I will be changing wheels and tires this weekend. Going from 275/55/20 to 285/70/17.

My 5star tunes via x4 are all setup for the 275/55/20 tires. Where do I adjust this in my tuner?

Also, I use the 87p/t and on the same long downhill run coming home on I-75, with cruise set, it feels like the transmission is undecided whether to engine brake or coast. It's almost like a slow shutter where it's going to back and forth between coast and engine braking. When I cancel the cruise it stops and coasts. I'm sure this is something to do with engine braking when towing but I'd like to adjust this if possible.

Is there a setting or do I need to get another tune?

 

X4 User Manual for how to enter TS adjustments: https://www.sctflash.com/support

Call 5Star fer ANY other tuning adjustments - you paid for that privilege. Don't try to mess with it yerself via end-user adjustments if you don't know what yer doing. It's a Custom tune - you'll only make it worse.

MGD

 

You also have to know the number of tire rotations your tires make in a mile. It is not going to ask you the size of the tire. It is going to ask you how many rotations per mile.

 

Good to know, www.tiresize.com shows me this info

 

It does, but be prepared for it to be wrong and have to make adjustments multiple times. As an example, that site and others say that my 305/55/20's go 601 revs/mile. If I go to Toyo's website, it says 625. I tried 601 and was no where near correct. 625 is perfect. Most manufacturers will list those specs on their own sites as well. Not a bad idea to check.