UofMN

iTrader: (1)

I understand what IRS is, but I guess I don't understand why it is causing the wheel-hop everyone is complaining about. Are we looking at a trade-off between ride comfort and performance?
Do all independant rear suspensions suffer from wheel hop??

Just Curious

CSiJason

It is mostly the squishy bushings at joints between the differential housing and frame as well as soft suspension bushings and the rubber connector between the drive shaft and differential. Eliminate or reduce the problem at each flex point and you should reduce wheel hop significantly.

2edybrd

I've heard the IRS Cobras had wheel hop.

I put the SLP sway with poly bushings and end links and that cured 80% of the problem. We'll see what differential bushings do for the rest. After that shocks

CSiJason

I believe Energy Suspension has control arm and sway bar end link bushings in the works. Should be very good improvement over stock.

2edybrd

You should see how TINY the rear sway bar is. They say a torque converter is the first mod for an auto. I truly believe at least a 19mm rear sway should be the first mod for the GTO.

CHarris

iTrader: (5)

My 85 Corvette wheel hopped like crazy after I finally got up to the 350+ RWHP zone. Fortunately, I smoked the tranny so I never really had to deal with it. Since then I've gone way bigger on power and decided to go 9 inch and 4 link.

Cory

2edybrd

I'm still kind of a newbee when it comes to suspensions. On the rear for each wheel there is a thin almost tie rod looking kind of control arm that goes at an angle from the main suspension to the wheel. They both have bushings on either end.

Are these a type of "LCA" and if they are, being so narrow with rubber bushings; wouldn't that be a reason the wheels squirm enough for wheel hop? I mean replacing these with thicker pieces and poly bushings would keep the wheels from, I guess "toe"-ing in and out would be the best term?

stangman_nb

iTrader: (3)

I would definitely like to see a solid rear axle conversion become available for our cars at a resonable price.

2edybrd

I agree. I think the car would be a good drag racer with the conversion. I like the IRS though (had enough drag racers) I want to see how far this can go as a handler.

CHarris

iTrader: (5)

The IRS makes a nice street suspension that the vast majority of people are more than happy with. Once you step over and start road racing or drag racing all the problems become obvious fairly quickly. For the Drag guys it's wheel hop and breakage. For the road racer, it is handling issues and breakage. For the track day, fun lapping day guy these can all be dealt with in any IRS. Once the power goes big and lapping becomes true racing the cost of making the IRS get the job done makes the simplicity of a rear solid axle very appealing.

For instance, when I started taking the corvette lapping at the track I found that the rear camber bushings were allowing a lot of rear camber changer. I threw about $300 at that problem and installed camber rods with spherical bearings. Problem mostly solved. Solid rearaxles don't have camber change.

When I then decided to lower the car about 3 - 3.5 three inches overall it handled better in most respects but it picked up some wicked bump steer in the process. A solid axle rear wouldn't exhibit this. The problems with power-on toe out just suck on the C4 when you start putting the power down and then you have the maintenance issues. Solid axle has one drive shaft to break... IRS effectively has three. Solid rears have 2 u-joints... IRS has 6. The corvette IRS uses the two propshafts as upper suspension mounts. If you break one or lose the u-joint you have a nasty accident waiting for you. The C4 when tracked often and hard eats hubs. A worn hub introduces lots of handling issues and the possibilty of breakage. Big tires makes all this worse.

Ultimately, the IRS has very neglible superiority over the solid rear axle when a car is driven at the limit. Most people would not be able to obtain a difference in lap times between equally full out, no expenses spared, prepped cars. This makes the solid axle the better option for many racers because of its inherent strength and reliability. Look at the trans am series racers. They typically run 4 links and solid rears... even in the vettes (world challenge must use stock design). An IRS has far more parts and places that wear can occur making it more expensive to maintain and less predictable in my opinion.

Now changing the rear end to a totally different style is not for the faint of heart or mechanically challenged (trying to be pc here!). In these cases you go with BMR and those companies who make the stronger parts and let them work the bugs out.

While I'm more than willing to cut up the vette I won't do that to the GTO. I'll be going the mild BMR route eventually with this car and keeping it totally street worthy. I love how much more well mannered the IRS feels under normal usage.

Cory

2edybrd

I agree, the solid axle is great for handling, but you said it yourself, it really shines on smooth roads, like a track.

Or the southern states.

Smooth roads are few and far between for me. I remember many times I could the feel the rear of the Trans -Am start to skip across frost heaves and tractor trailer ripples and ruts. That kind of behavior makes you very nervous on the street when you're just trying to enjoy the car.

The IRS cars I have owned are much more stable and controllable on the street.
Well, I shouldn't really talk like an authority here. The only other IRS car I had was a Subaru SVX. HOWEVER... what a great car that was. I went to a '96 Trans Am from that and , frankly until I got used to the T/A, it's handling scared the begeezus out of me.

CSiJason

I'm coming from a Civic Si with a tweeked to the ***** suspension to the GTO and honestly I think the GTO feels great right out of the box. I also frequently drive a WRX which handles pretty well also. No complaints about the GTO considering the ride quality vs the WRX and Si.