Darookie27

I'm new to CL, (recently picking up a new\used IS250 Awd) and am struggling with this also.....cause I hate the stock wheels.

I've seen "keep it the same rolling Diameter" and, "As long as it's close to the same." So which is it? As for keeping it close to stock diameter....I wouldn't think that would matter.

IS 250 AWD comes with 225/45/17's 17X8 rims, so the Rolling Diameter would be Exactly 25".

I'm considering staggered 18's with 18x8 front and 18x9.5 in the rears.
Tire options would be: (from the BFG T/A G-force KDW chart)
Front: 235/40/18 - Dia 25.402
Rear: 265/35/18 - Dia 25.303

Your opinions please, Do you think this is close enough?

Koz

There are two reasons why AWDs use non-staggered wheels and tires. The most important reason is to insure the overall diameter of all 4 wheels/tires are the same and to be able to rotate the tires. Since AWD is harder on tires. The reason for staggered is to be able to put larger tires on the rear where they can not be used on the front, for max performance.

It doesn't make any sense to put larger rims on the rear with the same size tires as the front!

Koz

Darookie27

Yep, I absolutly agree.

I really don't care about being able to rotate the tires. For as long as they are going to last, rotating really doesn't give you that much more, if the car is properly aligned. The only reason to do this is Looks. I really don't think it going to effect performance to noticeable degree, It's an IS250 AWD.

(your reply is slightly confusing, I'm thinking you a meaning to say Wider not larger) I am going larger also to 18's, Staggerd is width only....

Which put us back to the original question: Do the diameters have to be Exactly the same? or is there some acceptable tolerence? (to preserve the AWD system)

19psi

having owned many performance awd vehicles and being an avid tire/wheel ****, i'll say this: just make sure your OD is the same between front and rear.
www.1010tires.com has a tire diameter calculator to use for this specific purpose. plug in the sizes and look at the od. edit: their site is down atm.
look here:http://www.rojawheels.com/wheeltech/...Calculator.htm

awd porsches use staggered wheels and they don't have any problems.
there is an acceptable tolerance ; for example, porsche uses 225 40 18 fr. and 265 35 18 rear. that's a 0.22" difference.

Joeb427

iTrader: (1)

A wider tire in back has more of a footprint and rolling resistance.I don't know if that means anything on extra stress for the Lexus AWD system.
I moved up to 18s and stayed 18.8 all around.Other than maybe looks,I can't see any benefits of a staggered set on a 250AWD.

Darookie27

Thanks guys, that's more of the answer I was looking for.
As you can see in my original post, I did the homework on diameters,
(for both 18's and 19's actually) and with the proper staggerd set I can get within .1" (one tenth of an inch) in diameter in either size.

I'm thinking this should be just fine.

And Yes it's ALL about the looks. I just didn't want to mess up the AWD system. I have Staggered on My BMW M Roadster, and it just looks sooooo cool....I get many compliments (and the're are OEM)

almacruel

The staggerd wheels I have on my awd are the exact same OD
Front: 19x8.5 235/35/19
Rear: 19x10 275/30/19

rdgdawg

With all due respect, if it's AWD (ALL WHEEL DRIVE), WHY would larger rears make a difference again? If just for looks why risk AWD permanent damage? I'm NOT into risking damage to my car.

I'm a little confused.... but wish the best to anyone who makes the change... personally I''ll get bigger wheels eventually but they will ALL be the same four wheels...

passnu2

iTrader: (33)

There is a tolerance that is allowed. I would call Discount Tire or Tire Rack and see how much variance you can have. You just need to make sure the Diameter is within spec. Having a wider tire will give you better performance/handling and will not hurt your AWD. You will not be able to rotate the fronts and rears like us 350. You will find a set that will work it this one doesnt. I cant imagine that the .1 difference is that big of a deal. They have to build them and allow for some safety/variance.

Joeb427

iTrader: (1)

I just wonder why the Lexus engineers didn't call for staggered on the AWD.
I don't buy the cost issue someone brought up in the past.
I mean how much extra would two half inch wider rims and a two wider tires cost Lexus? $100?Probably much less.
The AWD has a sticker of $35+K.Adding that $100 to the sticker price wouldn't even be noticed.
There has got to be another reason or reasons.
Maybe the AWD traction in snow or wet roads may be a problem with staggered.
I don't know but it's definitely something.

rdgdawg

+1 on all points....

Koz

Depending on the center diff (locking 50/50 split or variable split) damage to the diff could accure if the tires are not spinning at the same speed. To be sure you could check with the diff manufacture, Torsen. Why take the chance of damage?

Koz

passnu2

iTrader: (33)

right but if the diameter is the same then they are doing just that. on any AWD car that is the most important issue. If you have 18x5 front and 19x10 rear that doesn't matter. I think that is what the OP is asking about. On the IS350 staggered set up i don't think they are a perfect match for diameter unless i am wrong. When i have a Eclipse GSX (AWD) i had so much power in that car and was running wider tires in the back then the front. I beat the **** out of this car and never once had any issues. I did lots of research and it all boiled down to over all diameter. That car,cant recall what, did have a tolerance for slight variation. I would also think that if you get a flat that running the spare isnt the same diameter as your OEM tire/rim. I know this can be done on any car. You just need to do your home work before pulling the trigger. All of the concerns are great and don't blame any one for them. I had the same concerns when i did this back in 97/98 on my eclipse. Call Lexus service department or Discount Tire and ask them for some input

Koz

Each tire will carry a different load and be faced with different situations causing them to wear out at different rates.. The front tires will carry more weight then the rears. They are also responsible for about 80 percent of the braking and do the steering. Not only that, but the right front tire might tend to wear out more quickly than the left front because the nature of American traffic means that left-hand turns (which load the right-front tire) tend to be taken at higher speeds, and under higher loads, than right-hand turns (which load the left-front tire). It stands to reason, then, that the front tires will wear more quickly than the rears.

It still may not be worth rotating! Depending on how much it cost to rotate the tires which may not equal the savings on the longer life of the tire.

Koz

Koz

I agree, thats why I said "if the tires are not spinning at the same speed". Has nothing to do with the rims. For that matter, you could have 18s on the front and 20s on the rear.

Koz