Axle tramp on sprint starts

[NicD]

I had a member ring me the other day asking whether the fairly severe axle tramp he was experiencing on his Boxster S was normal. This was on a quarter mile sprint, so a racing start. This is in line with my experience at a hill climb, so perhaps typical for the model. John said he had not experienced this with previous cars - TVR, Lotus etc.
So why more tramp on a Boxster S? All I can think of is, the mid engine configuration makes for more weight over the driving wheels and relatively soft suspension (even though Sports) can not control the movement when started.

What driving (racing) technique to minmise the tramp while maximising the acceleration? Drop the clutch at 3000, then feed in power gently or ...

Over to you guys:

 

[Mark_Bennett]

I've never subjected my transmission to such treatment, so cannot help a great deal here.

Perhaps the TVR guys who cooked the Boxster clutch on Top Gear can help?[:'(]

I'm really suprised at getting axle tramp at all though - something I would have attributed more to soft suspension (surely?).

Also, the mid-engine layout means that more weight is over the driven wheels - I thought it was old front engined/rear drive cars that are more susceptable to axle tramp due to no weight over the driven wheels.

This just doesn't add up - has anyone else experienced this on the Boxster?
(Do you mean by "This is in line with my experience at a hill climb" that you have experienced this as well Nic?)

Or am I just completely off-line with my reasoning?

 

[timhum2002]

I experienced a similar effect in my Boxster S. I put it down to the weight being in the right place for traction but with not enough torque to break the grip of the tyres. I now have a 996 which doesn't appear to suffer from 'axle tramp' and will spin the wheels. I must confess that I haven't tried many quick getaways (it feels far too brutal) in either car so it could be lack of skill.
Wasn't the axle tramp of years gone by down to poor location of a solid axle with leaf springs alone?

regards

Tim

 

[Melv]

"Wasn't the axle tramp of years gone by down to poor location of a solid axle with leaf springs alone?"

Yes, but as a result of transmission wind up due to soft springing. There's your answer...

Mel

 

[matt643]

yep, I've had it. I'm pretty brutal with my boxster, or at least I was in the early days of ownership!!

If you 'drive it like you stole it' then the weight of the engine as you pull away forces the tyres into the tarmac, the tyres eventually loose their grip on the black stuff and slip causing a momentary weight shift which causes the 'tramp'


I've had it really badly on two occasions, (1) when I lit the back end up on a semi wet day on a section of tarmac frequently used by our heavy fuelled brethen and (2) when I had a new set of tyres fitted to the rear of my motor and the afore mentioned tyres still had that 'orrible silicone mould release on them.

And yes, the guys at just tyres were a bit p*ssed off with the black marks out of their depot!!

perfectly normal for a perfectly balanced motor car!!

 

[Guest]

Now I'm really impressed! I knew Porsches could do many things but to get axle tramp without an axle is truly amazing!

 

[Nick Moss]

Surely axle tramp in an IRS setup is due either to transmission windup or inadequate damping.

 

[Bill Stewart]

I rallied an Opel Manta 16v with 4 link rear suspension & coil springs. Despite the axle being well located it used to "tramp" on tarmac stages when the shock absorbers were starting to become tired and unable to control the rear axle. Whilst the Boxster has IRS could this be part of the problem?

 

[NicD]

Now I'm really impressed! I knew Porsches could do many things but to get axle tramp without an axle is truly amazing!

Its a figure of speech Ian

 

[JCB..]

Nic

It's more than a figure of speech.

Whilst you might have trouble accepting the lineage the last component of the drive-train of the VW Beetle and vans was and is referred to as a swing axle. With the advent of the double CV jointed IRS setup on later models the term fell out of use even though they are effectively still 'swing-axles'.

I might be wrong but I believe that the 356 has the same setup.

Furthermore it's very easy to experience the same "tramping" if you stick a big enough motor in one without tweaking the suspension.

JCB..

 

[Kevin Cooke]

Best ever Axle tramp experience was in a Rally Range Rover in Dubai in the 80's.

It had a 4.5 ltr TWR engine moved back a few inches and a fast back rear end. At traffic lights on sand tyres you could get smoke pouring out of all four wheel arches and have both front and rear axles jumping up and down trying to detach themselves from the car. The the whole thing would then leap forward at an incredible pace.

It would also fly level from undercut sand dunes.