maro z28

I understand solid rears are more suited to the hard launching of drag racing, but what advantages and/or disadvantes do IRS have vs. solid rear axles in autoX racing? Does the ability to do 4 wheel alignment help w/ negative camber gain during hard cornering? How do similarly powered Cobras and Vetts compare in autox to solid rear cars? Any info is greatly appreciated, thanks!

Z28SORR

It would probably be a good idea for you to buy a BOOK on race car handling.
As this is very complicated.
But anyway here's the short version. Picture your car in a hard lefthand corner. You've already down shifted and are accellerating out of the corner.
The highest forces are on the right rear. Now add some bumps or undulation, so that the right rear has to bounce up and down. As it does so the tire become unweighted and looses traction.
With a solid axle the up and down movement of the right rear will be transfered to the left rear. Causing both to become unweighted at the same time. This causes both a loss of forward traction and a loss of sideways grip. If the bumps a severe enough the rear end can slide sideways causing you to input steering correction at the least or spinning out at the worst.
With IRS there will be less transfer of motion and some off setting of time. In other words the left reacts slightly later. This allows at least one tire to remain in contact with the track and provide more forward motion and side grip.
End result is cars with IRS go though corners faster then solid axle cars.

maro z28

Cool. Know any books in particular that are good reads?

Z28SORR

Here's a place to start.: http://www.amazon.com/s/ref=nb_ss_gw...Go.x=9&Go.y=16
Check your local discount book stores. Usually have good deals.

maro z28

thank you!

dregsz

Herb Adams: Chassis Engineering
also check thier site at http://www.vsecobra.com/

Very interesting historica info on Pontiac TAs.
Herb developed hwat became the WS6 suspension package.
E

lincmarkv

And for clarification, generally a solid rear will go through a corner faster than an IRS car if the corner is smooth. Solid rear axles maintain consistent tire camber angles.

But most corners are not smooth...

dregsz

Solid Axles are favored at the drag strip. IRS has the advantage on the road course.
Forget the acadamic arguments, in reality, an equally powered, well set up vette will smoke an equally powered well set up F bod, by at least a half second per turn on most tracks.
That could be more then IRS though, shorter wheel base, lower center of gravity, stiffer chassis...

lincmarkv

Of course it's more than the IRS.

Mustangs with IRS are no faster around the road course (and in most cases slower) than the solid rear ones. Why?

dregsz

Because Mustangs Suck A$$

lincmarkv

Brilliant reply. Thanks for furthering the discussion.

KRS

I've heard that the Cobra's are prone to axel hop because of the IRS setup they run.I'm not sure how much of this will translate to going around corners though.But i'm sure if it's causing problems in a straight line putting power down than it will cause further problems putting power down around corners.

dregsz

Well, let's see...
Camaros w stock torque arms get axle hop when in the pre turn braking zone.
I've never had a problem getting power down accelerating out of a turn.
I thought the IRS cobras did really well as CMC/AI cars but I can't remember.