Nayethar
Posts: 1
Joined: Mon Feb 10, 2020 6:03 am
Location: Santa Clara, CA

18 inch versus 20 inch tires

Mon Feb 10, 2020 6:20 am

Is there any advantage to having 20-inch versus 18-inch tires on your RV? I can't see an advantage, but I wanted to see if I was missing something?

joni3s
Posts: 45
Joined: Wed Oct 02, 2019 11:16 am
Location: VA

Re: 18 inch versus 20 inch tires

Mon Feb 10, 2020 10:11 am

I am not aware of any typical 18s available to the i3 vehicle (RV?).

Advantage is aesthetic, road feel response and handling. wheel diameter is similar for 20&19.

19&20 differences are mostly sidewall ratio, tire compound availability, tire choice, rim width choices, staggered, square

IIRC the contact patch is similar between 19 & 20
2018 I3s rex

robthebold
Posts: 92
Joined: Sat May 11, 2019 5:09 pm

Re: 18 inch versus 20 inch tires

Mon Feb 10, 2020 9:26 pm

Physics is pretty hard-donkeyed about that. The total contact patch depends only on the weight of the vehicle and inflation pressure. Any persistent imbalance would result in the car being sprung off the face of the earth or sinking into its infinite depths. So for a constant inflation pressure -- regardless of the geometry of the tires -- the total contact patch (in square inches) for a vehicle at rest is: Weight of car / PSI of tire inflation. A 6000 pound car sitting on 60 psi tires requires 100 square inches of contact for the earth to be pressing up on the tires exactly as hard as the tires are pressing down on the earth. Whether these tires are skinny or fat, short or tall, ultimately the area pressing against terra firma is the same.

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MKH
Gold Member
Posts: 521
Joined: Fri Nov 02, 2018 5:48 am
Location: Dallas

Re: 18 inch versus 20 inch tires

Tue Feb 11, 2020 5:10 am

Is there any advantage to having 20-inch versus 18-inch tires on your RV
The difference is the 20 inch rims your option is only the low-sidewall summer/sport tire. On the 19" rim, your option is the higher-sidewall all-season tire.

The all-season tend to last longer. The 19" with the higher sidewalls are less prone to pot-hole damage to the rims and tires, and the ride is less harsh. I had 20" sports tires on mine, and in the first 4 months, bent all the rims, and ruined two tires hitting potholes. Since switching to 19", no further damage, and a better ride. The 20" may be fine for the well maintained autobahn, but on bad surface streets, not so much.
Mark H.
2015 i3 Rex, Capparis White, Tera World, Technology & Driving Assistant, Parking Assistant, Harman Kardon Audio System, 19 inch 427 wheels, EVoInnovate EVSE

joni3s
Posts: 45
Joined: Wed Oct 02, 2019 11:16 am
Location: VA

Re: 18 inch versus 20 inch tires

Tue Feb 11, 2020 10:03 am

lastly, the wider 20" 431 style rims have a larger patchable area due to the them being wider.

Additionally, folks have install even wider non ecopia tires (Potenzas) on the 431s (maybe 10-20mms wider depending on rim).
2018 I3s rex

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