Will P235/50/ZR18 tires fit my 2003 M45

[Tim/M45]

I need to shop for tires. Local guy has a set of P Zero Nero P235/50ZR/18 with good tread for little $.
My car has 235/45/18 now as is specified by the manufacturer. Will the 235/50/ZR18 tire be too big?

[EdBwoy]

I used an online calculator to get these results: http://www.1010tires.com/Tools/Tire-Siz ... /235-50R18

It says that the diameter variance between the 2 sets is more than their recommended 3%. Physically, the tires will fit, but I can't recall exactly at what point the M45 will throw a SLIP/VDC light.
However, I looked into it when I ran 235/50/18 winter tires in the rear and the factory 235/45/18 in front with no ill effects.
I assume if you ran a square set of the 235/50 series you'll be fine.

[Larz]

Just curious why you want to go with a smaller tread than stock? I would can see increasing tread width but I'm wondering why you would want less tread width?

[BlackCat81]

Just curious why you want to go with a smaller tread than stock? I would can see increasing tread width but I'm wondering why you would want less tread width?

There's nothing smaller about those tires.

[szh]

Just curious why you want to go with a smaller tread than stock? I would can see increasing tread width but I'm wondering why you would want less tread width?

Actually, the width of a 235/50/18 tire is the same as stock 235/45/18 ... just a bit taller ...

So, It should fit fine on the stock 18" wheels. And, if you have it on all four wheels, the VDC should be fine too, although the speedo will be nominally off (your speed error will probably be about 1.5 to 2 mph).

FWIW, I use 245/45/18 on my car on the stock 18" wheels - this is slightly wider than stock, and has an actual speed a bit off than shown. I have verified the error with my Garmin GPS unit and the error is about 1 mph in my case.

And, 245/45/18 is the widest you should do on a 7.5" wide wheel (stock wheels are 7.5") in a 45 aspect ratio - any wider a tire will lift the inside and out edges of the tread a tiny bit at normal pressures, negating the effects of using the wider tire since the contact patch will actually be smaller. The 235/50/18 will fit on a 6.5" to 8.5" wheel though, since it has more tire height to play with without changing the tire aspect ratio.

Z

[EdBwoy]

I think the reason Tim wants to run a non-stock size is mainly fiscal. He mentioned that the price was right.

Also, I have driven many different cars with many different combinatiuons of tires and wheels and very few times have I seen the speedo accurate to a GPS unit. As long as I keep the OD fairly close I'm not too worried.
Consider the subtle changes that happen to a tire as it wears with age, as it gets squished with vehicle and passenger weight, as pressure increases with temperature etc.

Good point above about being sensible with wide tires.

[Tim/M45]

Thanks all,
I'll go check them out today.

[Tim/M45]

Update: False advertising. The tires were about as worn down as the ones on my car, so I passed.
There is a set of 245/45/18 Hankook tires I will look at this week.

[szh]

Check out Tire Rack for excellent prices on brand-new tires ... they are a NICO sponsor too.

Z

P.S. Never get used tires that are more than 3 (maybe 4) years old, or new ones more than 1 to 1.5 year old. The rubber starts hardening almost right after manufacturing. Tires that are 6 years old, even with perfect full 10/32" tread, would still be dangerous - prone to cracking easily!

[Larz]

Good point! There is a "born on" date on the sidewwall. It's easy to tell how old the tire is.
.

.
The tire above was born in the 26th week of 2013

[Larz]

Update: False advertising. The tires were about as worn down as the ones on my car, so I passed.
There is a set of 245/45/18 Hankook tires I will look at this week.

I second Tire Rack. They have actual video comparisons of tire types done on their track. I always used Michelins until I tried Hankook. My last set of Michelin Pilot Super Sports began to show cupping on the outer edges if the tread. My tire guy told me that the heat and direct sun in South FL causes some brands to deteriorate prematurely and Michelins are supposedly known for this. He recommended I try Hankooks.
Mind you, they are NOT 100% identical in every way, but they come so close that I couldn't justify spending the extra money to stay with Michelin. I bought a set of Hankook Ventus S1Noble2 and I have driven them for 2 years. No significant tread wear and they are very quiet for Ultra High Performance tires. They grip like a cat on a carpet pole and the stop in the rain on a dime. The only thing I can't attest to is whether they will ride like this near the end of their life because they are still near new after two years and about 12,000 miles. No cupping, no sidewall problems. Michelins ALWAYS ride like new even at the end of the treadlife. I'm waiting to see if these Hankooks do that, but so far they have not disappointed me or made me regret not staying with Michelins.
My tires: Hankook Ventus S1Noble2 255/40/19
Here is a video about them:
https://youtu.be/6OGsfUZj0GU
If you are looking at USED tires, here is an easy way to tell how much tread is left:
http://www.tirerack.com/winter/tech/tec ... ?techid=51

[szh]

Good point! There is a "born on" date on the sidewwall. It's easy to tell how old the tire is.
.

.
The tire above was born in the 26th week of 2013

Indeed, yes! Thanks for that image.

Z

[szh]

If you are looking at USED tires, here is an easy way to tell how much tread is left:
http://www.tirerack.com/winter/tech/tec ... ?techid=51

I is a lot finickier! Here is what I have and love: http://www.amazon.com/gp/product/B0015D ... detailpage



It measures in 32nds too, not just the millimeters shown. And $19 is not too expensive at all. Provides excellent accuracy to see how the tread is wearing across the width.

Regardless, a cheap pencil depth gauge should be mandatory for all of us ... before I got this fancy gauge, I simply kept one of those pencil depth gauges in all my glove boxes ... they are inexpensive enough and we should check our tires periodically to see how they are wearing across the tread width and adjust tire pressure up or down accordingly (but never going below 33psi for our cars!).

Z

[szh]

Also, I have driven many different cars with many different combinatiuons of tires and wheels and very few times have I seen the speedo accurate to a GPS unit. As long as I keep the OD fairly close I'm not too worried.

A good point ... I was actually surprised when I got my Garmin GPS going and saw that the speedo error was about - within the ability to estimate the speedo reading, of course - what I had calculated (see my tire charts in the stickies) would be the error based on the revolutions per mile specs for my tire.

Z