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Biggest Tire We Can Fit On An Rx400h?


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Hey just wanted to see whats the biggest tire we can shove under our fenders. 255/45/20? I was wondering about a 265/45/20 or possibly a 274/45/20. Any feedback would be greatly appreciated.

-Brett

You realize Lexus put the size best suited for a combo of MPG, comfort and handling, right? Seems if you read threads where changes are made, comments often say the mileage takes a hit. But if looks come first ... good luck. I'd suggest the search tool. We stuck with the standard size, then found a chart listing the tire with the best rolling resistance / longest wear & picked a Michelin. We may sufffer some on handliing, but being a slow poke driver, we don't notice.

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The wheel wells certainly have plenty of room, but the stock tire size looks pretty close to the struts. Don't think you could upsize by much.

there is a guy here running 255/55//18's on his RX400h, he has a 5mm spacer. I took out a measuring tape and it looks like a 255/50 would fit no problem but im curious about a 265/50/19 or so

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I have Toyo Proxes and they are a wee bit bigger and look much better for the wheel well. I have 255/55-18" and if there was a difference in the MPGs, I haven't noticed. I keep really good track of my MPG. Anyway, my '06 400h came with very bad Good Year tires so after only one year I had to replace them. The Toyos are terrific. They are about a 1/2" bigger and it wouldn't seem as if you would notice but you really can. I have side by side pictures, before and after, if you look up my other entries on this forum. The car rides so much better in every way and even though Lexus picked the tire size for this car, it actually looks and feels better with the slightly larger tire. I wouldn't go bigger though...255/55 has not been a problem with anyone in this forum that has this size, no matter the brand. Look up "New Toyo Tires" in this forum, it's my entry and you can see my tires. As I said, my car looks amazing and I also took off that ugly (in my opinion), and for me unecessary, roof rack Rey Bustos, very happy Lexus owner in L.A.

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I have Toyo Proxes and they are a wee bit bigger and look much better for the wheel well. I have 255/55-18" and if there was a difference in the MPGs, I haven't noticed. I keep really good track of my MPG. Anyway, my '06 400h came with very bad Good Year tires so after only one year I had to replace them. The Toyos are terrific. They are about a 1/2" bigger and it wouldn't seem as if you would notice but you really can. I have side by side pictures, before and after, if you look up my other entries on this forum. The car rides so much better in every way and even though Lexus picked the tire size for this car, it actually looks and feels better with the slightly larger tire. I wouldn't go bigger though...255/55 has not been a problem with anyone in this forum that has this size, no matter the brand. Look up "New Toyo Tires" in this forum, it's my entry and you can see my tires. As I said, my car looks amazing and I also took off that ugly (in my opinion), and for me unecessary, roof rack Rey Bustos, very happy Lexus owner in L.A.

Rey, I'm currently in the process of reading through your New Toyo Tires thread on the forum, can you comment on the handling/ride comfort with the new tires compared to the old ones? Did you have to use a spacer to mount the 255/55/18s? Do they Rub at all?

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They feel really nice. No, absolutely no rubbing or any problems whatsoever and NO change in MPGs that I have seen. I was also contemplating the Bridgestone Alenzas that so many seem to be nuts about. I feel that too would be a great tire for you to contemplate as well as the few other choices that people have mentioned in earlier tire posts. I simply loved the look of the Toyo Proxes S/T. they are directional so if you don't mind that, they are wonderful. The car corners much better and they have shown almost no wear in the same time that the Good Years wore away. There wasn't any need at all for spacers even though they are a bit wider as well as taller...but remember that it is only a very little bit of size difference. Some have mentioned that they don't like the aggressive look of the Toyo Proxes but I actually loved that part of it. I didn't mind that my 400h looked like a "girl" before, but now it does look more masculine...well, a little bit more, afterall, it is a lovely and elegant car. I took off the roof rack, as I said, and I added the chrome side step pipes (Nerf Bars) and that along with the new tires makes the car look a little more unique. I also have four "Hybrid" emblems, two on the back and one on each side. In '06 they didn't have anything to show that I had a hybrid except the "h" after the 400 and I felt that I needed to make a statement and wanted people to know that I cared enough to spend the premium for the top of the line hybrid SUV. I hope this helped and remember, make sure that you like the look of the Toyo Proxes S/T tires . I personally think that they ride nicely and feel secure and they do look like a million bucks. In a couple of years or so I might try the Bridgestone Alenzas...but right now, these tires are great! Rey

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They feel really nice. No, absolutely no rubbing or any problems whatsoever and NO change in MPGs that I have seen. I was also contemplating the Bridgestone Alenzas that so many seem to be nuts about. I feel that too would be a great tire for you to contemplate as well as the few other choices that people have mentioned in earlier tire posts. I simply loved the look of the Toyo Proxes S/T. they are directional so if you don't mind that, they are wonderful. The car corners much better and they have shown almost no wear in the same time that the Good Years wore away. There wasn't any need at all for spacers even though they are a bit wider as well as taller...but remember that it is only a very little bit of size difference. Some have mentioned that they don't like the aggressive look of the Toyo Proxes but I actually loved that part of it. I didn't mind that my 400h looked like a "girl" before, but now it does look more masculine...well, a little bit more, afterall, it is a lovely and elegant car. I took off the roof rack, as I said, and I added the chrome side step pipes (Nerf Bars) and that along with the new tires makes the car look a little more unique. I also have four "Hybrid" emblems, two on the back and one on each side. In '06 they didn't have anything to show that I had a hybrid except the "h" after the 400 and I felt that I needed to make a statement and wanted people to know that I cared enough to spend the premium for the top of the line hybrid SUV. I hope this helped and remember, make sure that you like the look of the Toyo Proxes S/T tires . I personally think that they ride nicely and feel secure and they do look like a million bucks. In a couple of years or so I might try the Bridgestone Alenzas...but right now, these tires are great! Rey

Thanks for the detailed writeup, I'm still undecided as to which tire i'm going to stick with, Maybe a 265/50/19 or maybe a 255/50/19. I'm mainly looking to firm up the suspension, have a firmer grip on the road, a wider stance, etc. I've been comparing alot of the features from tirerack, Tire Width, revolution per mile, etc, I love the directional treads, and you can't go wrong with the Toyo's especially at the cheap price you paid for them. If your 255/55/18's fit no problem, no rubbing, etc I might just go with something similar in size, thanks for all the help and i'll let you guys know what i'm doing as soon as I finish comparing all my options

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Rey- thanks for the photos. Those tires look awesome on the RX.

Does anyone have similar pictures with 255/50 18's? I like how the 255/55's fill the fender well, but the 255/50 is the closer match to the original 235/55's diameter-wise so there would be no impact to speedo readings. Here's a good calculator to play with:

http://www.1010tires.com/TireSizeCalculato...p?action=submit

The 255/50's are 0.5% larger than stock, while the 255/55's are 3% larger. Not a huge difference from a speedo reading standpoint, but the calculator brings up the following warning which is a little disconcerting

"Warning! When changing tire sizes, we recommend staying within 3% of the diameter of the original tire. Any more than this and you face the risk of brake failure."

Now, that's not a fun prospect. I can see how increased rotating mass could overwhelm brakes that were not designed for that load. Rey- have you experienced any decrease in braking performance from the larger tires?

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3% is exactly the difference and factor that in when calculating my MPG. No, I have not noticed any difference in regards to braking. The ride is so much better that all that I do notice is how much happier I am with these tires and how much better they feel. Keep all the info coming, it's great to have all of you to learn from! Rey

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