Speedometer after putting on larger tires

[Hedsic]

I'm just curious if anyone knows what the difference the speedometer would read when upgrading tires to 245/75R16?

I had your typical 235/70R16 stock. Just got curious to know how off my speedometer probably is after changing to the 245's Would it just be a couple mph off in general or would it make a rather huge different?

(just asking because now I take the interstate to work for my new job and they put in speed camera's along the interstate. Would hate to get hit with one of those in the mail)

 

[John3seventeen]

I'm just curious if anyone knows what the difference the speedometer would read when upgrading tires to 245/75R16?

I had your typical 235/70R16 stock. Just got curious to know how off my speedometer probably is after changing to the 245's Would it just be a couple mph off in general or would it make a rather huge different?

(just asking but now I take the interstate to work for my new job and they put in speed camera's along the interstate. Would hate to get hit with one of those in the mail)

Depends on tire diameter, my 245/75/16's are around 30.25" and my speedo is off between 2 - 3 mph at 65. I used my GPS to check it.

 

[Hedsic]

mine are listed at 30.75 but I was told they was probably a bit bigger.. Hmmm good to know though.

Yeah I don't even have a GPS. Here in Iowa I think it'd be impossible for me to get lost to where I'd even need it.

 

[Luke]

Try this Bub ..
Speedometer Calibration Calculator And Information

 

[u2slow]

I'm running that size. Based on those road-side radar signs it is bang on. Speedo must have been reading high with the factory tires.

 

[Luke]

I think those things are set low ... we have one around here and it says mine is dead on too... but I know it's not.

 

[Wulfhound]

Try this Bub ..
Speedometer Calibration Calculator And Information

that calibration calc is cool but it doesn't have 31x10.5 15's on there it's all metric :shakehead:

 

[Wulfhound]

I'm running that size. Based on those road-side radar signs it is bang on. Speedo must have been reading high with the factory tires.

the speedos in so cal say im about 5-7 mph over

 

[Luke]

it's all metric :shakehead:

What else is there? ... Eh

 

[VAhlene]

I think those things are set low ... we have one around here and it says mine is dead on too... but I know it's not.

I actually maintain these signs as part of my Job. I work for the town in the sign, signals and marking dept. There is no way to set it slow, at least with ours, its hooked up to a radar gun that is hooked up to a small computer that calibrates everything and is very accurate. you can however change at what speed it flashes and shuts off. Ours shut off after a certain speed so people don't see how fast they can get their vehicle to go.

 

[HoosierJeeper]

Comparing to GPS, with 245/70/17 (same as 245/75/16), mine reads about 2 over what it really is, which is fine with me...rather it be that then vise versa. Ex: Jeep says I'm going 70, GPS says 68.

 

[Luke]

I actually maintain these signs as part of my Job. I work for the town in the sign, signals and marking dept. There is no way to set it slow, at least with ours, its hooked up to a radar gun that is hooked up to a small computer that calibrates everything and is very accurate.

Now that I think about it ...and taking your expertise into account, it must be that they are usually set in relatively low speed areas. At low speed the offset (from actual speed) would be very small.

 

[Wulfhound]

What else is there? ... Eh

here in America atriot: metric is to complicated for us to many big numbers :happy175::happy175:

 

[TheBlueKJ]

here in America atriot: metric is to complicated for us to many big numbers :happy175::happy175:

Lol I actually like metric over SAE since it's easier. 1KM=1000m 1m=100cm or 1000mm unlike 1mi=5280ft 1yd=3ft 1ft=12in

 

[Luke]

Lol I actually like metric over SAE since it's easier. 1KM=1000m 1m=100cm or 1000mm unlike 1mi=5280ft 1yd=3ft 1ft=12in

That's how they sold it to us ... and the rest of the world *cough*


...actually I was right on the bubble of the change I learned both in school.