All Season Tire DD Thoughts

[Vimy101]

I am torn between getting stock LGT 17" rims which provides a lot more A/S tire choices for the cold months or just changing to an A/S seasonally on the Spec.s 18" wheels. The big problem with the latter is that there is only one, that's right, one tire that comes in the OEM size! They are the Pirellis. I've read many reviews on Tire Rack about this tire and the reviews are all over the map. Some love them others hate 'em. Some say they wear like iron while some say they are trashed well before the wear rating.

 

Not one review ever mentions the tire pressure they have been running which with the Pirelli that has a max inflation pressure of 51 would make a profound difference all over its performance spectrum. Going with the standard 32 psi means that the tire is almost 20lbs below its design limit which is where all tires are tested. Higher max inflation tires are lightly constructed compared to ones that have a max of 35lbs for instance. Inflating the Pirelli to max cold inflation would make it an entirely different tire than if it were filled to Subaru OEM inflation specs.

 

 

Tires have a shelf life wherein ozone oxidation will begin to degrade them and this is especially important with lightly constructed ones. An additional advantage to going to separate wheels for winter and summer is that for storage purposes one could inflate the stored tires with pure nitrogen which would greatly aid in preventing oxidation of the rubber thus preserving their design charateristics.

 

 

Few people seem to be aware that high speed runs in very hot summer temps will cook a tire (especially most A/S) and degrade their performance which is why there are summer tires that are built to withstand heat build up. This is why people who get new tires are always so impressed with them initially. It's because they haven't been cooked yet. When they get cooked, tires get hard and lose strength and grip and if they are underinflated it compounds the problem.

 

 

From what I can tell - and please correct me if I'm wrong - remounting a set of tires costs about $40. Therefore, it will cost me $80 per year (and time) going the one set of wheels route. Anyone know how much OEM 17" rims going for?

[jim1969]

I have the pirellis on the 17" tire. I run 37f/35r tire pressure. They are great all season tires.

[Vimy101]

I have the pirellis on the 17" tire. I run 37f/35r tire pressure. They are great all season tires.

 

It is amazing to think that you are still more than 10 lbs below the OEM design specs. I tend to favour lower max inflation tires as they are more robustly contructed. However, the LGT is a pretty light car so perhaps this shouldn't be as much of a concern to me now.

 

Have you ever tired your Pirellis at or near to their max inflation? I wonder how they would feel at that pressure.

[jim1969]

I'll try it out.

[Vimy101]

I'll try it out.

 

Cool. It will be interesting to read your opinion.

 

On the NICO site, there was a lot of tire talk amongst the J30 and especially Q45 owners because they are comparitively heavy vehicles. I didn't really follow the tire talk on the newer models like the G35 or M unfortunately. That said, the consensus was that lower max inflation tires with their stronger sidewalls run at their max cold inflation was the way to go. I did this on my YK420s are they wore like iron. However, the Q guys didn't have much luck with them and it was put down to the fact that the Q had a different suspension set up and really needed a higher speed rating than the H of the 420s.

[ilh]

I think you should run 17" in the winter. Even then you'll be on 45- or 50-series tires.

 

I would run 16" on my LGT for winter if they would clear the brakes.

 

--Lee

[Vimy101]

I think you should run 17" in the winter. Even then you'll be on 45- or 50-series tires.

 

I would run 16" on my LGT for winter if they would clear the brakes.

 

--Lee

 

Any particular reason you would want to run a smaller wheel? If I do go for a 17", I'd be looking to keep the same diameter which will necessitate a sturdier sidewall than I think the Pirelli can provide. However, with the smaller wheel I'll have a lot more choices so perhaps the Nokian or Avon.

[MilesA]

Running a smaller diameter wheel would allow you to run a higher-profile tire. A tall and skinny tire cuts through snow better than a lower, fatter tire. Ride is also more comfortable in nasty winter conditions with the higher-profile tires; you are less likely to bend a wheel, too.

[tantal]

Mounting and balancing a set of tires is going to cost you more like $80 a shot rather than $40 a shot.

 

Definately just buy a second set of wheels if you are going to run two sets of rubber. Don't remount twice a year - it's hard on both rims and tires.

[krzyss]

It is amazing to think that you are still more than 10 lbs below the OEM design specs. I tend to favour lower max inflation tires as they are more robustly contructed. However, the LGT is a pretty light car so perhaps this shouldn't be as much of a concern to me now.

 

Have you ever tired your Pirellis at or near to their max inflation? I wonder how they would feel at that pressure.

 

May I ask where do you get your info?

As far as I can tell Subaru pressure numbers apply to all tires matching OEM size. Pirelli 51 PSI is max pressure that you may need when running full load capacity at max speed (sustained).

 

Krzys

 

PS Why do you think lower max pressure tires are more sturdy than high pressure (usually higher speed rated and higher load index) tires? I would expect just opposite.

[ilh]

Around here it is closer to $100 to mount 4 tires. That is if you don't want the monkeys at the chain stores scratching your wheels. Every tire change is a potential scratch.

 

Let's see, with 17-inch wheels, keeping close to your 215/45R18 diameter, you could go to 215/50R17 and have options such as Dunlop Winter Sport M3, Dunlop Graspic DS-2, Bridgestone Blizzak WS-50, and Michelin X-Ice. You would also have 1/2-inch more sidewall to soak up the winter potholes.

 

225/50R17 might be an option too that offers even more choices, but that increases the diameter a little bit.

 

I am likely to go with 205/50R17 for the winter, which is about 1/4-inch more sidewall than stock 215/45R17. My speedo will actually be more accurate since mine typically reads about 2% low with my stock RE92s.

 

--Lee

[Vimy101]

May I ask where do you get your info?

As far as I can tell Subaru pressure numbers apply to all tires matching OEM size. Pirelli 51 PSI is max pressure that you may need when running full load capacity at max speed (sustained).

 

Krzys

 

PS Why do you think lower max pressure tires are more sturdy than high pressure (usually higher speed rated and higher load index) tires? I would expect just opposite.

 

Not all tires are created equal. OEMs provide their suggested inflation pressures to get the handling charateristics they feel the car should have and in most cases they're thinking Joe/Jane Blow. The most infamous case of an OEM recommending inadequate pressures was Ford with the Explorer. There was nothing wrong with the tire if it had been properly inflated but people were running the tire at and probably most often under Firestone's designed pressure. The heat build up leed to catastrophic tire failure and usually of the a rear tire which is the worst case scenario.

 

Heat build up in tires is created by sidewall flex in the main and, as we all know, heat is the enemy especially when it comes to rubber compounds. Tire OEMs design the tire and test it at max cold inflation. However, a tire design is only tested for a matter of minutes and only has to maintain its integrity for the duration of the test to attain whatever speed rating the OEM is after.

 

Lower max inflation tires keep their form at lower pressures because they are more robustly constructed. High max inflation tires are cheaper to make and are lighter because there simply isn't as much material in them. Because there is less material in them, high max pressure tires can be built to higher speed ratings more cheaply because there is less centrifical force trying to tear them apart. Load rating applies equally across the spectrum.

 

My knowledge comes from reading hundreds of posts on the subject (and related links) on the NICO site (a shadow of its former self now sad to say) that dealt with heavy early Qs and Js.

 

If your tires are more than 6 months old or have been subject to extreme heating; i.e, high speed runs in hot summer weather, be very circumspect about running your car near or at its tires' speed rating.

[Vimy101]

Good advice re having goofballs scratching my rims up and not doing the job right the first time. I want to keep the diameter as close to the OEM set up as possible and the 17" wheel will give so many more options. An aggressive AS will meet my needs here in Chicagoland where I do lots of freeway cruising and my driveway is level.

[Garandman]

Running a smaller diameter wheel would allow you to run a higher-profile tire. A tall and skinny tire cuts through snow better than a lower, fatter tire. ////

 

SAAB said this about the 155x15 tires on my 1969 SAAB 96. And every year tires on cars get wider and they are more capable in bad weather.

 

ADAC (German Auto Club) states that narrower tires are better on wet roads and slush, but that on hard packed snow and ice at low temperatures, a wider tire might be better.

 

In most of Europe the manufacturer must designate the allowable sizes, so you can only purchase what is specified. Sometimes the designated snow tire sizes are narrower or smaller so they can clear tire chains.

[Vimy101]

When at speed, slush is by far the most dangerous "snow" condition one encounters on a regular basis in the US temperate region and narrower tires will cut through it better. The most tricky to maintain traction in is wet snow. Ice is ice when and where it happens and there's not much you can do about it. Even studs are next to useless.

 

There have been improvements in rubber compounds and to a lesser degree tread design. It's all about compromise in the end.

[ilh]

Regarding ADAC recommendations, note that they didn't give a single 225/45R17 tire more than 1 star (3 being the best) due to the width and low profile. They really didn't like that size and say if you can go down to 205 width that would be their first choice. At 205/55 they had several 3-star tires.

 

--Lee

[Guest]

$40 for remounting and balancing?

 

I wish it was true here. The cheapest I found it's $20/tire in 17". With road force balancing it's $30/tire.

 

Ripoff, ha?

[tantal]

Well, it is expensive, but I wouldn't call it a ripoff. There is an hour's worth of labor or more involved. Everyone needs to earn a living. Problem is that since it is this much money, you have to find a good shop; otherwise it's not worth it.

[Garandman]

Regarding ADAC recommendations, note that they didn't give a single 225/45R17 tire more than 1 star (3 being the best) due to the width and low profile. They really didn't like that size and say if you can go down to 205 width that would be their first choice. At 205/55 they had several 3-star tires.

 

--Lee

The test of that size was in 2003.

 

Taking the example of the Dunlop WinterSport M3, the smallest size tested got two stars; the middle size got three; and the 225/45r17 got one. Kinda hard to draw any conclusion about the tire or sizes.

[krzyss]

I am asking some gurus from other web sites for help answering you but...

 

It is the air that carries you not tires. Tires just keep air in one place.

 

We agree that "Heat build up in tires is created by sidewall flex in the main and, as we all know, heat is the enemy especially when it comes to rubber compounds."

What we do not agree is how to fight it.

Untill recently passenger tires in the USA were rated up to 35PSI because load tables published in USA were only up to 35PSI.

Europe was different animal, I suspect because of Germany. There was a need to design/define tires to be able to support load at much higher speeds. Even cheap cars in Europe can go 100mph, sustained and legally (in Germany again). So vendors/standard organization created load index tables that stretched to 44 and then 51 PSI (I guess some kind of metric equivalent ;-).

In the interim some tires made in USA still had 35PSI MAX pressure embeded on them even though the same tires being built in different coutry could have had 51.

 

Higher published MAX PSI enables manufactures to claim something like this on inside of my VW Passat fuel flap:

 

up to 100mph above 100mph

F R F R

half load 28 28 30 30

full load 30 32 32 39

 

The numbers are from memory and are wrong but idea is preserved ;-)

 

Do not forget that at higher sustained speed the tire must:

survive higher centrifugal force (tire rotates faster)

the flex that IS the source of heat is happening more often as tire is rotating faster.

 

To reduce the flex you bump the pressure, it reduces the heat but the tire needs to withstand this higher pressure after being driven for hours in the summer in the sun. When manufacturer says that tire load is x and speed rating is y, the tire is supposed to carry this weight at such speed until there is any tread left and then some.

 

I think that high speed rated tires are better than lower speed rated tires as they are built to withstand higher operating temperature, give you bigger margin of error, handle better. Higher Max Pressure on the sidewall is just result of making tire to handle the load at higher speed.

 

Krzys

 

PS I might be wrong but never uncertain - I took it from somebody else but it is true about me ;-)

[Vimy101]

Good thoughts in your post re the history of inflation standards. Higher speed tires are indeed more strongly built. However, in order to attain the speed rating a tire only has to remain intact at the design maximum speed and load under simulated conditions for something less than 10 minutes.

 

Could you repost your VW's inflation recommendations? I'm not quite getting them in the format they showed up in your post.

[krzyss]

board software removes white space and formatting is lost

 

Krzys

 

PS I will get real numbers at home and post them later.

[Vimy101]

I just called my local Sube dealer to find out what stock LGT 17" wheels would cost. $300 each.

[ilh]

Nobody would buy new. There are always some available used here.

[JuxtaGT]

Might also be worth looking at what type of mounting hardware your tire place has. Most cheaper places have a single lever system that can destroy a tire's sidewall when taking it off. I have to go to a higher end place that uses a dual lever "touchless" machine to get tires taken off without risk of damage. It cost me $60 just to get the tires taken off.

 

Just get a second set of wheels. Or, like many here, keep your stock wheels for winter and get a nice set for summer.