Help understanding recommended wheel width

[Black1500Ram]

Hi Guys,

I'm trying to wrap my brain around why two sizes of the same brand and model tire, LT275/60/20 and LT275/70/18, both ~ 33" tires, have an inch difference in approved rim width (7.5-9.5" for the 20's and 7-8.5 for the 18's). Exact same weight ratings etc. Everything is the same but size.

I have these tires on 20x9 at the moment and they're wide for size giving me plenty of protection for my rims.

Planning on running the 18's on 18x9 wheels. Penny for your thoughts?

James

 

[Black1500Ram]

Found this video on custom offsets of a matchup 275/70/18 on an 18x9 and it looks exactly the same as my 20x9 on 275/60/20 does in terms of wheel protection (tire width > wheel width).

Custom Offsets Matchup 275/70/18 on 18x9

 

[crazykid1994]

A lot of the reason may be due to sidewall flex. Not saying you can’t do it. I’m looking at swapping to a 285/75r18 from my 305/70r18 when the time comes so I can have less road drag and a lighter weight tire. I run a 18x9. My wife’s old truck had 16x9 and 305/70r16 which is a 33. I cracked a rim and had to buy her new since the ones she had were not made anymore. I remember swapping to stock wheels which were a 16x7 for her truck. They were definitely to wide for the wheels and the sidewall was bulged looking. Swapped to a 285/75r16 and the fit was night and day better. I know that’s more of an apples to oranges situation but that’s what I’ve seen in my experience.