[30ONA]

Recently I was surprised when I moved into a roundabout with ease, but got axle tramp. As it was raining I was being cautious, but perhaps not enough and the rear axle bounced like crazy. I already suspected the shocks could be replaced all round, is this likely the cause? Mine also has 50mm raised red springs in the rear. Presumably the previous owner used it too tow.

[alien]

Mine has trac bars and i still get 'tramp' - it's more to do with putting down enough power to spin the wheels, but not enough to spin them consistently, so they grip then let go then grip again etc. This is only on dry roads though. Maybe you just found that balance point on yours?

Try replicating it to see if it does it all the time or if it was just a fluke?

[fordem]

Are you sure the axle "bounced"? I think it highly unlikely that you could get enough traction on a wet road to wind the springs up enough for that.

My experience with the GV on wet asphalt has been that if you're not careful putting the power down in a turn, it will spin the inside tire or even break the back loose, but I've never had an axle tramp issue with my GV, wet or dry.

[Gwagensteve]

Sounds like the shocks are shot.

[just_cruizin]

Axle tramp in a link suspension, sounds like your bushes are stuffed.

Tramp is similar to axle wrap where the diff housing itself rotates. In a linked setup this is limited to the give in the bushes, a leaf Spring it bend the leaf into a 'S' shape and isn't really limited by anything other then the leaf itself

[30ONA]

Was straight line very slow take of from stand still. Its only happened once.
Was deff tramp.

[Gwagensteve]

My renaultsport Clio would tramp under certain circumstances and I can assure you it didn't have worn bushes., but it was softly damped for the type of car.

Tramp isn't necessarily due to wind up or wrap.

[fordem]

Gwagensteve wrote:

Tramp isn't necessarily due to wind up or wrap.

What are the other causes?

The Clio is front engine front wheel drive, I've never driven a Clio, but my experience with FWD "hot hatches" has been that IF you have enough torque AND traction you can get violent wheel hop (I'm not calling it axle tramp because it's IFS) due to soft engine mounts, but we're discussing what is in effect a RWD vehicle on wet asphalt.

30ONA wrote:

Was straight line very slow take of from stand still. Its only happened once.
Was deff tramp.

Straight line, very slow take off from a stand still.

I'm very puzzled here - how do you take off in a straight line on a roundabout? If you're on a roundabout, you should be moving in a circle, if you're now moving off, you're probably entering the round about, so you should actually have more lock on than if you were already in the roundabout - what am I missing?

Very slow take off from a stand still in the wet - you have neither the torque nor the traction for axle tramp to occur.

[Gwagensteve]

OK, there's semantics here that I'm obviously unhelpfully glossing over.

Here's my take.

I think 30ONA has experienced wheel hop, not "tramp" if "tramp" can only be related to axle wrap. (Personally, I think they are the same thing - uncontrolled vertical oscillations of the wheel off the road surface)

The cause of tramp/hop *might* be axle wrap in a leaf sprung vehicle, it might be soft/inadequate/failed damping that results in the damping being inadequate for the force at work, it could be a broken engine mount, or excessive traction for the suspension design/damping (the example of putting very grippy tyres on a car without increasing damping)

We have to assume that 30ONA understand what they felt and it WAS wheel hop. That being the case, the most obvious cause would have to be inadequate damping, as the other most obvious causes - high traction or axle wrap aren't likely.

Steve.

[fordem]

The point I want to make is this - even with inadequate damping - there needs to be something that triggers the initial vertical motion that progresses to the point of becoming an uncontrolled vertical oscillation.

A couple of years back I picked up a Pajero iO at a very good price, amongst the problems it came with were dead rear shocks (if you're not familiar with it, it's a compact 4WD just smaller than a Grand Vitara, and with a suspension design that it is very similar) I'd be picking up my daughter from work and on the way in and out of her office compound I would be rolling over a "speed bump" (also known as sleeping policeman, I assume you have them in Australia) - the back of the iO would bounce a couple of times, but as far as I know the tires never left the ground, there was never any sensation of wheel hop, although there might been if I were on the throttle, but, on a very slow take off, over a speed bump, it just never happened.

[30ONA]

My car is a a coil sprung solid rear axle, no leafs.

[alien]

With mine it's simply a case of no weight over the rear axle. Accelerate from standstill, weight transfers backwards and compresses, tyres compress and as momentum forwards starts the weight lessens, the tyres spring back, lose a bit of traction and boom, tramp. If i accelerate harder, the wheels spin. If i accelerate less it goes away. There's just a sweet spot on mine where it'll happen, so as soon as it does i (usually) just back off the throttle a bit and by that stage it's time to change into 2nd anyway.

[Grags]

Wheelspin of any kind on a smooth surface like bitumen wet or dry will show up deficiencies in a suspension system
how old are the shocks, are they soft/standard or are you sure that they are matched to the different springs in the back
While we are at it, probably nothing to do with wheel hop, but are the shocks also the right length, eg do they still hold the springs in their seats when the car's jacked up and stands under the chassis rails? check that out anyway
Your problem... either the shocks aren't valved to suit the springs, or they are just worn out, or the suspension and/or shockie bushes are on the way out.. or given the age of the car all 3
Rule of thumb because this is all from a description and no pictures or info on the condition of the parts...
Thumping/bouncing on acceleration = usually shocks
gripping letting go, gripping letting go = usually bushings doing an imitation of leaf spring wrap-up
Hope that helps
Can you post up some pics?
Just have to remember, there's always some kind of compromise going on in cars like a GV. ride quality, space considerations, cost of manufacture. but not horsepower haha

[fordem]

Grags wrote:

Wheelspin of any kind on a smooth surface like bitumen wet or dry will show up deficiencies in a suspension system.

Why would/should there be wheelspin on a "very slow take off from a stand still"?

[alien]

Wet, oily road? Coolant is crazy slippery too.