Understeering M5

[clositintelctual]

I have a very nice BMW M5 1993 3.8, It has a few minor mods uprated front and rear anti roll bars 18 inch wheels supachip K&N. It does not have nurburgring suspension. My problem is on track days i find it predominantly suffers from understeer, very safe but a little boring, it is possible to provoke opposite lock but you have to really boot it, I cant help feeling if it was a more neutral it would be quicker through the bends and much better fun. I use contisports 235's front and 265's rear. I dont want to change camber angles etc as it would eat tyres and at £150 a piece i wouldnt be able to afford track days so what would be the point.

[GreenV8S]

quote:I have a very nice BMW M5 1993 3.8, It has a few minor mods uprated front and rear anti roll bars 18 inch wheels supachip K&N. It does not have nurburgring suspension. My problem is on track days i find it predominantly suffers from understeer, very safe but a little boring, it is possible to provoke opposite lock but you have to really boot it, I cant help feeling if it was a more neutral it would be quicker through the bends and much better fun. I use contisports 235's front and 265's rear. I dont want to change camber angles etc as it would eat tyres and at £150 a piece i wouldnt be able to afford track days so what would be the point.

What is the difference between your standard and uprated ARBs? Typically, you'd reduce understeer by softening the front arb or stiffening the rear. If the uprated ARBs are stiffer, you might try refitting the original front ARB. If you keep the changes small you can go a long way with just a little theory. Bear in mind though, there are umpteen variables at work here and if you have a big problem you need to consider the system as a whole rather than just pick one component and hope that will give you the right setup. Getting the car set up properly (spring, dampers, ARB and geometry) by an expert will probably give a better overall solution if you can afford it.

[CarZee]

Sorry to butt in, but I just wanted to comment that in action here is one of the brilliant things about PH - Friendly people with shedloads (garageloads?) of experience in the whole range of black arts.

People have said this in some of the IT threads before, but I guess I just didn't appreciate how valuable it all is when I'm on the giving end of the spanner of knowledge.

So, nice one Peter..

(Sorry about that - just had a sudden rush of humanity there... I'll be alright in a minute.. )

[M-Five]

With the larger tyres on the back you will always get understeer before oversteer.

Try putting 245/40 Z18 (or 235/40 Z18) on the rear and see if that helps.

I run 245/40 Z18 all round on my '94 M5 (with Nurburgring suspension) and on proper circuits it is fine - it only understeers when I start gooning around in the dry on airfield days.

If it's wet I get plenty of oversteer in 1st through 4th.

[adrianr]

First question - was all the geometry setup properly after the mods? You'd be amazed how many people don't even get the tracking done!

Have you tried experimenting with tyre pressues - go up a couple of pounds one end and down a couple the other and you may be able to tune it to your tastes. Set the tyres cold and then measure what they get to when hot first so you can keep track.

AdrianR

[clositintelctual]

Thanks for all your thoughts i will definately check the geometry as i have all the necessary gauges, and it is worth playing with tyre pressures. the ARB's have adjusters on and i have set them on soft front hard rear. I am also in the process of looking for a dedicated track car together with 3 mates, £2000 each will get us a good ex rally car to play with then i will just use the M5 on the road, well that is untill I go to the next track day and get carried away.