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Live axle incident.


John E

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Last weekend I almost had a serious off in my live axle crossflow.

I clowted a moderate size stone with the offside front wheel after losing the back end. I was quite surprised by how quickly the car broke away and how difficult it was to bring it back into line. Admittedtly the road surface was a tad greasy but have others had the same kind of problem.

I wonder whether the car is just not suitable for anything other than dry road use as under almost any kind of throttle opening it is possible to slide the rear. Now we're only talking 140+ bhp but we are on very crap tyres which are of 205 width.

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I was follow john (well i would be wouldn't i) in my

W E S T F I E L D with a proper independent rear end and LSD i was steady as a rock, but can vouch for the fact that the road surface made driving a se7en type car very interestingbiggrin.gif

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My live axle car has recently been converted to LSD, it does help with the traction, but bear in mind that when it lets go, you lose both wheels! The slides are a lot more predictable though and the cornering feels 'flatter'. An expensive but great mod!

 

 

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John, I had exactly the same experience in my 205 shod car, albeit Dedion rear end. When the rear end broke free it came around so quickly it was outside my ability to control it, resulting in an expensive repair bill but thankfully no personnel injury. Concequently my driving in the seven has since been a little more reserved, and led me to believe that my everyday car, an RS Escort, is far more manaegable on our far from perfect public roads.
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I find the great joy of my 7 (which does have alive axle) is the ease which silly powersides can be enjoyed. Give me a quiet wet roundabout and I will show you opposite lock - err whilst on private roads obviously.

Whilst I hate to mention the topic, aged 205 tyres sounds like the problem on a wet road.

 

Whilst I'd say a 7 handles infinately better, most front drive hatches are easier to drive at speed on a wet road.

 

Edited by - James Arnold on 12 Feb 2001 09:09:35

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Fair weather cars ? Fair weather drivers?

 

How about a bit of throttle control?

 

Breaking the back end of a Seven on wet road would seem more a matter of choice than a problem or a fault.

 

The old saying is "the biggest problem with any car is the nut behind the wheel"

 

I always thought driving sideways was fun.

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Have a read of December's Low Flying. In the handling test we encountered a Seven that was *horrible* to drive and unpredictable in the wet.

 

Badly set up Sevens are much, much worse than competent tin tops.

 

Just by adjusting the rear ride height on my Superlight, I can make my Seven handle badly - worse than most competent tin tops.

 

The good news:

 

Whatever is making the car nervous in the wet can be fixed.

 

 

The bad news:

 

We are not as far ahead of tin tops as we would like to think.

 

Two incidents remind me of this.

 

First, I was driving around Donington Park in my Superlight, going really well and among the fastest of the fast session when I was caught up by a Honda Integra R (on slicks, some engine mods) - I let him past and watched his lines.

 

Second, there was a wet day at Kemble airfield when a bog standard, comfort spec BMW 323i Coupe overtook all other participants on a trackday including Sevens, Elises, TVRs (Chimaera and Cerbera) and Porsche Turbos and was one of the few cars not to spin all day despite attaining some rather eccentric angles of drift. The driver had the traction control switched off, stereo on, was driving holding the steering wheel between thumb and forefinger of one hand and was answering mobile phonecalls.

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Chris, ouch!!! but thanks for the comment,

 

Peter, thanks for the comment. I think that unpredicable is the correct term. I dont think that I am to heavy with the gas pedal, we can all cause our cars to slide by provocation. My incident certainly un nerved me and has caused me to consider whether or not the car is set up properly. the Low Flying article is very interesting and I seem to remember a comment, "I didnt think that a 7 could handle so badly". I'm sure that the owner of the vehicle referred to thought that the car was OK under most circumstances, not until the unexpected happens do you realise its limitations.

The question is where do we go to from here?

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I'm trying to rationalise an explanation for *unpredictable* handling. In the end it all has to come down to tyre contact patches and what you are doing with them.

 

205 section tyres (crap ones) sound much too big (and crap), using the rule of thumb that correct tyre size for road use is mostly down to weight. 185 is probably nearer the mark. Old tyres harden and become next to useless.

 

Next up you have to wonder about the correct functioning of the suspension components. Springs are simple. Dampers are more complex and can have given up the ghost without much external indication. Look for fluid leaks. The suspension movement should be supple. Think about the way the car behaves in these circumstances:

 

1. Braking - should pitch noticeably, but not excessively.

2. Cornering - should roll progressively; should feel fluid in a series of bends

3. Compression - should feel all the springs compress to take up the load and then rebound over a period of about 1 second.

 

Bounce the car at each end. It should move and rebound and settle. Before we get into adjustments we need to know that the bushes are in good shape and the bearings are OK. Jack up each corner in turn and test the bearings in the approved manner. With the front wheels in the air check the free movement of the steering. Check all suspension attachments are secure, particularly the radius arms. Check the A-frame bushes.

 

Right. Now its down to adjustments and I have no idea about live axles - over to someone else...

 

P.S. I don't think you're too heavy with the right foot either.

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Bloody hell Peter what a star you are. Your replies are always informative and include a feeling of, I've been there and a genuine willingness to help. Excellent and thank you.

The car has all new shockers, Spax set at number 3. All new springs, 100 rear and 200 front, all new bushes back and front, just changed the A frame. All fitments are sound and have been torqued correctly with the car on its wheels.

The suspension certaily seems to take the rebound very well and settles OK. I've checked and re packed all bearing and they seem ok as well. The car does pitch slightly under braking and so my conclusions are that the tyres, Fulda, 205 x 70 x 13 are way over size and probably very hard rubber. They are probably the originals 1990, and I suspect are in need of change. Whilst I havnt driven this car on the track I have a reasonable level of experience, 250 g/box Karts and I confess that the thought of a fully blown drift in this vehicle does not fill me with delight. Looking at the photographs of the recent test day comparison and reading the text I feel that my vehicle would currently stand out somewhat. Maybe a similar test for live axle cars would be worth organising. I would certainly offer mine.

 

 

 

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I'm sure that you are right, I've probably changed to many things and not done it progressively enough. We have some nice weather on the way and so I'll start with the shockers. It would be good to compare with other vehicles though particularly those in a similar state of suspension set up and rubber.
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Other thing is, of course, tyre pressure.

 

My first track experience was punctuated with a spin on a greasy Goodwood chicane. Next track day at Donington I did the same in the last session when it started to drizzle. I was running far too high tyre pressures (20psi cold in 13x6-21 ACB10s) and ever since I took to running with 16.5 psi cold I haven't had a problem.

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Currently 18 psi all around cold. One of the reasons that I changed the springs/shockers was because the side exit exhaust can was bottoming on right hand corners. I concluded that the ride height was ok but that the springs were to soft allowing to much body roll. I was advised by Caterham on the spring upgrade and this was confirmed by James Whiting.
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