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Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Transmission - Rearend> car still WHEEL HOPS why????
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Topic Review (Newest First)
08-11-2003 11:28 AM
tyson You guys should write a text manual or something.A friend of mine swears up and down that this wheel hop problem is coming from wore out body mounts.He thinks this is were the chassis flex is coming from.Do you think he has smoked to much funny stuff or what???
08-10-2003 09:01 PM
johnsongrass1 I've always been the one to play the devils advocate my self. So don't worry, absoulutly no offense takes at all. I still learnig a lot about chassis myself. The typical dirt car will set the upper right bar front link slightly higher than the left to get the car to turn left better. I always thought that the bar would change the radai that the upper bird cage would index to, loosens the rear end. As it turn out, that just another way to preload the right rear and still maintain cross weight percentages. Does the same thing.
08-08-2003 10:39 PM
TurboS10 I am not trying to fight with ya, I just like a good argument. Makes it interesting. I think from your previous post we are sortof on the same page now. I must admit circle track is not my gig. Seems to me the weight in of the cars in the corners would tend to load the right harder than in straight line. Plus we are talking dirt versus paved. Just a different world IMO.

As for 4 links they work exactly the same and axle torque is the same. This is what I was getting at on preload. Usually you turn the top right bar around 1/2 turn past where it starts to load up. This will actually raise the right side of the car and load the right tire. When the car launches the axle torque will level out the car and counter act the preloaded condition.

As for the coil setup that started this conversation......I have a friend who ran in the tens with a 80 malibu on stock suspension. He was running an air bag on the right side and a set of SSM lift bars. The car hooked really good on the street. The bag kept it level, and the lift bars really helped keep the *** end planted.

Chris
08-08-2003 09:26 PM
Scuzzy Try Original Parts Group part #2001610, no hop traction bars(just happened to have gotten the '03 monte/El camino OPG catalog the other day), have worked pretty well in past g-bod applications.... haven't tried in a monte yet, but they are great for El Camino's and they are a bit lighter in the ***** end, only cost $130 for the set too
dunno if this will cure the original problem but regardless it'll help you hook up better, as they cleared up wheel hop on my buddy's 87 el camino
08-08-2003 09:09 PM
johnsongrass1 I sorta disagree with the statement about drag racing chassis and circle track being completely different. After all, roundy round is nothing more than two drag strips connected at each end. Both types of competitions try to do the same thing, race down the straights.

Heres what I have found:
Drive shaft torque in the counter clockwise rotation will want to pull up on the right rear because it attempts to take the whole axle with it. Even though the right rear is more loaded with weight the car, the car still want's to drive off the left rear causing the car to go right. How do you explain this? The axle will twist to the right side on launch, this loads the the right rear, the weight of the chassis will push the right rear down. You would think this would counteract the tendency to unevenly distribute the weight to one side or another but the key is, that with an open differential,(which circle trackers never use) the tire with the least amount of traction will get the most power, hence a 1/8 mile burnout. In this case your right, you would add a round of wedge or preload to the right rear to get the car to launch straight. However, the bags or screw jacks or whatever are intended to increase weight on the right rear to counteract the torque twisting of the drive shaft, assumes the rear end is located with some sort of leaf spring or coil over. But, if the rear is either a IRS or a four link, the transfer of weight doesn't happen the same. With a four link rear, the axle doesn't twist in the same direction as rotational torque of the drive shaft.

My knowledge was being applied to a different type of suspension. You can beat me if ya want
08-08-2003 07:54 PM
johnsongrass1 I'll check it out and see what I can find. Fight with ya later!
08-08-2003 02:26 PM
TurboS10 Yes, I understand chassis engineering. Kindof have to be to design and build a new chassis for a vehicle. I hate to be the bearer of bad new to you, but you are mistaken on this application. Circle track and drag racing are two different animals......totally different.

While wieght is transferred to the rear right the axle torque will cause the rear right tire to lift. If you go back and look at what ever books you have read you will see this. This is why drag cars add preload to the right rear suspension to counteract the lifting of the rear right tire on launch. If it is not done, the car will not launch straight. This is also why any one holer street car will spin the right rear tire every time.

Chris
08-08-2003 01:19 PM
johnsongrass1 Tyson, You need good bushing's that support the rear end, Good geometry to start with, things like ensuring the rear is square with the centerline of the car and all angles are correct.

With a little tuning. if there are adjustable, And stiffen the chassis than you will be well on your way to long burnout's with out the shakes. Sounds as if you just have too much flex into the chassis. If applicable, build a roll cage. If not, than things like frame connectors and sway bars and other stuff should get you what you want.
08-08-2003 01:07 PM
tyson So is what you are trying to say is that i should try to get more weight transfer or WHAT?????Or should i try to stiffin the frame????
08-08-2003 11:21 AM
johnsongrass1 TurboS10, Please don't take this as a aggressive response. You are confused slightly. I don't know how much chassis dynamics you do know so I will explain. If you already know this then good,will be elementary for you.

As engines turn counter-clockwise the torque of the engine will attempt to lift the left front tire. That weight, expressed in pounds, will be transfered the the right rear. If you ever watch a circle track race you would have surely heard of cross weight's,weight jacking or wedge. They all mean the same thing. It just a theory that states when you move weight from one corner the opposite corner's weight will decrease as well as increase the the adjacent corners weights

Lets say you have a table top with four legs. If you friend stands in the middle of the table than the weight of you friend will be the same on all four legs. If you friend moves to the right then the weight will be increased on the right side and reduced on the left side. If you friend moves to the right rear than the weight increase will follow him wherever he go's.

Engine torque lifting the left front "leg" will make you friend lean his body toward the left front in order to keep himself sliding off. This will increase the weight of the right rear and left rear(although not to the same extent as the right rear) because of the weight transfer. This act of weight movement will load the right rear first.

Take a look at my avatar, that's me in the yellow car, No. 11. This car makes 770 horsepower at 8600 RPM with a RPM limit of 9200, using methanol fuel. If you look real close you can see that the left front tires is lifted nearly a foot off the ground. This pic was taken while coming out of the middle of the corner. I get back on the throttle just before mid-corner and the engine torque coupled with good forward bite and indexing of the bird cages will transfer weight to the right rear so violently that the wheel will lift and it will be carried all the way down the chutes. It only comes down for a split second while braking to make the next corner. This is a classic example of weight distribution. I have tried to add weight from the right rear and add it to the left front(called weight jacking, Nascar uses screws in the back glass to do the same thing) to move the weight around to keep the front down so it will steer better. But I lose a certain amount turn in weight on the left front in mid turn due to the weight transfer to the rear when the bird cages index and moves the weight. So it's easier and faster for me to just three wheel it. The left front tire only touches the ground twice for about a total of three seconds on 12 1/2 second lap time.

I hope I have explained this well enough. Please feel free to reply and challenge anything I have said.
08-06-2003 02:57 PM
Dave E Shank HEY TYSON: iI was at Street Rod Nationals last week and attended a technical seminar on leaf spring suspensions. It was put on by Eaton Detroit Spring, Inc. www.eatonsprings.com or 313-963-3839 or sales@eatonsprings.com E mail The owner talked about your type of problems and said to call with problems and they would be glad to help solve difficulties like yours....DAVE
08-06-2003 01:50 PM
tyson Can't be the posi i have broke several different kinds
08-06-2003 01:19 PM
Hollywooding Tyson!

Dude were you at big valley this last weekend? Good stuff there,

anyway, this might sound kinda wierd but what if it's the posi in the diff slipping intermittently???? Kinda like a grab, let loose, grab, let loose vibration that's shaking the ******* outta your ride?

Like you said though, I've done lots of research into those rear ends and yes your overpowering it, thats' why it's chewing through axles and could be the source of your wheel hop.

Just my Opinion, I'll have to do some research for this one.
HTH
Hollywooding
08-06-2003 12:34 PM
tyson It produces good power so under take off,when i am doing 50 km,when ever i give it a chance to.The wheel hops are very extreme,breaking axles and housings etc....
08-06-2003 05:22 AM
TurboS10
Quote:
Originally posted by johnsongrass1
Frame twisting under severe loads. The car might be loading the right rear, unloading the left rear and twisting the frame to the point that the frame springs back and loads the left rear while unloading the right rear.
Not to pick, but the car will load the left rear and unload the right first. Seems backwards, but think about with tire always spins first.

I am curious how bad the wheel hop is. Does it just do it once on take off, or does it shake the car under power?

Chris
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