Decision time

[dave]

Hi Gareth.
You really need to go for bigger wheels and lower profile tyres. Or possibly Run flats if they are available in your sizes.
Do you have any form of anti roll bar stiffness on the car, that will make a massive difference.
Also, for high speed stability some flippers under the front corners, but I don't thing they will be as effective on a Sumo compared to other makes due to the engine location.

[gareth08]

Thanks guys.

I really don't want to have to change wheels as it's to expensive and I really like the wheels I have. To get 16 or 17 " rims with the corect offset they are gonna have to be split rims which are going to be 2 grand with tyres I suspect.

Thats why I was looking at changing the rubber instead. Ending up with a slightly smaller rolling radius is not a real issue (I can recalibrate the speedo from inside the car easily enough) and I can always lower the car a tad to compensate for looks.

Im probably not going to own the car for much longer as I'm looking to buy something different for my birthday that will tie in nicely hence the reason I'm reluctant to shell out on new rims as well.

Surely running Toyos must/should improve it.????

[Clarkson]

Originally Posted by gareth08

Thanks guys.

I really don't want to have to change wheels as it's to expensive and I really like the wheels I have. To get 16 or 17 " rims with the corect offset they are gonna have to be split rims which are going to be 2 grand with tyres I suspect.

Thats why I was looking at changing the rubber instead. Ending up with a slightly smaller rolling radius is not a real issue (I can recalibrate the speedo from inside the car easily enough) and I can always lower the car a tad to compensate for looks.

Im probably not going to own the car for much longer as I'm looking to buy something different for my birthday that will tie in nicely hence the reason I'm reluctant to shell out on new rims as well.

Surely running Toyos must/should improve it.????

You might aswell leave it alone then.

[wilf]

Something can't be right here - from Gareth's descirption, the thing is virtually undriveable above 100mph. That is just not right.

Now my old (MKII) Sumo on 15" rims with BFGs could struggle up to 125mph, but whilst it wasn't a paragon of stability, it certainly was not bad once I had the shocks etc. sorted.

The Crendon is absolutely rock solid way above that, on 16" rims. There is only 1/2" difference in tyre sidewall height, not significant IMHO.

I feel there is something else going on here apart from just tyres. Gareth - have you tried "raking" the stance of the car - i.e. get the rear ride height about 1" higher than the front? It can often help.

[gareth08]

Originally Posted by wilf

Something can't be right here - from Gareth's descirption, the thing is virtually undriveable above 100mph. That is just not right.

Now my old (MKII) Sumo on 15" rims with BFGs could struggle up to 125mph, but whilst it wasn't a paragon of stability, it certainly was not bad once I had the shocks etc. sorted.

The Crendon is absolutely rock solid way above that, on 16" rims. There is only 1/2" difference in tyre sidewall height, not significant IMHO.

I feel there is something else going on here apart from just tyres. Gareth - have you tried "raking" the stance of the car - i.e. get the rear ride height about 1" higher than the front? It can often help.

Hi Wilf,

This is the akward bit as at say cruising at 120+ its ok in a straight line but its as soon as you start taking a reasonable bend that it starts going pear shaped also it appears the same thing is happening under very hard acceleration with the rear squatting and the back feeling like its all over the place and the opposite happening under hard deceleration gear changing.

The car currently sits about 1 1/2" lower at the front. I have wound the damp and rebound right up front and rear to try to stop the see saw effect but it doesn't seem to have helped much.

Any other ideas ?????

[wilf]

Sounds like rear toe-in is varying under power/deceleration?

[stevee8]

Gareth, the 2" side movement stationary suggests it's not a dynamic problem.
Have you tried the same test with the tyres pumped right up, say 35psi?
This should significantly reduce side wall flex and might give you a clue as to whether it's a tyre issue. Failing that I assume you have checked bushes and mountings etc which might induce that kind of movement?

[FatBoy]

Would Goodyear "Billboards" fit?
But I'm inclined to agree with Wilf, it sounds like more than a simple tyre issue to me too.

Paul

[Clarkson]

Why don't you swap your wheels with a local member,that will rule that one out??

[Noel]

Originally Posted by dave

Hi Gareth.
You really need to go for bigger wheels and lower profile tyres. Or possibly Run flats if they are available in your sizes.
Do you have any form of anti roll bar stiffness on the car, that will make a massive difference.
Also, for high speed stability some flippers under the front corners, but I don't thing they will be as effective on a Sumo compared to other makes due to the engine location.

Don't talk to me about "run flats"

Got some excessive wear on outside edges of mine, went down to tyre place and they inform me that is usual for run flats and I am doing well to have done 14K on them with a 3 series. They have excessively stiff side walls (which could solve Gareth's problem) and give a very hard ride with less grip than ordinary tyres. If I had a 5 series I would be lucky to see 10K. On the plus side they have come down to £130 each. So that's alright then