High speed handling
Discussion
Pushed hard for the first time yesterday (for those that Know it the A331 westbound) was taking a sweeping lefthander and the back end started a cycling shimmy. Most disconcerting and not what I would have expected. Is this normal or does the car need to go on a ramp. (too old to crawl underneath)
Edited by crisisjez on Tuesday 10th April 19:09
Sounds like a bushing or alignment problem.
Although tyre choice and pressures will come into it.
When the rear end is as it should be and with the stock 235 section tyres they are fine even at 130mph. Though don't try lifting off mid-corner; not enough rubber on the road.
With 255 or 265 section rears they feel much more planted.
Although tyre choice and pressures will come into it.
When the rear end is as it should be and with the stock 235 section tyres they are fine even at 130mph. Though don't try lifting off mid-corner; not enough rubber on the road.
With 255 or 265 section rears they feel much more planted.
To be honest, I have had similar problems. My tyres have definitely seen better days though so I will slap some new ones on this week. Sorry to hijack the thread slightly but it would seem that a 255 is definitely the way to go at the back but what about the front. Maybe going to a 245 is the way forward as it would provide a little more grip but in my experience the front end of the car isn't the problem. I don't want to compromise the turn-in by giving the front too much grip.
any thoughts?
any thoughts?
GTS 029 said:
To be honest, I have had similar problems. My tyres have definitely seen better days though so I will slap some new ones on this week. Sorry to hijack the thread slightly but it would seem that a 255 is definitely the way to go at the back but what about the front. Maybe going to a 245 is the way forward as it would provide a little more grip but in my experience the front end of the car isn't the problem. I don't want to compromise the turn-in by giving the front too much grip.
any thoughts?
any thoughts?
Different strokes maybe,
All my problems are with the front end. Understeer and more understeer. The stock (post 2002) rear end is fine imo, on wider rubber (265).
Fitting a complete bush kit at the front (Super-Pro from Oz) has improved the feel and got rid of a lot of the understeer by giving more castor (hence more turn-in neg. camber) and more straight-line stability. The front end geometry also doesn't change so much under heavy braking (front wheels splaying/toe-ing out and moving rearwards in the arch) as it did with the stock GM bushes which had too much compliancy.
245 tyres on the front will provide about another 1/2" of tread-width rubber on the road but for those that like to wind on static-load no lock negative camber, you'll be limited to about minus one degree -stock is 0* 12" +/- 18" -before the inside of the tyre contacts the strut.
Edited by sid447 on Tuesday 10th April 19:59
crisisjez said:
Pushed hard for the first time yesterday (for those that Know it the A331 westbound) was taking a sweeping lefthander at about 130ish and the back end started a cycling shimmy. Most disconcerting and not what I would have expected. Is this normal or does the car need to go on a ramp. (too old to crawl underneath)
www.pistonheads.com/gassing/topic.asp?t=377548&f=23&h=0
FYI
V8HSV said:
crisisjez said:
Pushed hard for the first time yesterday (for those that Know it the A331 westbound) was taking a sweeping lefthander at about 130ish and the back end started a cycling shimmy. Most disconcerting and not what I would have expected. Is this normal or does the car need to go on a ramp. (too old to crawl underneath)
www.pistonheads.com/gassing/topic.asp?t=377548&f=23&h=0
FYI
Hmmmmmmm.
well worth a full read, kinda puts a lot of things into context.
back to tyres again though I've just had some muppet telling me that you can't go wider than 225 on an 8J wheel. Needless to say he didn't get my business. The next one then suggested that if I want a bigger tyre then the profile would need to go up to a 45(!). Third time lucky though I'm sticking to a 235 on the front and going up to a 255 on the rear. apologies for hijacking your thread for a second time. I'll shut up now!!
well_fans said:
take it you mean 130kph for anyone thinking you were doing 130mph on a public highway and then admitting such a thing on a public forum......
Quite right and well worth pointing out, wouldn`t dream of exceeding the limit. Glad you got home safely, nice to meet you last Sun.
GTS 029 said:
V8HSV said:
crisisjez said:
Pushed hard for the first time yesterday (for those that Know it the A331 westbound) was taking a sweeping lefthander at about 130ish and the back end started a cycling shimmy. Most disconcerting and not what I would have expected. Is this normal or does the car need to go on a ramp. (too old to crawl underneath)
www.pistonheads.com/gassing/topic.asp?t=377548&f=23&h=0
FYI
Hmmmmmmm.
well worth a full read, kinda puts a lot of things into context.
back to tyres again though I've just had some muppet telling me that you can't go wider than 225 on an 8J wheel. Needless to say he didn't get my business. The next one then suggested that if I want a bigger tyre then the profile would need to go up to a 45(!). Third time lucky though I'm sticking to a 235 on the front and going up to a 255 on the rear. apologies for hijacking your thread for a second time. I'll shut up now!!
So for 255 on the rear, what section are you running? Is that on the 18 or 19 wheel? I'd love to get a wider piece of rubber on the deck at the rear so would that be 255 35 18?
Soz Gas Man
just put my reply on another thread about tyres. In a nutshell though I have a VT model GTS running the standard 8J wheel. I have kept the fronts the same ie 235/40/18 but have gone up to a 255/35/18 on the rear. The ratio size is just a percentage of the size of the whole tyre (I was always under the impression that it was a measurement in mm the same as the other numbers.) As the 255 is, on the whole a bigger tyre, to keep the rolling radius the same the profile needs to come down to compensate.
I am trying Nexens and they came in at £470 all in, they have a similar 'V' groove pattern to the goodyear F1 and my initial impressions are favourable.
There are probably other schools of thought about the profile of the tyre which will be contradicting to what I've just written. Usually its only necessary to downsize the profile if you are upsizing the wheel as it will have an effect on speedo accuracy etc. I discussed both options (255/40 and 255/35) and was recommended to use the 35 profile. Loads of guys on here with far more experience of this than I've got so I'm sure there will be other views as well.
just put my reply on another thread about tyres. In a nutshell though I have a VT model GTS running the standard 8J wheel. I have kept the fronts the same ie 235/40/18 but have gone up to a 255/35/18 on the rear. The ratio size is just a percentage of the size of the whole tyre (I was always under the impression that it was a measurement in mm the same as the other numbers.) As the 255 is, on the whole a bigger tyre, to keep the rolling radius the same the profile needs to come down to compensate.
I am trying Nexens and they came in at £470 all in, they have a similar 'V' groove pattern to the goodyear F1 and my initial impressions are favourable.
There are probably other schools of thought about the profile of the tyre which will be contradicting to what I've just written. Usually its only necessary to downsize the profile if you are upsizing the wheel as it will have an effect on speedo accuracy etc. I discussed both options (255/40 and 255/35) and was recommended to use the 35 profile. Loads of guys on here with far more experience of this than I've got so I'm sure there will be other views as well.
Edited by GTS 029 on Thursday 12th April 14:41
Many thanks for that, much appreciated. I have some experience of lowering profile sizes to compensate for greater width sections eg 165 60 13 to 185 55 13 on the old Metro Turbo (in my distant youth!).
Just never quite sure how much to reduce profile by to compensate. That has been a lot of help, and incidentally increases the options of tyres available (and in a range of prices too!)
Possibly irrelevant to this thread by finally bit the bullet and got my 04 CV8 booked into Monkfish next week for the essentials...
Sportpac, ripshifter, engine covers and VXR brakes
Just never quite sure how much to reduce profile by to compensate. That has been a lot of help, and incidentally increases the options of tyres available (and in a range of prices too!)
Possibly irrelevant to this thread by finally bit the bullet and got my 04 CV8 booked into Monkfish next week for the essentials...
Sportpac, ripshifter, engine covers and VXR brakes
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