Higher Speed Instability

[n1cecupoftea]

Hi. Firstly, this is a great forum that has already been extremely useful to me.

I bought a 2006 MR2 roughly five months ago.

I have noticed that at low to medium speeds it feels stable but at higher speeds it feels unstable and I have had a couple of moments of oversteer as a result, when I wasn't even pushing hard. traction seems to be excellent, way better than my other car, which is understandable because it is front engined and front wheel drive. I am trying to find out if this higher speed instability is normal or if I have a problem and would really appreciate any help/advice anyone can offer.

Not sure if the additional information below is helpful. Sorry in advance for the waffling.

When I purchased the car it had Toyo Proxes T1R 185/55/15V's on the front, which are still on it now. On the rear there was two different cheap tyres that I decided to get rid of straight away. I think the recommendation is to stick with one brand/type of tyre on all four wheels but I couldn't find any Toyo's that had the required W speed rating. V rated tyres should be more than adequate but wasn't sure if not adhering to the manufacturers recommended speed rating would potentially invalidate my insurance. With this in mind I now have Bridgestone RE040 215/45/16W's on the rear.

I have done around 3500 miles so far and started with Toyota's recommended tyre pressures. I am now running 2 PSI above the recommended pressure in the fronts because as I understand it the Toyo's have soft side walls. The rears are still running at the OEM pressure level.

I went on a 160 mile drive at the weekend and at the end checked the temperatures of the rear tyres. The outside of both was cool but the inside of both was warm. This was just checking by touch only but there was an obvious noticeable difference. The only thing I can think of that would cause this is too much negative camber but I don't think the camber on the rear is adjustable.

It is only a weekend toy so I drive it fairly enthusiastically but not hard because I am still getting used to having a mid-engined car and don't want to end up in a field or a ditch.

The rear tyres are wearing evenly, the inside is definitely not wearing faster than the middle or outside.

Does all the above suggest that I have something not quite right or bent at the rear of the car or is there an alternative simple explanation for this?

Thanks in advance for your help. Sorry for the wall of text. I wanted to provide all the information I have.

[1979scotte]

I would be looking to get a full 4 wheel laser alignment done.
Are your shocks and springs in good condition?
What is the state of the rear cross member?
If nothing wrong with the above then I would blame the tyres.
Toyos soft sidewalls may not play nicely with another brand.
I have had Toyos on a previous 2 and was very happy.
Until I tried  Yokohama AD08R and realized what I was missing.

[n1cecupoftea]

Thanks very much for your reply.

The 4 wheel laser alignment sounds like a good plan to me. I am in North Cambridgeshire. Does anyone know of a garage they would recommend in the area for this?

The shocks and springs look to be in good condition. The rubber dust protectors on the shocks have fallen to pieces but I think this is relatively normal.

I will readily admit that I have almost zero technical skills/knowledge. Is the rear cross member the thing shown in the image linked below? If it is then I have checked this and it only has mild surface rush on it.

 m https://uploads.tapatalk-cdn.com/201701 ... 2482a8.jpg m

I will definitely do with the Yokohama AD08R next, thanks for the recommendation. If they are good enough for Lotus to put on the new £60k Elise 250 Cup then they are good enough for an MR2. Just a little reluctant to change the tyres when they have only done 3.5k miles. I know changing the tyres is cheaper and safer then going backwards into a field.

[Topdownman]

Yes, thats the rear subframe.

What mileage has it done and when is the next mot due?

These cars really do like fresh suspension, even late low mileage models. If the mot is due soon they may pick up on any worn bushes or wheel bearing problems which could also cause problems.

Ardent swears by wheels in motion for alignment but pricy and you may want to check everything else is ok first?

[n1cecupoftea]

Thanks again for the reply chaps, appreciated.

It has done 66k miles and the next MoT is due in May. There were no advisories on the last MoT but I realise that doesn't mean much.

I am not sure if I should wait until the MoT or go get the alignment checked out first.

There seems to be a Wheels in Motion in St. Neots and one in Chesham, please see below. I am guessing it is the Chesham one.

 m http://wheelsinmotion-stneots.co.uk/ m
 m http://www.wheels-inmotion.co.uk/contact-blackboots.php m

[Bossworld]

When you mention minor surface rust on the subframe, is that from looking through the engine bay or underneath the car (you'll need to remove the 'nappy' under the car for a proper look)?

[JoeCool]

Don't spend money if you don't need to. You tyres won't be doing this, you can get some more life out of them yet. At least use them thorough winter!

First: Check sub frame condition properly. Get underneath it, with the car on a lift, and remove the plastic undertrays, and have a very good look at the underside of the sub frame. That said, if it was bad enough to cause instability, it would almost certainly have killed you already. But it's first thing to check on any MR2 Roadster.

Then: Alignment, all day and all night. Get it set up by someone decent. I've leave someone closer to you to make recommendations. It may well be that that alone cures it. These cars are very sensitive to proper alignment, and because they're light and have low polar inertia, they whip around quick!

I use the Wheels in motion in Chesham and they're brilliant, but it's a big drive for you. 'Blackboots wheels in motion'  they are. THe St NEotts one appears to be unconnected.

[n1cecupoftea]

When you mention minor surface rust on the subframe, is that from looking through the engine bay or underneath the car (you'll need to remove the 'nappy' under the car for a proper look)?

First: Check sub frame condition properly. Get underneath it, with the car on a lift, and remove the plastic undertrays, and have a very good look at the underside of the sub frame. That said, if it was bad enough to cause instability, it would almost certainly have killed you already. But it's first thing to check on any MR2 Roadster.

I have looked through the engine bay but also had the car up on ramps and taken off the 'nappy'. It looks better than I expected considering it is 11 years old although it isn't by any means perfect.

[n1cecupoftea]

Don't spend money if you don't need to. You tyres won't be doing this, you can get some more life out of them yet. At least use them thorough winter!

Then: Alignment, all day and all night. Get it set up by someone decent. I've leave someone closer to you to make recommendations. It may well be that that alone cures it. These cars are very sensitive to proper alignment, and because they're light and have low polar inertia, they whip around quick!

I use the Wheels in motion in Chesham and they're brilliant, but it's a big drive for you. 'Blackboots wheels in motion'  they are. THe St NEotts one appears to be unconnected.

I agree, I definitely have to get a few thousand more miles out of the tyres.

I will get the alignment done soon. I think it is worth it for peace of mind alone. Chesham is a fair way but it is a good excuse to drive the car  s:D s:D

[Ardent]

Hello and welcome

I echo what joecool said.
160 mile round trip for me to w in motion.
Worth it.

[Bossworld]

When you mention minor surface rust on the subframe, is that from looking through the engine bay or underneath the car (you'll need to remove the 'nappy' under the car for a proper look)?

First: Check sub frame condition properly. Get underneath it, with the car on a lift, and remove the plastic undertrays, and have a very good look at the underside of the sub frame. That said, if it was bad enough to cause instability, it would almost certainly have killed you already. But it's first thing to check on any MR2 Roadster.

I have looked through the engine bay but also had the car up on ramps and taken off the 'nappy'. It looks better than I expected considering it is 11 years old although it isn't by any means perfect.

Fair enough and good on you for being thorough.

Mine ('04) used to wander badly when I first got it but the subframe was shot.  I had a brand new one fitted, followed by a full wheel alignment at Demon Tweeks.  That did the trick for me.  It's still affected by crosswinds at motorway speeds but certainly feels more stable than it did.