I have a 69 mustang that has a really bad case of tire hop. When i am going dowm the road at about 20-25 mph the whole car starts moving up and down like the rear wheels are hopping. I had someone follow me to see what it was and they said the the rear wheels are hopping. I have the stock leaf springs with traction bars and a shackle kit, and a set of mickey thompsons were just put on. The leaf springs are no longer curved but straight, and are not really stiff at all. The weird thing is that this whell hop seems to only happen at about 25mph and if i go faster or slower it goes away. The guy before me had those horrible air shocks in the car so i am thinking that those shocks did a number on my leaf spirngs. Do you think that it is prosible to get the wheel hopping from bad leaf springs. It makes sense to me but a friend of mine who owns a suspension shop says that leaf srpings shouldnt do that even if they are bad!
I was just looking for any opinions.
Thanks
Matt

 

Yeah, you need new leaf springs and a decent set of shocks.

 

Your friend at the suspension shop is a smart man. While you do need new springs, they should not cause the condition you describe. Check for a bent wheel or axle or an out of round tire. Did it do this before the new tires and removal of the air shocks? BTW, if you are talking about a shackle lift kit, the air shocks were a better short term solution for saggy springs.

 

You need shocks. Plain and simple. And a car thats as old as yours you really should replace any rubber component that has to do with the suspension. But first and foremost, shocks and springs. Also, check your tires, make sure you dont have a seperated belt or bent rim.
-P.

 

Thanks for the replies! We actually jacked up the back of the car and spun the tires and the spin nice and straight up and down, side to side. We used the same rims as before, we just changed the tires on them. The tires spin straight and dont seem to have any signs of defectivness. We have new KYB gas shocks in the back along with new bushings. Could it be possible that because of the radical stance in the back, the car isnt getting enough weight to the rear tires causing them to hop around, while those leaf springs which are crap dont help the situation. It seems as if the car hops around more on decelerating at 25mph when the nose of the car settles back down. I think i am going to try and bump the shackles down one noch and see if it improves.
Thanks alot
Matt

 

I've got a similar, but different kind of hop. New heavy duty springs, urethane bushings, and new monroe-matic shocks. Car drives great, but if I hit a little bump, the rear end seems like it wants to jump to one side or the other. If I happen to be cornering and hit a bump, it's like the whole rear just comes off the ground and moves over a FOOT and then plops back down (at least that's what it feels like!). Would a sway bar help the rear stick to the street better? This car has a trac-lock rear, and new rims, tires, bearings and a proper balance and alignment...

 

If your shocks are working, you would hit a bump and the shock would depress and then go back to the regular ride height - sounds to me like maybe something in the shock or springs (leaf springs should not be flat). I would also check the tire balancing - are the weights still there? Also, what about your differential, I have a few friends with the supra rice rockets and he gets a bad vibration whenever his diff starts to go out (they are into drifting......)

 

An out of round tire, a bent wheel, or axle will vibrate at all speeds. Check to where the top of the shock attaches. Is that metal still solid, or did the air shocks punch a hole and the shock is not doing its' job? At any rate, you will need to replace those leaf springs before you can rule out anything.

 

You metion a radical stance is it possible the drive shaft angle has changed enough to cause a vibration

 

Keep remembering that it only happens at a certain (25MPH) speed. If the driveshaft was out of balance, it would cause vibration at all speeds, but especially at the higher speeds, which he reports it smooths out. If the U joints were shot, it would cause vibration at all speeds.