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Downsizing rim size

1371 Views 12 Replies 11 Participants Last post by  Rubik0nkidd45
I have an 04 Rubicon with the stock 16" rims on it. Can I drop down to 15" rims or will my brake calibers rub. Thanks.
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you can drop down with no issues as long as your on stock brakes.....but it seems more and more tire manufacturer's are dropping the 15" size on their tires. but lots of guys do it.
I opted for the 15 in rim on my 04. Like Jimmy said, no issues with stock brakes.
I am running 15" rims, but in retrospect wish I had gone with 17". Options for larger tire sizes are getting very limited with 15" rims. Plus now that I'm running 37" tires, a major brake upgrade is likely in my future, and would really like to get the Vanco upgrade that requires 16" rims.
I'm running 15" rims with 35s on my 04 Rubi with no problems. I went that route just because of tire cost. For some reason the tires for 15s are much cheaper. So far, using 35s, I haven’t had any problems getting the tire I want. Going larger might start bringing out some issues though.
15's on my '05... Did it and haven't looked back.
Thanks for all the replies. I am running stock brakes. I too want to go to 15" rims because of tire cost.
I vote 17s with JK rubi tires...

But I just like 17s.
It's not like there is no downside. Ideally for safety, handling precision, and to better protect the tire when aired down, you want the wheel to be half of the total tire diameter, and the rubber to be half. The further you get from the ideal formula, the lower the performance both onroad and offroad.

15" wheels should be OK with up to about 33" tires. 16" wheels OK for up to about 35" tires. 17" rims for up to 37's.
I run 15's and 35" tires on my 06. No problem here either.
I get nice tire wrap when aired down to 10lbs but they aren't so flat I have to worry too much about them.
KaiserJeep said:
It's not like there is no downside. Ideally for safety, handling precision, and to better protect the tire when aired down, you want the wheel to be half of the total tire diameter, and the rubber to be half. The further you get from the ideal formula, the lower the performance both onroad and offroad.

15" wheels should be OK with up to about 33" tires. 16" wheels OK for up to about 35" tires. 17" rims for up to 37's.
Not to pick, but the formula for on road is actually 75% of your tread width should be sidewall for optimal ride and comfort. i.e. 235/75R15 tire is expressed as:
235mm tread width
75% of tread width is sidewall height, or 176.25mm

Lots of studies have been done to provide this formula.

As for off road, you're right, most people agree that your sidewall should be no less than half your rim diameter. i.e. Take your rim diameter and multiply it by 2 and that's the smallest tire you should run for optimal off road performance.

Sorry to thread jack, just wanted to make sure the formulas were correct.

A good point was also brought up about brakes... As soon as you go with larger tires, your brakes effectiveness start to decrease and larger brakes require larger rims.

I went to smaller rims because both tire cost, and more sidewall for off road performance.

Cheers!
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I'm running 35" tires on 15" wheels with EBC brake pads and love the set up. My KM2's were cheaper with 15" wheels and i love how my 04 handles the trails. Absolutely no issues.
Does anyone have any info on running a 35" MTR on a 17" rim?
Also I wonder if anyone had any pics! Just to see what they look like!? Thanks
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