fahr_side Posted October 12, 2016 Share Posted October 12, 2016 ^^ This. I bent two of mine and was able to repair them. #3 had to be replaced. Went back to 17s very shortly after. My car is so much faster on the 17s and stops much quicker too. Brake wear also noticeably better. Only do 18s if you're determined to run a 355mm brake kit. Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs. Link to comment Share on other sites More sharing options...
jonnyt88 Posted October 13, 2016 Share Posted October 13, 2016 I've read some pretty credible sources say it's not wheel weight we feel nearly as much as it is the difference in diameter of the wheel and tire when talking about daily drivers. Sizes being the same (comparing a 17" wheel to another 17" wheel) a weight difference of say 6lbs per corner will not be noticed by many drivers I'm told. Wheel/tire diameter is what makes the noticeable difference for most of us who've switched. I wanted more comfort, more wheel and tire options, cheaper combos, and I got all of it with noticeably improved driveability when I switched. Both of my wheel setups are 16lbs/corner, so I don't know for sure. on my MR2 turbo I had stock 350z wheels 17x7.5 & 17x8. I swear they had to be pushing 30lb a pop. ran with 205/40 and 235/40 Swapped to 17x8 + 17x9 RPF1s, put the 235/40s up front and 255/40 in the back which increaded the rolling diameter of the rear. and it still made a significant difference Link to comment Share on other sites More sharing options...
Smithcraft Posted March 15, 2017 Author Share Posted March 15, 2017 Every time I go over a bump in the road I think the rim is bent! Who would want such low profile tires on a street car? Oh wait! My coworker that wants to put my SpecB wheels on his SH Forester. SC 1994 Legacy MI 2008 Legacy GT specB 2023 Crosstrek Limited Link to comment Share on other sites More sharing options...
xtea Posted March 15, 2017 Share Posted March 15, 2017 With how lite rpf1s are, would they be ok with 18's? Or is 17 still better? I almost bought some used xxr 530 18"s but saw this and it caused me pause. Link to comment Share on other sites More sharing options...
fahr_side Posted March 16, 2017 Share Posted March 16, 2017 With how lite rpf1s are, would they be ok with 18's? Or is 17 still better? I almost bought some used xxr 530 18"s but saw this and it caused me pause. Oh god those make great boat anchors! RPF-1 in 18 is pretty light but it doesn't fix the issues with short sidewalls. Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs. Link to comment Share on other sites More sharing options...
xtea Posted March 16, 2017 Share Posted March 16, 2017 Oh god those make great boat anchors! RPF-1 in 18 is pretty light but it doesn't fix the issues with short sidewalls. The issues being feeling more road imperfections, or the wheel inertia thing? Link to comment Share on other sites More sharing options...
BoozeRS05 Posted March 16, 2017 Share Posted March 16, 2017 Comfort of the tire he means, a 45 series tire is much more comfortable for a lowered daily driver. Both my setups are 17s, but my summers are 235/40, and my winters being 215/45 are so much nicer DDing. Also my 17x9 RPF1s are 17lbs. EB's Subaru journal - 2005 LegacyGT Wagon & 2014 Forester FB25 (2008 specB - RIP) IG@legacygtliving Link to comment Share on other sites More sharing options...
xtea Posted March 16, 2017 Share Posted March 16, 2017 Comfort of the tire he means, a 45 series tire is much more comfortable for a lowered daily driver. Both my setups are 17s, but my summers are 235/40, and my winters being 215/45 are so much nicer DDing. Also my 17x9 RPF1s are 17lbs. So 6lbs lighter then the xxrs. Is it really that much difference? Link to comment Share on other sites More sharing options...
Rhitter Posted March 16, 2017 Share Posted March 16, 2017 With Outback sized tires 235/45/18, our tire sidewalls aren't really short. So 6lbs lighter then the xxrs. Is it really that much difference? I think the short answer is yes. It's 6 pounds per corner of unsprung weight. Just switching to Legacy GT brakes (calipers and rotors) I could feel it in the cars acceleration. Made me realize I absolutely cannot go to a heavier wheel set-up than OEM. That being said, I am going to go to a lightish 18 inch wheel at 235/45/8. So, I will still have some sidewall. My OBXT build Link to comment Share on other sites More sharing options...
fahr_side Posted March 16, 2017 Share Posted March 16, 2017 With Outback sized tires 235/45/18, our tire sidewalls aren't really short. I think the short answer is yes. It's 6 pounds per corner of unsprung weight. Just switching to Legacy GT brakes (calipers and rotors) I could feel it in the cars acceleration. Made me realize I absolutely cannot go to a heavier wheel set-up than OEM. That being said, I am going to go to a lightish 18 inch wheel at 235/45/8. So, I will still have some sidewall. 6lbs unsprung in and of itself is not insignificant to the suspension. The bigger deal is the change in inertia. Neither the engine nor the brakes care about mass (weight) very much as 24lbs on the whole vehicle weight isn't a big change. What they need to overcome is inertia. A small change in wheel mass, when it is ~9" from the rotational axis, is a big change in inertia that the engine has to accelerate and the brakes decelerate. The same weight (mass) wheel in 17 and 18" will feel very different on the car because increasing the diameter even an inch increases the mass moment of inertia by a considerable amount. Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs. Link to comment Share on other sites More sharing options...
BoozeRS05 Posted March 16, 2017 Share Posted March 16, 2017 ^ this.. EB's Subaru journal - 2005 LegacyGT Wagon & 2014 Forester FB25 (2008 specB - RIP) IG@legacygtliving Link to comment Share on other sites More sharing options...
xtea Posted March 17, 2017 Share Posted March 17, 2017 6lbs unsprung in and of itself is not insignificant to the suspension. The bigger deal is the change in inertia. Neither the engine nor the brakes care about mass (weight) very much as 24lbs on the whole vehicle weight isn't a big change. What they need to overcome is inertia. A small change in wheel mass, when it is ~9" from the rotational axis, is a big change in inertia that the engine has to accelerate and the brakes decelerate. The same weight (mass) wheel in 17 and 18" will feel very different on the car because increasing the diameter even an inch increases the mass moment of inertia by a considerable amount. Love the physics lesson! This is what I wanted to know. So even a 17" rpf1 will feel quicker and more nimble then an 18. The 18s look so good though, but with tire costs its harder to justify given its entirely for looks. Link to comment Share on other sites More sharing options...
xtea Posted March 17, 2017 Share Posted March 17, 2017 6lbs unsprung in and of itself is not insignificant to the suspension. The bigger deal is the change in inertia. Neither the engine nor the brakes care about mass (weight) very much as 24lbs on the whole vehicle weight isn't a big change. What they need to overcome is inertia. A small change in wheel mass, when it is ~9" from the rotational axis, is a big change in inertia that the engine has to accelerate and the brakes decelerate. The same weight (mass) wheel in 17 and 18" will feel very different on the car because increasing the diameter even an inch increases the mass moment of inertia by a considerable amount. Love the physics lesson! This is what I wanted to know. So even a 17" rpf1 will feel quicker and more nimble then an 18. The 18s look so good though, but with tire costs its harder to justify given its entirely for looks. Link to comment Share on other sites More sharing options...
xtea Posted March 17, 2017 Share Posted March 17, 2017 With Outback sized tires 235/45/18, our tire sidewalls aren't really short. I think the short answer is yes. It's 6 pounds per corner of unsprung weight. Just switching to Legacy GT brakes (calipers and rotors) I could feel it in the cars acceleration. Made me realize I absolutely cannot go to a heavier wheel set-up than OEM. That being said, I am going to go to a lightish 18 inch wheel at 235/45/8. So, I will still have some sidewall. So you are saying the lgt brakes and rotars make the car feel slower? I was going to upgrade to those but maybe I'll just get fancy pads and master cylinder brace instead. Link to comment Share on other sites More sharing options...
xtea Posted March 17, 2017 Share Posted March 17, 2017 With Outback sized tires 235/45/18, our tire sidewalls aren't really short. I think the short answer is yes. It's 6 pounds per corner of unsprung weight. Just switching to Legacy GT brakes (calipers and rotors) I could feel it in the cars acceleration. Made me realize I absolutely cannot go to a heavier wheel set-up than OEM. That being said, I am going to go to a lightish 18 inch wheel at 235/45/8. So, I will still have some sidewall. So you are saying the lgt brakes and rotars make the car feel slower? I was going to upgrade to those but maybe I'll just get fancy pads and master cylinder brace instead. Link to comment Share on other sites More sharing options...
fahr_side Posted March 17, 2017 Share Posted March 17, 2017 Back in the day I upgraded my GF wagon from the stock 265mm single-pot setup to the 295mm WRX items. Car was notably slower to accelerate until I swapped the motor. I like to add brake mass for more heat capacity but offset that with lighter wheels. Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs. Link to comment Share on other sites More sharing options...
fahr_side Posted March 17, 2017 Share Posted March 17, 2017 Back in the day I upgraded my GF wagon from the stock 265mm single-pot setup to the 295mm WRX items. Car was notably slower to accelerate until I swapped the motor. I like to add brake mass for more heat capacity but offset that with lighter wheels. Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs. Link to comment Share on other sites More sharing options...
xtea Posted March 17, 2017 Share Posted March 17, 2017 Back in the day I upgraded my GF wagon from the stock 265mm single-pot setup to the 295mm WRX items. Car was notably slower to accelerate until I swapped the motor. I like to add brake mass for more heat capacity but offset that with lighter wheels. I had no idea brakes would effect the moment of inertia since the calipers float over the rotar. I can see the larger rotors though making the difference. Glad I got this info. I will not be going with bigger brakes then. Link to comment Share on other sites More sharing options...
xtea Posted March 17, 2017 Share Posted March 17, 2017 Back in the day I upgraded my GF wagon from the stock 265mm single-pot setup to the 295mm WRX items. Car was notably slower to accelerate until I swapped the motor. I like to add brake mass for more heat capacity but offset that with lighter wheels. I had no idea brakes would effect the moment of inertia since the calipers float over the rotar. I can see the larger rotors though making the difference. Glad I got this info. I will not be going with bigger brakes then. Link to comment Share on other sites More sharing options...
fahr_side Posted March 17, 2017 Share Posted March 17, 2017 I had no idea brakes would effect the moment of inertia since the calipers float over the rotar. I can see the larger rotors though making the difference. Glad I got this info. I will not be going with bigger brakes then. The calipers do not affect inertia but the rotors do. Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs. Link to comment Share on other sites More sharing options...
fahr_side Posted March 17, 2017 Share Posted March 17, 2017 I had no idea brakes would effect the moment of inertia since the calipers float over the rotar. I can see the larger rotors though making the difference. Glad I got this info. I will not be going with bigger brakes then. The calipers do not affect inertia but the rotors do. Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs. Link to comment Share on other sites More sharing options...
LatentWagen Posted March 17, 2017 Share Posted March 17, 2017 Calipers are unsprung but not rotating (inertial). Rotors, wheels, tires, lug nuts, valve stems & caps, etc, are all unsprung AND rotating. Forge and two-piece all the things! LW's spec. B / YT / IG Link to comment Share on other sites More sharing options...
LatentWagen Posted March 17, 2017 Share Posted March 17, 2017 Calipers are unsprung but not rotating (inertial). Rotors, wheels, tires, lug nuts, valve stems & caps, etc, are all unsprung AND rotating. Forge and two-piece all the things! LW's spec. B / YT / IG Link to comment Share on other sites More sharing options...
xtea Posted March 17, 2017 Share Posted March 17, 2017 Calipers are unsprung but not rotating (inertial). Rotors, wheels, tires, lug nuts, valve stems & caps, etc, are all unsprung AND rotating. Forge and two-piece all the things! So you could get super lite rotors and upgrade brakes and be fine then. Link to comment Share on other sites More sharing options...
xtea Posted March 17, 2017 Share Posted March 17, 2017 Calipers are unsprung but not rotating (inertial). Rotors, wheels, tires, lug nuts, valve stems & caps, etc, are all unsprung AND rotating. Forge and two-piece all the things! So you could get super lite rotors and upgrade brakes and be fine then. Link to comment Share on other sites More sharing options...
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