Haggard-hawk

[rentedmule]

It was pretty shocking racing my bone stock 2010 Grand Sport after getting out of the significantly modified Formula. The vette was on junk tires and I'd barely driven it and my times were as fast or faster than they were in the bird on new 315 AR1's. I'm not getting rid of the bird, but there's something to be said for starting with a better platform...

[Catmaigne]

It was pretty shocking racing my bone stock 2010 Grand Sport after getting out of the significantly modified Formula. The vette was on junk tires and I'd barely driven it and my times were as fast or faster than they were in the bird on new 315 AR1's. I'm not getting rid of the bird, but there's something to be said for starting with a better platform...

True, and those platforms are certainly more confidence inspiring right out of the box, but that's reflected in the upfront cost. I do have a couple more avenues to explore before moving on and most of them center around getting more confidence/grip out of the rear of the car.

-Lower roll center in the rear with stiffer springs for less lift under braking, but similar roll stiffness
-Watts link for less mid-corner disruptions
-Mild aero up front to neutralize any lift that might be happening
-Decoupled TA (if I can find one?) to use the live axle to its advantage by having more antisquat on corner exit

If I can't shit on a competent driver in an SS1LE with all that and good tires, then it's vette time lol.

Also, I built the spoiler after seeing this vid. This is the same guy who set the f-body nurburgring record all those years ago. Interesting that slapping a spoiler on the bird made it more planted on corner exit than his C5z.

[rentedmule]

I've watched that guy's ring videos many, many times - so much fun.

I bet the Watts would help a lot. Mine is still laying on a bench. I had the best intentions of getting it in for this season but no luck. From your videos, it doesn't look like you're struggling for control on corners but maybe it would just smooth things out to give you more speed?

I find one of the biggest differences with the vette is the ability to put down power, even from a dead stop. I know a lot of that is a well-tuned IRS, but I never felt the Formula launched or pulled out of a corner like it should with huge r-compounds. Are you running drop LCA brackets in the rear? I have some sitting on the bench beside the Watts link...

[Catmaigne]

I've watched that guy's ring videos many, many times - so much fun.

I bet the Watts would help a lot. Mine is still laying on a bench. I had the best intentions of getting it in for this season but no luck. From your videos, it doesn't look like you're struggling for control on corners but maybe it would just smooth things out to give you more speed?

I find one of the biggest differences with the vette is the ability to put down power, even from a dead stop. I know a lot of that is a well-tuned IRS, but I never felt the Formula launched or pulled out of a corner like it should with huge r-compounds. Are you running drop LCA brackets in the rear? I have some sitting on the bench beside the Watts link...

So I remember the ring guy renting a e92 M3 on tire at the end of his stay in Germany and running within a couple seconds of his Firebird. The chassis can't be that bad lol.

I don't think the watts is going to help me at all with mid-corner grip, but it should certainly prevent the car from getting upset during transitions (due to lowering the rear RC) and over quick transients (due geometry/range of motion). I think the former will have a larger affect on lap times than the latter, but the watts kills 2 birds with 1 stone compared to a lowered panhard setup.

I never found that I had issues with putting down power in the car except for when the posi was dying or when the LCAs were sticking. Actually quite the opposite, I've always felt like the car squats like a drag car and rockets out of corners wayyyy sooner than I think it can. The rear is somewhat softly sprung so the sensation is a little unsettling at higher speeds because there is so much motion, but it usually works out. No LCA relocation brackets or anything and my TA is stock length.

My biggest gripe with the current setup is that it has always felt super loose and unsettled at the rear during hard braking/corner entry, almost as if the back of the car wants to do a stoppie like a motorcycle and rotate around. The soft springs are definitely contributing to the issue, but upping with spring rate in the rear without dropping the RC seems to make the car edgy and hard to recover once the rear lets go because of the added roll stiffness. I think the general balance of roll stiffness front/rear is good as-is, but the roll axis inclination from the rear RC being so much higher than the front means the rear end has to be floppy fore/aft to preserve roll balance. This arrangement was intentional by GM in order to get better ride quality out of a live axle car, but it completely screws me on the track, especially anywhere I'm required to brake/turn at the same time. The best example of this was T1 at Palmer where I couldn't dive into the corner nearly as deep or with as much speed as everyone else because there were too many overlapping elements.

[rentedmule]

I'm running BMR springs and they're softer than Stranos. I got them used/cheap before I had any intention of racing the car.

I think you described the characteristics of my car too - I'm probably just driving around that handling flaw but I trail-brake a lot to get it to rotate on the tight auto-X courses we run here. Between that and lift-off oversteer, I often end up drifting when I'm really pushing it.

Is that issue why so many of the FRRAX guys run crazy stiff (1000#) springs?

[Catmaigne]

I'm running BMR springs and they're softer than Stranos. I got them used/cheap before I had any intention of racing the car.

I think you described the characteristics of my car too - I'm probably just driving around that handling flaw but I trail-brake a lot to get it to rotate on the tight auto-X courses we run here. Between that and lift-off oversteer, I often end up drifting when I'm really pushing it.

Is that issue why so many of the FRRAX guys run crazy stiff (1000#) springs?

Do you know when the BMRs are from? I know they revised them at some point and basically made Strano knockoffs at 550/160lb (the SP001R set). I wouldn't be surprised if they were the same springs from the same factory with different marketing, but someone would need to measure the wire diameters and coil OD of each to be sure. The # of active coils looks identical.




I'm actually running the standard BMR 160lb rears but with Eibach 850lb fronts on my coilovers. Front rate may seem high, but the factory style shocks don't have a lot of travel before hitting their foam bumpstops which effectively makes the wheel rate progressive. Sam told me 800-850lb springs on a high travel coilover are similarly balanced to 550-600 on a stock style shock.

I also see a lot of different rates thrown around on FRRAX, but some of them are from 3rd gen people or those running slicks so it's apples to oranges.

Do you have the stock posi? I would get lift off oversteer when mine was dying or if I had way too much LSD additive in the diff. It would make the car step out during quick transitions while on throttle too. The sensation was really strange because you could feel the rear moving around and taking a wider line without the tires screeching like in a slide.

Also, how thick of a rear sway bar are you running? I am only running a 21mm solid 3rd gen bar and found that the "23mm" (actually 22.3mm or 7/8") solid Addco bar made the car very squirrely. It seems like the sway bar does more work to combat roll than the springs themselves on the rear at least. Just a change from 21mm to 22.3mm took the bar rate from 210lb/in to 260lb/in if these calculators are correct. The arms are 8.5" long and the center section is about 32" if I remember correctly.
https://www.gtsparkplugs.com/Sway-Bar-Calculator.html

[rentedmule]

I installed the BMRs in 2015 and I'm not sure how long before that they were purchased. I know the old version of them was in the ballpark of the Stranos, so it was never a priority to change them.

I'm running the non-adjustable Strano hollow sway bars 35 front and 22 rear with Koni yellows all around.

I do have the stock diff as far as I know, but I have no history on the first 170k kms of the car so it could be aftermarket. I had a shop change the fluid at some point when I installed the diff cover and they made a point to mention that it looked brand new. I think I'm ok on quick transitions and putting power down on sustained turns but I'll pay attention to that the next time I run it. It'll definitely spin both consistently on a launch.

Good info on the spring rates with/without bumpstops. In all the discussion I've seen on FRRAX, I don't think I've ever seen that mentioned.

[Catmaigne]

I had no idea about the stops until Mr. Strano was talking me into higher rate springs.

Before I bought the Ridetech fronts, I decided to cut open the dust cover on one of my Bilstein HDs while it was installed on the car with UMI lowering springs. There's maybe 1/2" of travel before the yellow shock body hits the orange foam stop with the car on level ground. The motion ratio allows the wheel to move a little more before contact, but the travel still sucks. The car rode 10000% better with the Ridetechs just because I wasn't hammering the hard foam stops all the time.

Screenshot_20230914_142407_Gallery.jpg

[rentedmule]

Interesting - I've always felt like the car was just too low to ride well but that probably explains it.

[JOATMON]

This reminded me that I have a set of Eibach springs NIB. They came with my Camaro when I bought it.
EIBACH PRO-KIT 3831.140 They are lowering springs I think about 1 1/2".
They can be had cheap, if any of ya'll are interested in them.
Nolan