New larger tires and hard downshift
#1
New larger tires and hard downshift
I put some bfg at's on my '16 f250 6.2 today, 285/70r17 from 245/75r17. Has anyone went to a larger tire and had funny downshifts? I had two hard down shifts on the way home from tire shop that I have never had before. I'm hoping this will go away once the computer relearns. Should I disconnect the battery or anything or just drive it and let it learn? I'm a little disappointed, the tires still look tiny, and checking clearances at liners and radius arms, I could have cleared a lot more tire easily. They sure looked bigger on dads '04. These will do me for a year or so until I can upgrade wheels, tires and suspension.
Before
After
Sorry for the crappy photo, couldn't get the lighting right
Before
After
Sorry for the crappy photo, couldn't get the lighting right
#2
#3
You could always get the speedo recalculated and see if that helps. Your new tire (32.7") is only about an inch taller than the stock (31.5") so I'm not sure how much of a difference that will make. This is my truck with 295/70/18's, and I don't have any hard shift issues:
2015 F250 2.5 Front 3.0 Rear
2015 F250 2.5 Front 3.0 Rear
#4
#5
I had 1 more funny shift after posting, but it was an up shift into 2nd. I'm happy to say, that after a 100 mile trip and my daily driving this week, everything has been good. I am a little surprised at the amount of performance decrease from such a small increase in tire size. Very noticeable. My speedo is actually spot on with GPS now. Never checked it before the tire swap.
#7
When you change tire size it's always best to change the tire size in the computer. Today's trucks are more sensitive to changes because of traction speed management and engine speed. It messes up the shift points that you are experiencing. It may just go away but for some things the computer will not adjust to because ford doesn't want it to. You can go to the dealer and have them change the settings and be done with it. Also a 1 inch tire has a additional run out of 3.14 inches. As for power loss that comes from new tires. I bought a set of new tires once and got worse fuel millage and it was because the tires need to be broken in. (run through a few heat cycles)
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#8
Originally Posted by NJSD
You should have gone with a 285/75/17
#9
Originally Posted by The Bone
When you change tire size it's always best to change the tire size in the computer. Today's trucks are more sensitive to changes because of traction speed management and engine speed. It messes up the shift points that you are experiencing. It may just go away but for some things the computer will not adjust to because ford doesn't want it to. You can go to the dealer and have them change the settings and be done with it. Also a 1 inch tire has a additional run out of 3.14 inches. As for power loss that comes from new tires. I bought a set of new tires once and got worse fuel millage and it was because the tires need to be broken in. (run through a few heat cycles)
#10
Take a look at this thread. https://www.ford-trucks.com/forums/1...ut-dealer.html
You can use forSCAN to adjust tire size and it is free. Just need a $12 bluetooth OBD adapter.
You can use forSCAN to adjust tire size and it is free. Just need a $12 bluetooth OBD adapter.
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ADVNTURR
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
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07-26-2012 09:47 PM