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CoolHandMoss · 09-10-2019, 08:09 AM

I'm getting a little frustrated with my setup development so maybe the community here has some helpful advice. Throughout the last two years of running a twin in STX I have tried a variety of setups in terms of spring rates and sway bars and I have consistently had issues with mid-turn push. The current setup is 350F/400R, stock rear bar, Karcepts front bar. Caster is 7*, 4.1* camber in the front and 2.5* in the rear. I have about 3mm of positive rake. I currently run rivals and I run the fronts at 27 PSI and I get just a little roll over on the edge but not a lot. I've tried down to 26 PSI and that was definitely not an improvement. I've checked tire temperatures and I find about 15* warmer on the inside edge with the middle measuring closer to the outside edge than the inside which has led me to experiment again with higher front pressures which has yielded mixed results. I like the turn in but it doesn't help my mid turn grip problem. Turn in feels very good as is and the car transitions pretty well. Once I shed enough speed to get the front end planted the car exits very well with good balance on throttle. Generally adding throttle to rotate out of the push will just cause more push unless the speed is just right to have the power to really break the rears loose. The car also will not trail brake at all. Holding a little brake in to a turn just causes the car to push on entry rather than turn in nicely before pushing. Almost every single sweeper or 90* at nats was a nightmare. I was slowing more than I wanted to before turn in, getting a decent entry and then once the car was set the front end just pushed until I shed enough speed to be able to get on the gas so I was always on the gas late.

I've ended up adjusting the front bar down to the third softest setting of 7 which is still rather stiff at 346 lbs. In order to keep turn in crisp when changing to softer sway bar settings I have bumped front compression damping up to about 7 clicks on MCS.

The obvious course of action I think would be to continue softening the front or to stiffen the rear but the problem I am running in to is that the front is already getting to the point where it's soft enough to be close to running out of travel. I made sure that I'm maximizing travel in the front when installing this suspension system. I use a bump stop that contacts the damper body within a few mm of when the tire contacts the fender liner. I am not currently running out of front travel but pictures of the car on course show that it's not too far from doing so. I've tried the front bar all the way up to almost full stiff and that really made the problem worse. I've tried a stiffer rear bar but that made the rear end really snappy under throttle and I had trouble putting power down. I believe the next thing I am going to try is stiffer rear springs (450 lbs as I can't find any 425s in the right length) and if the car gets too loose I can balance that out with more front sway. I'm not really a fan of this solution though because I already am not using all of my rear travel. I took a video of the rear suspension motion at the damper on a rough road through some hard turns and found that the suspension is really only traveling through 60% of the available range and as such stiffer springs will really only act to sacrifice rear grip rather than to improve front grip.

Another solution I have considered is to use some rear toe out. I have usually kept rear toe at 0 but currently I have just a hair of rear toe in, about 2mm total.

Understandably, many will say that this problem is more a result of driving style than of setup. I have been trying to drive around this by reducing entry speeds and keeping steering inputs smooth but in order to avoid this mid-turn push I end up sacrificing entry speed so much that I'm just slow. Not to mention, using some rear compression damping has the car so balanced on initial turn in that it's even harder to give up that entry speed.

I would appreciate any constructive input on this. I'm just stumped as to whether the front end is pushing because it's too stiff, is it a matter of tire pressure and/or camber, is it that there is not enough front roll stiffness and the body is rolling too much, or are the weight distribution and other inherent characteristics of this car just such that I need to accept limiting rear travel and grip by going too stiff on the rear springs in order to get the car balanced out mid turn so I can get on the throttle earlier.

09-10-2019, 08:09 AM	#3707
CoolHandMoss Senior Member Join Date: Jan 2018 Drives: 2013 FRS Location: VA Posts: 305 Thanks: 1 Thanked 86 Times in 55 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	I'm getting a little frustrated with my setup development so maybe the community here has some helpful advice. Throughout the last two years of running a twin in STX I have tried a variety of setups in terms of spring rates and sway bars and I have consistently had issues with mid-turn push. The current setup is 350F/400R, stock rear bar, Karcepts front bar. Caster is 7, 4.1 camber in the front and 2.5* in the rear. I have about 3mm of positive rake. I currently run rivals and I run the fronts at 27 PSI and I get just a little roll over on the edge but not a lot. I've tried down to 26 PSI and that was definitely not an improvement. I've checked tire temperatures and I find about 15* warmer on the inside edge with the middle measuring closer to the outside edge than the inside which has led me to experiment again with higher front pressures which has yielded mixed results. I like the turn in but it doesn't help my mid turn grip problem. Turn in feels very good as is and the car transitions pretty well. Once I shed enough speed to get the front end planted the car exits very well with good balance on throttle. Generally adding throttle to rotate out of the push will just cause more push unless the speed is just right to have the power to really break the rears loose. The car also will not trail brake at all. Holding a little brake in to a turn just causes the car to push on entry rather than turn in nicely before pushing. Almost every single sweeper or 90* at nats was a nightmare. I was slowing more than I wanted to before turn in, getting a decent entry and then once the car was set the front end just pushed until I shed enough speed to be able to get on the gas so I was always on the gas late. I've ended up adjusting the front bar down to the third softest setting of 7 which is still rather stiff at 346 lbs. In order to keep turn in crisp when changing to softer sway bar settings I have bumped front compression damping up to about 7 clicks on MCS. The obvious course of action I think would be to continue softening the front or to stiffen the rear but the problem I am running in to is that the front is already getting to the point where it's soft enough to be close to running out of travel. I made sure that I'm maximizing travel in the front when installing this suspension system. I use a bump stop that contacts the damper body within a few mm of when the tire contacts the fender liner. I am not currently running out of front travel but pictures of the car on course show that it's not too far from doing so. I've tried the front bar all the way up to almost full stiff and that really made the problem worse. I've tried a stiffer rear bar but that made the rear end really snappy under throttle and I had trouble putting power down. I believe the next thing I am going to try is stiffer rear springs (450 lbs as I can't find any 425s in the right length) and if the car gets too loose I can balance that out with more front sway. I'm not really a fan of this solution though because I already am not using all of my rear travel. I took a video of the rear suspension motion at the damper on a rough road through some hard turns and found that the suspension is really only traveling through 60% of the available range and as such stiffer springs will really only act to sacrifice rear grip rather than to improve front grip. Another solution I have considered is to use some rear toe out. I have usually kept rear toe at 0 but currently I have just a hair of rear toe in, about 2mm total. Understandably, many will say that this problem is more a result of driving style than of setup. I have been trying to drive around this by reducing entry speeds and keeping steering inputs smooth but in order to avoid this mid-turn push I end up sacrificing entry speed so much that I'm just slow. Not to mention, using some rear compression damping has the car so balanced on initial turn in that it's even harder to give up that entry speed. I would appreciate any constructive input on this. I'm just stumped as to whether the front end is pushing because it's too stiff, is it a matter of tire pressure and/or camber, is it that there is not enough front roll stiffness and the body is rolling too much, or are the weight distribution and other inherent characteristics of this car just such that I need to accept limiting rear travel and grip by going too stiff on the rear springs in order to get the car balanced out mid turn so I can get on the throttle earlier.