To Flatout racing...racing the 355

No no no! The Hoosier "SGS" compound from last year, which is now this year's "GT" tire IS better than the Grand-Am Cup tire. While heavily based ON the Grand-Am Cup tire construction, it is a full slick, and performs better as such. The Grand-Am Cup tire looks, acts, and is to the best of my knowledge a *slightly* different version of an R3S03 (or whatever Hoosier's big R-Comp was at the time).

When we ran, this SGS tire was not yet available... It was still a prototype. We ran on Hoosier "GAC" R-Compound tires, complete with grooves/ "tread", and 40+psi operating pressures... It was interesting to say the least, but ultimately, we got the car pretty darn close to the times that the Challenge guys had run on Pirelli slicks. It was EVIL to drive, but certainly no 7-9 seconds...

-Jeff

 

Rob S.,

I understand that the Z06 is easier to drive fast, but do you think with two world class drivers the Z06 in T1 form is faster than the 355 (again in T1 form)?

Dave,

The GAC Hoosier that Jeff raced on is very close in performance to the old SO3's. I was buying used GAC Hoosiers for my BMW track car. From what I was told the CAG was simply a slightly harder compound than the Hoosiers you buy at Tirerack.

I can mirror what Jeff has said about running a Challenge car (355 not a 360) that is set up for Pirellis on the Hoosiers.

Evil is a good way to describe the feeling. The tires had a very "mushy" feel to them an on very fast high speed corners it felt like the sidewalls were being strained.

It speaks volumes for Jeff's ability to get within 2 seconds of the 360 C pole time (on slicks). I felt that my car was very unstable on the Hoosiers especially under braking.

Regards,

Jon

 

How do you define a "little"? I think if you put the car on scales you might not even be able to tell the difference in weight distribution from a change in ride height within reasonable limits. From a Grassroots Motorsports article on corner weighting:

There actually is an effect but it's so small as to be negligible in the calculations.

I completely believe your car is working better but it's not from weight distribution. If I had to guess (with my complete-amateur-beginner-suspension-guy hat on), what you're really feeling is the higher roll center in the front of the car from raising the suspension. The car understeers a little more and feels more comfortable coming into corners with the brakes on.

 

Bob,

Don't let the term club racing fool you. I know what you mean by the term. It's mean to describe low cost amateur racing (or at least low cost compared to ALMS or Grand Am). But that being said there are some world class drivers in SCCA and T1.

When I mean world class I am not referring to Senna or Schumacher. Remember there are plenty of pros who started (and still race) in club racing.

John Heinracy may have a day job at GM, but he is a world class driver. No one get's into a SWC Caddy and matches Ron Fellows lap times.

Bobby Archer (previous T1 big wig and SWC racer) was in my opinion and world class driver (though some may dispute this).

Michael Galati, Randy Pobst, and others raced in the same SCCA club racers we do and some still come back on a regular basis.

I think the top one or two finishers in most classes at the Run Offs have world class talent or darn near close.

Some have neither the budget nor the time to race professionally but do have the talent.

As in any race series (whether it be ALMS, Grand Am or SCCA at the Regional level) there will be people who truly have talent, people who don't but are very proficient through practice (I put myself in this category) and then those who will never be fast but are having fun (which is all that really counts at the SCCA level).

Don't sell the talent short in T1 at the National level. There are some great racers out there.

As far as which car made you comfortable I don't doubt the Zo6 made you faster. I think the car is the car to have in T1 because of that reason. You can learn more in that car in a faster time period than in a 360 or 355.

I think the Zo6 will be the weapon of choice for years to come in T1. The GT3 is a great car but costs twice as much and is still down on torque. The Viper is just too heavy and expensive (now 90K).

Regards,

Jon

 

With a little more thought, I can see why that could be so. Higher front roll center == less front weight transfer. Normally, this would mean more understeer. HOWEVER, the M3 has a strut suspension and probably not great camber curves. The camber advantage of not rolling as much outweighs the weight transfer effect. Another possibility is that your lower ride height was occaisionally kissing the bumpstops which really screws things up by increasing spring rates dramatically and unpredictibly.

Or something.


Separately, I agree with Rob. There is defintely serious overlap between top flight "club" racers and "pros". I know "club" guys who were beating current "pros" when they raced together but one put together the right program and the other never did. It certainly is a lot easier to get into the top series if you start with a strong checkbook.

 

Not true. Load transfer (weight transfer) in a corner is a function of track width and CG height, nothing more. Raising (or moving it in any direction) the roll center just changes the percent of load transferred to the tires/road via the spring/damper and via the suspension control arms/upright/hub, and of course, modifies the suspension geometry changes in bump and rebound relative to static ride height.

One will always have weight transfer. In fact, design the roll center high enough, and the car will camber into the corner looking like a bike, it’s been done, usually by mistake.

BTW, you’re correct in stating raising the front ride height does not place additional weight on the rear axle. And agreed, the improvement in cornering is due to geometry changes/ changes in how the driver sensing the chassis accelerations, changes to camber gain, etc.

 

I agree that overall weight transfer remains the same but relative roll centers affect how that transfer is distributed front to rear. Beyond that, the specifics get sketchy and the more I read, the more I see that I should just keep my mouth shut.