Grt

[sgart35]

Got a 2011 GRT with wide Rf update that we run in an all steel engine, spec tire class that scales at 2400 lbs. The problem that we are having is that the car, when entering the corner seems as it is just "skating" across the top of the track. It has tons of body roll and is getting over on the right side but its like it doesn't have the side bite to help the car "hook" and therefore can't get into the throttle like everyone else is and they are just pulling us 4 or 5 lengths off the corner. The setup that we started with is a standard GRT setup as listed on their website. Any ideas would be greatly appreciated.
LF: 550 RF: 350
LR: 250 RR:225
Fifth: 325 @ 36"
Bite: 90-100lbs
Left: Around 55%
Rear: Around 54.2%
Shocks are IDAs by GW

[potts5]

600 lf 325_ 350 rf 250 rr 200 lr we have grt we won 15 race on these springs with 120 lr wedge 54.5 ls 55 %

[grt74]

you say skating but is this the whole corner ,entry to middle ,middle to exit,or middle only
reading what you posted it looks like your needing drive middle off,what I mean is you cant get in the throttle because it will spin out and not pull the car straight or to the right a little???
not being a wise guy but it will take a little more info

[grt74]

and also when you have a ton of body roll(excessive)is it really planting the right side tires ???you can have too much roll

[SS Motorsports]

My experience with GRT's with spec tires and steel engines has been they like more right front spring 425-450.

[RACR_73s]

SS - What do you suggest for a LF spring? I have a 500 LF and a 400 RF and I agree with what sgart35 is saying his car is doing as mine does the same. Although mine is a 2005 and has the shorter RF lower. ~Thanks~

[hpmaster]

My opinion is your LF spring is too heavy and stopping the weight from transfering to the RF. Go to a 375 LF and then move up 25 lbs. untill it skates again. Then you will have your high and lower LF spring weights. Then start working on the RF springs. JMHO.

[grt74]

if a car is skating the whole corner,here are some adjustments,leftside %,rr spring,rf spring (for added drive),rear%,on the lf spring you shouldn't need more than 550,if so the car needs to be set up with a tighter setup,we start with a 450 lf

[lcpestka]

550 lf 325_ 350 rf 250 rr 200 lr , 120 lr wedge 54.5 ls 55 % You have got to have a 250 RR spring, if you don't it won't go, prescribe to the skip arp way of thinking, put a 250 in the RR and leave it and don't ever change it. If you want to come off the corner hard just keep softening the LR spring. 200 is a good place to start.

[SS Motorsports]

We always ran a 525 lf.

[papier]

lcpestka and potts5,

Where did you guys run your 4 bars and j-bar with the 250RR spring?

[lcpestka]

Run the standard holes, top RR Bar should be about 18 too 19 degrees, and lower RR Bar should be uphill to the front about 2-3 degrees, Remember GRTs love wedge and to get side bite coming in you can soften the RF until it gets the side bite you need coming in. With a stiffer RR spring , such as a 250, when you change your LF spring up or down it will have more effect.
J-Bar 1/2 inch below pinion, and 8 1/2 inches higher than that on the frame. dont really use frame measurements, as your hight on your year of car and pinion plate could yield a different result.

[papier]

Thanks lcpestka.

[sgart35]

Thanks for all of the responses guys. I'm sorry it's taken so long for me to respond to this thread, got busy through the holiday season and it slipped my mind. But back to the topic, we had a race this past weekend and went a little harder on the right front than we were running but still had the same issue. It seems as though when entering the corner the car is good and actually plants the right side tires but with any application of the throttle, the car seems to want to over-rotate and doesn't have any drive off. Started off with bars in standard location and the rest of the setup was basically the same. Let me know if you guys have any more ideas. Thanks again.

[FlatTire]

I had about the same problem last summer and my chassis builder Kevin Shaw recommended I go to a stiffer RR spring as a previous poster mentioned as well. I was also getting a ton of body roll.

I had a 250 LR and 225 RR and the car wouldn't stay on the bottom on entry. The front end wanted to skate up a couple feet unless I got totally out of the gas and didn't try to push the issue. I Put a 250 RR spring on there and problem solved. That stiffer spring doesn't have to compress as far to equal the same force as the softer spring. F=kx. k is your sprint rate, F = your force, x is the distance traveled. You will also generate less body roll. The stiffer spring which produces more force becomes more effective helping keep the front end pointed to the infield.

[sgart35]

Ok, that explains it well. We have a couple practice days coming up so I'm going to take into account all things suggested and see what we can accomplish.

[Mantachie Missile]

There's a lot more questions that need to be answered before you can really determine the cause of your problem. You're saying its over rotating, where's your bar angles? Are you indexed anywhere? How much are you leading the lr? I agree there needs to be done spring changes but with the car over rotating on throttle it sounds like to much rear steer. Jmo

[lcpestka]

There is a happy medium in everything, on a GRT latemodel, based on where the spring is located from the wheel in comparison to a Rocket or Mastersbuilt is further away. GRT = 7.75 from the rotor to the center of the spring RR, on a Rocket it is 7.25. So eveything is a system and works together, if your RR isn't making enough sidebite on Cornner entry it won't trip the RF down and elevate the LR which in turn can cause a push in the center which seems to describe the situation of the original post. Remember also, that when you change bar angles you also change the spring rate cause it effects the motion ratio, pick your bar angles and stay with them, work the springs and shock and you will have way more sucess.

[grt74]

Thanks for all of the responses guys. I'm sorry it's taken so long for me to respond to this thread, got busy through the holiday season and it slipped my mind. But back to the topic, we had a race this past weekend and went a little harder on the right front than we were running but still had the same issue. It seems as though when entering the corner the car is good and actually plants the right side tires but with any application of the throttle, the car seems to want to over-rotate and doesn't have any drive off. Started off with bars in standard location and the rest of the setup was basically the same. Let me know if you guys have any more ideas. Thanks again.

2 things that come to mind,spring or rebound on the rf,dont worry about the # just keep adding spring rate until she pushes,or if you have a ton of rebound back it off some,good luck,hope this helped
when it does push just back up a little of what you have done