Rear wheel alignment problem

[nfs13b]

Hey All,

Not sure if any of you have this problem or if its just me (probably) but after I drag race my rear wheels go out of alignment.

I have some nolathane(?) bushings in the rear control arms and new bolts etc for them and we do them up really tight but after a run the wheels have moved forwards out of alignment.

If I got a solid bushing (like a brass one) do you think this would help the problem or does anyone have any other suggestions that might help?

Thanks

[Sheck]

not sure if this helps but i would of assumed that it was the bolts that would be slipping. try some paint markers in them to prove that theory. And if that is right then metal bushes wont help unless you ditch the eliptical bolts and weld in some off center metal bushes (to get the desired offset and toe) then use round bolts to lock it in place.

just my ideas
dave

[nfs13b]

I have marked the bolts, and we re-adjust them after each run.

[manga_blue]

nfs, you're going way beyond our collective experience with what you're doing.

My gut feel says you need to double the tightening torque you can put on the suspension bolts. I reckon that means increasing the bolt size by 2mm (from 8 to 10 I think) and using top quality high tensile steel. So you'll need to drill out the centre pins as well and get a machine shop to fabricate the new bolts and fixed cams as well as make up new cams for the nut end.

If that fails then maybe you're up for fundamentally re-thinking the control arms and adjusting bolts, even going beyond an MX5 sub-frame.

[nfs13b]

At the moment I am thinking about maybe seeing if I can weld a strip across the bolt to the arm to hold it in place (once aligned)

[bigdog]

If it was me I'd be fabricating new arms with rose joints for adjustment and do away with the eccentric bolt idea... but you wouldn't want to drive it on the road then

[nfs13b]

it doesnt get dríven on the road so thats fine.

eventually I will be going to a 4-link system with a 9 inch so dont want to be making up new control arms

[manga_blue]

At the moment I am thinking about maybe seeing if I can weld a strip across the bolt to the arm to hold it in place (once aligned)

Might work ... and maybe put a small bolt through the end of that strip onto the control arm somewhere.

[nfs13b]

I have been advised that mx5's have a brace that runs across the back of the 2 control arms (mine does not have this)

Can someone post up a pic so I can see it. Would this stop the arms from moving forwards and toeing in?

[manga_blue]

Right at the back of this photo is a brace across the bottom of the rear subframe almost under the diff and two arms coming forward from there that bolt onto the floor pan.

The arm across stiffens the sub-frame itself, the forward arms help stop the subframe from moving back and forward under braking and accleration forces.

It's worth putting on your car to help the subframe resists the forces you're putting on it but it won't help your cam adjuster problems. To fit it you'll have to weld mounting lugs onto the rear subframe near your rear lower control arm bushes.

Aftermarket braces across the back use the cam bolts and putting more strain on those is the worst thing you could do.

[wun911]

Apparently the new alignment bolts are better to hold the alignment than the old ones. (Only applies to NA)

[nfs13b]

Apparently the new alignment bolts are better to hold the alignment than the old ones. (Only applies to NA)

I have the new bolts

[manga_blue]

It's interesting to consider the forces you're putting on that car. You're lifting the front wheels a foot off the ground and you must be pulling around 2 g in acceleration.

There are two forces involved here that work sometimes together on the subframe and sometimes against each other.

The first one is the torsion exerted at the rear wheels which lifts the front. To picture how much that is, just imagine that you have rear hubs bolts that are frozen solid and your handbrake could never slip. Now imagine putting a socket and a 6 feet breaker bar on each rear hub nut and getting a few of your mates to pull back on the bars. How many of your mates would it take to lift the front 2 feet off the ground? All of that torque is being transmitted by the control arms through the inboard bushes and into the car.

The second is forward thrust. I guess you have the rear wheels dragging the rest of the car forward at 2g. That's the same as hanging the car vertically, nose up, by the rear wheels and tying on a second car to swing off the back bumper of the one hanging by the wheels. Again, all that thrust force comes onto the inboard rear control arm bushes. The front bushes are being mashed in towards the centre and the rear bushes are being dragged out.

Combine those torsion and thrust forces together and you realise why the cam-style adjusting bolts are twisting under the strain.

[fattima]

May sound a bit rough but since it is not a road car can you just tack weld the alignment bolts in place?

[nfs13b]

May sound a bit rough but since it is not a road car can you just tack weld the alignment bolts in place?

Also thinking of that as an option.... But if it doesnt work and I need new control arms does anyone have any spare ones?