Quote:
Originally Posted by JusticePete
With your permission, I'll reply to both.
Wheel hop is a harmonic issue just like reverberation in a theater sound system. It starts out smalls, travels through the suspension until it explodes as wheel hop or axle tramp. Eliminating this requires the 'acoustic' be altered. Changing coils, dampers and bushes ALL alter harmonics. Contributing factors include tire compound and wheel alignment both change the way the tire connects to the road surface. That means changing rear wheel camber and the tire (stickier, wider, sidewall etc...). There is one more key factor -- the driver and we can't forget about RWHP.
So what is the short answer to wheel hop? Camber and sub-frame mounting. The less rear camber the better. The more square you can keep the tire to the pavement -- keep in mind when the car launches and squats the rear suspension negative rear wheel camber increases leading to the main tire contact being the inner edge of the tire with the outer edge barely touching -- the greater the potential for wheel hop.
Adjusting the rear camber to as close to wagon wheel straight as possible is a significant improvement created with a simple wheel alignment. It requires no parts. It has the side benefit of reducing understeer too. So step one is to square up the rear wheel to the pavement as much as possible through alignment. We do make a rear camber and toe bolt kit that doubles the OE range of adjustment, but the OEM bolts will allow you to get close.
A simple set of sub-frame insert will settle down the sub-frame motion you see in brand-x videos. The higher the RWHP the greater the need for a full sub-frame bush replacement until we get to the very hard Delrin for the street level of sub-frame bush. Adding more urethane to the rear IRS will continue to reduce overall compliance making the IRS more stable with each bush kit and incrementally reducing wheel hop. This would include replacing the differential bushes with a progressive voided set of bushes or moving to a much harder solid bush. Keep in mind, the harder the material the noisier they will be.
Finally we get to tires, gear ration and RWHP. My car simply shreds the tires. We are a true 530 at the rear wheels, with a gear change by wheel and tire size. The 305/30/19s put us at I think a 373. With a full Pedders suspension and the Bridgestone RE-11s it just rip the rubber off the tires and no wheel hop -- none. OE RWHP and SUV size wheel and tires are a real challenge. They limit slip and are efficient in that respect, but that is a HUGE wheel and tire combination to keep under control. The GM wheel hop update helps. Learning how to launch helps. The modifications listed above all help. It isn't a single solution. It is a combination of solutions.
Saving weight is always a good thing in a performance car. On the other hand, I am rather fond of the extensive durability testing OEMs do on things like control arms and curb impacts. The rose style joints that are incorporated into the rear control arms a a good example of excellence in GM engineering. Our car is pull 1.38 Gs on the track with street tires. That is great grip and I send my drivers out with all the confidence in the world that the arms will do what they are supposed to do.
A built in bias at Pedders i that our part should install just like the OEM bits. We try to avoid altering the structural integrity of the vehicle because we have so much respect for the OEM development process. We look at the OEM bit and try to see what we can do to enhance the performance without throwing the system out of balance. It is a fine line.
If anyone is still awake after reading this    |
we're not worthy!!! i just learned more about the C5 from reading your posts than i've learned in months of reading and weeks of owning one. i'll definitely be checking out your offerings.
and to get this back on the topic more specifically, although i own an SS, i can't wait for the Z/28 to come out. who knows, i may even buy one to keep my SS company. i think the two cars will be great stablemates and don't have to be mutually exclusive. and if i had the money, i'd probably buy a ZR1 as well. i'd prefer a Z/28 that's lightened and has improved performance, giving it back it's original first gen Z/28 feel.
i get the images from the "Italian Job" movie in my head where they modify the Minis to lighten them to be able to perform better. i know the components in my SS are top quality. everything has a solid, quality feel to it. in my mind, i can see replacing various covers and braces with lighter weight versions, saving hundreds of pounds, without doing anything radical at all. judicious use of carbon fiber bits here and there, thinner layers of damping materials in doors, panels, etc, and cross-drilled bits and parts for the stock SS running gear would help as well. then again, i'm not an automotive engineer, but it seems to work on performance versions of cars from Fiat Abarths to Ferraris...
anyway, i'm sorry if this has already been posted before, i didn't see this discussed in too much detail when reading this thread (i did skim some posts)... great discussion though.
last thought, i think Chevy should make the best possible Z/28 for a certain pricepoint. if it happens to kick other cars' butts, great. if not, it will still be one helluva fun car to drive.