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Speedo Correction with 22's??

2611 Views 3 Replies 2 Participants Last post by  92TripleBlack
Has anybody fixed their Speedometer to correct for the large 22's you have installed?

If so how did you do it?
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Not available yet. BTW, the rim size is meaningless. Its the outer tire size that counts. You could very well have 22s and still have 33" tires, so no speedo correction. You also could have 17s with 37" tires and need a large correction. Most 22s people have are approximately standard diameter. ;)
What is concedered a "Standard" size tire? Wouldnt it depened on the persons taste?
Rollin-on-Dubs said:
What is concedered a "Standard" size tire? Wouldnt it depened on the persons taste?
No. "Standard" tire size is the outer diameter of the stock tire. You are asking questions about the rim size which doesn't dictate the tire size.

Let me put it in easy terms.
Explanation : If you get 18" rims with tires that are high profile, the overall diameter of the rim/tire combo may be larger than stock. 18" rims with regular profile would have the same overall diameter. Low profile tires are probablly going to result in smaller overall diameters.

Stock rims and tires are 18x8 rims, 265-70-18 tires.
This means the tire width is 265, tire height is 70% x 2 the tire width, and then add 18" for the width of the rim to get the outer diameter.
265-70-18 overall diameter is 265x0.7x2/25+18=32.84"

The /25 converts millimeters to inches.
I have 305-55-20 tires on 20x10 rims.
My calculation is 305x0.55x2/25+20=33.42 so my tires are larger diameter than stock and would require a speedo change. My tires rotate slower than stock because they are larger. This means if you are going 60, it will read about 58

If I chose 305-50-20 tires however and kept the same rims,
my new calc is 305x0.5x2/25+20=32.2"
These tires rotate faster than stock because they are smaller. This means if you are going 60 it will be reading about 61.

Both examples use the same rim, but now I would have to adjust the speedo down instead of up.

The rim size is meaningless. You could put 22s on and not need to change the speedo depending on the tire size. The tire size dictates if you are going to need to change your speedo. This is why I posted what tire are you looking at? The outer diameter of the tires, not rims, dictate the speedo change. :crikey:
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