Make it handle

[robnolimit]

Lots of thread postings lately discussing the mounting point of trailing arms. The hieght of the pivit mount determines the "rate of rise" or "anti-squat" transfered to the rear tires. There is some disussion on wheather to raise or lower the pivit point for better handling/traction... This also may effect pinion angle, So, lets have a look.
Pinion angle If you are working on a truck with an existing rear axle, (most are) and it is stock height, then the pinion angle is set to factory spec. If you lower the truck 4", the pinion angle will decrease appx 3 deg. Raising the front pivit point of the trailing arm 4" will restore the pinion angle to it's orig. spec. As a note, It would be ideal for the pinion to be parallel to the crank/trans center line.
Anti-Squat Is heigher better? - maybe. It's all a trade off. lets start with some basic driving info. If a car/truck has "Oversteer", then when you go through a turn, the front will turn in, and the rear may tend to get a bit loose and rotate out, loosing traction. The truck is turned MORE than the input from the steering, = "Oversteer", or "LOOSE". Now, if the car/truck has "Understeer", then, when you turn the wheels in, the truck will not respond as quickly. The rear has great traction, and "PUSHES" the front straight. In this instance, the truck turns LESS than the steering input. It has "UNDERSTEER", or a "PUSH". Somewhere in th middle is a balance. If we take the front suspension out of the equation for a moment, to see how the rear can effect steering, we could say this. - More traction = push. Less traction = Loose. more traction is better, right? Maybe not if your in a corner. If you aretrying to get through a corner at speed, and the front "pushes" you have no choice but to get off the throttle, on the brake, and slow down enough to get the truck to turn. This is the slow way around. If the truck is "loose", you can use the throttle to help steer through the corner, as long as your not to heavy footed.
So, back to production based Chevys. Most trucks push a lot if you drive them hard. The weight imbalance (nose heavy) tends to make then "push" into a corner, and get "loose" on the way out. Since it is easier to drive with a bit of a loose condition, and most of us are dealing with existing axle housings, I tend to recomend raising the pivit point. Now, if it was a truck mostly for drag/straight line fun, then I would leave it low, and use a wedge shim to fix the pinion angle. Some companies, like Hotchkis, have a front trailing arm mount with multiple mount points. Realisticaly, you would need to check the pinion angle at each setting to get a true comparison. Also, Horsepower comes into the discussion. As we add Hp, traction goes away, So it is fair to say that a truck with big Hp may benefit from a slightly lower pivit point. On our "Silver Bullit", we have moved the front many times. The goal is to have as much traction as we can get, up to the point that it has a push, then we back off a bit, keeping it just to the loose side.

[NPilot1975]

Rob, do your front trailing arm mounts (uniballs?) fit in the stock trailing arm brackets?
Posted via Mobile Device

[robnolimit]

Originally Posted by NPilot1975

Rob, do your front trailing arm mounts (uniballs?) fit in the stock trailing arm brackets?
Posted via Mobile Device

No, our 'Monster ball' adjusters use a 9/16" through bolt, and are 2 5/8" wide. If you thinking about building adjustable arms, you will need to fab new front mounts as well.

[Hotchkis]

Originally Posted by NPilot1975

Rob, do your front trailing arm mounts (uniballs?) fit in the stock trailing arm brackets?
Posted via Mobile Device

NPilot1975 – The trailing arm front brackets we offer work with the stock trailing arms and give 4 adjustment holes for tuning pinion angle and traction for improved handling.

Hotchkis Sport Suspension ULTIMATE C-10 Pickup...

[BMERDOC]

Whew, sat down for several hours, determined to read this entire thread! I started a thread on modernizing the basic alignment angles and now it looks like I may have to back pedal on a couple of things I thought to be true. Seeing some of the simple upgrades here looks like I'm gonna be busy! Thanks Rob for all the info, drawings and tips!

[robnolimit]

Originally Posted by BMERDOC

Whew, sat down for several hours, determined to read this entire thread! I started a thread on modernizing the basic alignment angles and now it looks like I may have to back pedal on a couple of things I thought to be true. Seeing some of the simple upgrades here looks like I'm gonna be busy! Thanks Rob for all the info, drawings and tips!

Hey Doc. I read over your alignment posting this morning. It got me thinking. I like the comment about toe out, keeping the front steering tight. While this is true, I never thought of it that way. I always used toe toe balance the acreman during initial turn in. Your concept/comment is right on. With slight toe out, the outside tire, the one you get all the feedback from, will never 'slack-up' while transitioning into the corner. Thanks for the great input. Keep it up.

[BMERDOC]

And your comments on Toe got me thinkin too. Thats what I meant when I said I needed to back pedal. Ive got to clean that section up.

I have some questions for you regarding the stock LCAs that were done in this thread and JT's thread. Uortunatley, I'm at work and only had time to take a peek.

[doublebeetx]

Hey Rob I have a question. I see that 2 inch blocks aren't recommended for a truck with 15 inch wheels, I assume because they push the arms too low. Would 4 inch springs and a 1 inch block have a similar effect as the 3 inch spring and 2 inch block ?

[tubbedII]

Originally Posted by doublebeetx

Hey Rob I have a question. I see that 2 inch blocks aren't recommended for a truck with 15 inch wheels, I assume because they push the arms too low. Would 4 inch springs and a 1 inch block have a similar effect as the 3 inch spring and 2 inch block ?

Yes to all...(Sorry I'm not Rob, but...)

[robnolimit]

Right you are TubedII. The scrub line gets pretty close when you have a 2" block with 15" wheels. Just remember that the shorter the spring is, the stiffer the truck will feel.

[tubbedII]

[QUOTE=robnolimit;4965404]Right you are TubedII.QUOTE]

I'm gonna print and frame this...

[robnolimit]

[quote=tubbedII;4965720]

Originally Posted by robnolimit

Right you are TubedII.QUOTE]

I'm gonna print and frame this...

thanks, lol

[doublebeetx]

What would be the ideal way then to lower 5 inches and stay with 15 inch wheels ie, best ride and handling ?

[robnolimit]

Originally Posted by doublebeetx

What would be the ideal way then to lower 5 inches and stay with 15 inch wheels ie, best ride and handling ?

I would probably do a 2" block, and 3" spring. But, I'd be risking it with the scrub line. So, is the risk worth the ride quality gain? (vs 1" block and 4" spring) hmm, not sure.

[lolife99]

Originally Posted by doublebeetx

What would be the ideal way then to lower 5 inches and stay with 15 inch wheels ie, best ride and handling ?

I would use a 5" drop spring.

[Greywolf200]

Greetings Rob, did you ever get any results for the raised upper ball joints?

Thanks

[robnolimit]

Originally Posted by Greywolf200

Greetings Rob, did you ever get any results for the raised upper ball joints?

Thanks

We're finally getting around to putting a set on the JT. It should change the camber gain from .86deg per inch, to 1.23deg per inch. We probably won't test until after SEMA. As a comparison, our wide rides have 1.56deg/in

[shawnr21]

Great thread!!!, I have some questions that I have not found the answers to yet. Maybe you guys can help. I have a 90 c1500 and would like to get some upper a arms to correct suspension geometry. Does anyone know of any, seems most parts are for the earlier models.

Rob, awesome thread. I would like to get one of your rear 4 bar kits for the same '90 model truck. I'm guessing I can adapt the kit you sell for earlier models to work with my truck. I was wondering how long the bars are that you sell? I recall you mentioning the longer bars or further pivot point is better.

Thanks!!!

[hotrod1]

ROB:

Assuming we are talking about using your 4 link fat bar setup:

I was wondering about rear coil over position. Can it be mounted behind the axle or in front of it, and what would it do to the handling if any? Tilt forward, backwards, further out, further in? How about cantilever like you have in your fat frame?

Any other options?

Thanks

[robnolimit]

Originally Posted by hotrod1

ROB:

Assuming we are talking about using your 4 link fat bar setup:

I was wondering about rear coil over position. Can it be mounted behind the axle or in front of it, and what would it do to the handling if any? Tilt forward, backwards, further out, further in? How about cantilever like you have in your fat frame?

Any other options?

Thanks

Hmm, let me find some info and picts to post up about cantilever or rocker arm mounting. This may be of interest.

[robnolimit]

Originally Posted by shawnr21

Great thread!!!, I have some questions that I have not found the answers to yet. Maybe you guys can help. I have a 90 c1500 and would like to get some upper a arms to correct suspension geometry. Does anyone know of any, seems most parts are for the earlier models.

Rob, awesome thread. I would like to get one of your rear 4 bar kits for the same '90 model truck. I'm guessing I can adapt the kit you sell for earlier models to work with my truck. I was wondering how long the bars are that you sell? I recall you mentioning the longer bars or further pivot point is better.

Thanks!!!

We really haven't got into the 88-98's yet, So, I really don't know of any arms that help. But I'll look around. Most of the parts out there are clones of factory arms, or adjusted for lowering, - not for any handling gains. Yes, you can use our FatBar kit, the bars are 30 1/4" eye-eye. The front mounts are slightly modified for that install and must be welded to the chassis.

[69gmcc10]

Rob, I am having a difficult time trying to understand how the raised ball joints create an advantage. Can you go into more detail about how these upper ball joints work and are there any disadvantages.

[gringoloco]

Originally Posted by robnolimit

We're finally getting around to putting a set on the JT. It should change the camber gain from .86deg per inch, to 1.23deg per inch. We probably won't test until after SEMA. As a comparison, our wide rides have 1.56deg/in

Would you be able to combine this with an offset upper arm bushing for more gain?

Originally Posted by 69gmcc10

Rob, I am having a difficult time trying to understand how the raised ball joints create an advantage. Can you go into more detail about how these upper ball joints work and are there any disadvantages.

Me too!

[jayman68]

Originally Posted by 69gmcc10

Rob, I am having a difficult time trying to understand how the raised ball joints create an advantage. Can you go into more detail about how these upper ball joints work and are there any disadvantages.

I was wondering about the advantage also, Thanks for explaining it.

[robnolimit]

Tall Ball Joint Geometry