GOT PULLED OVER FOR SPEEDING: COP SAYS BAD SPEEDOMETER DUE TO BAD CHIP

[MattStarr]

Ok, I'm coming home from studying at my friend's dorm. On the way out of the parking lot I pass a cop who has his windows up, he says I was playing my STOCK stereo too loud. So he turns around and follows me back to my dorm down the main road which is 45mph. I see him behind me so I make sure to do the speedlimit. I'm doing 45mph (according to my speedometer), he says I was doing closer to 55!!! I told the officer that I saw him behind me and I was making sure to do the speedlimit. He said my speedometer was off due to possibly worn tires or not stock size. I have the stock tire size which is LT235/75R15. There is about 30% of the tread left. Then he says that I might also have a bad chip and that Ford is notorius for that. Please help me. He said I should take it to ford and get it checked out. He was nice about the whole thing and it turned out he was from my home town. He let me off and I made sure to thank him.

Funny thing is he didnt say anything about my brushguard which obstructs my headlights, or my tailight guards which block my tailights or my tinted windows. I looked in the mirror when he was walking up to the car and I saw him touch my tailight guards with his hand. He grabbed them!!

So... Can someone please tell me why this speedometer is messed up?? Thanks guys

 

[Redrig]

maybe he suspected something and just wanted to pull you over to check you out.... i never heard of a chip causing that. but it could be i guess.

 

[MattStarr]

Maybe he thought I was a punk kid that was drunk or stoned..... Thats what section525 suggested, then he had nothing to go on, so the cop let me go???

 

[Redrig]

yep thats what im thinking

 

[Commtech]

I understand that speedometers are never accurate from the factory. You can go to the shop and get it calabrated if you want to spend a few bucks. I have done it before to have a speeding ticket reduced (I was running 16" rims on my F150 that came with stock 15"ers). Or you could drive on the interstate for several miles and check your odometer against the mile markers on the side of the highway (I would suggest at LEAST 10 miles). If you match mile for mile at the end of the trip then you are close, If you are off, then measure the distance and do a little math to figure the percentage off and apply that to the speedometer.
What you also could have done is ask the cop to calabrate his radar unit. They have a tuning fork they use to calibrate the unit, and if he is giving you a ticket, he is required to tune it if asked. If it is off then you have a good shot in court of having the radar reading not used as evidence. BUT, chances of it being wrong are slim.
Hope this helps you........

 

[MattStarr]

Ok... anyone else have any ideas about the chip or tires??

 

[MattStarr]

Luckily he didnt give me a ticket. Since I was coming out of a college dorm blaring my music, he probably thought he could get me for DUI or drugs or something. Theres no way it could be off by 10mph b/c the speedometer is gear driven and not computer.

 

[Commtech]

OH, also.... He put his hand on the back of your truck to put his finger prints on it. If you did something illegal like run away, drive over him etc. they would have a positive ID on you by recovering the truck and finger prints. Safety precaution for the cop there, as he has no idea what you are going to do. I was stopped once on my motorcycle and the cop put his finger prints on my back fender, and kept the bike between us all the time.

 

[MattStarr]

Oh yeah, I remember hearing that somewhere, thats smart on their part. So... to all cop killers out there.... Wash the back of your truck so you dont get caught

 

[Alec]

If anything most factory speedo's read fast, not 10 mph slow. Do the highway mileage check as stated above, may reveal something. It also may be his speedo or radar gun that's off, ask him for the calibration certificate

Besides, your 97's speedo is gear controlled, not computer: therefore you could fix it with a gear instead of mucking with the computer, or could have a wrong gear.

 

[MattStarr]

Im not going to worry about it. I think it was racial profiling!!! j/k

 

[Hokie]

Ummm... worn tires (smaller) will make your speedo read fast, not slow. With my 32's my speedo is off around 6% which makes basically no difference until 55 MPH

So, in that situation... My speedo reading 45 means i'm going 48.. whooopdee... he was trying to catch you for something else and came up empty handed. And the system too loud is crap. No stock system can play loud enough to break noise ordinances. And they have to use a meter from like 50 ft away before they can bust you for that.

 

[meathd420]

I just bought my explorer back in March......

my dad is a mechanic and he told me the first time he ever drove it he could tell that mine speedometer was off so he just did the highway thing like Commtech mentioned and told me that it reads about 5mph under.

He also told me it is a big PITA to fix it so just deal with it, and always keep in mind when driving it that i'm going 5mph over what the speedometer says .........lol

so that is what I've been doing and haven't gotten pulled over yet...lol....(knock on wood)

BTW - I also run on the stock size tires.

 

[MattStarr]

hokie~ i told the cop that in VA we have a law that says you have to be able to hear the music from 50ft away. He said that in SC if they can hear it outside your car its illegal. I was playing Lil jon and the eastside boys "get low"... its got some from my stock system!!

 

[Hokie]

Originally posted by MattStarr
hokie~ i told the cop that in VA we have a law that says you have to be able to hear the music from 50ft away. He said that in SC if they can hear it outside your car its illegal. I was playing Lil jon and the eastside boys "get low"... its got some from my stock system!!

But wait.. I can hear the cop's high and low band dispatch radios from outside of the car when I walk by.. they must be illegal too right?

You got off, don't worry about it.. he was being a d!ck and came up empty handed and tried to save face by making himself sound smart.

 

[Alec]

BTW, it's not a PITA to fix it:

$7 and 10 minutes.

Originally posted by meathd420
I just bought my explorer back in March......

my dad is a mechanic and he told me the first time he ever drove it he could tell that mine speedometer was off so he just did the highway thing like Commtech mentioned and told me that it reads about 5mph under.

He also told me it is a big PITA to fix it so just deal with it, and always keep in mind when driving it that i'm going 5mph over what the speedometer says .........lol

so that is what I've been doing and haven't gotten pulled over yet...lol....(knock on wood)

BTW - I also run on the stock size tires.

 

[meathd420]

Originally posted by Alec
BTW, it's not a PITA to fix it:

ok if it's not a PITA then you tell me how to fix it..........

 

[Alec]

Your tranny (or tcase) has a speedo gear. Each size up slows the speedo by 5mph, each size down speeds it up by 5mph (at 65-70). I think, I may be thinking backwards

Anyway, get the right gear from Ford and you're fixed, depends on the gear you have now. There are many threads and a few tech articles on the speedo gear, use the search engine and also check out the main explorer4x4.com page.

 

[Cyclepsycho]

Do you have a GPS? If not, find one of your friends who does and borrow it.
Then check the speedometer against the GPS. I've found my GPS to be very accurate and use it to determine the accuracy of the speedometers of the motorcycles I work on (which can really vary wildly).
If it checks out, then the cop was just fishing (and lying). If it's off, then you either need to determine what is causing it to be off or just know how far off it is and drive accordingly.

 

[IAmTodd]

BTW- You mentioned you have worn tires, meaning that they are smaller than they are new, meaning that you speedo will read faster than what you are actually going, so your speedo must be really off! Or he was just making it up!