Calculate total lowered height? - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

Warlin · 12-15-2017, 03:04 PM

Hey guys, just wondering how one calculates total height lowered when running different tire size as well as a drop. I just received my 17’ BRZ, and have decided to go with the Eibach Sportline Springs, a 1.4” drop, as well as 235/45/17 Hankook Ventus, which add .7” height. I’m wondering if the calculations for figuring out how much lower the car will be is simply the decrease in height from the springs plus the increase in height from the tire (netting .7” lower) or if there is a more correct method. Thank you!

Leonardo · 12-15-2017, 03:38 PM

Welcome to the forum!

You need to divide the tire height addition in half then subtract that from the 1.4" lower to make 1.05" inches lower.

Additionally, springs can/may vary a few mm in drop. A 235/45/17 is 2.8% larger diameter than stock. Generally, you do not want to go more than 3% larger diameter. Hancook makes 10+ tires that start with "Ventus"; which one have you chosen?

My $0.02 - Get Eibach prokit springs and 225/45/17's. IMO the tires will work better on the stock wheels and weigh 3lbs less than the 235/45's. TRD Springs are rebranded Eibach prokit's, which have been proven to work well with the stock shocks. Sportline's will decrease the life of you stock shock and have a rougher ride. This is my opinion. Ignore it if you want.

DIY for spring install.
http://www.ft86club.com/forums/showthread.php?t=10842

Warlin · 12-15-2017, 11:46 PM

Thank you for the help, I tried so hard to figure this out! I appreciate your suggestion on the lowering springs as well; my decision for the Sportline was due to this being a non-daily car. Also, I didn’t mention, but the springs are going on the same time as my Avid1 AV20 rims, which are 17x8, which is why I decided to go with the 235 over the 225 to get that extra width and height so that the car does not bottom out too much.

Poodles · 12-15-2017, 11:55 PM

Keep in mind a larger tire will lead to a smaller gap between the tire and fender/wheelwell. You'll increase the chance of rubbing, plus you might lose steering feel.

Depends on what you're really looking for from the car and why you're lowering it.

Leonardo · 12-16-2017, 12:04 AM

With a 17x8 +35 you could run a 245/40 and some camber bolts. The 245/40 is the correct diameter and weighs a pound less than the 235/45

12-15-2017, 03:04 PM	#1
Warlin Member Join Date: Dec 2017 Drives: 17 Blue BRZ, MT Location: Central Arkansas Posts: 20 Thanks: 14 Thanked 6 Times in 5 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	Calculate total lowered height? Hey guys, just wondering how one calculates total height lowered when running different tire size as well as a drop. I just received my 17’ BRZ, and have decided to go with the Eibach Sportline Springs, a 1.4” drop, as well as 235/45/17 Hankook Ventus, which add .7” height. I’m wondering if the calculations for figuring out how much lower the car will be is simply the decrease in height from the springs plus the increase in height from the tire (netting .7” lower) or if there is a more correct method. Thank you!

12-15-2017, 03:38 PM	#2
Leonardo Country Boy 4 Life Join Date: Jul 2012 Drives: 19' & 06' Ridgelines, 13' FR-S Location: EUGENE Posts: 5,228 Thanks: 6,719 Thanked 5,291 Times in 2,720 Posts Mentioned: 47 Post(s) Tagged: 1 Thread(s)	Welcome to the forum! You need to divide the tire height addition in half then subtract that from the 1.4" lower to make 1.05" inches lower. Additionally, springs can/may vary a few mm in drop. A 235/45/17 is 2.8% larger diameter than stock. Generally, you do not want to go more than 3% larger diameter. Hancook makes 10+ tires that start with "Ventus"; which one have you chosen? My $0.02 - Get Eibach prokit springs and 225/45/17's. IMO the tires will work better on the stock wheels and weigh 3lbs less than the 235/45's. TRD Springs are rebranded Eibach prokit's, which have been proven to work well with the stock shocks. Sportline's will decrease the life of you stock shock and have a rougher ride. This is my opinion. Ignore it if you want. DIY for spring install. http://www.ft86club.com/forums/showthread.php?t=10842 __________________ I LIKE TIRES!

12-16-2017, 12:04 AM	#5
Leonardo Country Boy 4 Life Join Date: Jul 2012 Drives: 19' & 06' Ridgelines, 13' FR-S Location: EUGENE Posts: 5,228 Thanks: 6,719 Thanked 5,291 Times in 2,720 Posts Mentioned: 47 Post(s) Tagged: 1 Thread(s)	With a 17x8 +35 you could run a 245/40 and some camber bolts. The 245/40 is the correct diameter and weighs a pound less than the 235/45 __________________ I LIKE TIRES!

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12-15-2017, 11:46 PM	#3
Warlin Member Join Date: Dec 2017 Drives: 17 Blue BRZ, MT Location: Central Arkansas Posts: 20 Thanks: 14 Thanked 6 Times in 5 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	Thank you for the help, I tried so hard to figure this out! I appreciate your suggestion on the lowering springs as well; my decision for the Sportline was due to this being a non-daily car. Also, I didn’t mention, but the springs are going on the same time as my Avid1 AV20 rims, which are 17x8, which is why I decided to go with the 235 over the 225 to get that extra width and height so that the car does not bottom out too much.

12-15-2017, 11:55 PM	#4
Poodles Senior Member Join Date: Oct 2013 Drives: 2015 Series.Blue Location: Fort Worth, TX Posts: 1,781 Thanks: 88 Thanked 781 Times in 481 Posts Mentioned: 16 Post(s) Tagged: 0 Thread(s)	Keep in mind a larger tire will lead to a smaller gap between the tire and fender/wheelwell. You'll increase the chance of rubbing, plus you might lose steering feel. Depends on what you're really looking for from the car and why you're lowering it.

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