SCT Tuner Question

[docs302]

I was in the process of updating my tune from AED when the custom tune screen asked about my choice of revs/mile which I assume is tire size. I am running both 18" slicks with an aspect of 680 and DOT's. I will run the slicks most of the time so I will tune to that size but how do I determine the correct revs?

 

[Grant 302]

It's best to lookup the revs/mile for your specific tire, but you can use the value from a similar diameter tire.

The Pirelli 305/680-18 is listed at 760 revs/mi.

680 is actually the nominal diameter of the tire in mm, not an aspect ratio like 30, 35, etc. So 680/25.4mm/in. = 26.77"

26.77" ~ 753 revs/mi.

I'd use 753 or 760 without the published value from the mfg. Otherwise calculate it using the exact circumference of your tires.

 

[docs302]

Wow that's great.....thanks Grant. Learned something new about slicks. I will try the programming again and see if this works.

 

[gtorpedo]

In my experience on the S550, regardless of what you input on the SCT for revs/mile it doesn’t actually fix the speedo.


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[docs302]

Honestly, I probably shouldn't really be that concerned. I will mainly be using the Boss on the track so the speedo is really not relevant.

 

[Mad Hatter]

Actually in can be pretty useful when comparing videos etc after changes to the car..

 

[docs302]

Actually in can be pretty useful when comparing videos etc after changes to the car..

If I ever get to that point I will look at all the details but I just need to get my ass out on the track before it's winter again!