View Poll Results: What size wheels do you have now?
Voters: 87. You may not vote on this poll
Do you have 17" or 18" wheels?
Registered User
iTrader: (14)
Joined: Sep 2004
Posts: 432
From: San Francisco, CA
Car Info: 13 BRZ Limited
Originally Posted by AntiochCali
Short answer, Yes you can.
Long answer, The problem is rotational mass and inertia - the farther from the center the mass is, the more energy it takes to overcome the mass affecting both positive and negative acceleration. Hence notice that most "racing wheels" have 50% or more of their mass at the most extreme distance from the center of the hub, because this mass must be here to cover the inside of the tire while the spokes get small. making the spokes smaller has less effect than making the wheel smaller. On steel wheels for example, only about 40% of the mass is where the tire meets the rim.
My 17" Rota Attacks weigh around 18 lbs they are faster than my stock 16" wheels weighing around 30 lbs, but they are not crazy faster because I have more rotational mass farther away from the center - but I can feel the difference.
This is also why a lightened flywheel gives better response to accelertion, rotational mass even though all you shed was 10 lbs, it's 10lbs the engine doesn't have to spin.
Long answer, The problem is rotational mass and inertia - the farther from the center the mass is, the more energy it takes to overcome the mass affecting both positive and negative acceleration. Hence notice that most "racing wheels" have 50% or more of their mass at the most extreme distance from the center of the hub, because this mass must be here to cover the inside of the tire while the spokes get small. making the spokes smaller has less effect than making the wheel smaller. On steel wheels for example, only about 40% of the mass is where the tire meets the rim.
My 17" Rota Attacks weigh around 18 lbs they are faster than my stock 16" wheels weighing around 30 lbs, but they are not crazy faster because I have more rotational mass farther away from the center - but I can feel the difference.
This is also why a lightened flywheel gives better response to accelertion, rotational mass even though all you shed was 10 lbs, it's 10lbs the engine doesn't have to spin.
Thread Starter
VIP Member
iTrader: (5)
Joined: Apr 2004
Posts: 3,674
From: El Cerrito, CA
Car Info: 2014 Mazda MX-5 GT PRHT
Originally Posted by AntiochCali
Short answer, Yes you can.
Long answer, The problem is rotational mass and inertia - the farther from the center the mass is, the more energy it takes to overcome the mass affecting both positive and negative acceleration. Hence notice that most "racing wheels" have 50% or more of their mass at the most extreme distance from the center of the hub, because this mass must be here to cover the inside of the tire while the spokes get small. making the spokes smaller has less effect than making the wheel smaller. On steel wheels for example, only about 40% of the mass is where the tire meets the rim.
My 17" Rota Attacks weigh around 18 lbs they are faster than my stock 16" wheels weighing around 30 lbs, but they are not crazy faster because I have more rotational mass farther away from the center - but I can feel the difference.
This is also why a lightened flywheel gives better response to accelertion, rotational mass even though all you shed was 10 lbs, it's 10lbs the engine doesn't have to spin.
Long answer, The problem is rotational mass and inertia - the farther from the center the mass is, the more energy it takes to overcome the mass affecting both positive and negative acceleration. Hence notice that most "racing wheels" have 50% or more of their mass at the most extreme distance from the center of the hub, because this mass must be here to cover the inside of the tire while the spokes get small. making the spokes smaller has less effect than making the wheel smaller. On steel wheels for example, only about 40% of the mass is where the tire meets the rim.
My 17" Rota Attacks weigh around 18 lbs they are faster than my stock 16" wheels weighing around 30 lbs, but they are not crazy faster because I have more rotational mass farther away from the center - but I can feel the difference.
This is also why a lightened flywheel gives better response to accelertion, rotational mass even though all you shed was 10 lbs, it's 10lbs the engine doesn't have to spin.
hmmm sounds good.. but still not convinced. in theory, I can see why that would make sense though. However... being that the tires have to match the diameter of the stockers, wouldn't that make the mass consistent to the formula? Rotational mass isn't really affected is it? I mean, unless the tire is wider... giving the tire more friction on the road. So having the tire being the same diameter as the stock one (something to do with the ECU and the differential?) the center of mass shouldn't be different because it's not changing the diameter of the lug patterns. in other words.. it's all the same, but the wheel is bigger and the tires are skinnier. make any sense? oh well
Thread Starter
VIP Member
iTrader: (5)
Joined: Apr 2004
Posts: 3,674
From: El Cerrito, CA
Car Info: 2014 Mazda MX-5 GT PRHT
Originally Posted by 1fastGC
18x9 +35mm offset 245/40/18 S03s
no rubbing at all.
no rubbing at all.
people always say there is rubbing when it comes to 40 and below.. how did you get away from that?
VIP Member
iTrader: (2)
Joined: May 2003
Posts: 4,219
From: out on the twisties
Car Info: WRB WRX 2003 Subaru Sedan
I really like the look of the 18's but i do far too much rally driving to have em. I need that extra side wall. So i have the 17's. Plus 18" tires cost too much
Registered User
iTrader: (14)
Joined: Sep 2004
Posts: 432
From: San Francisco, CA
Car Info: 13 BRZ Limited
Originally Posted by sireatalot
hmmm sounds good.. but still not convinced. in theory, I can see why that would make sense though. However... being that the tires have to match the diameter of the stockers, wouldn't that make the mass consistent to the formula? Rotational mass isn't really affected is it? I mean, unless the tire is wider... giving the tire more friction on the road. So having the tire being the same diameter as the stock one (something to do with the ECU and the differential?) the center of mass shouldn't be different because it's not changing the diameter of the lug patterns. in other words.. it's all the same, but the wheel is bigger and the tires are skinnier. make any sense? oh well
When I brought up unsprung weight, a lot of time a larger wheel/tire combo could weigh less than the stock setup. I'm new to the WRX world, but a stock DSM 16" w/tire could weigh easily close to 45 lbs. if you got a lightweight setup in 17" or even 18" it could weigh less than the 16", and allow for a net loss in weight, which would lower the unsprung weight, and is highly desirable.
Dahveed aka Robin Hood
iTrader: (3)
Joined: Nov 2002
Posts: 4,793
From: Robbin' the Hood (Claycord)
Car Info: (RIP) '04 STi Silver
Originally Posted by sireatalot
people always say there is rubbing when it comes to 40 and below.. how did you get away from that?
Registered User
iTrader: (4)
Joined: Nov 2002
Posts: 3,549
From: HK / BAIC (still in denial)
Car Info: '08 GT3/'08 Cayenne Turbo/'02 WRX Sedan/'95 E36 M3
Originally Posted by 1fastGC
18x9 +35mm offset 245/40/18 S03s
no rubbing at all.
no rubbing at all.
VIP Member
iTrader: (3)
Joined: Nov 2002
Posts: 1,804
From: Oakland/El Cerrito, CA
Car Info: Evolution VIII
Originally Posted by babysmurf
only 245's?? you can do better
Registered User
iTrader: (4)
Joined: Nov 2002
Posts: 3,549
From: HK / BAIC (still in denial)
Car Info: '08 GT3/'08 Cayenne Turbo/'02 WRX Sedan/'95 E36 M3
Originally Posted by 1fastGC
the s03s 245s are relatively equivalent to most 255s on the market. I could have gone 255/35/18s but didn't feel like fork out that kind of $
just giving u a hard time
hahahaha
I <3 White Girls
iTrader: (38)
Joined: Nov 2002
Posts: 26,491
From: Danville, CA
Car Info: E92 M3, E70, F32, E21
Originally Posted by blue blurr
i have Tarmac 2's in 17's and it looks awsome IMO, looks much better then 18's or at least a little better
VIP Member
iTrader: (3)
Joined: Jan 2004
Posts: 5,312
From: Why the **** is
Car Info: this required information?
Originally Posted by 02BlackWRX
I think everyone here will agree that as far as looks are concerned 18's > 17's