traction control problem

[hippee]

hi everyone I'm having a bit of bother with my 1999 328 when you put your foot
down the traction control light flashes and you cant get to far unless you switch it
off. Has anyone got any ideas on why this is happening your help would be much appreciated

 

[Big Daddy]

Your system is detecting slippage and limiting the throttle response. Are you spinning the tires or trying to? If so that is the problem, turn it off and you can spin to your hearts desire. Also check and make sure you have the proper tire sizes, if someone has changed the overal ldiameter of the tires/wheels you can have problems.

 

[hippee]

i havent been trying to spin. the traction controll was ok before i got my tyres changed and i did change the size of the tyres from 185/6015 to195/50/15 can you tell me why this would cause a problem big daddy.
cheers

 

[Big Daddy]

Because your DSC system is reading the oversize of the tires as slippage. I had this happen when a tire shop mistakenly put 235 45/17's on my car intead of the 225's it came with. I do not know if your system can be adjusted to accept the newer taller tires or not, worst case you will need to revert back to the stock tire size or do a "plus one" size adjust.

 

[hippee]

does anyone know why changing the tire size will cause this problem and will i have this problem when i change to a set of 18's

 

[Big Daddy]

I just told you, your DSC is reading the larger diameter tire as slippage, you cannot increase the tire diameter. When you switch to 18inch wheels you have to plus size, which means you get a tire that is the same diameter as the original, thus the lower profile (sidewall) of the 18 inch vs the 17, etc. Read this articel from the Tire Rack. HERE

 

[Kirby]

The DSC computer basically compares each tire's actual revolutions per second and the car's indicated speed against a formula. The formula is programmed in the computer for a specific tire size. Your tire size is too small in diameter, and the computer thinks that ALL of your tires are losing traction so DSC kicks in.

www.1010tires.com has a calculator that tells you what will work or won't work. They say you should be within 3% of the factory diameter. You are 4.5% smaller. It seems like not much, but the computer is not forgiving! Common thought is that the computer CANNOT be recalibrated. Actually, it almost certainly COULD be recalibrated, but that would be a HUGE legal liability for BMW to let people recalibrate a safety system.

205/50/15 is the closest size that will be under 3%, but I'll bet they won't fit your rims.

Stock Tire - 185/60R15 New Tire - 195/50R15
Section Width:7.28 in185 mm -/- Section Width:7.67 in195 mm
Rim Diameter:15 in381 mm -/- RimDiameter:15 in381 mm
Rim Width Range:5 - 6.5 in -/- Rim Width Range:5.5 - 7 in
Overall Diameter:23.74 in602.99 mm -/- Overall Diameter:22.67 in575.81 mm
Sidewall Height:4.37 in110.99 mm -/- Sidewall Height:3.83 in97.282 mm
Radius:11.87 in301.49 mm -/- Radius:11.33 in287.78 mm
Circumference:74.58 in1894.3 mm -/- Circumference:71.21 in1808.7 mm
Revs per Mile:876.1 -/- Revs per Mile:917.5

Actual Speed:60 mph100 km/h -/- Speedometer:62.8 mph104. km/h
Speedometer Difference: 4.725% too fast
Diameter Difference: -Diameter Difference: 4.51%

 

[hippee]

cheers for your help everyone i think i will go back to the proper tyre size

 

[DSK]

Just to make an addition to what the others have said, you can have a look at;

http://www.tyresave.co.uk/choose.html

and play with the tyre size calculator to find your most suited sizes. Also there the E36 is listed as one of the common vehicles so you can see what size options are listed.