96Cherokee113

Well today I was going down a local 50 MPH road and my speedo said 55 MPH. My radar went off so I slowed down to 50 MPH and the cop passed. I saw him riding his brakes so I sped up to try and lose him a little before he turned around to come get me. I cruised around 60-65 and then I saw him coming in my mirror so I proceeded to slow down, knowing I was getting pulled over. A car pulled out in front of me after that so it's not like I could go any faster than they were. I passed another cop and shortly after got pulled over. He said he originally clocked me doing 63 MPH (when my speedo said 55) and the other cop I passed clocked my doing 88 MPH (while I was driving behind the other vehicle)! Obviously there is something wrong here. I was clearly not doing 88 MPH when I was behind another vehicle. I have 235/75R15s and I know the speedo is off, but I really don't think it makes that much of a difference from stock so I doubt I was doing 63 MPH to begin with. Anyway, I got a ticket for speeding in excess of 38 MPH and Reckless driving. I have to go to court, but the cop said Reckless will most likely be dropped and the speeding ticket will be reduced. Does anybody have that link where you can compare tire sizes and see how much the speedo reading changes? That might be helpful in court along with my report card showing straight As to try and schmooze my way outta this. Just thought I'd share my story.

P.S. And I know I shouldn't be speeding and admit to being an idiot.

superj

http://www.csgnetwork.com/speedocalibcalc.html

this one works good

JSmith0055

well seeing from that speed calculator it looks like there should only be a 1 mpg diff. from stock to 235's, stock size is 225, thats not much differance at all... but just curious where can you get your speedo. calibrated?

96Cherokee113

An auto shop should be able to do it. I know it's an electrical speedo, but there should be some way to recalibrate it. Maybe adjustment of the speed sensor or new speedo gear. I usually do all my own work, but don't have the technology for this job if it requires electronic adjustment.

89Laredo

I can tell you right now, 235s make almost no difference. I regularly follow my girlfriend, she has 235s and I have 225s. Her speedometer says 55mph and I can be following her and mine will be ~50-53 1 car length behind. If I get right up and tailgate her, its at an indicated speed of 55.
She has a 96 also.

According to that speedometer calculator posted, You are going 56.1482254697286mph at an indicated speed of 55. Ive never heard of anyone getting pulled over for going 1.14mph over.

96Cherokee113

The officer claimed I was doing 63 when he originally clocked me. Then 88 when I was driving behind another car. Tell me how that's possible. And the speed limit was 50 so I would have been doing 6.14 MPH over.

96Cherokee113

Also, when I use my GPS, I notice that the speed reading from the GPS is higher than what my speedo says and I'm assuming GPS is more accurate considering it's using Latitude and Longitude to calculate the speed. My differential was rebuilt before I bought the Jeep, but I'm pretty sure the gears weren't changed so that shouldn't affect anything. Last possible idea, I changed out my gauge cluster from idiot lights to full cluster, but I don't believe that should make a difference either. What else could possibly be throwing my speedo off?

89Laredo

Yes, GPS is alot more accurate. I would go find a back road and see what it says at 55. If it does not read "63mph" then I think you have reason to believe the officer was lying..
I dont think the cluster swap would do anything. Only other reason I can think of is gears.

96Cherokee113

I really think the cop was just having an off day and wasn't happy I had a radar. The first words he said were, "Your radar works good, but not good enough. I clocked you doing 63 and you were slowing down real quick". Also, the other cop that supposedly clocked me doing 88 didn't even introduce himself, so how can I take the other cops word. And it is still impossible to do 88 while traveling a steady 4 car lengths away from a car doing 50. I guess I just have to go to court and plea not guilty.

Hommersimpson

before you or the next person guess's at this or that.. how about something real simple..on the highway.. they have things called mile markers... you can do this two ways... stop at a mile marker..push the little button on dash. and drive to next one and report back.. :} or have someone time it while your speedo is at 60...but honestly its easyer to just hit the road do 65 or what ever and hit the reset at a marker and drive 10 miles and then look what the trip says... the mile markers are with in fractions of a inch..
now to fight it in court you need to prove it..

96Cherokee113

I'll try the mile marker concept. It shouldn't be impossible to fight it in court. Chances are the cop won't show up, so how is he supposed to prove his claims. And the other officer who claims I was doing 88 never even introduced himself to me.

FrankSchmeiser

I think that if you should def get that fixed but as far as t6he ticket goes you are s.o.l. my friend even if you were not speeding you are still going to have to pay the fines ect it is truely nothing more than law enforcement "taxing" you

robertj

You're lucky he didn't get you for trying to evade him...

OverlandZJ

Sounds like there is something wrong, you need to verify your speed with a GPS.

The speedo adjustment is a speedo gear as you eluded to. 5 min job to replace. I'm wondering if work was done to the transfer before and you have the wrong gear installed.

96Cherokee113

I'm not sure if any work was done, but it is possible. My Jeep was overhauled by the PO before I got it. I have receipts for thousands of dollars in work, but there was nothing for the transfer case. Today, I'm going to test how off my speedo really is and have a buddy in the back seat take a picture of my speedometer and my GPS speed next to each other so I can bring it in for some sort of evidence. I'm not sure what speedo gear I would need though. I looked into it and it looks very simple, just one bolt and a clip.