Rear Tire to Wheel Well Clearance

[Michael]

The previous owner of my car had the ride height sitting a bit too high for my taste (approx. 5.5" front & 5.8" rear), so I recently lowered it to more appropriate and aesthetic dimensions of 4.8" front and 5" rear.

Now I understand why he had it sitting so high. I have less than acceptable tire to wheel well clearance on the right hand side (barely 1/4") in static condition. Too close for comfort (mine), since it appears to me that upward deflection of the suspension would cause contact between the tire and the inner fender lip. I would like to increase the clearance to at least 1/2" (similar to the left hand side) to eliminate any possibility of contact. The tightest clearance is right at the twelve o'clock position and minimal clearance probably extends at least 6" fore and aft of the apex.

The simplest and most obvious solution would be to trim the inner lip an appropriate amount, but I'm not really partial to that solution. I'm considering moving the suspension inboard the necessary amount by shortening the top turnbuckle (see photo) and the lower inboard heim joint in equal amounts to maintain alignment geometry. The upper link however, is already at minimum length, so I'd have to locate thinner jam nuts to allow shortening of the overall length. Any thoughts or recommendations on why I should not attempt this type of solution?

 

[Michel]

How thick are your bell disk ?
You can may be machine those some mm , then do the same to the wheel face and finally only screw at max all joints ( say ball bearings joint) so you can leave your actual jam nuts ( finding thinners will probably be hard ?)
Being said is not advisable to have ends completly into turnbucle and lower whishbone because one day or another you will need to proceed to some set up and you will be allowed only to "unscrew"
Smart solution will be to take off also small amount on those parts ; taking out one by one the parts will be the only way to prevent total suspension dismantling of course ( anyway to will have to do so on the lower ends as they need unbolting from the upright !!
Machining a little each part will give you more more thread avaible out of the spinner so you could ( doing asmall radial hole) fit a safety spring stuff

 

[Ian Anderson]

Can you move the whole rear clip to the Right and get 3/8 clearance each side?

how upright are your tyres?
if you adjust the bottom heim joint out 1/16 inch you move the top of the rim in the same distance so top of tyre in perhaps 1/8 inch

each little bit adds up!

ian

 

[Michael]

Michel, I will consider going that route if less invasive options are not deemed viable. If I can't find thinner jam nuts, I can have the existing ones machined down to a thinner profile. From what I've seen on other RCR Mk1 cars, they all seem to have the upper turnbuckles at the minimum length as a consequence of design. Jam nuts are at least 1/2" thick, replacing them with 1/4" thick (or machining them) would allow me to move the upright the required amount and leave a bit of adjustment for alignment purposes if needed.

Ian, the rear clam is very well positioned as it sits now. Any attempt to shift it right to gain clearance would create steps & gaps that would require much body work and repaint, plus it would likely create a clearance issue on the left hand side that doesn't currently exist. Tires appear to me to be very upright, but I'll have to put a level on them to verify. I'd prefer not to alter the camber if I can avoid it, especially since it would need to be done on the left side as well, which currently enjoys perfect clearance.

Thx Gents, appreciate the responses.

 

[Michel]

 

[Morten]

Hi, thinner tires would also solve the problem

Morten

 

[Michael]

Morten, I've considered that option. Switching to 275/50-15 would give me an extra 1/2" of clearance, but it would affect both sides and I don't want to alter the left side, which sits pretty good now.

 

[Randy V]

Put an additional .5° Negative camber into the rear on each side. Perfectly acceptable.
If your control arms are too long, simply shorten them. You can probably take up to 1/4” off of each end.

 

[Dr. Bob Woods]

Michael,

Have you checked your weight on wheels? You might have one diagonal heavier than the other and thus making one side droop more than the other. I agree with the more negative camber. It will probably help the handling as well.

-Bob Woods
Tornado GT40 in Texas

 

[Bill Kearley]

Carefull with the camber on a street car unless you want to invest in a tire company. I had about an inch and a half of tire to move inboard in order to center the rear clam, a big pain to deal with. I had to rotate the front clam, spider and rear clam clockwise ( from above ) and rework the left rear control arms, about 3/8 of an inch, to center things.

 

[Michael]

Yeah Bill, I'm not a fan of excess camber on a mostly street driven car. I think initially I'll adjust the upper link and lower control arm inboard heim in equal amounts to move the wheel inboard at least 1/4", and a bit more if necessary, without any additional camber. Does anyone know the size and pitch of the RCR Mk1 upper turnbuckle heims? I'd like to know before I pull everything apart, so I can start searching for thin profile jam nuts. I guess I can just call RCR.

Bob, planning to corner balance the car and realign everything once I have adequate clearance.

Thanks for your responses fellas.

 

[Bill Kearley]

It won't be the best, but you could also delete the lower arm jamnut and bottom out the Heim as well as one of the uppers . the gain may be about 1/2 an inch

 

[Dr. Bob Woods]

Michael,

By "corner balance" I presume you mean to get the sum of the weights on the diagonals equal. You will never get the left = right on both ends unless your car is absolutely symmetric.

-Bob Woods

 

[Michael]

Bill, yeah, removing the jamnuts and threading the heim joints in would work for sure, but I'd never run without them on primary suspension components. I've spent my entire career in aerospace manufacturing and I know better.

Bob, yes, corner balance equalizes weight on the tires diagonally from left front to right rear and right front to left rear. Not expecting absolute symmetry or perfect balance, close enough and I'll be happy.

 

[Randy V]

Yeah Bill, I'm not a fan of excess camber on a mostly street driven car. I think initially I'll adjust the upper link and lower control arm inboard heim in equal amounts to move the wheel inboard at least 1/4", and a bit more if necessary, without any additional camber. Does anyone know the size and pitch of the RCR Mk1 upper turnbuckle heims? I'd like to know before I pull everything apart, so I can start searching for thin profile jam nuts. I guess I can just call RCR.

Bob, planning to corner balance the car and realign everything once I have adequate clearance.

Thanks for your responses fellas.

How much camber do you have now and what do you consider excess? 1/2 degree to 1 degree negative will not give you terrible looks or tire wear.
I would never advise the delete of a jam nut. Not only does that nut keep things from rotating, it also takes out *all* slack tolerance in the control arm / heim (rose) joint...

 

[Michael]

Randy, I'll have to look through the PO's paperwork to see if the original alignment specs are documented. Holding a level against the tire indicates a small amount of negative camber, so I'd guess it may already be at .5 to 1 degree. Can't be sure though until I check it with proper tools. Thanks.

 

[Morten]

Hi, on fitting the bodies on my SGTs its a very time consuming job getting all aligned. One fraction out on the front affects everything on the rear, or one tweek on center section makes big change to rear clam location. I reckon you’ve measured everything ten’s of times body in relation to chassis vs suspension etc.
As you have more space on one side I have a feeling a little tweek of body could sort you out instead of altering suspension setup, weights etc, unless everything is bonded in....

Best of luck sorting your fab GT out mate

Morten

 

[Michael]

Morten, you give me way too much credit assuming I've measured everything at this point...

After mulling all of the suggestions, I think my path of least resistance is to first establish the actual camber settings and then decide how much suspension tweaking, with or without additional negative camber, may be required. I'll only consider tweaking the clamshell as a last resort, because as Dirty Harry Callahan famously said, "a man's got to know his limitations."

 

[Bill Kearley]

It's to bad a lot of our cars are not as true as claimed. The top side of my firewall on the passenger side is 5/8 of an inch ahead of the drivers side so when I tried to mount the spider square to it and then the rear clam, it all resulted in a whole bunch of tire outside the LR fender. It was a lot of work to rotate the body on the tub in order to move the rear clam over. The amount I needed was the lesser of two evals. Reworking the fiberglass after the paint was all ready on would have been worse. To pull a lower control arm in by not using the locknut and bottoming out the Heim tight with a thread locker will do no harm.

 

[Howard Jones]

It won't be the best, but you could also delete the lower arm jamnut and bottom out the Heim as well as one of the uppers . the gain may be about 1/2 an inch

NO! NO! NO! the jam nut prevents the rod end threaded shank from wobbling when loaded. The steel RE threaded shaft will wear the aluminum threads in the control arm VERY quickly and ruin them. Bottoming them out will not prevent this.

If that was my car I would trim the wheel opening return (90 degree flange) to about a 1/8 inch on the side in question with a orbital sander and see where you are then. The bodywork will retain its strength as long at there is at least that much. If it works for you then the small sanded area can be touched by hand with a fine work paint brush afterwards.

Rear camber: 1/2 neg is about as much as I would put on a street car. Anymore will wear them out pretty quickly. BUT...……… 1/4 - 3/8 will gain you some clearance and still not hurt the tires much more than a straight up 0 degree camber setting. At least not much. If the tires are not directional then you could just swap sides every 500 miles or so. That way they will wear pretty evenly.