rear end bobbing around on turns
10-20-2009, 11:06 AM
#16
There's a lot of rubber in the 993 rear suspension, it could be just all of it compressing and releasing.
The best thing I ever did for my cars handling was to go to harder RS rubber bushes on the arms and solid bushes on the sidemounts
The best thing I ever did for my cars handling was to go to harder RS rubber bushes on the arms and solid bushes on the sidemounts
10-20-2009, 11:31 AM
#17
Rennlist Member
Yup. I was thinking a lack of precision in the suspension movement causing small dynamic alignment changes... coupled with perhaps too big a rear (and front) sway bar that reduces warp (independent wheel movement). A stiff bushing (unlubricated and/or clamped too tight) would further reduce warp.
10-20-2009, 11:43 AM
#19
Yes, my '94 993 cab had bad motor mounts (they're frickin' 15 years old!)....the rear end felt vague in turns and unsettled....like there was a tank of water back there sloshing around, even when the car was driven spiritedly but not aggressively (it's a tip cab). I had the motor mounts that came out of my turbo installed in the cab (car is not driven aggressively nor often so was not looking to spend a huge amount) and problem solved.
10-20-2009, 12:34 PM
#20
Addict
Rennlist Member
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Thread Starter
Gee guys - thanks for all the suggestions.
I am using 315 Nittos back there, 245 in front, however it was doing it with 295 MPSC (235 front). I was running the MPSC at 36 hot rear and 34 front. I've been running the Nittos at between the same and +2 more. My rear bar is in the middle and the front bar is also in the middle of 5. The car understeers a bit on steady throttle, but I can induce throttle oversteer. The only alignment spec I remember is my camber is at -1.9 front and rear, which is pretty much maxed out.
Sounds like I should first check my motor mounts and suspension bushings, make sure my bar isn't binding and then try softening everything up, which really seems counter intuitive to me. I got some really sticky lube from Viper Bob at one point for the TRG bars. Anyone know what that stuff is or is he the only source? Can any mechanic check the suspension bushings? I assume its a visual to see if they are cracked and then a pry bar to see if they move too much the "art" being what is too much. I know my regular mechanic is going to want to change everything to ERP, so I may go somewhere else for this. Thanks.
Greg H.
I am using 315 Nittos back there, 245 in front, however it was doing it with 295 MPSC (235 front). I was running the MPSC at 36 hot rear and 34 front. I've been running the Nittos at between the same and +2 more. My rear bar is in the middle and the front bar is also in the middle of 5. The car understeers a bit on steady throttle, but I can induce throttle oversteer. The only alignment spec I remember is my camber is at -1.9 front and rear, which is pretty much maxed out.
Sounds like I should first check my motor mounts and suspension bushings, make sure my bar isn't binding and then try softening everything up, which really seems counter intuitive to me. I got some really sticky lube from Viper Bob at one point for the TRG bars. Anyone know what that stuff is or is he the only source? Can any mechanic check the suspension bushings? I assume its a visual to see if they are cracked and then a pry bar to see if they move too much the "art" being what is too much. I know my regular mechanic is going to want to change everything to ERP, so I may go somewhere else for this. Thanks.
Greg H.
10-20-2009, 01:08 PM
#21
Race Car
The swaybar mount is easy to check visually for any cracks etc. To check binding, just disconnect the drop links and move the bar, if it's hard to move it is binding. The binding also increases the effective rate of the bar as well (by how much is impossible to measure)
Someone will chime in on checking the engine mounts, I usually just lift the engine and see how much movement (vertical) there is in the engin prior to lifting the rear of the car.
If the sway bar bushings and the engine mounts are ok, then try softening the rear shocks (no other adjustments).
Someone will chime in on checking the engine mounts, I usually just lift the engine and see how much movement (vertical) there is in the engin prior to lifting the rear of the car.
If the sway bar bushings and the engine mounts are ok, then try softening the rear shocks (no other adjustments).
10-20-2009, 01:47 PM
#23
Rennlist Member
As you mentioned, we never ended up together on the track Friday. Wrong assortment of cars this time...... But who was telling you? This wasn't exactly a pro-level track day! When I'm in the SM and my pass/being passed ratio is 10+:1, that pretty much tells you all you need to know.
Basic question is how the car feels to YOU. Absent something flat-out broken, I can tell you the difference between the C4S and yellow car isn't even funny. Now depending on where you want to go, if everything pretty much checks out, you know what's entailed in replacing 10+ year old rubber in all those locations. Then the car sucks as a street car.
Basic question is how the car feels to YOU. Absent something flat-out broken, I can tell you the difference between the C4S and yellow car isn't even funny. Now depending on where you want to go, if everything pretty much checks out, you know what's entailed in replacing 10+ year old rubber in all those locations. Then the car sucks as a street car.
10-20-2009, 02:23 PM
#24
Rennlist Member
"Then the car sucks as a street car."
Great point...once you go past M030 and Bilstein HD with 993RS bars, any additional changes will impact street driving.
My car has lots of track mods.. would be a bit notchy on the street. The sidewalls on the tires are very low, stiff too, the sway bars creak...various noises creep into that cabin through the shifter, the monoballs...the monster sway bars, BUT, there are solutions to this:
Just change out the stock cats to cat bypass pipes or 200 cell cats and change out the mufflers too. You will be in a constant Grin
state driving the car...sure that couple across the street with the twins will hate you, but you didn't like them anyway, darn breeders with big carbon foot prints.
Yes my response is pretty much 
My car has lots of track mods.. would be a bit notchy on the street. The sidewalls on the tires are very low, stiff too, the sway bars creak...various noises creep into that cabin through the shifter, the monoballs...the monster sway bars, BUT, there are solutions to this:
Just change out the stock cats to cat bypass pipes or 200 cell cats and change out the mufflers too. You will be in a constant Grin
state driving the car...sure that couple across the street with the twins will hate you, but you didn't like them anyway, darn breeders with big carbon foot prints. Yes my response is pretty much
