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Downsize wheel size from 20 to 18?

9K views 9 replies 7 participants last post by  Scot. S 
#1 ·
Hi, new to this site and brand new to being a Jeep owner. We just bought a 2020 Grand Cherokee Overland. It's got 20" rims on it and the tire options for 20" are not great if you want to find a good all terrain tire that allows you to do some moderate off road driving and still provide a good ride on the highway. I talked to the Jeep dealership we bought it from and they are not recommending downsizing stating the vehicle's suspension, 4WD, etc. was designed around the 20" wheel. I'm not sure I buy that, if I put a tire on an 18" rim that has the same diameter and width of the tires currently on it, should it really matter? Along the same topic, how do I find out what the offset is on the current rims that are on the vehicle? So if I do put 18s on there I can match the offset as well.

Thanks for all the input, we are very excited to be a Jeep owner and I foresee more in our future.
 
#2 ·
Agreed. The dealer just didnt have 18's to sell you so they didnt care about your question. Go for it. You should get a smoother ride out of the switch. If you cant find the offset online, you might have to just measure it. However, since a smaller diameter wheel is likely to be a smaller width, backspacing will also be an important measurement to consider. You will have to reduce the offset by the same amount as the backspacing in order to keep the outside edge of the wheel in the same location and keep the Jeep looking right.
 
#3 ·
OEM Backspacing = 56.4mm

Optimum clearance appears to be with 18x8 with 32mm backspacing.

All WK2 models can use any of the wheels for the other models with 2 exceptions.

You can't put anything smaller than 18s if you have the HD (vented) brakes that came on the towing pack and you can't run the SRT (Brembo) brakes without the SRT wheels.

If you have the standard brakes you can even run 17s from the Wrangler.


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#5 ·
JDJensen:
I've attached a picture of the stock 18" Jeep Grand Cherokee Trailhawk wheel with a stock profile A/T tire, in this a Bridgestone Dueler A/T Revo 3 265/60R18. Hope this helps with your decision. Personally, I wish there was a 17" wheel that would fit the WK2, (more tire choices) but these 18" wheels work well and I'm happy with the set up. I hope this helps with your decision.
Quadra Drive.

Wheel Tire Vehicle Automotive tire Locking hubs
 
#9 ·
Depends on the 18" wheel offset and tire and many other factors...

33x12.50 is too wide for stock offset and will rub the steering yoke (275/55R20 on OEM wheels kisses it every once in a while) so you'll need to be further away from the suspension.

I've seen 33x11.50 on OEM wheels but anything wider is on a different offset or spacers. And "technically" most 12.50 tires call for a 9-10" wide rim for the best profile as well.

It also depends on the tire as some 33s are very close to a full 33" diameter but some (Nitto, BFG, etc) are closer to 32.5" mounted.

18x10 with a 0mm offset and 33x12.50 would probably clear suspension with 2.5" kit (especially if you use the leveling puck up front) but you might hit the front fender lip at full lock depending on sidewall and/or tread pattern...YMMV.

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