speedometer question?

[1000_eyez]

My speedometer is 5 miles off. I have to go 5 miles faster to go the speed limit. The car is a 89 535i manual 5 speed. Anyone have any suggestions on what it could be...? Thanks.

[Dick Schneiders]

and the computer not being recalibrated for the new size, or simply the normal built-in difference that most BMW's are designed to have. What I recall reading, and seeing in my cars, is that the speedometers are designed to read 5 to 7% faster than the car is actually travelling. 5 mph is a bit much for this alone - I usually see about 3 mph or so on my cars. I don't know if the computer in the 89 535 can be adjusted for tire size.

My speedometer is 5 miles off. I have to go 5 miles faster to go the speed limit. The car is a 89 535i manual 5 speed. Anyone have any suggestions on what it could be...? Thanks.

[632 Regal]

and the computer not being recalibrated for the new size, or simply the normal built-in difference that most BMW's are designed to have. What I recall reading, and seeing in my cars, is that the speedometers are designed to read 5 to 7% faster than the car is actually travelling. 5 mph is a bit much for this alone - I usually see about 3 mph or so on my cars. I don't know if the computer in the 89 535 can be adjusted for tire size.

[1000_eyez]

thats how I know...and following traffic but everyone seems to speed anyways. I ran by one of those radar boxes and it said I was 5 miles under. Maybe it's nothing. The tires are the size it calls for. I don't think it's the tires. Anyways, I should ask a cop to check how fast I'm going. My wife has done that before because the truck she was driving had 35" tires. She had no idea what speed she was going. The cop told her it's 10 miles off. Thanks.

[1000_eyez]

nice cars! Thanks for the info.

[Dick Schneiders]

I only drive my cars under 65mph.

[Phil Sanderson]

...but 5/60 = 8% and I always drive right on the speed limit - I think, but that didn't stop the $130 fine I recieved last week from a roadside camera, for doing 82kph in a 70kph zone (I'm a bad boy!)

I only drive my cars under 65mph.

[Dick Schneiders]

Perhaps tonight I will really let the 740 fly and get it up to 70mph. :-)

...but 5/60 = 8% and I always drive right on the speed limit - I think, but that didn't stop the $130 fine I recieved last week from a roadside camera, for doing 82kph in a 70kph zone (I'm a bad boy!)

[Phil Sanderson]

are exactly 8% fast - i.e. at 100 k.p.h indicated speed i'm actually doing 92 k.p.h. These figures were obtained over a measured (signposts on the side of the freeway) 5 kilometres - it takes 3 minutes to travel 5 kilometres at 100kph. My figures are the same as yours 100kph = 62mph and 92kph = 57mph (close enough) so my speedo is 5mph over. I'ts normal for these cars.

I'm no expert but seeing as both the speed sensor in the diff. and the speedo itself are electronic it may be a difficult thing to recalibrate the actual speedo readout to be spot on exact.

I've always thought that knowing exactly what the error is is a good thing because it means the in say a 60mph sreed zone I can do say 65mph and still be legal.

p.s. the error in my 525i has not changed the slightest amount in my 13 years of checking it (which I do all the time).

hope this helps
Phil

[Dan in NZ]

You can use the OBC to change the speedo correction factor. I've lost the link now, but I think gale's page had a section on the obc's hidden functions, and a formula to use for correcting the speedo.