I asked him about this. He is a long time engineer/car designer.

To some extent industrial applications require different rules to automotive, for now we will stick with automotive.

A bush is basically a pivot, with or without compliance. Rose joints are non compliant and in real terms should be attached with a ground shoulder pin tensile 12.9 however this requires expensive machining of the mounting bracket and provides little clamping force it also has the tendency to corrode and seize making removal almost impossible, much too hard to drill hence only full race spec cars fi/f2 etc use them in automotive applications.

Rose joint or polly bush using bolts of 10.9 or greater tensile strength, some clearance between the bush tube/rose joint spherical bearing and bolt is desirable to prevent seizure and allow for some misalignment of mounting brackets/simple cheap manufacturing.

Now the technical bit, if you take the clamping pressure of the bolt if tightened to 55/65 lb’ft of torque this would give approximately 4 tons per sq inch of clamp pressure, now if you take the surface area of the tube ends this is approximately 1/20th of a sq inch therefore the clamping pressure on the tube equates to approximately 80 tons per sq inch, if by any chance you apply enough pressure to move the tube I don’t think you will be in any fit state to worry about it, for that matter I don’t think there would be a lot left of the car!

Set up. I agree that setting up would be easier if there was no play in tube/bolt however set up is about dynamic loads not static therefore the following procedure should be applied with any suspension that has flexible bushings.

quote:

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Originally posted by rdodger
Another opinion from a friend of mine when I asked him about this. He is a long time engineer/car designer.

To some extent industrial applications require different rules to automotive, for now we will stick with automotive.

A bush is basically a pivot, .....
etc
etc
....... that has flexible bushings.

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quote:

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Originally posted by loggyboy

quote:

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Originally posted by rdodger
Another opinion from a friend of mine when I asked him about this. He is a long time engineer/car designer.

To some extent industrial applications require different rules to automotive, for now we will stick with automotive.

A bush is basically a pivot, .....
etc
etc
....... that has flexible bushings.

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In laymans term what exactly are you trying to say!?

[Edited on 23/1/12 by loggyboy]

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quote:

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Originally posted by rdodger
That using M12 isn't a problem.

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As Ash said above, I knocked out my Rose joints after 12 months (and 11,500 miles) because of 12 mill bolts in a 1/2 hole. So this winter with the help of ASH's lathe, I now have machine spacers and sleeved rose joints so its all tight and I fully expect to get a lot more life from the suspension because of it.

I had mine, corner weighted, ride height and geometry set up last week and I will put a few hundred miles on it over the next two weeks and take it back for a recheck once its all settled down. The guy who did it said I would be wasting my money if I didn't take the "slack" out of it before I got it done.

................Neil

Having given this some thought I think I am going to change to 1/2" bolts. I figure even if it makes no difference when they are fully tight it's got to make life easier to set up the suspension.

The question is where can I get a bolt long enough to go through the rear upright. It needs to be about 9" long. The longest I can find with the likes of Namrick is 6"

[Edited on 24/1/12 by rdodger]

[Edited on 24/1/12 by rdodger]