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Tire Speed Ratings


Eneto-55
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Looking at some snow tires for our family car (AKA “my wife’s car”).  Before now, I was unacquainted with the “Speed Rating” part of the tire code.  But I am still not sure I understand it, at least in the case of the tires I’m looking at.  

Here’s the specific tire: Bridgstone Blizzak DM-V2 P235/65R17S XL.
Which is the speed rating, the ‘S’, or the ‘L’?

Why this tire?  The car (2019 Honda CR-V EX-L) comes with P235/60R18 tires.  I want to drop down to 17” steel rims for the winter tires.  
Why the smaller size? Somewhat lower cost, more tire height, used 17” steel rims available.
Why steel Rims? Avoid the reaction between the normal aluminum wheels and the steel it’s mounted to. The much lower cost. Personal preference – I don’t like the looks of aluminum wheels.  (I’m weird that way.)

Re: matching the tire sizes: The tire size comparison:
P235/60R18 – 91.4” circumference; 693 revolutions/mile
P235/65R17 – 91.1 circumference; 695 revolutions/mile

So this specific tire comes up in the tire size matching charts, by both circumference and by Revolutions per mile.  BUT, it is not available in the ‘T’ speed rating for passenger cars – this particular tire is designated for ‘light trucks’ (by which I assume they mean ‘Pick ups’, which in my upbringing and dialect are not considered ‘trucks’ – That would mean a 1 ton or more.)

Notice in the speed rating chart that the ‘L’ designation has a top sustained speed of 75 MPH.  We don’t drive that fast in the snow around here, and have the street tires for Summer time.  But if the ‘XL’ is not the speed rating for this tire, then it is an ‘S’ rated tire, and there’re no more questions in my mind.

OR, Would you all suggest just sticking with the 18” tires for both Summer & Winter?  (I can purchase 4 new 18” steel rims for about 4 times the cost of the 4 used 17’s – $300.00 compared to $75.00.)
 

Tire Speed Rating Chart.JPG

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I would have no problem changing the wheels assuming they would fit over the brake rotors?

 

I always thought the speed rating was a combo of rubber compound & tread design.

For a sports car tire, would have a soft rubber compound that would really grab the pavement & probably a more aggressive tread design for traction.

This tire would wear out more quickly, then a harder less aggressive tread tire.

 

 

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27 minutes ago, Los_Control said:

I would have no problem changing the wheels assuming they would fit over the brake rotors?

 

I always thought the speed rating was a combo of rubber compound & tread design.

For a sports car tire, would have a soft rubber compound that would really grab the pavement & probably a more aggressive tread design for traction.

This tire would wear out more quickly, then a harder less aggressive tread tire.

 

 

From what I understand, these Blizzak tires do have a softer rubber used on the first 55% (as I recall) of the tread, then they perform as regular mud & snow tires.  

 

There's lots of room around the rotors, and the 17" wheels are used on the base model.  I've looked through the "features charts" for what is added for each model, and larger-size brakes are not mentioned anywhere.

[What I don't understand is what is driving this trend toward larger and larger wheels.  Is it just looks?  Not that I personally think it looks any better.  Maybe just an excuse for higher prices?  But what about the added unsprung weight, and additional wear & tear on the suspension?]

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1 hour ago, Eneto-55 said:

[What I don't understand is what is driving this trend toward larger and larger wheels.  Is it just looks?  Not that I personally think it looks any better.  Maybe just an excuse for higher prices?  But what about the added unsprung weight, and additional wear & tear on the suspension?]

Shorter sidewalls improve handling as there is less 'leverage' to lift the outer part of the tread during cornering.  So at a give OD to match the overall gearing and shortening the sidewall results in a bigger hole in the middle to fill with a wheel.     In most cases that is also the reason for alloy wheels, reduce unsprung weight and suspension motion that must be dampened by the shocks.

 

 

It may be my overactive imagination but I think I can feel the difference when comparing the same vehicle with steel wheels and alloy.  Seems to have more 'bounce' on certain roads.   I don't think size is much of an issue, but on a lighter vehicle the added weight may be noticeable on some roads.

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2 hours ago, kencombs said:

Shorter sidewalls improve handling as there is less 'leverage' to lift the outer part of the tread during cornering.  So at a give OD to match the overall gearing and shortening the sidewall results in a bigger hole in the middle to fill with a wheel.     In most cases that is also the reason for alloy wheels, reduce unsprung weight and suspension motion that must be dampened by the shocks.

 

 

It may be my overactive imagination but I think I can feel the difference when comparing the same vehicle with steel wheels and alloy.  Seems to have more 'bounce' on certain roads.   I don't think size is much of an issue, but on a lighter vehicle the added weight may be noticeable on some roads.

I do get the deal about handling.  But I'm a very sedate driver, and don't do any race car tactics, especially not in the snow.

 

I would have also thought that the aluminum wheels would be significantly lighter, so when I bought an aluminum open box trailer (4 x 8), I got the aluminum wheel option.  Later I took one off and weighed it, as compared to a steel wheel with the same size tire on it.  There was very little difference at all.  

 

Regarding the gearing, I had wondered if there was a significant weight gain in the transmission, by basically lower gearing.  (Not being an engineer, I don't even know if that makes any sense.)  The only advantages I can think of for large wheels are 1.) possible weight reduction in the transmission, and 2.) the larger the wheel the less it will drop into deep pot holes.  I could understand the logic in the latter, if our roads were still like they were in the 20's and 30's, but not really today.  And as to the first, any gains in transmission weight would have to be enough to overcome the additional weight of the larger wheels & tires.  (And, in an on-line search, I found no ADVANTAGES for greater unsprung weight.  The much wider tires must already be much heavier than the tires that came on our P15s, for instance.  Or is that just because I'm older now, and everything feels heavier than it used to?)  So what I'm left with (as a reason for the large wheels on modern vehicles) is greater revenue for the tire manufacturers, and 'looks'.  (Neither of which concern me.)

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I Weighed the spare wheel and tire for my old 97 F150.  265r16 and one of the aluminum version on the truck.  I don't remember the actual weight but the difference was about 10lbs.  I have a set of Jeep factory 15s for my 56 project and they are nearly 9 lbs lighter than a 15" mopar cop wheel from the 70s.

 

There is almost no difference in the OD of the standard wheel and tire package and the oversize aluminum options on most, if not all cars.  Like my Tundra, it has 20s on it, aluminum.  The standard package is an 18" wheel with a 70 series tire.  My 20s use a 55 series tire.  Net difference in most tire brands is under 3mm diameter.

 

So, pot hole drop is the same, weight of the wheel and narrower sidewall is much less.  Reduced unsprung weight is a good thing as it reduces the work the shocks have to do.  And the reduction is most noticeable, IMO as the ratio of unsprung to vehicle weight gets worse,  lighter car/truck, heavier wheel/tire.

Edit to add:  Steel belted radials, even in a similar size will be heavier than OEMs on our old cars, for obvious reasons. steel construction vs nylon or rayon.   I think the tread width vs sidewall mass is mostly a wash.

Edited by kencombs
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2 hours ago, kencombs said:

I Weighed the spare wheel and tire for my old 97 F150.  265r16 and one of the aluminum version on the truck.  I don't remember the actual weight but the difference was about 10lbs.  I have a set of Jeep factory 15s for my 56 project and they are nearly 9 lbs lighter than a 15" mopar cop wheel from the 70s.

 

There is almost no difference in the OD of the standard wheel and tire package and the oversize aluminum options on most, if not all cars.  Like my Tundra, it has 20s on it, aluminum.  The standard package is an 18" wheel with a 70 series tire.  My 20s use a 55 series tire.  Net difference in most tire brands is under 3mm diameter.

 

So, pot hole drop is the same, weight of the wheel and narrower sidewall is much less.  Reduced unsprung weight is a good thing as it reduces the work the shocks have to do.  And the reduction is most noticeable, IMO as the ratio of unsprung to vehicle weight gets worse,  lighter car/truck, heavier wheel/tire.

Edit to add:  Steel belted radials, even in a similar size will be heavier than OEMs on our old cars, for obvious reasons. steel construction vs nylon or rayon.   I think the tread width vs sidewall mass is mostly a wash.

OK.  My memory may be faulty on the weight comparison.  If I get an opportunity, I'll do that again, but not in this cold we're having right now.  But while I was holding off on purchasing the set of used steel wheels, to get a better feel for what was the correct course, they sold last night or this morning.  (They had been listed for around a month, so I thought waiting a day wouldn't matter.)  So anyway, the same guy has a set of alloy wheels; twice the money, but still a good deal.  He's holding them for us, and my son-in-law will be picking them up for me on Monday.  So the weight difference question is not important at the moment - just my curiosity at this point.

Thanks to all who contributed to my understanding on all of this.

Edited by Eneto-55
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Tire rack lists tire weight in the specs tab if anyone is really curious, lol. 

 

I just got done reshoeing my BMW, 4 Michelin Pilot Sport AS4's, more than $1200.  But they are an Ultra High Performance All-Season tire, 25 lbs each and are Y speed rated.  That's 186mph, can my BMW do it?  Nope, limited to 155.  Can I even use that top end?  Nope, not legally anyway, lol.  Though Goodyear's proving grounds are here and they are hiring for a tester, hmm...

 

Now the tires I have on the back of the 51 are P255/50R17 that are W speed rated.  168mph, way over kill, but the price was good and they fill the rear wheel wells nicely, about the same over all diameter.  When I get motivated I will pull one rear tire setup, put it in the front and see how well it will fit.  Then I can complain about manual steering, lol.

 

 

 

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The speed rating on tires also has a lot to do with the contact patch (amount of tire actually in contact with the road surface) when operating at higher speeds.  The centrifugal force of the tire spinning at speed forces the center of the tire outward.  Even with the car's weight, the contact patch that was the full width of the tire at rest and "lower" speeds, is now only a few inches at best.  Not a problem at "highway speeds", but once you start exceeding 100 mph or so it becomes a problem.  One of the reasons a car gets "squirrely" at high speeds with normal tires, and why high speed rated tires make a car ride like an ox cart since they are engineered to keep as much rubber on the road as possible - they are stiff.  This from my retired TX State Trooper brother who was one of the TX Highway Patrol's driving instructors and a certified "special service vehicle" (read: Camaro and Mustang) operator when they had those.

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Another question, only sort of related, but hate to start a new thread....

 

Did I say that I ended up getting some used Honda alloys?  Anyway, I got them this morning, and they say on them "for TPMS".  Will regular valve stems work on wheels like that?  I don't care about the pressure monitor system - I'd rather be responsible for my tire pressures myself anyway.  I don't care if they are there, but not so crazy about the extra expense, just for winter tires.

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Another question:  What do you all think of running spacers on the front wheels?

 

(There is a bit of caliper interference, a bit less than 1/4".  The thinnest spacers are 5mm.  But this would push the wheel out far enough that the wheel would no longer engage the flange on the hub.  (So in my thinking, that would make it "lug bearing", not "hub bearing".  Not crazy about doing this.)

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I have a set of 1.5" spacers that bolt to the hubs and has it's own studs.  It is also machined to be hub centric at both the hub and wheel interfaces.  That is the only kind of spacer I would consider, but it probably overkill for you. 

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8 minutes ago, Sniper said:

I have a set of 1.5" spacers that bolt to the hubs and has it's own studs.  It is also machined to be hub centric at both the hub and wheel interfaces.  That is the only kind of spacer I would consider, but it probably overkill for you. 

I've seen those on-line, and wondered how that works.  Is the 1.5" enough that the lug nuts holding the spacer to the hub do not interfere with mounting the wheel, or do you have to replace the studs in the hub?  I don't want to do the latter, because in my situation this "solution" is only for the winter wheels/tires.  The idea then would be to get some steel wheels that have a full 1" extra backspace (5.5 instead of 4.5), then use 1" spacers.  The advantage would be that the 1" spacers would be thick enough to have a hub-centric flange extending into the wheel hole.  (I'm still not convinced that the hub itself is not weight-bearing in relation to the wheel.  There's a lot of back & forth in that discussion, but a lot of the younger crowd seem to be totally unaware of how our old cars were designed, with a very substantial hub structure that not only centers the wheel, but also, I would argue, supports it.)

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1 hour ago, Sniper said:

I haven't had a problem with the hub mounted studs interfering with the wheel mounting.  Hub centric is the only way to go, imo.

Thanks. Do the lug nuts extend beyond the 1.5" spacers at all?  Are there recesses between the lug holes in your wheels, and if so, do the hub to spacer lugs correspond with  the recesses in the back of the wheel?  (One or the other of these Honda wheels has recesses between the lug holes and the other doesn't.  I'm thinking that the 17s are the ones with the recessed areas, rather than the stock 18s.  But I wasn't thinking of this question when we had them off.  I would need to run up to my rented shop to look at the 17s.)

 

The 5mm spacers aren't thick enough to leave room for a hub-centric flange.  So I don't think I want to use them.  And I suppose that a person should not dare to grind away any part of the inside of the wheel.  If it was only up to a couple of millimeters (1/8"), I might do it.  But it would also affect the wheel balance, unless it was done very carefully, to consistently remove the same amount of material all around the wheel.  That would pretty much require a metal lathe operation to feel confident about something of that nature.

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I have never needed to use wheel spacers. .... I would feel fine using them as long as they are quality made.

I watched this guy build this truck on youtube, I know he has been driving it for over a year pulling a large trailer .... it is a solid work truck.

It is a 8 lug Dodge 3/4 or 1 ton axles with semi truck super singles 22.5 wheels mounted using the magic of wheel spacers.

 

Not sure if this would be considered severe Duty use .... they certainly do work if built right ..... these were built by his buddy who has a machine shop.

 

 

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1 hour ago, Eneto-55 said:

Thanks. Do the lug nuts extend beyond the 1.5" spacers at all?

I used the lug bolts original to the car, they do not interfere.  I have not tried the spacers since I converted to discs, yet.

 

1 hour ago, Eneto-55 said:

Are there recesses between the lug holes in your wheels, and if so, do the hub to spacer lugs correspond with  the recesses in the back of the wheel? 

 

Yes and yes

 

1 hour ago, Eneto-55 said:

And I suppose that a person should not dare to grind away any part of the inside of the wheel.

 

Not a good idea, though you might be able to shave some off the calipers.  I haven't done either but have heard of others doing that.  Not sure I would shave the calipers, they don't make them any thicker than needed any more so you might be gambling with a losing hand there.

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7 hours ago, Sniper said:

I used the lug bolts original to the car, they do not interfere.  I have not tried the spacers since I converted to discs, yet.

 

 

Yes and yes

 

 

Not a good idea, though you might be able to shave some off the calipers.  I haven't done either but have heard of others doing that.  Not sure I would shave the calipers, they don't make them any thicker than needed any more so you might be gambling with a losing hand there.

That's what my son-in-law suggested, until we saw how much would have to be removed.  (We put washers on two of the lugs, and kept adding more until the wheel spokes cleared the caliper support.  The two washers (together) made up about 7/32", and we figured that a 20 mm spacer would make it clear, although it would still be pretty close.  (I didn't use a micrometer to measure the washers, so I could be a bit off.)

Today I found some wheels on Summit Racing (CRR-83-7714) that might fit, with 1" spacers.  It's the type that has two sets or patterns of lug bolt holes, one for 4.5" and the other for 4.25".  (Our CR-V uses the 4.5" pattern.)  This wheel's back space is 5.5" instead of 4.5", so if I understand how all of that works, then the 1" spacers would put it right back on the money, and the ends of the stock lugs bolts holding the spacer to the hub could stick through the extra holes in the wheel.  (This type of spacer has an additional set of lug bolts, which are used to fasten the wheel to the spacer.  I have also seen people saying not to use this kind, that one should get loner lug bolts, so that they run all the way through from the hub to the wheel.  But this is only for winter tires - I need to be able to remove the spacers when I put the summer tires back on in the Spring.)  But also wondering if all those holes weakens the structure of the wheel.

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