18" Bubble Tires

[00n8]

Hi guys, new to this forum, not new to the auto world and sharing. I wrote a little guide for LX470/Landcruiser owners seeking to supercharge their rigs: https://forum.ih8mud.com/threads/hun...-guide.585427/

I searched hi and low to find this and if it's been answered, apologies.

I'm in an area with lots of potholes and I have 18" stock wheels on a 2012 E70 35d, [eddit: starting with 255/55/18 on 8.5" wide BMW stock wheels]. I'm trying to find a case study of someone with what I call "bubble wheels", the biggest sidewall, biggest tires that will fit stock without modification (not looking to trim or mess with the wheel areas).

Ideally all road/wet use.

No Off Roading will be done with this rig, maybe a little sand at the beach.

Looking to replace a set of tires and want maximum pothole protection.

Thanks for your suggestions!

[Henn28]

Search the forum for “overland” and you’ll find a great thread with a lot of good wheel and tire info for guys wanting to go bigger, and up (lift).

If you are looking for a better ride on crappy roads, you may want to consider 17 or 16” wheels. I’ve got 275/70/16 Yokohama Geolanders mounted on Method Race Wheels model 701s. Love them, but it took some work with the angle grinder to get them to play nicely with the calipers and other suspension bits. I picked them because they were one of the few that came in a 5x120 pattern and a zero offset. Total diameter is around 31.2 and they rubbed at the lock until I went at the wheel wells with a heat gun. It didn’t need too much massaging tho. I don’t think I could run them on anything rough without the 1.5” lift I’ve got on it.

5x120 bolt pattern is a limiting factor for more off road oriented stuff, but you can always go with adapters if you are ok with added complexity.

[00n8]

I don't care about off road and definately no adapters or spacers. Just looking for max sidewall. Do 17s fit around the calipers? Ideally I want to just keep the 18x8.5 I have and just get a little extra sidewall. Like 265/60/18 but I don't know if those need spacers too?

[smassey321]

I don't think 17"s will fit over the brakes. Diesel has bigger brakes than the gas I6. And V8 has even bigger.

[andrewwynn]

Look in the e53 section. Somebody did similar to your wish but they did go bigger diameter for off road.

I think the lug circles match gm 120mm or so the rims don't need to be from BMW possibly (though you may lose the hub centering).

The stock smaller rims on e53 are 17s. Tires are 235/65-17.

https://tiresize.com/calculator/

That site let's you find alternate sizes.

235/70-16 appears to be an exact match for 255/55-18. I don't know what the minimum wheel size will fit over the brake rotors but I've driven many miles on 235/65-17 and those are quite soft compared to the 255/55-18 the 235/70-16 might be all the balloon you need.

[00n8]

Originally Posted by andrewwynn

Look in the e53 section. Somebody did similar to your wish but they did go bigger diameter for off road.

I think the lug circles match gm 120mm or so the rims don't need to be from BMW possibly (though you may lose the hub centering).

The stock smaller rims on e53 are 17s. Tires are 235/65-17.

https://tiresize.com/calculator/

That site let's you find alternate sizes.

235/70-16 appears to be an exact match for 255/55-18. I don't know what the minimum wheel size will fit over the brake rotors but I've driven many miles on 235/65-17 and those are quite soft compared to the 255/55-18 the 235/70-16 might be all the balloon you need.

Sounds like the 16s won't fit over diesel calibers... Good thoughts though! Thanks.

[andrewwynn]

Unless I missed something you didn't say the size of tire you are starting with but the baseline tire I suspect is 255/55/18

Going to a wider cross section will make for a stiffer not softer ride. Thinner cross section with a taller ratio will get you a softer ride but to get more height you either need to use smaller wheels or end up with taller tires that will throw off your speedometer more than it already is (BMW speedometer reads 3mph high except in Japan).


245/60 looks promising.

[00n8]

Originally Posted by andrewwynn

Unless I missed something you didn't say the size of tire you are starting with but the baseline tire I suspect is 255/55/18

Going to a wider cross section will make for a stiffer not softer ride. Thinner cross section with a taller ratio will get you a softer ride but to get more height you either need to use smaller wheels or end up with taller tires that will throw off your speedometer more than it already is (BMW speedometer reads 3mph high except in Japan).


245/60 looks promising.

Very helpful thank you! Yes starting with 255/55/18 on 8.5" wide BMW stock wheels. Simply stated, just looking for a little taller ratio, without spacers, adapters or new wheels, if it throws off the spedo, no big deal.

[andrewwynn]

245/60 what I would use. "235" tires actually have 190mm patch so you lose a lot of grip. Slightly narrower but going from 55/60 will make for softer taller tire to remove some rattle from the pothole.

You can work on lower psi also until you find you are wearing outside tread. Maybe 30 vs. 32 psi. Three risk is hitting a deep enough hole you can have a rim strike and kill the tire the rim and the bearing.

[andrewwynn]

245/65 add 1.5" from stock. That's only 3/4 different radius but will be a lot softer ride though potholes.

I really notice the difference when I ride on my 235/65/17. Much softer ride. Really can tell the difference but I get more body roll and can't corner like I'm used to.

Nice for road trips though. Soaks up those expansion joints on the freeways.

A little math shows that with 245/65/18 you will be going 79 when the car thinks it's going 75 but it will be already be reporting 78 so it actually improves the accuracy of the speedometer.

(It will throw off mpg and possibly distance to empty but those can be corrected)