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Lifting a rear wheel…thoughts?

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1,022
99
Exp. Type
HPDE
Exp. Level
10-20 Years
Texas
0Shot%202015-06-02%20at%207.48.34%20PM_zpseslp8ehv.png

I always knew I was lifting a rear wheel under brakes on turn-in. This is just the first picture I have found as evidence but I believe I've lifted the rear wheel even higher than is shown in this picture.

The problem is when I transition back to power I am spinning an inside wheel until the suspension sets and the weight is transferred back to the rear. Should my torsion diff be doing this? The wheel is off the ground in the air but should the diff be locking both wheels together? There is only one turn where I feel this at NCM, turn 2. I know stiffer spring rates up front or a larger front sway bar would probably help with this. I think I may even be lifting a front inside wheel when I use the curbing on corner exit.

I'm on Koni's, sportlines, and the stock sway bars.

Thoughts?
 
Flyboygsxr said:
You need to push harder so you get both inside wheels off the ground. :p
 
I'm not your guy to fix the wheel lift problem other than to say a smaller rear swaybar may help. As for the Torsen dif it acts just like an open dif once either tire is lifted off the ground. That is to say it functions great providing power to the wheel with the most grip as long as both tires remain on the ground, but once one is off the ground it becomes a one wheel peel open dif.
 
1,022
99
Exp. Type
HPDE
Exp. Level
10-20 Years
Texas
That's good to know, I thought I broke the diff. On the sticky Pirellis the wheel lifting problem is even worse.

I don't want to go to a smaller rear sway bar because the car feels balanced on the current setup running square. If anything I have more front grip than rear and I like that. When I run a staggered setup it pushes and that can be so frustrating when the car just won't turn.

Thanks for the info
 

steveespo

Lord knows I'm a Voodoo Child
Moderator
4,008
1,924
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W2W Racing
Exp. Level
10-20 Years
Cookeville TN
Compromise is the key. I get that you like the loose setup but as you found out it impacts braking behavior and power on exit. I had to lower rear spring rate from 375 to 300 with my 18mm rear bar to eliminate wheel hop under braking and to get back to full throttle early on corner exit. I also softened rear compression and stiffened rebound, while stiffening front compression and softening rebound. This helped with brake dive and overall balance for my driving preference. I look at what the Mustangs in Continental Challenge do with their setups, the back of the car rolls and twists but the rear tires stay planted. I have found that spring rate is more important than bar diameter out back. Stock diameter springs aren't offered in rates high enough for what the chassis wants. My high $ coil over setup gives the flexibility to tune but I would not recommend for street duty. Give a smaller rear bar a try, they are only $75 on ebay and take 15 minutes to swap in the pits at an event.
Steve
 
1,022
99
Exp. Type
HPDE
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10-20 Years
Texas
There are so many things I want to do to the car but I have already done 4 events this year so the piggy bank is very low. Coilovers, roll cage, clutch and flywheel are on my mod list along with many other things I can't afford. The piggy bank is empty right now after doing 4 events already this year.

What coil over setup are you running Steve? I would love to go with a two way adjustable system but I wouldn't know where to start on adjustments.

Thanks for the good info

Adam
 

steveespo

Lord knows I'm a Voodoo Child
Moderator
4,008
1,924
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Adam
I am running the Maximum Motorsports JRi 2 way adjustable setup. Cortex has a similar setup for a similar price. The MM setup keeps the rear springs on the axles so spring changes at the track take 10 minutes. I am really happy but they are for track only. The ride is harsh and I wouldn't want to wear the shocks and struts out on the street (they are rebuildable but spendy).
I get the budget thing, that's why I say try the rear bar, not too expensive and the Koni yellows give you pretty good tuning capability. The car responds well to stiff front, softer rear and take off slicks. Have fun, you are a pretty quick driver as it is.
Steve
 
598
536
Here's my take, I'm not a fan of jump on the Coil-over band wagon, I have used Coil-overs on my car and others, swapped them out for a more conventional setup with Koni yellows and Maximum Motorsports springs. I use a Eibach front sway bar set on full stiff with a 18mm rear bar. I run squared and very balanced. Staggered I set the front sway bar to the middle. Ford racing rear anti squat brackets with Ford racing boss 302r arms. It's really as basic as you can get. I can drive on the street all day long with no issues. On the track I can put power down mid corner and full throttle by corner exit, even when I was running 3:73's. The other thing I enjoy is being able to change my line though a corner with out up setting the car. As nice as coil-overs are, you don't need them to run well at the track. I know most will disagree with me about coil-overs and tell you to get them..and that's fine, but for the money spent, you can't go wrong with this simple set up. No watts link, I tried the Cortex Watts link and pulled it back out and sold it. Went back to a Ford racing boss302r panhard bar. I pulled the Watts out because I could never get the center section to say put, It would always come lose and drip gear oil. Back to back testing at Button Willow didn't show a change in lap time or the way the car felt. Same day, same car, same tires (slicks). It didn't give anything up in the esses or cotton corner. Bumps don't upset the car. This is just my .02 cents worth.
 

Grant 302

basic and well known psychic
I'd start with increasing the damping up front. Maybe even if it's just the front right assuming this only happens on this left-hander.

I know you said you didn't want to change the balance of the car, but maybe the GT 24mm rear sway would work for you. I don't think you'd get the balance you want from one of the smaller bars.

That said, I don't think you have a problem if you like the balance. I think I'd try to revise my line for that corner, and take advantage of how the car rotates. More 'diamond'-like. And are you trail braking? I've only lifted the rear (that I know of) on FWD cars. So consider me a little impressed. 8)
 
1,022
99
Exp. Type
HPDE
Exp. Level
10-20 Years
Texas
Next time I get out I want to come cameras on the car so that I can see what the rear suspension and rear wheels are doing. Ideally I would like to have three…one on each wheel and one showing the movement of the upper control arm as the suspension articulates. Actually, make that 5 cameras :) One for each lower control arm also unless you could figure a way to watch the control arm and the wheel with the same camera. Who will be the first to do this experiment for me?

Adam

PS…I know I can be fast on the suspension I have currently but where I see the advantage of coil overs is in transition sections i.e. the esses at NCM and VIR also. It takes longer for the suspension to set because there is more roll and body movement. Seems the only way to get really high spring rates is with coil overs.
 
Here is a camera that could easily be sacrificial. I have a different version of the 808 "family", and it works great. This one appears to be a #24 according to one reviewer. Not the best, but it's only $7 so you can't expect it to be great. Some people seem to have gotten faulty ones, so it might be a hit-or-miss buy. The #16 version is actually a lot nicer, but more costly than I would consider for attaching to the underside of car at $42.

For something this small you could fasten it with zip ties (as long as you can keep it from vibrating too much the picture should be fine). I had mounted mine with Velcro to the splitter:) The only issue I had was the cmos lens glue melting in the sun, the splitter was baking it. The camera does not have a beep, just an few blinks of an LED to indicate it is recording. So putting it somewhere you can get video and see the LED might be a hassle. I drilled the LED holes out on my case so I would not have to be dead-on to see it blink.

Cheap 808 #24:
http://www.banggood.com/Wholesale-Mini-DVR-808-Car-Key-Chain-Micro-Camera-Pocket-Camcorder-p-48256.html

$42 808 #16:
http://www.banggood.com/808-NO_16-HD-120-Degree-Mini-Camera-Module-7g-p-82197.html
and this site is a good resource:
http://www.chucklohr.com/808/c16/
 

ArizonaBOSS

Because racecar.
Moderator
8,730
2,734
Arizona, USA
Compromise is the key. I get that you like the loose setup but as you found out it impacts braking behavior and power on exit. I had to lower rear spring rate from 375 to 300 with my 18mm rear bar to eliminate wheel hop under braking and to get back to full throttle early on corner exit. I also softened rear compression and stiffened rebound, while stiffening front compression and softening rebound. This helped with brake dive and overall balance for my driving preference. I look at what the Mustangs in Continental Challenge do with their setups, the back of the car rolls and twists but the rear tires stay planted. I have found that spring rate is more important than bar diameter out back. Stock diameter springs aren't offered in rates high enough for what the chassis wants. My high $ coil over setup gives the flexibility to tune but I would not recommend for street duty. Give a smaller rear bar a try, they are only $75 on ebay and take 15 minutes to swap in the pits at an event.
Steve
@nsfw302
 

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
Here's my take, I'm not a fan of jump on the Coil-over band wagon, I have used Coil-overs on my car and others, swapped them out for a more conventional setup with Koni yellows and Maximum Motorsports springs. I use a Eibach front sway bar set on full stiff with a 18mm rear bar. I run squared and very balanced. Staggered I set the front sway bar to the middle. Ford racing rear anti squat brackets with Ford racing boss 302r arms. It's really as basic as you can get. I can drive on the street all day long with no issues. On the track I can put power down mid corner and full throttle by corner exit, even when I was running 3:73's. The other thing I enjoy is being able to change my line though a corner with out up setting the car. As nice as coil-overs are, you don't need them to run well at the track. I know most will disagree with me about coil-overs and tell you to get them..and that's fine, but for the money spent, you can't go wrong with this simple set up. No watts link, I tried the Cortex Watts link and pulled it back out and sold it. Went back to a Ford racing boss302r panhard bar. I pulled the Watts out because I could never get the center section to say put, It would always come lose and drip gear oil. Back to back testing at Button Willow didn't show a change in lap time or the way the car felt. Same day, same car, same tires (slicks). It didn't give anything up in the esses or cotton corner. Bumps don't upset the car. This is just my .02 cents worth.


Adding my two cents.... I would have agreed with you until I put in the Cortex setup with koni single adj shocks. Its was the race setup with 600#/350# and on soft setting it rides better then the stock Boss adjustables with P springs... I would have never thought that till I saw another GT with the same set up first. I imagine its mainly to do with the shock valving?
 
598
536
Adding my two cents.... I would have agreed with you until I put in the Cortex setup with koni single adj shocks. Its was the race setup with 600#/350# and on soft setting it rides better then the stock Boss adjustables with P springs... I would have never thought that till I saw another GT with the same set up first. I imagine its mainly to do with the shock valving?
I can see that, I ran The Ground Control coil overs on my 05 GT Autocross car with rates like that. One of the best ride ever, was very smooth and fast. I do run coil overs from time to time, swapping is easy. Right now I'm on Bilsteins and MM springs. Last year at Sonoma I was on my Ford Racing Boss 302s coil overs (Needs rebuilding now) I also have JRI's that I use time to time. I love coil overs, I just feel not always needed. That's all. If you can afford them buy them. If not there are other setups that work well too.
 
6,361
8,184
I tried to find some pics of our cars, they don't quite lift the inside wheel (if they stay off the curbs) but they are right there. The last pic is with an 18mm or bigger bar, the first 2 are 18mm or no bar, and of course, the stickier Pirelli Tires. I would like to point out the rollover in the last pic.
I think you are on the right track



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323
318
Exp. Type
Autocross
Exp. Level
20+ Years
So Cal
I don't want to go to a smaller rear sway bar because the car feels balanced on the current setup running square. If anything I have more front grip than rear and I like that. When I run a staggered setup it pushes and that can be so frustrating when the car just won't turn.

If you don't change the car, you won't change the car. You need stiffer front springs and bars. The springs in particular will not increase understeer. The bar may, but it's worth it because you can go to throttle so much earlier.

I'll also agree with the rear bar comment, although it probably won't influence the tire lift much. What it will do is stick the rear. The biggest influence, by far, on the handling of any car is your feet. Load the front properly and I guarantee it will turn.

The diff is acting as it should, which is freewheeling when one tire is unloaded. What you really need is preload and the stock Torsen isn't built with much.
 

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