igotanewis

My IS250 RWD came with 18" summer tires, no choice as I live in California.

I'm planning to switch to 17" tires when these wear out.

Will this soften the way the car rides? I notice on bumpy freeways the ride is very un-Lexus like. I get hit by the headrest on each bump and my daughter is jostled around in her car seat.

For those with 17" tires, what kind of wear have you noticed? Would you recommend the set of tires you have now?

Thanks!

KuyaPatz

not sure about the different tires but as for the suspension, i know if u get the sports suspension ur rides gonna be a lot stiffer and less bouncy and gentle. i got the sports package and you can really feel the bumps as if my car had not springs at all.

C280to250

If you lower the tire pressure to about 30 pounds it would soften the ride alot and its a great ride but the TPS will come on after awhile.

I dont know what the acceptable setting is for the TPS but 35 pounds is way too much on this cars.

DaSweetgrl

A better option would be to keep your 18 inch wheels, but get a set of 45 series tires. The stock tires are 40 series which have less tire height than the 45 series. The 45 series will give you 1/2 inch more tire beneath the wheel. It should soften things up a bit and also protect the wheel. Your wheel diameter will change from 25.1 to to 26 inches. The PCM will need adjusting for the speedometer to correct for the difference in wheel diameter.

Lorna

flipside909

welcome to CL! A less aggressive tire package will definitely help out in the comfort levels. Unfortunately, the IS either in standard suspension form or sport suspension, the ride will be a little more harsher than the average Lexus vehicle. If you do opt for the 17" wheel combination, make sure you go with a Ultra High Performance All-Season Tire in favor of an aggressive low profile summer compound. My two favorites are the Pirelli P-Zero Nero M&S and the Michelin Pilot Sport A/S.

Turkoman

[QUOTE=flipside909] If you do opt for the 17" wheel combination, make sure you go with a Ultra High Performance All-Season Tire in favor of an aggressive low profile summer compound. /QUOTE]

Is that because the ride would be smoother with the M+S compared to max performance summers? I am probably going to stay with 17" but I do want summer performance tires on them and a set of winter tires for the winter. Are you saying that is a bad idea for ride quality?

jasoncd

iTrader: (2)

Is this something the tire installer can do, or does it have to be done by Lexus?

RE: 17's (Potenza RE92), the ride is good, not great. I've not had much experience with tires. I came from a set 15's, and the 17's aren't much worse. When these wear out, I was planning on getting the Pirelli's flipside mentioned if they're still made. I test drove with the 18s as well, but I just seemed to pick up every little bump and it seemed noiser. I think the biggest problem is just the low profile nature of these tires, as it can be rather jarring sometimes.

ff_

I wouldn't suggest that. You're talking about throwing the spedo calibration off, and also changing the acceleration characteristics and suspension geometry. You might even end up with tires that contact the suspension and/or body panels when hitting larger bumps. The smarter choice would be to switch to the proper smaller diameter rims and all-season tires. Then lower the tire pressure to the minimum listed amount for that vehicle and tire size.

igotanewis

Thanks everyone for the ideas. I'll take them to the Lexus mechanic tomorrow!

I love my car. I'm so glad I didn't get a Camry or a Hyundai. Yes, I was very close to buying the Sonata (very good value, not bad looking, so-so crash test ratings).

Bichon

Assuming that the car has a speedometer compensation setting, it would have to be done by Lexus, or at least by a mechanic with a factory scan tool.

I agree with ff_ that you'd be much better off going with the 17" wheels; that will give you a taller sidewall without messing up your suspension geometry and speedo calibration.

DaSweetgrl

Yes I know about the speedo calibration.. thats why I said the dealer or someone who knows how will have to adjust the PCM for the new wheel diameter... I.E a taller tire will have less revolutions at the same speed than a shorter tire. The PCM will need to be told what size tires are on the car.

Suspesion geometry will not change unless the back wheels are taller than the front of vive versa...a non issue. With such a small chance at any point on the circumference of the tire...1/2 inch will not make a difference in turn clearance. A full lock turn should not make the tires rub the inner fender.

Lorna

ff_

Wrong.

http://www.rqriley.com/suspensn.htm
There is all sorts of useful info on suspensions. Just query google.

DaSweetgrl

We are not talking about putting 22's or 26 inch rims on the car. We are talking about 45 series tires vs 40 series keeping everything else the same. I have seen the IS wheels... quite honestly I couldnt believe the wheels are 18" because they look so small because the tire is so short. I think Lexus should have went with a 45 series or even a 50 series tire on a car like the IS 250 or 350.

When you factor in the cost of buying 4 new 17" wheels and 4 new tires( and they wont be cheap if they look like anything) vs. buying just the 45 series tire to fit the stock 18's the right choice becomes even clearer.. its a no brainer.

Another thing to note is that with a 45 series tire, the back wheels will have more traction because there will be more tire "twist" during hard launches . Tire twist increases the contact patch of the rear tires and will improve traction. On a car like the IS 350 you want more traction, and if you can get it with a slightly taller tire...go for it.

There are more positives to going with a 45 series tire than there are negatives. Its just a 1/2 an inch more tire between the rim and the road...and you get to keep your stock wheels

Lorna

gsrthomas

iTrader: (1)

Think you bought the wrong car. Should of gotten the ES350.

ff_

DaSweetgrl, any change in the tire height is going to affect acceleration and handling. Depending on the suspension employed on the particular vehicle, the effects of the taller tire may be more or less noticeable. Truly, in the end you're best off not even recommending that route to people.

And I'm pretty sure that going from a 40 to 45 series tire will probably do very little in helping soften the ride. You'd be much better served by switching to a flimsy all-season tire of the correct size (assuming that you can find any of the correct size for that tire series), or switching to a smaller rim. If that doesn't work, then consider spending a little more time test driving the car next time before buying, and taking the car over some rough roads as part of that test drive.