sperkins

Not without physically adding or removing weight or sacrificing the LF corner weight.
You can jack on the spring bolts all day long, but you're never going to get 50/50 F/R or L/R.

drivinhard

Just a thought...I think the "magical" 50% cross is a bit overrated, or at least not optimal for all tracks/conditions. At the end of the day, you're trying to make the car behave the same way going left or right with a 50% number. But tracks don't have an equal amount of left and right corners, and you want the car really good on the really important corners (the ones that lead to long straights so that you can have the largest WOT on time as possible for that sector). My Road Atlanta set-up isn't anywhere near 50% cross. It's good in 12, 1, 7, and turning down into the esses. I can live with it being not quite as good for the two left handers (4 and 5).

I guess another way of saying that is test. Try it at your current setting. Swing it 1% and try again. Swing it 1% the other way and try again. See what works and what you like, and maximize your car in the important areas of the track.

redtopz

Thanks guys. That's what I figured. Funny thing is after all this work, I think I'm right back where I started with just using my fingers to check ride heights at each corner! I guess I'll see if it makes any difference at the track.

I went through the process because I just replaced my front spring perch bolts that had no padding on the pucks. They were metal to metal and were turning during the race especially on the LF. After a race, my LF ride height would be about 1/2" lower than when I started. I just took 2 old stock front height adjusters and trimmed down the rubber pads to about 1/2 the stock thickness. I'm hoping this along with a liberal dosage of blue loctite will prevent the ride heights from changing.

RX-Ben

Get the hardbar delrin pads, they slide better.

geerookie

Bringing this back up with a related but slightly different question.

My car has 3-way adjustable coil-overs and adjustable bars front and rear. The suspension was designed to work on bumpy NE tracks with good mechanical grip. I have a little bit of aero, about 500lbs total at 120mph.
The static numbers with equal ride height and no bars connected are:
50.1% Front
50.5% Left
49.9% Cross

I want to de-wedge the car (lower the cross) for a track with more banked high speed right hand turns (Watkins Glen).

Which works better and why, Preload on the front or rear bar or more preload on the springs?

sperkins

I would adjust the wedge (without pre-load on either of the bars) by raising the RR and/or lowering the RF, but my car has no aero. You can always tweak both fronts (or all 4) to achieve the same thing without messing up your ride height too much. Jacking the rear up in the air seems to help with mechanical grip on our skinny tire cars.

redtopz

Follow up on my corner balance: it definitely seemed to help the car handle better. It was slicing through the esses at Buttonwillow very well and felt nicely balanced.

However, lap times did not show an improvement because my ABS/AH warning lights started flashing Sat morning during warmups. A code scan showed EBCM malfunctions, steering, and wheel sensor codes. Nothing I did helped and the rear tires were locking up in braking zones even with no trail braking. It sucked. Based on some older threads I found on this site, it sounds like the dynamic rear proportioning system needs a functional abs to properly bias the rear brakes. I qualified and raced with it going easy on the brakes, but I had a massive spin off track trying to avoid another car and realized it probably wasn't very safe for me to continue like that. So I loaded up and headed to work Sunday am. That was the end of my T1 career.

RacePro Engineering

Wow! Where to start . . .

You gentlemen from Georgia must be really, Really, REALLY GOOD, to achieve great results by UNbalancing the car for road racing. I think you might be the only ones in the country who have found this secret. How does that work under hard braking? Hard acceleration?


And now this . . .

First of all, if your cross-weight (LR+RF) is 49.9%, then you already have a favorable "wedge" for TURN IN on right-hand turns. But jacking the weight to UNbalance the car on a road course carries major penalties, particularly with heavy, higher powered cars like the Corvette. So even if you are a good enough driver to take advantage of the slightly enhanced turn-in, you will give up stability in threshold braking on ALL corners, AND give up rear grip exiting those all-important fast right-handers.

Set the car up properly: Ride height, caster, camber, toe, bump-steer, and corner weights - all as symetrical as possible. (It sounds like your corner weights are fine as is.) Depending upon what the car tells you it needs (understeer, oversteer, and where), make adjustments at The Glen with your tire pressures, your anti-roll bars, and your dampers.

Ed

sperkins

De-wedging the car is done specifically to gain rear grip exiting those right handers.
Yeah I could see huge problems if you change the crossweights by several percentage points on an F1 car, but you have to remember that our cars are very softly sprung so these changes don't affect braking at all (or at least it doesn't for me)
.

geerookie

This is what I was thinking as well and I have the same result with my not so skinny tire car. I think adding it all in the rear works best because of the way the weight transfers with the soft springs.
I have also noticed I can play with how it "feels" by adjusting compression settings on my shocks or low speed damping. Basically it changes when the car takes a set and how early (and hard) I can get on the gas.

geerookie

First of all, Thank You for taking the time to jump back in on this thread.

I completely understand what you are saying here and (in theory) agree BUT my on track experience has been much different. I haven't specifically tested this at the Glen yet (end of the month).
By adjusting my cross between 47% - 49% I can get better out of right hand corner grip.
This is the reason for my question, theory and reality don't seem to agree,
so 1), I'm questioning my understanding of the theory and
2) wondering if I adjusted the wrong thing and dumb luck solved a problem I didn't know I had.

geerookie

So two things here:

Why would you choose springs over bars? What's the difference on how it effects the suspension.

And jacking the rear up in the air does "seem" to help mechanical grip but when you look at the camber curves it "should" hurt it! It would be nice to have a $10,000 full on Pi Research system hooked up to the suspension and a race track at our disposal for two or three days and never have to go to work and...............back to the world I live in.

Painrace

OK, guys, I admit I did not read all the post but here is my 2 cents.

When I was racing GT-1 we had a designated knowledgable suspension engineer with us. We started with the car neutral on all four corners with the driver in it (Very important for the driver to be in the car). Forget ride height except for rake. Adjust lead weights to get the car neutral. Then take the car to a track and record everything. Communicate with and listen too the suspension engineer and do what he says. Some times this takes a couple of days! You need a lot of sets of tires and plenty of fuel and maybe an extra engine and crew guys that are ready to do a lot of work! Driver must come in hot every time so tires can be punched. Roll out needs to be changed as the suspension engineer dictates (I always like the engineer to punch the tires).

The car will get very fast and the suspension will change a ton. When you leave the track you should have a very good record of what changed do. Now, you have a record for that track and those conditions only. Different temperatures, tires, etc. means you must make changes, every time!

When you go to the next track many, many changes must be made and you are not even close if you go from a right turn track to a left turn track or you go from a track like Roebling Road ( right turn track) to Charlotte Motor Speedway ( left turn track with banking).

After a while, you will have a record of what to do at each track and your crew can set the car up before you leve home to be close when you roll off the trailer. You will learn to guess at new tracks and get good at it.

Now, how can the weekend guy do this? You can only get close. Most don't have the time, money, sponsorship, car, crew, engineers, etc. to get a GT-2 car to run 1:18s at Road Atlanta. And, if you are like me, you will wreck and destroy a few cars so you need a couple of spare cars around and then you start all over.

WOW, I did not mean for this to be such a long post. I was able to set a few track records about 100 years ago with the above method. I was surprised to see that this year cars running the road course at Charlotte were lapping at times slower than my track record!

Good luck guys. Going fast is never easy and it is one hell of a lot of work. Good shops are hard to find that know suspensions but good suspensions are actually more important than HP within reason.

Life and going fast is not easy but that is what makes it fun!

Jim

RacePro Engineering

So . . . to be absolutely clear here . . . are you hoping for faster weight transfer ONTO the LR corner, or slower weight transfer? And why?

Thanks,
Ed

geerookie

To be honest I haven't even thought that far into it at this point.
I have always been under the understanding that 50% cross is where you want to be and then make tire pressure adjustments and shock adjustments at the track to deal with particular corners/problems.

BUT, I have recently started experimenting with a static cross in the 47% - 49% range since many tracks I run favor right hand turns and they tend to be the turns you can make up the most time in and/or they lead to fast long straights. As stated, this works and helps my lap times without the expected (theory) braking and big left turn issues.

My question isn't about whether to set my cross at xy% but rather IF I'm going to set it at 48% would it be better to do it with springs or bars and WHY?

And/Or what the difference in doing it one way or the other would be since the springs and bars affect the car in different ways at different times. e.g. springs affect straight line braking as well as turn in, mid corner etc. but bars should/would have no affect on straight line braking.

Basically I'm trying to decide
1) how much I'm going to dewedge the car before The Glen based on previous and expected results.

2)Whether I'm going to do it with springs or bars.

geerookie

Hi Jim,

I agree with the first part and if I had the time I would try to find the money to do that because it is the kind of thing I LOVE to do.

I'm stuck as a weekend guy right now and for the last two years been collecting basic data like lap times, sector times and "feel". I have now started experimenting with things I "think" should make a difference and recording some new data.

I 100% agree that Suspension and Brakes are more important than HP (within reason) to go fast. I'm still running a stock motor and working on suspension.
Until my data says my theoretical lap times are the same as my actual lap times and I can do it for 5 - 10 laps in a row I'm not going to add any HP.

RacePro Engineering

We always like to know what problem we are trying to solve, before solving it. Just a habit . . .
Ed

Painrace

I completely agree with your approach. Keep records and refer to them often. I can tell you I have been in on track incidents that knocked a lot of stuff out of wack and I went faster! But, most of the time unintended changes slow you up. All the best!

Jim

geerookie

I understand, as an Applications Engineer I always ask my customers what they think is broke or not working before trying to diagnose the situation.

In this case I'm not trying to "fix" something just trying to understand why things are or may be done a certain way in order to be better prepared for what may happen at the track.
Trying to toss around some ideas before testing but needing to have a better understanding of what to expect so I can better interpret the results at the track.

Are you going to the Glen Sept. 28th - 30th by any chance?

Murphy's Law ... For a race car to be quickest in all conditions it must be infinitely adjustable.

Corollary to Murphy's Law..If a race car is infinitely adjustable, there is a 100% chance that something is always in need of adjustment!
AND...
Nothing is so out of adjustment that $$$ cannot fix it

Painrace

And no matter how good you or your car are, you can out run everything but money!

Jim