Author Topic: auto tire experts sought...  (Read 3435 times)

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mattsz

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on: November 12, 2014, 10:01:54 pm
So, my car came with 175/65R15 tires.  I want to put "snow" tires on, and the local shop wants to mount 195/65R15 snows.

The first number is the width of the tread, right?  2 cm wider than the OEM all-weather tires... does this sound normal for snow tire mounting?


Arizoni

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Reply #1 on: November 12, 2014, 10:21:23 pm
If you were planning on driving in sandy washes, wider tires will keep the tires from sinking in like the narrow stock tires would.

I mention that because sandy washes and dunes are about as close to snow as my imagination can get, living here in the desert as I do.  (I've got to drive over 100 miles to get up to the snow country. :) )

Actually, I have driven on snow and I don't know which condition I think is better:
Sinking into the snow deeply so there is something on the side of the tires to help turn?
Riding on top of the snow so you are less likely to get stuck.

I guess I'll sit back and hear from all of you snow birds that have to drive in that crap.
Jim
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High On Octane

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Reply #2 on: November 13, 2014, 12:37:16 am
The thing with tire sizing is that numbers aren't exactly a set number.  The first number represents the width profile, the second number is actually an aspect ratio of the first number.  I don't know exactly how it works, but I believe the second number is actually a percentage.  But to make it simple, with the aspect ratio, or sidewall profile, the lower the number the shorter the sidewall, and vice versa.  That being said, normally going a size or 2 bigger in width generally doesn't cause any issues.  If you go too wide tho the tire can start rubbing on the spring perch of the strut.  You should be ok, but it is a good idea to stay with the OEM tire size.  I HIGHLY recommend the Hankook I-Pike tires.  Awesome traction and ride!  I have them on my wife's Hyundai Accent and my Subi.
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Vince

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Reply #3 on: November 13, 2014, 12:54:34 am
     The width is 175mm. The height is 65% of the width-114mm. The rolling diameter will be 550mm. While the wider tire also has 65% profile, the ride height is 127mm with a rolling diameter of 612mm.
    On a bike this is huge. On a car probably not so much. The 10% difference in rolling diameter will affect the speedo reading.
     Stock rim width is generally optimized for the stock tire. This means that the wider tire may not have the optimum profile. Squeezing the beads closer together with the wider tire on the narrow rim usually results in the center of the tread carrying the load rather that the load being more evenly supported by the entire tread. This affects wear and handling. You'll probably have to experiment with tire pressure to find a good compromise with wear and handling.
     With the higher ride height the tire will tend to squirm more. Tire pressure that would minimize squirm will adversely affect the wear/handling compromise.
     I tell my customers that if they "need" a wider tire, they need a better tire. If you want to go with the wider tires you should seriously consider wider rims. Check for fender and wheel well clearance.
     Installing wider tires on your existing rims will work OK, it's just not the best choice. Regular snow tire users often have them mounted to their own rims. The switch is then easy to do. Change the wheel/rim assemblies to save yourself the twice yearly trip to and cost at the tire store.
     Buy cheap rims. It's winter and they'll be dirty anyway.


High On Octane

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Reply #4 on: November 13, 2014, 01:11:23 am
mattz - I was just doing some research and the 175/65/15 is quite an odd size with very limited tire options.  I'm thinking you may be better off just getting those 195/65/15.  They should fit ok and any inaccuracies with the speedo will be very minimal.
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REpozer

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Reply #5 on: November 13, 2014, 01:31:13 am
     The width is 175mm. The height is 65% of the width-114mm. The rolling diameter will be 550mm. While the wider tire also has 65% profile, the ride height is 127mm with a rolling diameter of 612mm.
    On a bike this is huge. On a car probably not so much. The 10% difference in rolling diameter will affect the speedo reading.
     Stock rim width is generally optimized for the stock tire. This means that the wider tire may not have the optimum profile. Squeezing the beads closer together with the wider tire on the narrow rim usually results in the center of the tread carrying the load rather that the load being more evenly supported by the entire tread. This affects wear and handling. You'll probably have to experiment with tire pressure to find a good compromise with wear and handling.
     With the higher ride height the tire will tend to squirm more. Tire pressure that would minimize squirm will adversely affect the wear/handling compromise.
     I tell my customers that if they "need" a wider tire, they need a better tire. If you want to go with the wider tires you should seriously consider wider rims. Check for fender and wheel well clearance.
     Installing wider tires on your existing rims will work OK, it's just not the best choice. Regular snow tire users often have them mounted to their own rims. The switch is then easy to do. Change the wheel/rim assemblies to save yourself the twice yearly trip to and cost at the tire store.
     Buy cheap rims. It's winter and they'll be dirty anyway.
As usual Vince is right .
The tire store has this size in stock and wants to move product.
If the new tires are a good deal , consider them. I don't know of any real advantage to going bigger on snow tires. It's possible the bigger tires might bottom out on a heavy load or rub the fender wells in a parking lot tight turn.
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singhg5

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Reply #6 on: November 13, 2014, 01:45:59 am
It is a coincidence that yesterday I had watched some videos on what these tire specs mean, that are well known at least superficially. There are many videos but this one guy has an interesting take on it that others do not. Link below.

The 3 tire numbers are unusual combination of different measuring systems - millimeter, %, and inches !!  Go figure who came up with this idea. Just keeping them all in one measuring unit would be so much easier - mm.

Width - mm, aspect ratio % of width, and diameter of wheel at bead - inches.

Here is the interesting part. The first number is NOT tread width (according to this guy on video, and he shows it by measuring a tire). The first number is Cross-Section Width of the tire at widest point, which is usually from one side wall to other side. He also mentioned something about difference in racing and street tires, in their measurements. These values can be different from manufacturer to manufacturer.

To confirm his idea, I was measuring the width of our RE tires today. I have some pictures and will post them later and try to get opinions from others as to how they interpret them. Because when I measured the width of Avon Speedmaster MKII front tire, which is labeled as 3.25x19 inch, there was no point that measured 3.25 inches accurately. The widest point was 3.5 inches (at cross-section) and at tread it was less than 3.25 inches !! So what does the first number (width size) really tell me ? May be my tire has distorted ?
 
Anyway, back to the link of this guy -

http://www.youtube.com/watch?v=WJNF5bnI65Q   
« Last Edit: November 13, 2014, 02:25:57 am by singhg5 »
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mattsz

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Reply #7 on: November 13, 2014, 02:42:22 am
Thanks guys!

I have limited choices in my area - I want to support the local joint, where they've gone out of their way to help us on short notice on a number of occasions.

I'll ask them what they've got available for order, and sizing.  The size I listed above was a "quick quote" and might be a simple adjustment...


High On Octane

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Reply #8 on: November 13, 2014, 02:54:07 am
Singh - That is correct about the cross-section, as that is the correct term for that measurement.  The 1st number doesn't refer to the "tread width" itself, tho it is relevant to the cross section.  Meaning, the first number is not necessarily the width of the actual tread, but overall width of the tire itself from sidewall to sidewall.

Mattz - What car are these tires for?  Like I mentioned, the 175/65/15 is an odd size.  I'd like to know the car so I can help you decide on a good compromise for size vs availability.  Which can affect the overall cost of the tires all said and done.
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singhg5

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Reply #9 on: November 13, 2014, 05:25:53 am
There was an interesting thread last year on the size of tires for RE. The question was 'is 100/90-19 the same size as 3.25 x 19 inch tire'

If first number 100 mm is divided by 25.4 to convert into inches, it comes to 3.94 inches.

Vince had mentioned that for motorcycles, anything 100/90 is equivalent to 3.5 inches for FRONT tire and 4 inches of REAR tire ! Even though number is same.

Bare had said that 90/90 is equivalent to 3.25 inches, even though 90 mm divided by 25.4 is 3.54 inches !

The point is that this first number can be different for tires that are equivalent or considered equivalent from another manufacturer.

Extending the same analogy, I wonder if it is possible that tires designed for one purpose of usage may have slightly different numerical value due to its design profile than its equivalent tire designed for another purpose. Just my hypothesis.

I will find link to that thread.   
« Last Edit: November 13, 2014, 05:47:03 am by singhg5 »
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singhg5

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Reply #10 on: November 13, 2014, 05:38:10 am
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motorman2whel

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Reply #11 on: November 13, 2014, 09:42:15 am
I think in general you want a snow & ice tire that is the same or narrower than a standard tire for better traction. Were not talking Artic exploration thru very deep snow. You don't want "flotation" on snow with a street car, much like hydroplaning on wet roads its not good. Even the Rally racing cars use narrower tires on snow & ice. If you want a aggressive winter only tire, the Firestone Winterforce radial with or without studs is a great choice.
« Last Edit: November 13, 2014, 09:50:59 am by motorman2whel »


mattsz

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Reply #12 on: November 13, 2014, 11:45:44 am
Mattz - What car are these tires for?  Like I mentioned, the 175/65/15 is an odd size.  I'd like to know the car so I can help you decide on a good compromise for size vs availability.  Which can affect the overall cost of the tires all said and done.

Scotty, the tires are for my wife's 2014 Toyota Prius c (the baby one).  175/65R15 are what came on the car.  I asked my local tire shop (a Cooper Tires franchise) for a quote on 4 snow tires to fit my car, no other info or instructions, and the quote they gave me was for Cooper Weather-Master S/T2 tires in the 195 size, $505 out the door.  I'm sure they can order other tires if I ask for them.

It seems like I can do a little better price-wise if I go further afield, but these are the guys who take care of the routine maintenance of our cars, and when we have a sudden concern about a noise or problem we want them to check out, they say, "we've got an opening in half-an-hour, is that ok?"  So, I'm willing to keep my business with them...

The dealer we bought the car from is an hour away - they offered Michelin x-ice tires (I didn't ask the size) for $600, but they charge double the local guys' seasonal switch-over costs.

Still debating buying extra wheels to go with the tires - I'd still want to have them balanced each switch-over, so I'd have to bring them in anyway...


High On Octane

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Reply #13 on: November 13, 2014, 12:17:39 pm
The thing to do Matt it's search Craigslist and local salvage yards for a an extra set of steel wheels for your car.  You can generally find them for cheap and then you don't have to continue to waste time and money on swapping tires every spring and fall.

As for sizes, maybe going to 175/60/15 will give you better options than the 195/65/15.
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mattsz

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Reply #14 on: November 13, 2014, 12:37:21 pm
Update:

I called my local guys again - got the manager this time and asked about the size discrepancy - it didn't sound right to him.  First time, I just told the counter guy the car I had, but this time he asked me the tire size.  He confirmed that our car should have the smaller size, and that it is indeed an unusual size - small Prius's (Pri-i?), and some Minis are about it.  They can easily get Bridgestone Blizzaks (which he says he likes) in the right size or special order something much more expensive.

As for wheels, I'm still on the fence.  Right now, I don't "waste" time on swapping tires, because I take the car to them - and they do the job in the time it would take me to switch wheels myself.  Plus, they check and adjust the balance of each one, each time.  It does cost money, of course...

Junkyards and Craigslist around here are a challenge - you have to either wait for a local deal, or be willing to drive pretty far.  Plus, there's the cost of new tire pressure sensors in all 4 wheels - I wonder what the ramifications are of running without them?  Dash lights on all winter, probably, at a minimum?  She won't go for it.

I'll probably just get tires now, and look into new wheels for next season...


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Reply #15 on: November 13, 2014, 03:11:15 pm
If getting a set of used wheels is difficult in your region then just get the tires for now.  The Blizzaks are awesome snow tires as well, but I didn't recommend them because they are pricey.  But if you can get a good deal them in the correct size, then I would say definitely go that route.  Perhaps mention to the manager that you are in fact a loyal customer.  Sometimes the small guys will give dedicated loyal customers a bit of a discount, or maybe mount them free of charge.  Never hurts to ask.
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mattsz

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Reply #16 on: November 13, 2014, 03:19:37 pm
Thanks Scottie!  I'll certainly ask...


AussieDave

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Reply #17 on: November 14, 2014, 02:58:39 am
I don't know what you want four tyres for Mattz. Two should be plenty! Anything that needs more has to many wheels and should be avoided!  :)
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mattsz

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Reply #18 on: November 14, 2014, 11:47:54 am
Yeah, I know, Dave... that's fine for us, but I need four tires for my wife's vehicle:



High On Octane

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Reply #19 on: November 15, 2014, 08:59:03 pm
Matt, did you get your tire situation figured out?
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mattsz

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Reply #20 on: November 15, 2014, 09:15:55 pm
Yes Scottie, I did.  Turns out, I only need three tires for my wife's vehicle - that fourth one's cosmetic.



Sorry.  I went ahead and ordered the Blizzaks through my local guy - he'll install them next Saturday.  Tires only; I'll worry about extra wheels some other time.

Thanks again, everyone, for your input!!