Cons of 33 inch tires

[Rahul Sharma]

I have spent the better part of the past 3 hours reading all posts that have come up for the search "lift" on this forum. Some real informative stuff out there!!



I have just purchased the PA 3" body lift kit (from Chris in the swap and sell section) and am now concentrating on the next part - new tires and rims. From reading here, 285/75 or 33x10.5 should fit no problem with the lift. I'm not doing the shackle/tt lift at this point. but i will be going with A/T tires so i am hoping for no rubbing. I can always trim a bit as well....



My question is this - what are the real cons of having 33inch tires on the trac? These are some of the things i've read:



"Fuel consumption goes up/ MPG goes down" if so, how much?

"The truck is more sluggish because of the gears" how much more sluggish?

"The odometer is off about 5 miles" over or under?



i really am doing the body lift for the aggressive look, and the ability to put bigger tires on it. I'm not taking it off-road, nor am i looking for more clearance (which the body lift doesn't give you anyways). i will most likely be going with a 15 inch rim. Is there a 32 inch tire that will work better? i want it to look good, but i don't want to sacrifice too much fuel consumption and performance.



I will be putting on brand new shocks on as well at the same time i do the lift. Suggestions there would be appreciated as well!



Thanks in advance guys!!

 

[Aaron Yarbough]

"The odometer is off about 5 miles" over or under?

The speedometer would indicate a slower speed than what you would actually be doing.

 

[Johnny O]

If you do the body lift, you don't really need a TT and shackles.

If you have 4.10 gears you can live with 33's although to keep the rpm vs. road speed close to stock you should get 4.56's. This is not cheap. 4.56's would probably help the mpg though.

With stock gears your odometer will read slower than you are actually going. Roughly 15%.

285/75-16's will fit on the stock 16x7 rims but will rub a little on the insides. A 16x8 is better and the Pro Comp 1069 has the least backspacing, 4.0", of any 16x8 that I've seen.

A 15x8 with 3.75" backspace is common and will work well. 15" tires are cheaper than the equivalent 16" size. A 32x11.50-15 will work fine with just the body lift.

 

[Rahul Sharma]

thanks JohnnyO for the info. i guess going to a 32x11.5 which is effectively a 31.5 tire would actually help in all regards as compared to a 33x12.5 which is a 32.6 inch tire.



how expensive is it to change the gears?



i thought that teh XCal2 helps with the problem of odometer and MPG? i haven't read much on it, so i may be out to lunch here....

 

[Yardsale]

Tire diameters are specific to the individual tire design (they are close, but not exact).



Expect to pay $500 to 600 for each differential. Add a bit ($100) more for the front differential labor.



ProComp will custom make steel rims with any back space you want (within safety parameters of the particular rim style). BTW - steel rims are typically less expensive than aluminum or magnesium.



The percentage difference in tire diameter between stock and what you decide is the percentage difference in indicated speed. Changing from 30 to 33 inch is about 10%, so the indicated speed will be about 10% less than actual speed. For your ’05, this can be corrected by regearing (to bring the distance traveled by the tires and the transmission back in sync.) or reprogramming (to change the sensed speed signal that is used to display speed). Reprogramming will not compensate for the following …



More cons - with a larger diameter tire and without compensating by regearing the differential(s), at a given speed, the engine RPM will be lower and may be below the power band for the engine. This can be a concern on long hills where, instead of accelerating a bit to maintain speed, you will have to force a down shift (and this cycle will repeat until the hill is topped). This is one area where you will notice fuel consumption.



It's not always simple.

 

[Matthew W]

Just a note on the speedometer .... it won't be off b as much as you think. I have found that Fords, from the factory, say you are going faster than you actually are (yes, I drive fords for work as well as owning some). On my Trac, I have the Toyo Open Country 285/75/16 on stock wheels, and have gone past several different speed radar/warning machines ... my speedometer only reads about 2-3 mph slower than actual (usually in the 45 mph range).

 

[Becker69 CO]

I have been running 32x11.50x15's on my truck for about 6 years and they have been great... I don't have a BL, but have the TT/shackle instead (which is about 1.25" less clearance than you'll have). I have 15x8 Eagle Alloys (3.75" backspaced). An added benefit of going with 32x11.50's vrs. 33x12.50's is the shear difference in weight of the tire (~ 6-9 lbs less per tire!!). This yields a little less wear and tear on your brakes without stressing them quite as much as heavy 12.50's.



(not to mention if you go with a 265 75 16 as a spare -using the stock steel wheel... you'll still be able to fit it in the spare tire location!)



If you interested in supremely impressive (for street and winter/snow driving) AT tires, give the Pro Comp AT's a look in 32x11.50. I have been in Colorado for 4 years now and have several thousand snow miles on my Pro Comps and I am continually impressed with their snow traction. Good luck and enjoy your mods!!

 

[Tom Schindler]

math-you,



Those radar warning machines are not accurate at all. Get a GPS and see how accurate your Speedometer really is. My Trac's Speedo is within 1 MPH.





Tom

 

[George C]

RS,

I have the TT and Shackle lift with 285/75/16 BF Goodrich All-Terrain T/A ko tires. There is a noticeable difference in fuel mileage and performance. If you have the 4.10 gears already that is a help. If you go with the 285's your speedometer will be slow by about 9.5%.



Good idea on upgrading the shocks. I would also recommend at least the rear sway bar and front if you have the extra cash. You will want improved handling and support because you will lose some with the lift. I have the Rancho RS9000X adjustable shocks and love them.



George

 

[Rahul Sharma]

thank-you all for you reply's - it's been helpful!



in the end, i think i like what Becker CO suggested with the 32x11.5's. i don't think that there will be too much visual difference between those and the 285's, however, if i can keep the weight down, that should help.



I am leaning towards the Rancho RS9000X shocks myself George. i have factory shocks on right now, so i am expecting the biggest gains there! the rear and front sway bars might have to wait just a little bit, as i am eagerly awaiting the lift kit, and then this month i will get on the lift kit, new tires, new wheels, shocks, and install all my audio equipment that i bought last month! New head unit, ipod, and 4 new speakers! in a matter of weeks it's going to be a brand new ride!