255/85 R16 Owners Experience

My 255/85R16 Cooper S/T report:

I put my 255/85R16 Cooper S/T tires on the truck and did the Rug Road trip this past Friday-Sunday. I lowered the tire pressure to 18-20 PSI and these tires did GREAT! Climbing rocks, steep step decents, and they performed very well. Probably due to the tall sidewall they soak up more impact than a 75 series tire making for a good ride in the rough stuff and lots of traction as they wrap around the terrain. I have 4.56 gears (and lockers) in both axles and the added height over my 265/75 tires also makes the highway cruise a bit lower RPM (which is good!), they are pretty quiet, so I'm elated all the way around.

These S/T are not an aggressive tread pattern but they work great in this rocky terrain, and even on my wide 8" wheels only rubbed when the truck was REALLY flexed out.

 

Is your speedo off with the 4.56 gears and the 255 tires? I've got stock 3.73 gears, 255 tires and mine speedo is off by about 3.2 MPH at 65.

Just wondering thanks.

 

A reminder that the Autos use the wheel sensor, taking the gear ratios out of the equation. Manuals are affected by gear ratio changes.

 

Oh that's right! So autos are going to need an ECU update. Thanks!

 

Glad you asked. I had my Tom-Tom navigation toy on for the 120 mile ride home on the highway. At an indicated 65 MPH on the speedometer the nav was saying 68MPH. I would have guessed it would be further off than that. Cruising at 65 MPH (actual) has the v6 spinning about 2400 RPM, which is easy on the motor and lets it climb slight hills without downshifting out of overdrive. Before the regear (3.73 to 4.56) my truck would downshift on every overpass, I could not stand it. I have a lot of weighty stuff on my Taco (steel plate bumpers on both ends, winch, skids, sliders, 200 lbs of recovery gear, bed rack RTT up in the wind, etc.).

 

Looking to grab a set of Dick Cepek Extreme Countries from 4wheelparts maybe.

Just to clarify, these generally don't require major modifications to run, do they? No cab mount chop, fender cutting, BFhammering like most 285 sizes?

 

My speedo is 2.5 mph fast with st maxx and 4.88 gear (perfect combo)

 

Are you a 4cyl? What are you revving at with that gear combo? 4.88s are generally for the 35+ size, so I have heard mixed views on this gear combo compared to 4.56.

 

x2!


...I've also heard 4.88 is good for auto and 4.56 is good for manual.

 

From what I have heard 4.88's are going to be over geared unless you're in the 35-37 variety or a 4cyl. Even with 35's 4.56 are good for either, generally speaking. Even a dclb auto with armour at 35's I have read people being over geared with 4.88's. Now back a square one lol.

 

I'd be quite interested to hear some testimonials for 4-cylinder re-gears.

 

Thanks. I will regear to 4.56 when I can afford it.

 

I know this feeling.....

 

4.88 is a great combo for the 4cyl 5 speed and 33's. I'm running around 3100 rpm at 70 mph and 2700 at 60 perfect range in my opinion for the power band of the 4cyl. I was going to go 4.56 but all of the gear guys that I talked to said 4.88 and very glad I did. Even with my 265/70 r16 the gearing was not to much in my opinion.

 

In case you didn't know, the 2.7L Prerunner TRD Autos come stock with 4.56 gears.

 

I thought it was 4.10

 

I'm not sure about 2nd gens, but 1st gens definitely. That is the only TRD combo that didn't get the elocker.

 

Awesome, thanks for sharing!

 

I have ICON Extended travel suspension adjusted to give about 2" lift over stock, my 255/85 Cooprt S/T tires and have done no cutting or pounding mods. I did remove the factory mud flaps because they hit tires and terrain and I figured that if they got ripped off it would screw up my fender.

 

Ring an pinion ratios should match you individual use. For example if you run the highways most of the time and those highways are mostly level ground I would stick with factory 3.73 ratios (on most 2nd gen V6 trucks) and save a bit of fuel. If you live in the back country and rarely get to go 70 MPH plus spend a lot of time pulling and rough hilly terrain then 4.88 may be your BEST choice. Also tire heigth, vehicle weight and motor torque are all factors. Gear ratio is a personal thing, but I always end up with higher numerical ratios in my vehicles, and the extra torque means livelier performance tooling around in the city....

I like my 4.56 gears with the 255/85 tires, but it is not my daily driver either. I had considered going to 35" tires, but some guys have chopped up their fenders, flares, removed inner fenders, pounded the hell out of firewall, and still rub. I cannot justify this kind of butchery on a fairly new truck personally.

As to Gas Mileage, the truck works so well off-road that I don't worry about fuel mileage. For reference I have the 4.0L V6 and auto trans, both bone stock.