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#1 |
Senior Member
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Location: Dandridge, Tn. USA
Posts: 2,226
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Re: Make it handle
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.
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#2 |
Senior Member
Join Date: Aug 2002
Location: Plymouth, MA
Posts: 891
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Re: Make it handle
Rob, do your front trailing arm mounts (uniballs?) fit in the stock trailing arm brackets?
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1972 Blazer body...need to get a thread started for the rest of the story |
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#3 |
Senior Member
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Location: Dandridge, Tn. USA
Posts: 2,226
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Re: Make it handle
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.
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#4 | |
Registered User
Join Date: Nov 2010
Location: Santa Fe Springs, CA
Posts: 134
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Re: Make it handle
Quote:
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. ![]() |
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#5 |
Registered User
Join Date: Jun 2011
Location: Richmond,Va
Posts: 2,934
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Re: Make it handle
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!
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Nick Carter 1967 C10 Short bed Fleetside Project Cheap Thrills! 2WD C10 Modern/Performance Alignments Easiest Alignment Ever! |
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#6 | |
Senior Member
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Location: Dandridge, Tn. USA
Posts: 2,226
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Re: Make it handle
Quote:
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#7 |
Registered User
Join Date: Jun 2011
Location: Richmond,Va
Posts: 2,934
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Re: Make it handle
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.
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Nick Carter 1967 C10 Short bed Fleetside Project Cheap Thrills! 2WD C10 Modern/Performance Alignments Easiest Alignment Ever! |
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#8 |
Registered User
Join Date: Mar 2010
Location: Chandler,Tx
Posts: 78
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Re: Make it handle
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 ?
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#9 |
needs more $$$
Join Date: Mar 2004
Location: Sacramento
Posts: 1,936
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Re: Make it handle
Yes to all...(Sorry I'm not Rob, but...)
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1970 2wd Blazer |
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#10 |
Senior Member
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Location: Dandridge, Tn. USA
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Re: Make it handle
Right you are TubedII. The scrub line gets pretty close when you have a 2" block with 15" wheels. Just remember that the shorter the spring is, the stiffer the truck will feel.
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#11 |
needs more $$$
Join Date: Mar 2004
Location: Sacramento
Posts: 1,936
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Re: Make it handle
[QUOTE=robnolimit;4965404]Right you are TubedII.QUOTE]
I'm gonna print and frame this... ![]()
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1970 2wd Blazer |
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#12 |
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Location: Dandridge, Tn. USA
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Re: Make it handle
[quote=tubbedII;4965720]thanks, lol
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#13 |
Registered User
Join Date: Mar 2010
Location: Chandler,Tx
Posts: 78
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Re: Make it handle
What would be the ideal way then to lower 5 inches and stay with 15 inch wheels ie, best ride and handling ?
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#14 |
Senior Member
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Re: Make it handle
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.
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#15 |
67-72 parts collector,…
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Location: Mid-MO
Posts: 22,717
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Re: Make it handle
I would use a 5" drop spring.
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#16 |
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Join Date: Jan 2011
Location: Mount Airy, NC
Posts: 132
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Re: Make it handle
Greetings Rob, did you ever get any results for the raised upper ball joints?
Thanks
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#17 |
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Re: Make it handle
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
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#18 |
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Join Date: Jan 2007
Location: sc
Posts: 10
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Re: Make it handle
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!!! |
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#19 |
56 - autocross
Join Date: Apr 2010
Location: Camarillo, Ca
Posts: 1,121
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Re: Make it handle
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 |
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#20 | |
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Re: Make it handle
Quote:
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#21 | |
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Re: Make it handle
Quote:
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#22 |
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Location: Missoula, MT
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Re: Make it handle
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.
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#23 | ||
A guy with a truck
Join Date: Sep 2005
Location: Germany, for now
Posts: 5,921
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Re: Make it handle
Quote:
Quote:
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#24 | |
Fun Stuff
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Re: Make it handle
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#25 |
Senior Member
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Location: Dandridge, Tn. USA
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Re: Make it handle
Tall Ball Joint Geometry
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