18 inch wheels with 17 inch spare

[CaliBee]

I have the Black Appearance Package with 18 inch wheels. A quick look under my truck shows it has a 17 inch spare. Does that mean I'd have to drive cautiously if I need to use the spare? Under 55 mph, and only a short distance? Should I get an 18 inch wheel for my spare? (Or should I get four 17 inch wheels for my truck? But that's a topic for another thread.)

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[Rinn69]

The spare's tire is a taller sidewall (65) than the stock (60). No issues, but heed the warnings on the spare.

This question has been beaten within an inch of it's life sooo many times... Not trying to be an ass, but I learned early on, when joining a forum, the first thing to do is a search before posting a question. Just a friendly suggestion as I've been flamed pretty good in other forums.

 

[TBR17]

I have the Black Appearance Package with 18 inch wheels. A quick look under my truck shows it has a 17 inch spare. Does that mean I'd have to drive cautiously if I need to use the spare? Under 55 mph, and only a short distance? Should I get an 18 inch wheel for my spare? (Or should I get four 17 inch wheels for my truck? But that's a topic for another thread.)

They are as close as you can get in 2 different rim sizes. Overall circumference 95.8" vs 96". Not enough to cause harm.

 

[HenryMac]

I have the Black Appearance Package with 18 inch wheels. A quick look under my truck shows it has a 17 inch spare. Does that mean I'd have to drive cautiously if I need to use the spare? Under 55 mph, and only a short distance? Should I get an 18 inch wheel for my spare? (Or should I get four 17 inch wheels for my truck? But that's a topic for another thread.)

It states right on the spare tire not to run over 50 mph. Also states that in the Owners Manual. But I researched the tire, and the wheel. Both are regular production units. The tire is no different than what you would buy and the wheel is the same that comes on all four corners of a XL Ranger.

Oh, and flip the spare over so you can easily check the air pressure.. More on all of this here: Flipping The Spare

 

[TBR17]

It states right on the spare tire not to run over 50 mph. Also states that in the Owners Manual. But I researched the tire, and the wheel. Both are regular production units. The tire is no different than what you would buy and the wheel is the same that comes on all four corners of a XL Ranger.

Oh, and flip the spare over so you can easily check the air pressure.. More on all of this here: Flipping The Spare

That must be a Ford CYA thing.
I added a takeoff matching alloy to avoid the "you got a flat" glare from fellow judgmental motorists.

 

[HenryMac]

That must be a Ford CYA thing.
I added a takeoff matching alloy to avoid the "you got a flat" glare from fellow judgmental motorists.

The 50 mph mandate does make some sense. Your other tires are wearing, so it's diameter doesn't match the other tires on the truck and that's getting worse everyday. If folks do as you have done, rotate their tires frequently (every 4,000 miles) and include the spare tire in each rotation, then your good to go at highway speeds. Few people do this.

I guess you could put the spare on the right rear... and do a long smoky burnout, then measure the circumference...

But don't use the rear locker like this guy..

 

[DukeCanBuildit]

As others have indicated, wheel diameter is not the big consideration here, overall tire height is. There are plenty of sites to help you with this. Here’s one...https://tiresize.com/chart/

I haven’t looked it up but I‘m pretty sure the height of 17” and 18” Ranger tires are very close, otherwise, they’d be re-calibrating speedometers based on trim level or options. This allows Ford to use the same spare on all Rangers. Sounds odd but it works for them.

If you get a flat on a rear tire and you put on a spare with tire of much different height, your differential will constantly “differentiate” - this is not good. This isn’t the case on the front.

What to do if you’ve determined your spare is a lot different in height? Replace the flat rear tire with a tire from the front and put the spare on the front. Yep, it’s extra work, but your truck’s worth it.

 

[DukeCanBuildit]

The 50 mph mandate does make some sense. Your other tires are wearing, so it's diameter doesn't match the other tires on the truck and that's getting worse everyday. If folks do as you have done, rotate their tires frequently (every 4,000 miles) and include the spare tire in each rotation, then your good to go at highway speeds. Few people do this.

I guess you could put the spare on the right rear... and do a long smoky burnout, then measure the circumference...

But don't use the rear locker like this guy..

This also works to check that your high-speed balance was done properly. ?

 

[HenryMac]

As others have indicated, wheel diameter is not the big consideration here, overall tire height is.

Well not overall tire height.. just the distance from the ground to the axle c/l.

If you get a flat on a rear tire and you put on a spare with tire of much different height, your differential will constantly “differentiate” - this is not good. This isn’t the case on the front.

What to do if you’ve determined your spare is a lot different in height? Replace the flat rear tire with a tire from the front and put the spare on the front. Yep, it’s extra work, but your truck’s worth it.

Sure, that's solid advice in the case of a rear wheel drive vehicle, but on a 4x4 both the front and rear have open differentials.

Is there something, mechanically, about the front differential that makes it tolerate the tire height difference "better" than the rear?

If that was the case the Owners Manual would specify this... and it doesn't.

 

[DukeCanBuildit]

Well not overall tire height.. just the distance from the ground to the axle c/l.

Sure, on a rear wheel drive. But on a 4x4 both the front and rear have open differentials?

I think Phil chimed in on a similar thread to explain that the fronts are not affected by this - when transfer case isn’t engaged, they turn independently- something like that. Something in engineer-speak, followed up by a cool backstory.

 

[HenryMac]

I think Phil chimed in on a similar thread to explain that the fronts are not affected by this - when transfer case isn’t engaged, they turn independently- something like that. Something in engineer-speak, followed up by a cool backstory.

I wonder if that's applicable to the current Ranger, or just the older Rangers that Phil actually worked with?

 

[DukeCanBuildit]

I wonder if that's applicable to the current Ranger, or just the older Rangers that Phil actually worked with?

Of course, you know I’ve been searching this like mad just now - I think it requires staying out of 4WD. I’ll keep digging and link to it when/if I find it.


EDIT: Here it is...

https://www.ranger5g.com/forum/threads/first-time-ranger-owner.7770/post-138950

...backstory included. ?

 

[port43]

I have the Black Appearance Package with 18 inch wheels. A quick look under my truck shows it has a 17 inch spare. Does that mean I'd have to drive cautiously if I need to use the spare? Under 55 mph, and only a short distance? Should I get an 18 inch wheel for my spare? (Or should I get four 17 inch wheels for my truck? But that's a topic for another thread.)

Do NOT feed the trolls!

 

[HenryMac]

Of course, you know I’ve been searching this like mad just now - I think it requires staying out of 4WD. I’ll keep digging and link to it when/if I find it.


EDIT: Here it is...

https://www.ranger5g.com/forum/threads/first-time-ranger-owner.7770/post-138950

...backstory included. ?

Needs clarification. Does that apply if you are in 2H

 

[DukeCanBuildit]

Do NOT feed the trolls!

John or Steve? ?

Needs clarification. Does that apply if you are in 2H

My gut says only in 2H but my gut’s not gonna solve Steve’s problem. Where’s Phil when you need him?

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