Cocked the handling up - any ideas?
Discussion
2009 Astra 1.8.
No fireball by any stretch of the imagination but, before I had 2 new rear tyres fitted, I knew it's limits and how it would react in certain situations.
However, since having 2 new Dunlop tyres fitted on the rear the 'handling' has gone to pot.
I think it's now suffering from, basically, the new tyres outperforming the fronts.
It's demonstrated by, at say 60/70mph, and just flicking the steering from left to right. What follows is that the front will change direction then there's a sort of squirm where it seems that the back then catches up. It's quite un-nerving at first, especially on the same day as changing when the fitters had only put 31psi and it was bucking around like a kangeroo. Previously the pressures were 36 all round - as recommended for 'economy driving' in the handbook. Pumping the new rears up to 36 improved things a lot, but it's still there.
Rear are Dunlop Sport BluResponse (V rated) and the fronts are Bridgestone Turanzas (H rated).
When I was buying the new Dunlops I could get the V rated versions for the same price thinking it would improve handling.
Obviously now I know I should have perhaps gone for H rated to match the fronts.
Do you reckon messing with pressures will improve matters - perhaps reducing the fronts?
Or, should I just concentrate on wearing down the fronts as quickly as possible so I can get some more Dunlops?
No fireball by any stretch of the imagination but, before I had 2 new rear tyres fitted, I knew it's limits and how it would react in certain situations.
However, since having 2 new Dunlop tyres fitted on the rear the 'handling' has gone to pot.
I think it's now suffering from, basically, the new tyres outperforming the fronts.
It's demonstrated by, at say 60/70mph, and just flicking the steering from left to right. What follows is that the front will change direction then there's a sort of squirm where it seems that the back then catches up. It's quite un-nerving at first, especially on the same day as changing when the fitters had only put 31psi and it was bucking around like a kangeroo. Previously the pressures were 36 all round - as recommended for 'economy driving' in the handbook. Pumping the new rears up to 36 improved things a lot, but it's still there.
Rear are Dunlop Sport BluResponse (V rated) and the fronts are Bridgestone Turanzas (H rated).
When I was buying the new Dunlops I could get the V rated versions for the same price thinking it would improve handling.
Obviously now I know I should have perhaps gone for H rated to match the fronts.
Do you reckon messing with pressures will improve matters - perhaps reducing the fronts?
Or, should I just concentrate on wearing down the fronts as quickly as possible so I can get some more Dunlops?
doogz said:
What did it do before you fitted new tyres, when you flicked the wheel left to right?
The steering wheels respond first, since they’re the ones you’re asking to work.
I don’t quite understand the problem.
It's hard to describe really. The steering wheels respond first, since they’re the ones you’re asking to work.
I don’t quite understand the problem.
Previously it did what you say, steer and change direction, simple.
It does the same now, but there's a sort of 'squirm' after the change of direction has happened, a sort of sideways shimmy - as if the tyre walls are flexing at different rates.
Or the tread blocks flexing?
Firstly, I very much doubt you'd notice any difference between H and V rated dunlops, as there's very little difference.
Secondly, what were the previous rear tyres? If they were some unknown chinese ditchfinders, then you may have been loose at the rear. The blue response tyres are the "eco" dunlop, whether that has something to do with the bouncy ride you describe, I'm not sure.
Dare I say it, you may just be feeling the actual handling characteristics of the Astra for the first time? (ie, safe boring understeer)
Secondly, what were the previous rear tyres? If they were some unknown chinese ditchfinders, then you may have been loose at the rear. The blue response tyres are the "eco" dunlop, whether that has something to do with the bouncy ride you describe, I'm not sure.
Dare I say it, you may just be feeling the actual handling characteristics of the Astra for the first time? (ie, safe boring understeer)
Could be that the new ones have a much softer sidewall than the old ones, in which case you may be able to tune a bit with pressures but otherwise just learn to drive around it, try less agressive steering inputs to let the rear settle - I've had a similar issue with sportier tyres on the front and touring tyres on the rear.
Give them a bit more time to scrub in though, it could just be that.
Give them a bit more time to scrub in though, it could just be that.
205/55 x 16 - so there's definitely plenty of sidewall. 
Softer sidewalls? Yeah, this is what I'm thinking.
I could see that causing what's happening.
It only happens if I 'make it happen'. So under normal driving you'd never noticed and it's something you could easily manage.
But I know it's there now so, under the right circumstance, will expect it (well at least while they're still new).
Softer sidewalls? Yeah, this is what I'm thinking.
I could see that causing what's happening.
It only happens if I 'make it happen'. So under normal driving you'd never noticed and it's something you could easily manage.
But I know it's there now so, under the right circumstance, will expect it (well at least while they're still new).
Edited by Fastra on Thursday 13th June 12:58
Fastra said:
205/55 x 16.
So there's definitely plenty of sidewall.
Softer sidewalls? Yeah, this is what I'm thinking.
I could see that causing what's happening.
Does it tell you the number of ply's (is that even a word?) on the sidewall ? So there's definitely plenty of sidewall.
Softer sidewalls? Yeah, this is what I'm thinking.
I could see that causing what's happening.
6 ply fronts and 8 ply rears perhaps (IIRC eco tyres are stiffer to save fuel)
robinessex said:
Maybe this. Many years ago I mixed makes on a Lotus Europa. Nearly scared myself to death on the first fast corner. Turned the car round, and went back and had 2 more (same make) tyres fitted. Problem solved.
Thank god for the that then. 
Thought it was just me and my soft, sensitive arse.
Are they the correct load rating for the car?
Also - are they the same load rating as what is fitted at the front?
I find this is something that's often overlooked when buying new tyres.
ETA: Kwik Fit are listing tyres with a load index of 91 (mostly) but there are a couple with load index 94.
What do you have currently OP?
Also - are they the same load rating as what is fitted at the front?
I find this is something that's often overlooked when buying new tyres.
ETA: Kwik Fit are listing tyres with a load index of 91 (mostly) but there are a couple with load index 94.
What do you have currently OP?
Edited by TonyRPH on Thursday 13th June 13:12
Another test is to rotate them front/rear and see how it feels - you may be able to feel the extra flex more easily through the steering and/or analyse what is different.
An example: At one stage I had 2x Toyo T1R and 2x Bridgestone RE001 on the Legacy - similar grip level but different construction, the Toyos were far softer in the sidewalls. With the Toyos on the front it was terrible, vague steering feel and was borderline dangerous the way the nose followed bumps and darted around quite unpredictably. Through an interesting piece of road I know fairly well I ended up >20km/h slower than usual as I just had no confidence in the front end.
As soon as I got home I rotated front/rear and it was fine, better than it had been with 4x Toyos previously. 4x RE001 later on was better again, but the T1R front/RE001 rear combination was uniquely appalling - I guess sometimes with mixed tyres you can get a strange combination of effects that is far worse than any of the tyres would be exclusively.
An example: At one stage I had 2x Toyo T1R and 2x Bridgestone RE001 on the Legacy - similar grip level but different construction, the Toyos were far softer in the sidewalls. With the Toyos on the front it was terrible, vague steering feel and was borderline dangerous the way the nose followed bumps and darted around quite unpredictably. Through an interesting piece of road I know fairly well I ended up >20km/h slower than usual as I just had no confidence in the front end.
As soon as I got home I rotated front/rear and it was fine, better than it had been with 4x Toyos previously. 4x RE001 later on was better again, but the T1R front/RE001 rear combination was uniquely appalling - I guess sometimes with mixed tyres you can get a strange combination of effects that is far worse than any of the tyres would be exclusively.
Edited by GravelBen on Thursday 13th June 13:18
Gassing Station | General Gassing | Top of Page | What's New | My Stuff