Is a coarse thread a bad idea for a suspension bolt?

[E36Dan]

Afternoon all.

Question for the engineers/hobbyists. I've got a car (2001 MR2) which has aftermarket coilover suspension on.

The problem here is, as I've recently discovered, the holes for the suspension struts are slightly larger than that of the hub. This means that when I take off my suspension, my wheel alignment goes down the pan.

This seems pretty common on Mcpherson struts which affix in this way.


(image from Google)

I've been trying to think of a way around this and had the idea to try a countersunk bolt, but the only high-tensile M14 countersunk bolts I can find are coarse thread (2.0). I think the countersunk head will centrally locate the strut through the hub, unless anyone can suggest a better solution.

I don't think I've ever even seen a thread as wide as this on a car before though, so alarm bells are ringing. I'd like to try it but I'm just not sure of the implications of doing so.

Here's a video showing the suspension play caused by the "generic" shocks. https://youtu.be/g2Vdi4kXoX4?t=638

Thoughts?

[Ransoman]

What you describe is normal, don't try to bypass it.

If it is any help, all workshop manuals i have read describing this setup has recommended pulling the top of the brake disk outward and downward as you nip up the bolts and this gives the recommended alignment.

[Krikkit]

You could use a shanked bolt and have a sleeve welded to the outside of the coilover attachment?

[stevieturbo]

So you want to remove the ability to adjust the suspension ?

[996TT02]

Make up 2 "shim" plates per side with holes that are a precise fit for the bolts. Assy them beneath the bolts/nuts, tack weld them to the strut. That way bolts now have no play. Have an alignment done. Next disassy and reassy, hub will locate in the same place.

[E-bmw]

Call me pedantic if you like but surely the movement you describe won't affect your wheel alignment at all. It may affect your camber be a degree or so at most, and yes, whilst this isn't ideal are you sure it isn't just a case of the wrong bolts being used previously?

Surely, those bolts would be shouldered bolts & leave virtually no play at all?

Certainly ones that I have taken off similarly arranged cars before have been like this & in fact most are difficult to get in/out due to there being so little movement.

[Dave Brand]

E36Dan said:

I've been trying to think of a way around this and had the idea to try a countersunk bolt, but the only high-tensile M14 countersunk bolts I can find are coarse thread (2.0). I think the countersunk head will centrally locate the strut through the hub, unless anyone can suggest a better solution.

That plate you're bolting through is too thin for a countersunk head.

Secondly, never rely on a bolt thread for location.

Don't try to second-guess the original designers; they did it that way for a reason!

E-bmw said:

Call me pedantic if you like but surely the movement you describe won't affect your wheel alignment at all. It may affect your camber be a degree or so at most,

Call me pedantic, but camber is one of the elements of wheel alignment!

[E36Dan]

Thanks for the replies....

Ransoman said:

What you describe is normal, don't try to bypass it.

If it is any help, all workshop manuals i have read describing this setup has recommended pulling the top of the brake disk outward and downward as you nip up the bolts and this gives the recommended alignment.

Normal? It's crap! The original shocks don't mount with such variance.

Krikkit said:

You could use a shanked bolt and have a sleeve welded to the outside of the coilover attachment?

The original bolt is shanked - it's M14 which fits perfectly in the hub, but far too much play with the aftermarket shock mount - IMO!

stevieturbo said:

So you want to remove the ability to adjust the suspension ?

No. I have the ability to adjust toe and camber properly. I want this to be static so that when I remove my suspension my alignment isn't lost. This is a track car.

996TT02 said:

Make up 2 "shim" plates per side with holes that are a precise fit for the bolts. Assy them beneath the bolts/nuts, tack weld them to the strut. That way bolts now have no play. Have an alignment done. Next disassy and reassy, hub will locate in the same place.

Tacking 4 14mm shims to each strut sounds a bit hefty. Was hoping to just use a nice bolt... me no weldy!

E-bmw said:

Call me pedantic if you like but surely the movement you describe won't affect your wheel alignment at all. It may affect your camber be a degree or so at most, and yes, whilst this isn't ideal are you sure it isn't just a case of the wrong bolts being used previously?

Surely, those bolts would be shouldered bolts & leave virtually no play at all?

Certainly ones that I have taken off similarly arranged cars before have been like this & in fact most are difficult to get in/out due to there being so little movement.

Pedantic - not quite. More innacurrate/naive to the effects of a couple of mm on that area of the suspension and how that can effect the alignment of the wheel.

Agreed - these bolts are usually tight. Not happy with this play.

Dave Brand said:

E36Dan said:

I've been trying to think of a way around this and had the idea to try a countersunk bolt, but the only high-tensile M14 countersunk bolts I can find are coarse thread (2.0). I think the countersunk head will centrally locate the strut through the hub, unless anyone can suggest a better solution.

That plate you're bolting through is too thin for a countersunk head.

Secondly, never rely on a bolt thread for location.

Don't try to second-guess the original designers; they did it that way for a reason!

I was looking at a countersunk bolt with a shank down the hub - but if it's too thin then that's not ideal.

I guess it has a flat head on the OE bolt for a reason. Aftermarket shocks have caused this problem, not Toyota!

Cheers

[aww999]

Make/buy a collar that fits around the shanked portion of the OE bolt, and takes up the slack to the aftermarket part? The bolt is not the problem here.

[tapkaJohnD]

Dan,
You need an eccentric bolt, a widely used and accepted way to adjust and hold camber for MacPherson Struts.

See this - it's just the first of very many. Search for "camber adjust MacPherson strut": https://www.youtube.com/watch?v=Qe9AS99o3o8

JOhn

[E36Dan]

tapkaJohnD said:

Dan,
You need an eccentric bolt, a widely used and accepted way to adjust and hold camber for MacPherson Struts.

See this - it's just the first of very many. Search for "camber adjust MacPherson strut": https://www.youtube.com/watch?v=Qe9AS99o3o8

JOhn

No no no no

I removed the camber bolts. They were originally on my car but with camber bolts AND too much gaps doing the alignment was a nightmare.

I want this to be static. NOT ADJUSTABLE. It is not mean to be adjustable here.

Mcpherson fking blows

[227bhp]

They're there for a reason - to allow for some slight adjustment as one side will be different to the other.
If you want to lock it solid then the thread of the bolt has no consequence, using a C/S head will though so I wouldn't use one of those.
I'd do as per above and get some washers made up with a precise hole diameter and weld them on.

[tapkaJohnD]

E36Dan said:

No no no no

I removed the camber bolts. They were originally on my car but with camber bolts AND too much gaps doing the alignment was a nightmare.

I want this to be static. NOT ADJUSTABLE. It is not mean to be adjustable here.

Mcpherson fking blows

Ah, but they ARE adjustable. Live with it.
Or else sleeve the bolt.
JOhn

[JoeMk1]

What brand are the aftermarket struts out of interest? How much play are we talking? +/- 1mm or so?

I can only re-iterate not to use a countersunk bolt. You'll be concentrating all of the clamp load on two points vs the whole underside of the bolt head. EDIT no you wont, I'm picturing a slotted hole in the strut but it round on the MR2 doh!

As people have said the only solution is to find a way to reduce the size and control the location of the hole in the strut whilst maintaining the proper bolted joint.

I'd probably go for a small collar the thickness of the strut clevis that sits under the bolt head to locate the bolt during assembly. You'd only need it on the head side of the bolt as it's only for location.

Edited by JoeMk1 on Thursday 11th April 17:33

[E36Dan]

tapkaJohnD said:

E36Dan said:

No no no no

I removed the camber bolts. They were originally on my car but with camber bolts AND too much gaps doing the alignment was a nightmare.

I want this to be static. NOT ADJUSTABLE. It is not mean to be adjustable here.

Mcpherson fking blows

Ah, but they ARE adjustable. Live with it.
Or else sleeve the bolt.
JOhn

Adjustable from poor workmanship

It's just what happens with these generic mass produced items. Nevermind!

Thanks for the advice all, coutnersunk idea sacked off. Will just try to position them all in a standard place before alignment.

Cheers
Dan

[E36Dan]

JoeMk1 said:

What brand are the aftermarket struts out of interest? How much play are we talking? +/- 1mm or so?

I can only re-iterate not to use a countersunk bolt. You'll be concentrating all of the clamp load on two points vs the whole underside of the bolt head. EDIT no you wont, I'm picturing a slotted hole in the strut but it round on the MR2 doh!

As people have said the only solution is to find a way to reduce the size and control the location of the hole in the strut whilst maintaining the proper bolted joint.

I'd probably go for a small collar the thickness of the strut clevis that sits under the bolt head to locate the bolt during assembly. You'd only need it on the head side of the bolt as it's only for location.

Edited by JoeMk1 on Thursday 11th April 17:33

They're Meister R coilovers.

Cheers for the words!

[Ransoman]

They are supposed to be adjustable, it is normal. It is not bad workmanship, it is by design. If you don't understand this then you really shouldn't be working on your car.

[Richard-D]

E36Dan - I feel for you reading through this thread. The bulk of people offering suggestions are completely ignoring what you've asked and your responses. I think you might want to revisit 996TT02's suggestion as your response suggests you've misunderstood him. His suggestion will add very little bulk.

Another option would be to ream out the existing holes to be a close fit on a bolt with a plain shank.

Edited by Richard-D on Friday 12th April 18:26

[SAS Tom]

If it was me I’d either get some collars made up which is probably the best option or make the holes in the hub bigger and use bigger bolts.

[gordmac]

Once the location is correct drill and tap it and dowel with a setscrew, say M6.