E39 540 issues please help

[PowerslideSWE]

Have you checked tyre pressures? I know it sounds daft, but old BMW's are sensitive that way, friend of mine had similar issues and it turned out that one tyre was down in pressure quite alot.

[colinrob]

Will try the pressures thanks

[Talkwrench]

I wouldn't be too put off by the fact that the car ran faultlessly for 100 miles or 400 miles. It could still be all down to tyre rolling radius. The ecu's are designed to have a certain tolerance of different rotational speeds of each wheel. If you are running very close to the edge of that tolerance, it will only take a very small difference to log up an error. Something as simple as tyre temperature, a slight wheel slip on acceleration or braking etc. The systems are intolerant of cross axle differences and front/rear differences. All sorts happened on one of my 850's when I had to drive a few miles home on a spare wheel fitted to the front that was a different profile to the other tyres. Both ABS and traction ended up switching themselves off. Before the traction went off, the gear changes changed characteristics completely.

It could, however, be a rear ABS sensor. If changing the wheel dislodged some muck that is now stuck to the magnetic sensor, it could intermittantly give an error. It could also have a genuine intermittant fault, dependant on temperature. They frequently work when cold but fail when warm.

Edited by Talkwrench on Saturday 25th July 16:16

[jz325i]

Well, I had a look at one of the web sites listed above which looks like it has the correct tyre sizes for your vehicle (540i).

Now if I understand correctly and according to that web site, the correct tyres are... Front axle: 235/40 ZR 18 and Rear axle: 265/35 ZR 18

And you fitted 255/45/18 rear and 235/40/18 front.

So I calculate that your rear tyres have a rolling circumference that is 7 percent different to what should be fitted. And 6.5 percent front to rear difference.

Either way, whatever you do, read your user manual and look for what wheel sizes and tyre sizes are actually correct for your vehicle.

[PowerslideSWE]

jz325i said:

Well, I had a look at one of the web sites listed above which looks like it has the correct tyre sizes for your vehicle (540i).

Now if I understand correctly and according to that web site, the correct tyres are... Front axle: 235/40 ZR 18 and Rear axle: 265/35 ZR 18

And you fitted 255/45/18 rear and 235/40/18 front.

So I calculate that your rear tyres have a rolling circumference that is 7 percent different to what should be fitted. And 6.5 percent front to rear difference.

Either way, whatever you do, read your user manual and look for what wheel sizes and tyre sizes are actually correct for your vehicle.

Are they really supposed to be that wide in the rear on a 5 series? My 750 (e38) have 255's on the rears as stock on the 18" option

[colinrob]

Thanks everyone for there help, just got back to England this morning (4 hour wait at tunnel due to migrants)
Changed both front wheel sensors took for a drive all lights came on, drove round parts of Austria every day no gearbox issues but dashboard kept lighting up, left for home yesterday morning no lights on dashboard, got caught in long traffic jam after jam gearbox started playing up (no dash lights) after 10 miles gearbox reset itself no further problems. dashboard only lit up when I accelerated very hard, in summary I think the gearbox is over heating and wheels are causing the light issues (but why only under hard acceleration (no lights at 120 mph in Germany) any help on the overheating would be appreciated.

[eliot]

PowerslideSWE said:

Are they really supposed to be that wide in the rear on a 5 series? My 750 (e38) have 255's on the rears as stock on the 18" option

From memory on my 540 sport they were pretty beefy on the back, one of the reasons I liked the look of the e39's