Handling Questions
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Burning Brakes
Joined: Mar 2005
Posts: 909
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Handling Questions
here goes...
When I got my c2 it had some mostly worn out mxxv5 or somesuch michelin pilots on it. The car was loose as could be so I never pushed it in the turns.
I solved my performance issues so I bought some Michelin Pilot Sports for it.
Now I've been pushing the car more in turns. I live in the so-called mountains of the eastern us so I have plenty of windy twisty roads. Now that I am actually exploring the cars bounds I have a couple questions.
I did drive a porsche quite a bit when I was younger, but it was a 73 911 and I never really explored its bounds. Other than this I've mostly driven front wheel drive vehicles. So, some of what I'm going to say may be common sense to you fellows. Try not to make too much fun of me.
With 44lbs in the rear tires it is just too loose for my liking. I dropped them to 41 in back and left the standard 36 in front. I'm running stock tire sizes all around on the stock 16in wheels. Car background:
90 C2 w/ the limited slip diff option. Stock with a cat bypass.
Turn in and overall grip seems great, but, when i get on the throttle, even a little, the car will push (understeer). It will do this even in rather minor (fast sweeping) turns. If I am accelerating in a turn already and let off the gas the car will turn quicker and I have to correct with less steering.
At first my guess was the differential. Problem with this theory is it does it well before the tires should have a 40% speed differencef.
Could it be worn rear suspension arm bushings allowing the rear to toe-in during acceleration? I have raced rather complicated model cars in the past, so I am familiar with suspension theory. Adapting that theory over to a full size car with many more restictions on space and such is a different story.
Thanks for any input.
When I got my c2 it had some mostly worn out mxxv5 or somesuch michelin pilots on it. The car was loose as could be so I never pushed it in the turns.
I solved my performance issues so I bought some Michelin Pilot Sports for it.
Now I've been pushing the car more in turns. I live in the so-called mountains of the eastern us so I have plenty of windy twisty roads. Now that I am actually exploring the cars bounds I have a couple questions.
I did drive a porsche quite a bit when I was younger, but it was a 73 911 and I never really explored its bounds. Other than this I've mostly driven front wheel drive vehicles. So, some of what I'm going to say may be common sense to you fellows. Try not to make too much fun of me.
With 44lbs in the rear tires it is just too loose for my liking. I dropped them to 41 in back and left the standard 36 in front. I'm running stock tire sizes all around on the stock 16in wheels. Car background:
90 C2 w/ the limited slip diff option. Stock with a cat bypass.
Turn in and overall grip seems great, but, when i get on the throttle, even a little, the car will push (understeer). It will do this even in rather minor (fast sweeping) turns. If I am accelerating in a turn already and let off the gas the car will turn quicker and I have to correct with less steering.
At first my guess was the differential. Problem with this theory is it does it well before the tires should have a 40% speed differencef.
Could it be worn rear suspension arm bushings allowing the rear to toe-in during acceleration? I have raced rather complicated model cars in the past, so I am familiar with suspension theory. Adapting that theory over to a full size car with many more restictions on space and such is a different story.
Thanks for any input.
RL Community Team
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Joined: Oct 2003
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Likes: 880
It sounds like you have the stock suspension, yes? If so, you may need to "upgrade" various aspects of your suspension to achieve the desired effect. 964's in general will have a greater understeering tendency when stock versus an early 911; all that power of a 3.6 certainly helps worsen the problem!
Things you'll find on this forum that have been mentioned to help with the understeering:
wider front tires (use 225's instead of 205's)
stiffer rear sway bar (or looser front)
stiffer rear shocks
As DaveK says, alignment makes a difference, but it's really easy to alter handling with changes to the above items. Sway bars might be the cheapest overall fix that benefits a street car the most since you don't lose much in ride quality, and don't need a full alignment and corner balance afterwards!
It's doubtful that the differential would make that much difference, unless it was completely locked - but that's not a "limited slip"!
Hope that helps point you in the right direction
Things you'll find on this forum that have been mentioned to help with the understeering:
wider front tires (use 225's instead of 205's)
stiffer rear sway bar (or looser front)
stiffer rear shocks
As DaveK says, alignment makes a difference, but it's really easy to alter handling with changes to the above items. Sway bars might be the cheapest overall fix that benefits a street car the most since you don't lose much in ride quality, and don't need a full alignment and corner balance afterwards!
It's doubtful that the differential would make that much difference, unless it was completely locked - but that's not a "limited slip"!
Hope that helps point you in the right direction
Burning Brakes
Joined: Mar 2002
Posts: 1,081
Likes: 1
From: WhippetWorld, .........is it really only this many
Originally Posted by Heirsh
.
With 44lbs in the rear tires it is just too loose for my liking. I dropped them to 41 in back and left the standard 36 in front. I'm running stock tire sizes all around on the stock 16in wheels. Car background:
With 44lbs in the rear tires it is just too loose for my liking. I dropped them to 41 in back and left the standard 36 in front. I'm running stock tire sizes all around on the stock 16in wheels. Car background:
Turn in and overall grip seems great, but, when i get on the throttle, even a little, the car will push (understeer). It will do this even in rather minor (fast sweeping) turns. If I am accelerating in a turn already and let off the gas the car will turn quicker and I have to correct with less steering.
Once you have understeer the front tyres loose a significant part of their grip so that they are always going to give way even if you increase throttle (unleess you have much more than stock power). You can eliminate the understeer by winding off the lock a little to regain grip with the front tyres. If the front tyres start to bite and you are under power you can turn your understeer into oversteer. Lifting off the gas as you describe has a similar effect in that because you are no longer pushing the car into understeer the front grips and turns in. If you do a big enough lift the car will rotate but you then have the problem of no power to the rear wheels unless you are quick and you won't always catch it and spin.
Drifting
Joined: Jun 2002
Posts: 2,464
Likes: 25
From: colchester UK
I tend to agree with Tony,
My C2 on stock setup gets great initial turn in, but if you apply power the front end will soon wash out and understeer is the order of the day......mind you lift off oversteer has given me a few scares......
kevin
My C2 on stock setup gets great initial turn in, but if you apply power the front end will soon wash out and understeer is the order of the day......mind you lift off oversteer has given me a few scares......
kevin
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Burning Brakes
Joined: Mar 2005
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Well the suspension is certainly safe the way it is right now and I guess thats better than being tail happy.
It just seems so odd that I can feel this affect even on normal turns. I'll be doing a valve adjustment and some anti-squeal additions to the rear brakes soon so while I'm back there I'll do a thorough inspection. I really think there is play in the rear arms causing toe in under acceleration. But, on the other hand, I don't have a lot to compare it to. Thus is why i came here with my questions.
It just seems so odd that I can feel this affect even on normal turns. I'll be doing a valve adjustment and some anti-squeal additions to the rear brakes soon so while I'm back there I'll do a thorough inspection. I really think there is play in the rear arms causing toe in under acceleration. But, on the other hand, I don't have a lot to compare it to. Thus is why i came here with my questions.
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Burning Brakes
Joined: Mar 2002
Posts: 1,081
Likes: 1
From: WhippetWorld, .........is it really only this many
Originally Posted by Heirsh
It just seems so odd that I can feel this affect even on normal turns.
which does set alarm bells ringinging though. It's difficult to say what is normal behaviour and what isn't unless you can compare directly.
I would say that they should feel planted unless you are driving enthusiasticly and that the tendancy for the front to bobble about is often caused by poor alignment.
Alignment is fairly critical and I found that correct alignment transformed the car ( it was on stock suspension and still understeered when going quickly but felt planted at road speed)
See Dave does know what he's talking about after all
