possible speed sensor?
 

hello guys, hopefully you can be my saving grace.

2002 f4i, now unlike all the answers i have found in the search function i can not find one to reflect my situation.

my speed sensor DOES work, but it is very inaccurate, il be doing 40 and it will display 27.

the sprockets both front and back are standard sizes so it rules out the gearing.

i have heard of these speedohealers, but that appears to be for gearing correction.

i have removed the sensor, cleaned it, cleaned connections, cleaned connection on back of clocks, checked fuses the lot.

does this still sound like it is the speed sensor to you guys?

i found found a few sites that sell them using one of the stickys but could you point me in the direction of the cheapest? i am in england so postage will differ slightly.

kindest regards
james

nobody?