Wheelspin in turns

[marksawatsky]

I have a scratch built autocross car and when I'm turning and accelerating at the same time, it spins the inside rear tire. I have tried an Eaton TrueTrac (Torsen style) and now run a Variloc (clutch style) diff but they both spin the tire. The balance of the car is amazing and I have to be careful I don't make it understeery. I have SLA suspension in front and live axle with 3 link and Panhard out back. I wonder if longer travel shocks out back might keep tires planted. Any suggestions on how to solve this problem? Pictures of the car

http://img.photobucket.com/albums/v701/loosecannon/MGB-GT/IMG_9891_zpszq47jv8e.jpg (http://smg.photobucket.com/user/loosecannon/media/MGB-GT/IMG_9891_zpszq47jv8e.jpg.html)

http://img.photobucket.com/albums/v701/loosecannon/MGB-GT/IMG_7165_zps98es9sce.jpg (http://smg.photobucket.com/user/loosecannon/media/MGB-GT/IMG_7165_zps98es9sce.jpg.html)

http://img.photobucket.com/albums/v701/loosecannon/MGB-GT/DSC_5883_zpsuvusygvd.jpg (http://smg.photobucket.com/user/loosecannon/media/MGB-GT/DSC_5883_zpsuvusygvd.jpg.html)

[andrewb70]

I am by far not an expert, but if the shock is too short and is bottoming out on rebound, then that would definitely cause the inside tire to spin.

Andrew

[Che70velle]

I was going to say the same thing as Andrew said, but to add as well, are you running a rear sway Bar? I don't see one in the pics. Have you considered a spool?

[marksawatsky]

I was going to say the same thing as Andrew said, but to add as well, are you running a rear sway Bar? I don't see one in the pics. Have you considered a spool?

I am consulting with Ron Sutton on the suspension but I suspect that getting 7" of rear suspension travel instead of the current 5" (3" compression, 2" droop) will solve the problem. I don't run a rear sway bar any more, balance is adjusted with roll center.

[raustinss]

Tony from ABC Performance has a "toed" and "cambered" rear end ,which if I recall he said it helped him drive out of the corners putting down the power. But ....again I'm also not a expert by any means

[GregWeld]

I am consulting with Ron Sutton on the suspension but I suspect that getting 7" of rear suspension travel instead of the current 5" (3" compression, 2" droop) will solve the problem. I don't run a rear sway bar any more, balance is adjusted with roll center.



Smart move.

[marksawatsky]

I talked with Ron Sutton today and he told me to send him the Performance Trends file for my car. Before doing that, I double and triple checked all the numbers and added a few that I didn't have yet. I discovered that my front roll center was 2.5", not 3.5" and that my rear roll center was 14" and not the 10" I thought it was. Also, turns out I have zero caster, not the 6 degrees I thought I had. So, I think I know at least a couple of things Ron is going to tell me to change.

http://img.photobucket.com/albums/v701/loosecannon/MGB-GT/Sawatsky2017-12_zpstvjeckqh.jpg (http://smg.photobucket.com/user/loosecannon/media/MGB-GT/Sawatsky2017-12_zpstvjeckqh.jpg.html)

[WSSix]

So basically, you're rolling enough to lift the inside tire? A longer shock would allow the axle and thus wheel to press harder on the surface and not spin?

Cool car. Welcome to the site and good luck getting the car sorted.

[marksawatsky]

So basically, you're rolling enough to lift the inside tire? A longer shock would allow the axle and thus wheel to press harder on the surface and not spin?

Cool car. Welcome to the site and good luck getting the car sorted.

I believe that is happening, yes. There is a guy who has won my class at Nationals 12 years in a row and he leaves no stone unturned for performance. I built my car from scratch to the limit of the rules to win the class and now I just need the last little piece to unlock the speed. I hope Ron can help me with that and am prepared to put longer travel shocks in the back, if that's what he tells me to do.