For a while I have been contemplating going up in tire size from the stock 245/75R16 on 16x7 rims to 265/75R16 or 285/75R16 on the stock rims (call me warped, but I kinda like them). These will be going on a 2000 with a 4.6 and 3.55 Limited slip axle. Now my questions are:
1. What will be the impact on these larger tires on my acceleration/power?
2. How difficult is it to get the speedo reprogrammed?
3. Will the 285's clear without any mods, or will I be trimming the plastic/bottoming out inside the fenders?
4. It does not really matter, but what about fuel economy?
5. Will my stock rim fit 265's/285's (many tire manufaturers say lower limit is 7.5" wheel)?
6. Would a new chip lessen the woes created by the mods?


Thanks.

 

1: The 285's may hinder both without regearing. The 265's are a good compromise. I've got them and don't notice much, if any power loss. (I can still leave some marks for 3-4 feet in our company parking lot!!)

2: For the 2k, you have to have it programmed for the new tire size. A 265/75/16 is basically the same size as a 265/70/17, which Ford put on these rigs with the ORP package. They should be able to reprogram the computer for that ratio. Don't know what the cost is. (I've got a 97 and it just needed a speedo gear swap $12.00)

3: Not for sure, but you should not have to trim anything to fit the 285's.

4: You're correct. It doesn't matter! Really, I didn't notice any increase or decrease going to the 265's (once I corrected for the speedo difference, which was @ 5%)

 

gas mileage i don't think changed for me when i got the 285's. i really don't notice a power/acceleration difference either. i only went from 265 to 285, it may be different going from 245 to 285. i also have the 5.4L, 3.73 gears, and some performance mods so that might be why i didn't notice a power difference. if you have a 4x4 285 shouldn't rub at all. if you want pics click on the thumbnail in my sig, (the thumbnail hasn't been loading on my comp lately, may not go at all).

 

I have had 285s on my 97 4x4 for almost a year now with no problems whatsoever. They aren't even close to rubbing at any point. Also I have not noticed any big change in gas mileage, but I have noticed a slight loss of power since I haven't regeared but its negligable. I also have a 4.6L with 3.55 gears. I don't regret getting the 285s at all. Your speedo will have to be reprogramed by a dealer, someone else might correct me on this but I think they're the only ones that can do it on 99 and newer trucks. Also I believe a superchip can accomplish this too.

 

akforsyth,

I'm looking at getting new tires too...increased size.

I think if you went with anything wider than 265 (like 285) you'd
want to get a wider rim. Note I said want, not need....A 285 recommends a 7-9" rim. It might look like the tire bulges out...which is ok if that is the look you're going for.
285/75s should look pretty macho either way. (33" tire)
I'm actually looking at staying with the same width but taller.
(255/85) Maybe some Dunlop Radial Rover A/Ts or Bridgestone Dueler A/Ts or H/Ls.

 

Anyone else...I'm still kind of lacking in the info department.

 

I'm also thinking of going to 265 from 245's. I've got a '97 4.6 with the 3.55 rear also. Can someone tell me which speedo gear I need? As well, are tranny shift points affected at all with this change in tire size?

 

powerstroke73:

How does your tranny like the 285's? I'm concerned about it shifting all over the place with Overdrive.

Are you able to use it?


Kurt
97 F150 4x4 3.55

 

I just put 305/70/16's on my 97 with NO lift at all. They don't rub. The tranny seems fine, other then the loss of power at the low end. I have the 3.55LS rear. I also have a superchip.