MR2 Swaying side to side

[Jabeo]

Hey all, long time no post! Have been having a bit of a problem recently with the 2 in which the car isnt tracking straight and feels like it (the rear end?) has a tendency to sway from side to side at speeds from 80kph+ on the expressway.

What happened was i took the car to get the 2 rear tyres replaced, to another pair of 235/40/17s which is what i was running. Car drove to the shop in Auckland perfectly fine and drove straight as can be with no issues. Immediately after getting the car back and taking it on the motorway the car began to feel extremely sensitive and twitchy, and it felt like the car was on ice at times, pulling to one side, and then with a correction, gets worse in the other direction, so on and so forth. This is especially evident when changing lanes, in which it feels like the car is unpredicatable and wont go in the direction i want it to due to its swaying.

I have since got the car an alignment in which they fixed some of the toe on the back to hopefully get it to track straighter, but that did nothing at all really. I have also dropped the tyre pressures in the rear a bit, in the hopes that maybe the car would settle a bit and have a bigger contact patch to the road but no luck. Moving the rear wheels 9-3 and 12-6 shows little to no play side to side and All suspension is torqued to spec and nothing is loose, only thing i can think it might be is the suspension bushings maybe? Rear tie rod bushes possibly? I have a full kit but not the ones for these. Does anyone have any ideas for anything else i can check?

I just find it really strange that the only change made to the car between it driving fine and then it not, was getting some new tyres fitted to the rear. It has made driving to and from auckland really uncomfortable and feels quite dangerous at times.

[mknz]

Dumb question, are the wheels actually torqued on correctly? I can't imagine what else they would have changed. Balancing wise tends to be purely vertical movement and doesn't match the twitchy symptoms. Direction doesn't matter since it's purely to move water. Symmetry could make a difference depending on the tyre, but doesn't really explain twitchy.

I'm assuming they didn't touch the suspension setup since they shouldn't have.

[Benckj]

Having been through something similar with mine many years ago I would be looking at your alignment results and comparing to what the autocross guys run. I do not think the factory specs are good enough which is what most alignment Technicians adjust to. It is also advisable to speak with the Tech to actually find out how competent they are. Often they stick some pimply face kid on the machine who doesn't have the correct experience to set-up suspension. Common fault is not getting enough negative camber on the front end without installing 'Crash Bolts'.

https://midshiprunabout.org/mk2/crash-bolt-install/

[GDII]

What are your new tyres? What tread depth do they have vs the old ones?

When I got new Toyo T1R on the 15" wheels I had they would feel real sketchy for at least 1000km while they cleared the surface material but also the tread depth is like 10mm so the tread blocks allow the car to 'float' around on them a bit. Once it was worn in it would feel far more planted. However I never had this issue with my RE003 but they are not the same tyre and on a different wheel size so that explains some of it.

[Jabeo]

Dumb question, are the wheels actually torqued on correctly? I can't imagine what else they would have changed. Balancing wise tends to be purely vertical movement and doesn't match the twitchy symptoms.

Having been through something similar with mine many years ago I would be looking at your alignment results and comparing to what the autocross guys run. I do not think the factory specs are good enough which is what most alignment Technicians adjust to. Common fault is not getting enough negative camber on the front end without installing 'Crash Bolts'.

The Passenger rear wheel was done up extremely tight and the drivers rear not so much. i ended up removing both wheels, and chucking on a spare set of wheel nuts and made sure all of them were torqued even to spec with a torque wrench. According to the alignment guy he was doing it to oem specs and looking at the sheet it looks like he left the car at 2 degrees camber up front and rear and adjusted the toe in the rear to help it track a bit straighter, this also fixed some camber in the back too. sitting at about 2.5mm toe in on each side of the rear. I do have a set of 4 (12mm?) oem crash bolts sitting in a bag that havent been installed yet as well.

What are your new tyres? What tread depth do they have vs the old ones?

When I got new Toyo T1R on the 15" wheels I had they would feel real sketchy for at least 1000km while they cleared the surface material but also the tread depth is like 10mm so the tread blocks allow the car to 'float' around on them a bit. Once it was worn in it would feel far more planted. However I never had this issue with my RE003 but they are not the same tyre and on a different wheel size so that explains some of it.

I ended up going for a pair of ns20s purely cause i have heard mostly good things about them, they came in the profile and size i wanted and werent going to tear my wallet to pieces, as this is a mostly street driven car I have the spare set of BBS wheels that will be getting rebuilt so i would like to run a bigger tyre on that - so forking out massive coin for a pair of tyres now didnt make a lot of sense to me. The current tread depth on them is about 8mm, and the alignment guy also reckons that they should track a bit better after ive done a few kms on them. ive done a few trips to auckland and back since but not a great deal of improvement. is that a large tread block?

[GDII]

8mm is about normal but it also depends on the pattern. The NS20s are nothing special but that means they shouldn't really do what you are feeling. Maybe swap out the rear wheels for a test set, maybe from a mate or something if you don't have another set to rule out the tyre.

[mknz]

Yeah, to be honest, I have no idea what changed. I had a pair of NS20s when I got the SW and didn't have this issue.

Did they do an alignment with the new tyres before you drove it? I can only imagine that either a setting is way off or something's up with the rear tie rods. If they aligned the front then maybe the same up front.

[Benckj]

I’d install the Crash bolts to get negative camber. Not sure what size you have but possibly use one on each corner to get -2deg or may have to use the four on front only. I’ll see if I can locate my autocross alignment specs as it made the car handle very well regardless of tyre type/brand.

[GDII]

I found those autocross specs terrible. Under braking the car wants to go anywhere but where you point it.

[tw2]

I have never had issues with stock alignment specs. Handles perfectly. I would check the rear trailing arm bushes and lower ball joints.

Otherwise greasy crap all tires are covered in as mentioned already. Maybe old tires? What is the manufacturer date code? I have refused new tires before as they were sitting around for too long and these aren't the most common sizes.

[4CylinderSpecial]

Def double check the alignment specs, although I had a similar issue with my old G-LTD and it was the tyres. It made the car not feel planted at all and almost like the rear wanted to step out a fair bit. There was a spot coming down from the Harbour Bridge where I would change lanes and I would almost feel like the car would be on the edge of a slide (at 80). Being that you have the earlier toe arms etc (from memory), you might want to get even more toe added as possibly you don't have enough.

Echoing Phil in that you should avoid autocross specs as it makes the car very prone to wondering and tramlining! We both had this issue, esp under braking which is when you'd want the most stability. I found my favourite specs to be with a small amount of toe out in the front and max camber all around.

[GDII]

Def double check the alignment specs, although I had a similar issue with my old G-LTD and it was the tyres. It made the car not feel planted at all and almost like the rear wanted to step out a fair bit. There was a spot coming down from the Harbour Bridge where I would change lanes and I would almost feel like the car would be on the edge of a slide (at 80). Being that you have the earlier toe arms etc (from memory), you might want to get even more toe added as possibly you don't have enough.

Echoing Phil in that you should avoid autocross specs as it makes the car very prone to wondering and tramlining! We both had this issue, esp under braking which is when you'd want the most stability. I found my favourite specs to be with a small amount of toe out in the front and max camber all around.

This is a 92 so has the later suspension but still, they are an MR2 afterall.
I drove a REV4 but wasn't going much faster than 80 for the short test drive but I could feel the tyres in the rear floating around a bit. They were rather high profile 16s though. Nothing that made the car feel unstable but you could feel it when pushing hard in the corners vs the RE003 with stiff sidewalls. I still have my 15" T1R and 4s in the rear and they are a bit floaty but nothing scary, just a bit slow to react to driver input.

[Benckj]

I found those autocross specs terrible. Under braking the car wants to go anywhere but where you point it.

I'll need to drag out the specs used to make sure we are singing from same song sheet. I seem to recall going over the specs with two alignment Technicians at different times and they agreed it would be the best settings for road/track use. Both Technicians had experience working on rally suspension cars worth mega bucks. I've never had an issue with the drivability during all sorts of conditions (dry, wet, mud, snow & ice) using a multitude of tyres.

Specs used;

91-92 version
FRONT
Camber -2.5 or greater
Caster 5.0 deg
Toe 0.3 deg OUT
REAR
Camber -1.5
Toe 0.3 deg IN

93+ version
FRONT
Camber -2.5 or greater
Caster not adjustable
Toe 0.3 deg OUT
REAR
Camber -1.5deg
Toe 0.15 deg IN

[GDII]

Yip. Same specs. Was not a fan.

[Benckj]

Yip. Same specs. Was not a fan.

Might be a good idea to display the specs everyone runs with as I believe the factory ones state positive camber. Running with the negative -2.5deg was one of the biggest improvements I found with mine. Crash bolts were not enough as needed high tensile camber bolts to get more deflection.