Ok, I have a 1998 F-150 4x2 4.2.

It has the standard 235/70-16 wheels. I'd like bigger wheels but I'm confused and scared i'll screw something up.

Can someone explain to me what happens with bigger wheels, and mainly what's the biggest that will go on my truck and how will that affect the transmission. I'm also concerned about losing power; I don't tow anything, but I don't want to throw what acceleration the v6 has in the trash.


Thanks

 

Well you change the gear ratio when you go to bigger tires, i went up to 265 on all the f-150s (1)1997 (2) 1998s..you feel it alittle but its liveable...all but my 1998 came with the 235s..Im getting ready to put 295s on next month when i get mine lifted, so i will be going up 4 tire sizes..wont know how that will feel, if need be i will regear....Good luck..Dave

------------------
1998 F-150 sc/flareside, 4.6,auto,3.55s,airaid system w/k&n,flowmater w/duals out the back side 45*, superchip, blk nerf bars, bed liner and mat, bug shield and window rain guards, cls III reciever, tinted windows, cd changer,Atlas polished rims w/265-75-16 pirelli at/scorpions,oxford white.

 

First, your current tire & wheel diameter is about 29". Next, I'm assuming you want a larger overall diameter tire & wheel combo, not just "bigger wheels". Unfortunately, to keep the speedo accuracy and acceleration you have now, you need to stay pretty close to the stock overall diameter.

If bigger wheels are all you want, remember that as the wheel size increases, the tire diameter must decrease. And, as wheel size increases, tire availability decreases. You can get 20" wheels, but finding tires will be difficult. When you do find them, they will be expensive.

You could probably go up to 31" tire & wheel combo without the tires rubbing the fenderwells, but your power will be somewhat impacted and your speedo will be off about 7%. The only tranny affect will be that your shift-points will be off a little.

It is possible to reduce the effects of larger tire & wheel combos by changing the gears in the rear-end. However, this can get expensive as well. There really is no cheap solution.

Just an FYI, it's possible to go DOWN in wheel size & buy bigger tires while keeping the overall diameter the same- or larger.

Neal

------------------
1997 4x4 Expedition- 4.6L, true dual exhaust w/glass-packs, K&N air filter, SuperChip, airbox mods, Edelbrock shocks, 285/75R16 BFG ATs, Optima "T-Bone" wheels, and Clarion In-dash CD player.

1993 4x2 F150 Reg. Cab LWB- 5.0L, cat-back dual exhaust w/glass-packs, K&N air filter, Superchip, fresh paint, and Line-X bedliner.
http://members.visualcities.com/NoMo

 

Go to 4lo.com that l is the letter L. On top of the page to the left are some tire and gear calculators that will tell you tire size and even the gear you should change to if you are trying to maintain your original power settings. For example to change from 255/70/16 to 265/75/16 I would need to change the rear gears from 3.55 to 3.73 to maintain original specs on power and speedometer.

------------------
97 F-150, 2WD, Reg Cab,Flareside,Dk Toreador Red, 4.6, 3.55 LS, EGR Bug Deflector, ******* Bed Cover, Bed Liner, XL Full Length Running Boards, Air Aid Kit, Gibson Single Out Cat Back, Superchips, TransGo Shift Kit, Hellwig Rear Sway Bar, Hellwig 2500# Overload Springs

 

also check out www.tirerack.com
in their "tire tech" section they have a chart that lists a wide range of truck tires by overall diameter making it very easy to pick a changeover to another wheel/tire combo

 

Bottom line - if you increase the overall height of you tires without changing the gears you will feel a loss in power. I went up 5% on mine and can feel a significant difference in power and my mileage went down about 1 - 1.5 mpg. Still love the looks of the new tires but wish I had 4.11 gears. Unfortunately no way can afford swapping both front and rear gears. Way to expensive. I wish Ford had taller gears as an option.

------------------
'97 F150 Lariat, Flareside, SC, ORP, 5.4, Mods: 305/70/16 GY ATS, AR Baja wheels, dual exhaust, Smittybilt nerf bars, Edelbrock IAS Shocks and fog light mod.

 

kkirt1:
Are you remembering to multiply your miles/tank by 5% and add that to the MPG equation? As you know, you just went from 3.73 gears to "effectively" 3.55 gears. This usually results in a slight increase in fuel mileage. Also, your speedo is off- so you may be driving faster than before.

Neal

------------------
1997 4x4 Expedition- 4.6L, true dual exhaust w/glass-packs, K&N air filter, SuperChip, airbox mods, Edelbrock shocks, 285/75R16 BFG ATs, Optima "T-Bone" wheels, and Clarion In-dash CD player.

1993 4x2 F150 Reg. Cab LWB- 5.0L, cat-back dual exhaust w/glass-packs, K&N air filter, Superchip, fresh paint, and Line-X bedliner.
http://members.visualcities.com/NoMo

 

Neal: I didn't think about the 5% in the mileage equation. Thanks! I was getting about 300 miles from a tank and now I'm getting 250. The 5% helps some. My odometer at 250 should say 262. The difference between the 262 and the 300 I attribute to the increased rolling resistance from the big Goodyears. I have gradually increased the pressure in the tires and it seems to be helping the mileage. At the factory recommeded (Ford) pressure of 29 I was getting about 240 miles from a tank full. I have the front aired up to 40 and the back at 42 now. I think a good compromise between fuel economy and ride quality.

BTW, my truck has 3.55 gears so I went down to 3.37 gears. I drive mostly in the city so I don't think I am getting much benefit from the taller gears.



------------------
'97 F150 Lariat, Flareside, SC, ORP, 5.4, Mods: 305/70/16 GY ATS, AR Baja wheels, dual exhaust, Smittybilt nerf bars, Edelbrock IAS Shocks and fog light mod.

 

Thanks for all the info.

it sounds like if I only make 1-1.5" change, the difference will not be that major.

When it comes to getting different gears, is that sometihing that a dealer can do or is it purely aftermarket?

 

Definitely aftermarket.
Most dealers wouldn't touch it with a 10ft pole.


------------------
99 XLT 5.4l reg cab
4 wheel disc/ABS
5 star larait style wheels
Toreador red 2tone
3.55 gears
255/70/16 OWL
Delta toolbox
Eclipse 5340 cd player
Memphis ARCS50 component speakers (excellent sound)
Sherwood amp
subwoofer coming soon
More mods as funds become avalible.