Help with traction problems...

[Indy Lonnie]

Ever since dyno tuning at ZZPerformance I have had traction issues. I know, such a problem... right... I want to step it up a little on the power side with a turbo and short block,, but it seems pointless if I can't get it to stick. I am currently running Bridgestone RE71R 255/40R17 in the back. I am willing to up the size on the rear but was wanting to see what others have done to help with traction. I am running Konig Dekagram 17x9 5X114 ET40 and would like to be able to use the same rim if possible. I run my Goblin on the street so keep that in mind. Autocross is upcoming with trips to the dragstrip.
First and second gear will break loose at any RPM, it still is clawing - but it is skating. Sometimes I have to get out of it several times to keep it from coming around. Third gear will break loose about half the time from 40-80 MPH. I honestly haven't experimented with forth gear much...

 

[TheNuker]

Do you know what you dynoed at? Did you have ZZP do the boost ramping in first/second gear?

Nuker-

 

[Ross]

Does your car have over steer? When I first set up my car, I put very soft springs in the back (125 lbs/inch) and with 315 tires, the car had a lot of under steer, and a lot of rear traction. Yes I could still break loose first and second, but it didn't spend much time spinning, it got out of the hole. Now I have it more neutral with 300 lbs/inch springs on the rear. The back end is a little more loose, but not bad.

 

[Indy Lonnie]

Do you know what you dynoed at? Did you have ZZP do the boost ramping in first/second gear?

Nuker-

I told Al at ZZPerformance to ramp first gear. I think my power #'s were 292 hp and 380 ft lbs torque at the wheels. The torque is all in at 3000 RPM. I really have not watched the boost gauge in first, I'm usually too busy and it goes by really fast. Second will hit 25 lbs - so no ramping... With that much torque, it goes hard in whatever gear its in.

 

[Indy Lonnie]

Does your car have over steer?

To tell the truth, I have not pushed the car much in corners. It will push for a moment and then grab. I have never really got the tires hot. So far, it has taken everything I have given it but I have not been on a track yet. I have the rear coil-overs with 300 lb QA1 springs that came with it, 400 lb springs in the front (stock DF).

This is the stuff I want/need to know. I have not optimized any of the suspension yet. Frankly, I don't know where to begin.

 

[ctuinstra]

How much pressure are you running in the tires? We are running the Toyo R1R and don't have any issues with traction (other than wet and cold).

 

[OptimizePrime]

Go Wide - You can fit a 285 tire on a 17x9 but best would probably be 275
Go Low - You could run 21psi
Get 'em hot

Should help, but it's likely to still be present to some degree until you modify the tune.

 

[George]

I run Toyo Proxies, not as much power as yours. Sipped the rear tires at 45 degree angle about 3/8" apart
It helped.
Brad

 

[Indy Lonnie]

How much pressure are you running in the tires? We are running the Toyo R1R and don't have any issues with traction (other than wet and cold).

I think they are at 18...

 

[George]

On the rear suspension, what if you leaned the strut forward 4 degrees how much anti squat would that add.
Anti squat should increase rear weight transfer.

Brad

 

[ccannx]

Are you running an LSD ?

I have been through a lot of springs so far and have done a complete 180 on what I originally thought would work for spring rates on the Goblin. George seems to have done the most with suspension so far.

You should see better rear traction with softer springs in the rear. I went from 500lbs rear to 400lb then 300,175. After more testing I plan to drop to 12” 150lb springs rear. I’m running a variable rate 140/250 front which is working very well but the front is scrapping during hard braking. I also have a massive front sway bar but one of the endlinks broke while testing. Moving to a smaller 3/4” bar to drop the wheel rate significantly in the near future.

I don’t think a sway bar in the rear is a good idea in this car. I ran an 87 mr2 that did not come with a rear sway but we added a tiny one and the car was nearly uncontrollable. I think the swaybar in the front should help transfer weight to the rear inside tire during turns but may create some understeer at the same time.

 

[TheNuker]

Did the soft springs make the rear feel wobbly in hard turning at speed?

Nuker-

 

[ccannx]

Solostorm data showed constant radius turn speed improved. Turn in while slowing into a corner still makes the backend light and twitchy depending on how much input is given which is good and bad. Hopefully longer travel springs with higher travel distance from static ride height will increase rear grip and the front swaybar won’t be needed at all for autocross.

 

[George]

If you do not have the rear strut adjusted correctly the shock will bottom out and make the car suddenly loose.
I found that out a 100mph. set the shock so it is in the middle of travel when setting static.

Brad

 

[Indy Lonnie]

Are you running an LSD ?

I do have a LSD.
As Soon as this COVID thing breaks, I plan to do some autocross. I have a friend who is one of the leaders for my area.
The only suspension settings I set are from recommendations on the forum. I have both the front and rear shocks set in the middle with recommended ride height in the back, slightly higher ride height in the front so I can get in and out of my driveway.

 

[Indy Lonnie]

Go Wide - You can fit a 285 tire on a 17x9 but best would probably be 275
Go Low - You could run 21psi
Get 'em hot

I can go with a 275 tire on my current 17" rear rims, but my fenders won't fit afterwards. I've been looking and if I need to change out tires I will go with a 315/30R18 with an 18" x 10.5"W ET18 rim that matches my front rim. I will need to get new rear fenders and widen them. The tire height will increase by just 0.5" - not enough to worry about. My only worry is how it will look with my front tires/rims. They are 205/50R15 with 15" x 8"W ET25. I love the stance right now and don't want it to look awkward. Got to have the right shoes...

 

[JBINTX]

I understand your concern about your "shoes". However, did you notice how the perspective changes the tire size appearance so drastically as you walk around the car? I looked at A LOT of the finished pics here on the forum before I purchased my tires and wheels. When you are standing at the rear corner like the pic you shared above, yes the rears look BIG. But from anywhere else, they fall into proportion.
Put what you think you need on there. They will look great!
Just my 2 cents......

 

[Indy Lonnie]

I understand your concern about your "shoes". However, did you notice how the perspective changes the tire size appearance so drastically as you walk around the car? I looked at A LOT of the finished pics here on the forum before I purchased my tires and wheels. When you are standing at the rear corner like the pic you shared above, yes the rears look BIG. But from anywhere else, they fall into proportion.
Put what you think you need on there. They will look great!
Just my 2 cents......

Image from the front side.
Thanks for you input...

 

[Ross]

Go wide....

Ross's extended city, easy entry Goblin- 06 SS/SC, NW Arkansas

Wow - nice write up on how the GM steering works. Looks like it can be changed in HP Tuners... I need to learn/pick a HP Tuners option... $800 or $500? Don't get your hopes up on HP Tuners helping you with the different maps. No such thing, at least not in my car.

dfkitcar.com

Ross's extended city, easy entry Goblin- 06 SS/SC, NW Arkansas

Assembled the front uprights today, with the new hub bearings, thicker rod end mounts. Torqued everything. Pressed out the old rear hub bearings. The aluminum had a reaction to the steel bearings, so they were stuck. The rear Moog wheel bearings arrived today. Test fitted them, and...

dfkitcar.com

Just my 2 cents.