I recently bought a 2005 f150 super crew that had aftermarket 20" rims and larger tires...then i got a ticket for speeding when my cruise was set on the speed limit. The cop said I was going 76, when my speedometer said 65. Is it normal to be off 11MPH when going 2" larger in the wheels with bigger tires? I'm going to fight this in court, but need this information first.

 

Uh no! The max I have ever seen off was 4-5 MPH on trucks with larger wheels and tires.
I only have 18" wheels with 285/65R18 tires and was checked by local PD to be only 2 MPH
off at 50 MPH. I would definitely go to court and have them prove their case.

Now in saying that your speedometer could be off so I would go in to a dealership and have
it checked and get a report from it.

 

Just some advice. Your speedometer being off is not gonna get you out of a ticket.
How much your speedo is off depends on how much taller your current tires are than the oem tires. For instance on my Screw, it came with 30 inch tall tires. I went to 33 inch tires and my speedo was off 5mph at 60mph. The faster you are going, the more it will be off.

 

Especially not with the state law in nac brother. I tried twice while I lived there and neither time worked. Granted mine was for seat belt tickets but its awfully difficult to overturn a cops word against yours.

 

They are going to go by what the cop says he radar'd you with. If you claim your speedometer is off, then here in TX I have seen them then claim your vehicle unfit and unsafe for proper driving and will give you another ticket on top of that.

Look at your driver side door area and tell us what the factory size tires were on the sticker in there and then tell us what size you have now.

When i bought my truck it had much bigger than factory size tires on there to begin with and the speedo had not been adjusted. The speed was off by almost 11% across the board. So at 20-30 mph it didn't matter much because that will only be off by 2 or 3 mph. But at 70, your speedo says 70 and you are doing 77 or more. Big no no there.

I wouldn't fight the ticket in fear of them doing worse to you and just get it adjusted properly. Keep in mind also that your odometer is now wrong too, which is also a big problem too over time. The next owner of the truck would be getting a vehicle with more miles than what you are selling it with which isn't the best idea to deceive anyone like that.

 

I agree with the responses here. You're probably fighting a losing battle.
Were you paced, or hit with radar? If radar, you have less of a chance of beating it than being paced - but there are different paths to take to fight each.

In either event, I'd say save your time and just pay the ticket. When it comes down to it, unless you can prove that you were not speeding, you'll likely be found guilty - despite the reason for speeding.

Now - with that said:
If you have proof that your speedo was off considerably (~11 mph), you may be able to plea "guilty with an explanation" (In NJ you can) and show proof, and also that the situation has been corrected - you may be able to plea to a lesser offense or reduced fine. Think about it - you were still speeding (guilty) - but have a reasonable explanation for the offense (speedo improperly calculated - unknown to you). Prosecution may argue that you should have been able to estimate that you were going considerable faster than 65 mph. You want a sure fire way to get your actual speed? Got a GPS?

If you're looking at a 4 pt ticket for x mph over the limit, you may be able to talk to the prosecutor and get it down to a 2 pt ticket. If he/she is in a really good mood, you may be able to negotiate an non-moving violation.