RCR gt 40 track test & chassis setup (results)

dlampe · #1 (**permalink**) 09-30-2007, 07:25 AM

RCR 33 track test & chassis setup

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The car has finally crossed over from the build to the tuning phase.

I spent the day at the track today so I thought I would write a little report. Before I get into the performance of the car let me share some basic chassis set up data for you. I weigh 205lbs and I had 12 gallons of fuel, 6 gals each side.

Ride height F 3 3/4 R4.5
Lower front A arm angle 3.5 deg.
Wheel weights Lf 650 Rf 589 Lr 763 Rr 715
Front% 45.6
Left % 52
Total 2717lbs

Springs front 550 Rear 375 lbs (wheel rate around 280 front and rear)
Ackerman 1deg toe out in 10 degs of turn

Toe F -1/16 (out) Rear 3/64
Camber F-1.9 R -1deg
Caster F 5.8 R5.6deg

bump steer left front bounce and droop
inch change
1 = 0.005
.75 = 0.002
.5 = 0.008
.25 = 0.002
0 = 0.000
-.25 = -.017
-.5 = -0.034
-.75 = -0.55
-1 = -0.07

bump steer right front
inch change
1 = -0.012
.75 = 0.001
.5 = 0.003
.25 = 0.005
0 = 0.000
-.25= -0.007
-.5 = -0.02
-.75 = -0.41
-1 = -0.052

These settings where achieve through a lot of chassis set up and a lot of trial and error.

To the track..........

This car drives so well that there is really no words to do it justice. I ran with a group of 75 Porsche's. I ran most of the day in Group 1 which is the advance group. I was consistently able to lap every car in the group over a 20 minute session. The car went where I turned and behaved very predictably. I was consistently faster than I had been the year before in my cobra. The car was tight with this setup and had a tendency to push in the corners although you could kick the rear end out with just a little pedal. I am going to take the rear springs up to 450 to loosen the car a little but I will also need to increase my front bar to correct a little boy roll issue. The goal is to net out a car that is a little less tight but not by much. I have a universal joint problem and the fuel pressure is running a little high for the Webers. I don't think I will make it back to the track tomorrow but today was a screaming success. For those of you just finishing your car, let me tell you that you will feel like a rock star when you go to this type of event. Everyone will want to come over and talk to you. People are fascinated by these cars. If anyone has any specific questions, just ask. I feel like I really bonded with the car today and let me say it again- There are no words to describe how well this car handles.

For those of you who wanted to reserve judgment on RCR until there were some on the track, Here you go.

gsharapa · #2 (**permalink**) 09-30-2007, 07:49 AM

Dean,

Where are the pics!!!!!! Glad to hear the car is working good..........

dlampe · #3 (**permalink**) 09-30-2007, 09:43 AM

I just added some pictures.

RedBarchetta · #4 (**permalink**) 09-30-2007, 09:57 AM

Quote:

Originally Posted by dlampe

...you will feel like a rock star...

Yeah, you're worshiped here, too.

Very nice car.

-Dean (the other one with a RED car, only mine is a distant second to your RCR)

BT SNAKE · #5 (**permalink**) 09-30-2007, 10:18 AM

Dean,
An exellent report that is very informative and I'm sure helpful to many.
I am wondering about the push you mentioned on the other forum. Is it
possible that this may be because your spring weight in the front is too heavy. I am surprised that the springs are heavier in the front than the rear. I know our cars are very different and you are a way better driver but I have 400 Lbs up front and 425Lbs in the rear. I have no push unless I force the issue.
I guess what I'm asking is why the Heavier springs up front?

Hersh

dlampe · #6 (**permalink**) 09-30-2007, 12:21 PM

Hersh, the springs aren't really relative by themselves. It is where they are mounted on the lower a-arm and at what angle along with the spring rate that will create wheel rate. I had my wheel rate set at 275-285 pounds per wheel. I could actually live with the little bit of push that I have but if I add a larger front sway bar to control the body roll, i will exaggerate the push so i will need to add more spring in the rear or a larger rear bar. I am looking forward to seeing you in a couple of weeks.

BT SNAKE · #7 (**permalink**) 09-30-2007, 01:09 PM

Thanks Dean,
I see what you mean. I look forward to seeing you and the others too. I
am so impressed with your car. Best of all you kept accurate records of your build and share the learned knowledge with others. It don't get any better than that. It can only help make this great event grow.

Hersh

BMK · #8 (**permalink**) 10-01-2007, 03:59 AM

BT SNAKE

Hersh,

Some good set up detail here. Looks like spirited competition coming up..

Have fun..

Naumoff · #9 (**permalink**) 10-01-2007, 04:21 AM

Great report Dean.

Looking forward to seeing the car in person at the RnG.

The wheel rate calculator that was linked to on the RnG forum was great.
My car is low but close all the way around so it will be interested how she does on the open track. I have to go back and enter the info but it was around 235-245 and I am running 3/4" swaybars front and back.

WildBill3 · #10 (**permalink**) 10-01-2007, 04:29 AM

your going to be a Rocket at runngun man im lookimg forward to see you and the GTR go at it,see ya ther,wrench wrench bang bang uh duct tape some pop rivets aahh done

...WB3

SwiftDB4 · #11 (**permalink**) 10-04-2007, 07:59 PM

Nice GT40! What size wheels and tires do you have? I have an SPF MkII on order and hear 295/50/15's are nearly extinct except possibly Avons.

dlampe · #12 (**permalink**) 10-04-2007, 08:06 PM

I am not sure about rim size i think they are 7.5 and 9.5. The tires are 295's and I think they are still pretty easy to get. The fronts are 205's but they could be bigger.

Naumoff · #13 (**permalink**) 10-05-2007, 05:33 PM

Dean,
I found my numbers for the wheel weight of my Cobra.
240# for the front and 230# for the rear.
What do you think? I guess we will find out next week.

gsharapa · #14 (**permalink**) 10-05-2007, 06:23 PM

Dean,

Thanks for the pics and report. Car looks awesome and from your description it appears you are going to have some real fun on the track in the near future. Hope you bring it to Tulsa next June?

Buzzmobile · #15 (**permalink**) 10-05-2007, 06:43 PM

take care of my next car....don't mess it up before I buy if from you. Smiles. Things much better on the home front. talk to you soon. my cobra will be outta the shop soon and I will be back in "life" quickly. see ya

Buzz

496fe · #16 (**permalink**) 10-05-2007, 07:05 PM

Just wondering... why don't you stiffen the bar in the rear, rather than the springs. It seems that the rear end is where you have room to work with the body roll. You are right - stiffening the front bar will cause more understeer, but stiffening the rear springs will cause more oversteer. My theory has always work with the end that is NOT working (front) and leave the end alone that IS working (rear). Body roll in and of itself is not necessarily a bad thing.

BTW - the GT40 is a real race car, not a converted sports car. (Incoming flames on the horizon).

Brian

Naumoff · #17 (**permalink**) 10-05-2007, 07:24 PM

Quote:

Originally Posted by 496fe

Just wondering... why don't you stiffen the bar in the rear, rather than the springs. It seems that the rear end is where you have room to work with the body roll. You are right - stiffening the front bar will cause more understeer, but stiffening the rear springs will cause more oversteer. My theory has always work with the end that is NOT working (front) and leave the end alone that IS working (rear). Body roll in and of itself is not necessarily a bad thing.

BTW - the GT40 is a real race car, not a converted sports car. (Incoming flames on the horizon).
Brian

...........For what?

496fe · #18 (**permalink**) 10-05-2007, 09:38 PM

Whenever anybody suggests that Cobras weren't real race cars, the fit hits the shan.

dlampe · #19 (**permalink**) 10-05-2007, 10:17 PM

Tony, your wheel rate are set up great for the road. For the track they need to be at least 275 and a little closer to 300 is better. You will be fine. The cool thing is at least your know. I have a lot of springs. Do you know what size you are running?

496fe, To fix the body roll the correct way would be to bump up the springs but that will mess up my balance as I have it set. I can raise the swaybar rate front and rear with the most gain in the rear and get pretty close. That is what I am going to try first. The car is already very close. When I get to the track I can test my tire temps and that will tell the whole story.

Gary, I plan on running in Tulsa next year for sure.

Buzz, glad to hear things are going better.

496fe · #20 (**permalink**) 10-05-2007, 10:26 PM

Quote:

Originally Posted by dlampe

496fe, To fix the body roll the correct way would be to bump up the springs but that will mess up my balance as I have it set. I can raise the swaybar rate front and rear with the most gain in the rear and get pretty close. That is what I am going to try first. The car is already very close. When I get to the track I can test my tire temps and that will tell the whole story.

Perfect

. You know what you're doing. No wonder you were blowing everyone else in the weeds.

Brian