someone educate me about tires

[IlllI]

i never understood this so i thought i'd ask

say you have a car that uses 14in tires. they take those off and replace them with larger rims/tires

in my uneducated observation i dont see any benefit to doing this. is there any? or is it just for looks.

in fact, i would seem to think the smaller tires would last longer?

for one, the smaller tire has more rubber. theres more to the tire, so more = better?

using larger tire would make the tire wear out faster? b/c theres only like an inch and a half of rubber between that and the rim. also less air inside the tire too.

this is a bad comparison, but something like this vs this

 

[mwmorph]

Bad comparison, the amount of rubber does not affect how quickly the tire wears, tires do not drive on the sidewall after all. Tire wear is instead affected by depth of tread and tire compound chemistry.

The big wheel thing is a 2 part deal.

On one hand there is the financial flaunting of money. 20"rims and tires cost more than 14" rims and tires by a factor of at least 4.

On the other is style. Originally, sports cars had huge rims and tire diameters to fit bigger and bigger brakes inside the diameter. Nowadays, everyone wants them because that is the fashion right now and also people think it helps performance, mostly erroneously, as larger wheels and tires = more unsprung weight. Lower sidewalls = lss tire flex but that is balanced out by slower turn in, lower acceleration and worse ride all things being equal.

They're basically automotive jewelry. Just like on people, fashion costs a lot more, is less practical and all things being equal perform worse, but I guess that's part of the attraction. Whatever is less convenient is more desirable because it shows you're well off enough to maintain that lower level of convenience.

 

[StageLeft]

It's generally for appearance. I presume the larger would wear out marginally slower as a single revolution of it happens slower at any given speed so essentially there is more rubber to it.

Less of a profile on a tire can increase handling but also decreases comfort. More weight on the wheel, which is generally the case with tire and wheel "upgrades" results in a slower car as there is more rotational mass. So, if you're looking at a performance car and all you care about is 0-60, you'll generally do it a touch faster with the cheaper tires than the pricier ones as they're lighter.

 

[herm0016]

cars were designed with a specific size tire in mind, the suspension design, mass, and the damping of the tire are all considered. most of the time you are reducing perfromance by installing larger wheels with more weight, less damping, and changing the angle the suspension works at, changing your camber and tow suspension settings.

 

[exar333]

Originally posted by: Skoorb
It's generally for appearance. I presume the larger would wear out marginally slower as a single revolution of it happens slower at any given speed so essentially there is more rubber to it.

Less of a profile on a tire can increase handling but also decreases comfort. More weight on the wheel, which is generally the case with tire and wheel "upgrades" results in a slower car as there is more rotational mass. So, if you're looking at a performance car and all you care about is 0-60, you'll generally do it a touch faster with the cheaper tires than the pricier ones as they're lighter.

You are correct, provided the same material is used for the new wheel. Often times, larger wheels come in more exotic materials (aluminum, etc) that can help offset the weight differences.

 

[angry hampster]

Because mud tires won't fit on a (stock) civic.

 

[Gibson486]

from someone who owns a car that came with stock 17's.....dam....it's no longer an economy car....why any would want purposely get bigger tires...geesh, it is just a money pit. People thought at first that getting bigger tires increase traction and thus give you more grip, thus makes your 0-60 time faster. Now it is has become purely a fasion thing (Go to pep boys and you will see wanna be rims made of coated steel). Most do not realize that bigger tires lead to a less comfy ride. I drove an older 3 with 16 in. tires....the difference was very noticeable.

 

[halik]

Bigger wheels generally look better (to a point) and smaller sidewall improved steering response.

 

[IlllI]

so they serve no practical purpose and are mostly to show off.. hmm i kind of figured as much but i always wondered if there was some secret benefit that they had over stock wheels

 

[BlackTigers]

The only reason I'm upgrading mine is to get rid of some wheel gap, and my struts and springs will get rid of the rest of the gap.

In my case it's purely aesthetic.

 

[mwmorph]

Originally posted by: ExarKun333

Originally posted by: Skoorb
It's generally for appearance. I presume the larger would wear out marginally slower as a single revolution of it happens slower at any given speed so essentially there is more rubber to it.

Less of a profile on a tire can increase handling but also decreases comfort. More weight on the wheel, which is generally the case with tire and wheel "upgrades" results in a slower car as there is more rotational mass. So, if you're looking at a performance car and all you care about is 0-60, you'll generally do it a touch faster with the cheaper tires than the pricier ones as they're lighter.

You are correct, provided the same material is used for the new wheel. Often times, larger wheels come in more exotic materials (aluminum, etc) that can help offset the weight differences.

Both of you are partially correct.

I have never met anyone that swaps out tires to move to a higher outer diameter on non truck tires.

Swapping from 195/65/15 to 195/65/20 will increase your final drive because of the increased diameter, but that also throws your speedometer out of calibration. That is why people when upgrading tires, choose a tire that will give the same outer diameter and will cover the exact same distance with each revolution. For example, people would upgrade from 195/65/15 to 245/25/20 which would mean the speedo is only 0.6% off, a negligible difference in tire wear.

As for lighter materials, sure that would work, but most of the weight of a wheel is concentrated on the outer rim. As wheels grow in diameter, the weight moves further and further away from the center of the axle, increasing inertia. A car with a 15" 20lb rim will always accelerate faster than a car with a 20" 20lb rim, because the weight will be spread out further from the central mass and as weight moves away from the centre, each pound will induce proportionately more and more inertia.

 

[Knavish]

A couple of comments...
Like most people said above, the vast majority of people run big wheels to show off. I sometimes wonder if this is because of the way concept cars are drawn and displayed. When was the last time you saw a concept car (especially an artist's drawing) that didn't have the largest wheels that would possibly fit in the wheel well. I think it's a bit crazy... I suppose like most style trends, it will change eventually. Who knows, maybe whitewalls will come back

Also -- A few yrs ago Road&Track ran an article where the put a range of wheel sizes on a 5 series BMW (as I recall). At the time, they got the best handling out of 17" wheels. The 18 and 19s slightly decreased performance, and noticeably decreased ride quality.

 

[jtvang125]

Pros:
Better traction (more dependant on tread compound and tread design though)
fit larger brakes
Looks better (keeping size conservative)

Cons:
more expensive
tends to wear out faster (tread compound geared more towards performance)
harsher ride
more unsprung weight
more road noise

 

[alkemyst]

Originally posted by: herm0016
and changing the angle the suspension works at, changing your camber and tow suspension settings.

proper plus sizing should not affect these.

90% do this just for looks though even if they think it's adding performance. If done right the ending package should weigh the same or less than the originals.

Sticking with Plus sizing recommendations is usually going to ensure all you add is some weight and the noise, vibration and harshness that can come with less sidewall.

 

[KentState]

Cars get bigger, so the brakes get bigger, so them rims need to get bigger. Plus to keep the same proportions on larger cars, the size keeps growing. Look at a 90s Honda Accord and the car looks pretty good with 16" rims, but now the car is bigger by 10-20% and so have the size of the rims.

 

[ElFenix]

Originally posted by: ExarKun333

Originally posted by: Skoorb
It's generally for appearance. I presume the larger would wear out marginally slower as a single revolution of it happens slower at any given speed so essentially there is more rubber to it.

Less of a profile on a tire can increase handling but also decreases comfort. More weight on the wheel, which is generally the case with tire and wheel "upgrades" results in a slower car as there is more rotational mass. So, if you're looking at a performance car and all you care about is 0-60, you'll generally do it a touch faster with the cheaper tires than the pricier ones as they're lighter.

You are correct, provided the same material is used for the new wheel. Often times, larger wheels come in more exotic materials (aluminum, etc) that can help offset the weight differences.

stamped steel wheels don't weigh much and are often the same or less than what the aluminum wheels weigh. for example, PT cruiser's steelies weigh 17.0 lbs while the aluminum in the same size weighs 16.9 lbs.

further, moment of inertia increases with the square of the radius. so small changes in wheel diameter can cause big changes in the moment of inertia and the amount of energy needed to start and stop the wheel. so even if the wheel weighs a little less, pushing the mass a few more inches from the center could cancel out the savings.

of course, that could be balanced by tires that weigh less than stock, but i doubt the people getting 24s on their lumina have tires that weigh less than on the stock 15s.

 

[kalrith]

I think the performance difference between smaller and larger wheels depends on what size you start with. If you upgrade stock 14s to 16s, then I would think the increased handling from the lower-profile tire would offset the greater unsprung weight. If, however, you upgrade stock 18s to 20s, then you're likely to the point of diminishing returns, and 20s weigh a heckuva lot more than 18s.

I hate the trend these days to put not larger wheels on cars that are supposed to "sports cars". Take the new Camaro SS, for example. It comes with 245/45R20. I much prefer the 245/40R18 that Subaru puts on their STI. Less unsprung weight = better performance, but less bling, I guess. I suppose the typical consumer cares more about bling than performance.

 

[Zenmervolt]

Originally posted by: kalrith
I think the performance difference between smaller and larger wheels depends on what size you start with. If you upgrade stock 14s to 16s, then I would think the increased handling from the lower-profile tire would offset the greater unsprung weight.

And you'd be even better off with low-profile tires on those original 14" wheels and correcting the gearing mis-match with a software programmer. Admittedly that's a little more difficult.

The real issue there is that 14" wheels just don't allow for decently-sized brakes. You can fit low-profile tires to small wheels, but you can't shove big brakes inside of small wheels. (Of course, you could move to inboard brakes, but those have their own set of issues.)

ZV

 

[w00t]

car looks better with less wheel gap, you can lower your car, get bigger wheels, or both.

the only way I see it changing the performance

smaller wheel = lighter most likely

but it may speed up or slow down your speedo..

 

[Rifter]

You people who are saying they are just for looks are insane, or have just never driven on good low profile performance tires. I have a Honda CRX which comes with stock 14" wheels, they use 185/60 size tires. I also have a set of Konig Graphite 17" wheels that i run 205/40 size tires on in the summer. The car feels like a totally differnt car with the 17", it corners alot better brakes better accelerates better. Besides having more rubber on the road for more traction and lower profile tires for better cornering they are also lighter than my stock 14" wheels. I would drive with the 17" all year but they are not good in the snow I would reccomend anyone to get larger low pro tires for the summer its alot more fun to drive. Just make sure the wheels you get are light not heavy as if you get wheels that are heavy you will need better brakes.

 

[Zenmervolt]

Originally posted by: Rifterut
You people who are saying they are just for looks are insane, or have just never driven on good low profile performance tires. I have a Honda CRX which comes with stock 14" wheels, they use 185/60 size tires. I also have a set of Konig Graphite 17" wheels that i run 205/40 size tires on in the summer. The car feels like a totally differnt car with the 17", it corners alot better brakes better accelerates better.

I'm going to call bullshit on the bolded part. You may think it accelerates and brakes better, but it is beyond unlikely that there is any measurable difference. I'll concede that the additional width, softer tire compound, and different tread pattern of the larger tires may help some in braking, but it is unlikely.

Additionally, the move from 185 series tires to 205 series tires is a huge jump in width, plus there are changes in tire construction and compound. Most 185 series tires today are long-wearing tires designed for low price; this is not a set of design constraints that are conducive to overall grip. 205/40 tires are going to be designed more for sporting use and will feature stiffer sidewall construction, softer rubber, and a tread pattern that is more optimized for grip. The difference in tread pattern, rubber compound, tire design, and width are the key players in the improvement you are seeing.

Also, you clearly do not understand a word that anyone in this thread has said. No-one is saying that low-profile tires are bad. What people are saying is that 205/40/14 tires would be a better choice (assuming that proper gearing for the speedometer could be retained) than moving to 205/40/17 tires. 205/40/14 tires would offer all of the same advantages of 205/40/17 tires without requiring the larger wheels.

Once again, the only reason to fit larger wheels, aside from cosmetics, is to fit larger brakes.

In your case, things are blurred slightly as it is currently almost impossible to find "performance" tires in 14" diameters and the fact that 205 series tires would be too wide for your stock wheels, meaning that you would need to replace the wheels to fit the wider tires anyway.

ZV

 

[Rifter]

You can think what you want, it does brake better and accelerate better, its basic physics of having more rubber on the road and having lighter wheels(my 17"s are 9lbs lighter each wheel than my stock 14"'s, this is almost a 25% weight savings per wheel). But in my case i have snow tires on my 14's and high performance summer tires on my 17's so its not so good of an idea to compare but i did state in my first post i had summer wheels/tires and winter wheels/tires. If you want to argue that winter tires can accelerate at the same rate as summer tires you are insane, obviosly the summer tires have more grip and can launch faster otherwise people would not bother with performance/slick tire to drag race they would just run with whatever they have on the car. If the tires i have were the same width and design it would be closer or not even a difference except cornering where the tire profile would help, but in my case this is not the case. But even if you had the SAME tire tread/compound design in 185/60 and 205/40 the larger tires will stop/start faster every time as they will be able to put more braking/accelerating power to the road to stop/start you faster. If i were to run 205/40/14's even if i could find them and fit them on my wheels which i might be able to do the overall diameter of my wheels/tires would be way way off(by 3+ inches) and the suspension geometry would also be off as well as the hight of my car, the 205/40/17 tires/wheels are within half a inch of the same size as the 185/60/14's so my speedo and suspension maintain the proper geometry/readings. And as you said it is impossible to find a high performance tire in 14" size.

 

[Zenmervolt]

Originally posted by: Rifterut
If you want to argue that winter tires can accelerate at the same rate as summer tires you are insane, obviosly the summer tires have more grip and can launch faster otherwise people would not bother with performance/slick tire to drag race they would just run with whatever they have on the car.

First of all: Good god man. Paragraphs. Use them.

Secondly, comparing a drag car to a 108 hp (at best) CRX is not an apt comparison. Also, I did not say that winter tires are as grippy as summer tires. If you think I said that, you clearly need to focus on augmenting your reading comprehension skills.

If the tires have the same compound and the same tread design, you're not going to see a difference unless you need to move to wider tires. Larger wheel diameter is irrelevant here.

You are trying to say that larger wheels are better. However, your own comparison contains so many additional uncontrolled variables (e.g. different widths, different compounds, different tread patterns, different wheel materials) that it cannot be taken seriously. The faults in you comparison method are both obvious and myriad.

Your comparison of 185/60 R14 winter tires against 205/40 R17 summer tires is, quite simply, not valid as a means of demonstrating that larger wheels are helpful in and of themselves.

ZV

 

[Zenmervolt]

Originally posted by: Rifterut
But even if you had the SAME tire tread/compound design in 185/60 and 205/40 the larger tires will stop/start faster every time as they will be able to put more braking/accelerating power to the road to stop/start you faster.

That says all anyone in this thread needs to know about your (lack of) understanding.

The wider tires will be able to grip better, yes. But the change from a 14" to a 17" wheel has nothing to do with that whatsoever.

ZV

 

[PlasmaBomb]

Originally posted by: Zenmervolt

Originally posted by: Rifterut
If you want to argue that winter tires can accelerate at the same rate as summer tires you are insane, obviosly the summer tires have more grip and can launch faster otherwise people would not bother with performance/slick tire to drag race they would just run with whatever they have on the car.

First of all: Good god man. Paragraphs. Use them.

Seconded.