I have an 04 scab 4x4 4.6 and want these tires and rims. I know I have posted a similar question about a decrease in performance. Everyone pretty much said I would notice a performance loss but I have decided to order the xcalibrator so I think this would make up the difference. The only thing I am worried about is gas mileage. I am getting anywhere between 16-17 mpg now driving a mix between highway and city.

 

what are u talking about?

since when does changing rims affect performance?

larger tire size yes..,..but they would have to be significant

 

When you say rims, I assume you are talking about changing rim and tires together? The two sizes that are stock on these trucks seem to be 30 inch and 32 inch. That is a large difference. When I wanted to upgrade my wheels from the stock STX, I didn't want to raise my gears, as 3.55 is already pretty tall, so I went to the Lariat wheels with 30 inch tires, increasing my tire size only .6 inches. I can feel the drop in launch from the 17 inch tires/rims. A jump from stock to 32 with a 4.6 will not be overcome by a tuner. Doesn't mean it won't work, just means you will loose a noticable amount of power. It will be as if you changed your rear gears to 3.32
To clarify your situation, why don't you post the size tires you are running now, and the size rim/tire you want to switch to?
Chris

 

I am running the stock 255/60/17 tires. I wanted the 18" FX4 rims and tires. I have several friends who have upgraded to larger rims and tires on their trucks and they say they haven't notice any power loss or decrease in mileage. The trucks range from Toyotas, Fords, Chevys... all different size motors. When I read on here everyone says that I will notice a power loss. I was also wondering about the gas mileage. It is just confusing to hear from friends that their truck feels the same after larger tires but here everyone says don't do it because you will notice a power loss. Last week a friend of mine who has a 03 F150 screw 4.6 4x4 went from 255/60/17 to 285/65/17 and he told me he couldn't tell. I can't comment on this because I have never drove his truck.

 

On my old 2000 Scab, all I did was switch the tires from the OEM Generals 245/70-16 and switched to Michelin 255/70-16 and that affected my mileage and acceleration noticeable! Just 1/2 in. increase in diameter made a noticeable difference.

 

.6 inches made a noticeable difference in mine, so I would have to agree.

99ls1z, what you are saying is that a change from a rear gear of 3.55 to 3.32
shouldn't make a difference? Then why should they sell more than one geared rear end?
The guys going to 4.56 because they put 35 inch tires on their trucks could argue that point.

There are two flaws in the argument as a whole.
1. The statement that they don't notice the difference is totally meaningless.
That's like the guys that say they tow 6000 lbs and 'it doesn't feel like there is anything back there'. Right. It's less than hearsay
.
2. We haven't defined 'make a difference'.
If you define it as ‘can you still drive the truck’, then 35 inch tires are not a problem. The truck will still drive. Everyday, and for many miles.
If you define the difference as 'it won't chirp the tires anymore' or it feels like I'm taking off in second gear, then you have something we can talk about.

Your tires are 255/60/17? I wonder about that. I see a lot of them with 255/65/17.
255/60/17 inch tires would be very short. 29 inches tall.
The common FX4 tire is 275/65/18 which is 31 inches tall.
That is a 7% increase in ratio.

If your tires are actually 255/65/17 they are 30 inches tall. That would be a jump of 3%, not very much, and a three percent drop in power would not bother most drivers.

You can go to Lariat wheels and tires, 265/60/18 and only loose a tiny amount. about 1.6% hardly noticeable.

Also, you may not notice even a 10% drop in power. Many people can run with a flat tire, or a spark plug wire off and never notice it.
Most of us who post here do notice little things like a 7% drop in power.

Double check your tire size, and then do what seems best.
Chris

 

the FX4 275-65-18 is 32.1" tall. I switched from the Lariat 265-60-18, 30.5" tall tires. There's a 5.1% difference in rolling diameter. You guys noticing a big difference in .6" tire height must be like the princess that slept on a pea. Swapping tires/wheels may have effectively dropped my gearing from 3.73 down closer to a 3.55, but it still pulls very hard, and is the identical setup that all the stock tired (32") 4x4's with 3.73 gearing have, without the extra 10-15% parasitic power loss due to the 4x4 drivetrain. When compensating for the slight speedometer error I notice no difference in gas mileage. I say go for it 99ls1z!

 

The numbers on the tire say the size which computes to the diameter, but it is nominal.
Six different tires from six different manufacturers would vary by the legal 1.9 percent. That does not include the difference from tire tread.
275 millimeters times the 60 aspect ratio times two plus the rim diameter is the correct size.
But when you measure them with a tape measure, you get a larger number. The tires on a rim bulge when inflated.
Still, on a semi-aggressive tread tire like the Long Trail 32.1 inches is within specification.
On something like a classic snow tire, you could even get 33 inches around, and it would still be a 275-65-18.
I used the legal size, as that is the only way to compare the tires without taking tread, brand, wear, etc. in to account.

As to noticing the difference, do the math. Changing the tire size two inches is more change at sea level than adding an Airforce one, or a Catback or a premium tuner, as the place you notice the change is at launch, where you are not making more than 125-140 horse on any of these trucks.
This becomes much more noticeable at high altitude, where the horsepower is much lower, but the gear change is the same.

I don't suppose you think all the guys with intakes, tuners, or catbacks are 'princesses' because they feel the 1 to 3 percent increase at launch any of these might give?

Also note that he is talking about a 4.6 truck.
A 4.6 with 3.55 gears is actually very tall geared. a 5.4 with 3.55 or a 4.6 with 3.73 would not be affected anywhere near as much. A 4.6 3.73 truck with the 32 inch tires would be the same gearing as the 4.6 3.55 with 30 inch tires. Are you suggesting that you couldn't feel the difference between 3.73 and 3.55 gears?

Not really starting an argument, but on a 4.6 truck with 3.55 gears you are going to notice the drop in power throughout the range if you go from a 255-60-17 to a 275-65-18.

We are talking the equivalent of dropping 10-15 ponies.
Should he do it? Sure, why not? Only a few of us are worried about a little extra power anyway.
And notice, I swapped to the 18 inch rims myself, on a 4.6 3.55 truck. The 1.6 percent that I lost was not too much to give up for better looking rims, to me. But to deny that you do take a loss is just wrong.
Chris

 

Sorry my tires are actually 255/65/17. You said I may notice 10-15 hp loss going to the 275/65/18 FX4 rims and tires. I thought a tuner would give me at least that in hp increase. I also plan on adding a magnaflow muffler. I just think that the tires on my truck look too small. If I don't get the 18" rims I want to get a bigger tire. The largest I would go would be 285s for the stock 17 rim. I just personally like the FX4 rims better than the XLT rims. I can handle a small power loss for the better look. I just don't want to loose 2 mpg by making the swap. Have you noticed a power loss or a loss in mileage?

 

I lost both. My .5" increase in tire diameter cost me about 1/2 to 1 mpg decrease in mpg and it seemed more sluggish. My GF drove my truck and even she remarked that it felt a little slower, even though I didn't tell her I changed my tires.

I have 18" on my FX4 w/ 3.73, and I rarely get 15 mpg with mixed (biased towards highway) driving and get 13 mpg mostly city driving. Obviously I won't be changing to bigger tires anytime soon. The heavy FX4 Screw is already pretty slow already; I can't imagine what would happen with some fat all terrains, unless I go 4.10 or something like that.

 

Why don't you look for some Lariat 265/60/18 tire/rim combos.
That's what I did, and I'm quite happy.
The loss is 1.6 percent, really no big thing. My highway mileage got a fraction better, and my around town mileage got a fraction worse.

When I had the stock 255/65/17 Michelin tires with the Magnaflow catback and Superchips tuner on premium I could spin the tires on rough pavement on launch. When I switched to the bigger (1.6%), heavier (20/bs) tire rim combo, I could not spin them. I didn't notice a power loss anywhere but out of the hole.
I have since added a BruteForce intake, and even on Premium tune on my tuner, it still won't do more than chirp the tires on anything but smooth pavement. On regular coarse pavement there is no spin at all.
The heavier rims, combined with the slight diameter increase stops any spinning.
On smooth pavement, a rarity around here, it will smoke the tires, but that’s cheating…
Look into the 265-60-18 rims-tires and see what you think.
Have a great one,
Chris

 

I will check into these.

 

Lariats come with 275/65/18's also.Mine did.

 

As unbelievable as it sounds, these trucks have about 9 different stock tire sizes.
Ouch.

The only ones on an 18 inch rim that is almost the same diameter as the very common 255/65/17 is the 265/60/18 which is only on some Lariats, and is only in the BFG Long Trail.
I swapped my Michelin 17s to the BFG 18s and found the ride was slightly better with the BFG's and the handling about the same. And that's with the Michelins. If you were pulling off Hankooks or Generals etc. I think you would notice an improvement in handling and in the ride with the Long Trails.
Chris

 

i have a '04 stx std cab w/ 4.6 and 3.55 L slip traded 17inch michelins out for the fx4 18 inch bfg. no loss of mph and any power loss was/is negligible. 14mpg before (40 miles round trip daily, 85 before i get to the end of on ramp then set cruise. 39 of the 40, hiway miles still 14 mpg.) have noticed nicer ride.