Rear wheel offset problem, looking for help from rx7 gurus !!
 

Hi all,


I'm a new member and apologise if this post is in the wrong area.


ok so I have a 1993 fd rx7 stock rear end other than the following:

​​​coilovers

hardrace trailing arms

Hardrace toe arms

And superpro polyurethane bushes.


I have a problem I can not figure out and its doing my head in.

My rear drivers side ( right hand side ) hub and wheel stick out further out the rear guard compared to the left hand side.

The difference is approx 10-15mm.

It's as if the wheel offsets are different, however they are not.

it seems like the rear cradle has shifted the whole suspension to right. I dont know how this is possible because it has locator studs as well as the bolts, so im lost.


The following things to note

- a couple of years ago, I had a broken PPF replaced, both engine mounts replaced and polyurethane diff bushes installed at the same time. I also changed my aftermarket wheels at the same time. I am not 100% sure if the issue started after doing those things, but I suspect it could have because the car never had the issue before that. ( unless the aftermarket wheels I bought it with had different offsets to make it look straight )

- the car drives very straight

- the chassis is not bent

- the driveshafts are seated properly

- there is no unusual knocks or noises from the rear

- the upper and lower control arms are the same length

- the camber is not the issue because even if i reset the camber to zero on both sides, it is still not straight.

- the rear guards both look the same

- I didn't check the offset of the old wheels because I bought the car with them on the car and now they have been sold.

- the front of the car does not have the same issue.

- the rear subframe does not appear to have any cracks and doesn't look bent from what I can see.


I'm looking for some ideas, solutions and would appreciate your help so much. This issue has been bugging me for so long and I'm at boiling point.


- my thoughts are that possibly the engine mounts, ppf, and diff need to be loosened and re aligned to shift the diff to the left. However I'm not sure if there is adjustment there as the subframe has locator pins and doesn't look like it can be re aligned.


please help

Pull the wheels off, place a straight edge across the back of each wheel, and physically measure the backspacing. Since you're not experience issues while driving the wheel is wrong, the hub is wrong, or there is body damage.

Swap wheels right to left and see if the offset stays the same.

Remove the lateral rear lower control arm and see if the power flex bushing that was installed was an offset bushing that was not installed the same right to left.

Thank you for your fast replies.
The wheels on the car are near new and are exactly the same. I have measured them as well. They are enkei, +15 offset. Both should be approx in line with the edge of the rear guard, however the left side sits inside the guard and the right side sits at least 10mm outside the guard.
The bushes on both the top and lower control arms are normal superpro bushes, none of them are offset. And the bushes do not have a left or right, they are the same for both sides.
iv measured the control arms, they are the same, none are bent.
The hubs look the same, the drive shafts are the same length also.

Is one of your upper control arms installed upside down?

Few ideas for you -

First, take the 1 minute and swap the wheels side to side. Super quick and will rule that out. It's possible one was mislabeled or something. Do the easy stuff, check that off the list first.

Next is gonna be the not fun part - comparing each side to find what is different. The upper Y-shaped arm can be installed upside-down and will do very weird stuff so that's worth verifying. Take a picture of one side then go to the other side and compare.

Finally start measuring things. You can use a string or something simple, doesn't have to be some super precise measurement. This is like one of those "spot the difference in the pictures" - you have to find what is different between the 2 sides.

This is not a common issue, there is something weird going on here. You're gonna have to dig in and find out why. Post pics if you need another set of eyes to check things out.

Dale

Thank you again for your ideas and replies.
I have tried swapping the wheels over and it made no difference.
with the wheels off, you can visually see the hubs are not the same on both sides. One sits further in than the other.
The upper control arms are not install upside down( Iv removed them and checked over, measured etc)

I have also measured the wheel wells and both appear to be the same. Iv measured from imchassis to out edge of the guard, and seems the same.
the only thing I haven't measured is the subframe, I'm trying to leave removing it to last resort.

post pics of those hubs and uprights

https://cimg1.ibsrv.net/gimg/www.rx7...e1175eca5f.jpg
Left hand side - sitting further inside the guard
https://cimg4.ibsrv.net/gimg/www.rx7...b1d491b2d7.jpg
Right side - sitting further towards the outside of the guard

https://cimg5.ibsrv.net/gimg/www.rx7...3dac7d95b7.jpg
Note rear right side wheel compared to the photo of the left.
https://cimg2.ibsrv.net/gimg/www.rx7...49b7407b0e.jpg
Note the rear left hand side, wheel sitting inside the guard. Wheel offset is +38 19inch.
https://cimg7.ibsrv.net/gimg/www.rx7...bcc9e0118c.jpg
Not the right hand side rear sitting almost in line with the rear guard lip. Wheels are 19inch, +38

Get it up on a lift and take *detailed* photos of your subframe and suspension.

Mostly likely you have improperly installed offset bushings, with one side set all the way in, and one side set all the way out.

It's possible your installer didn't know what he was doing. Or Superpro sent the wrong bushings.

Also, make sure the trailing arms are the same length. You might have set them to different lengths and used the toe rods to compensate.

Ok I will take more photos tonight and post them.

But I have checked all the bushes that I have replaced, they are all the same and none are offset.
Plus if they WERE offset or wrong bushes, that could only affect the lower control arm which controls the camber. The upper arm still remains in the same position, meaning the whole hub/wheel CANNOT move.
the only way I can see the whole hub/wheel shifting is if I had adjustable upper control arms and aftermarket lower arms with lots of camber adjustment.
Only other ways are
1 - the subframe shifted/bent ( unlikely )
2 - somehow the subframe, ppf and engine mounts are not aligned properly ( not sure if there is much adjustment in them )
3 - maybe diff bushes are installed wrong or something and the whole diff/subframe has shifted? ( not sure if possible )

I'm stuck for ideas, so your ideas and help is much appreciated.

That is not true. You could offset the entire hub with top and bottom offset bushings. That said, I don't know if Superpro makes offset upper bushings for both the front and rear.

Half an inch offset on one side, half an inch on the other side, and you've shifted the entire suspension by one inch.

Diff bushes aren't going to move the hubs.

It's unlikely that *both* of your subframes (front and rear) are off in the exactly same way.

I am assuming the car hasn't been in a massive accident.

Yes you are right, you can offset the hub with offset rear upper and lower bushes, but none of my superpro bushes are offset, they are standard polyurethane replacements for the oem ones. I have pulled out the arms and double checked again.
the car has NOT been in a major accident either.

and also just to confirm, the front subframe/wheels/hubs are all normal as they should be. No issues at all.

It is ONLY the REAR that has the offset issue.

Nothing stupid like a centering ring stuck on the hub stopping the wheel seating properly? If the suspension "wishbones" are non-adjustable and constrained upper and lower by the subframe, that's dictating wheel position basically.

Diff is suspended off the subframe and won't affect it's position. When making one piece diff bushes several years ago, there is a 5.5mm wide lip on each, needed to replicate the rubber donut on the stock mounts. I suppose in theory (with a dash of incompetence!), they could be installed wrong to shift the diff across, but that would be taken up by plunge in the tripod and CV.

I'd be checking a few pick-up diagonals to verify things are good if nothing stands out. I'm not sure if there's a body repair manual uploaded to the site anywhere? Bookworks - wherever they're located now - would be another option for factory manuals if you light cigars with $100 notes. :D

Unfortunately it's not the hub rings or anything like that because even with the wheels off, you can visually see that the hubs are not the centred the same.
Iv measured both left and right ( as best I could ), the rear guard from chassis to lip, diff centre to hub, and subframe lower control arm mounting point to hub. All appear to be the same or similar.

Maybe its just the angle of that picture but that Quarter panel almost looks like it was pulled out a bit and doesn't look like the factory body lines, the lighting makes it hard to see

Yep. It looks like the car has been wrecked to me

stone guard is missing, so its at least been repainted. also front end doesn't match the rest of the car

i'd start measuring like Billy boy says, manual is here https://foxed.ca/rx7manual/manuals/F...p%20manual.pdf

Fender lip to inner wheel well measurements on both sides, as well as hub flange to inner wheel well. Should tell the story.

I had the car resprayed many years ago but it definitely hasn't been hit. The rear quarters have not been repaired other than a couple of small trolley dings.
it is probably the lighting of the photos that makes it look that way. I will take more photos.
I have measured the wheel well to lip, and both sides are the same.

Is there any adjustment in the engine mounts?

I know there is a bit of adjustment in the PPF from the transmission side.

Is there any adjustment in the sub frame?

That's not just a little off, it looks like INCHES different. It would be hard to repair an accident and have it look even semi normal with it that far off. I'm better on something mis-installed.

However—is it just an illusion, or is the front wheel tucked in more on the left than the right as well? That may be an illusion, but the rear definitely isn't.

Fixed by 4 or 5 fasteners each side and locating dowels - you're not going to find adjustment there.

Engine mounts or PPF, will again have no bearing on what happens at the wheels, that's clutching at straws I'd say. Longshot, the aluminium uprights have been known to be damaged by hamfisted mechanics pressing bearings and I guess bad kerbing could damage something too, but would think damage there would be fairly obvious to the naked eye.

Post pics of the actual hubs and suspension. Facing the wheel well.

The front is definitely not off. so must just be the angle or lighting of the photos.

I will take more photos and post them up.

I have also removed and measured the top and bottom control arms on both sides to compare. There is no issue there. Both L and R are the same.

I can't see it bieng anything other than a twisted/bent subframe. But visually from underneath the car looking at the subframe i cant see any kinks, twists or signs of damage.

https://cimg4.ibsrv.net/gimg/www.rx7...0bc640df29.jpg
Right side
https://cimg6.ibsrv.net/gimg/www.rx7...69c8104420.jpg
https://cimg5.ibsrv.net/gimg/www.rx7...5f47f48af5.jpg
Right side
https://cimg7.ibsrv.net/gimg/www.rx7...bbb60ab444.jpg
Left side
https://cimg8.ibsrv.net/gimg/www.rx7...7c89a3318b.jpg
Ppf
https://cimg9.ibsrv.net/gimg/www.rx7...9093674b1d.jpg
Diff/subframe

Subframe
https://cimg2.ibsrv.net/gimg/www.rx7...5e55959776.jpg
Subframe locating pins
https://cimg3.ibsrv.net/gimg/www.rx7...c551fecf49.jpg
Diff/subframe
https://cimg5.ibsrv.net/gimg/www.rx7...18beef9114.jpg
Diff/subframe
https://cimg7.ibsrv.net/gimg/www.rx7...d807afcc2b.jpg
Left side
https://cimg8.ibsrv.net/gimg/www.rx7...96bdc65654.jpg
Right side
https://cimg9.ibsrv.net/gimg/www.rx7...e3fa0748ca.jpg
Diff/subframe

The car has had a subframe change at some stage at least.

Maybe a straightforward upgrade, rather than accident damage. I'd go through that link j9fd3s has kindly provided and check datum points if there's no conspicuous anomalies.

Edit: That last pic of the lower LHS suspension pick-up looks weird - camera angles possibly though.

The camber bolts are pointing in slightly different directions, but I'm sure that's a non-issue.

Maybe use a plumb line to mark spots on the floor to see how far the hubs and fenders are from centerline of the car?

The car needs to be perfectly level, though.

The car has had the subframe changed, to the later model subframe with bracing etc.
it is possible that it wasn't straight when I bought it? I bought it from a wreckers but it looked straight and there's no visual damage.

in regards to measuring the car perfectly, it's very hard to find the exact centre line of the car and to get it on exactly level ground.

I'm still leaning towards the subframe bieng the issue, but i need to pull it out and compare it side by side with another one.

I have read the body manual that was posted here, thank you very much. It gives me a few other ideas on measuring etc.

Pictures with everything blown apart don’t help. Take the wheels off and take fresh pictures.

to me, the quarter panel still doesn’t look correct. It’s almost like you’ve got a molded widebody on one side or a cut was put on top of damage underneath. Talk a picture of the inside of the fuel fill area too.

That upper Y-shaped aluminum arm that the bottom of the coilover is bolted to is upside down. There is a Mazda logo cast into it, it should be readable when it's installed.

That may not be the whole problem but that's a lot of it for sure. That will really jack up the rear end alignment.

Dale

i notice that too. the alignment will affect (effect?) where the wheel sits, and the bigger the wheel the more you'd notice

Dale is correct. Look at the diagram below. It clearly shows the correct positioning of the upper arm. The end of the arm where the pillow ball sits should be pointing upwards, not down.


https://cimg2.ibsrv.net/gimg/www.rx7...14a345c62.jpeg

lmfao, this whole time I was thinking "are the upper arms upside down?" but I was too lazy to check if I was right and didn't want to say anything in case I was wrong.

I thought it might be an indicator that something was off, but I don't actually know off the top of my head how much a full swing of the bolt changes the camber.
I don't/can't do alignments on my own car.

UPDATE
thank you Dale and others for the resources and your thoughts.

the upper control arms are installed correctly now, and unfortunately it didn't resolve my offset issue.

I pulled all the rear arms off, unbolted the PPF, subframe etc.
I tried to adjust the PPF and the subframe however it only gave me a couple of mm adjustment at most due to the subframe locator pins.

I haven't finished putting the wheels on and dropping the car on the floor etc, but I can still see that the hubs STILL don't sit equal inside the wheel arch.
So I imagine once the wheels are on and car is on the ground, it will be the same.

I am lost again and don't know where to go from here. I have tried to measure using the body manual attached above and everything seems normal.

I can only put it down to a bent subframe which is forcing the right side arms outwards and the left hand side arms inwards.

thoughts please..

Subframe sounds like the most likely culprit right now. I've bent many Miata subframes in my racing career. :)
Try getting a measurement between the alignment bolts. Maybe someone here can do the same measurements on their car to compare.

Now that I'm looking at this on a PC you can see as clear as day that this car has been wrecked before. Your whole driver's side quarter panel is body filler from the front of the arch and over around to the fuel filler door. It's all wavy and none of the spot welds are visible because the detents have all been filled with body filler.

Agreed, looks like from that picture that the fuel filler door doesn't even line up. I'm guessing they may have pulled out that whole side too far with whatever happened causing the overage.

That entire quarter panel (to half way up the roof pillar) is still available from Mazda.One way to fix that is get a new one and have it cut/welded and smoothed in.

I did mention before that the car has been resprayed about 15 years ago. The rear guard was NOT smashed, only had a minor ding.
the fuel door does line up however my latch and spring are broken so it looks like it doesnt.
I dont see how the rear guard is the problem because it doesn't explain why the right hand side has shifted outwards.

Does anybody have measurements for the subframe that they would like to share?

Did you see the car the subframe came out of originally - or was it just something that came off the wrecker's dexion? Unfortunate that there appears to be no measurements in the manual, there is a subframe here, but not sure if I'm likely to be over where it is any time soon.....and its modified for camber on the lower pick- ups.

If you can find fixed points on say the upper subframe, and shim your jack stands or whatever you're using level with plumb bobs (or use diagonals) you should be able to derive the centreline to scribe and measure the lower pick-ups at least. Of course the other least favourable way is just to buy another - all come out of rollers, so should be good......

Edit: appears the facebook link is no good, FDRX7 parts, James in Newcastle. He indicates he has a few.

Thanks Billyboy.
I did not see the car that the subframe came out of but it was from a wreckers so im assuming it was out of a smashed car.
it's hard to measure the subframe without something to compare to.
I think I might have to either replace the subframe and hope that it fixes the issue, or take it to a body alignment shop and have them laser measure the chassis/suspension etc. I just can't justify selling a kidney to pay for it
James Pearson does have lots of parts, he seems like a decent guy.

I believe that you're in denial OP, it appears that when it was repaired it was pulled out too far along the arch. If the subframe was bent you'd have alignment issues and the car would be walking all over the road. All of the suspension components line up and your struts bolt up correctly, if the suspension was too far in it would be angled going up into the pocket where it bolts in.

You're chasing an easy problem the hard way, have the car inspected and measured by an auto body shop.

This.

He needs to take a large framing square and measure the distance between a flat part of the unibody (e.g. the spot on either side of the shock) and the widest part of the fender lip.

That, or just have the other fender pulled out a bit more and call it a day.

Thanks Molotovman but you are wrong about the guard. I can confirm this because I measured the other guard and made a cardboard template following the curve from the hatch edge to the guard lip.
I then compared it to my other guard ( problem side ) and it matched. It was max 1-2mm difference which could just be because the template was made by hand.
I then compared this to my friends low kms, stock s8 fd and his guards match my template.
I have also measured my guards inside the wheel well and both are the same measurement.

That rules out the guards bieng the issue.
It might be the angle or lighting in the photos that make it look like they arent straight.

The hubs are out at least 10mm out from each other which I think has to be either the subframe or a part of the rear suspension.

Is it possible for the trailing arm adjustment ( castor ) or camber adjustment or coilover adjustment to cause my issue?

Thanks Molotovman but you are wrong about the guard. I can confirm this because I measured the other guard and made a cardboard template following the curve from the hatch edge to the guard lip.
I then compared it to my other guard ( problem side ) and it matched. It was max 1-2mm difference which could just be because the template was made by hand.
I then compared this to my friends low kms, stock s8 fd and his guards match my template.
I have also measured my guards inside the wheel well and both are the same measurement.

That rules out the guards bieng the issue.
It might be the angle or lighting in the photos that make it look like they arent straight.

The hubs are out at least 10mm out from each other which I think has to be either the subframe or a part of the rear suspension.

Is it possible for the trailing arm adjustment ( castor ) or camber adjustment or coilover adjustment to cause my issue?

sort of, if you change the angle of the wheel, it changes where the lip will sit. the effect will be bigger the bigger wheel too.
for example if you have more negative camber the top of the tire will move inwards, which people use to tuck under the fender lip

Billyboy suggested finding the center of the car, and then you can measure the distance to the suspension pivot points on the subframe and see if they are symmetrical, if not then subframe is bent
https://cimg7.ibsrv.net/gimg/www.rx7...866eee1b97.jpg

^That pic is what you want to measure

On the diagonals may be easier, if you can clear the chassis mounts and any protrusions, without having to worry about going back and forth levelling - may need to drop the ARB and the fuel tank gravel shield to get best access. Basically following this X in the subframe brace, RH rear top to LH bottom mount and vice-versa - hopefully discover if there's any discrepancy.

Can't remember if the bolts are 12mm now? Threaded rod with a couple of nuts to adjust height and either sharpened to a point on the lathe, or spun up in a drill against a bench grinder would be best for an accurate measurement. You can probably eyeball it sufficiently without going to that extra trouble though. I seem to recall the two upper mounts are planar, but that's definitely not the case in the front.......you should be able to work something out to compare sides using some Greek guys ancient theorem if they aren't though. :D

I'd imagine putting it on a car-o-liner or similar nowadays would cost way more than the $350 for the subframe, then again, you want to be sure you're not pissing money away replacing parts and still be in the same boat.

https://i.imgur.com/BtI4Wm6.jpeg