Today I put BFG 285/70/17s on Mickey thompson classic II wheels. I drove it around and noticed a little bit of power loss from the larger tires.

Then I loaded the 87 tow custom tune and changed the revs per mile to 635.
BFG website said 634 but the xcal goes in intervals of 5. I drove it around and did not notice any improvement in performance I could tell a slight difference in the torque converter strategy and shift points, then got on the interstate going 75 and cars were passing me at a faster rate than normal. It felt like I was going alittle slower also. I turned the GPS on and was going around 65 mph. On the interstate I was able to go from of 70 to 80 (speedo reading) easier than normal. So I have to get the speedo right to determine if the xcal is making the percieved power difference on the interstate or if it is because the speedo is off.

Has anyone programmed for 285 tires? Was your speedo right using the published revs per mile for your tire?

I guess I will play with the revs per mile until I get the speed right.
When I burn another 3/4 of a tank I will fill it up with 93 and see if there is a difference with the 93 performance tune.

 

I know BFG advertised my 285/65/18's as being 33 inches tall and they are no where near that tall so I would not be suprised if their revolutions per mile was off as well. You might want to post over in the tire section. Wandell and the guys over there are pretty good with the tire info.

 

I am running 295/75/17's that are actually a little over 33.25 inches tall mounted and my speedo is "right on", thanks to the X-Cal2.

 

Hey Marc,
I can't believe this one slipped by you!
93f150 is driving a 1993 model year (by his signature).

93f150, you will have to make tire or gear change calibrations by switching out the speedo gear in the transmission. Ford didn't start to use the ecm for speedometer operation until mid 1997 or 1998. The gears cost are only a few dollars and easy to change. Visit your Ford Dealer parts man and he can get the right one for you to get that speedometer corrected, remember transmission shifting points are effected by this also! So it's important to have correct.

Marc, maybe it was the juice last night?

Allright! I'll let up.

Everybody have a good one!

Gene

 

Must be that long drive from Mikes to home every weekend or
something...

 

Well I guess I need to update my signature because in July I got a new to me hunting truck. It is a 2000 F150 XLT extended cab 5.4 L off road package.

Besides doing maintenance stuff I have put a plastic floor liner over the carpet, got neuroprene seat covers, built custom aluminum toolboxes, built a custom aluminum bumper that houses a Warn 9000i, the tires and rims mentioned above. As soon as Detroit will start selling there locker (supposed to be this month) for the 9.75 I will have 4.10 gears and lockers front and rear. Then after hunting season I will start working on the turbo.

And you are wrong about the 93. It has a speed sensor on the diff, no gear in the trans. I programmed it for larger tires myself by doing a combination of turning the key on and pressing the trip button. You didn't need a gear or a tuner to change tire sizes on the 93, just a few minutes in the yard. Also on the 93 you just jump a wire and get any codes from the check engine light blinking. I don't know why they take these capabilities away from us.

And I fixed the problem with the tire size. Evidently the custom programs are for 3.31 gears. I put 3.55 gears in and the 635 revs/ mile and it was within 1-2 mph depending on the speed you were going. I put the gear ratio back to "stock" and left the 635 and it was way off again. So apparently it came with the wrong "stock" gear setting. Will call Troyer performance to discuss.

Evidently the 635 revs/mile is accurate. Because if you calculate their advertised height (32.8") it comes out to be 615 revs/mile.

 

i have a 96 ford 150 302 with 3.55 i had my vss go out last week and since replacing it the speedo is off way off. do you know how to fix it.
Thanks.

 

I would have to do some research on how to program, it has been years since I did the 93. You have to know which number to put in for the tire size, it is not a size or revs/mile number, it is some other constant that correlates to a tire size.

HOWEVER, I would investigate if perhaps you got a different sensor than what is supposed to be in there. The sensor is supposed to put out a certain amount of pulses per revolution that I thought was standard for all.

 

i don't know i just went to the dealer gave him my truck info and he gave me the part. it is different then the orginal, but only material. the or was half plastic and half metal the new one is all plastic.

 

Well I would go back and try to get the right part.

The only problem with programing is that on those trucks you only get 6 times to program and then you have to replace the EPROM. If you were changing a tire size then you just put in the constant for the tire size. However you are going to be guessing on what numbers to put in to get your speedo correct and this make use your 6 times.

Like I said I would try to get the right part, but if you want to try programming, search on it and search on other sites to just not this one.

Otherwise PM me from time to time to ask me to find it. I just squeez in a few minutes here and there online.

 

could it be a break in period. i blow a fuse for the speedo when it blow so could the pcm be relearning?

 

No.

Something is wrong.

 

it was a break in period of sorts it later stopped moving so much and is only noticeble at 70+ mph. but i think the speedo is going to fry soon i hope not though.