New Guy Needs Help !

Suspension Tuning, Troubleshooting, Design and Discussion

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graydog
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New Guy Needs Help !

#1 Post by graydog » Fri Apr 28, 2006 10:26 pm

Hello everyone
I've been reading the forum for some time now and finally have some questions for some real racers. I've been helping my brother with his truck this spring and we're having some major wheel hop issues. Its a 1949 chevy with a chassis engineering 3 link back half with a late 70s nova front clip. It weighs 2850 with driver and 1700 front and 1150 in the rear. It has single adj. coil overs with 110 lb springs. The wheel hop is so bad that it broke both axles a couple weeks ago. The only thing that seems to help is loosening the rear springs and raising the tire pressure. I don't think the spring pressure is perfect but it should be close. The slicks are kinda old but would this cause wheel hop? Tonight we played with the shock settings with no real results. I think the tire pressure is just a bandaid fix for something else. Anyone have any ideas?? Thanks

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John_Heard
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#2 Post by John_Heard » Sat Apr 29, 2006 8:55 am

Adding air pressure is probably just band-aiding the problem. The first two things I would sugguest is a fresh set of slicks and some good video of what the truck is doing at launch so you can watch it in slow motion.

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#3 Post by graydog » Sat Apr 29, 2006 2:48 pm

Thanks for the input. We've been talking about a new set of tires since day one. My brother seems to think if it were the tires it would spin not hop. I'm not sure I agree. New tires would definitely take out the unknown part of the equation. Thanks again.

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#4 Post by graydog » Sat May 06, 2006 7:52 pm

Well we tried a new set of tires today with the same results. After looking at some video the truck looks like it wants to bite then unhooks. It also looks like it squats alot more on take off than we thought so we looked at the shocks and the drivers side is bottoming out. My question now is shouldn't the suspension be working the other way and would moving the front of the ladder bar to another hole help plant the tires harder? The mount has five holes and were in the middle now. The bars are almost paralel with the ground. Any help woud be appreciated!!

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#5 Post by John_Heard » Sun May 07, 2006 8:30 am

If you want to extend the shocks more at launch, you'll need more anti-squat, since you have laddar bars this will be easy to try. Just move the front up a hole or two, that should shorten he instant center and make it plant the tire harder at launch. Give that a shot. At least you know now that the old tires are most likely not the issue. Do you have a way to post the video that you took?

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#6 Post by graydog » Sun May 07, 2006 11:06 am

Thanks Beyond. That's what we will do for the next time. I have no idea how to post a video. I guess I'm still in the stone age. I'll let you know how it does.

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#7 Post by jones_performance » Mon May 08, 2006 12:04 am

id try to get that front to rear weight closer to 50/50
Kevin

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#8 Post by graydog » Mon May 08, 2006 7:44 pm

I guess we could put another engine in the back. :lol:

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#9 Post by graydog » Mon May 15, 2006 11:49 pm

We got to take the truck back to the track again this weekend. We moved the bars from the middle hole to the top hole skipping one. We now have to much separation and are running out of shock travel on extension. I guess we moved the instant center to far back. We're going to try the hole we skipped and maybe figure out a way to put some weight in the back. This is getting old real quick!

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#10 Post by John_Heard » Tue May 16, 2006 9:22 am

It'll be worth it when you get it all figured out. You may end up needing shocks with a stiffer valving on the rebound/extension.

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#11 Post by graydog » Tue May 16, 2006 10:03 am

We're using adjustable chassis engineering coil-overs now. In both situations we could help the hop with shock adjustments but couldn't fix it completey. Once those big tires start bouncing it's all over.

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Mike Peters
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#12 Post by Mike Peters » Tue May 16, 2006 10:32 am

Just a few thoughts here.........first of all Chassis Engineering shocks are not good. I think you've already proven this to yourselves with statements the shock looks like it bottoms out. Sounds to me that the shocks can't control the violence of the launch of your truck. I would set the ladder bars back to the hole which is parallel at ride height. Spring pressure really doesn't have anything to do with launch other than setting vehicle ride height. If your springs are too weak, you can be using up shock travel trying to compensate for a spring that needs help holding the vehicle to the desired ride height. If the spring is too stiff, it can fight the shock valving. I would say I'd like to know how much power you're trying to put to the track as a high horsepower vehicle chassis set-up is not the same. Until you can control the reason the truck is hooking and then unloading, trying to plant the tires harder by changing suspension geometry is not going to solve your problem. Moving ladder bars or other suspension links changes so many things and is not as simple as unbolting and moving them to the next hole. So many things need to be checked but, I would say buying a good set of shocks would be the first step. Hey, you haven't even discussed the front suspension. I've seen cars unload the back tires when the front suspension tops out. If the truck is initially hooking and then unloading as you described, you need to track down the reason for the unloading and not looking to try to dial even more bite into the chassis. Just so many things it could be........

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#13 Post by graydog » Thu May 18, 2006 12:04 am

Mike, you have alot of valid points. I'm almost sure now the problem is in the front. The truck just doesn't have enough power to transfer the weight with the limited front suspension we're using. We either need more front travel or a big shot of nitrous :) The suspension will probably come first.

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Mike Peters
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#14 Post by Mike Peters » Thu May 18, 2006 7:36 am

Keep us posted of what you learn and analyze the whole situation. Most of all, enjoy the adventure.
"If winning was easy, losers would be doing it"

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