18” wheels on RX mk3

Vadim · November 2, 2021

For those who have been thinking of a spare set if wheels for winter, or a 18” wheel rims, here is an example.

Wheel rims: 7.5Jx18 ET35 (from Lexus NX)

Tyres: Continental CrossContact LX 255 60 R18

18” tyres are noticeably softer on ever degrading London roads, and wider tyre profile (255 vs 225mm) protects sensitive diamond-cut wheel rims from curbing.

This size of tyres is standard for Nissan Navara, Range Rover Discovery, VW Amarok, Jaguar F-Pace etc., and often can be sourced as a set in near-new condition for a fraction of original price.

Vadim · November 2, 2021

Toyota/Lexus has its own specific centre bore size (60.1mm) which is critical for correct wheel positioning on wheel hubs. For this reason those who look for alternative wheel rim options have to stay within Lexus/Toyota domain even when the rest of the wheel rim dimensions appear similar.

Vadim · November 2, 2021

Refreshing lug nuts: Mitsubishi uses exactly the same lug nuts on Outlander, Shogun and some other models. Due to relative unpopularity of Mitsubishi brand their original lug nuts can be sourced at a significant discount.

Greg B · December 7, 2022

Hi mate,

I am planning to go the same route. Have you noticed any issues with rubbing under load(4 people plus luggage) or when turning etc.?

Best,

Greg

Vadim · January 29, 2023

On 12/7/2022 at 5:07 PM, Greg B said:

Hi mate,

I am planning to go the same route. Have you noticed any issues with rubbing under load(4 people plus luggage) or when turning etc.?

Best,

Greg

Sorry for late reply. It has been 2 years since I changed the wheels, and there has been no issues: road humps on everyday school runs in London, full-load trips to France and Italy. However, it should be noted that I have air suspension model, which levels to neutral position regardless of the load. With coil spring suspension under extreme loading the rear tyres may come closer to the internal walls of the wheel arches. But you won't bring 20 bags of cement at a time in these cars anyway.

Barry14UK · January 30, 2023

Useful info Vadim. Some aftermarket wheels are provided without lug holes and can be bored out to any bolt pattern. I had this done many years ago for one of my cars (can't remember which one). Of course rim size and offset also needs to be correct.

Vadim · January 30, 2023

7 hours ago, Barry14UK said:

Useful info Vadim. Some aftermarket wheels are provided without lug holes and can be bored out to any bolt pattern. I had this done many years ago for one of my cars (can't remember which one). Of course rim size and offset also needs to be correct.

In the UK any customisation may cost a fortune.

Νote also that on Toyota/Lexus the wheel rims are centered on the hubs by the centre hole, not the nuts. A part of this hole is conic (narrower inside), and has to be done to the spec precisely.

Barry14UK · January 31, 2023

19 hours ago, Vadim said:

In the UK any customisation may cost a fortune.

Νote also that on Toyota/Lexus the wheel rims are centered on the hubs by the centre hole, not the nuts. A part of this hole is conic (narrower inside), and has to be done to the spec precisely.

That's interesting and restrictive, so means for example that wheel spacers should not be used, although I thought I had read somewhere that somebody had done so.

My E39 BMW is fitted with wheels from an E60 or E61 but the centre hole on each wheel had to be bored out to original spec as the earlier E39 bore is larger. This must be quite a common mod as I have a second set of wheels where this has been done. The rims are secured by typical conical headed bolts rather than square shouldered nuts that Lexus use.

Vadim · February 6, 2023

On 1/31/2023 at 1:47 PM, Barry14UK said:

That's interesting and restrictive, so means for example that wheel spacers should not be used, although I thought I had read somewhere that somebody had done so.

There are wheel spacers with centre bore extension (the cylindrical part sticking out) to imitate Toyota spec:

Barry14UK · February 6, 2023

Something else that could be worth noting!

Vadim · February 26, 2023

18” wheels upgrade

Wheel rims from Lexus NX (18”, 7.5J, ET35), tyres 255/60 R18.

No curbing and noticeably softer ride compared to stock 19” 235/55 R19.

Las Palmas · February 26, 2023

255 vs. 225 on 7½” wheels.

I find 225 an OK size to 7½” (187,5mm). 255 will be floating instead of steering in the direction the front wheels are pointing. To have 255 tyres I think that any rim not at least 8½” will be too narrow.

Here I am pretty sure they would not be permitted. Rightly so in my opinion.

If wheel offset value is equalized with spacers, spacers are OK; if spacers change the width difference of the middle of the tyres changing the steering characteristic the factory think is correct, it better be made by somebody with more knowledge than the people calculating such things in the factory. Such people are working in Formula 1 and rare to find.

Instead of 235/55/19 I think that 235/60/18 will be a reasonable change with a bit softer ride and minimal difference in most other things.

235/55/19 will have 442 revolutions each km

235/60/19 will have 443 revolutions each km

255/60/19 will have 429 revolutions each km

NemesisUK · February 26, 2023

58 minutes ago, Vadim said:

18” wheels upgrade

Wheel rims from Lexus NX (18”, 7.5J, ET35), tyres 255/60 R18.

No curbing and noticeably softer ride compared to stock 19” 235/55 R19.

And your speedometer will be under reading by a significant amount?

Las Palmas · February 26, 2023

Sorry !

Big typing mistake:

Wrong:

235/55/19 will have 442 revolutions each km

235/60/19 will have 443 revolutions each km

255/60/19 will have 429 revolutions each km

Correct:

235/55/19 will have 442 revolutions each km

235/60/18 will have 443 revolutions each km

255/60/18 will have 429 revolutions each km

Vadim · February 27, 2023

On 2/26/2023 at 5:20 PM, NemesisUK said:

And your speedometer will be under reading by a significant amount?

The 255/60 R18 have slightly larger external diameter, but the speed measurement actually becomes closer to GPS reading. It seems that the speed indicator over-reports by about 5% with stock wheels, which is common for modern cars in general from my experience.

Here is the tire dimensions comparison by one of the tyre calculators:

Vadim · February 27, 2023

On 2/26/2023 at 4:54 PM, Las Palmas said:

255 vs. 225 on 7½” wheels.

I find 225 an OK size to 7½” (187,5mm). 255 will be floating instead of steering in the direction the front wheels are pointing. To have 255 tyres I think that any rim not at least 8½” will be too narrow.

It is a matter of personal preference, I assume. You can find 255 tyres even on 7J wheel rims (Nissan Navara, for instance). It steers well.

The point here is to use wider tyres to protect the wheel rims from curbing, which is a common problem for city dwellers.

Some time ago manufacturers started using tyres which are almost flush with wheel rims, so that a lightest touch with a curb leads to scratches. I would not bother if I did not damage a set of almost perfect wheels in the first two days after buying this car.

As per offset, ET35 provides sufficient clearance for 255/60 R18, so that there is at least 5-7mm to closest parts of wheel arches (with stock tyres it is about 10mm). As tyres wear the clearance increases.

More rubber on the wheels also offsets some of the notorious stiffness in the pneumatic suspension of the 3rd generation RX.

Las Palmas · February 27, 2023

1 hour ago, Vadim said:

It is a matter of personal preference, I assume. You can find 255 tyres even on 7J wheel rims (Nissan Navara, for instance). It steers well.

The point here is to use wider tyres to protect the wheel rims from curbing, which is a common problem for city dwellers.

Some time ago manufacturers started using tyres which are almost flush with wheel rims, so that a lightest touch with a curb leads to scratches. I would not bother if I did not damage a set of almost perfect wheels in the first two days after buying this car.

As per offset, ET35 provides sufficient clearance for 255/60 R18, so that there is at least 5-7mm to closest parts of wheel arches (with stock tyres it is about 10mm). As tyres wear the clearance increases.

More rubber on the wheels also offsets some of the notorious stiffness in the pneumatic suspension of the 3rd generation RX.

Offset is about geometry in the steering gear. At least that is what car manufacturers tell, not about clearing. Changing steering geometry is not something I recommend.

Many companies make tyres with rim protection.

Nissan Navara is a truck. RX is in my opinion a car. A big one, but not a truck.

But you are right that more air volume make softer suspension.

Vadim · February 28, 2023

I forgot to mention the comparison of wheel rim dimensions and the offset:

RX450h mk3 stock rims:

7.5jx19 ET35

NX (the ones featured above):

7.5Jx18 ET35

So that the wheel rim geometry and offset are exactly the same except the rim diameter.

255mm tires add 10mm width each side compared to 235mm stock tires, that is 4.2% of tire width increase. But the tire centre line remains the same relative to the rest of the car.

Given that RX mk3 is barely a high-performance sport device (particularly in EV mode), this - in my experience - does not affect steering experience and high speed stability.