2nd odometer question.

call your local jeep dealer and ask for service.. give them the vin # and they can pull all the options that the vehicle came with.

as and FYI , I found the original tire size listed with the Vin# on the inside door decal.

Thanks

JD

"There are some simple truths...And the dogs know what they are." Joseph Duemer

Ok, what's right. the door sticker list the original tire size at P215/75R15 .. When I called a local dealer and gave them the Vin# he said P225/75R15.

JD

"There are some simple truths...And the dogs know what they are." Joseph Duemer

When I got my CJ7 it had 31's on it and i swore it was reading off the wrong way. Put 33's on and it checks out with my GPS perfectly.

On our 88 Cherokee, the largest tire is supposed to be a 225. I put

I think you need to either use a GPS or find a 'measured mile' on the highway somewhere to get it right on for a base.

Mike

JD wrote:

Both.

They can be ordered with either, your VIN states the right one.

Our Cherokee label says 205, 215 and 225.

Mike

JD wrote:

The owners manual to my GPS says that the groundspeed on my GPS will not always be accurate:

"For security reasions, the U.S. Government introduces small errors(selective availability)which can affect positioning information. These errors are most noticeable while viewing speed, heading, and elevation."

Now, I know you're in Canada, but don't you guys use the same satellites as us for GPS purposes?

-- Old Crow '82 Shovelhead FLT 92" 'Pearl' '95 Jeep YJ Rio Grande ASE Certified Master Auto Tech + L1 TOMKAT, BS#133, SENS, MAMBM, DOF#51

I had thought that the US gov't had declassified the GPS offset thing. Basically that they had turned off the function that causes inaccuracies. If it's still on now...well....I've been able to get 3m accuracy which seems to me to still be pretty good. Any small warhead would still do damage if it was 3m off!! So I dunno!!

We use the same network of GPS satellites. I'm not sure of the "spacing" of them but I don't think we use the same sat in the Yukon that someone in florida uses. Isn't there like 30 sats for gps?? I know that towards the poles, sometimes there's not enough sats 'visible' to your reciever to give it a proper reading!

If you are getting 3m accuracy it is turned off. With the inaccuracies switched on it was about 50m off IIRC. Some GPS receivers support supplementary readings from (usually costal) radio transmitters which can get it down to 1.5m ; this is called DGPS (Differential GPS).

Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ

Interesting you mention that. My GPS will give me an accuracy reading according to how many satellites it is picking up. On the 401 corridor in Southern Ontario where I do my speed tests, I get 7 to 11 solid hits and the speed matches the speedometer every time I check it.

However, in one deep bush area I camp, the military uses part of it for some kind of drop training (6000' old bush airfield) and my GPS has gone insane on me twice for a couple days. Both times it reported me about

I don't know for sure, but it sure seems like someone is messing with the signal consistently in/for that area.

Mike

Selective Availability (SA) has been "turned off" since May 1st, 2000:

-John

Most of the replies talk about the speed, it's much more accruate to set it by the odometer. find a highway with mileposts, drive 10 miles (10km if you are in the northern provinces of the US LOL!) The difference between actual and your odometer is the actual % it is off. Multiply that times the number of teeth on your speedo gear to find out how many teeth you need to go up or down.

My guess is that you will be right > I bought my 2000 tj used from a broker. It came with 30x9.5 tires. Is

This appears to be the best solution as far as I can tell.

"There are some simple truths...And the dogs know what they are." Joseph Duemer

I know they can "JAM" GPS in certain areas...but it's all ground based jamming! I don't think they can skew the readings from teh actual satellites as the sats are only kicking out a timing signal. The Sats don't actually know where we are as our GPS units don't transmit back....

wonder what sort of "materials" have been left behind in some of those cold war bombing tests?!!?

My 02 TJ door label has 215 75 R 15 and it came with the 30" wheel group. (30x9.5 Tires) I would guess that it is correct. Chad

Locate a Railroad. They have measured miles. Find one that runs along a road.