i dropped my tire size from stock to 215 50 R15's. right now my speedo is off 1.1:1. so if i'm goin 100 on the speedo, i'm really goin 90, 50mph is really 45. how do i recalibrate teh speedo, i know some GM's just have the tire size plugged into the computer, and old jeeps have a gear. anyone know how to fix it on a 92 SE?

 

I guess you'd have to splice in a variable resistor into the speed sensor's output. However its the analog speedo that is inaccurate. With out a radar gun or someone with a calibrated speedo how are you gonna adjust it. Call it good forunte because your speeding tickets will be for alot less than normal. Plus you should get more acceleration due to shorter gearing.

 

defenitely noticed more acceleration, but hurtin on speeding. I just keep the speedo just above 80 on the highway. thats like 73 or so.

 

Some of the major car dealers have machines to check how far off your car is at different speeds in incriments of 10mph all the way up through 80. Only one shop in my area will do it and it cost $50 just to get it checked. Call your local major car dealerships, I think this one was a Chevy dealership, it's been a while. They should be able to tell you how to fix it or what needs to be done.

 

Just do it the redneck way and use some white-out to rewrite the numbers on the speedo.
hehe
stuff like this is best left to the dealer.. when they get done griping at you for changing your tires from the recommended size, they'll charge about an hour's worth of labor and should be able to calibrate it correctly.
some tire/wheel places that offer on-the-car tire balancing should also be able to do it, as the same equipment can be used to check the speedo.