Hi! My sister is buying a new car, and it comes with four rim sizes: 15, 16, 17, and 18 inches. I don't know what the advantages/disadvantages between smaller/larger rim sizes. What should she choose? Thanks.
rim size
- Thread starter cprince
- Start date
In a non performance car, Larger rims (18 inches and up) can hurt acceleration and handling by increasing the unsprung weight of the car. They can also hurt the car's ride because very low profile tires with stiff sidewalls must be used. This is especially true when small cars (with relatively weak engines) like Honda Civics are fitted with 18"+ "bling" rims that weigh well over 25 pounds each.
If she is buying a performance car, however, then lightweight rims of a larger diameter (up to a certain extent...18 inches or so) can be an advantage since many high performance tires are low-profile and utilize very stiff sidewalls to maximize the contact patch and prevent sidewall flex under cornering and other high stress situations. However, these lightweight forged (high performance rims are almost always forged instead of cast) rims (BBS, Rays/Volk, etc) can cost thousands for a set of 4.
If she is buying a performance car, however, then lightweight rims of a larger diameter (up to a certain extent...18 inches or so) can be an advantage since many high performance tires are low-profile and utilize very stiff sidewalls to maximize the contact patch and prevent sidewall flex under cornering and other high stress situations. However, these lightweight forged (high performance rims are almost always forged instead of cast) rims (BBS, Rays/Volk, etc) can cost thousands for a set of 4.
the bigger the rim, the worse the ride. tires also become more expensive to replace, and it is easier to damage the rim. they also tend to weigh more, which increases the wear and tear on your suspension, steering, and brakes, and makes the car accelerate slower. in return, you sometimes get marginal handling improvements due to reduced sidewall flex. it is said that anything over 18" provides no noticeable handling improvement.
style is another issue, and some people think that the bigger wheels look better, and they are willing to put up with the penalties in order to look "cool."
style is another issue, and some people think that the bigger wheels look better, and they are willing to put up with the penalties in order to look "cool."
Rims are functionally only useful for stuffing larger brakes in, otherwise larger rims are always a bad idea. F1 runs 13 or 14" rims, Lemans runs 13" except in close cockpit(more aerodynamic) cars which are punished by having to run 14" rims, Nascar is standardized with 15" rims.
Stylistically if you can pair up a bigger rin with bigger brakes, it can look very nice, but functionally, its worthless.
Stylistically if you can pair up a bigger rin with bigger brakes, it can look very nice, but functionally, its worthless.
boomerang
Lifer
- Jun 19, 2000
- 18,883
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Have her pick the ones she likes the most.
If the manufacturer offers them as standard equipment, the ride issue should be a non-issue. The suspension should be softened to offset the stiffer sidewalls.
However, if in order to get the wheels she wants, she must get them as part of a performance package she can expect a stiffer ride.
Racing analogies used in regards to a street car are useless in my opinion.
If the manufacturer offers them as standard equipment, the ride issue should be a non-issue. The suspension should be softened to offset the stiffer sidewalls.
However, if in order to get the wheels she wants, she must get them as part of a performance package she can expect a stiffer ride.
Racing analogies used in regards to a street car are useless in my opinion.
LeMans Prototype car rims are bigger than 13 Best pic i could find in a rush..
To me that looks much bigger than 13 inches...
Until you consider the difference between 15" and 18" rims are going to be probably 3-5/10ths of a second in acceleration.
I was off by half a inch
http://bankspower.com/DmaxTypeR-Chs6.cfm
13.5 and 14.5"
I got it mixed up though, on closed cockpit LMP1s, the wheels can only be 14" wide(contact area) while open can be 16" or something like that. Max diameter i think for LMP1s are 16" also but i dont think any team runs that since the car would be uncompetitive with the extra unsprung weight.
A larger rim is not going to hamper acceleration to the point that anyone can tell it in the seat of their pants or with a clock...as long as the overall tire diameter is still the same. The little bit of unsprung weight is insignificant. You'll lose MUCH more performance by carrying a bowling ball in the trunk.
Larger rims will make the car ride worse, again, if the overall tire diameter is the same as with a smaller rim. Basically, to fit the larger diameter rim, you have to lose some sidewall, which is where your tire flex comes from. More flex=smoother ride. Less flex=better handling, at the expense of the ride quality.
That's why I don't understand people who buy a truck or SUV and put some huge rims and low-profile tires on there....they've absolutely KILLED their towing ability by doing that.
Honestly, for your sister...it won't make a difference. Just get the ones she thinks look better...she probably won't be able to tell a dime's worth of difference.
Larger rims will make the car ride worse, again, if the overall tire diameter is the same as with a smaller rim. Basically, to fit the larger diameter rim, you have to lose some sidewall, which is where your tire flex comes from. More flex=smoother ride. Less flex=better handling, at the expense of the ride quality.
That's why I don't understand people who buy a truck or SUV and put some huge rims and low-profile tires on there....they've absolutely KILLED their towing ability by doing that.
Honestly, for your sister...it won't make a difference. Just get the ones she thinks look better...she probably won't be able to tell a dime's worth of difference.
996GT has it right on the dot. unsprung weight can hamper performance more than you think packman multiply the weight by 1.5, and thats the weight sprung...hurts more, kinda the reason im going with 17's that weigh 17lbs each for track use only.(BBS magnesium forged rims, but i'd rather go with a nicer set of 16's that are light too, and those cost around 2,000 for all four.) the larger rims will help with crusing more since the whole circumference is larger and requires less rpms to cover the same amount of distance. but it will also require more fuel to get up to that speed since the mass is higher.
This is what matters most to me.
If the only tires available for the wheel are high performance tires, the rubber will probably wear out faster, too. So you get to pay more, more often.
Go to www.tirerack.com and price out some of the different sized tires for the vehicle. You may want to reconsider a tire/rim size if the only tires available are ultra high performance ones that cost an arm and a leg.
If you drive in winter conditions, I think the larger rims tend to have wider tires, which are not as good in snow, or so I hear.
The difference in weight of a 16" aluminum rim and the same rim in a 18" is not significant.
You don't need any calculation. All you need to do is weigh the rims. You're talking 20lbs, max difference for a set of 4.
A street car will NOT be able to tell a performance difference and you won't see one of the drag strip, either.....unless it's because of the lower profile tires hampering the launch.
On a race car, where thousandths of a second count? Maybe. But we are talking some dude's sister's car. There will be NO noticeable difference, in anything but the way they look to her.
Plus, with regards to weight of wheels, there's a whole other world of thinking on that...you have to consider WHERE the rims weigh more, not just their overall weight. A 30lb rim that has most of the weight in the center will affect performance less than a 25lbs rim with most of the weight on the outside, etc, etc, etc.
Bottom line, there will be no noticeable difference on a stock street car, so getting off on really technical, minimal difference tangents is irrelevant in this case.
yeah, your right on where the weight is, weight on the outside will hamper more, but more weight is still worse. hampers braking distance, and acceleration in all cases. unsprung weight is calculated to 1.5x and thats the weight sprung, so you do need some type of math because it will hurt gas mileage in city driving when the size of the rim/tire doesnt actually help.
itch, yeah wider tires dont help in rain/snow conditions, my dad knows this from experience, as well as i do. they tend to go over the snow and rain instead of through it(hydroplaning if you like) but thats if you have more surface patch and not enough gaps in the tires for the water to go elsewhere, you can find all weather tires. just remember this, your brakes really aren't the thing stopping you, its your tires. don't have grip? you don't stop end of story.(yes that is rather off topic as well.)
itch, yeah wider tires dont help in rain/snow conditions, my dad knows this from experience, as well as i do. they tend to go over the snow and rain instead of through it(hydroplaning if you like) but thats if you have more surface patch and not enough gaps in the tires for the water to go elsewhere, you can find all weather tires. just remember this, your brakes really aren't the thing stopping you, its your tires. don't have grip? you don't stop end of story.(yes that is rather off topic as well.)
alkemyst
No Lifer
- Feb 13, 2001
- 83,769
- 19
- 81
A bowling ball in your trunk is sprung weight. Wheels are not only unsprung but they require centrifigual force to move them at each change of acceleration.
You can take the same car and put a set of 18's on it and run it down the track, then take a set of lightweight 15's and repeat...both with the same diameter so no gearing changes are introduced. The 15's will turn a better 1/4 mile time.
In a short track where acceleration and braking are paramount, even larger differences can be seen.
Now selection of rim can be based on many different criteria. I look for keeping my gearing within 3% so that the speedometer is accurate. If I had too I would look into recalibrating it....
To do this you follow Plus sizing. like a 205/55R16 equals a 245/40R17 or 235/45R17 at +1....I am running a 235/40R17. Tire size is also dependant on wheel width. Wheel width that works depends on the vehicle and the wheel's offset.
Increase rim size doesn't add harshness. Decreasing tire profile does. Also more performance oriented rubber rides 'harder' as even the same size as a touring tire.
It really depends on what you are looking for. If performance is key the lighter the wheel and tire the better. If looks are key then the biggest wheel and thinnest tire usually is the best looking to most people.
In both categories you need to find how much you want to give up to get to the extremes.
In cars where ultimate grip is needed one usually ends up cutting out body panels and adding flairs and changing the suspension in such a way that anything other than the smoothest tarmac will knock a tooth lose.
Also keep in mind at the larger is better end of the spectrum, braking is greatly affected by heavier wheel combos.
ViviTheMage
Lifer
IMO
smaller rims = more MPG
smaller rims = smaller tires and cheaper!
this is just what I think about smaller rims. go 17" rather common
smaller rims = more MPG
smaller rims = smaller tires and cheaper!
this is just what I think about smaller rims. go 17" rather common
Zenmervolt
Elite member
- Oct 22, 2000
- 24,514
- 44
- 91
F1 cars have brake sizes regulated and they cannot exceed a specific diameter. There's no need for wheels to clear larger brakes and they use the smallest wheels possible. Wheel diameter is also limited though.
The LeMans prototypes have more leeway in design and can have larger brakes, which necessitates larger wheels.
As has been said, larger wheels are beneficial to fit larger brakes, otherwise there's no reason to bother with them for anything other than aesthetic reasons.
ZV
Good points, but not exactly on topic with what I am saying, for the most part.
No, increasing rim size doesn't increase harshness, and yes, decreasing profile does....which is why I said "if the tire diameter remains the same, the ride will be worse", or something thereabouts. If the TIRE diameter remains the same, the only way you can get a larger diameter rim is by decreasing profile. That's a given. I thought everyone knew that here, so I didn't elaborate.
As far as a set of 15's vs. 18's at the drag strip, again, many different factors come into play, to the point that you can't really compare apples to apples.
First, you're going to have a different size sidewall with each set of rims, IF the tire diameter stays constant.
So you have a problem there, because the shorter sidewall the 18's have is going to adversely affect traction. So that's a problem with the comparison.
Next, you have to figure where you are putting the extra weight of the 18's, assuming there is any at all. After all, going from a set of stock 15" thick aluminum rims to a set of aftermarket, sporty 18's, there might not be any weight difference. But if there is, where is the weight? Center of the wheel? Outside? Makes a difference. If the extra weight is in the center, there will be zero to almost zero difference...they might even be quicker.
Now, one final factor in this theorectical drag test is tire diameter. If you decide to keep the same tire profile with the 18's, that will require a taller tire....which will change your gear ratio and will affect the acceleration more than a few lbs of unsprung wheel weight will.
The rest of the post I agree with totally, but as I said before, in the case of the OP's sister just wondering what effect larger rims will have on her stock girly-mobile, there will be zero to almost zero effect. So I recommend she just get whatever rims she likes the look of better, and can afford to put tires on later.
Maybe you should re-read it? Lots of good and correct points I made in there. I really wasn't trying to refute what you wrote, moreso I was expounding on it...mentioning other variables.
Until the big rims crack on a pothole, or she has to pay $$$ for new tires, or they get stolen.
Although I guess if it's a stock option, the first and last scenario isn't as likely.
zerocool84
Lifer
- Nov 11, 2004
- 36,041
- 472
- 126
Also more likely to scrub the big novelty rims on a curb.
If it is even a question, then they are undesirable which is true for the overwhelming vast majority of both road and off-road vehicles. Personally, I think the fad was stupid and the fact that they are now OEM options says it is no longer trendy (i.e. it may be the common fashion but is no longer fashionable). But in any case it's really dumb to degrade functionality in favor of form, as said.
If it is even a question, then they are undesirable which is true for the overwhelming vast majority of both road and off-road vehicles. Personally, I think the fad was stupid and the fact that they are now OEM options says it is no longer trendy (i.e. it may be the common fashion but is no longer fashionable). But in any case it's really dumb to degrade functionality in favor of form, as said.
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