Drastic Tire Size Change
#1
09-08-2000, 11:54 PM
Join Date: Aug 2000
Location: Villa Rica, GA, USA
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Drastic Tire Size Change
This is posted in Aftermarket Wheels/Tires also. I didn't know which one to post to, so I put it in both. Sorry. 
I've got a 2000 F-150 SuperCab and just ordered a set of 10 spoke, 2001 SuperCrew wheels and tires (new takeoffs, great price too). My factory wheels are 16's and the tires are 235/70/R16. The new wheel/tire combo is 265/70/R17. I didn't think at all about the gear that I am running when I made the order. Am I going to have problems with a 3.31 gear? How far off is my speedo going to be? Do I need to get the computer reprogrammed/recalibrated? I'm not going to be drag racing the truck, so I'm not that worried about loss of HP, but just curious, is my HP loss going to be significant? I'm just now getting used to the Flowmaster and Airaid FIPK mods. Am I immediately going to want to buy a SuperChip to make up for it?
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BigDawg
2000 F-150 SuperCab
Oxford White/Harvest Gold
5.4L V8
3.31 Gear
Husky Liners
Ford Duraliner
FlowMaster 40 Series
K&N FilterCharger
Airaid FIPK
I've got a 2000 F-150 SuperCab and just ordered a set of 10 spoke, 2001 SuperCrew wheels and tires (new takeoffs, great price too). My factory wheels are 16's and the tires are 235/70/R16. The new wheel/tire combo is 265/70/R17. I didn't think at all about the gear that I am running when I made the order. Am I going to have problems with a 3.31 gear? How far off is my speedo going to be? Do I need to get the computer reprogrammed/recalibrated? I'm not going to be drag racing the truck, so I'm not that worried about loss of HP, but just curious, is my HP loss going to be significant? I'm just now getting used to the Flowmaster and Airaid FIPK mods. Am I immediately going to want to buy a SuperChip to make up for it?
------------------
BigDawg
2000 F-150 SuperCab
Oxford White/Harvest Gold
5.4L V8
3.31 Gear
Husky Liners
Ford Duraliner
FlowMaster 40 Series
K&N FilterCharger
Airaid FIPK
#2
09-09-2000, 07:30 AM
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Join Date: Nov 1999
Location: Carolina, Puerto Rico, USA
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BigDawg
Check www.ring-pinion/RPMCalculator.html where you will be able to see what they recomend for that new wheel/tire combo.
Taking in consideration the powerband of your 5.4L and that particular combo they usually are stuffing in there the 3.55's. There is no loss of power in your engine by doing that change, but the ability of transmitting it to the rear wheels will decrease rear wheel HP because of the larger new tires diameter. How much? Well, maybe a small %. And making changes to correct that will depend on how demanding you are. Some people will do it, and some may not.
Regarding the speedo you will be off like 9-10%. And in my case I can fix that with a new speedo gear. In newer models is electronically controlled, I think it should be programmed. You have to check. Or, if you change gears to go as close to the relation that you had at beginning, that will be OK as well.
Good luck with all this.
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1998 F150 4x4 Lariat Supercab Flareside 5.4L in Oxford White/gold, ORP, Tow Package, 3.55 Gears.
Modifications: K&N FIPK, Stepshield door sill protectors, Performance Accesories 3" body lift and Lift Lips.
See photos at <A HREF="http://www.communicomgroup.com/jmtruck
" TARGET=_blank>www.communicomgroup.com/jmtruck
</A>
Check www.ring-pinion/RPMCalculator.html where you will be able to see what they recomend for that new wheel/tire combo.
Taking in consideration the powerband of your 5.4L and that particular combo they usually are stuffing in there the 3.55's. There is no loss of power in your engine by doing that change, but the ability of transmitting it to the rear wheels will decrease rear wheel HP because of the larger new tires diameter. How much? Well, maybe a small %. And making changes to correct that will depend on how demanding you are. Some people will do it, and some may not.
Regarding the speedo you will be off like 9-10%. And in my case I can fix that with a new speedo gear. In newer models is electronically controlled, I think it should be programmed. You have to check. Or, if you change gears to go as close to the relation that you had at beginning, that will be OK as well.
Good luck with all this.
------------------
1998 F150 4x4 Lariat Supercab Flareside 5.4L in Oxford White/gold, ORP, Tow Package, 3.55 Gears.
Modifications: K&N FIPK, Stepshield door sill protectors, Performance Accesories 3" body lift and Lift Lips.
See photos at <A HREF="http://www.communicomgroup.com/jmtruck
" TARGET=_blank>www.communicomgroup.com/jmtruck
</A>
#3
09-09-2000, 09:38 AM
Join Date: Aug 2000
Location: Villa Rica, GA, USA
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Is not changing the gears going to cause damage? According to that calculator (thanks by the way, the link is actually http://www.ring-pinion.com/RPMCalculator.html , but I figured it out), the tire is only going to be 2.7 inches taller. Also, I bought the 3.31 gear to get better gas mileage on the highway. Needless to say, I don't know a whole lot about trannys. Thanks for the help.
------------------
BigDawg
2000 F-150 SuperCab
Oxford White/Harvest Gold
5.4L V8
3.31 Gear
Husky Liners
Ford Duraliner
FlowMaster 40 Series
K&N FilterCharger
Airaid FIPK
------------------
BigDawg
2000 F-150 SuperCab
Oxford White/Harvest Gold
5.4L V8
3.31 Gear
Husky Liners
Ford Duraliner
FlowMaster 40 Series
K&N FilterCharger
Airaid FIPK
#4
10-06-2000, 01:15 AM
Junior Member
Join Date: Oct 2000
Location: Tustin Ranch, CA, USA
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BigDawg
One would think that you are saving gas with the 3.31, but in reality you really don't.
If you drove on a flat surface, no headwind, open highway for hundreds of miles...
I thought the samething to but when you are having to push the gas harder to get the darn thing to go, you end up wasting more gas.
With the 265/70/17's I would probably opt for 3.73 or lower ratio depending on what you will be doing with the truck, i.e. towing (go with 4.10's) if so.
I had a 95 F150 with 3.31 and the 302 motor and it was a dog. Changed them out to 3.73's and the truck and I were happy.
Don't feel bad though, I am having the same problem again. I now have a 2001 Supercrew with the stocker 265/70/17 and 3.55 gears. I want to go to 305/75/16 but will probably need to do a gear swap to 3.73 or 4.10's.
Can anyone say, money, money, money ?
One would think that you are saving gas with the 3.31, but in reality you really don't.
If you drove on a flat surface, no headwind, open highway for hundreds of miles...
I thought the samething to but when you are having to push the gas harder to get the darn thing to go, you end up wasting more gas.
With the 265/70/17's I would probably opt for 3.73 or lower ratio depending on what you will be doing with the truck, i.e. towing (go with 4.10's) if so.
I had a 95 F150 with 3.31 and the 302 motor and it was a dog. Changed them out to 3.73's and the truck and I were happy.
Don't feel bad though, I am having the same problem again. I now have a 2001 Supercrew with the stocker 265/70/17 and 3.55 gears. I want to go to 305/75/16 but will probably need to do a gear swap to 3.73 or 4.10's.
Can anyone say, money, money, money ?