535i Sport handling problem?

[E34BMW]

Hi all,

My dad has an E34 535i SE Sport including M-Tec suspension, a LSD and E39 M5 replica wheels 235/45 R17 (Goodyear F1 GSD3’s) at the front and 255/40 R17 (Goodyear F1 GSD2’s) at the back.

Last Saturday we added a new increased throttle body, performance panel air filter and a viper2 chip. The car’s acceleration is transformed and has great throttle response.

However, after fitting the mods, we went out in the dry for a fast drive and noticed that the back end of the car was badly stepping/sliding out, at speed which it hasn’t in the past.

On Thursday we replaced the rear axle rubber mounts as the old ones had gone. We went back out for another drive in the dry on the same roads to find that this hasn’t fixed the problem. We have checked all the other parts of the rear suspension and can’t see anything that needs replacing.

The rear tyres are down to 2/3mm…could this be the problem?
I wouldn’t have thought that the tyres would lose grip until they are below 1.6mm but then again I the tyres didn’t squealing at al, before when you were going for it, the tyres would start to squeal and then progressively the car would start to slide. The car is unsafe to drive at full throttle while cornering on roads which it wasn’t in the passed.

The only option at the moment seems to replace the rear tyres with the newer Goodyear F1 GSD3’s and hope it fixes the problem.

Thanks to all who reply.

[Paul in NZ]

i have exactly the same car.I had the same problem i think.When i had new tires on the back and partly worn on the front the car was ok,but swapping the tires around made my car handle very badly.new back tires made it as good as before.My tire sizes were also the same as yours,but i now run 235 all round.Depending on the mileage it might be time to replace front suspension and steering parts,and maybe rear suspension parts...after all the car is at least 12 years old.....

[drum2430]

Hi all,

My dad has an E34 535i SE Sport including M-Tec suspension, a LSD and E39 M5 replica wheels 235/45 R17 (Goodyear F1 GSD3’s) at the front and 255/40 R17 (Goodyear F1 GSD2’s) at the back.

Last Saturday we added a new increased throttle body, performance panel air filter and a viper2 chip. The car’s acceleration is transformed and has great throttle response.

However, after fitting the mods, we went out in the dry for a fast drive and noticed that the back end of the car was badly stepping/sliding out, at speed which it hasn’t in the past.

On Thursday we replaced the rear axle rubber mounts as the old ones had gone. We went back out for another drive in the dry on the same roads to find that this hasn’t fixed the problem. We have checked all the other parts of the rear suspension and can’t see anything that needs replacing.

The rear tyres are down to 2/3mm…could this be the problem?
I wouldn’t have thought that the tyres would lose grip until they are below 1.6mm but then again I the tyres didn’t squealing at al, before when you were going for it, the tyres would start to squeal and then progressively the car would start to slide. The car is unsafe to drive at full throttle while cornering on roads which it wasn’t in the passed.

The only option at the moment seems to replace the rear tyres with the newer Goodyear F1 GSD3’s and hope it fixes the problem.

Thanks to all who reply.

Tire pressure can have an affect. I always keep my rears 2 lbs softer than the fronts. This "plants" the rear tires a little better in corners. I am not saying this is your only problem but try it and see what happens. Also Bruno's subframe inserts will reduce body roll thus keeping the weight distribution in the rear a little better balanced. They are cheap and really easy to install. Check out http//www.racingking.net.

Tell me about the throttle body. How much? Who did you get it from? No installation problems?

Good luck.

Gordo.

[E34BMW]

Tire pressure can have an affect. I always keep my rears 2 lbs softer than the fronts. This "plants" the rear tires a little better in corners. I am not saying this is your only problem but try it and see what happens. Also Bruno's subframe inserts will reduce body roll thus keeping the weight distribution in the rear a little better balanced. They are cheap and really easy to install. Check out http//www.racingking.net.

Tell me about the throttle body. How much? Who did you get it from? No installation problems?

Good luck.

Gordo.
The subframe inserts look good. They have now been ordered.

We first bought the chip from www.chippeduk.com for £100.
A few weeks later we bought the throttle body again from www.chippeduk.com for £136 (including sending your old one back). It seems like a different car, so much better through the whole rev range and pulls so much harder from 5,000rpm all the way to 6,5000rpm (250rpm increase from the chip but still within BMW spec) like no tomorrow.
We have also added an Alpha performance panel air filter(£35), at the same time as we fitted the throttle body. With these mods I’m told that it should increase the BHP by 43 (23bhp (26ftlb) for the chip, 17bhp for the throttle body and 3bhp for the panel filter). To me this seem correct for the rate the car now accelerates, as my friend has an Audi S3 (1.8 Turbo) with was remapped at AMD and had 209BHP on the rolling road and after his remap produced 252BHP on the rolling road. The acceleration increase seems very similar but it cost my friend £1200.

The throttle body is dead easy to install, just have to remove the air box, air follow meter, a bit of pipe/tube and then just 4 bolts which hold the throttle body onto the air manifold.

An 535i weights 1525kgs and an 3.6 M5 weights 1724kgs which is 199kgs more. If you work out the BHP per tonne this is what you get;

535i Sport - 218BHP + 43BHP = 261BHP / 1.525 = 171BHP per tonne.
3.6 M5 – 315BHP / 1.724 = 182 BHP per tonne.

Not bad going…
p.s.
Its worth noting we have both front and rear upgraded cross drilled discs and Pagid fast road pads with DOT 5.1 brake fluid to give better braking.