Winter tires, downsizing rim size.

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So I'm playing with the idea of buying dedicated winter tires, on rims so I can swap and go when need be. I haven't had a real winter consistently around here, few weeks here and there. Last year was decent, but the A/S Dunflops did reasonably well on the roads. I had a bad day getting up to Mt. St. Helens, specifically pulling too far off the road to let pickups with trailers pass on a narrow road, and making the mistake of coming to a complete stop. The AWD system on this car is a gimmick, plus disengagement of traction control does not work with the Lexus cars, IDK why the need the play God there, but whatever. So, there are infrequent events of need for a better winter tire.
I've been looking for rims and the OE size ranges from 18" and up, width between 7.5 and 9, with the average offset of 35. Looking around the web and trying to make sense of things with no real knowledge, it seems I can get away with 17" rim for sure, and other cars getting away with 16" rims for similar brake rotor size.
What do I do to figure out the minimum rim size for (any) car?
 
You have a super common bolt pattern. Just find/borrow some wheels in different sizes to see what fits. I run 14" front and 15" rears on my mr2 in the winter and although everyone says 14s won't clear front brakes, they fit fine. Just have to try. Online calculators will only be so accurate. Also everything is different on every car. I've seen cases of wheels not clearing on one car but clearing on another with exactly the same brake caliper and rotor. Online calculators say my summer wheels should hit the strut in the front but I have 5 to 8mm of clearance. Just have to try and fit some for yourself.
 
Tire rack is a great resource but their calculator is all but perfect. There are hundreds of accounts of people buying wheels from tire rack that it says fit fine but do not actually fit at all. Tire rack says a 7.5" wheel with 40mm offset fits the front my my mr2. In reality that would not even be close to fitting.

Need to do your own homework.
 
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I assume you are talking about the RX450h. If the OE size was 18" and you want to go down, you need to make sure it clears the caliper as you said. I would joist mount up a 16" Toyota wheel, which are as common as sin, and see if it fits. Is your RX450h (is that what you are talking about?) the Toyota car 5-bolt or truck 6-bolt pattern?

You could also check a place like tirerack.com. They have online fitment apps for vehicles and it may include information if -2 (which is what you asking about) would work.

Another thought, since we live in apparently the same climate (I am in the Cascade foothills around Snoqualmie/North Bend), would be to put A/t tread m/s rated tires on it and use them year round. That is what I have on my SUV and it is more than adequate for the occasional trip to the mountains in winter, with chains in the back for emergencies (have not used in many years).
 
Originally Posted By: LotI
Hundreds?

OTOH, TR said a 17x7" wheel from my Accord wouldn't fit my Mazda6, bit it was fine.


Most of their issues are failure to account for offsets with cars where the front struts are close to the wheel. 350z, g35, lots of Toyota's, new mustang, and a few others are primary offenders.
 
Yes the RX.
The tire rack is useless when it comes to downsizing beyond OE recommendations. I don't really have any available rims to play with, other than the 17s off the IS, and some 15s from the Jeep and my old J30. I would like to be able to crunch numbers instead of throwing parts, but if no one here knows a certain way...
Originally Posted By: Oro_O
the Toyota car 5-bolt or truck 6-bolt pattern?



5x114.3 aka 5x4.5, the most common thing out there "."
 
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I mean you can put a wheel on the car, try and measure the space from the top of the caliper to the wheel. That will give you the space you have to play with. So when changing one size down at a time, you will be getting the wheel 1/2 inch closer to the caliper.
 
What size is on your car now? 18 or 19 inch? Both OE sizes have reasonable sidewall ratios of 55 and 60, at least as reasonable as it gets these days. 235/60-18 or 235/55-19.

Your case may call for an "all weather" tire, which is an all-season tire with the mountain-and-snowflake symbol, or a winter tire that can be used year-round. Examples include the Toyo Celsius, Nokian WRG3, Vredestein Quatrac 5, and Goodyear Assurance WeatherReady.

You might also be able to find an A/T tire that gives you acceptable winter performance.

Also, keep in mind that the worst winter tire is better in winter than the best all-season tire, even if you don't minus-size
smile.gif
 
Good point, I'll measure clearance between the rim and caliper. thanks for helping me pull my head out of the overthinkibg hole
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Anytime. Been there and done that. I've owned probably 30 sets of wheels in the last 7 years or so for lots of different cars. All aftermarket. Definitely understand how figuring all this out can be frustrating. I have bought wheels I have thought would fit that did not more than once.
 
FWIW they never put a 15" wheel on a chevy HHR but I found some that fit.

You might want to see if maybe the canadian or 3rd world version of your car ever came with a size smaller.

In my example the HHR has the same floor pan, subframe, struts and brakes as a chevy cobalt that rolls on 15s.
 
Highly doubt anything below 17" can go on that car. I know it is Lexus and not Porsche, but still has decent rotors and calipers.
Anyway, it is not the rim that is important, it is width of the tire. What you really want in winter is narrower tire. So you need to see what is narrowest size you can go.
However, not sure what you will get there if winters are not bad. If you make just occasional trips to mountains, I would stay with regular size tires, just get different wheels and put winter tires. Smaller tires or narrower tire will affect other performance aspects, so unless you very often experience snow, there is really no benefit there, but then you are affecting performance when you drive in dry or wet.
Also, think what kind of tires to get. Again, if not often in mountains get something like Michelin X-Ice that have good longevity and ice performance, but not so much deep snow performance.
 
Originally Posted By: JC1
Originally Posted By: LotI
Tire Rack


+1 check the online tire sites that will tell you the minimum tire Size that fits.


This. Just call them. They are very knowledgeable and you will have a guarantee that everything fits. If you belong to a Lexus forum, there is probably TR rep on the forum specializing in your needs.
 
The RX sits at over 4500lb, so the 235 is plenty narrow. Definitely going with actual winter tires, because where I go in the winter, either has really bad road conditions, including slopes and no room for error, or areas that do not have anyone around for miles, hours and no phone reception. Besides, if the weather is good, they will just camp in the garage. The brakes are supposed to be undersized on hybrids, but that was from a Wikipedia article, and whether it's legitimate or not, who knows.

Also, the backspacing is backwards as I understand, right? Smaller number will push out more?
 
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The hybrid uses a different AWD system. It uses an electric motor to drive the rear wheels. Not a powerful motor though.

I would look at its sister car, the highlander for a smaller wheel size if possible
 
Originally Posted By: Dyusik
The RX sits at over 4500lb, so the 235 is plenty narrow. Definitely going with actual winter tires, because where I go in the winter, either has really bad road conditions, including slopes and no room for error, or areas that do not have anyone around for miles, hours and no phone reception. Besides, if the weather is good, they will just camp in the garage. The brakes are supposed to be undersized on hybrids, but that was from a Wikipedia article, and whether it's legitimate or not, who knows.

Also, the backspacing is backwards as I understand, right? Smaller number will push out more?

Yeah, 235 is narrow enough. By the way, Michelin X-Ice Xi2 Latitude are real snow tires (I actually got them for next winter, to try them too).
IMO, I would go with those, or Bridgestone Blizzak DM-V2 (I had them last two seasons, good in deep snow, not so much on ice), Continental Wintercontact SI, Noakian Hakka. R2. Those are usual suspects.
Only Michelin has warranty, 40K.
 
Originally Posted By: Dyusik
The RX sits at over 4500lb, so the 235 is plenty narrow. Definitely going with actual winter tires, because where I go in the winter, either has really bad road conditions, including slopes and no room for error, or areas that do not have anyone around for miles, hours and no phone reception. Besides, if the weather is good, they will just camp in the garage. The brakes are supposed to be undersized on hybrids, but that was from a Wikipedia article, and whether it's legitimate or not, who knows.

Also, the backspacing is backwards as I understand, right? Smaller number will push out more?


If the RX is just for bad conditions only, why not consider studded tires? The rear electric motor isn't that powerful for the tricky stuff. Going down steep descents, the best studless winter tires are not enough. You really need something that actually bites down into the packed snow and ice, which is either chains or studs.

I would spend the extra money and look for a studded tire that is studded from the factory. This way you have the benefits of the unique stud designed for that tire, whether it be Nokian Hakka 8 SUV, some sort of Gislaved NordFrost studded, etc.
 
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