Bigger Rims = Bad gas mileage??
08-28-2005, 04:38 AM
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Bigger Rims = Bad gas mileage??
I was told that bigger rims means bad mileage. How true is that and why is that? My last questions would be: What is the best size rims for tC, 18 or 19? Thanks
08-28-2005, 04:46 AM
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the larger the wheel, the larger the contact patch is with the ground. you are also increasing the rotating mass on the corners. it takes more to spin 60lbs of wheels then it does 30 lbs.. same with braking.. you will see less life from you brakes since it takes more force to stop 60lbs of spinning mass.
08-28-2005, 06:08 AM
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I've heard that size does matter..... when it comes to gas mileage.
But as for the best size for the tC.... I have the stock 18s and ive seen 19s, they both look equally as good. 19s look hot with a 2in drop... but with if you hit a good size bumper, you'll have some rubbing.
But as for the best size for the tC.... I have the stock 18s and ive seen 19s, they both look equally as good. 19s look hot with a 2in drop... but with if you hit a good size bumper, you'll have some rubbing.
08-28-2005, 06:23 AM
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HEAVIER CARS = WORSE GAS MILEAGE
no matter wat car. the heavier it is, the worse the gas mileage will be.
if you get bigger rims and they happen to be heavier, then your mileage will worsen
no matter wat car. the heavier it is, the worse the gas mileage will be.
if you get bigger rims and they happen to be heavier, then your mileage will worsen
08-28-2005, 08:18 AM
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There's a lot of bad info on here, so I'm gonna try to straighten out some of it. . . I wish someone would make a sticky of it already. I hate reposting the same information, arguing about it, and then coming to the same conclusion.
Rotational Inertia: a wheels resistance to changes in speed (acceleration or deceleration). THe more inertia, the worse MPG, worse braking, worse HP.
I=MRR (that's M times (Rsquared))
As you can see, weight is not as important as radius. Inertia increases by the SQUARE or radius. Therefore, mass is the LEAST of your concerns.
a 5% increase in mass has a 5% increase in inertia. A 5% increase in size has the square's increase in inertia.
Thus reducing your wheel size by 5% is far more effective than lightening them by 5%, and in the real world, reducing the size decreases the weight as well.
SO
Increasing size will always hurt performance, in almost every regard. It takes a larger decrease in weight than %increase in size to offset the performance difference. So even if the bigger wheel is lighter, it is probably a worse performer.
REMEMBER
That this applies to wheels of equal width and overall diameter, and tires of equal traction. Of course, if you get wider tires, you will have more traction (if the width you already have does not match traction limit). When comparing performance, you need to compare tires of equal performance (not econo vs performance slicks)! More often than not, there are performance alternative tires of smaller diameters, with stiff sidewalls.
Just because you gain sidwall stiffness with larger diameters does not necessarily mean faster track times. In several independent tests, the ruled the opposite. Larger=slower. The offset in traction did not offset the loss in acceleration and braking.
If handling G's are your goal, than stiffer sidewalls are critical, however. And styling, of course! But remember that you pay a price in MPG, HP, and braking.
Rotational Inertia: a wheels resistance to changes in speed (acceleration or deceleration). THe more inertia, the worse MPG, worse braking, worse HP.
I=MRR (that's M times (Rsquared))
As you can see, weight is not as important as radius. Inertia increases by the SQUARE or radius. Therefore, mass is the LEAST of your concerns.
a 5% increase in mass has a 5% increase in inertia. A 5% increase in size has the square's increase in inertia.
Thus reducing your wheel size by 5% is far more effective than lightening them by 5%, and in the real world, reducing the size decreases the weight as well.
SO
Increasing size will always hurt performance, in almost every regard. It takes a larger decrease in weight than %increase in size to offset the performance difference. So even if the bigger wheel is lighter, it is probably a worse performer.
REMEMBER
That this applies to wheels of equal width and overall diameter, and tires of equal traction. Of course, if you get wider tires, you will have more traction (if the width you already have does not match traction limit). When comparing performance, you need to compare tires of equal performance (not econo vs performance slicks)! More often than not, there are performance alternative tires of smaller diameters, with stiff sidewalls.
Just because you gain sidwall stiffness with larger diameters does not necessarily mean faster track times. In several independent tests, the ruled the opposite. Larger=slower. The offset in traction did not offset the loss in acceleration and braking.
If handling G's are your goal, than stiffer sidewalls are critical, however. And styling, of course! But remember that you pay a price in MPG, HP, and braking.
08-29-2005, 03:41 PM
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I don't see what the big deal is. You more than likely are not going to even NOTICE a change in your MPG. You have to take into account that with your stock wheels, the sidewall height of the tire is larger than on a larger rim. If you were to sit both tires side by side, you will probably notice that the OVERALL height of the tire+rim is about nearly the same. Stock = Smaller wheel and thicker tire. Aftermarket = Larger Wheel (perhaps lighter in some cases) and skinner tire. If you want to Track it up all the time, then you probably will benefit from a smaller wheel thicker tire setup better. But If you are looking for asthetic value, then I say go with 18's or 19's (19's seem to be the formula for the TC IMO). By your question, it dosen't seem you are looking for the best Performace, but are more concerned with your gas. Dude, seriously, you probably won't even think of MPG, because you will be to busy looking at how good your TC looks drop on a set of 19's.
08-29-2005, 03:58 PM
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Originally Posted by rhythmnsmoke
I don't see what the big deal is. You more than likely are not going to even NOTICE a change in your MPG. You have to take into account that with your stock wheels, the sidewall height of the tire is larger than on a larger rim. If you were to sit both tires side by side, you will probably notice that the OVERALL height of the tire+rim is about nearly the same. Stock = Smaller wheel and thicker tire. Aftermarket = Larger Wheel (perhaps lighter in some cases) and skinner tire. If you want to Track it up all the time, then you probably will benefit from a smaller wheel thicker tire setup better. But If you are looking for asthetic value, then I say go with 18's or 19's (19's seem to be the formula for the TC IMO). By your question, it dosen't seem you are looking for the best Performace, but are more concerned with your gas. Dude, seriously, you probably won't even think of MPG, because you will be to busy looking at how good your TC looks drop on a set of 19's.
08-29-2005, 04:06 PM
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Most of us making a big deal are just answering his question. But as I previously stated, larger rims are for aesthetic value. You will lose a substantial amount of power and MPG
Thank ya.. I wasnt trying to get into the whole physics of larger wheels/moving the rotating mass away from the center of the hub/blah blah.. just a quick yes answer. djct knows whats up. just do some websearches.
Thank ya.. I wasnt trying to get into the whole physics of larger wheels/moving the rotating mass away from the center of the hub/blah blah.. just a quick yes answer. djct knows whats up. just do some websearches.
08-29-2005, 04:08 PM
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Originally Posted by djct_watt
Most of us making a big deal are just answering his question. But as I previously stated, larger rims are for aesthetic value. You will lose a substantial amount of power and MPG. Just try racing two identical cars, one with 19's and one with 17's. It's been done time and time again with different cars (this doesn't count ricer boys who flat with lame cameras). Aesthetically, larger rims can look really good. . . And then there's always super dub 28" spinning rims. It's all personal taste, but it's best that people know what they are getting into before they make a large purchase.
I will just offset the "power loss" by installing a ZPI turbo...lol. And MPG...well, aftermarket = loss of MPG.
08-29-2005, 05:20 PM
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actually, lighter 17" rims and a drop will increase your MPG. . .
but kudos for the ZPI turbo. . . when you run that thing on the track, switch back to your stockies or some lighter performance rims. I bet it'll be one clean car.
but kudos for the ZPI turbo. . . when you run that thing on the track, switch back to your stockies or some lighter performance rims. I bet it'll be one clean car.
08-29-2005, 05:36 PM
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Originally Posted by djct_watt
There's a lot of bad info on here, so I'm gonna try to straighten out some of it. . . I wish someone would make a sticky of it already. I hate reposting the same information, arguing about it, and then coming to the same conclusion.
Rotational Inertia: a wheels resistance to changes in speed (acceleration or deceleration). THe more inertia, the worse MPG, worse braking, worse HP.
I=MRR (that's M times (Rsquared))
As you can see, weight is not as important as radius. Inertia increases by the SQUARE or radius. Therefore, mass is the LEAST of your concerns.
a 5% increase in mass has a 5% increase in inertia. A 5% increase in size has the square's increase in inertia.
Thus reducing your wheel size by 5% is far more effective than lightening them by 5%, and in the real world, reducing the size decreases the weight as well.
SO
Increasing size will always hurt performance, in almost every regard. It takes a larger decrease in weight than %increase in size to offset the performance difference. So even if the bigger wheel is lighter, it is probably a worse performer.
REMEMBER
That this applies to wheels of equal width and overall diameter, and tires of equal traction. Of course, if you get wider tires, you will have more traction (if the width you already have does not match traction limit). When comparing performance, you need to compare tires of equal performance (not econo vs performance slicks)! More often than not, there are performance alternative tires of smaller diameters, with stiff sidewalls.
Just because you gain sidwall stiffness with larger diameters does not necessarily mean faster track times. In several independent tests, the ruled the opposite. Larger=slower. The offset in traction did not offset the loss in acceleration and braking.
If handling G's are your goal, than stiffer sidewalls are critical, however. And styling, of course! But remember that you pay a price in MPG, HP, and braking.
Rotational Inertia: a wheels resistance to changes in speed (acceleration or deceleration). THe more inertia, the worse MPG, worse braking, worse HP.
I=MRR (that's M times (Rsquared))
As you can see, weight is not as important as radius. Inertia increases by the SQUARE or radius. Therefore, mass is the LEAST of your concerns.
a 5% increase in mass has a 5% increase in inertia. A 5% increase in size has the square's increase in inertia.
Thus reducing your wheel size by 5% is far more effective than lightening them by 5%, and in the real world, reducing the size decreases the weight as well.
SO
Increasing size will always hurt performance, in almost every regard. It takes a larger decrease in weight than %increase in size to offset the performance difference. So even if the bigger wheel is lighter, it is probably a worse performer.
REMEMBER
That this applies to wheels of equal width and overall diameter, and tires of equal traction. Of course, if you get wider tires, you will have more traction (if the width you already have does not match traction limit). When comparing performance, you need to compare tires of equal performance (not econo vs performance slicks)! More often than not, there are performance alternative tires of smaller diameters, with stiff sidewalls.
Just because you gain sidwall stiffness with larger diameters does not necessarily mean faster track times. In several independent tests, the ruled the opposite. Larger=slower. The offset in traction did not offset the loss in acceleration and braking.
If handling G's are your goal, than stiffer sidewalls are critical, however. And styling, of course! But remember that you pay a price in MPG, HP, and braking.
Nice post bro. That is all I will say as a reply
08-29-2005, 05:45 PM
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He is right about the rotational iniertia. When anyone increases the actual metal rim bigger, the increase in inertia is squared like he said. Even if the tires are the same size as the previous tires, they do not weigh as much as the actual metal rim. Even if the rim is slightly lighter the rotational inertia will probably still be increased. Anyways this brings me to the point that most race cars use the smallest diameter wheels that fit there brakes for a reason. So there will be an effect on gas milage. also for the best sized rims depends on what you want to do. If you like the looks of bigger rims then 19's are in order but for gas milage the best would be a 15 inch rims (if you can fit it) with a low rolling resistance tire. And for performance a 15 inch rim again with a racing tire is in order but for a street tire i would probably stick with the stock rims and better tires. anyways my 2 cents.
08-29-2005, 06:02 PM
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A big part of the problem (especially with the xA and xB) are the tiny little engines. If you have a big, powerful V-8 and you upsize the wheels, you will never notice the drop in power or gas milage. But when you only have a little 108 HP 4 cylinder, it doesn't take much to notice a change. If you slap a set of heavy 19" chrome wheels on a xB, you are going to get crappy milage and have no power....but you'll look good.
