Can I put 18" tires & rims on 20"? - JeepForum.com
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post #1 of 13 Old 03-11-2021, 05:13 PM Thread Starter
sam_234
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Can I put 18" tires & rims on 20"?

Like it says,

I have a Jeep grand cherokee with 20" wheels (Summers} and I wish I could just trade them in for 18" in the winters.

Say it's so.

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post #2 of 13 Old 03-12-2021, 12:19 PM
222Doc
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the wheel size is just the hole in the tire. In theory it could be any size under the tire size. example a 35" tire on 15" wheel is the same as a 35" tire on say 24" wheels. Its still a 35. just tire has a smaller whole or bigger hole. So yes you can run 18" wheels just keep same tire SIZE in Diameter. what ever that is for that jeep.

18 will ride better then a 20. especially on small tires like say 30" and under. 17 would even ride better yet if they fit and would cost far less then any 18" or 20" tire. Vehicles with 20s and up tend have heavier tire and wheel weight too. Wheels tend to be much heavier then the rubber per inch. Unless the 20s are say made very light Forged or other higher tech way to make them that cost BIG money.

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post #3 of 13 Old 03-12-2021, 04:52 PM Thread Starter
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hey, thanks for the reply!

But then there's brakes, and yadda yadda yadda. So I can put 18"'s on my 20s?
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post #4 of 13 Old 03-12-2021, 05:10 PM
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You cannot put 18" tires on 20" wheels.
You can put 18" tires AND 18" wheels on your Jeep.

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post #5 of 13 Old 03-12-2021, 06:26 PM
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There is a minimum wheel size that can be run on a vehicle due to the size of the brakes, but I don't believe any year Grand Cherokee requires at least a 20" wheel. If your particular year Grand was offered with 18" wheels from the factory, you should be able to drop down to that size -- you'll still need to make sure the wheels you use have the appropriate offset or backspacing though.
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post #6 of 13 Old 03-30-2021, 08:51 AM
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Quote:
Originally Posted by Kruzin View Post
You cannot put 18" tires on 20" wheels.
You can put 18" tires AND 18" wheels on your Jeep.
18" tires might be a tad bit small for a Jeep, like any adult size Jeep at least....


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post #7 of 13 Old 03-31-2021, 09:16 AM Thread Starter
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Holy macrel - took me three weeks to find this thread again. i'm sure I just got confused about subscrpitions.

So, the long and the short of it is, I basically don't want skinny minny 20's on the vehicle for the winter. (Ya, I'm thiinking of winter already.) I'd like some big meaty 18" tires and wheels for traction etc

Obviously I can't put 18" tires on 20' rims.

But can I squeeze 18' wheels and tires around the 18" brakes on a 2015 Grand Cherokee. With proper offests? I'm sorry if wasn't cear before.

This Answer from Mukluk appears to be the closest to reality. If I want Wrangers (i do) I suppose the easiest is to jut go into a firestone dealer and say "Can you make them fit?" - but i wanted to doube ckeck,

Thank for your your patience.
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post #8 of 13 Old 04-16-2021, 11:11 AM
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Quote:
Originally Posted by sam_234 View Post
Holy macrel - took me three weeks to find this thread again. i'm sure I just got confused about subscrpitions.

So, the long and the short of it is, I basically don't want skinny minny 20's on the vehicle for the winter. (Ya, I'm thiinking of winter already.) I'd like some big meaty 18" tires and wheels for traction etc

Obviously I can't put 18" tires on 20' rims.

But can I squeeze 18' wheels and tires around the 18" brakes on a 2015 Grand Cherokee. With proper offests? I'm sorry if wasn't cear before.

This Answer from Mukluk appears to be the closest to reality. If I want Wrangers (i do) I suppose the easiest is to jut go into a firestone dealer and say "Can you make them fit?" - but i wanted to doube ckeck,

Thank for your your patience.
For future reference, this is all covered in the stickies in the WK2 section.

What engine? The Hemi and Diesel come with HD brakes and can’t run smaller than 18’s w/o 1”+ spacers. Easiest way to tell is to see if your rear desks are vented or not. Vented=HD brakes, not vented=standard brakes and 17’s should fit. If you want to stay stock diameter, use a wheel calculator to see what tire to run, but OEM on the 18’s is 265/60r18.

I’ve destroyed my OEM 18” Trailhawk wheels off road, so I just grabbed a set of JL Sahara take-offs.
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post #9 of 13 Old 04-20-2021, 09:10 PM
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Originally Posted by gspfunk View Post
...can’t run smaller than 18’s w/o 1”+ spacers.
This seems like a generalization. I assume you mean they can't run a stock 18" Jeep wheel, because you could get an 18" aftrrmarket wheel with more caliper clearance or less backspacing if need be. My Fusion Sport has the same issue with having to be selective about fitting 18" wheels, but I don't think I've seen anyone say wheel spacers are the solution.
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post #10 of 13 Old 04-21-2021, 11:12 AM
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Originally Posted by BOT ROCKET View Post
Quote:
Originally Posted by gspfunk View Post
...can’t run smaller than 18’s w/o 1”+ spacers.
This seems like a generalization. I assume you mean they can't run a stock 18" Jeep wheel, because you could get an 18" aftrrmarket wheel with more caliper clearance or less backspacing if need be. My Fusion Sport has the same issue with having to be selective about fitting 18" wheels, but I don't think I've seen anyone say wheel spacers are the solution.
18’s work fine. With 17’s, they have more than just a little interference with the caliper on HD brake-equipped Jeeps. The HD brakes use a different bracket than SD that pushes them out (along the face of the rotor, not toward the outside of the vehicle) to accommodate a 20mm larger rotor.

Caliper clearance is one of the big reasons you see so many people running spacers.

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post #11 of 13 Old 05-20-2021, 01:07 PM
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Quote:
Originally Posted by gspfunk View Post
18s work fine. With 17s, they have more than just a little interference with the caliper on HD brake-equipped Jeeps. The HD brakes use a different bracket than SD that pushes them out (along the face of the rotor, not toward the outside of the vehicle) to accommodate a 20mm larger rotor.

Caliper clearance is one of the big reasons you see so many people running spacers.
That's what I mean. Spacers don't increase the inner diameter of the wheel drum, so what do spacers have to do with making larger diameter brakes fit unless the point is to get the brakes sit completely outside the wheel drum, or if the wheel design (such as stock wheels as I mentioned) had a larger diameter toward the back of the wheel drum.
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post #12 of 13 Old 05-21-2021, 09:16 AM
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There are 2 main issues. 1) the inside diameter of the wheel decreases closer to the face of the wheel. 2) the face of the 17” wheels is flatter, or even a little concave vs the convex face of all the 18 WK2 wheels. Spacers push the wheel far enough out that it clears both of those.

From what I’ve seen, most people are having to run 1.25” spacers, which is a LOT, IMO. However, there are a lot of people running that setup, so it obviously works.
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post #13 of 13 Old 05-21-2021, 10:34 AM
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yes....

















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