06blackonblackctsv

iTrader: (1)

After getting a speeding ticket for 81 in a 70 while having my cruise control set on 77, I took it to get the speedo checked. It was off. The place told me that they could not fix it and that I should take it to the dealer. Does anyone know how much this would be to fix or do I just have to get a tune? I have 255 45 18 rear tires, so that shouldnt make the speedo off right?

jenks40

iTrader: (3)

Yep, that's the reason...

06blackonblackctsv

iTrader: (1)

Wow, I didnt think that by going one size wider in the tire would throw it off that much.

GhettoTy

iTrader: (2)

I don't think it would throw it off by that much, but i've been wrong before. I still need to get mine adjusted since I got bigger tires.

JJSimon904

iTrader: (8)

Your speedo should read 1.3% too slow...which in this case should be under 1mph off.

A previous owner could have modified what the computer thinks the tire size should be and could make it read wrong by even more. Plus different sizes aren't always exact. You can get the same size tire but different models or even manufacturers and they can be different in actual size.

wcryan

iTrader: (2)

yeah, u shouldnt be 11MPH off..... that's ridiculous

jenks40

iTrader: (3)

well, it's 4 off, according to the op. new tires, they are the biggest they will ever be and, therefore, will make the speedo off the most amount. also, I don't believe all manufacturers are equal. a michelin may have a larger rolling diamater than a khumo of the same size, or visa versa. It is a possibility.

RADEoN

iTrader: (12)

I had 255/40/18's on the back of mine and it was off roughly 2-3 mph. I don't think the 4 mph is tooooo ridiculous.

VforMe

You can use the GPS to tell you how far off you are. It wouldn't be unheard of for a radar gun to be a little off too. This could all add up to 4 mph.

Here's this for anybody who hasn't seen it.....

http://www.miata.net/garage/tirecalc.html

garrettg

iTrader: (1)

I believe it, I have a 07 with stock sized 245/45/18's conti extreme contact dw and the speedo reads 1.5-2 mph slower than actual speed at normal highway speeds. Check it using the gps info built into the dic nav unit or with a smartphone with gps capability and speed software application.

To fix your speedo go with a tire with less height. 265/40 or 255/40 for sure would get you on the other side where your speedo reads slightly higher than actual. Otherwise a custom ecu tune can adjust if you are set on running 255/45's.

06blackonblackctsv

iTrader: (1)

Thanks guys, that gives me a good reason to go get my car tuned, lol, although the wife will probably tell me to use my math skills when I driving to figure out my speed.

RADEoN

iTrader: (12)

i don't think it'll be a constant 4 or so mph, i'm thinking it's more of a percentage based deal.

at least that's what you can tell her...

06blackonblackctsv

iTrader: (1)

Yep, thats what I am planning on telling her. She should be cool with it, because I let her drive it every now and then. When I tell her she cant drive it, she always says " I dont know why you dont want me to drive it, I am not the one who wrecked your first one".

LS2duc

iTrader: (1)

I went by one of those display cop things the other day-right on the money!
I bought a Valentine Radar Detector 15 years ago, its been upgraded 4 or 5 times-so Im into it for probably over a grand. But its saved my *** countless times! I'd say I've probably saved 3-4 grand with that unit. Massachusetts surcharge is SIX years, longest in the country! Ive even been saved from lazer when the cop shot the car in front of me-twice!! Hey if your not a speeder, not a problem. BTW that tire size will get you off in front of a judge but you MUST have paperwork from tire strore stating you changed tire size. I've seen it done before in court. I got off of a broken speedo cable on my Ducati, even showed it to the statey, wouldn't listen. Judge threw it out when I showed him repair receipt from the next day. Ticket was on 4th of July for 11 over. Good luck, but ALWAYS fight them!! Even if the cop who gave you the ticket fails to show up, you automatically win. This is court, NOT the hearing. Unless they let you off completely at the hearing, say "no, I want a trial judge. This is your constitutional right! Good luck.

06blackonblackctsv

iTrader: (1)

Thanks ls2, I showed the paper work to the judge and he dropped it to a equipment malfunction, still had to pay about $120. I also had to pay a tint ticket(I have 35% all around and you can see through all my windows but the legal limit is 50 for the front windows) and a front license plate ticket even though I got it mounted the judge didnt drop it. I really want a V1 bad, but they are illegal in VA and I cant find a place that I can mount it that will get good coverage and still not be visible from the outside, where do you have yours mounted?

RADEoN

iTrader: (12)

****** mash her in the grills.

bamacaddy

iTrader: (1)

I remember putting 38's on my first lifted truck...95 Z-71...The speedo was off like 18mph or something like that....Just did a redneck calibration by riding by a buddy on a 4-lane and him yelling how fast we were going....The damn thing was so weak by then that speeding wasn't an issue....When I met the trooper yesterday I told the wife DAMN! He got me @ 71...Sure enough mine is on the money.