iMSQ

235/55 R18 is OEM size for 2nd Gen RX, but speedometer lies (shows more than actual).
235/60R18 has minimal speedometer error (<1 mph higher than actual speed)
245/55R18 is very close to (a little bit smaller in diameter than) 235/60R18

MattRX

The speedometer on my RX with 225/65R17 (Slightly larger diameter than 235/55R18 - not sure if speedo is calibrated) still reads slightly higher by a km or or two on the cluster. My Highlander did this too until I took apart the gauge cluster and soldered in new LEDs. You can get the speed more accurate by putting the needles back on using the scan tool for vehicle and engine speed.

Not sure if this is possible on the RX as the motors are a different style and may be CAN bus controlled.

Felix

[QUOTE=MattRX;11427241]The speedometer on my RX with 225/65R17 (Slightly larger diameter than 235/55R18 - not sure if speedo is calibrated) still reads slightly higher by a km or or two on the cluster. My Highlander did this too until I took apart the gauge cluster and soldered in new LEDs. You can get the speed more accurate by putting the needles back on using the scan tool for vehicle and engine speed.

Say hey Matt, those 225/65/17's are the standard size for the gen 2 rx's....The 235/55/18's came in a couple few different option packages & was also a stand alone option as well.....The 255's are a 29'' diameter vs 235's 28.2'' Wheel width for the 235's- 7-8.5'' where the 255's 7-9.5'' width wheels...The 225/6517's are right in the middle at 28.55'' diameter..........

mandyfig

You can use spacers , good luck.

MattRX

Planning on going with 255/50R18 if I ever decide to switch from the 245/50s, should sit right at 28” and be about 1.7% smaller than stock. Hey Felix, how do those 255s look on a 9” rim? My greatest fear is having the tire balloon like the 225/65 tires on the stock narrow 6.5” rim, my buddies always think they’re flat but they just look that way - and drive the part too! 235/55 7” rims were super rare here, I’ve only seen a handful of them.

iMSQ

Why are you looking for wide tires for SUV? Tires will not save you from rolling in a car with a high mass center if your speed at turning is too high.

iMSQ

https://tiresize.com/comparison/

MattRX

If you've been following my posts you'll know that my RX isn't your average, squishy SUV. it'll be getting coilovers soon and a bigger rear sway bar. It's going to be lowered by 3". As it sits, it's on Eibach springs, 3rd gen RX front sway bar. Body roll is very low and it is apparent the weak link is narrow rims and tires. It can now take advantage of grippier, wider tires now that the mushy stock suspension is gone.

iMSQ

OFF: My question were not "personal"...

Jride06

Can I get some thoughts on these three wheel sizes for the RX.

18 x 9.5 +22. For this one I wouldn’t know what tire size is right for this one.

19 x 8.5 +35. This I’m looking at something like 255/45 right?

19 x 9.5 + 25. And for this one I don’t know either. I wouldn’t know what’s a good size for 9.5 wide.

I don’t want to go up to a 10.5 because I just don’t think it’ll work for the offsets they offer for the wheel I want. Unless I have enough space between the wheel and strut for like a little bit more than an inch and a half but I don’t think so. But those are the three options for the wheels I want that I think are somewhat doable. Can I get some opinions?

Jride06

i like the first one because it stays at 18’ wheel. I like the second one because it’s even and I like the third because it has around the mm I want to push towards the street. I don’t have a favorite but I’d rather put what would make sense and would fit right without problems. I’m not sure if anyone would have some idea of what Can workout?

MattRX

I would steer away from 35 offset if possible, it’s getting dangerously close to the strut and trailing arm w/ wide wheels and tires and something could get jammed in there while driving.

10.5 is WIDE. That’s how wide the rear wheels are on our M3 track car with 275 rear tires on a staggered setup. I think it would be overkill for an RX unless your suspension is waaay stiffened up, the car lowered and the tires max performance summer minimum. It’s a lot of unsprung weight to add too if they’re not forged wheels and you won’t get the benefits out of it unless the tires are super wide. You might have issues up front too with something that wide at full lock, especially with a higher offset.


18x9.5 +22 is almost identical to Felix’s setup, you could easily mounted 255s or even 265s on that. I’d use Tire Size Comparison to see how close you can get to 28.5” diameter, it’ll help by giving examples too.

19x8.5 +35 wouldn’t be sticking out as much as me and the tires would he super close to strut. I still have lots of room especially in the back

19x9.5 +25 there will be lots of tire sizes available w/ 19s especially performance ones as you drop into the lower profiles.



Possible sizes (just an example):

18”
255/50R18
265/50R18
295/45R18


19”
265/45R19
275/45R19
295/40R19

Jride06

i checked out all the wheels with the tire setup and the ones that came really close to 28.5 diameter were 18x 9.5 22+ with the 255/50 tires and the 19x 9.5 +25 wheels with 295/40 tires. The first one was off by 4 mm and the second one by 3 mm. I don’t know it’s hard to choose because honestly I’d like to keep it at the 18’ wheel diameter and I would be happy with the wider wheel and then the second one I’d like the bigger wheel but to me the 295 seems like a big tire. What would yo recommend between those two. Honestly I’m leaning toward the 18 x9.5 because I feel like it’s somewhat safe and in my comfort zone but that’s because I don’t know if the 19 x 9.5 +25 is worth it with the 295/40 setup. Which setup would you chose in that situation?

MattRX

.4mm won't even be noticeable on the speedometer unless you're going 100+ mph on the highway. On my summer setup with 245/50s it's 1.5mm off and there is a noticeable but small difference while driving, I wouldn't want to go anymore than that which is around a 3% difference. I would go 255/50 for sure over 295s. 295 is massive and will be way more expensive and heavy, not to mention harder to find, and mileage will go down the toilet for no real performance gain. With those 295 tires you might find yourself tramlining like on an old 5-series wagon that we ran 265s on. I have tried 19" rims from my 2014 RX on this car and I'd rather have the 18s. 19" starts getting expensive and heavy, plus there isn't really a huge performance benefit from it either on these, at least not something you'll notice from day-to-day driving. I also think it makes the brakes look smaller even though I upsized them.

I also just saw that post of the 3rd gen RX with massive friggin' 285 tires, 10.5" wide rims and a 22mm offset. His are definitely sticking out due to the width. Member Clutchless with a 3rd gen RX runs 255/50R19 on 19x8 rims with 25mm H&R spacers and he has a little bit poking out, I'm not sure of the offset of his rims though.

Jride06

yeah that makes a lot of sense. I never go 100 mph anyway honestly I always drive safe and never go far really. Well I’m really glad I reached to the RX community because this helped me out a lot. I think I’m for sure going with the 18 because it makes sense to just stay close to stock especially if there’s no real benefit and it’s really expensive just to possibly perform worse. It wouldn’t be worth it to do that and with the 18 it’s so close to home with jeopardizing my wallet and performance. Thanks Matt for all your help and oh I know it’s late but just one more question because for the 18 x 9.5 +22 the 255 tire is 4mm and the 265 is 6 mm difference. Would it matter which one I chose or is there one that’s better out of those two? What do you think?