What is speedometer calibrated to?

[nrobidoux]

Basically got myself into a big pickle with tickets.... as related to keeping my job. I got two serious traffic violations (15+ mph over the limit) that'll count against my CDL.

My question basically comes down to having brand new tires vs. tires that are worn to the bars indicating tread depth is too shallow. Yes, that difference can be enough to determine whether or not I'm under or over 15mph over the limit.

Okay I guess that really wasn't a question .... Is the speedometer calibrated to "new" tire or a "worn" tire?

I drive a '98 Saturn SC1 with the stock steal rims... R14 if I remember right. I basically have two new tires on the front end... One about 1000 miles off the other one.

Thanks.

[Ruley73]

I would think that Saturn would have erred on the side of safety and calibrated it with new tires. This way, with worn tires your speedometer will indicate faster than you are actually going. For example, with tires that are worn to the wear bars, your speedometer may indicate 55 MPH, but you may actually only going 53 MPH. If you have a tire size that is different than what came with the car, this will skew the speedometer reading too. Check the sticker in the driver door jamb to see what tire size your car would have came with.

[phipps]

Worn vs new tire is not going to give you a 15mph difference in speed.

I have different than factory tires on my Dakota and there is more of a difference than a couple mm you get with worn/new tires and my speedo is only off by 3-4 mph.

If you're legitimately off by 15mph I tend to think it's something other than tire size.

Sound like "lead footitis" to me! LOL

[nrobidoux]

Thanks guys. I'm in the oilfields of ND so doing small things like calling garages.... (or bringing your car to one LOL when you're working all the time) become much bigger tasks.

Phipps: I wasn't looking to loose 15mph ... 2mph would be enough to bring one of the tickets below 15mph over. That would mean I only have one serious violation against my CDL if I fought and lost the second ticket in court. And I could keep working as my CDL wouldn't be suspended. Basically if anyone's CDL is suspended they are terminated.

The first ticket I was a featherfoot LOL. That's what fascinated me and kept me going. I know, but it was true. I deserve that one. It's the one where I thought I was in a 70mph zone (that was 55) that I made an honest mistake.

No speeding tickets in over 10 years.... 2 in 30 days! Both over 15mph over to boot!!!

I do have non-factory tires... but they are the stock size 175/70 R14.... guess it depends on the tolerance on the "70."

Ruley: Yeah I would think the same too.... going to have to call and get a definitive answer.