Alt Size 225/45/18 on 18x8

[Rex]

I've picked up a set of 350Z Track wheels and the fronts are the 225/45/18 RE040's, but the load rating is only 91, and my 1994 Infiniti Q45 needs more . I was hoping to find something ~96.

The wheel is 18x8 with an offset of 30. I'm currently at stock height and am experiencing no rubbing.

Have I provided enough info? Any suggestions?

[AZhitman]

255/40/18

Easy choice.

[Rex]

255/40/18

Easy choice.

LOL, I'm only looking to replace the fronts, as the rears (245/45/18 on 18x8.5 33 offset) have a 96 load rating. I was hoping to buy just 2 tires.

Would a 235/4018 Toyo Proxy work? If so, anyone know of a fair price for said tire?

[maxnix]

255/40/18

Easy choice.

Ditto. Sometimes the world is the way it is, not as we wish it were.

[Rex]

FWIW, I do not think a 255 will fit with the current front wheel set up (18x8, 30 offset) and NOT rub the fender. IIRC, Wes has 265's on his rear (18x8.5, 33 offset) and it rubs on full down travel.

BTW, Wes has the same wheels.

Here's 2 pics of the front clearance with the 225'shttp://q45.spilky.com/Q/newcar%20005.jpghttp://q45.spilky.com/Q/newcar%20010.jpg

[chmercer]

if it was me i would leave it.

91=1356 pounds, i highly doubt your car would ever experience 5424 pounds of downward force? unless you have like 5 fat friends and you put a bunch of wings all over it and go for a top speed run.

[elwesso]

I kind of agree... I think the load rating wont be a big deal...

Either way, the 245-45-18 would be a good choice for the front, IMHO

[AZhitman]

91=1356 pounds, i highly doubt your car would ever experience 5424 pounds of downward force? unless you have like 5 fat friends and you put a bunch of wings all over it and go for a top speed run.

Not even *close* to how load rating works.

Put some 91's on a Q and do a high-speed blast through AZ on I-10 in August and you'll find out the hard way what load rating numbers mean.

[Rex]

Ditto. Sometimes the world is the way it is, not as we wish it were.

And as much as I might "wish" them to, the 255/40's won't fit under the front fenders on the forged wheels I'm using .

I do "wish" I knew of a 225/45/18 with a load rating of 95 or higher. I've learned that Nitto's do, as well as Toyo Proxes do in a 235/40/18 . Any others?

[hannibal]

Yokohama ES100, Falken Azenis ST-115, Kumho ECSTA SPT, Kumho ECSTA ASX, Kumho ECSTA Supra all have 95 load ratings in 235/40-18.

[chmercer]

Not even *close* to how load rating works.

Put some 91's on a Q and do a high-speed blast through AZ on I-10 in August and you'll find out the hard way what load rating numbers mean.

hmm well the load rating seems sufficient to me for the car, i mean if you are going corner carving in a big sedan you probably shoud switch platforms...

imho

[elwesso]

hmm well the load rating seems sufficient to me for the car, i mean if you are going corner carving in a big sedan you probably shoud switch platforms...

imho

own one and youll understand

[chmercer]

uhh sure...

[obnoticus]

lol...

[Rex]

hmm well the load rating seems sufficient to me for the car, i mean if you are going corner carving in a big sedan you probably shoud switch platforms...

imho

I appreciate your perspective, that's why I posted this in the Wheel/Tire specific forum.

The Q has a "required" load rating of 95, and I think it's fair to say running any tire with a lower load rating than the manufacturer recommends is a bad idea. Maybe not for the first 3k miles, but probably for the last 3k miles . And as AZ mentioned above the conditions can greatly impact if you're pushing the tire too hard, even without heavy braking/conering.

What I am interested in learning is - if the load rating is based on Max PSI, what is the actual load rating on tires run in the mid-30's versus the max of ~45.

I'm looking at some different options now, 1 may be to get slightly wider rear tires and move the current ones to the front, assuming they wouldn't rub. I AM concerned about fender rub with a 245/45/18 up front on the 18x8 - 30 wheel.

[Exar-Kun]

Rex, you may want to get the *gasp* continental sport contacts in a 235-45-18..their reinforced with a load index of 98, and will fit nicely on a 18x8 wheel.

-Chet

[chmercer]

^^^ uhh its up to rex on what he wants to do with his tires, so just let me make clear that i have no beef with him and i just suggested that the 92 index tire would probably be fine for regular driving. but that paragraph you just posted made absolutley no sense. by that logic i could get the same grip out of a hummer as long as i got like a 10 ply sidewall tire.

please explain "how friction works"

[Nismo_Freak]

The size of the car really means very little as far as handling goes. As long as your tires have an adequate load rating, it doesn't really matter how heavy the car is, since increased weight will translate to increased traction and will basically offset itself, due to how friction works. Sure, really low weight does help some, but where weight is really a winner in "handling" is braking distance.

That being said, load rating needs to be higher than you'd figure for the tire due to weight transfer. You have to expect to probably get about 70-80% of the weight of the car on the outside wheels during hard cornering with a soft suspension.

What the hell lol...

[Exar-Kun]

I've removed that for..uhm..obvious reasons....

-Chet

[Rex]

Rex, you may want to get the *gasp* continental sport contacts in a 235-45-18..their reinforced with a load index of 98, and will fit nicely on a 18x8 wheel.

-Chet

Any opinion/info on Toyo Proxes? The seem to have a few options and meet the laod rating.

Also does anyone have any information about true load ratings given no one really runs the max pressures that the laod rates are based on?

[Exar-Kun]

a load index translates into a carrying capacity at a given air pressure, IIRC it's base is 32psi cold. THere's a chart showing the load carrying capacities for given load index tires...I've got the book at my desk at work.

Just keep a load index at or better than the OE...trust me.

-Chet

[AZhitman]

hmm well the load rating seems sufficient to me for the car, i mean if you are going corner carving in a big sedan you probably shoud switch platforms...imho

I appreciate that, but "seems sufficient to me" is a woefully inadequate and flawed measure.

If you are able to ascertain the amount of force on the RF tire of a Q45 at the apex of a 35-mph emergency swerve/ threshold brake, then you can dispute the tire engineers and their rating system.

Until then, it's best to stay at or above the recommended rating.

Think aout it: One tire failure = a MINIMUM of $70 to replace the tire.

That's assuming you don't damage the rim, you don't have to be towed, you don't miss any time off work, you don't damage the car (with a destroyed tire), you don't experience said failure at high speed and total the car, your tire failure doesn't cause an accident, you don't get sued by a crafty attorney who knows load ratings and can trace the cause of the accident back to your neglect....

I'd rather spend an extra $30-$40 and get the good stuff. Pretty simple economics.

[szh]

LOL, I'm only looking to replace the fronts, as the rears (245/45/18 on 18x8.5 33 offset) have a 96 load rating. I was hoping to buy just 2 tires.

If you temporarily swap the rear wheel and tire to the front and check it out, that is an easy test, right?

I think the 245/45-18 will work, even on a 30mm offset tire, and there are plenty of good 245/45-18 tires with high load indexes. It will stick out under the fender a tiny bit (that is what I experienced with my 245/45-17's with a 30 or 33mm offset - I forget which), and should not rub except on very hard bumps, I would think!

Another, albeit expensive, possibility is the Bridgestone Potenza ER33 at 235/45-18 ... has a load index of 94. A bit lower than desirable, but may work out. This tire comes stock on the 2003/4 M45 ... which is a similar weight car. This tire is probably a bit stronger than most tires in its class, and if you run it at 36 to 40psi, you will get the load rating up enough to count.

Z

[szh]

I'd rather spend an extra $30-$40 and get the good stuff. Pretty simple economics.

Yes!

And, also helps between being around to understand the difference. I have no desire to lose a tire explosively at high speeds. Did that once and it is not fun. If it had been on a curve, I would be dead for sure.

Z

[Rex]

At this point, I've narroed it down to 2 options

1) Get some 225/45/18 Nittos, they meet the laod rating and match current front tire size.

or

2) Get some 255/45/18's (preferably Bridgestone RE040's) for the rear and move the current 245/45's to the front. If I do this, I hope to find the tire pressure sensors so I can ebay them along with the 225/45/18 RE040's .

THOUGH, I'm looking really hard at some 245/45/18 Yokohoma AVS ES100 all around.