Ok so today i was driving down a back country rd that there are never any cops on. Well today that was different, i passed a car that was goin 40 and i was rollin about 64 in a 55. Well i passed a cop coming at me and i got pulled over and he said he clocked me goin 75! Now my speedo in my jeep said like 64. I have 33's on my jeep but i havent had it calibrated yet. Whats the most that a 33 can change your speedo? I figured maybe 2-3 miles an hr. But definately not 11. I asked the cop about his machine and if it was up to date and he said yes i did it before i started my shift today. Im not goin to fight the ticket because i know that i was speeding but seriously 75 in a 55 in a jeep? When my speedo says 70 my **** is shaking bad. So i never go over 65, or so my speedo tells me im goin 65. But i just was wondering how much a 33in tire changes the speedo?

 

Well my XJ is 5 off with 31's so I'd say 11 off with 33's is about right...

 

yup i have 32's and i got clocked at 47 in a 35 but my speedo said 40 but i got let go..

 

yeah, that's about right. what's your gears, is it a 5 speed?
wow, that's like doing 120kph in an 90kph zone. slow the fawk down mang.

and get yourself a gps for an accurate speedo.

 

I have 33's too.


here is a good conversion chart (i made this comparing it to my GPS)
25=27
45=54
55=65
60=70/71
65=75/76
70=81
75=86/87
80=91/92
85=96/97

 

mines off 5 with 31's

 

i got pulled over once too same scenario i was on a back country road my speedo said 63, i passed a sherrif and i figured just going 63 i woulda gotten pulled over anyways, so i looked at him as he passed and he pointed at the side of the road, so i pulled right over before he even got turned around...and he clocked me at 67 with brand new 31 inch tires on my ZJ when i had it..i told him, not to get outa the ticket but just to tell him that my speedo was at 63 when he passed me and then i said i had just put brand new larger tires on the jeep that week, and he kinda looked at them and could tell they were brand new bc of the little nipple things were still on the tires, and he let me go with a warning...

i told him i had meant to run it by one of those radar trailer things that you see on the side of the road clocking people so i could see what kinda difference the tires made but hadnt had the chance and he laughed and said, well, there was your chance and i shook his hand and off we went

the point of that story was the fact, like nick said, just 31s can make a 3-4 MPH difference...so im not suprised with 33 if they made atleast an 8-9 difference

 

Gotta laugh at it a little. A block with wheels speeding....... The cop must have been bored, around here they won't even flash you unless your doing 10 over.

 

http://www.1010tires.com/TireSizeCalculator.asp

check out this link. it tells how far your speedo will be off. you'll have to punch your tire size in.

zedpapa

 

Check out the ‘conversion chart’ above. I am seeing a common theme around talking about how it is “XX MPH off.” Changing tire sizes or gears will change your speedo by a percentage of your speed, and not by a solid MPH number at any speed. A quick estimate is the percentage of size increase. If your Jeep came stock with 28’s and you have 33’s, it will be off by about 18%. At 30, you are really going 35, and at 60, you are really going 71, and so on.
It could be calibrated different, static sizes could vary, etc, so to be 100% accurate, you need to get a good GPS reading, drive by a radar display, or time a couple of miles on the freeway.

 

I have only been pulled over for going to slow... I was doing 25 in a 55 because I got air in the clutch slave cylinder and couldnt shift it very easily. I was only going 3/4ths of a mile on that road. I was taking back roads with speed limits of 30 up until then. I wasnt doing anything illegal because it wasnt a freeway so he just checked my license and off I went.

 

i would fight it just hopin that maybe the cop will lower it i got pulled over doing 69 in a 45, 24 mph over the speed limit and when i got to the court house the cop and just talked and he told me to just slow down and lowered it to 10 mph over so i would atleast give it a try only its only a couple bucks for the court cost i think mine was like $7, $7 for 14 mph ill take that anyday of the week

 

you need to change your speedo gear for what tires u hav. at least for mine and the early 90's. i have 31's i think my gear is a 32 tooth maybe. not sure about the electronic speedos though. i got pulled over for doing 69 in a 55 and i was doing 69.

 

If he has stock gearing they do not make a speedo gear with that few teeth. trust me, i have looked everywhere from dealers to speedo/tach speciality shops.

and as i posted above, those are really accurate for 33" tires. just keep that chart with you or memorize it

 

As I re-read this, it sounded like I was bagging on the conversion chart - I was actually agreeing, using it as an example of how it is not off by the same amount at different speeds. No bagging intended