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jchahn 01-22-2004 09:26 PM

Simple question:
When bigger tires or a lift kit is put on a vehicle, it throws the speedometer off. How is this corrected?

Shorts 01-22-2004 09:45 PM

Re: Speedometer
you gotta adjust the vehicle speed sensor reading. get a TruSpeed.

u4ia4 01-22-2004 10:52 PM

Re: Speedometer
another option is to crunch the number and figure out the appropriate gear ratio and re-gear. the simplest and cheapest method is the truspeed way.

i have 35s and re-geard so the speedo is off by less than one percent, but i run 31s in the winter so the spedo is off by about 13%. i just drew dashes on my speedo at 35, 55, and 70MPH just to give me an idea in the winter.

MSF 01-23-2004 01:41 AM

Re: Speedometer
New tire size / old tire size x the speed your speedometer says = actual speed.

That's how I figure mine. I just do the math while I drive, 90% efficient, so 30 is 27, 50 is 45, and so and and so forth. Of course you have to factor in gear changes too. And yes, it would be much easier to get a truspeed, but that costs money. [img]images/graemlins/smile.gif[/img]

J.R. 01-23-2004 07:43 AM

Re: Speedometer
Last time I posed this question to a dealer they said that you could have the speedo recalibrated. When I said "Great! When can I come in?", they said "Oh, we don't do that here; you can take it to a speedo shop to have it done".

I never bothered, since the only calibrating shop I knew in the area was sort of shady and/or already out of business...

Ken_Loyd 01-23-2004 07:57 AM

Re: Speedometer
Hello Folks,

Over at Randy's Ring & Pinion website has a bunch of equations to figure the ratio's out. And etc...

u4ia4 01-23-2004 10:53 AM

Re: Speedometer has some good calculatorsa as well

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