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I am considering getting a set of low profile tires for my RX400h when I replace my tires sometime in the near future. Reason being, they will have less weight and will lower the vehicle approximately 1.5" (tire size 235/45r18 vs 235/55r18). Less rotational mass and lower ride hide should equal improved fuel economy. Anyone want to chime in with why this is a bad idea? The load rating will go from 99 to 94 (1709lbs to 1477lbs) but that shouldn't matter should it? GVWR of the vehicle is 5520lbs, or 2865lbs max front or rear. The vehicle's curb weight is 4365lbs (AWD), so even if I was carrying 5 200lb people, I would still have 155lbs before hitting GVWR. Even so, 94 load index tires are rated for 1477lbs each, which would be higher than the weight limit max for front or rear. Thoughts?
Again, main objective would be fuel economy as I do a lot of highway driving where aero comes into effect. I have a dedicated set of winter tires/wheels already, so these would be for warmer weather, 3 seasons of the year.
Smaller diameter wheel and tire will rotate more times per mile than the larger size.
The engine will also be rotating more, my assumption is that MPG will decrease rather than increase.
Consider getting Low Rolling Resistance tires in the stock size if mileage is your principle concern.
Smaller diameter wheel and tire will rotate more times per mile than the larger size.
The engine will also be rotating more, my assumption is that MPG will decrease rather than increase.
Consider getting Low Rolling Resistance tires in the stock size if mileage is your principle concern.
thanks for the reply. Part of my consideration is that the rx400h has a CVT, so I do not know whether or not the engine would actually be running at a higher RPM regardless of speed.
Don't forget about the speedometer error! tire calculator
PS: On 235/55 R18 my actual speed was ~2 miles less than actual by radar or GPS. Now I am on 235/60 R18 (and this is the biggest possible diameter for the rear wheels).
On 235/55 R18 my actual speed was ~2 miles less than actual by radar or GPS. Now I am on 235/60 R18 (and this is the biggest possible diameter for the rear wheels).
That was my experience also. When I was researching, I saw that Lexus started using the 235/60/R18 on the 3rd gen. So I calculated the speedometer error percentage and the tire size difference percentage and they were a match, so I got the 235/60/P18.
Thats what im thinking of now. Have you had any issues with handling or steering with the larger tires? width is equal, I see, but being taller i just wonder if there is any downside?
Thats what im thinking of now. Have you had any issues with handling or steering with the larger tires? width is equal, I see, but being taller i just wonder if there is any downside?
Why not go w/ a 255-55x18 tires? Yea if your running the oem 7'' width wheels as that be the smallest width to run thou.....as a 255 you could run a 8.5''-9'' width wheels.....Have you thought of 8.5'' width wheels w/ a 20mm offset? Thats if your looking for a tad bit of track width....
06-25-19, 08:12 AM
Call me crazy.... Low Profile Tires on an RX?
