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2017 Impreza Hatch, 1.5/1.8 ADF Lift
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Discussion Starter · #1 ·
Hi all,
Longtime lurker who just decided to make an account, I’ve used some of the posts here as a guide as I try to beef up my 2017 hatch. I installed an ADF lift recently and am looking to throw some AT’s (likely 215 65/R16 Wildpeaks) on for added grip and a little more clearance. My only question is should I be concerned about transmission stress/damage? When I mentioned my plans while picking up OEM parts from my dealership they said the increased diameter/weight would put too much stress on the CVT. I’ve found mention of this with more substantial tire size increases but nothing specific. Thanks!
 

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2021 Subaru Impreza 5-Door Sport 5MT
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Hi all,
Longtime lurker who just decided to make an account, I’ve used some of the posts here as a guide as I try to beef up my 2017 hatch. I installed an ADF lift recently and am looking to throw some AT’s (likely 215 65/R16 Wildpeaks) on for added grip and a little more clearance. My only question is should I be concerned about transmission stress/damage? When I mentioned my plans while picking up OEM parts from my dealership they said the increased diameter/weight would put too much stress on the CVT. I’ve found mention of this with more substantial tire size increases but nothing specific. Thanks!
Anytime you introduce additional weight to a driveline, you are also introducing more stress. Sudden speed changes are the killer, not as much constant speed as you now have inertia on your side.

You're not the only one to lift an Subaru, so I'm sure there is a bunch of info out there around the topic but may be on other Subaru sites. CVT cooler may be in your near future, and OBK or Ascent models already run them in the TR690's so you may even be able to get your hands on an OEM one. CVT fluid changes will also be a good idea, probably every 20k-30k miles (closer to the 20k with the additional weight).

I wish I had more definite answers for you with data, but I hope the above mentioned items at least give you something to research further as a step in the right direction.
 

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Drag racers have a 'rule of thumb' which goes something like this....
"every pound of weight on a rotating tire is equivalent to 7 pounds sitting in the car"

This is an oversimplification of how mass behaves when rotated (as opposed to 'static' mass) but it kinda explains the concept.
 

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2017 Impreza Hatch, 1.5/1.8 ADF Lift
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Discussion Starter · #4 ·
Anytime you introduce additional weight to a driveline, you are also introducing more stress. Sudden speed changes are the killer, not as much constant speed as you now have inertia on your side.

You're not the only one to lift an Subaru, so I'm sure there is a bunch of info out there around the topic but may be on other Subaru sites. CVT cooler may be in your near future, and OBK or Ascent models already run them in the TR690's so you may even be able to get your hands on an OEM one. CVT fluid changes will also be a good idea, probably every 20k-30k miles (closer to the 20k with the additional weight).

I wish I had more definite answers for you with data, but I hope the above mentioned items at least give you something to research further as a step in the right direction.
No worries, I know this is kinda a niche interest haha. Yeah I’d browsed around here a decent amount, obviously saw people mention the slight MPG dip from larger tires but nothing beyond it. I know the 5th gen’s are approved for light towing in other countries (I want to say Australia and Canada?) with the same engine/CVT as US models that aren’t, makes me wonder if they’re capable of dealing with a little more stress than I think. I’m admittedly relatively new to this side of things so figured some people here would have a better idea
 

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I know the 5th gen’s are approved for light towing in other countries (I want to say Australia and Canada?) with the same engine/CVT as US models that aren’t, makes me wonder if they’re capable of dealing with a little more stress than I think.
I can't say for the Australia and Canada Imprezas, but I know that in the US, Crosstrek is rated for towing but the Impreza isn't, and the difference is that the USA Crosstrek has a CVT cooling line but the USA Impreza doesn't.
 

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the difference is that the USA Crosstrek has a CVT cooling line but the USA Impreza doesn't.
Are you certain about this?

My 2017 base Impreza has a "heat exchanger" which has CVT fluid and Antifreeze flowing thru it. Subaru calls it a "Transmission Cooler".
It is mounted to right side of engine and looks like this ==> https://d1vnbry5hm94g5.cloudfront.net/ABE/J7J/6SU/TH5/G.jpg

The Subaru P/N = 31237AA100

BTW: This very same P/N is used on Legacy, Ascent, Crosstrek, Outback,Forrester and WRX. (Even on the STI!)

This tells me that the "tow ratings" have NOTHING to do with the presence of CVT cooler.
 

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2021 Subaru Impreza 5-Door Sport 5MT
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Are you certain about this?

My 2017 base Impreza has a "heat exchanger" which has CVT fluid and Antifreeze flowing thru it. Subaru calls it a "Transmission Cooler".
It is mounted to right side of engine and looks like this ==> https://d1vnbry5hm94g5.cloudfront.net/ABE/J7J/6SU/TH5/G.jpg

The Subaru P/N = 31237AA100

BTW: This very same P/N is used on Legacy, Ascent, Crosstrek, Outback,Forrester and WRX. (Even on the STI!)

This tells me that the "tow ratings" have NOTHING to do with the presence of CVT cooler.
This is more of an oil warmer than it is a cooler, even though it does help to some degree. Manual transmission Impreza's do not get this, and the other models get a dedicated CVT cooler located by the radiator (except Impreza). Any vehicle with a tow package tends to have an upgraded trans cooler.
 

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2017 Impreza Hatch, 1.5/1.8 ADF Lift
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Discussion Starter · #8 ·
This is more of an oil warmer than it is a cooler, even though it does help to some degree. Manual transmission Impreza's do not get this, and the other models get a dedicated CVT cooler located by the radiator (except Impreza). Any vehicle with a tow package tends to have an upgraded trans cooler.
Is it worth looking into universal cooler lines/Crosstrek ones and mounting to a similar location if possible? I guess I’m trying to gauge how big of a concern it is if I’m easy on the car otherwise. I haven’t HEARD of any issues but I know the community is small haha
 

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2019 Subaru Impreza Sport 5 Dr. Manual Shift
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Some interesting info (okay debatable) on Wheel / Tire Weights and Rotational Inertia.

>>Click Me<<

I did not make this but saved a copy, my wife is an engineer so she likes stuff like this :)
 

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Some interesting info (okay debatable) on Wheel / Tire Weights and Rotational Inertia.

>>Click Me<<

I did not make this but saved a copy, my wife is an engineer so she likes stuff like this :)
Reminds me of my University physics course, though this is a lot more specific and in depth than I ever got. The flywheel spreadsheet definitely made me wonder due to the low power and torque of these engines. I'm curious how it would stack up against a similar hp/torque vehicle from say, three decades ago.
 

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Hi all,
Longtime lurker who just decided to make an account, I’ve used some of the posts here as a guide as I try to beef up my 2017 hatch. I installed an ADF lift recently and am looking to throw some AT’s (likely 215 65/R16 Wildpeaks) on for added grip and a little more clearance. My only question is should I be concerned about transmission stress/damage? When I mentioned my plans while picking up OEM parts from my dealership they said the increased diameter/weight would put too much stress on the CVT. I’ve found mention of this with more substantial tire size increases but nothing specific. Thanks!
Would not be worrying just about transmission. Also think about stress on the power steering circuit.
 

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2021 Subaru Impreza 5-Door Sport 5MT
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Is it worth looking into universal cooler lines/Crosstrek ones and mounting to a similar location if possible? I guess I’m trying to gauge how big of a concern it is if I’m easy on the car otherwise. I haven’t HEARD of any issues but I know the community is small haha
Can't hurt! Like others have stated, try out NASIOC and see what people have done for CVT cooling options. That should hopefully be a somewhat simple thing to take care of.
 

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2017 Impreza Hatch, 1.5/1.8 ADF Lift
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Discussion Starter · #13 ·
Can't hurt! Like others have stated, try out NASIOC and see what people have done for CVT cooling options. That should hopefully be a somewhat simple thing to take care of.
I’ll have to take a look, thanks! Haven’t seen too much in the way over there of warnings about oversized tires (mostly posts of people showing them off) which is slightly reassuring?
 

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Discussion Starter · #14 ·
Would not be worrying just about transmission. Also think about stress on the power steering circuit.
This would mostly be in regard to tire width/weight rather than the diameter increase though right? Even with the larger tires the overall combo is only slightly heavier than stock due to lighter wheels
 

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This would mostly be in regard to tire width/weight rather than the diameter increase though right? Even with the larger tires the overall combo is only slightly heavier than stock due to lighter wheels
Agreed.
The engine is wide. As a result, Subaru has the most advanced front drive system with tightest turning circle in the industry. Think about wheel offset with larger diameter tires. As for the weight. Do not know how closely the suspension is designed to the weight limits of the cars. Had to replace the torn front control arm bushing at 54,000 miles. Which suggests that the suspension is engineered closer to the bone—Subaru wants to be seen as a fuel efficient vehicle; fastest way to get there is reducing the weight of the vehicle with improved aerodynamics.
 
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