Hi again. I'm about to get a set of dunlop's and this will be my 3 rd different tire size. Here is the scoop. I originally ran stock 235-75/r15 tires, then 225/60/16 tires which i had calibrated on my bamachip programer by doug, and now I'm getting 255/60/17 tires that arn't calibrated yet on my programmer.

Now, I contacted Doug and asked if my speedometer is going to be really screwed up and he replied saying use www.1010tires.com. On there, I will be able to find out my change is on my new tires. And sure enough it did, but I need you fellow members to help me figure out how to read the following that i copied.

Stock Tire - 235/75R15

Actual Speed: 60 mph



Tire 1 - 225/60R16

Speedometer1: 65.0 mph

Speedometer Difference: 8.453% too fast

Diameter Difference: 7.8%

Tire 2 - 255/60R17

Speedometer2: 59.6 mph

Speedometer Difference: 0.586% too slow

Diameter Difference: 0.59%

So, with my new tires(255/60/17) do i need to go faster or slower from my LAST set of tires(225/60/16)?

Thanks:
Matt

 

Faster, but not by much....by .4mph lol

 

After changing from replacement tire 1 to replacement tire 2, your speedometer will read lower/slower than actual. In other words, when you see 59.6 on your speedometer after the change, you will actually be traveling at 65 MPH - a good way to set yourself up for a speeding ticket.

Interestingly enough, replacement tire 2 is almost exactly the same diameter as your original stock 235/75R15s. So, you would need to go back to the factory setting that you had before Doug adjusted it for replacement tire 1.

 

what programmer do you have?

 

I think he has xcal2...but lost it

haha, not good

 

i have the old bama programmer, the blue plug and play one.
i have the 225/60/16 on my current setting now, then i lost the programmer, so for now, i'm stuck on this setting.

well, what i did was put the 225/60/16 size as my stock setting, then typed in 255/60/17 as my "Tire 1". And its telling me this.

Stock Tire - 225/60R16

Actual Speed: 60 mph


Tire 1 - 255/60R17

Speedometer1: 55.0 mph

Speedometer Difference: 9.089% too slow

Diameter Difference: 8.34%

So, i think i found my answer.

 

Correct.