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[Osaze]

Earlier this week I was driving somewhere to stay overnight and I was pacing along a rural national speed limit type road (60mph+) when I had to correct a bit of a twitch on a fast left-hander which is unusual as I drive that stretch a lot. Later I tried to provoke things on a roundabout to see if something was amiss but it seemed as grippy as usual.

Next day I get out and see I've got a completely flat right rear tyre. Put the spare on and drove down to tyre place. Had a slight oversteer twitch moment when steering right on a roundabout. Put it down to slightly damp road surface at the time, but still unusual.

Had to buy a brand new right rear tyre (Nankang replacing a Goodyear). Driving it back I took a medium sized roundabout the usual way, carrying a reasonable amount of speed into it. Just past the apex, where the loading is probably the most, the back end stepped out big time. I had to do my best Sebastian Loeb to catch it and not spin. (No-one was around to see it ! It must've looked great!) In my fright I had to pull up somewhere with the hazards and check the wheels/tyres. Visually ok, got home and checked them all; front pressures fine at 30psi, left rear 32, new right rear 30. Corrected the rears to 33 and went out to see if this would happen again. I was a bit scared, but when I had the bottle to carry some good speed into a roundabout I had the same problem. Driving in slower and feeding in the power was no problem.

I was worried so I'm borrowing another car at the moment. Could it be the tracking? Or something more wallet-emptying, like new bushes or dampers?
 
'96 2.0 CDX Estate

[vauxfan2k]

cant see half your text cos of the HUGE avatar m8,  

[Osaze]

Yeah, that was bizarre! Changed it now (the avatar that is).

[Jimbob]

Its things like this that ensure I always have matched tyres per axle.

[jjleonard]

I'm thinking it might be your front wishbone bushes, or maybe the steering idler? Others will have other opinions, but I had a very similar moment on an approach to a motorway slip road off a roundabout.

At the highest point of loading the back stepped out dramatically and like you I had to wind on a ton of opposite lock to control it. Scared the bejesus out of me.

A later visit to WIM showed my front wishbone bushes (and steering idler) to be knackered. Tony showed me just how much the front wheels can independently vary in steering angle when the bushes are loaded - it looked like up to five degrees!

I've since tested the theory (haven't changed the bushes yet) - if I enter a corner and turn in hard, I can feel the bushes causing the steering to wriggle, once it felt like the wheels were digging in, and sure enough, around came the back end again.

Don't know if that's any use, but i'll be following this thread with interest!

[TECHNOPUG]

Well firstly you had a flat tyre. Secondly, you then fitted a different make of tyre on the same axle and the tyre is brand new. It takes several hundred miles of driving to scrub a new tyre in so that it works properly. You'll have very little grip pushing on with a brand new tyre.

[GmasterT]

Nankangs are gash compare to the goodys, that will contribute, possibley knakered rear shocks or bushes that is upsetting the initial balance, or the fact that its slippy season and the roads are slippy    

 

[HerefordElite]

mixed tyre age and make across an axle is a big big no no  

end of

[Osaze]

Hmmm, I guess the tyre mismatch is a possibility. However, the new tyre is the right rear, and as the problem seems to be in right-handers that means the Goodyear left rear is the one being loaded the most.

I won't have the chance to get it looked at before Sat.

[vauxfan2k]

oversteer will be caused by worn donut bushes in the rear, the rear wil feel like its sliding out but its the body moving on the rear suspension thats causing the feeling.

Had this on my carlton and 2 of my omega's. once sorted you could hook it round a corner and it stuck as good as the tyres wwould let it.

[Marks DTM Calib]

Goodyear one side....Nankang ditch finder the other...

I assume the ditch finder tyre size is the correct one and its fitted to the correct orientation?

Obvious.....and you will have to go some to get the inner wheel off the ground so it will always be contributing to keeping the car straight...

[al brown]

I agree, both rear tyres are gripping the road but a new tyre will have little grip for the first few days. You may have other problems, but I would be carefully chucking such a big car about on any new tyre.

[Entwood]

Have a read about the molasses/gritting issue ....  I wonder if this is a possibility ??

http://www.omegaowners.com/forum/YaBB.pl?num=1232048936

[ngrainqey]

iv driven about with odd tyres from one side on the rear axle to the other before and it drove no differently and hung on rather well

[Osaze]

It was a good job I wasn't on a corner with a brick wall on the exit...

Are there any other symptoms of worn bushes, or dampers, when not near the limit? Like noise over bumps?

Someone also suggested swapping the tyres around, maybe put the new Nachoking front-left and see what happens, to eliminate the possibility of this being the cause.