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over size wheels messing with speedometer help!

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Old 05-03-2006 | 11:32 PM
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Default over size wheels messing with speedometer help!

OK i know you guys on here never like this but i put 20's on my car. The day i put them on i had my cruise control set at 73 in a 65 and cop pulled me over and gave me a ticket for 79. so i was wandering how do i fix my speedometer for having the bigger wheels and tires. any help is appreciated guys
Old 05-03-2006 | 11:53 PM
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you have to get some tuning software like hp tuners or efi live and reprogram your tire diameter.
Old 05-04-2006 | 12:10 AM
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will a hypertech programmer do this? for this big of a wheel and tire?
Old 05-04-2006 | 01:20 AM
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Most people get rid of their 20's when this happens. j/k man, I think that a Hypertech might be able to solve your problem.
Old 05-04-2006 | 01:28 AM
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i honestly kinda regret it because i lost a lot of power but i like the looks so i will have to make up the power somehow.... how can i find out for sure if the programmer will work
Old 05-04-2006 | 11:27 AM
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I just had my speedo corrected for the 4.10's. About any hand held programer would make it right for you or, if you know someone with a LS1 Edit, they could correct it as well. Until then, look here- http://www.f-body.org/gears/ enter the info and print the results out and keep it with you when you're driving ( you'll be using your tach to gauge your speed ) and that might keep you from getting another ticket.
Old 05-04-2006 | 11:45 AM
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20's don't mess with your speedo. tire size does though. you should be running a 285/30/20 and it is 26.7" high, the same as STOCK.
Old 05-04-2006 | 02:00 PM
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i got a FREE tune.... ALWAYS stay 7-8 miles below the speed limit and you'll be FINE!!
Old 05-04-2006 | 03:14 PM
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hmmm...wouldn't the bigger tires/wheels make the speedo read more than your actual speed?

Our cars came stock with P245/55/16's right? So if you put P275/20/20's on when your speedo says 71 you would only actually be doing 65 right? If so your speedo may have been changed by someone else before you got your car cause your numbers don't seem to compute. Or maybe I'm just not thinking correctly which is always possible.

EDIT: After checking the tire Calc. I'm wrong sorry. I had it backwards.

Last edited by Mike02Z; 05-04-2006 at 04:51 PM.
Old 05-04-2006 | 04:35 PM
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Man i really dont know. i know that my tire size is 255/35/zr20. and i know that i got the ticket for doing 79 when my speed was set on cruise control at 73. thats pretty much all i know. that and that i need to get it fixed haha
Old 05-04-2006 | 04:40 PM
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Your tires are too big . . . use the tire calculator:

http://www.discounttiredirect.com/di...foTireMath.jsp

The stickies are there for a reason . . .

The Hypertech will adjust for over sized tires and gear changes . . . that is about all it is good for
Old 05-04-2006 | 04:40 PM
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must have given you a ticket for the wheels, lol


don't waste your money on a hand held, get hp tune or pay to have it recalibrated.
Old 05-04-2006 | 05:50 PM
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and where would i get that done at i live in sedalia missouri anyone know?
Old 05-04-2006 | 05:51 PM
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and more importantly whats the gonna cost
Old 05-04-2006 | 06:40 PM
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PM sent - I would post up on the local fbody board and see if someone there can help you out.
Old 05-05-2006 | 02:12 AM
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thanks man




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