Hi I am building a Haynes Roadster with MX5 engine but with Sierra running gear. Its someone else's failed project which came with a Pinto engine which I am stripping back to bare chassis and rebuilding.
I've been sorting out the rear suspension. I have found a lot of play in the suspension joints allowing changes to the toe in or out of the wheel. None of the bolts are fully tightened. I first found that the lower bolts comprised of one 12mm and one 10mm bolt instead of the correct 260 x 12 mm bolt. Solution found I thought. The 10mm bolt has been replaced with a 12mm temporarily while I source the longer bolts but there is still a lot of play. The crush tube dia is 12.1 mm but I see that the holes in RU1 and RU2 (the uprights) are as per the drawings on page 178 of 13mm. Before tightening this leaves a lot of play and I can see it moving when subjected to use on the roads.

Is this right?
or
Is the solution to somehow reduce the 13 mm holes to 12mm, replace the bolts with 13mm, replace the bots with 1/2" which will reduce the play.

Sorry if this has been asked before, I failed to find a similar thread with a solution looking back.

Having built my roadster I can confirm all the bolts are 12mm for suspension.

The best solution would be to cut off all the brackets that have been drilled incorrectly and replace with the correct sized holes

1/2 bolts would help but you may have to drill / change your crush tubes. I don't like the idea of having random sized bolts for suspension.

I've just drilled all my rear wishbone brackets out to 1/2" because I've made rosejointed wishbones and 1/2" joints work out cheaper.

Thanks Ben - I must say I am going to try and find another way around this if I can. It seems odd to me that the holes are all shown as being 13mm dia in the book and there has been no update that says it is an incorrect dimension. What dia holes are there in the commercially produced uprights? Are they 13mm as per the book as well?

Not sure on commercially produced ones but I would have thought they'd all have used some knowledge of car building and put the correct sized holes in.

Are you sure the crush tube is 12.1mm ID, ones I have seen have been 13mm ID?

Cheers
David

Yes they are 12.1mm - one was actually 11.8 and I had to take it out to 12.1mm
ian

I'd spotted the 13mm in the book and always thought it a little big BUT look in any engineering text book and a std clearence hole for a 12mm bolt will be more or less 13mm

Truth is, if I was building it myself, I'd go 12mm and easy the holes slightly if assembly proved difficult.

In practise, once everything is bolted up tight, nothing will move. If in doubt drive for a few miles then, check and adjust geometry again

Thanks for the replies - what I am thinking of is using 1/2" bolts which are 12.7mm and opening up the crush tubes to fit. I would prefer to use 12mm but the 13mm book specified holes put me off. I know 13mm is 12mm clearance hole size but most of the other holes where this is required are 12.5mm. I would be happy with that dimension. It does seem to be a pity that the book itself is so riddled with errors in dimensions after so long and a number of updates and reprints that would avoid this issue if they were corrected.
Yes Ben it is going to be a mix up of bolts and sizes and I would prefer otherwise but I am at least old enough to still have a toolbox full of BSF, whitworth and AF spanners and sockets so they will at least fit
thanks for your replies
Ian

I wouldn't normally suggest anything I saw on kit car crisis, they had a similiar problem but what they did was to weld a thick washer about 3mm with the correct size hole

David

Does it really matter?

The crush tube has a bolt through the middle which is clamped up. This clamps the crush tube in position. The bush itself then rotates around the crush tube - so this fit is critical. If you think about all the bolted joints used generally, very few use 'fitted' bolts.

Some interesting info here - https://www.fastenal.com/content/feds/pdf/Article%20-%20Bolted%20Joint%20Design.pdf

Including this snippet -
"With some shear joints; the ultimate joint strength depends only upon the shear strength of the bolts.
This type of joint is referred to as a “bearing type” joint. The amount of tension created in the bolts
during assembly is relatively unimportant as long as the fastener is retained in the assembly. The joint
member is allowed to slip until the fasteners come into “bearing” and prevents further slip. The fastener
in this assembly is basically used as a pin.
Other types of shear joints rely on initial clamp load to resist slip. This type of joint requires a frictional
force between the joint members. The shear forces have to overcome the friction developed by the
clamp load, which in most cases will be far more than the actual “shear strength” of the fastener itself.
This type of joint is common in the structural steel construction industry and may be referred to as a
friction-type or slip-critical joint."

As a test I would try fitting everything properly, torque the bolts up correctly and then get a crowbar and try and mve the crush tube on the bolt.

Thanks minicooper, yes I did think of welding thick washers, I was considering 5mm thick but the same principle. David, a very interesting read about bolts and stresses, thank you.
What have I done? I've bought some suitable 1/2" UNF (12.7MM) bolts from Norfolk Fasteners in Dereham today and the crush tubes are being drilled out to 1/2" as we speak. My main concern was the 1mm play in each hole 9" apart giving variable toe in or out either when tightened up or when under load. by doing what I have the play has been reduced to 0.3mm which is much more acceptable to me. Too late to try the crowbar I'm afraid.
Thanks everyone