MustangSal

I don’t think anyone really knows the difference. Anyone on here tested all those tires themselves? On a controlled surface. In the same environments? Doubt it.

Unless you’re tracking the car or have some requirement for mileage guarantee (I wanted 45k warranty) ... Go with what you’re money speaks to you logically and just enjoy it. In a few different vehicles over the decades I’ve never done a tire change and been disappointed.

Goodyear F1s Assemmetrics on mine with a couple thousands miles since replacing. Super happy. Couldn’t tell you if there is much of a predominance or ride difference because (to me) the potenzas performed fine, drove smooth, sounded fine. Just lasted 25k was my only complaint.

ix3ph09

Thank you for the input everyone! After much research, online shopping and comparisons, I will go with the P7s since I am looking more for comfort and quietness in the ride than sportiness. I have ordered the tires from Discount Tires (America's Tire on west coast) and will have them installed this coming Saturday. I was also considering going with the wider tires at 145/45r/18, but since there is not much of a difference, will stick with the stock sizing. Thank you once again!

bclexus

I don't know what you paid for your Pirelli tires, but I couldn't believe how much the price dropped for the Pirelli Cinturato P7 A/S Plus tires here in Dallas. My Pirelli 245/45R18s were only $162.00 each, where they were ~$190 or so a few months ago. I paid $233.00 each for my Michelin Premier tires in the same size that I just replaced. The Pirelli P7 tires are 44% less than the Michelin Premier tires - Wow!

peteharvey

Good choice to stick to the OEM size of 235/45R18 94W.

Upsizing to 245/45R18 will slightly slower your acceleration, and slightly increase your unsprung mass for a knobbier ride, plus give you more positive steering scrub radius: http://www.clubprotege.com/forum/sho...n-Scrub-Radius

1. Quote:

   A positive scrub radius will increase steering effort, torque steer and kickback on bumps to a considerable degree. At the same time, a blowout or a failure of one front brake could yank the wheel hard enough to pull it out of your hands. The advantage is that there is much greater road feel and feedback so that you can feel when the front tires start to break loose in a corner. Consequently, this is often the set-up of choice on race cars.

On the upside, the bigger 245/45R18 size will slightly improve your fuel economy, plus slightly improve the handling.

bb700092

Why will it improve fuel economy? The larger tire should weigh more, so it should decrease fuel economy, isn't it?

peteharvey

The larger the rolling circumference of the tire, the taller the vehicle's actual gearing, hence slower acceleration but superior economy [depending on torque available etc].

Theoretically, the taller gearing would increase the top speed too, however in practise, the top speed will also depend on the torque and wind resistance.

The heavier unsprung weight of the wheel/tire combo will also reduce the acceleration too.
In the article below, notice how upsizing the wheels while reducing the profile increases the weight of the wheel/tire combo reducing the acceleration from 7.6 to 7.9 seconds.
Here, they have actually widened the wheels too, hence the considerable weight increase of the wheel/tire combo from 40 to 54 lbs.
Imagine you had to spin a heavy metal disc with your bare hands; the heavier the disc, the harder it is to spin, hence the fall in acceleration.
Many enthusiasts use big and wide wheels, not realizing the effects on the vehicle's acceleration & braking.

When upsizing from 235/45R18 to 245/45R18, I didn't talk about the effect of extra unsprung weight on acceleration/deceleration, because it'd be so little.

bclexus

I think you are making far more out of upsizing than is really warranted. The wheel size has not changed. The diameter change is minuscule. The weight difference is not a factor - it's a heavy, luxury 4-door sedan for crying out loud! If I wanted to improve acceleration a tad bit I'd remove the 100+ pounds of golf stuff from the trunk...

peteharvey

I don't think I made it out to be far more than really warranted.
That's why I said I didn't bother talking about 245/45R18's extra unsprung weight effects on acceleration/deceleration - because it would be so little...

bclexus

Well, you gave the distinct impression (in the first quote above) that upsizing +1 should not be considered. I disagree...

peteharvey

[QUOTE=bclexus;10019240]What I said is true.
There are small differences in tire specifications, and that why manufacturers go to all the effort to make tires in these different sizes and specs, despite the fact that some drivers can't tell the difference.
If there was truly no genuine differences at all between the different sizes and specs, manufacturers wouldn't bother to make various models.
The differences are there, it just boils down to whether the buyer is the type that can perceive the differences or not.

235/45R18 vs 245/45R18 - the differences will lie mainly in the slight differences ride and acceleration, versus handling and economy - if one is sensitive enough to perceive the differences.
Another major effect is that the 245/45R18 will often come in higher load and speed ratings, which improve the handling, at a cost to the ride comfort.

However, in terms of bb700092's question about the effect of additional weight on the fuel economy - there will be very little difference...

peteharvey

If you read properly the part I bolded for you in black, you will notice that there are advantages to using 245/45R18.

235/45R18 is commonly available in many load/speed ratings, for example 94W versus 98Y.
Often people think that 94W and 98Y handle/ride "exactly" the same.
If this was really true, manufacturers would discontinue producing the 94W version.
The reason why both 94W and 98Y moieties are manufactured, is because there is a difference to the handling/ride.
The 98Y can certainly handle more weight and more speed, but with a stiffer carcass, better at handling, though a detriment to the ride.

bclexus

Pete - You're talking about minor differences in tires that will be used on a heavy, luxury 4-door sedan. Only someone that cares to scrutinize things they likely cannot really discern differences in would be interested in such things. Tires are usually chosen by owners of a GS 350 based on looks, quietness/comfort, tire wear or the 'perceived' view of performance, the latter of which will never be tested on a 10/10 level to prove anything meaningful...as most owners' time is spent in stop-n-go rush hour traffic or running errands on city streets or highways alongside your typical Toyota Camry or Honda CV-R. In other words, the tires are not near as important as some make them out to be. Acceleration - nope...I'll never know the difference! Traction - nope...I'll never know the difference! A stiffer carcass of a 100V versus a 94W or 98Y in the same brand and type - nope...I doubt I'll feel the difference. Increased or decreased fuel mileage between two tire sizes - nope...one or two extra red lights waiting on traffic destroys that analysis!

peteharvey

https://www.clublexus.com/forums/gs-...l#post10017019

I've clearly said that if the differences were that small, the manufacturers wouldn't bother making small model variations - yet they do.
I can tell my Cinturato P7 A/S Plus doesn't grip as well as my old OEM SP Sport Maxx 050's.
I've told you before that I can tell the difference between the 98Y I had for several days versus the 94W I have now; big difference to me in the ride comfort.
There will be some people like yourself bc who will be less sensitive than others, and you can't tell the difference, but others can.

I've said that it depends on the individual sensitivity of the person involved; some people are more sensitive to small changes than others.
How sensitive some one is, I leave it to the individual person.
Let's not worry about forcing other members to feel the difference, or not feel the difference - let them decide.
For very fine parameters like acceleration and fuel economy, we obviously need a stop watch and/or telemetry, and an arithmetic calculator to tell the difference.

For example, the first poster on Page 2 above could not tell the difference between the OEM Bridgestone Potenza RE050A's; he said
"the potenzas performed fine, drove smooth, sounded fine. Just lasted 25k was my only complaint".
Me? I can tell a big difference, especially in the smoothness and quietness of the Potenzas.
There will be some people like yourself bc who will be less sensitive than others, and you can't tell the difference, but others can.
Each to their own.

https://www.clublexus.com/forums/gs-...l#post10017526


It kind of reminds me of this thread in the 6ES section where the OP was adamant that there was steering wheel vibration at idle, but another poster lesz kept saying that he could not feel any steering wheel vibrations at idle in his ES...

https://www.clublexus.com/forums/es-...at-idle-3.html


.

bclexus

Pete - Maybe you have more nerve endings in the cheeks of your *** and can feel the difference between a 98Y and a 94W in the same model tire while driving on a wide range of roads and highways. Even though you are a self-proclaimed extraordinaire in sensitivity, I'm not at all convinced you can tell the difference! It would be interesting to set up a controlled test and have people (such as you who claim they can) bet their own money on whether they could tell the minor difference. Betting $10 grand - were you driving on 98Y or 94W tires? Uh, well...ah. BZZZzzz - you lose...

Can you detect the difference in 1 psi of tire pressure? How 'bout 2 psi? Maybe 3 psi? Or 4 psi? But, I'm sure Pete, there's no doubt with your sensitivity that you can [also] feel the difference between using 93 octane versus 91 octane gasoline too, right? C'mon man!

peteharvey

BC buddy.
I'm glad you realize that this post of yours is not correct, because there are both pros and cons to each design and parameter.
https://www.clublexus.com/forums/gs-...l#post10019240
https://www.clublexus.com/forums/gs-...l#post10019247

Now, you change the topic to "how much difference", or "very little difference".

To address your change in topic, I can tell the difference in handling between my OEM Dunlop SP Sport Maxx 050 versus my Pirelli Cinturato P7 A/S Plus.
The Sport Maxx 050 definitely has sharper turn-in & higher limits of adhesion, where the P7's are softer and slide more.
However, the P7's are also much softer riding and much quieter esp above 50 mph.
Obviously, there will be those who can't tell the difference.

I have accidentally owned a Cinturato P7 A/S Plus in 235/45R18 in 98Y for 5 days, and owned the same tire in 94W for over a year, and I can tell you the 94W rides much better.
I can't tell the difference in noise though.
Handling? I actually only drove the 98Y very gently because they were being returned, so I don't want to flat spot them by dumping them around my favorite corner.
Now once again, obviously there may be people like yourself bc buddy who can't tell the difference between the two.

Excellent that you brought up the tire pressure difference.
In fact, instead of using the OEM recommended 33 PSI [230 kPa], I use 32 PSI [220 kPa]!
For me, the 4GS coils are a bit too firm, and the base/luxury model uses exactly the same coil springs, and part number as the F Sport.
Thus, I dropped the tire pressures all round.
Noise is the same.
However, the lower PSI has a softer ride.
31 PSI is even better again, however the outsides of my tires start to wear out more than the middle.
Of course handling is diminished at lower PSI.
Also, using the trip computer or manual calculations via speedo/GPS, gas station dockets & a simple arithmetic calculator, I notice that my mileage has decreased from 22.40 to only 21.38 MPG with a drop in tire pressure.

Btw, I can't tell the difference in octane rating; higher octane rating prevents uncontrolled spontaneous combustion at high compression ratios called "pinging".
However, I can tell the difference between normal gasoline versus those gasolines containing a high content of ethanol; I found hi ethanol gasoline noticeably loses power.

These are just simple observations that any person can do.
Thus, with your change in topic, there will be people who notice the difference, and there will be some people who can't tell the difference, and there will be some people who make an a**** of it all...

.