I was wondering now that I put 20's on my car if the speedometer would be off a little bit? If so how much, anyone know anything about this? I will post pics as soon as my other rim comes, I received 3 rims today and the 4th will be comming tommarow.

 

it throws it off, but how much i dont know, or if its in a positive or negative direction. dont think its that much to worry about
anyways

 

I was thinking the same.. I hope its only a few miles off. Thanks tho.

 

Go to one of the tire dealer websites and get the revs per mile for your old and new tire size.

Once you have those it's you can see how much bigger or smaller the new tires are and can calculate the speedometer change.

 

This tire calculator can be pretty helpful. With 20's, pretty much any tire you put on it will still lower your speedometer and odometer compared to actual speed and distance. Hope this helps

 

Stock Tire - 235/50R17 >Search Tires Tire 1 - 225/35R20 >Search Tires
Section Width: 9.25 in 235 mm
Section Width: 8.85 in 225 mm

Rim Diameter: 17 in 431.8 mm
Rim Diameter: 20 in 508 mm

Rim Width Range: 6.5 - 8.5 in
Rim Width Range: 7.5 - 9 in

Overall Diameter: 26.25 in 666.75 mm
Overall Diameter: 26.20 in 665.48 mm

Sidewall Height: 4.62 in 117.34 mm
Sidewall Height: 3.10 in 78.74 mm

Radius: 13.12 in 333.24 mm
Radius: 13.10 in 332.74 mm

Circumference: 82.46 in 2094.4 mm
Circumference: 82.30 in 2090.4 mm

Revs per Mile: 792.3
Revs per Mile: 793.8

Actual Speed: 60 mph 100 km/h
Speedometer1: 60.1 mph 100. km/h

Speedometer Difference: - Speedometer Difference: 0.189% too fast
Diameter Difference: - Diameter Difference: 0.2%

Thats it huh... Wow i was expecting much more difference. Anyways, thanks for the help guys

 

Umm.....stock tires are 215-50-17

 

I saw that too

Really your new setup is going to show 4% slower than stock.
When your speedo reads 60 your actually going 62.4

 

i guess the ultimate test would be to drive next to a stock car at different speeds and compare...

 

Actually math is the ultimate test.......

 

Not really cause all cars are off by some degree & are different from car to car.

My explorer has bigger tires & says it reads 6% off. Radar station says up to 45 it's accurate, after that it gets off by almost 5mph too slow.

 

It looks like 235/30's work pretty well, if they'll fit your rim.


Stock Tire - 215/50R17 >Search Tires Tire 1 - 235/30R20 >Search Tires
Section Width: 8.46 in 215 mm
Section Width: 9.25 in 235 mm

Rim Diameter: 17 in 431.8 mm
Rim Diameter: 20 in 508 mm

Rim Width Range: 6 - 7.5 in
Rim Width Range: Unrecognized tire size.

Overall Diameter: 25.46 in 646.68 mm
Overall Diameter: 25.55 in 648.97 mm

Sidewall Height: 4.23 in 107.44 mm
Sidewall Height: 2.77 in 70.358 mm

Radius: 12.73 in 323.34 mm
Radius: 12.77 in 324.35 mm

Circumference: 79.98 in 2031.4 mm
Circumference: 80.26 in 2038.6 mm

Revs per Mile: 816.9
Revs per Mile: 814.0

Actual Speed: 60 mph 100 km/h
Speedometer1: 59.7 mph 99.6 km/h

Speedometer Difference: - Speedometer Difference: 0.356% too slow
Diameter Difference: - Diameter Difference: 0.36%

 

lol thanks for correcting tire size...Sorry i was kinda baked when I posted.. The tires fit nice, slight rubbing when going over big bumps in the back but nothing too bad. Thanks everyone.