Suspension tuning guru's - Spring rate question- - >
10-05-2006, 08:25 AM
#1
AudiWorld Super User
Thread Starter
Suspension tuning guru's - Spring rate question- - >
Trying to tune out a slight bit of understeer...
Current setup for aggressive street, no track time...
* Track Sport 600f / 700r SportPlus valving (aka Fletcher valving), rebound settings tuned with ryans4
* Intrax ARB's Anti Roll Bars
* Corner Balanced w/ ride height at 25.125" all corners except rf is 25.25"
Handling has a bias towards a slight bit of understeer, which I want to tune out. Other than this, I am very very happy with the handling and turn-in response. The obvious trade-off is a harsh ride which is a compromise I can live with given I won't be buying a new set of Penske's or Ohlins.
Last night I installed the stock front sway bar (stock = 27mm, Intrax = 29mm) and kept the Intrax rear bar. I achieved the desired result of slightly less understeer.
I have a hollow A4 front bar which could effectively further reduce understeer if needed.
Here's the rub...literally. With the reduction in front end stiffness I expect my front tires to rub. 18x8.5 ET 36 with 245/35 T1R's, 50% front fender roll.
My questions -
Are my expectations correct with regard to the rubbing? I think yes...similar result to dropping the ride height in corners..
Assuming I go back to the Intrax 29mm front bar, how much additional rear spring rate would be required to inflict the same amount of additional oversteer as was achieved with the 2mm reduction in front sway bar?
Current setup for aggressive street, no track time...
* Track Sport 600f / 700r SportPlus valving (aka Fletcher valving), rebound settings tuned with ryans4
* Intrax ARB's Anti Roll Bars
* Corner Balanced w/ ride height at 25.125" all corners except rf is 25.25"
Handling has a bias towards a slight bit of understeer, which I want to tune out. Other than this, I am very very happy with the handling and turn-in response. The obvious trade-off is a harsh ride which is a compromise I can live with given I won't be buying a new set of Penske's or Ohlins.
Last night I installed the stock front sway bar (stock = 27mm, Intrax = 29mm) and kept the Intrax rear bar. I achieved the desired result of slightly less understeer.
I have a hollow A4 front bar which could effectively further reduce understeer if needed.
Here's the rub...literally. With the reduction in front end stiffness I expect my front tires to rub. 18x8.5 ET 36 with 245/35 T1R's, 50% front fender roll.
My questions -
Are my expectations correct with regard to the rubbing? I think yes...similar result to dropping the ride height in corners..
Assuming I go back to the Intrax 29mm front bar, how much additional rear spring rate would be required to inflict the same amount of additional oversteer as was achieved with the 2mm reduction in front sway bar?
10-05-2006, 08:49 AM
#3
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Could you get the suspension to the bump stops with the thicker bar? If it didn't rub then it's not
going to rub now. Ar you running stock control arms or adjustable? What are your camber settings?
The toyos run a bit narrow, too. Section width of only 9.6 in that size vs. 9.9 for me on my dunlop super sports, same size.
Can't answer your last question. There's probably a caculation for it but i don't know it.
The toyos run a bit narrow, too. Section width of only 9.6 in that size vs. 9.9 for me on my dunlop super sports, same size.
Can't answer your last question. There's probably a caculation for it but i don't know it.
10-05-2006, 08:53 AM
#4
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Here's a way to get a rough estimate...
Given the different diameters of the stock and Intrax front bars you can calculate the approximate % difference in spring rate between the two. Take that % and add it to your current rear coil spring rate. Or just add 100lbs to the rear rate and see what happens 
10-05-2006, 09:12 AM
#5
AudiWorld Super User
Thread Starter
Stock CA's...
<img src="http://images9.fotki.com/v173/photos/4/43687/2137991/AlignmentSpecs-vi.jpg">
I would love to go with adjustable CA's if I could find a set that won't rattle....I am toasting tires two a year...
I would love to go with adjustable CA's if I could find a set that won't rattle....I am toasting tires two a year...
