traction issues with short trailing arms - The 1947 - Present Chevrolet & GMC Truck Message Board Network

joehalford01 · 03-16-2008, 08:53 PM

Hey guys,

I haven't been working on my 63 in a while, it's down to the frame and it's been sitting that way for a few months. I was going to go long and low but now i'm considering bob-tailing it with a small flat bed and only putting air bags in the rear for ajustability. I have a bridge kit i'm going to weld in right behind the cab and mount the rear axle right there. With this I want to shorten the rear trailing arms an equal amount. Besides the traction issue from the standpoint of having no weight back there (at least i can go as wide as i want on the tires

). Will I run into any traction issues or adverse suspension problems from having excessively short trailing arms? My concern is that being so short, they will not be able to travel much before bringing the axle up and down, making it bouncy and uncontrollable under wot. I don't think i will many safety issues with the tired 327 i have but when i pull it later to rebuild or upgrade, then what? Thanks.

djracer · 03-17-2008, 12:30 AM

I would keep it atleast normal short bed length. and just buy a short bed and don't cut the trailing arms down just move the mount forward.

joehalford01 · 03-17-2008, 01:39 AM

duh, i can't believe i didn't think of that. haha. Moving the mount up sounds alot better then shortening the trailing arms, easier and it'll work. I know most might not care for the super short look but i want the old skool hot rod kinda look. I think having some huge street slicks right behind the cab would look real cool. Thanks dude.

Super73 · 03-17-2008, 03:48 AM

There are both advantages and disadvantages to a shorter rear control arm.

With a shorter control arm, if you move the front mount up or down, it is going to have more effect on antisquat and instant center of gravity than a longer (stock length) control arm. But, it is going to be more prone to wheel hop and jacking the rear causing it to unload the rear tires under heavy braking conditions. Not good for auto crossing road racing ect. For straight lines though, that might not be a big deal for you.

Moving the full set up forward is also going to change your Center of gravity, ICG and AS. You might be able to over come the adverse affects of moving your CG. With less weight in the rear you are affectively moving your CG forward. By moving the axle forward and keeping the factory length control arms your ICG point moves forward as well.

You really won't know unless you weigh the truck as it sits now and take measurements on the suspension. Then weigh it again and re measure once your work is done.

But do yourself a favor and make an adjustable front mount so you do have some tuneability.

joehalford01 · 03-17-2008, 09:36 AM

Quote:

Originally Posted by Super73

But do yourself a favor and make an adjustable front mount so you do have some tuneability.

What do you mean by an adjustable front mount?

Super73 · 03-17-2008, 10:52 AM

http://67-72chevytrucks.com/vboard/s...d.php?t=278864

joehalford01 · 03-18-2008, 09:40 AM

thats sweet dude. i may have to build it and see how it handles, then try that if i need to adjust it. I'm curious though, if i moved it forward, wouldn't i be moving the cg more towards the middle? Wouldn't that make it handle better? Similar to a mid engine sports car? I've got two corona's in me, so i could be way off right now

. Thanks.

Super73 · 03-18-2008, 06:50 PM

Yes and no.. If you cut the bed and loose what is behind the rear axle, you are moving the CG forward even before moving the axle forward. Once you move the axle forward you are then moving the CG backwards again.

03-16-2008, 08:53 PM	#1
joehalford01 Registered User Join Date: May 2007 Location: Visalia, CA Posts: 98	traction issues with short trailing arms Hey guys, I haven't been working on my 63 in a while, it's down to the frame and it's been sitting that way for a few months. I was going to go long and low but now i'm considering bob-tailing it with a small flat bed and only putting air bags in the rear for ajustability. I have a bridge kit i'm going to weld in right behind the cab and mount the rear axle right there. With this I want to shorten the rear trailing arms an equal amount. Besides the traction issue from the standpoint of having no weight back there (at least i can go as wide as i want on the tires ). Will I run into any traction issues or adverse suspension problems from having excessively short trailing arms? My concern is that being so short, they will not be able to travel much before bringing the axle up and down, making it bouncy and uncontrollable under wot. I don't think i will many safety issues with the tired 327 i have but when i pull it later to rebuild or upgrade, then what? Thanks.

03-17-2008, 12:30 AM	#2
djracer Registered User Join Date: Feb 2001 Location: Wetumpka, Al, U.S. Posts: 8,891	Re: traction issues with short trailing arms I would keep it atleast normal short bed length. and just buy a short bed and don't cut the trailing arms down just move the mount forward. __________________ Kevin Special Thanks to All who have helped on the TRUCK! My Pass Time Show http://s129.photobucket.com/albums/p...Chapter1-0.mp4 So Far my best Times are: Motor only: 6.44 1/8 @ 104.13 10.39 1/4 @ 125.83 Nitrous Times: 5.785 1/8 @ 118.65 with a 1.336 60ft 9.168 1/4 @ 142.58 with a 250 shot dead out of the hole!

03-17-2008, 01:39 AM	#3
joehalford01 Registered User Join Date: May 2007 Location: Visalia, CA Posts: 98	Re: traction issues with short trailing arms duh, i can't believe i didn't think of that. haha. Moving the mount up sounds alot better then shortening the trailing arms, easier and it'll work. I know most might not care for the super short look but i want the old skool hot rod kinda look. I think having some huge street slicks right behind the cab would look real cool. Thanks dude.

03-17-2008, 03:48 AM	#4
Super73 Registered User Join Date: Nov 2007 Location: Bay Area, Ca Posts: 2,841	Re: traction issues with short trailing arms There are both advantages and disadvantages to a shorter rear control arm. With a shorter control arm, if you move the front mount up or down, it is going to have more effect on antisquat and instant center of gravity than a longer (stock length) control arm. But, it is going to be more prone to wheel hop and jacking the rear causing it to unload the rear tires under heavy braking conditions. Not good for auto crossing road racing ect. For straight lines though, that might not be a big deal for you. Moving the full set up forward is also going to change your Center of gravity, ICG and AS. You might be able to over come the adverse affects of moving your CG. With less weight in the rear you are affectively moving your CG forward. By moving the axle forward and keeping the factory length control arms your ICG point moves forward as well. You really won't know unless you weigh the truck as it sits now and take measurements on the suspension. Then weigh it again and re measure once your work is done. But do yourself a favor and make an adjustable front mount so you do have some tuneability.

03-17-2008, 10:52 AM	#6
Super73 Registered User Join Date: Nov 2007 Location: Bay Area, Ca Posts: 2,841	Re: traction issues with short trailing arms http://67-72chevytrucks.com/vboard/s...d.php?t=278864

03-18-2008, 09:40 AM	#7
joehalford01 Registered User Join Date: May 2007 Location: Visalia, CA Posts: 98	Re: traction issues with short trailing arms thats sweet dude. i may have to build it and see how it handles, then try that if i need to adjust it. I'm curious though, if i moved it forward, wouldn't i be moving the cg more towards the middle? Wouldn't that make it handle better? Similar to a mid engine sports car? I've got two corona's in me, so i could be way off right now . Thanks.

03-18-2008, 06:50 PM	#8
Super73 Registered User Join Date: Nov 2007 Location: Bay Area, Ca Posts: 2,841	Re: traction issues with short trailing arms Yes and no.. If you cut the bed and loose what is behind the rear axle, you are moving the CG forward even before moving the axle forward. Once you move the axle forward you are then moving the CG backwards again.



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