Now that the OPTIMA Ultimate Street Car Inviational is over we can give you more details about our Sonic setup. We tested so many combinations of coil springs we lost count. When we got close with coil rate we tuned with ride height. We wanted our Sonic to rotate in the turns based on speed or a trace of brake pedal pressure. The ideal coil combination turned out to be the 6kg coils that ship with the GMPP Xa coilover kit and rear 8kg160mm tall coils. Those stout and short rear coils were a bit tricky to fit. To get the ride height we had to remove the lower spring perch and locking ring from the spring jack with the coil sitting on the base of the spring jack. With the adjustable length monotube set as short as possible there was not sufficient trap on the coils. They were no so loose they would fall out, but they were loose enough to rattle and clatter. Race cars rattle and clatter so we were ready to go.
We measure ride heights Pedders style from the bottom of the wheel lip, up through the wheel center, to the painted edge of the fender. With 17" wheels the Pedders OUSCI Ready Sonic is 580mm front and rear.
Getting the dampening right is mission critical with the coil selection. Fortunately the range of adjustment in Pedders GMPP Xa Sonic coilovers is broad enough to optimize our setup. The front are set to 14 off full hard. The rears are set to 4 off full hard. We set the front toe to 0.00 and ran with a touch of negative camber -0.50. For the event, we removed the rear seat and all the storage area materials right down to the spare tire and jack. We did want to run Carbotech XP8 front pads, but they were not ready for the event. We tried to get Hawk DTC 60 front pads, but they were storm delayed. In the end, we ran the OE pads that had been on the car for 17K. Just in case, we did have new OE pads with us.
The Bridgestone S04 Pole Positions performed well. John felt they had a two step feedback. Step one let you know you were well into the tire. If you stopped there you would say they were good tires. John didn't stop there. The second step is a wide one. There is plenty of grip in that second step. We would have loved to have run our favorite tire the RE-11, but OUSCI rules preclude running a 180 Tread Wear Tire. Within the context of the rules the S04 Pole Positions were a great tire choice. We ran 32 pounds up front and 36 pounds in the rear.
Our Sonic is not the more radical build I originally envisioned. What we wanted to prove with the Sonic is just how good the car is off the showroom floor and how good it can be with minimal modifications. Our Advanced Racing Dynamics tune doesn't lean hard on the motor. It does just enough to compensate for he automatic transmission in these types of events. Could we have gone a more aggressive route, of course. Would we expect the same reliability found in a factory car? The answer would be no. In our opinion, what we have done to the Sonic should have no impact on reliability or the life of the engine and driveline. Adding bigger brakes and wheels would have been cool, but our goal was to prove a point. It didn't start out that way, but when we looked at the engine reliability at high HP levels we opted for reliability. The first rule of racing is before you finish first, first you have to finish.
Our Sonic's results were impressive. At the OUSCI we consistently saw steady state 1.08 Gs in the turns. We placed 23 out of 56 bad fast American Muscle Cars that were specifically built for the OUSCI autocross. Looking at the imports, we blew by the 400 HP VW, Fiat 500 Abarth and in the Speed Stop Challenge bested a 1,400 HP Lamborghini! In a competition like this, fractions of a second matter. The brake pads would have helped in the speed stop and autocross. The Spring Mountain Road Course is fast. Where the big dogs were running over 140 MPH our Sonic was running 88 MPH. We were able to carry our momentum through the turns better than most, but it was not enough to over come the acceleration advantage of the incredible cars we competed with. Overall, the Sonic proved to be exactly what we thought it would be. The Sonic is hands down the best bang-for-the-buck combination grocery getter / race car available.
Now you know how to build an amazing and reliable Sonic.
I'm installing my coilovers on Sat. I could use your expertise. I'm gonna max the rear. I already cut the sleeves and removed one jam nut. My question is for the front.
I'm installing my coilovers on Sat. I could use your expertise. I'm gonna max the rear. I already cut the sleeves and removed one jam nut. My question is for the front.
Height adjustment is so easy on the Sonic install it as is out of the box. After all the practice for the OPTIMA I can set the Sonic on jack stands, use my electric impact for wheel lug nuts and the rear lower shock bolts, and adjust all four corners in 15 or twenty minutes
On a sedan you will need to bottom the front coilovers if you want to match the rear in your configuration (1 jam nut removed). I can't speak for the hatch but like Pete said, it's very easy to adjust.
The ideal coil combination turned out to be the 6kg coils that ship with the GMPP Xa coilover kit and rear 8kg160mm tall coils. Those stout and short rear coils were a bit tricky to fit....
Getting the dampening right is mission critical with the coil selection. Fortunately the range of adjustment in Pedders GMPP Xa Sonic coilovers is broad enough to optimize our setup. The front are set to 14 off full hard. The rears are set to 4 off full hard...
You had to use stiff coils and a very high damping setting on the rear to reduce roll and eliminate understeer (helping the car rotate in corners). This would be very uncomfortable on a road car. We need a rear anti-sway bar so we can retain the softer ride and get the same turn-in.
I'm begging now... Somebody send me a rear sway bar. :sadbanana:
Hmm. I can't remember if I used them on disassembly or not. I think I removed the strut top bolts with the car on the ground then lifted the car to decompress them.
You had to use stiff coils and a very high damping setting on the rear to reduce roll and eliminate understeer (helping the car rotate in corners). This would be very uncomfortable on a road car. We need a rear anti-sway bar so we can retain the softer ride and get the same turn-in.
I'm begging now... Somebody send me a rear sway bar. :sadbanana:
A set of 6kg rear coils with the damping set to mid point front and rear delivers a very well balance car with no bars. On track, we ran the 8s in the rear at almost full hard. That would be too much for the street.
When I tracked mine I ran +12 clicks on the front and +16 rear i beleive... It worked excellant and rotated nicely...faster than alot of cars on the track. The wider less profile hankook ventus v12s make a huge difference in handling as well.
Then I could use an upgrade over the 3kg rears that come in the xA kit. The extra weight in the rear of my sedan makes it squat, roll, and understeer more than what I'm used to.
