rearend preload

I recently had a new rearend housing install in a blown alcohol funnycar , the car now seems to pull to the right . The rearend was installed straight up , someone has suggested that it should be angled 2 degrees downward toward the right rear tire for preload is this correct? wondering what to do?

 

depending on the angle of the drive shaft and what kind of rod ends are used a 0 degree pinion angle is not un common some times, alot of people automatically say 2 degrees but this is not always where it should be, pinion angle and preload are two different things, if the car is going right it is probably that the left rear has more weight on it, shorten the right upper bar 1/4-1/2 a turn at a time and this should straighten it out, remember to mark things so You will have a benchmark if this get to far out of whack. call me if you need any help. 405-923-6762 Mike. Henson Racing Engines.

 

Not sure about mounting the rear at a angle but on a solid suspension car the rear tire pressure can be adjusted slightly to help steer the car.

 

tire roll out..check it.dave

 

Shorten the right upper bar? Wouldnt you want to lenthen the right upper bar to put more weight on the right rear tire?

 

Is the rear a sprung or solid mount? What type of front axle does the car have?

 

rear end preload

the car is a solid mount ,It is a 96 hadman chassis , as far as the pull its gradual and will go about 350 ft before having to get out of it or cross the center line.

 

Brain Fart, Yes !

 

I'm w/Dave on this...CHECK ROLLOUT! Had this problem right after NEW tires were installed! Do NOT "assume" they did it right!

 

Will,
I do not want to hitchhike on another thread but I have a similar problem; the chassis is tweaked (solid FC chassis) from what the scales are telling me. I think this problem is worse at launch because of motor torque. I had two ideas to solve the problem.

1. Dual wheel wheelie bar- This could prevent the chassis twist on launch from transferring unequal weight to the rear tires. I think my single wheel bar works like a rudder when the front wheels are off the ground.

2. Strange adjustable spindles- I could square up car wheel weights with spindles and maybe preload the chassis to compensate for motor torque after some baseline tuning.

I have looked at sterring, tire roll out, etc with no luck.

The car does have a 6-inch wider track width than the normal funny car to accomodate an old nostalgia altered body I do not want to cut up. I think the wider track width aggrivates the problem.

your thoughs?

 

Insanity, get the adjustable spindles. Scale the car. Dual wheel wheelie bars could not influence chassis pitch rotation enough to successfully steer your car, anyway.

 

rear end preload

Will do. Thanks for your help.

Dave

 

Anytime, Dave. Have fun

 

Although these spindles are "the" choice for a chassis like this. Sounds like you should look deeper into what is wrong with it. The Strange spindles are not a bolt on and require cutting off all the existing spindle mounts. Re-engineering the steering (the steering arms come blank, and also are a different dimension from the spindle C/L). Brakes should you have them will need to be purchased separately from Strange also. And not to mention this will need to be done on some type of jig or fixture. If you are able to do this, it is the "right" choice for sure, but while you are at it you might want to fix what is "tweaked" while the chassis is on a surface plate or jig.
Just a few things that were not brought up.
Kurt

 

rear end pre-load

Kurt,
thanks for your feedback. I have seen the spindles on other cars but I have not looked at the details of the install. I am currently using Mark Williams spindles and steering arms and was hoping the king-pin inclination was the same so I could use the same A-arms and adjust to get the right crankshaft centerline. I noticed the same four bolt design as the MW spindles so I took for granted that the MW steering arms would fit. I have already replaced the motor plate and fixed some problems with chassis alingment (motor/rear end to chassis) but it is not enough. My percentage of rear weight on the right side is 46%. I scaled some other 125-inch FC solid chassis that seem to work very well and they are between 50%-51% on the right rear. The cross weight is even worse mine is 45.5% (right rear-left front) and the other cars are 50-52% cross.

I think this is the same reason that the person submitted the original thread since the rear-end preload would add weight to the right rear.

I think I need to get at least 50% of the rear weight on the right side and I need at least 50% cross (right rear- left front). I may be able to do this with putting the car back on the jig and making new A-arms but if I go through this hassle I may as well add some adjustablility to the chassis.

Your thoughts?

 

The King Pin Bosses are totally different as are the steering arms, as I said it would require a total front suspension re-do. There is a small amount you can change in ride height, but the biggest advantage is pre-load adjustability and a much stronger spindle with brake provisions. If all the components are centered, left to right weight should be close. Provided Tire Rollout, spindle and rear axle C/L's are the same height left to right. Chassis stiffness also comes into play as a softer chassis will be more forgiving in weight twist. As far as pre-load, whatever is done to one corner will affect the opposite, i.e. left front-right rear. So with pre-load set in front left "normal in an F/C chassis" will put weight on right rear, the front L-R weight will always be different. Weight in percentages are normally front to back, not across. Setting up a Funny Car-Altered Chassis is simply based on Engine Location (out from rear) and Height, also where any components are located off center for advantage of weight distribution. And then of course a certain amount of pre-load on the right rear.
Don't know if this helps, but they are all things that should be looked at. If your chassis is twisted that bad, you may need to do more than spindles.