How to tune out nose diving while jumping?

[WIKD 281]

Hello all:
While jumping a few weeks ago during my first short course race I found my car nose diving on every jump. It wasnt really bad but Im thinking if I could get the car to land level or rear first it might be an easier landing for the occupants and easier on moving components.
How can I adjust this out so the car will land level or rear wheels first? I tried to throttle thru the jump and also throttle hard right before the jump. I havent tried to brake at the base of the jump to compress the suspension. Is there any shock tuning I can work with to tune lift offs?
I am not running a spare tire right now but am working on a new lower spare tire mount.
Thanks for help !
Harold Fijman

[PAToyota]

More weight in the rear of the car seems an obvious solution.

[Brutpwr]

I would make sure your front spring rate is not too soft... for the most part if your vehicle is level thru most whoops it should ride fairly level on jumps. If your front spring rate is too soft it will be hard to get it to work well in all racing situations. I only have a lot of experience tuning front engine vehicles so not sure if this applies well to buggies but we do have a Class 9 car but we have never really had to change much on it compared to the Pro 2 truck.

Jason

[WIKD 281]

Thanks for the replies! Making a spare tire rack now and well see how it helps this weekend.

[450GRL]

In our experience, too much unsprung weight in the back actually makes the nose diving worse. I'd never race short course with a tire on the back - we don't even race with a fuel cell back there anymore......sounds like you need to adjust your rebound accordingly. When mine kicks, we slow it down. Spring rates come into play, too....so....would be good to get someone to watch you jump and help you tune your shocks.

Throttle control has a lot to do with it, too - sounds like you are working with that and trying different things. That's good. Sometimes it's a matter of how big/small the take-off is, too. If it's too small it will act like a "kicker".

[JeepRecoveryTeam]

Originally Posted by 450GRL

In our experience, too much unsprung weight in the back actually makes the nose diving worse. I'd never race short course with a tire on the back - we don't even race with a fuel cell back there anymore......sounds like you need to adjust your rebound accordingly. When mine kicks, we slow it down. Spring rates come into play, too....so....would be good to get someone to watch you jump and help you tune your shocks.

Throttle control has a lot to do with it, too - sounds like you are working with that and trying different things. That's good. Sometimes it's a matter of how big/small the take-off is, too. If it's too small it will act like a "kicker".

This...

More spring rate in the front...more rebound dampening in the rear.

The extra weight in the back can push you through the bump zone in the rear shock and cause the tire to compress... nothing worse than when suspension rebound is amplified by tire rebound

[WIKD 281]

Thanks for the replies! Really appreciate any advise/help we can get!
We added a lower mounted spare tire last week and raced on Saturday. It seemed like it helped out a lot with nose diving. We also shortened up our 3" hydraulic bumps to 2". Definately need more tuning time. Hope one day I can bring the car out just for that. Every jump we throttle thru untill we're airborn. During practice, twice we tried to not throttle thru and just hold speed up the jump and it nose dived big time.

[skife]

I don't have much expierence jumping truck, but when racing motocross if you wanted the rear end to come down in the air you just burped the throttle

[pontoontodd]

In the front, you want fairly stiff springs, one rule of thumb is that they will be so stiff that with no preload you'll have a decent ride height. Lots of compression damping and light rebound damping.
Opposite in the rear. You don't want the rear to bottom out going up the ramp but close. Hydraulic bump stops are the opposite of what you want in the rear because they will increase compression damping/springing but won't increase your rear rebound.
Videotaping your car from the side or with a camera mounted to the car pointed at the suspension will help, the best thing is to have an expert watch you run the car and make suggestions.