Does rim size matter?
Hi all, I want to know if rim size or tire size matters when it comes to performance. For example is there really a differences for lude cars having 15 or 18 inch rims?
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From: Off THE 60, Between THE 605 and THE 57
rim size is correlated to rim weight so if you're rockin 18's and didn't spend 3 grand on them, chances are they weigh over 20 lbs, which in turn makes your engine work harder to get em spinning, which in turn makes you slower.
on the flip side, if you've got big rims, it means you've got low profile tires, which have less sidewall flex and are generally better for handling under most conditions, because it means the car "rolls" less under hard cornering.
Bigger tires mean a bigger contact patch which mean more available traction for acceleration, braking, and cornering, but bigger tires take longer to warm up, and when you get to a certain point, too wide is overdoing it. 225 i think is the upper limit for practical tire sizes in a lude.
There are other factors in this equation that other people are more qualified to elaborate upon, but the key i think is a balance. I think an ideal size for a performance minded lude is 15x7 or 16x7.5. If you go to an SCCA event, no one is ever running anything bigger than 16", and lots of miatas are running 14's on fatty slicks.
on the flip side, if you've got big rims, it means you've got low profile tires, which have less sidewall flex and are generally better for handling under most conditions, because it means the car "rolls" less under hard cornering.
Bigger tires mean a bigger contact patch which mean more available traction for acceleration, braking, and cornering, but bigger tires take longer to warm up, and when you get to a certain point, too wide is overdoing it. 225 i think is the upper limit for practical tire sizes in a lude.
There are other factors in this equation that other people are more qualified to elaborate upon, but the key i think is a balance. I think an ideal size for a performance minded lude is 15x7 or 16x7.5. If you go to an SCCA event, no one is ever running anything bigger than 16", and lots of miatas are running 14's on fatty slicks.
good info bad monkey....Hey, i'm currently running 215/45/17 on 17x7.5inch volks, do you think i could run the Nitto555 in 225-40-17 without issues?its the only decent tire i've found in that size....i actually noticed the JUN project lude has 225's in front and 215 in back...
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From: Off THE 60, Between THE 605 and THE 57
i think you could run 225's without rubbing. I think your offset might come into play as well as some other things, but for the most part, i think it'll be fine...
there's other tires in a 225/40/17 though...i think the yoko AVS ES 100 and the Eagle F1 DS are a couple...
i'm not a big fan of nitto.
there's other tires in a 225/40/17 though...i think the yoko AVS ES 100 and the Eagle F1 DS are a couple...
i'm not a big fan of nitto.
That should be fine unless youre really low. I'm going to be running 225/35/18 when I get my car back and they were close to rubbing but I was riding on Sportlines with blown struts. If you have a decent drop it should be ok. This is all assuming you got a decent offset.
BTW, I am a very performance minded person for the most part, but with all these hesitation problems I've been having I decided to fix up the exterior. That way when I drive and get all pissed cause of the hesitation, I just get out and stare at it and be happy again, lol. The 18s weigh 18lbs by the way.
BTW, I am a very performance minded person for the most part, but with all these hesitation problems I've been having I decided to fix up the exterior. That way when I drive and get all pissed cause of the hesitation, I just get out and stare at it and be happy again, lol. The 18s weigh 18lbs by the way.
The general rule for performance is get the smallest/lightest diameter that will fit over your brakes, and the widest width your can run. (Ie 15x7 or 16x7.5)
18" are for show really.
18" are for show really.
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From: Off THE 60, Between THE 605 and THE 57
well, i'm buying new wheels this week for rollin around town (17x7) and keeping my stock wheels for race day.
and every second counts, whether it's at the strip or arund the cones!
and every second counts, whether it's at the strip or arund the cones!
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">So you wouldn't sacrifice some 0.034 secs for a better look?</TD></TR></TABLE>
Yup!! Performance > looks in my book. And who said 15s or 16s look bad in the 1st place? But that's just me
Yup!! Performance > looks in my book. And who said 15s or 16s look bad in the 1st place? But that's just me

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by -743- »</TD></TR><TR><TD CLASS="quote">It's all about the 14s.</TD></TR></TABLE>
my first car (86 Accord LXI HB) rolled on 13's (steelies!)....BEEOTCH!!
PS: I have been having this same dilemma...I want nice looking Rims but I want them to be light + not sacrifice acceleration AND I want them to have the closest to stock offset possible (+55). Sooo I am considering sticking w/the stock 15in sawblades which are like 15-17lbs I think & MAYBE Powder-coating or painting them.
This is what I don't get.....lets say my stockers are 15in and 16lbs + the weight of the tire rubber. Lets say I get some ROTAs that are 17s But weigh 15lbs w/LOW PROFILE Rubber...wouldn't that weight about the same as the stock combo or LESS ?!?!?!
ALSO the overall size of the wheel/tire combo should be nearly identical w/17's and low-pros....so where does this problem w/performance come into play? If they were 20+ lb rims then I understand but what if they are about as heavy as the the stock 15's?
Am I missing something? I was never a physics wiz...
my first car (86 Accord LXI HB) rolled on 13's (steelies!)....BEEOTCH!!
PS: I have been having this same dilemma...I want nice looking Rims but I want them to be light + not sacrifice acceleration AND I want them to have the closest to stock offset possible (+55). Sooo I am considering sticking w/the stock 15in sawblades which are like 15-17lbs I think & MAYBE Powder-coating or painting them.
This is what I don't get.....lets say my stockers are 15in and 16lbs + the weight of the tire rubber. Lets say I get some ROTAs that are 17s But weigh 15lbs w/LOW PROFILE Rubber...wouldn't that weight about the same as the stock combo or LESS ?!?!?!
ALSO the overall size of the wheel/tire combo should be nearly identical w/17's and low-pros....so where does this problem w/performance come into play? If they were 20+ lb rims then I understand but what if they are about as heavy as the the stock 15's?
Am I missing something? I was never a physics wiz...
A small difference in unsprung weight (brakes, tires, rims, any weight on the vehicle not supported by, but not including a certain percentage of, the suspension) can make a huge difference in the acceleration and braking characteristics of your vehicle.
Any advantage gained in the increased contact patch from the larger rim/tire would be lost there as well if the unsprung weight differs by even a few lbs. The higher the unsprung weight, the less responsively the car will handle, the less stable it will be, and the harder it is for the suspension to maintain contact and traction with the road, especially on bumpy or uneven surfaces.
"So what if it's only a few pounds?!?" you say, well let's examine that. It was once said that 1 lb of unsprung weight= 8 lbs of sprung weight (don't quote me directly, I'm using someone else's equations, some quote that # as high as 10 lbs!), so if each aftermarket rim weighs only 6 lbs each more than the original equipment (6 lbs unsprung weight x 8 lbs theoretical sprung weight increase x 4 wheels = 192 lbs) you have changed your power-to-weight ratio as much as if you'd just lost 11 whp. No, the formula and the relationship aren't that simple, but think about that for a second. In increasing the weight of the car's unsupported rotational mass you functionally reduce usable whp.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LudeBoyLeRoy »</TD></TR><TR><TD CLASS="quote">ALSO the overall size of the wheel/tire combo should be nearly identical w/17's and low-pros....so where does this problem w/performance come into play? If they were 20+ lb rims then I understand but what if they are about as heavy as the the stock 15's?</TD></TR></TABLE>
First, when you increase the wheel diameter, regardless of it's weight, you always increase the weight of the wheel/tire combo. Why? Let me explain: In order to keep the same overall diameter, the tires must be smaller profile and therefore heavier due to the increased stiffness needed in the sidewalls. This is true even if the tires are the same width. The mere fact that it is shorter means that it will be stiffer, even with the same construction. That is the whole point of lower aspect ratio tires. The sidewall must be constructed stiffer because it is smaller. Otherwise, the rims would contact the ground much more easily when hitting a hole or during aggressive cornering. It is kind of weird to think that a smaller sidewall tire is heavier, but that's how it is, for the most part anyway.
And it's not just the height of the tire from top to bottom, it's the rolling circumference of the tire on the new larger rim that matters. Larger tires give you taller gearing (you can caluculate the % of the increase by dividing the diameter of the new tire by that of the old), which decreases acceleration, especially on smaller displacement engines, decreases revs at cruising speed, and limits your top speed.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Odessa »</TD></TR><TR><TD CLASS="quote">So you wouldn't sacrifice some 0.034 secs for a better look?
</TD></TR></TABLE>
A set of 18" Ro_ja's on low-profile tires will cost you the equivalent of over 25 whp and a lot more in the 1/4 than a couple of hundredths of a second; on a 3000 lb car that's like going from running a 15.4 to running a 16.3. Bling bling...
Modified by Final Flash at 2:59 AM 8/8/2003
Any advantage gained in the increased contact patch from the larger rim/tire would be lost there as well if the unsprung weight differs by even a few lbs. The higher the unsprung weight, the less responsively the car will handle, the less stable it will be, and the harder it is for the suspension to maintain contact and traction with the road, especially on bumpy or uneven surfaces.
"So what if it's only a few pounds?!?" you say, well let's examine that. It was once said that 1 lb of unsprung weight= 8 lbs of sprung weight (don't quote me directly, I'm using someone else's equations, some quote that # as high as 10 lbs!), so if each aftermarket rim weighs only 6 lbs each more than the original equipment (6 lbs unsprung weight x 8 lbs theoretical sprung weight increase x 4 wheels = 192 lbs) you have changed your power-to-weight ratio as much as if you'd just lost 11 whp. No, the formula and the relationship aren't that simple, but think about that for a second. In increasing the weight of the car's unsupported rotational mass you functionally reduce usable whp.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LudeBoyLeRoy »</TD></TR><TR><TD CLASS="quote">ALSO the overall size of the wheel/tire combo should be nearly identical w/17's and low-pros....so where does this problem w/performance come into play? If they were 20+ lb rims then I understand but what if they are about as heavy as the the stock 15's?</TD></TR></TABLE>
First, when you increase the wheel diameter, regardless of it's weight, you always increase the weight of the wheel/tire combo. Why? Let me explain: In order to keep the same overall diameter, the tires must be smaller profile and therefore heavier due to the increased stiffness needed in the sidewalls. This is true even if the tires are the same width. The mere fact that it is shorter means that it will be stiffer, even with the same construction. That is the whole point of lower aspect ratio tires. The sidewall must be constructed stiffer because it is smaller. Otherwise, the rims would contact the ground much more easily when hitting a hole or during aggressive cornering. It is kind of weird to think that a smaller sidewall tire is heavier, but that's how it is, for the most part anyway.
And it's not just the height of the tire from top to bottom, it's the rolling circumference of the tire on the new larger rim that matters. Larger tires give you taller gearing (you can caluculate the % of the increase by dividing the diameter of the new tire by that of the old), which decreases acceleration, especially on smaller displacement engines, decreases revs at cruising speed, and limits your top speed.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Odessa »</TD></TR><TR><TD CLASS="quote">So you wouldn't sacrifice some 0.034 secs for a better look?
</TD></TR></TABLE>A set of 18" Ro_ja's on low-profile tires will cost you the equivalent of over 25 whp and a lot more in the 1/4 than a couple of hundredths of a second; on a 3000 lb car that's like going from running a 15.4 to running a 16.3. Bling bling...
Modified by Final Flash at 2:59 AM 8/8/2003
WOW thanks for all the Info FLASH...sorry for the late response....
The only part I don't understand is this:
"And it's not just the height of the tire from top to bottom, it's the rolling circumference of the tire on the new larger rim that matters. Larger tires give you taller gearing (you can caluculate the % of the increase by dividing the diameter of the new tire by that of the old), which decreases acceleration, especially on smaller displacement engines, decreases revs at cruising speed, and limits your top speed."
So Let me get this straight....isn't the Tire Circumference the same whether its a 15in rim w/205 55's or 17's with whatever the low-pros would be? So then the only diff between stock would be the weight, right?
So if got a 17 rim/tire package and weighed it vs. the stock combo...if they are the same weight then I would have no performance loss, right?
And how about this....if I got 15x6.5's or 15x7's (slightly more rubber) that were 3 to 5lbs lighter than the stock rims I should see a performance increase (better acceloration + braking) Right?? Can you calculate the gain for me?
Thanks FLASH!
The only part I don't understand is this:
"And it's not just the height of the tire from top to bottom, it's the rolling circumference of the tire on the new larger rim that matters. Larger tires give you taller gearing (you can caluculate the % of the increase by dividing the diameter of the new tire by that of the old), which decreases acceleration, especially on smaller displacement engines, decreases revs at cruising speed, and limits your top speed."
So Let me get this straight....isn't the Tire Circumference the same whether its a 15in rim w/205 55's or 17's with whatever the low-pros would be? So then the only diff between stock would be the weight, right?
So if got a 17 rim/tire package and weighed it vs. the stock combo...if they are the same weight then I would have no performance loss, right?
And how about this....if I got 15x6.5's or 15x7's (slightly more rubber) that were 3 to 5lbs lighter than the stock rims I should see a performance increase (better acceloration + braking) Right?? Can you calculate the gain for me?
Thanks FLASH!
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by daveslude »</TD></TR><TR><TD CLASS="quote">I found that 205/45/16 were the best for performance</TD></TR></TABLE>
how?
how?
Rim size change - tire size change. This may / will also affect the gearing. I'm sure the track ****** could tell you all about it. Major difference between 14" and 18".
im going to the drag strip tomorrow. i was running 17" rims last week. tomorrow ill run my stock blacks.... ill tell you guys my new numbers.
one of the factors last week. i didnt wanna **** up my low pro tires, so i wasnt launching at a reasonable RPM. the on thing you dont want to do is **** up a tire that costs $100. stick with the blacks or stock rims... like someone said earlier.... 18" rims are more for show. leave them at home when you do out and race.
one of the factors last week. i didnt wanna **** up my low pro tires, so i wasnt launching at a reasonable RPM. the on thing you dont want to do is **** up a tire that costs $100. stick with the blacks or stock rims... like someone said earlier.... 18" rims are more for show. leave them at home when you do out and race.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LudeBoyLeRoy »</TD></TR><TR><TD CLASS="quote">WOW thanks for all the Info FLASH...sorry for the late response....
The only part I don't understand is this:
"And it's not just the height of the tire from top to bottom, it's the rolling circumference of the tire on the new larger rim that matters. Larger tires give you taller gearing (you can caluculate the % of the increase by dividing the diameter of the new tire by that of the old), which decreases acceleration, especially on smaller displacement engines, decreases revs at cruising speed, and limits your top speed."
So Let me get this straight....isn't the Tire Circumference the same whether its a 15in rim w/205 55's or 17's with whatever the low-pros would be? So then the only diff between stock would be the weight, right?</TD></TR></TABLE>
Nope. Circumference is the distance around the OUTSIDE of a circle, therefore increasing the tire size, even with low-pros, would increase the rolling circumference and change the gearing higher.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">So if got a 17 rim/tire package and weighed it vs. the stock combo...if they are the same weight then I would have no performance loss, right?</TD></TR></TABLE>
If the new package weighed the same as the old, you would see no negative change in acceleration characteristics. But like I said before, if they are any larger your gearing would get taller and you would see a detrimental effect on your times.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">And how about this....if I got 15x6.5's or 15x7's (slightly more rubber) that were 3 to 5lbs lighter than the stock rims I should see a performance increase (better acceleration + braking) Right?? Can you calculate the gain for me?
</TD></TR></TABLE>
Any theoretical gain would depend on if the formula(s) used to calculate unsprung-sprung weight are correct. What I did to calculate whp loss/increase was to use the car's weight at 3000 lbs and whp as 160 as static values (it doesn't matter if the values are exact or not, just that you approximate close enough and always use those same values in your calculations; all you really want is the ratio, when you add/subtract the weight, the positive/negative change will be about the same even if you used 3100 & 155 or something else as the weight/whp) then come up with the power-to-weight ratio, then change the weight (w/the new rim/tire package) and determine what hp would need to be added to make the ratio the same as before.
So, let's say that your new wheel package weighs 5 lbs per wheel less than the old. Plugging that into the formula (IF 1 lb unsprung= 8 lbs sprung) the change would (THEORETICALLY) have the same effect as a 160 lb weight reduction, which would have just about the same effect as adding 8.4 whp.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">Thanks FLASH!
</TD></TR></TABLE>
No prob, there are tons of articles around that go further into the mathematical aspects and how they change the physics of the vehicle, but some of them are ******* confusing. There are some in layman's terms that will even help you calculate what your individual gear ratios will change to. It's interesting stuff, and the main reason why I'm going with 17" Volk GT-N's (when I ever get the cash).
The only part I don't understand is this:
"And it's not just the height of the tire from top to bottom, it's the rolling circumference of the tire on the new larger rim that matters. Larger tires give you taller gearing (you can caluculate the % of the increase by dividing the diameter of the new tire by that of the old), which decreases acceleration, especially on smaller displacement engines, decreases revs at cruising speed, and limits your top speed."
So Let me get this straight....isn't the Tire Circumference the same whether its a 15in rim w/205 55's or 17's with whatever the low-pros would be? So then the only diff between stock would be the weight, right?</TD></TR></TABLE>
Nope. Circumference is the distance around the OUTSIDE of a circle, therefore increasing the tire size, even with low-pros, would increase the rolling circumference and change the gearing higher.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">So if got a 17 rim/tire package and weighed it vs. the stock combo...if they are the same weight then I would have no performance loss, right?</TD></TR></TABLE>
If the new package weighed the same as the old, you would see no negative change in acceleration characteristics. But like I said before, if they are any larger your gearing would get taller and you would see a detrimental effect on your times.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">And how about this....if I got 15x6.5's or 15x7's (slightly more rubber) that were 3 to 5lbs lighter than the stock rims I should see a performance increase (better acceleration + braking) Right?? Can you calculate the gain for me?
</TD></TR></TABLE>Any theoretical gain would depend on if the formula(s) used to calculate unsprung-sprung weight are correct. What I did to calculate whp loss/increase was to use the car's weight at 3000 lbs and whp as 160 as static values (it doesn't matter if the values are exact or not, just that you approximate close enough and always use those same values in your calculations; all you really want is the ratio, when you add/subtract the weight, the positive/negative change will be about the same even if you used 3100 & 155 or something else as the weight/whp) then come up with the power-to-weight ratio, then change the weight (w/the new rim/tire package) and determine what hp would need to be added to make the ratio the same as before.
So, let's say that your new wheel package weighs 5 lbs per wheel less than the old. Plugging that into the formula (IF 1 lb unsprung= 8 lbs sprung) the change would (THEORETICALLY) have the same effect as a 160 lb weight reduction, which would have just about the same effect as adding 8.4 whp.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">Thanks FLASH!
</TD></TR></TABLE>No prob, there are tons of articles around that go further into the mathematical aspects and how they change the physics of the vehicle, but some of them are ******* confusing. There are some in layman's terms that will even help you calculate what your individual gear ratios will change to. It's interesting stuff, and the main reason why I'm going with 17" Volk GT-N's (when I ever get the cash).
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Joined: Jun 2003
Posts: 9,633
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From: Off THE 60, Between THE 605 and THE 57
at auto-x today, i decided again, for the 100th time that bridgestone RE92s maybe the worst tire ever. slipping in the morning, slipping in the afternoon, screeching dying and slow...
anyway, i also found a connection for azenis-some guy can get 205/45/15's for 57 bucks a piece, so i'm going to shelve my OEM 16's, and use a set of OEM jeep wrangler 15's that i've got lying around (knew they'd be good for something and it's muuuuuuch cheaper than buying a set of slipstreams
). It sounds funny, but it's the 5spoke steel wheel and i'll be running em with no center caps, and only on track/course. thing is i'd really like to know how much they weigh, unfortunately those jeep guys seem to enjoy not knowing how much their wheels and 120lb tires weigh (and affect their performance) so i've got a mission for some of you internet snoops and a favor to ask: can someone track down the wheel weight of a 15x7" 5 spoke steel OEM jeep wheel

many millions of thanks in advance.
anyway, i also found a connection for azenis-some guy can get 205/45/15's for 57 bucks a piece, so i'm going to shelve my OEM 16's, and use a set of OEM jeep wrangler 15's that i've got lying around (knew they'd be good for something and it's muuuuuuch cheaper than buying a set of slipstreams
). It sounds funny, but it's the 5spoke steel wheel and i'll be running em with no center caps, and only on track/course. thing is i'd really like to know how much they weigh, unfortunately those jeep guys seem to enjoy not knowing how much their wheels and 120lb tires weigh (and affect their performance) so i've got a mission for some of you internet snoops and a favor to ask: can someone track down the wheel weight of a 15x7" 5 spoke steel OEM jeep wheel
many millions of thanks in advance.
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