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nupeskee
02-08-2004, 09:50 PM
This is a major problem in my opinion. So far one person on this board with V has reported this issue and I plan to track this on the other V boards as well Caddy built a performance car and there is no reason on earth why we should have to "ease" out of the hole to prevent this from happening. I can guarentee that BMW, Audi, and Mercedes don't have this issue on their equivilent models. This is unacceptable and is really giving me second thoughts about getting this car.

JohnG
02-08-2004, 10:48 PM
I wouldn't worry about it unless you wanted to drag race the car, or really had your heart set on doing smokey burnouts.

If a car has axle hop, it only occurs when you spin the tires A LOT from a stop. i.e. rev it to 2500-4000 rpm, put it in gear, and move your foot to the side letting the clutch pedal pop back up.
Drag race start, or the kind of start you would do if you wanted to light them up and make a smoke show.

The rapid spinning of the tires causes them to hop, because there is not enough force on them to keep them on the ground. Cars like Camaro's and Mustangs have suspension setups to keep the wheels on the ground in situations like this, because drag racing and burnouts are a big thing those cars are meant for. Usually, this is accompanied by a big heavy live axle.

Cars like M5s, GS430s, E55s, and even Mustang Cobras (with IRS) do not have suspensions set up to prevent axle hop, because they are not designed with dragracing in mind. They all have axle hop to some degree. They use independent rear suspension, which is more suceptible to axle hop in such a start, but provides more sophistocated handling.

There is more to it than IRS v. Live Axle, but that's the 5 minute summary.

But basically, don't sweat it. You will be able to punch it in 1st in your CTS-V without a problem.

Dave
02-09-2004, 06:48 AM
Will bigger tires fix wheel hop? 245/35's are available on Tirerack - would they help?

nupeskee
02-09-2004, 11:49 AM
a more detailed discussion around the causes of this.

oceanhut
02-09-2004, 03:21 PM
Larger tires would help out this situation, I would think. However, 245/35 is not a larger tire, just a lower profile.
With an 18x8.5 rim, I would think you could squeeze into the backs, probably a 275/30 series. I would rather stay in the 40 series, but I dont know what the depth of the rear wheel well is.

reupreckt
02-09-2004, 05:59 PM
more as it would allow more spin. Axle hop is generally a function of too much traction for the suspension to keep the tire on the ground.

Many articles note 911's having serious axle hop on certain dragstrips.


<img src="http://members.roadfly.com/reupreckt/gt3.jpg" height=180 width=615>

oceanhut
02-09-2004, 07:58 PM
Interesting. I would not have guessed a smaller tire. Now, are we speaking "smaller" in terms of height, or "smaller" in terms of width?

RickKap
02-09-2004, 09:30 PM

reupreckt
02-09-2004, 11:37 PM
more flex which can increase traction (look at the hight of a dragster slick, and width puts more rubber on the ground. A taller tire would raise the effective gearing to the ground (i.e. torque) which could also have some effect.

Basically a full independent suspension is rarely the best for dragrace type launches. Likewise the 4-link dragrace suspensions corner like crap.

think of it this way. If you had a big eraser on one end of a pencil and you had to hold it at the other end while it was spinning at 1000 rpm, it would be difficult to hold the eraser down on the table. However if you had erasers on both ends and you could push down in the middle, you would probably have better luck. A very simple analogy for independent versus live axle suspension when traction is involved. You can do some things to either design to increase capabilities, but essentially the independent type is better suited to a car like the CSV.



<img src="http://members.roadfly.com/reupreckt/gt3.jpg" height=180 width=615>

Shaun
02-10-2004, 02:49 PM
I believe that more drastic measures have to be made in order to control the wheel hop. Since this is the most serious issue that the V has, I believe that the 05 will correct the problem, and hopefully we will be able to modify our rear linkage to a better system. If not, some type of after market traction bar set up will need to be installed, yet I doubt that one will be made since it will be a small market. I am not letting the wheel hop detract me from buying the car since even with slow launches, you will still have best in class times. Hopefully someone will be able to find the secret to non-wheel hop, cause hey, we all want to try a doughnut once right?!

msheri01
02-10-2004, 09:21 PM
Since most of the concerns are in northern areas, it might be interesting to consider that GM highly recommends snow tires for this vehicle in areas with significant snowfall. Goodyear, I believe, makes them for this vehicle.

Shaun
02-11-2004, 12:58 PM
how do you explain the magazine tests on dry smooth race tracks then? Snow tires will not solve the problem and slippery roads are not the problem.

JohnG
02-11-2004, 07:34 PM
adjusting the pinion angle (pointing it down a bit, towards the road). Also by installing traction bars/ladder bars - big pieces that attach to the axle and then run toward the front of the car, where they either attach to the leaf springs or to the chassis.

Another way is with a torque arm - attached to the middle of the axle housing, it runs up to the front of the car and is attached to the transmission (or to the chassis). It keeps the rear planted during burnouts.


On an IRS car, I'm not sure what you can do. Need some sort of suspension member that will apply a sufficient force to push the tire down on to the ground. That's what the traction bars/torque arms are doing on live axle cars.


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