Wider tires w/Drop Possible?
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RE: Wider tires w/Drop Possible?
Damn, I know I insult people sometimes, but it's not like Moog was trying to make claims when he had no idea what he was talking about (generally the only time I bash people). He was genuinely asking questions about concepts he didn't understand. That doesn't warrant talking down to.
HCF Member
Joined: Jul 2005
Posts: 7,994
From: Rochester, NY
RE: Wider tires w/Drop Possible?
ORIGINAL: amg6975
Actually, I was always under the impression that the sidewall of a tire is heavier than most rim spokes over the same surface area. The catch is the metal ring around the outside of the rim is the heaviest part of a wheel/tire combo so you want to bring as close to the center of the wheel as possable so you don't have to accelerate it as far. I could be wrong though, that was just how I thought about the small rim vs. big rim argument.
I guess if the wheel spokes were lighter there's another argument for getting smaller rims!
And remember wheel weight is HUGE... you have to accelerate it forwards with the car AND around the axis of rotation. It also affects turn in performance... things that are rotating don't want to change direction easy so the lighter they are the less resistance they have to change. (Most people agree the turn in thing really doesn't matter though.)
Actually, I was always under the impression that the sidewall of a tire is heavier than most rim spokes over the same surface area. The catch is the metal ring around the outside of the rim is the heaviest part of a wheel/tire combo so you want to bring as close to the center of the wheel as possable so you don't have to accelerate it as far. I could be wrong though, that was just how I thought about the small rim vs. big rim argument.
I guess if the wheel spokes were lighter there's another argument for getting smaller rims!
And remember wheel weight is HUGE... you have to accelerate it forwards with the car AND around the axis of rotation. It also affects turn in performance... things that are rotating don't want to change direction easy so the lighter they are the less resistance they have to change. (Most people agree the turn in thing really doesn't matter though.)
plus the fact that larger diameter rims are usually wider, so more mass there too.
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RE: Wider tires w/Drop Possible?
Well, it's all about moment of inertia. It plays the same role for circular motion as weight (strictly speaking – mass) - for linear motion. Calculation for the case of wheel would be rather tedious; suffice it to say that wheel’s moment of inertia is proportional to its mass and to the square of the distance between the heaviest profile point (profile's or radial cut's center of mass, to be precise) and the center of revolution. Hence, if your goal is pure acceleration, you want as small rim as possible for a given outside tire diameter. You get terrible handling, though, because tire walls are very soft compared to rim.
Bottom line: want better acceleration – decrease rim size, better handling – increase.
And – No, you cannot have your cake and eat it, too.
Bottom line: want better acceleration – decrease rim size, better handling – increase.
And – No, you cannot have your cake and eat it, too.
HCF Member
Joined: Aug 2005
Posts: 2,821
From: Rochester, NY
RE: Wider tires w/Drop Possible?
ORIGINAL: Misha
Well, it's all about moment of inertia. It plays the same role for circular motion as weight (strictly speaking – mass) - for linear motion. Calculation for the case of wheel would be rather tedious; suffice it to say that wheel’s moment of inertia is proportional to its mass and to the square of the distance between the heaviest profile point (profile's or radial cut's center of mass, to be precise) and the center of revolution. Hence, if your goal is pure acceleration, you want as small rim as possible for a given outside tire diameter. You get terrible handling, though, because tire walls are very soft compared to rim.
Bottom line: want better acceleration – decrease rim size, better handling – increase.
And – No, you cannot have your cake and eat it, too.
Well, it's all about moment of inertia. It plays the same role for circular motion as weight (strictly speaking – mass) - for linear motion. Calculation for the case of wheel would be rather tedious; suffice it to say that wheel’s moment of inertia is proportional to its mass and to the square of the distance between the heaviest profile point (profile's or radial cut's center of mass, to be precise) and the center of revolution. Hence, if your goal is pure acceleration, you want as small rim as possible for a given outside tire diameter. You get terrible handling, though, because tire walls are very soft compared to rim.
Bottom line: want better acceleration – decrease rim size, better handling – increase.
And – No, you cannot have your cake and eat it, too.
HCF Member
Joined: Jul 2005
Posts: 7,994
From: Rochester, NY
RE: Wider tires w/Drop Possible?
ORIGINAL: Misha
Bottom line: want better acceleration – decrease rim size, better handling – increase.
And – No, you cannot have your cake and eat it, too.
Bottom line: want better acceleration – decrease rim size, better handling – increase.
And – No, you cannot have your cake and eat it, too.
HCF Member
Joined: Jul 2005
Posts: 7,994
From: Rochester, NY
RE: Wider tires w/Drop Possible?
ORIGINAL: amg6975
wheel weight . . . also affects turn in performance... things that are rotating don't want to change direction easy so the lighter they are the less resistance they have to change. (Most people agree the turn in thing really doesn't matter though.)
wheel weight . . . also affects turn in performance... things that are rotating don't want to change direction easy so the lighter they are the less resistance they have to change. (Most people agree the turn in thing really doesn't matter though.)
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RE: Wider tires w/Drop Possible?
ORIGINAL: mxs
sure you can. increase rim width, decrease rim diameter, decrease rim weight......... decrease weight of wallet, lol. this is why I'm looking at 15x7 wheels for race tires next season. hell, some people run 15x8 (I think) for race tires.
sure you can. increase rim width, decrease rim diameter, decrease rim weight......... decrease weight of wallet, lol. this is why I'm looking at 15x7 wheels for race tires next season. hell, some people run 15x8 (I think) for race tires.
ORIGINAL: amg6975
All you have to do is get some stiff racing or R-compound tires and pump them up a bunch and you're fine. Why would autocrossers use the smallest possable wheel if they made the car handle terrible?
All you have to do is get some stiff racing or R-compound tires and pump them up a bunch and you're fine. Why would autocrossers use the smallest possable wheel if they made the car handle terrible?
Can you read the post in its entirety? You were asking for engineering opinion, I gave you one. All this was assuming
ORIGINAL: Misha
a given outside tire diameter.
a given outside tire diameter.
Changing an outside tire diameter is altogether different animal and introduces a bunch of other problems to deal with. Go up, and you hurt your acceleration, go down, and you hurt your mileage. And you hurt your speedometer accuracy either way. May be other things, too, those just came to mind first.
HCF Member
Joined: Jul 2005
Posts: 7,994
From: Rochester, NY
RE: Wider tires w/Drop Possible?
ORIGINAL: Misha
.
.
Can you read the post in its entirety? You were asking for engineering opinion, I gave you one. All this was assuming
. For those who cannot read, this means you are using higher profile tire if you decrease rim size, and lower profile tire if you increase it, and you keep your outside tire diameter constant.
Changing an outside tire diameter is altogether different animal and introduces a bunch of other problems to deal with. Go up, and you hurt your acceleration, go down, and you hurt your mileage. And you hurt your speedometer accuracy either way. May be other things, too, those just came to mind first.
ORIGINAL: mxs
sure you can. increase rim width, decrease rim diameter, decrease rim weight......... decrease weight of wallet, lol. this is why I'm looking at 15x7 wheels for race tires next season. hell, some people run 15x8 (I think) for race tires.
sure you can. increase rim width, decrease rim diameter, decrease rim weight......... decrease weight of wallet, lol. this is why I'm looking at 15x7 wheels for race tires next season. hell, some people run 15x8 (I think) for race tires.
ORIGINAL: amg6975
All you have to do is get some stiff racing or R-compound tires and pump them up a bunch and you're fine. Why would autocrossers use the smallest possable wheel if they made the car handle terrible?
All you have to do is get some stiff racing or R-compound tires and pump them up a bunch and you're fine. Why would autocrossers use the smallest possable wheel if they made the car handle terrible?
Can you read the post in its entirety? You were asking for engineering opinion, I gave you one. All this was assuming
ORIGINAL: Misha
a given outside tire diameter.
a given outside tire diameter.
Changing an outside tire diameter is altogether different animal and introduces a bunch of other problems to deal with. Go up, and you hurt your acceleration, go down, and you hurt your mileage. And you hurt your speedometer accuracy either way. May be other things, too, those just came to mind first.
I was not talking about changing overall tire diameter. wheel diameter yes, overall tire diameter no.
Don't come in here with 49 posts and accuse moerators/admins of not being able to read...
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RE: Wider tires w/Drop Possible?
ORIGINAL: mxs
No, I was not asking for an "engineering opinion,"
No, I was not asking for an "engineering opinion,"
ORIGINAL: mxs
fine, I'll leave it to the engineer to explain it better than me . . . plus the fact that larger diameter rims are usually wider, so more mass there too.
fine, I'll leave it to the engineer to explain it better than me . . .
plus the fact that larger diameter rims are usually wider, so more mass there too.
ORIGINAL: mxs
I was responding to amg6975 and his post.
I was responding to amg6975 and his post.
ORIGINAL: mxs
sure you can. increase rim width, decrease rim diameter, decrease rim weight......... decrease weight of wallet, lol. this is why I'm looking at 15x7 wheels for race tires next season. hell, some people run 15x8 (I think) for race tires.
ORIGINAL: Misha
Bottom line: want better acceleration – decrease rim size, better handling – increase.
And – No, you cannot have your cake and eat it, too.
Bottom line: want better acceleration – decrease rim size, better handling – increase.
And – No, you cannot have your cake and eat it, too.
Surprisingly, your post looks pretty much like an answer to mine Probably my bad English, again
ORIGINAL: mxs
I was not talking about changing overall tire diameter. wheel diameter yes, overall tire diameter no.
I was not talking about changing overall tire diameter. wheel diameter yes, overall tire diameter no.
ORIGINAL: mxs
Don't come in here with 49 posts and accuse moerators/admins of not being able to read...
Don't come in here with 49 posts and accuse moerators/admins of not being able to read...
EDIT: OOPS I just realised I did acuse you of not being able to read. Bad wording, I apologize. I meant "those who did not want to read or did not understand"...
HCF Member
Joined: Jul 2005
Posts: 7,994
From: Rochester, NY
RE: Wider tires w/Drop Possible?
when I say "overall diameter" that's the same as the "outside diameter", the diameter of the tire
I don't have a problem, but when you go around saying things like " for those of you who can't read", that is considered rude
also, I'm not a man. and I still disagree with your comment about smaller rims = bad handling.
I don't have a problem, but when you go around saying things like " for those of you who can't read", that is considered rude
also, I'm not a man. and I still disagree with your comment about smaller rims = bad handling.