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Old 07-10-2012, 04:44 PM   #1
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285/75/r17s no lift?

Hey guys,

Im planning a 2.5 inch lift, and cant get it installed until mid august.

I want to sell my rubi tires and wheels. can I drive the Rubicon unlimited with 18/59 springs with these tires on 4.5 inch backspaced wheels?

or am I going to rub like crazy and want to kill myself?

Also road noise, km2 vs km1 noticable?

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Old 07-10-2012, 04:46 PM   #2
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The tires are BFG km2 285/75r17

also, do I need a new tire carrier for this tire?

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Old 07-10-2012, 04:50 PM   #3
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Those are considered 32" tires and that's about what I run with no lift needed. Mine ar 255/75/17's but yours are a bit wider so you may need to get a diff tire carrier. Mine barely fits on the back but its enough to stay put just fine. My 5th MT is on back order so I have a Goodyear on the back until it comes in.

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Old 07-10-2012, 04:53 PM   #4
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I think your tires are standard size, the 285/75/r17s are rated at 33.9. They are less than an inch smaller than the km2 35s
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Old 07-10-2012, 04:59 PM   #5
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Quote:
Originally Posted by BlackOpsJeep
Those are considered 32" tires and that's about what I run with no lift needed. Mine ar 255/75/17's but yours are a bit wider so you may need to get a diff tire carrier. Mine barely fits on the back but its enough to stay put just fine. My 5th MT is on back order so I have a Goodyear on the back until it comes in.
The tire carrier isn't about fitting its about weight. Too much weight will pull the welds on the tailgate. See how much the new tire/wheel combo weighs compared to the stock Rubi and you'll have your answer on if you need a new one or not
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Old 07-10-2012, 05:26 PM   #6
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I have 285/70/17s on my JK, they fit with no lift or wheel spacers. For the spare it fit fine but touched the third brake light arm so I made a 1/4" spacer out of King Starboard which solved the problem, it fits over the spare mount.
I have since added 18 and 59 springs which lifted it up a little.
From what I have read the 285/75/17s are only slightly bigger, I considered them but I wanted to run a P rated tire not LT, I ended up getting Toyo Open Country ATs, they are light and perfect for the JK in my opinion. I have LT tires on my Tundra and they made it ride much harsher, they are 275/70/18s load range E.
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Old 07-10-2012, 05:34 PM   #7
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LT285/75/16 with 4.25 BS...........no lift.
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Old 07-10-2012, 05:44 PM   #8
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I think those two examples are a little smaller than the 285/75r17 but thanks for the responses.

I have daystar spacers for the tire carrier.

anyone else have this size tire?
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Old 07-10-2012, 05:49 PM   #9
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I have 33x12.5s on stock suspension with no issues
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Old 07-10-2012, 09:34 PM   #10
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Originally Posted by PieFace View Post
I think your tires are standard size, the 285/75/r17s are rated at 33.9. They are less than an inch smaller than the km2 35s
Pieface, allow me to correct you. We both have the same height tire. The only difference between yours and mine is WIDTH (the 285 vs my 255) That number represents the width, the 75 represents is the ratio of the height of the tire's sidewall to its width (aspect ratio). 75 means that the height is equal to 75% of the tire's width.. Therefore, someone running a 70 series tire is taller than someone running aa low-profile 35 series. Then the last number represents the size of the rim in inches (a 17" rim or whatever). So, to summarize, a wheel and tire combination which in our case is 75 series and a 17" rim averages 32" in height. As N3M0 pointed out, the only real issue is the extra weight of a wider tire, thus the 285 you are referring to vs my 255. Probably not alot of difference in weight but yours would be a little wider which might cause issues on the OEM tire carrier. Hope this clears it up.

here is the definitions of tire markings:
http://b2c.sullivantire.com:8082/Tir...%20Ratings.htm

edit: I will admit that there are some wider tires that will end up "bowing up" a little more in the middle thus the height of your tire could be 33". I will admit I am not always correct but I'm pretty sure ours are about the same.
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Old 07-10-2012, 10:43 PM   #11
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Quote:
Originally Posted by BlackOpsJeep View Post
Pieface, allow me to correct you. We both have the same height tire. The only difference between yours and mine is WIDTH (the 285 vs my 255) That number represents the width, the 75 represents is the ratio of the height of the tire's sidewall to its width (aspect ratio). 75 means that the height is equal to 75% of the tire's width.. Therefore, someone running a 70 series tire is taller than someone running aa low-profile 35 series. Then the last number represents the size of the rim in inches (a 17" rim or whatever). So, to summarize, a wheel and tire combination which in our case is 75 series and a 17" rim averages 32" in height. As N3M0 pointed out, the only real issue is the extra weight of a wider tire, thus the 285 you are referring to vs my 255. Probably not alot of difference in weight but yours would be a little wider which might cause issues on the OEM tire carrier. Hope this clears it up.

here is the definitions of tire markings:
http://b2c.sullivantire.com:8082/Tir...%20Ratings.htm

edit: I will admit that there are some wider tires that will end up "bowing up" a little more in the middle thus the height of your tire could be 33". I will admit I am not always correct but I'm pretty sure ours are about the same.
The second number in the tire size is the percentage of the wheel vs tire when you look at it from the side. BFG km2s 305/70r17s are 33.9 inches tall, 285/75r17s are 33.9 inches tall. I dont know how it make sense, but thats from tirerack.

My current rubi tires are 255/75r17s, Im not saying i totally understand how tire sizes work, but i will tell you that the tires im talking about are taller than the 255 bfg km2s. (32.1 inches tall)
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Old 07-11-2012, 06:26 AM   #12
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285/70/17's on wheels w 4.5 backspace. No lift. No rubbing on the road. You will need/want a lift for off road.
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Old 07-11-2012, 10:30 AM   #13
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Quote:
Originally Posted by BlackOpsJeep View Post
Pieface, allow me to correct you. We both have the same height tire. The only difference between yours and mine is WIDTH (the 285 vs my 255) That number represents the width, the 75 represents is the ratio of the height of the tire's sidewall to its width (aspect ratio). 75 means that the height is equal to 75% of the tire's width.. Therefore, someone running a 70 series tire is taller than someone running aa low-profile 35 series. Then the last number represents the size of the rim in inches (a 17" rim or whatever). So, to summarize, a wheel and tire combination which in our case is 75 series and a 17" rim averages 32" in height. As N3M0 pointed out, the only real issue is the extra weight of a wider tire, thus the 285 you are referring to vs my 255. Probably not alot of difference in weight but yours would be a little wider which might cause issues on the OEM tire carrier. Hope this clears it up.
.
I'm not sure that's quite right.

Just because you both have 17-inch, 75-series tires does not mean that they are the same height.

You are correct in saying
Quote:
Originally Posted by BlackOpsJeep View Post
75 means that the height is equal to 75% of the tire's width,
however by that definition a 285/75R17 must be taller than a 255/75R17.

75 percent of (285 millimeters) = 21.37500 centimeters

75 percent of (255 millimeters) = 19.12500 centimeters

With the same diameter wheel (17-inch), the 285 will be taller, as there is more sidewall. That's why the 285/70R17 is a popular upgrade. It's still larger, but not by much.

70 percent of (285 millimeters) = 19.95 centimeters

Thanks.
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Old 07-11-2012, 10:45 AM   #14
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Quote:
Originally Posted by mgola27 View Post
I'm not sure that's quite right.

Just because you both have 17-inch, 75-series tires does not mean that they are the same height.

You are correct in saying however by that definition a 285/75R17 must be taller than a 255/75R17.

75 percent of (285 millimeters) = 21.37500 centimeters

75 percent of (255 millimeters) = 19.12500 centimeters

With the same diameter wheel (17-inch), the 285 will be taller, as there is more sidewall. That's why the 285/70R17 is a popular upgrade. It's still larger, but not by much.

70 percent of (285 millimeters) = 19.95 centimeters

Thanks.
Thank you. I was waiting for someone to say that so I didn't have to.
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Old 07-11-2012, 11:27 AM   #15
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To get back to the OP's question:

Quote:
Originally Posted by PieFace View Post
Hey guys,

can I drive the Rubicon unlimited with 18/59 springs with these* tires on 4.5 inch backspaced wheels?

*285/75R17 BFG KM2
From the Largest tire on stock JK? Here's your answer! thread...

Quote:
Originally Posted by 4fit View Post
It is true that the largest diameter tire you can fit on a stock JK without issue (read on) is 33” in diameter. With this diameter, you shouldn’t have any issues on the street. However, you could get some contact with your fenders if you flex offroad. Disconnecting your front sway bar will cause contact with your fenders.
My guess is you'll rub without your lift. The 285 width won't be a problem as you'll have wheels with correct backspacing, but your diameter will almost be 34". Since a 33-inch tire "could get some contact offroad," it's entirely possible that your 34-inch KM2s will rub on the street.

I don't know if anyone has done this, though, so you might be okay. Maybe someone has done this and can confirm.

I wonder, though, why not just wait until you get the lift and be done with it? Is there a reason why you want to stuff the 285/75s on now?
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Old 07-11-2012, 11:55 AM   #16
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Originally Posted by Ottosails View Post
285/70/17's on wheels w 4.5 backspace. No lift. No rubbing on the road. You will need/want a lift for off road.
^^ this
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Old 07-11-2012, 12:06 PM   #17
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Originally Posted by BlackOpsJeep View Post
edit: I will admit that there are some wider tires that will end up "bowing up" a little more in the middle thus the height of your tire could be 33". I will admit I am not always correct but I'm pretty sure ours are about the same.
They are not remotely the same and it has nothing to do with "bowing up". Here's the math:

255/75R17

255mm x 75% = 191.25mm = 7.53" sidewall height so 7.53 + 7.53 (2 sidewalls) + 17 (rim diameter) =32.06"

285/75R17

285mm x 75% = 213.75mm = 8.42" sidewall height so 8.42 + 8.42 + 17 = 33.84".

Do you consider a 32x10" tire to be "about the same" as a 34x11"? I don't.
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Old 07-11-2012, 12:30 PM   #18
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Originally Posted by Ottosails View Post
285/70/17's on wheels w 4.5 backspace. No lift. No rubbing on the road. You will need/want a lift for off road.
dude your jeep looks awesome. if I had a silver i'd do just that.
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Old 07-11-2012, 09:29 PM   #19
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my bad....
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Old 07-11-2012, 11:14 PM   #20
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IMO if you are going to wheel it you will definitely benefit from the lift on 285/75R17's or else you will experience some significant rub. When i got my 295/70R17's installed (which measured approximately 33.5" mounted on the Jeep) I had major rub when flexing before the lift. After, no rub on my last two trips The 285/75R17's are going to be probably just under a half an inch bigger but a little bit thinner so a lift/fender trim will definitely be beneficial so i would assume they would work on road but i would be hesitant to wheel it hard before you get the lift installed. As for the tire carrier, as N3MO stated, it is largely dependent on weight. I plan on getting a reinforced tire carry because my Toyo M/Ts are pretty heavy; however, the KM2 is lighter, albeit no as light as the duratrac or an A/T. Good luck!
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Old 07-12-2012, 07:11 AM   #21
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my bad....
No worries... we're all friends here.

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Old 07-12-2012, 03:24 PM   #22
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Thanks everyone!

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