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Have been reading many threads in this forum after finding out my newly-ordered NX comes with run-flats, and I've been losing sleep while waiting for my car to arrive.
1. Are the Modern Tire and the Lexus factory spare both run flats or regular? Are they regular size same as original or are they "spare-sized"?
2. Has anyone had issues with tire dealers not installing regular tires on cars coming with run-flats (e.g. found thread elsewhere Costco refused saying not "OEM").
3. Are these run-flats that have the stiff walls or are they the self-sealing?
4. Has anyone had issues getting a run-flat puncture within tread plugged?
5. Does Lexus tune the NX handling specifically for run-flats and are there handling issues changing to regular?
6. If the tire sensor indicates low pressure, or if slow leak, can air be added to run-flats?
7. Will fix-a flat or tire repair/compressor kit help seal a slow leak puncture?
Don't lose sleep over an owner changeable car part!!
1. Spares are regular. They have to be approx' the same diameter to keep the wheel speed computer happy, altho narrower. The hybrids do not have a factory spare. The Modern Spare can be run at full legal speed.
2. That would come from idiots that puff their chest out trying to sound intelligent. Simply go somewhere else if you experience that. I have one Costco that are jackasses and one that is mostly "workable".
3. Stiff walls. Mild disappointment on ride softness from traditional Lexus customers.
4. No more than any other tire and shop. I just had Discount refuse a puncture repair on a new regular Conti in the middle of the tread because I was in a hurry and stuck. They would only sell a new tire. Took it and went somewhere else.
5. This isn't Nascar/F1. NX has mild complaints of stiff ride. Most people like switching to regular tires.
6. It is an air filled tire with a tire valve, hence, you can add air????
7. Those products will fix any tire made outta rubber, BUT, make sure you get sensor compatible fix a flat if you must use it. Tire shops don't like to clean that sticky mess off a rim at tire change time. Doesn't matter the sidewall construction.
Modern spare was my solution and I'm at 50,000 miles with a tire change to Michelin CC2, mostly for winter/gravel conditions and miles warranty. I do lose some (2-3??) hybrid mpg.
Thank you for a quick reply. Like I said, they were naive questions! I have CC2's on my ES (will be trading) and RX now, love them. Do you know what brand the runflats are with 2025 NX? I hate the thought of having to find another with a blowout. I"m assuming if once plugged, the run flat would not necessarily have to be replaced? Still, gives me 2nd thoughts of driving this on a trip in rural areas, especially at night or Sundays. Read where the factory spare was hard to get. It would be nice if dealers assisted folks who wanted to get the spare and the tire support inserts for customers who wanted to switch out at purchase. Understand why they won't ship them that way.
3.. RFTs have stiff side walls and if flat you can drive on them in an emergency and get to a tire station. They are not self healing and if you drive on flat RFTs you usually ruin them and they need to be replaced. Most tire issues are punctures. RFTs or non-RFTs is best to air up the tire and drive to a tire store and get the tire plugged. A plug is permanent and will last the life of the tire.
7. Recommend to never to use fix-a-flax or any kind of sealant. This is basically a temporary fix that will get you to a tire store. It is not a permanent fix and one you do it you will not be comfortable using the tire until you replace it. It ruins the tire and the tire must be replaced. It is better to air up the tire and drive to a tire store and get the tire plugged. As tires got better over the years and failed less often, the tire sealant was a accountants dream to eliminate the cost of providing a spare tires. Tire sealants are not beneficial to the end customer.
Take Care
YMMV,
MidCow3
P..S. - There are a lot of good threads on this forum if you have some reading time available.
Though I'd like the NX to have a spare tire and have regular tires, I'm fine with the run flats. I'm going to replace them with new run flats when the stock tires wear out
Though I'd like the NX to have a spare tire and have regular tires, I'm fine with the run flats. I'm going to replace them with new run flats when the stock tires wear out
@DenverRx your choice , but really RFTs don't offer that much. RFTs will let you drive up to 50 miles at 50mph, then you have to replace the tire. Many times even driving less miles and lower speed will damage the sidewalls and you will still have to replace the tire.
You can carry an air pump and pump up the tire and drive to a tire center. Most flat tires are caused by puncture which can be permanently fixed via a plug. If you pump up an RFT tire, it can be plugged and reused like a non-RFT tire.
RFTs - with the heavier sidewalls are (1) heavier and get less mpg, (2) less cushioned, harsher ride , (3) are typically nosier and, (4) usually have less tread life.
However RFTs give comfort that you can drive to a tire station without stopping the car or changing a tire yourself. Yes, tires are much more reliable and durable these days and RFTs are much better than the first RFTs ; they are almost normal tires now ( i.e. non-RFT). RFTs give people a lot of comfort and peace of mind and that is great!!
Again vendors switch to RFTs was a pure economic decision, since a spare ( tire and wheel) cost a lot, take up a lot of space, and are rarely used.
I personally am going to change to 20" Michelin Cross Climate 2 non-RFT tires when I finally drive my NX enough to require a tire change.
YMMV,
MidCow3
Last edited by midcow3; 08-28-24 at 08:46 PM.
Reason: correct spelling :)
RFTs - with the heavier sidewalls are (1) heavier and get less mpg, (2) less cushioned, harsher ride , (3) are typically nosier and, (4) usually have less tread life.
I personally am going to change to 20" Michelin Cross Climate 2 non-RFT tires when I finally drive my NX enough to require a tire change.
I hear that CC2s don't get good MPG when compared to the stock RFT. This has me considering Michelin Primacy. They were on my ES300h and provided a comfortable, quiet ride with good MPG. I know they don't do as well in snow but that shouldn't be a problem in Southern CA.
I can verify that I list 2-3 mpg with CrossClimates on my RX. Otherwise, like the tires.
My results were the same with my '22 RX F-Sport.
Although disappointed in the reduction in mileage, which hovered below 20mpg much of the time, I was very pleased with the performance the CCs gave me in all types of weather.
HOWEVER, the reduced mileage, shifting points of the RX's transmission, and overall lumbering performance of the RX is why I now own a 2024 NX 350h, and I absolutely love it!
My daughter replaced the stock run flat tires with Cross Climate 2 when her 2025 NX450h+ was at 1500 miles. She told me the road noise improved just a bit, but the ride quality was like "night and day."
She also told me the mileages were about the same.
For my RX450h, however, mileage with CC2 tires was down about 7% compared to the non-run flat stock tires.
Curiosity The Michelin Cross Climate 2 tires seem like a perfect replacement. However, a loss of 2-3 mpg seems very high. Does anyone have a good reason or explanation for this drop in mpg ?
H'mm investigation are these primarily 18" or 20" tires ?
On 20" tires with less weight 29.19 versus 35 . same diameter 29.3" Basic physics says you should get better mileage with the Michelin.
Curiosity The Michelin Cross Climate 2 tires seem like a perfect replacement. However, a loss of 2-3 mpg seems very high. Does anyone have a good reason or explanation for this drop in mpg ?
I don't know for sure if this is "a good reason." But I think it is because the rubber is stickier. This accounts for the reduction in mileage and the improvement in traction.
OE tires that are on your new vehicle for some very good reasons. One of which is that the manufacturer must determine the gas mileage figures based on regulated test methods. And guess what better mileage provides the manufacturer with? Thanks to CAFE it has to PAY LESS to the government with every car sold. So chances are the OE Bridgestone Bridgestone Alenza A/S 02 tires are providing probably the best rolling resistance of all practical options for tires. For certain Lexus worked with Bridgestone to develop this tire to their specifications with the 'plus' of it being run flats so they could ditch the spare tire also and save more gas as well.
So unless a tire manufacturer has developed a better low rolling resistance tire to date, almost any 'replacement tires' will have a slightly less rolling resistance than the OE tires on that particular vehicle. Yes lower rolling resistance tires are coming, but the Europeans are just now pushing manufacturers to bring low RR tires to their market. North American markets tend to be more focused on tire pricing and other benefits like traction and wear mileage figures. The Michelin Cross Climates came to Europe first, the Cross Climate 2's as well. Now there's a European specific version of the CC2 that we can't get here in North America.
Rolling Resistance in Tires Explained in a 3 Part series of posts on the Tire Rack website:
Off note, it's important to realize what you're comparing to in your recent replacement of 'old tires' to your 'new ones' you just installed.
Quote from part 3 of this series on Tire Rack site that explainsRolling Resistance
" New Tires Generate More Rolling Resistance Than Worn Tires It's been observed that rolling resistance drops by about 20%, as a tread wears from its original molded depth to worn. While this reduction in rolling resistance over time is subtle, a switch from worn tires to a new set increase rolling resistance by a noticeable 20%. The automotive industry estimates a 10% increase in tire rolling resistance equals a 1% to 2% decrease in vehicle fuel efficiency. So, drivers should expect a 2% to 4% decrease in mpg after installing new tires."
Of note, and it may highlight how Lexus and Bridgestone have worked together to increase fuel mileage, when I replaced the Bridgestone tires on my '22 RX with CC2s resulting a 2-4 decrease in fuel mileage, the Bridgestone tires had only 1400 miles on them.
Why did I replace them? Simply because I've been a "Michelin man" since 1970 due to the confidence Michelin tires have always given me when driving in all weather conditions.
08-28-24, 10:13 AM
Naive Questions about Run Flats
NX has mild complaints of stiff ride. Most people like switching to regular tires.
curiosity
Does anyone have a good reason or explanation for this drop in mpg ?
