Tire Question

[Jay 02 TA ws6]

I have Bridgestone Potenza tires on my Legacy. They are specifically noted in the owner's manual as a "summer tire".

Exactly how bad are these things going to be during the winter when there are 6+ inches of snow on the roads? I have symmetrical AWD, but I'm figuring that isn't going to do me a lot of good when all four wheels have no traction.

The tires are size 215/30(or 35)/R18. The problem is the guy at Discount Tire told me there was no real good choice for an all-season tire in that size, and I would need to go with tires and rims down to 16's... YUCK! I already cruise on the highway at 3100 RPMs... if I go down to 16's, I'll be at like 3400, and that's just not an option.

Any suggestions? Thanks!

[Jeff_in_Atl]

The tire rack shows N/A for snow. 215/35WR18
http://www.tirerack.com/tires/tires....e1=yes&place=0
They show no winter only tires in that size.
They show 4 "Ultra High Performance All-Season"
http://www.tirerack.com/tires/Compar...=All&x=45&y=11
They show no other "all season" tires for that size.

[Injuneer]

.... The problem is the guy at Discount Tire told me there was no real good choice for an all-season tire in that size, and I would need to go with tires and rims down to 16's... YUCK! I already cruise on the highway at 3100 RPMs... if I go down to 16's, I'll be at like 3400, and that's just not an option.

Any suggestions? Thanks!

Why would going from 18" wheels to 16" wheels change your cruise RPM? You just need to select the correct tire diameter, to match what you have now. If you're running a 215/35-18, you would look for a 205/50-16.

[Jay 02 TA ws6]

Why would going from 18" wheels to 16" wheels change your cruise RPM? You just need to select the correct tire diameter, to match what you have now. If you're running a 215/35-18, you would look for a 205/50-16.

Right, I understand that... I forgot to mention that I asked that question specifically, and we talked about heights of the tire, etc... it came out that the wheel/tire combination he recommended was indeed much smaller than what I currently have. It would have changed the crusie RPM.

[wolfdogs]

get some spare rims, if you want an excelent all season wet, dry, snow, ice traction tire, the Michelin Cross Terrain is awesome.

[Dave M]

I can't really recommend a tire but I can tell you that you will need a winter/all-season tire. Two co-workers of mine have an STi and an Evo, both AWD cars and they both say traction in the winter is xistant with their summer tires.

[Jay 02 TA ws6]

I was wrong about the stock tire size - it's 215/45/18

But, a 215/35/18 will work... any idea how much this is going to change my RPMs at cruising speed? Should I re-calibrate my speedo?

What fraction of a 215/45/18 is a 215/35/18 in circumference?

[Performin Norman]

Jay,

It takes a big man to admit he's wrong. LOL

I would think your car would do fine being AWD. However, some on here have talked from experience.

[Trash man]

jay a 215/55R16 tire would be about the same hight maybe be off a 1/4 inch. look up on tire-rack they have a chart

[Jay 02 TA ws6]

Yeah Norm, with the first snow, I learned there is no way I would make it through the winter with the summer tires... braking was non-existent and acceleration was suspect as well...

I got the 215/35/18s installed today... the guy told me it will be too small of a change in circumference to produce any noticeable difference in cruise speed/RPMs... is that right?

[Trash man]

whyd u go with a smaller tire? the sidewall is now narrower i prob woulda done a 205/60R16 tire, same high and a lil bit more narrrower so u dont ride the snow

[Jay 02 TA ws6]

whyd u go with a smaller tire? the sidewall is now narrower i prob woulda done a 205/60R16 tire, same high and a lil bit more narrrower so u dont ride the snow

Because then I would have had to buy new rims as well.

[Trash man]

Bone yards are u friend. did subbie use same pattern for all the cars? i kno when i got 2 spare rims for my frist car(93 taraus) it only cost me 25$ for both of em from the tire shop

[Jay 02 TA ws6]

Can someone please help with the question about the speedo?

I'm not very familiar with tires at all...

As I understand it, the first number (215) is the width of the tire in millimeters, then the second number (35) is the height of the sidewall as a percentage of the width of the tread. So, a 215/35 would have a sidewall 10% shorter than a 215/45.

So each sidewall is 21.5 millimeters shorter - or 2.15 centimeters, meaning the whole circumference of the tire is 4.3 centimeters shorter.

The 18" wheel is 45.72 centimeters... the stock tire would have a sidewall height of (215 * 45%=) 96.75 millimeters - or 9.675 centimeters (seems really high)... Multiplied by 2 is 19.35 cm. Add this to the diameter of the wheel gives a total diameter of 99.72 cm.

If the total diameter of the wheel was 99.72 cm, and it's now 4.3 cm shorter, then that is a 4.3121% change so my speedo would be off by that much... so if I was driving along at 70 mph, my speedo would be off by slightly over 3 mph... if my speedo reads 70s, I'm actually only doing about 67.

Guys like Fred, Joe, Kevin, wolfman... how'd I do? Is that math anywhere near accurate?

[Jay 02 TA ws6]

Bone yards are u friend. did subbie use same pattern for all the cars? i kno when i got 2 spare rims for my frist car(93 taraus) it only cost me 25$ for both of em from the tire shop

I had no interest in buying new rims - especially not ones from a junkyard. Not to mention how much the handling characteristics would be effected by such a large sidewall... as it is right now, my car carves turns like a Thanksgiving turkey - I'd prefer to retain as much of that as possible.