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Author Topic:   Too tight on a Heavy Track!!!!
2 fast 4 you
Member
posted February 03, 2002 08:49 PM
I have a 2000 Larry Shaw Chassis with rear springs staggered. Left rear is in front of the axle, and the Right rear is in the back of the axle. My car is too tight on a heavy track. Would like to get some information on what people are doing the loosen these cars up. Left rear 175 lb. spring, Right rear 150 lb. spring. Rear shock are 94.


CUSTOMPERFORMANCE
Member
posted February 03, 2002 09:08 PM
too many variables without more info. you could change springs in rear and change cross weight and put both springs in front to name a few things to do . also whats your scale %?


2 fast 4 you
Member
posted February 03, 2002 09:19 PM
My left front spring is a 650, right front is a 750, rear % is 57%, left is 53.5%, diagonal is 49.7%


G17RACING
Member
posted February 05, 2002 09:43 AM
HOW MUCH BITE DO YOU HAVE IN THE CAR?
YOU COULD MOVE THE CENTERLINE(CL) OF THE CAR TO THE RIGHT BY CHANGING WHEEL OFFSETS, PUSH THE RR OUT, LR IN.

CUSTOMPERFORMANCE,
AM I RIGHT BY SAYING THAT?
DO YOU AGREE?


race8k
Member
posted February 05, 2002 11:17 AM
The first thing we need to knowis where the car is to tight.Is it tight getting into the corner, in the middle, or coming off.If you fix coner entry it may help exit if start fixing exit first it may hurt corner entry.More info.


2 fast 4 you
Member
posted February 05, 2002 06:45 PM
it is way to tight mid corner to corner exit


Roadhzrd
Member
posted February 05, 2002 09:41 PM
Try more stagger, more rear brake to get the car loosened up going in. Take some crossweight out. tuck in your lr and kick out your rr. You may even try to raise your rear ride height and move your lead higher or to the right to get it to roll over and give your car some side bite. Just a few ideas that have worked for me. You may try one of these or all of these ideas depending on how wet the track is or how bad the car is pushing. You might try the easier ones so you can put it back quicker when the track dries out. Hope I helped.


2 fast 4 you
Member
posted February 05, 2002 09:55 PM
if i stiffen the rihgt rear spring for the heat race will it work


CUSTOMPERFORMANCE
Member
posted February 05, 2002 10:33 PM
yes g17


tls88mod
Member
posted February 05, 2002 10:37 PM
I would move the front of the link arm on the right side up to the top hole on the frame and move the spring to the front side of the axle housing. If it is still a little tight put a stiffer spring RR.


2 fast 4 you
Member
posted February 05, 2002 10:48 PM
thanks 88 mod


wfoondirt
Member
posted February 06, 2002 08:21 AM
Moving the lr in and the rr out adds diagonal and left percentage. How does that loosen a car?


autoshop
Member
posted February 06, 2002 11:42 AM
wfoondirt, to my way of thinking, moving the tires to the right decreases lr weight, increases rr weight and takes wedge out of the car.

2 fast 4 u, whatever you do to loosen up the car, make sure you can easily undo it quickly. Sometimes you might have to do a quick turnaround between a heat race and feature. Changing a spring rate or mounting position isn't nearly as fast as changing wheel offsets or panard bar settings. Make it easy on yourself. I've got a 2001 Shaw with the rear springs on top of the rear end, so I'm not tempted to move the mounting points around. :-} I also change the rear brake bias (increase rear %) and turn on (increase) the rf brake to loosen it up on entry, which goes a long way to keeping it loose coming off. You can also raise the height of the panard bar to loosen exit (not the angle.)

Hope that helps.

wfoondirt
Member
posted February 06, 2002 03:46 PM
bkap, your backwards....the further in a tire is the more weight is put on it....try it on the scales


dawildchild56
Member
posted February 06, 2002 07:23 PM
2 words, wheel spacer. Try the stagger idea, set your RR out about 1/2inch to see what that does, it all depends on where your car is pushing, always rememer, RR gets you in to the turn, LR gets you out....


2 fast 4 you
Member
posted February 06, 2002 10:35 PM
bkap are you running the short or long pan hard bar on your shaw car


2 fast 4 you
Member
posted February 06, 2002 10:37 PM
what is the easiest way to raise the rear roll center


Sidebite
unregistered
posted February 07, 2002 08:22 AM           
bkap-
When you change offsets LR in and RR out, you are in effect moving the rear-end to the right. That has more effect on setup than the changes it makes to wedge because your track is now different compared to the front-end.

2 fast 4 you-
Raise your panhard bar to raise the roll center on the rear end.


bkap
Member
posted February 07, 2002 10:18 AM
2 fast 4 u - I'm running the long panard bar. You change rear roll center by changing the height of the panard bar, as sidebite said.

wfoondirt and sidebite - On further review ... you guys are right. I'm not sure what I was thinking. Thanks for the correction.

wfoondirt
Member
posted February 07, 2002 10:26 AM
All else remaining the same how does moving the rear track in reference to the front effect handling and why?


race8k
Member
posted February 07, 2002 12:07 PM
2 fast what have you got for wheel offsets ? What are your actual corner weights? Your cross looks kinda low to have a throttle push.
If you move the LR in and the RR out it will loosen the car on corner entry but it seems to also lose sidebite.

[This message has been edited by race8k (edited February 07, 2002).]

2 fast 4 you
Member
posted February 07, 2002 06:50 PM
i run the short panhard bar
i have 80 lb. of wedge
2 off all the way around and a 4 off bead lock


2 fast 4 you
Member
posted February 07, 2002 10:29 PM
WHEN YOU SAY RAISE THE ROLL CENTER ,YOU HAVE TO RAISE THE PAN HARD BAR, DOES THAT MEAN EVENLY AT BOTH ENDS


race8k
Member
posted February 08, 2002 07:46 AM
Try about 40# of lr bite this should loosen it up ? Just read on another ost that you run the short panhard bar.This setup builds a lot of lr on the gas so I would try dropping some lr.

[This message has been edited by race8k (edited February 08, 2002).]

Greggie
Member
posted February 08, 2002 08:41 AM
Just thought I'd talk about wheel offsets a minute... While offsets may affect weight distrib. to an extent, the biggest situation offsets are needed to tune is leverage on the centerline of the car. On the rear of a car the offset of a wheel will affect braking and acceleration, while the front will only affect braking characteristics. If you move a tire away from the centerline of the car, you are basically making it have more leverage on the centerline by making that "lever" have more length. Example: Move the LR out it will tighten under throttle and loosen under braking. The RR would be opposite. On the RF, we move it out on the slick to get the car into the corner more straight (this is really just to counteract the negative braking effect of the LR).

Then, when we get past these situations, we can deal with what offsets do to the way the shock & springs work.

If I were 2FAST, I would try moving RR out and LR in. Judging by what you said you were running, a 4in. lr and a 3in. rr would make a very significant change. There is also one other change that has not been discussed... Right side wheel base. Do you lead the RR wheel. This will also have a big effect on what the car does on the throttle. If you run like 108" wheelbase on right and, oh say, a 108.75 or 109" on left, I would try pulling the left rear wheel forward a half inch. If you do run a staggered wheelbase like that and you make both changes I have suggested at once, you may be a little loose. I would make both the wheelbase change and the offset change, but leave the 4" beadlock on the RR. I guarantee this thing will be much more driveable off the corner.

Greggie

Sidebite
unregistered
posted February 08, 2002 08:52 AM           
wfoondirt--
To demonstrate, ignore offsets for a minute and assume that you can move the rear-end left to right of car center. If the rear-end is moved to the right, the car will be loose and want to turn left if you release the steering wheel. By the same token, if the rear-end is left of center, the car will be tight and want to turn right if you release the steering wheel.

Think of a car that crab-walks or goes down the road sideways. The driver is constantly compensating for the condition and complains of the car 'pulling' one way or the other. Same thing here, just us racers use that as a tuning tool.

wfoondirt
Member
posted February 08, 2002 12:05 PM
Sidebite, typically the cause for "dogtracking" or "crabwalking" is the rearend isn't square to the front, not because it is offset one way or another but is good example of the effects of leading/trailing the rr.

Greg, i think i understand what your triing to say, but wouldn't the difference be most noticable in near steady state cornering (ie mid turn). The way i see it is the wheel offset changes the amount of weight transfer laterally during cornering. Under straight line accel/decel the wheel with the greatest weight gets the most grip and moving a wheel closer the the centerline of the car increases weight on that wheel. Thus moving the lr in will increase grip on that wheel and resulting in a tighter car on accel/decel.
Another result of moving the rr out/lr in is the change in wheel rates with the rr decreasing and lr increasing, which decreases roll resistance at the rear of the car which lends to looser cornering, because of weight transfer away from the lr tire resulting in less grip. This effect of loosening the car by moving lr in/rr out is pretty commonly accepted in the real world. My question is though is this truely a result of moving the track of the rear wheels or a result of the changes the wheel offsets has on the dynamics of the car. Hopefully someone can give me some new insight on this because everyway i look at it i come up with the same result.


bkap
Member
posted February 08, 2002 03:14 PM
2fast4you -- to raise the rear roll center, you would raise both ends of the panard bar equally. We raise the chassis end to increase sidebite and tighten the car on corner exit. We're still dialing in our Shaw and one of the first things we did was to lower the rear roll center because the car was too loose coming off. Lowering the bar (roll center) really helped. Now we're playing with the bar ANGLE in small increments. We've tried a half inch (on the frame end) so far and it really helped, although the track was really dry slick, then they watered it right before the main and it didn't completely dry out by the end. Even so, we were heartened enough try a greater angle (1") next time. On our Shaw we run 2 offs all around in the wet. We don't have a tight problem. For a dry slick, we're moving the rr in (2" bead lock to 3" or 4" beadlock) and the lr out (1/2" or 1" with a spacer.) This all seems to be helping although we've only run a few special shows and haven't begun our "regular" season yet where we can experiment from week to week.

Hope this helps.

CHAMP00
Member
posted February 08, 2002 09:32 PM
I would change the the rearend and roll the right rear back a litte and try that. would easy to change back. I dont think any has asked but is your wheelbase even? you might look there. CHAMP


2 fast 4 you
Member
posted February 10, 2002 10:01 PM
WE RACED TODAY, PUT A STIFFER R/R SPRING AND ADDED A 1/2 INCH SPACED ON THE R/R WHEEL. AT MAIN EVENT SWITCHED SPRING BACK,SEEMED TO LOOSEN IT REAL GOOD FOR HEAT RACE /////THANKS


neverenoughbrew
Member
posted February 13, 2002 06:22 PM
If you would like further info e-mail me, this discussion is is too full and half mistaken and would take too much time to respond to all inputs. There are correct answers if you read between the lines. No offence to anyone.