Recently changed tire size. Can we change this under the opt parm setting on the xcal2? Never been in there and just wondering.. Also, my shifts have gotton a bit soft, due to my lazy driving, wouldn't mind firming them up, and not just for WOT, has anyone adjusted firmness here? Been trying to get dyno time at TP and I'm sure Mike would take care of these but just wondering if anyone else has done any end user minor adjustments with the xcal2.

Been using the search tool here for what we can do under the Extreme Tune software, I see adjustments available under here but looks like we need .xtr files for this so hoping there are simple adjustments on the xcal2 unit itself for these. thanks

 

You can do it under the Opt Parameters menu. You just need to know the revolutions per mile number, which you can get from the tire spec sheet. You can only select in increments of 5, so pick the closest one. My new BFG AT 285/65-18 rev/mile nubmer if 636, so I used 635 as the new adjustment number.

 

Thanks mewaschuk - I'll have to look that up on the BFG site first. Can you adjust shift pressure as well? I'll have to check my TP doc's I got with the xcal to see what else is in there before going back to stock and reloading tune.

 

Exactly, adjust the tire size in terms of the revs per mile.

Now some tire manufacturers do not release that info, so one way to get that number is to take actual tire height and divide that into 20,800.

For example, say a tire is 34.8" tall - well, you simply take 20,800 and divide that by 34.8 and get a revs per spec of 597.7 - so you plug in either 595 or 600, since it;s in 5 rpm (revs per mile) increments.

Now there are some who say that formula is 20,850 instead of 20,800 - to each their own. You can easily play with it using a GPS to get it close.

Now one other thing to remember is that truck tires are generally rating in terms of their revs per mile spec at 45 mph - remember that the revs per mile is NOT going to stay the same at all speeds, the faster you go the more tire growth you get.

Good luck!

 

Mike I just sent in my worksheets for the xcal II and I put the tire size down I think, but will you adjust for the speedometer when you tune it or will I need to do it when I get everything? Tire size is 295/75/16, in case I didn't include it.

 

Hi mlsman23,

On those CPW's. there is a section where it asks you if you need the speedometer recalibrated - if you answer "Yes" to that, then we look at your tire size & gear ratio information. You will notice that we ask for your original gear ratio, your new gear ratio, and then your original tire size, as well as your new tire size.

The way this works is, even if you change only the tire size, we still need to know the correct gear ratio, because the area inside the PCM where we make those changes contains a "switch" to make it active - and once we turn that switch on so that we can recalibrate the speedo, then we have to enter BOTH the gear ratio *and* the tire size, even if only one of them has been change,d that is just how that area of the PCM works.

If you are not sure how you filled your info out, just take a look at your copy - if you need to make any corrections, you will need to send us that info, and it's best to do that by calling, so that you speak to a person who will go into that pile of CPW's and pull yours out, and make the appropriate changes so that it gets done right.

So the short answer to your question is, if you answer "Yes' to the question of do you need your speedometer recalibrated on our forms, then yes, we do that for you, so that you do not have to do that yourself. From there, if you ever make any *further* changes in gear ratio or tire size, you can simply plug that in yourself using the XCalibrator.

I hope that answers your question, & give us a quick call if you need to make changes - and don't' be surprised if they ask you to also send us an email, so that we have this documented form you in writing, which we attach to the file. We don't mean to put you thru a lot of hassle, we just want to make sure that we get it right, and have your authority to make changes from whatever you submitted to us, OK?

Thanks, & good luck!