knip21

I am going to get new tires for my Sportcross. I currently have the L-tuned wheel and tire package (OZ Salinas w/ Michellin Pilot Sport (235/40/18 front and 265/35 18 rear).

The L-tuned wheel/tire pkg was designed for the GS but fits the Sportcross just fine (a little wide in the rear). I have occassional rubbing in the rear when I hit bumps w/o slowing down -- this is also due to the soft stock suspension (which I will stiffen with Eibachs later).

Anyway I am looking to go with 225/40 in the front (18x8) and 255/40 in the rear (18x9.5). I am not too worried about the fronts. The rear tires are my question. In theory I am going taller and narrower which is what I want... am I insane or am I going to be OK?

If I've been driving on 265/35s with little to no problems, then I am thinking I wouldn't have any problems with 255/40s.

As far as road use is concerned, the Sportcross is our around town and short trips to LA car. BTW I am going with the Conti All-Season Performance tires -- they're about the only ones that have 255/40 18s.

My other option is to go with 245/40 at the rear. In other words, I am looking at 40 series tires in the back (265 and 275 are the other sizes... way too big without modifications).

What do you guys think... any tire experts out there... HELP!!!

mmarshall

Going with different size front and rear tires (225/40 and 255/40) is not a good idea. The chassis was designed for the same sizes front and rear, and has good front-to-rear weight balance for handling. Different-size tires front and rear could screw it up....not to mention maybe confusing the ABS and Traction computers, which compare front-rear wheel rotation speeds.
265/35's, which you mention you had before, are extremely stiff-riding, and give almost no impact and pothole protection. You must have pretty much stayed on glass-smooth roads.
What is wrong with the stock wheel/tire package? If my memory is right, for the SportCross, and most IS300's, that is a high-performance 45-series with plenty of cornering ability and a ride that is somewhat stiff but tolerable. Don't expect much more than about 20,000 miles out of them, but that is the case with almost any Hi-Perf tire, including the ones you mention. The Lexus engineers designed the chassis specifically for the factory tires used.

GGP4me

Wouldn't a 255/35 -18 (rear) match up better with the 225/40-18 front?

225/40-18= 25.1"
255/35 -18= 25.0"

255/40 -18= 26.0"



The 255 would probably give you more side rim protection as well.

255mm -25.4*9.5 = 13.7mm/2 =6.8 mm

245mm-25.4*9.5 = 3.7mm/2 = 1.8 mm

With the correct rear offset(~+55) the 255 should not rub with moderate drop.

rominl

iTrader: (4)

ggp is right, if you are going to 225/40 in the front, you should do 255/35 in the back just to match the front. i am not sure how much the speed would be off though, won't be much i'd say

marshall, the stock wheels and tires basically sux. the performance tires i am using now have pretty much the same tread wear but it grips a lot better. that's why people go with aftermarket wheels -- wider and better. stock is good, but no match.

and over the spec? so what? my gs4 has 20s and it's 6% out of spec and i am running it every day no problem. i drive pretty crazy at times and the abs and trac has no problem handling the task

knip21

Thanx for all the advice and input.

I would really like to go with a 40 series tire in the rear because it is meatier and takes on the potholes and bumps much better. What tire sizes are advisable for front rear?

What would match with 255/40? Will 235/40 front match 255/40 rear?

Thanx for enlightening my ignorance.

flipside909

You're right. Which is why i'm now in the market for new tires. Either gonna replace the tires and go with 225/45R17 or going with a larger wheel/tire combo.

Neo

iTrader: (3)

Just to make sure, you want the look of more sidewall in the rear than the front? I don't know. It would look a little strange to me.

GGP4me

The rubber between the rim and the road is basically 3.5" whether you go 225/40 or 255/35.

Going 255/40 in the rear raises the rear up ~ 1/4 "and dramatically throws off the speedometer/odometer:

255/40-18 (speedometer=60) actually traveling 62.5mph

There is basically about 0.3inch radius difference between 235/40 and 255/40 (or .6 " tire/wheel diameter diff between front and rear)

Brandon@TR

225/40 and 255/35 are perfect for the car. These tires have the correct overall diameter (25 inch).

knip21

Thanx Brandon. I'm actually going to order from TireRack so I'll give you a call when I'm ready (by end of this month or start of next month).

Next question. What's the best tire for me with ride comfort, tread durability and economy in mind?

rominl

iTrader: (4)

umm..... get 4 season tires.... what you are looking for is just opposite of what a performance tires bring you...

Brandon@TR

The best choice in the correct size for the vehicle is the Pirelli P Zero Nero M&S.

P255/35R18 PI P-ZERO NERO MS S 162.00
P225/40R18 PI P-ZERO NERO MS S 126.00

mmarshall

Well...good luck, Flip, with the new tires/wheels....hope it turns out well for you. I just remember from many of your earlier posts your telling people in most instances to get the stock 17's, not the all-season 16"s. But....... I can see where you're coming from, if even the stock hi-perf's don't give you the handling you want.
Michelin Pilots are good aftermarket rubber...they have an excellent reputation...as does Michelin in general.

knip21

Those are the tires I was looking to purchase. That makes me feel real good about going with those tires. I'll give you a call in a couple of weeks. Thanks Brandon and everyone else that's put in their two cents.

knip21

Ordered my Pirelli's from TireRack and will get them installed tomorrow. Brandon, I tried your extension a few times but I got your voicemail. I ordered from some guy named Kieth.