So it seems A7’s are at least as fast as the Bias and radial slicks available for my CP project.
I can’t help but think that a 18x12 with a 335/30/18 on the front would be grippy and responsive and a 27x14x16 slick would help to put power down because of the width and extra sidewall
I’d like to hear any thoughts on the idea, on A7’s vs Bias or radial slicks and the mixing of the two
Do it!
But check your brake balance, especially in fast slaloms and hish speed sweepers.
I wouldn't be mixing tires. I tried a couple of variations on the idea when I was road racing and it always resulted in me spinning the car. I'd be curious to see if anyone here has successfully managed it.
I'd be a bit concerned about different rates of heating up. In my experience, slicks would likely take more time to get up to temp and would be a lot lower on traction until they are. The A7s would heat up quicker and not have as big a change in traction. I think if the handling balance of the car were setup for the final everything-hot state, it might be hard to get it there without spinning.
I've too have never had much luck with mixing tire technologies or even brands in road racing. With some adjusting I've been able to get the car sort of balanced for a short run but then it's out on a long run. I don't know what you're doing with the car but I've also had issues with A7s for road racing. They come up to temp quickly and have a bunch of grip but they wear ridiculously fast. Granted that's on a 3,400 lb car but still the R7s work much better on track in my experience. I would imagine that they'd be great for autocross.
The car will be a 2800lb CP 97’ Firebird
Engine is an L33 based 310ci
The slicks are cheap the wheels are really cheap but it seems like A7’s are faster
I might just say the heck with it and run a 335/345 setup with A7’s
In reply to APEowner :
I tried mixing Hoosier R6s with theequivalent Goodyears on a VW GTI. Earlier on a test day I had run identical times on four Hoosiers as I had on four Goodyears. They were allnominally the same size, but the Hoosiers were almost an inch wider. So, in an attempt to get the car to rotate better I put Hoosiers on the front and Goodyears on the rear . Took off from the pit lane on cold tires and spun between turns 1 & 2.. It rotated faster than I could react. They also would heat up at different rates, the Goodyears being slower. The Hoosiers would take less than a lap, Goodyears a couple of laps.
CPFirebird said:The car will be a 2800lb CP 97’ Firebird
Engine is an L33 based 310ci
Totally sidetracking here, but do you have specs on your build? I considered going that route for my CP build, but it didn't seem that cost effective.
I wouldn't mix tires either. I'm running Hoosier Radial Slicks on my car, but I think the A7s are as fast or faster on almost any surface. I'd go A7s all round just to make things easier and consistent.
DeadSkunk said:In reply to APEowner :
I tried mixing Hoosier R6s with theequivalent Goodyears on a VW GTI. Earlier on a test day I had run identical times on four Hoosiers as I had on four Goodyears. They were allnominally the same size, but the Hoosiers were almost an inch wider. So, in an attempt to get the car to rotate better I put Hoosiers on the front and Goodyears on the rear . Took off from the pit lane on cold tires and spun between turns 1 & 2.. It rotated faster than I could react. They also would heat up at different rates, the Goodyears being slower. The Hoosiers would take less than a lap, Goodyears a couple of laps.
Yup. There are so many part to a tire's characteristics that mixing them tends to add more problems than it fixes. That's not to say that it can't be done. We do it with circle track cars all the time. The difference there is that with only four corners(which are often treated as two really long ones) you can do weird things to optimize setup for a specific track that just don't work when you have to turn different directions and have corners with dramatically different speeds and characteristics. For a road racing I've found that changing more than just tire size front to back just complicates things and that there are better ways to fix balance issues.
In reply to Gimp :
It’s a 97’ Firebird that I can get under 2800 but would rather run 100lbs heavier to get closer to the 51% rear weight Bias
the motor is going to be a budget built 310ci
L33 block bored to stock LS6 bore, stock LS6 pistons, 4.8 crank/rods, 243 LS6 heads with welded chambers and CNC ported. Intake will be a TBSS intake.
should do a little over 400 to the wheels with an extended rev range.
I think it’ll be plenty of power
Looks like I’m going to run 18x12’s and 335/30/18 front and 18x13 with 345/35/18 rear
CPFirebird said:In reply to Gimp :
It’s a 97’ Firebird that I can get under 2800 but would rather run 100lbs heavier to get closer to the 51% rear weight Bias
the motor is going to be a budget built 310ci
L33 block bored to stock LS6 bore, stock LS6 pistons, 4.8 crank/rods, 243 LS6 heads with welded chambers and CNC ported. Intake will be a TBSS intake.
should do a little over 400 to the wheels with an extended rev range.
I think it’ll be plenty of power
Not to get off topic here ...but.
What's your valvetrain and lifter setup? Any pictures of the welded chambers? What are you planning on setting as your ceiling on the RPM?
Sorry for the million questions. I have a LS3 block/pistons, gen4 4.8 rods and 0823 heads I plan on doing a 4.8 crank detroker build with. I've been trying to figure out how to get the compression up without throwing a couple months salary at forged internals or shaving the heads down so much that the valves start kissing the pistons.
7500 rpm-ish
I honestly am very new to the LS series.
the cam/valvetrain setup will be whatever is recommended by whichever cam or can/heads specialty shop I choose.
ive been in contact with SPS, AI, and TEA on head porting. AI welds chambers on 317 heads to make them match the chamber volume of the stock 243’s
a stock LS6 piston and milled 243 heads is going to boost compression to 11+
i have more research to do because I think 13.1 would be possible with welded 243 chambers but that’s race fuel or E85 territory. E85 is definitely preferred because of the cost.
Valve/piston clearance will be an issue. I’ll cut reliefs if I have to. The cam will have to have a massive amount of lift to develop power in such a “small” package.
Not much help I know. Only thing I really have mostly sorted is the block, crank, rods and pistons.
I say mostly because the one year 5.7 GTO used floating pistons as did later 4.8’s so I’d like to use that combo.
The engine combo is something I’m still putting together and will be the last thing done.
For autocross run whichever tire heats up faster but run the same type and brand.
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