leton

Please bear with me. This is my first post, and admittedly I know very little about appropriate rim and tire size for my model. I have an opportunity to get a set of aftermarket rims & tires - polished lip, (19X8.5 front, 19X9.5 rear, 5-114.3 245/35ZR19 and 275/30ZR19) that look pretty nice (see attached photo). They were originally on a Lexus GS430.

However tried to put the back wheel on, and it mounts, but the tire rubs the strut. Didn't even try the front at that point. What would I need to purchase to make tires clear the strut (like some sort of spacer or adapter)? Would it be safe? How will changing from my stock tire and rims to these effect ride comfort and fuel effeciency? Any other thoughts or considerations, or is it something I should not even do?

TunedRX300

GS rims have different offset. Google and find out what wheel offset it.
You will need wheel adapters. Yes, mounting larger diameter and heavier rim/tire will not only decrease mpg but also performance and ride quality.

leton

Thanks for the reply, however now it surfaces a couple more questions/concerns.

1) How do I go about calculating what size of a wheel adapter I will need to look for? Currently I have stock rims/tires on my RX300. Is there anyone that can help me calculate what size wheel adapter I will need?

2) Currently I get approx. 20 mpg fuel efficiency. What kind of a drop would you expect if I went ahead with the change?

3) The new rims/tires (lower profile) are a little smaller in diameter, but wider tire (9.5 in and 8.5 in). Would that represent a significant loss of power to the point that it would be disappointing (I do not race, I just commute to work...mostly freeway)?

4) Lastly, I read somewhere on this forum, that going up 3 inches in rim size is fairly tolerable comfort and performance-wise but more than that becomes intolerable. Does anyone have any words of wisdom regarding that?

Thanks in advance.

sgv_bum

you should be fine on the front ..i got a set of rims from a gs430 it was 20x9 in the front offset as 38 with no rubbing problems and i could still make you turns ... the back i had 20x9.5 offset was 38 or 40 i forgot...it was rubbing so i had to put on a 25mm spacer to make it clear but it will make your rim stick out a little bit but it will give you that nice look in the back.

leton

Thanks, I'll look for the 25mm wheel adapter/spacer. I know the wheels will look much better. Does anyone have a feel for how disappointed I'm going to be in the fuel efficiency and/or comfort of ride following this change?

Francis

You should not use staggered wheels. If your RX is AWD, all size of the wheels and tires must be the same. And it makes no sense and looks funny to put wider wheels and tires on rear for FWD car. Try tirerack.com, you will get a lot of idea.

Meetya

Then you space out front tires, they will wash out much faster. Because you change mean Turning Center of the vehicle without changing angle between the two front tires (Ackermann Angle) that was designed to minimize wear of original wheels.

leton

Thanks very much for the advice/guidance. I genuinely appreciate all your input. Based upon these postings I have abandoned the idea of the rims above. I do have FWD vice AWD, however it seems as if it is essential to get rims/tires w/no adapter(s) required for best fit/performance.

I guess I'm looking for the best of both worlds. Rim/Tire size for best look and yet select one with the least adverse impact upon performance and comfort. To that end does anyone have any suggestions for me to keep in mind as I look for replacement rims/tires for my stock RX300 rims/tires.

Thanks in advance.

TunedRX300

You can use 18x7.5 or 18x7 rim to pair up with 235 or 245 tires.
I went with 18x7 forged alloy rims that weight only 15.5lbs each and 235/60/18 tires. Bought everthing used off ebay and saved major $.
IMHO, if you upgrade rims for looks and ignore about diameter and weight, it is not worth it. For diameter, here is the best calculator I found on the net
http://www.1010tires.com/TireSizeCalculator.asp

LiqrSicc

Your gas mileage will decrease noticable. I have 20x8.5 on mine right now with 245/45/20 tires and they weigh in at over 12lbs stock... maybe even more. I was getting 22 mixed hwy/city to 17 mixed. Also those rear wheels will rub, depending on the offset. A good way to determine the spacer size is 25mm = 1inch (correct me if I'm wrong.) You shouldnt need more than that if the offset is +35 or less on a 9.5" wide wheel

TunedRX300

There is ~12mm between rear strut support and OEM tire mounted on OEM 16x6.5 rim. It is not hard to figure out as you increase in rim and tire width, you start to eat into that 12mm margin.
If your wheel offset is more positive, the entire wheel/tire assembly is pushed in further. Wider tire/rim needs less positive offset to make room, or wheel spacer/adaptor is needed to increase offset externally.

I will end this post with two numbers: OEM rim/tire weights 52lbs per corner, that is 208 lbs of rotational mass an AWD RX must turn before any torque is used to push the car forward. Have you turned 200 lbs mounted on 16" of moment arm hundreds of times per minute? next time try to do that in a gym and you will understand how reasonable is to put additional mass just to gain that cool look.

leton

Thanks "Tuned" for the info above. I did visit the tire size calulator link you provided, and interestingly, if you go too large (e.g., > 3% diameter difference), the calculator warns you of the potential for brake failure. By the calculator, you seem to have given me the best rim/tire size of 235/60R18 for the best upwards fit with only a 2.41% difference in the diameter. Now all I need to do is find the right 18x7 rims you recommend, and I'll be good to go.

Thanks for all your input. You've all been great!

Rick Leton