What are auto makers thinking with all the 17"+ wheels?

[outrun]

Performance is definately a draw.

Personally I think larger rims are more attractive.

OEM large rotors and multi piston calipers are nice too.

It may force you to buy better performance tires.

That or being stuck with OE S/T rated tires during a Moose in the way emergency swerve.

 

[CapriRacer]

quote:

---

Actually, the 'load index'/maximum load is for the load rating, while load range seems to be for handling.

---

Sorry - Load Index, Maximum Load, and Load Range are different ways of saying the same thing - the maximum load carrying capacity of the tire.

Load Range doesn't have anything to do with handling characterisitics.

Speed ratings on the other hand: While the rating itself is not a handling parameter, good handling is usually desireable in a vehicle that requires higher speed rated tires - so it is common for higher speed rated tires to have better handling characteristics.

Hope this helps.

 

[1sttruck]

"Sorry - Load Index, Maximum Load, and Load Range are different ways of saying the same thing - the maximum load carrying capacity of the tire.

Load Range doesn't have anything to do with handling characterisitics."

Looking at tires for my truck one can find a number of tires rated for around 3000 lbs, they state the maximum load as such, and they'll have pretty much the same load index, typically 118 to 121 or so, but some are load range D while others are load range E. The big difference in other specs betwen the two is that the load range E will have an 80 psi max while the load range D will have either a 65 psi or 50 psi max depending on tire size.

If maximum load, load index and load range are all supposed to be the same, why are they in fact different ? Why does Dodge state that load range E tires are needed, and not state that load range D with a 3000 lb max or 120 load index is acceptable ? Load range is spec'd as it's needed for towing and hauling heavyier loads, where sidewall deflection needs to be taken into consideration.

 

[CapriRacer]

May be a little lesson in tire engineering is in order:

If you look very carefully at the relationship between Load Index and maximum load capacity, you will find almost a one to one relationship. The reason it's not an EXACT one to one is that the US standardizing body - the Tire and Rim Association - does the load calculation first, then translates that to Load Index, where ETRTO - European Tire and Rim Technical Organization - formulates its loading standards STRICTLY on Load Index.

For tires: Air = Load Capacity. The larger the tire, the greater the load capacity. The higher the inflation pressure, the greater the load capacity.

Each of these standardizing organizations publishes a book that has the relationship between load and inflation pressure by size.

When we are talking about LT tires, which use Load Range to indicate the inflation pressure upper limits, the maximum load capacity is determined a combination of the maximum inflation pressure and the size.

Many P/U truck manufacturers will use a tire with a larger load capacity for those heavy duty trucks designed for towing big trailers - and this is a good idea from a vehicle design point of view. But you can get a similar effect using a higher inflation pressure - if your tires are designed for the higher pressure.

BTW, sidewall stiffness is more a function of inflation pressure than it is a function of load range. Sure the Load Range E tire is stiffer than the Load Range D tire, but the actual contruction effects are fairly small compared to the siffness that is added when you inflate the tire.

So putting a Load Range E tire on a vehicle that calls for a Load Range D tire is a good idea, paticularly if you use a little more inflation pressure. (But be aware, it is possible to use too much pressure.)

As far as what a given vehicle manufacturer "specs" on a given truck: There are quite a few considerations - Load capacity, physical dimensions available in the fender well, purchasing cost, etc. My impression is that vehicle manufacturers spec P/U trucks with fairly small physical dimensions, then use higher load ranges to get the load capacity. This also results in a less costly tire.
So typically an LT235/85R16 or a LT245/75R16 (both Load Range E) is used.

Having said that, I note that recently vehicle manufacturers moved to 17" and 18" tires on their P/U trucks.

Hope this helps.

 

[JHZR2]

Doesnt load range C, D, E have to do with the number of plies on the tire? THis of course will effect pressure and load handling capacity, but I was under the impression that all range C tires were 3-ply, and all E tires were 5-ply.

JMH

 

[CapriRacer]

"Doesnt load range C, D, E have to do with the number of plies on the tire? "

In a manner of speaking, but the number of plies is the result of standardization.

BTW, it's the ply material that counts, not the belts. The belts stiffen the tread area and restrict the circumference of the tire, but really don't factor into the load range issue.

It takes more strength to contain more air pessure. The strength needed goes up as the tire size goes up. So an LT235/85R16 at 50 psi needs more strength than an LT215/85R16 at 50 psi. Also an LT235/85R16 at 80 psi needs more strength than it does at 50 psi.

So the tire standardizing bodies have break off points they called Load Ranges to delineate the difference, so the proper tires can be fitted to vehicles. They decided how to do this decades ago.

The net effect of this is that when a tire manufacturer specifies what ply materials are used in the factory, they also have to standardize - but since time has moved on, (we've moved from nylon to polyester, for example, and from bias to radials) the break off points for the factory don't exactly line up with the break off points for the Load Ranges.

But what commonly happens is that lower Load Range will use a high density fabric, but a single ply, and a higher Lower Range will use a lower density fabric, but with 2 plies.

But just to confuse things further - a modern Load Range H Radial truck tire (at 120 psi) uses a single steel ply. Needless to say, if they used polyester, they'd have to use more plies.

Hope this helps.

 

[XS650]

quote:

---

Originally posted by JHZR2:
Doesnt load range C, D, E have to do with the number of plies on the tire? THis of course will effect pressure and load handling capacity, but I was under the impression that all range C tires were 3-ply, and all E tires were 5-ply.

JMH

---

No. The load rating is load rating. How many plys they use to meet the requirement is up to the manufacturer.

30 or so years ago, tire weight capacity was directly tied to ply rating.

 

[Audi Junkie]

Big brakes? Under most circumstances, braking distances are limited by available TIRE grip, especially in poor weather conditions. Anyway, my A4 calls for 205/55-16. I don't have sport packege, so it's full ride height. After having a chance to run some leftover 215/55-16s, I took a chance and ordered 205/60-16s. For me, it works great...better ride, I roll right over potholes. Also the price is a bit better. I just paid $58 installed for Bridgestone Fusions. I do however run 4 mounted sets, 3 all-seasons and 1 15" snows. Basicly, I use the newest set for winter (snows are a new aquisition for me, but the principle is the same) they aree later rotated to become the Fall/Spring set...eventually they are the summer "smokers". I would need a new set every year othrwise...basicly I still buy new ones almost that often, except my "winter" set is good for 2 good winters instead of 1. I put snows on for maybe a month. Wait, I'm OT now! What I am getting at is that one good size is fine all year around. No way do I want to pay extra beyond the $80 or so each every year. $1 a day is too much for freaking tires. Also, lower is not better. 17"s seem too expensive, don't work well in snow and choices are limited. Bigger rims bending easier is just a bonus.

 

[ekpolk]

A couple thoughts on 17" wheels. I do like the way they look on my G sedan; they're just well proportioned compared to the size and lines of the car. Unfortunately, as you push in the 17 and above range, you're usually also looking at relatively low profile tires, 215/55-17 in my case. That, in turn, means punishing ride. Yes, I like the handling, and I'd still have bought the car, but as I push into my second year of driving on New Orleans' dark-side-of-the-moon streets, I'm thinking that I'll just go ahead and get on the kidney transplant list now and get it over with.

Oh yeah, with 17+ wheels, tires become obscenely expensive and short-lived. My first set of replacements is in transit from Tirerack as I write this -- Avons at "only" $113 apiece. Most mainstream tires are above $150, some well over $200 per tire. Owwwwwww.

 

[JHZR2]

quote:

---

Originally posted by ekpolk:
Oh yeah, with 17+ wheels, tires become obscenely expensive and short-lived. My first set of replacements is in transit from Tirerack as I write this -- Avons at "only" $113 apiece. Most mainstream tires are above $150, some well over $200 per tire. Owwwwwww.

---

Which was my point for starting this thread... With average joe american having 0 savings, thousands in credit card debt, a leased car that they really dont care about beyond being able to trade it at the end of the lease, and most peoples' infatuation with showing off, keeping up with the joneses, and showing just how "rich and well off" they are, when they really are so deep in the red it isnt funny...

Whats to say they will ever desire or end up springing for a good set of tires when theirs go bald. Theyll choose the higher risk of driving on crappy used tires, for the sake of saving $$$, especially when the tires are over $100 each.

Do keep in mind that these are the same folks who didnt replace their tires before, or if they did, used the cheapo no name brands... and anyone is expecting better now with 17"+ wheels on their cars, tires that tend to grade lower in wet stopping, treadlife, etc.?

Couple less frequent replacement (due to financial position and replacement cost) with low insurance coverage levels (due to financial position), and I think it edges the risk for tire/control/traction related accidents higher and higher... Not a good thing.

JMH

 

[ekpolk]

There is certainly an element of truth in this, but the situation is, IMO, a bit more complex. One of the factors that drives the cost up in the low-profile 17+ range of tires is the performance ratings of the available choices. There are few, if any, that are less than H-rated, and the majority seem to be V or even W rated (at least in my size). H tires are rated up to 130 mph, V to 149. My chances of seeing speeds anywhere near these is about dead zero -- 80-85 on the interstates (when appropriate) is my max. Anyway, in this segment of the market, there are very few "crappy" or even dangerous tires of the sort you find when shopping for S rated 205/75-14s. In my own defense, Avon is essentially a "boutique" tire maker that's trying to penetrate more of the main US market (they supply the likes of Rolls-Royce). We'll find out shortly whether the $200 I saved (on the set) by passing on the Goodyears and Michelins was worth it.

 

[JHZR2]

yes but there is a majority of low-lifetime, fast wear, and limited traction offerings out there, which when worn down to the limit in 20k miles, will be more unsafe than the crappy s-rated tires that exist now... especially as these expensive tires get worn down to the belts and casings.

JMH

 

[tom slick]

my F-150's 17" rims just clear the calipers on the front. a 16" rim certainly would not fit at all.

 

[1sttruck]

"Big brakes? Under most circumstances, braking distances are limited by available TIRE grip, especially in poor weather conditions."

Maybe with some sort of sporty vehicle, but on a truck with a load brake fade is a serious issue, more so on hills. Even diesel pickups find that 'exhaust' or compression brakes are useful, as are large 4 wheel discs; I do like mine.

 

[ekpolk]

In the spirit of developing the thought (vs. hairsplitting), I'd point out that this class of tire is often short-lived/fast wearing as a result of having a soft, sticky tread compound. This, in turn, results in an extraordinarily high traction tire, so I'd respectfully disagree with the low traction part of what you said, unless you were referring to snow (or other bad surface) traction. On the other hand, the ultimate danger may be even greater than you suggest, since these tires also seem to give up their ferocious grip very quickly once they reach a certain stage of advanced wear. The unthinking clod may not realize that anything's wrong until he's spinning in the grass taking out innocent pedestrians.

 

[rjundi]

Our 2005 Legacy GT has really pretty 17" (215/45ZR17) tire/rims. I really like them and the way they look and the grippy tires. My only qualm is no steel wheels avail in this size for the winter. However the 2006 WRX will have these rims also standard so the younger set will sell these rims rock bottom so I can get some winter traction.

 

[thrace]

Bigger diameter wheels often go with lower profile tires. Lower profile tires allow more damage to wheels just in normal driving through potholes. This could lead to fatally damaging a wheel. Just another way of increasing operating costs and inconvenience.

 

[ekpolk]

quote:

---

Originally posted by thrace:
Bigger diameter wheels often go with lower profile tires. Lower profile tires allow more damage to wheels just in normal driving through potholes. This could lead to fatally damaging a wheel. Just another way of increasing operating costs and inconvenience.

---

This is definitely something to watch carefully, and an issue that makes tire selection all the more critical. Some tire designs are configured with a "rim protector", which is either a ridge or just a "fattening" of the sidewall so that it offers the edge of the rim some "cover." The newly installed Avons I'm running on my G35 (described recently in nearby thread) seem to have a particularly good rim protector. Tires without a protector leave that expensive wheel awfully close to curbs and parking bumpers.

 

[javacontour]

quote:

---

Originally posted by Quattro Pete:

quote:

---

Originally posted by slugsgomoo:
When i went from 205/55/16 to 235/45/17 my tires increased in width by 30mm, decreased in height significantly, and shaved nearly EIGHT POUNDS off their weight.

---

Are you saying that a 235/45/17 tire weighs 8 lbs less than a 205/55/16??

Not a chance. Most 235/45/17 high perf. summer tires weigh about 24-27 lbs; 205/55/16 - 21-24 lbs. Best case scenario, your tire weight remained the same.

Low profile tires require more reinforcement materials plus they're generally wider (like in your case), hence the increased weight.

quote:

---

It also helped that my new wheels (17x8) weigh 19lbs, and my old 16x6 crapulences weighed 27lbs. Overall, that's an almost 16lb savings per corner.

---

Very lightweight (forged) rims are expensive and hence not used as OEM on most cars. You'll find most OEM 17x8 cast rims to weigh around 25-28 lbs. Now, if you know what you're doing, of course you can shave some weight, but this generally doesn't apply to most factory OEM setups.

FYI, I've got two setups currently:

winter:
205/55/16 (23 lbs) on 16x7 rims (21 lbs) = 44 lbs

summer:
225/45/17 (22 lbs) on 17x8 rims (17.5 lbs) = 39.5 lbs

But that's only because I picked my summer rims and tires based on weight.

An average 225/45/17x8 combo weighs about 45-50 lbs otherwise.

---

Did the same thing with my SVT Contour. The factory 16" wheels weighed about 19-20# before putting a 205-55-16 tire on there.

I purchased a set of OZ Superleggeras in a 17x7, IIRC and each wheel was only 15.5#

Dropped 3-4# and was able to mount a 215-45-17 on the wheel.

Of course, the wheels and tires shipped to me were about $2k

TB

 

[edwardh1]

probably like that in the roman charriot days

hey claudius don't you want the upgrade with the bigger wheels for only 1000 dinaries more?