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p.s. there will more than likely be a switch to "disable" the ESP / TCS / ESC or whatever incarnation of the theme your car may have, check the handbook. It will more than likely cause an amber light to illuminate on your dash panel. You will then be free to wheelspin till your heart's content.
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The thumping is wheel tramp.
When you accelerate weight moves backwards, the front goes up, and the suspension goes light. The front wheel then bounce up and down. The only thng thats causing the wheel spin to the level where it starts to tramp is your right foot.
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TourVanMan TM < Ex RF >
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TVM the voice of reason,thankfully ,can you not be a moderator mate?
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I still reckon it's TCS; After Bosch perfected ABS, the company moved on to the second "building block" ? traction control. Sometimes referred to as ASR traction control (the ASR stands for "Acceleration Slip Regulation" and typically referees to systems appearing in German cars), the technology works in a similar fashion to ABS, but at the opposite end of the performance spectrum. Whereas ABS focuses on eliminating lock-up in braking situations, traction control regulates wheelspin during acceleration. In other words, when speeding from a standing stop or while in motion, a driver may give too much accelerator input, causing the wheels to spin freely. In such cases, traction control monitors wheel speed, cuts engine power or even applies the brakes to optimize contact between the tires and the road surface.
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I have bosch traction control. It stops the wheels spinning at all. ergo its not traction control
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TourVanMan TM < Ex RF >
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Nah-I've never owned a car with any kind of traction control-other than the driver inputs!
Wheel tramp sounds like what I am talking about.
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Wheel tramp sounds like what I am talking about.
Yep - that's it. Mid 80's Cavaliers were terrible for it.
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It is certainly not traction control (which should stop wheelspin altogether).
I have not heard of 'wheel tramp' - presumably you meant 'axle tramp' which afflicts mainly leaf-sprung rear wheel drive cars and is due to the torque reaction on a live rear axle 'twisting' it and causing the driver-side wheel to hop.
The cause of front-wheel drive 'wheel hop' is nothing to do with weight transfer (although that promotes the early loss of traction) but rather it is due to the torque reaction on the powertrain. When you engage the clutch the powertrain 'winds up' on its mountings. As the wheels break traction the powertrain mounts 'unwind' which momentarily allows the tyres to slightly increase traction - which winds up the mountings once again. Essentially you have an oscillatory system. The cure is to stiffen the engine mounts and also the suspension mounts. Stiffer springing and damping also helps. A 'steady bar' from the body to the powertrain is also a big help. Wheel hop is a bad thing because it can break your transmission!
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It's not TC. Front wheel hop is much worse in a non-tc car than one with tc. By worse I mean when playing silly bu---rs and doing it deliberately. Now with TC I only get wheel hop over wet cattle grids.
It's not weight transfer - on a wet surface the front will bounce up and down during wheelspin when almost stationary.
My old '80 Fiesta used to wheel hop when pulling away in the wet despite only having 55 bhp but the subsequent Nova and Cavaliers just spun their wheels without hopping. I'd go along with Aprilia and put it down to differences in engine / transmission / suspension mountings.
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'Tis tramp. Engine mounts, bushes, tyres, shocks all getting wound up and then the tyre slips and all the forces in the rubber are released and then the cycle repeats.
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'Tis tramp. Engine mounts, bushes, tyres, shocks all getting wound up and then the tyre slips and all the forces in the rubber are released and then the cycle repeats.
Isn't that what I said above?
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The cause of front-wheel drive 'wheel hop' is nothing to do with weight transfer >>
Really, I would not disagree with torque reaction being a cause however I would tend to agree with TVM re wheel tramp on some FWD cars, but to refine his explantion slightly:
When you pull away weight pitches backwards, the front goes light, one wheel finds a slippery patch, mud on the road etc, the wheel loses traction and spins, weight pitches forwards, traction is regained, weight pitches backwards, the wheel loses traction and spins, weight pitches forwards, traction is regained, etc etc all a few times a second.
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Really, I would not disagree with torque reaction being a cause however I would tend to agree with TVM re wheel tramp on some FWD cars, but to refine his explantion slightly:
No, as I said above,its not the weight transfer - although though that does help start it off. The frequency of wheel hop is well above the pitch frequency of the suspension. As I said, its due to torque reaction in the front powertrain and stored energy in the bushes. Stiffing up the powertrain mounting will pretty-much stop it. It is possible to fill hollow mountings with urethane to stiffen them. An alternative is a very stiff reaction bar between the body and engine to stop the engine from moving. Been there, done it, got the t-shirt etc etc. It does work.
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Of course, Aprilia needs no back up from me, but he is quite correct.
One interesting feature of this type of vibration is that because of the non-linear friction between tyre and road being the mechanism which allows the engines power to be fed into the vibration there are some peculiarities. Chief among them, is that during each cycle of vibration more power can be passed from powertrain into the vibration, sometimes the vibration can have negative damping - i.e., under certain conditions, the vibration can grow in amplitude exponentially.
If the wheel slip is slight, the vibration may lose more energy per cycle than is obtained from the engine. But, as the wheel slip speeds up, the effective damping reduces, until it becomes negative, the vibration increases, and is felt and heard by the driver.
Further to this, Aprilia's suggestion of stiffening the powertrain mounts works via two mechanisms; i) detuning the powertrain torsional frequency from the wheel hop frequency, and ii) reducing the amplitude of the powertrain's vibration amplitude per given amount of stored energy in the bushes (as elastic potential energy = 0.5 * k * x^2, increasing the stiffness, k, the displacement x is reduced significantly)
Number_Cruncher
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I was just about to ask if the car in question was a Vectra. My old 98R 1.8GLS (with no traction control, it was fitted to the 2.0 gls but not the 1.8) was terrible for this. My Audi does have ESP and comes on regularly and is much more pleasant than the Vectras banging.
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