soft spring vs heavy spring on rf

[dirtman47]

I have an old grt 97. Before you guys laugh it actually was supposed to be a sportsman car but our track decided that four latemodels and four sportsman should be run together. So obvioiusly I am a disadvantage with a limited engine but i actually do ok with it for now. On to my question. I am currently on a 375# spring and a bump stop with 1" of free travel. I want to increase my bump to 1.75 " and soften my fr to 300. Im having trouble generating enough side bite in the middle of the corner and it has a throttle push from center off. The push is manageble but with a 602 crate engine i know i cant give up anything in and off. I tried moving my rru bar up one hole made the car turn out of the corner too much, did not help my middle. I also tried raising the j bar all the way up on the frame and all the way down on the pinion still no change other than car got tighter center and off or untill it could get hooked up again.

[MasterSbilt_Racer]

Lose the bump stop and gain speed based on your description.

[dirtman47]

Why loose the stop altogther? My understanding was that it helped get the car on the bars quicker.

[Egoracing]

What you are more than likely feeling is the car getting onto the bump and that adding LR drive and you are getting a push. Loosing it will make the RF more consistant thru it's range of motion and will not allow it to suddenly gain LR drive.

[MasterSbilt_Racer]

It is very difficult to get right if you don't have the correct bumpstop and knowledge of how to set it up. It won't really gain you much unless it is a momentum track. It is a real pain on a bumpy track. If you just toss a bumpstop on a car, it will act very much the way you describe.

I am just trying to keep you from chasing your tail. I wouldn't go down that road unless you have the ear of someone who knows how to do it. And honestly, I am not that guy.

[dirtman47]

Thanks for the info guys. I do have someone helping me that runs these types of cars on a regular basis but one can never have enogh information. I like to have the theory behind the changes. I am not a fan of monkey see monkey do.

[jedclampit]

Lose the bump stop! ....Lose the bump stop!!!!


Is the lr underslung of the frame notched out ?
Making sure the correct or appropriate components and updates on a older car can be critical to getting it to work well.
So this car is loose thru the center....and has a throttle push?

[hpmaster]

Lose the bump stop! ....Lose the bump stop!!!!


Is the lr underslung of the frame notched out ?
Making sure the correct or appropriate components and updates on a older car can be critical to getting it to work well.
So this car is loose thru the center....and has a throttle push?

Jed is right, there are a bunch of things that you can do to the older GRTs to make them work well.

[dirtman47]

The underslung is redesined on the left rear. It also has the updated bearing bird cages and updated front suspension components. The car works pretty good just needs some minor improvement! The guy that is helping me with it has rockets and trackstars. So I guess im the crash test dummy. BTW our track is fairly smooth and slicks up as the night goes on. I moved the battery to the right side this week and also changed the right front spring to a 300# but still have the bump stop. If i dont have improvement thyis week I will remove the stop next week. The car is really fast in the heats so I won't know if its improved untill the end of the night.

[dirtdiggerracing]

I agree lose the bump or if not just put more air gap in it and leave the 375 !! I think you are getting on the bump way to soon and it is putting all the load on the rf and the rr is not getting enough load to plant it for the side bite !!! Are you having trouble turning down in also ??

[Graff Spee]

Why not leave the bump stop alone and pull some bite out of it? That should let you run on the bump stop and help with side bite.

[dirtman47]

Update..... Against better advice we left the bumpstop in and lowered the spring from 375 to 300. We also increased the bumpto 1.5". The car was even tighter than before. It would get in good but as soon as i pickd the throttle up it would push straight off the track. If I waited for the c ar to turn It would get off ok but it seemed like i needed to be on the gas sooner. So now Im willing to listen my next plan of attack is to loose the bump and keep the 300 spring but i thin k it may be too soft.we did lenghten the bars on the right side really couldnt tell a difference. I will put them back. I had a 160 lbs of bite. I want to go down to the 100 lb range. Any advice is greatly appreciated.

[jedclampit]

If you want my help, pm me with all your info.

You need to get on a basic deal!!!


I (have) help a lot of racers thru here,some may chime in to attest to it. The first thing to do is get on a basic, baseline GRT deal ...appropriate for your car,track configuration,tires, engine and racing conditions.

[dualdj1]

Jed always comes highly recommended in the GRT world, would listen to what he says!

[dirtman47]

If you want my help, pm me with all your info.

You need to get on a basic deal!!!


I (have) help a lot of racers thru here,some may chime in to attest to it. The first thing to do is get on a basic, baseline GRT deal ...appropriate for your car,track configuration,tires, engine and racing conditions.

Tried sending a PM but says your box is full.

[jedclampit]

Usual Monday morning mail bomb!
Should be go to go now.
Thanks for the good word there dualdj1!

[Wheelman33]

Got to agree with jedclampit. A base line GRT set up should get you real close! Lose the bump stop and stay away from the dual stage rf until you are fast enough to run up front

[FlatTire]

"Im having trouble generating enough side bite in the middle of the corner and it has a throttle push from center off."

So are you getting clear out of the gas when you feel the rearend coming out from under you and then when you
pick the throttle back up you are tight? Does the track have even moisture from top to bottom? What kind of track conditions?

[jedclampit]

Jed always comes highly recommended in the GRT world, would listen to what he says!

Rocket is my bread and butter, but thanks again for the kind words!

[dualdj1]

Rocket is my bread and butter, but thanks again for the kind words!

np man, just always remember hearing your name when it comes to grt stuff.

[fastford]

the problem ive found with useing a bump stop or stacked spring on older chassis is the rt frt frame rail will hit the ground, the bump and stacked is the best setup out there right in my opinion, but your car has to be designed to use it because of the amount of rt frt dive needed to properly use it. if you only have an inch or so of travel you are not getting very much rear steer which will give you a heck of a throttle push, you would have to greatly dewedge the car or run so much static rear steer you would use up the whole track down the strait away, i agree with the others loose the bump stop and go back to original base line JMO