Cascade Crew

[scott in wa.]

So We did a little burnout yesterday, got about two hundred miles on the new gear set up.
How do we get rid of the wheel hop???
didn't notice it before with the 2:73 gears, but its there with the new 3:73's in.
thanks
scott

[izcain]

Aftermarket LCA's would be the first thing on the list along with an adjustable torque arm next. How do you like your 3.73 I remember a long time ago switching from 3.23 to 4.10 with my 305 motor and man that sure did WAKE UP that thing! lol

[scott in wa.]

Yep, big difference, feels allot quicker.
We have been driving the car on egg shells for the past 200 miles or so,
And last night we tried to light them up, but way to much hop.

Iam ordering some gr2 shocks and some new rear control arm bushing today, Might as well start with the basics first, Been reading on TGO, about rear suspension, I see that Dewey really know his stuff on this subject....He posted some really good drawings...

But Man we have allot of other problems, I guess that’s what you get for going to a 91 s/d harness in a 88 Tbi car. I am finding out what a hodge podge we have because of this.
At some point we may go to the Holley Commander stuff, and get rid of all the stock gages, (instrument panel is wired a little different). But money is a big issue with those upgrades. So we will continue to try and work out all the bugs with what we have now.

Thanks
Scott

[Dewey316]

Generaly wheel hop can be cured with better shocks. By definition, wheel hop is uncontrolled spring oscilations. The shocks function is to control the spring, and keep it from oscilating. Sometimes, adjusting some of the rear geometry (lca brackets) can help, but the real cure, is to get dampers that are up to controlling the springs.

[scott in wa.]

So by dampeners you mean shocks? Or is there something to add to the shocks?

[Dewey316]

Yeah, I mean shocks. I use the two interchangably. I can't stress it enough, and I am sure people hear this from me way to often. But shocks/struts are the best place in the suspension to spend your money. Our cars have pretty good suspension from the factory, but they didn't come with very good shocks from the factory, then add 10-20 years of wear on them. You can't go wrong upgrading to a good set of shocks and struts.

[scott in wa.]

so are these ok for now???
must be alot better than whats on there now.
http://store.summitracing.com/partdetail.asp?autofilter=1&part=KYB%2D343211&N=700+0&autoview=sku

[Dewey316]

[Xophertony]

i had wheel hop (not too much, just a ittle) on the GTA with it's stock shocks. i upgraded to the KYBs and it went away. but that is about the only difference i noticed. still bounces just as much over speed bumps, still feels exactly the same in every other way. overall i am not too happy with them. my next set will cost a bit more $$$. but you can't beat the price. i would say they are marginally better then stock shocks.

[QwkTrip]

I'm just guessing, but I suspect wheel hop is a problem with the frequency of input forces from the drivetrain being equal to the natural freqency of the suspension. The pulses of drivetrain forces have hit resonance with the suspension and everything is out of control. And it will stay that way until you change the throttle position or something breaks. The gear ratio swap has changed the frequency of pulses through the drivetrain and the suspension doesn't like it. And that's the same reason you didn't experience wheel hop with the original gears. The GM engineers made sure it didn't happen.

If that's true (and I don't know for sure but it sounds pretty good ), then the solution is to tune the suspension's natural frequency to a different level. It is adjusted by changing the weight of the car, geometry of the suspension, or the spring rate. Shocks have little effect. They can limit the amplitude of vibration, or severity of wheel hop, but the wheel hop will still be there. And the more power you add to your car the worse it will get. The extra power will just slam the suspsension harder and the problem will surface again.

So I agree with Dewey - Make sure your shocks are in good working order. But I have to really agree with Izcain - It's time to play with your suspension.... or gain a lot of weight. Whichever you think is more fun.

[Dewey316]

Jon,

Your looking too far into it. You should see dinner conversations with my family, way to many engineers. We can argue over the the way the turkey is being cut. or what the FOS on the dinner table is.

The wheel hop, is actualy caused by the suden influx of power, it causes the natural squat/anti-squat to start to move the suspension in the direction that the geometry dictates. As soon as you start to lose traction, that torqueing of the axle housing is gone, and it starts to migrate in the other direction. this cuases the spring to compress, and unload. As the amount of force the springs are pushing back on the axle changes, so does the grip level of the tires (rubber does funny things, it does not have a constant cf (coefecient of friction, for everyone but Jon. ). So your grab a little more traction, move the suspension just a hair more and so on.

Also, unless you are actualy keeping the car in one spot and doing a powerstand, and you start to gain and lose tractrion (this is happneing very fast, the frequency of the springs is high, so the oscillations and movements go very fast) you also have weight transfered for and aft, this all just compounds.

So, the key here, is to control the spring, or to stand on the gas, and just keep the tires spinning (they won't hop, if there is very near zero traction, because there is no toqueing of the rear end).

So, you could get way overboard, and try to get a zero anti-squate geometry, but that would be very hard, and the suspension is dynamic, so as soon as any one of many variables changes, you don't have a zero anti-squate. Or, you can have the shocks do what they are supposed to, and control the springs.

[QwkTrip]

That makes a lot of sense. I like your explanation better. In this case geometry and spring rate would have an effect too.

Now, you got me curious... what is an FOS?

[Twilightoptics]

Dewey hit it right on. With the lakewood 50/50 in the back and stock IROC springs I had NO wheel hop.

When I cut the springs down, creating a new higher spring rate... the shocks can't handle it and now I get wheel hop.

[Dewey316]

[rjmcgee]

[Twilightoptics]

BTW I went from a downward LCA angle to an upward LCA angle and it did not add or take away wheel hop. Compile this with all suspension in the back changed at one point with the springs/shocks remaining the same...... the only time I experianced wheel hop was the spring change.

I need to get some shocks on the back. I have way too much body roll back there too that I think I get some snap oversteer. Leans way over then just GOES.

Thinking about doing a panhard like the LCAs.


Koni or Tokico?

[Dewey316]

Koni's, they are by far the best.

[Twilightoptics]

Reds are non adjustable... yellows are adjustable.... and the orange ones that summit shows are?

[Dewey316]

Their discription lists them as "Koni Sports" which is the yellow for our car, the specials are the red, but I am guessing since the Orange part summit is showing, is only a rear, and the front one listed, is their SP1 drag strut, it probably goes with that.

FYI, when I looked shox.com had the best prices on this stuff, you might also try stranoparts.

You know, if you wanted to get crazy and start fabricating, we could build a pushrod setup, with Ohlins Coil-overs, mounted inside the engine compartment, and in the rear hatch. That would be crazy trick, or we could use the rear Ohlins bits from like a motorcycle, and then we could get parts for cheap.

[QwkTrip]

Okay, now I get it. And I have a new acronym to use at work.

There are a lot of people at CAT that do hard core design work but I'm not one of them. Frankly, I haven't done a single bit of hard core engineering since school. I'd be useless in design any more. And I lose another pound of knowledge every year.

To top that off I'm in an electronics engineering group and I'm not even an electrical engineer. My job is to manage projects for new technologies being developed by suppliers. You have to be technically competent but more so a good project manager.