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Researching new tires for this fall. What is the largest metric size 18" that will fit a stock F350 Fx4 CC SB (camper and snow plow package if that makes a difference). What advantages and disadvantages (besides mileage) is there with a larger tire. I noticed the Toyo ATII goes to a higher max load with the 285/75 and 295/70. I'll be pulling a 10K-11K camper.
I ran 295/70R18s on factory 18"s and they fit fine, never rubbed. 6000# front springs with a heavy replacement bumper. I don't know what the absolute biggest you could stuff under is, but 295mm was the widest Nitto specified for an 8" wide wheel. I came down from 35x12.50s that rubbed even with a 2" leveling kit because the 17x9" wheels were backspaced out further than factory rims.
I had Nitto Trail Graplers, they wandered pretty bad when new, long solid M/T tread lugs will do that though. They pumped up to 4080# rating at 80spi though, they were very stable when towing after the first 10k or so. Disadvantage is an effective reduction in your gear ratio. If you have factory 20s you probably won't notice, but coming from 31.5"/265/70R17s I could tell a difference. Realistically anything that fits a factory wheel won't have significant disadvantages, so long as you get the correct load rating.
I ran 295/70R18s on factory 18"s and they fit fine, never rubbed. 6000# front springs with a heavy replacement bumper. I don't know what the absolute biggest you could stuff under is, but 295mm was the widest Nitto specified for an 8" wide wheel. I came down from 35x12.50s that rubbed even with a 2" leveling kit because the 17x9" wheels were backspaced out further than factory rims.
I had Nitto Trail Graplers, they wandered pretty bad when new, long solid M/T tread lugs will do that though. They pumped up to 4080# rating at 80spi though, they were very stable when towing after the first 10k or so. Disadvantage is an effective reduction in your gear ratio. If you have factory 20s you probably won't notice, but coming from 31.5"/265/70R17s I could tell a difference. Realistically anything that fits a factory wheel won't have significant disadvantages, so long as you get the correct load rating.
I don't want to go bigger than 295s. Maybe it's better just to stay with the stock size?
Every increase in tire rolling radius is reverse leverage against brake output. It’s part of the reason the ‘05+ and further went to larger diameter rotors from the ‘99-04 size. Higher GVW, larger dia and you go up in size. The target pedal effort was the same, just needed more wheel end torque. Back in the day, 2001, I measured the differential going from 265 to 285 on 16” rims. Not much but it’s measurable, but you can compensate by going to an aftermarket friction with a little higher friction coefficient. In public, that’s not an attribute public readily available except the required edge code which isn’t that precise.
I'm looking at the Toyo ATII. 275/70R18 show 33.2" inflated diameter, 295/70R18 show 34.3". Width is only .8" difference. Max load is 4080 for the 295 vs 3640 for the 275, but not really sure that matters in my application.
Its all in degrees. It when you go all large that's when it makes a real impact. I wouldn't let tire diameter be your overall consideration, I just wanted to inform there is a disadvantage since that was half the question. If when operating you feel you've lost brake effectiveness you have the option of changing to a more aggressive friction material.
It's just math.
It becomes a big problem when you go real large, there is no way to make up the leverage change by increasing pad coefficient of friction or increasing clamping force by larger pistons or more pistons. You have to increase the swept radius of the brake. Guys who go all monster size often get into this situation, try to go Wildwood and other directions. The answer is F450/550 axles with the larger diameter brakes. At the OE level, you punch up a few mm on the rotors, maybe a few mm in piston size if you have to. But larger caliper pistons means larger volume, so then it's on to larger Master Cylinder diameter and higher pedal effort or you have a longer travel with the original size, but the increase in M/C size usually is a balance because of the increase in brake effectiveness. If not, then a change in pedal lever ratio. Gets complicated.
Everybody got real excited about bigger brakes on the '05 package. It's all relative due to the tire change. And higher GVW.
Correct. The optional 20" 65 profile tire were in the 34.0-34.4" range. But as with any tire option situation we still saw variations in pedal effort vs deceleration within the OE offering. Some people notice it and others don't. It's when you get up in the 10% range that many people start complaining, but that is also a variable between people. I noticed a change in effort 265 to 285, but it's what I was doing for a living at the time.
I’m still good with that type of material. I may try the Motorcraft Super Duty pads on the next build. I’m not sure what formula they are using now. The one we approved years ago was good.
The one thing I don’t care for with the Hawk LTS is the POS noise insulator they apply to the back. In the aftermarket side of the business all the companies slap on a generic product, all of them. But there is a choice of using stainless steel as the metal layer, or not. Hawk does not. I’ve not had any noise because of the deterioration, it just irks me. When I go in my office I’ll edit in some images of what I mean. Environments with a less corrosive nature won’t have this issue.
Edit - I cannot find those images. What happens in a high corrosive environment is they just rust away.
No problem, it's appreciated but not necessary. It really depends on how you're using the truck to determine what type of material is best. And past issues you didn't like. I used to recommend Performance Friction "Z" pads for the '99-04 trucks, even over the Hawk LTS. It's what I used to have on my '03 first. That material was OE on the OBS, higher in friction, good thermal resistance, and the needed higher rotor abrasion compared to the OE material. They stopped supplying it and told people to use the "Carbon Metallic" but that was NOT the same formulation. (BTW, Hawk now calls their products "Carbon Metallic"). We tested all the competitors and CF was different in character. PF then brought back the "Z" into the market, but since I never tested it to confirm if it was the exact same I got gun-shy about endorsing it since they were recommending the CF instead. I never would have. They just don't have a high trust factor from me, and even got kicked out of Ford programs according to our sales guys. The founder of the company has since passed on and I have no idea how its run today.
The PF Products are different in formulation then most of the products out there. The biggest issue on the OBS trucks was that due to its thermal resistance and hard structure, the OBS trucks suffered rotor cracking due to hot spots, you need a compliant material to avoid that. But the OBS trucks would generate very high front rotor temps, and that resulted in one of the design goals of the '99 level disc-disc brake system, resulting the trucks running cooler then normal. So despite the hot spotting capability, it would not occur on the cooler running '99+ vehicles so I felt it was safe.
The Motorcraft pad formulation used in the SuperDuty line during my time was a tick higher in friction then OE, good fade resistance, good wear resistance, and the correct rotor abrasion level. Not as quiet as the OE material under some circumstances, but didn't have as expensive of a noise insulator, but better still then 99% of the aftermarket materials out there. I just don't talk about it much as I've not put it on my vehicle.
The problem I have in recommending materials is in the aftermarket many lines have a 3-5 year changeover rate. Based on warranty feedback, changes in production equipment, or the request by wholesale customers for something cheaper everyone flips. I've been out of the game 10 years. And my recommendations always were on test and real work experience.
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