GD/GG Impreza (WRX/STi) springs on BC/BF/BJ cars: UPDATED
Posted: Tue Jul 26, 2005 6:55 am
After some searching and quick logic we may have found that it is possible to use 04+ impreza rear springs on first generation suspension cars. First gen meaning bc/bf/bj/gc/gf/gm/sf/sg.
According to this thread:
http://forums.nasioc.com/forums/showpos ... ostcount=5
90-91 rear springs taper to 95mm at the top. We suspect this is the ID of the spring.
And according to this thread:
http://forums.nasioc.com/forums/showpos ... stcount=78
04+ Impreza rear springs taper to 100mm at the top using the ID.
The reason we suspect it's the ID is if you look at the other info from the first thread the rear spring top diameter is 125mm for non-tapered first gen springs and 130 for 02-03 impreza springs. In the other thread the rear suspension top diameter is listed as 100mm ID or 126mm OD. These rear springs wont fit with first gen rear spring perches, per this thread: http://bbs.legacycentral.org/viewtopic.php?t=21883 So the measurement has to be an ID measurement, which means the rear spring top diameter is 100mm for 04+ impreza.
Now, 95mm for 90-91 legacy rear spring top diameter, 100mm for 04+ impreza rear spring top diameter, the difference is 5mm. That is theoretically workable.
So what does this all mean? Well, it means theoretically you should be able to use 04+impreza rear suspension(including STi) if you use 90-91 legacy rear spring perches and top mounts. If 90-91 rear spring perches and top mounts are separate units you should be able to use sti gc rear top mounts. If they are one single unit, you'll have to use them, or find sti rear top mounts that are tapered.
Anyway, though this might be of use to someone.
EDIT: Psychoreo has confirmed this works.
EDIT #2:
I'm currently using 04 US STi struts with JDM GDB C-F Pink springs. The springs are listed as a 20mm/20mm front/rear drop for STi's. STi's are 10mm/10mm lower than WRX Sedans to start with, and 1mm/10mm lower than WRX Wagons. My hub to fender measurements are 343mm/311mm. Stock is 393mm/364mm. This setup provides a 50mm/53mm drop. This means a stock 04 US STi setup should be a 30mm/33mm drop or 363mm/331mm. A stock US WRX Sedan setup should be 20mm/23mm or 373mm/341mm. A stock US WRX Wagon setup should be 29mm/23mm or 364mm/341mm
These numbers are all based on my original measurements of my 90 Sedan LS 4WD so your ride heights may vary.
EDIT #3 by DerFahrer: Final clarification.
PLEASE READ THOROUGHLY before asking your question.
If you have a 90-91 Legacy, you can use 04-07 Impreza springs as direct replacements. The 90-91 Legacies have tapered rear springs like the 04-07 Imprezas do, so they will fit. Below are 04 WRX sedan part numbers as an example.
04 WRX sedan front springs: 20330FE861
04 WRX sedan left rear spring: 20380FE830
04 WRX sedan right rear spring: 20380FE820
From my post below, here are the part numbers you will need to have to use 04-07 Impreza springs on your 90-91 Legacy.
04 WRX front top hat: 20323FA000
04 WRX front rubber spring seats: 20325AA000
(all 02-07 Impreza front top hats and rubber spring seats are the same)
91 Legacy rear upper rubber spring seats: 20375AA011
04 WRX rear lower rubber spring seats: 20375FC001
(all 02-07 Impreza rear lower rubber springs seats are the same)
04 WRX front strut bearing washers: 20326AA000
(all 02-07 Impreza front strut bearing washers are the same)
You can use 04-07 Impreza rear tapered springs on your 92-94 Legacy, but you will need to switch to the 90-91 strut mount setup. To do so, or if you just want to replace your strut mounts, you will need these part numbers:
91 Legacy left rear FWD strut mount: 20370AA030
91 Legacy left rear 4WD strut mount: 20370AA010
91 Legacy right rear FWD strut mount: 20370AA020
91 Legacy right rear 4WD strut mount: 20370AA000
If you have a 92-94 Legacy, you can use 02-03 Impreza springs as direct replacements. The 92-94 Legacies do not have tapered rear springs, and neither do the 02-03 Imprezas. Below are 02 WRX sedan spring part numbers as an example.
02 WRX sedan front springs: 20330FE230
02 WRX sedan left rear spring: 20380FE630
02 WRX sedan right rear spring: 20380FE620
From my parts catalogue at work, here are the part numbers you will need to have to use 02-03 Impreza springs on your 92-94 Legacy.
02 WRX sedan front top hat: 20323FA000
02 WRX front rubber spring seats: 20325AA000
(all 02-07 Impreza front top hats and rubber spring seats are the same)
92 Legacy rear upper rubber spring seats: 20375AA030
02 WRX rear lower rubber spring seats: 20375FC001
(all 02-07 Impreza rear lower rubber springs seats are the same)
02 WRX front strut bearing washers: 20326AA000
(all 02-07 Impreza front strut bearing washers are the same)
You can use 02-03 Impreza rear non-tapered springs on your 90-91 Legacy, but you will need to switch to the 92-94 rear strut mount setup. To do so, or if you just want to replace your strut mounts, you will need these part numbers:
92-94 Legacy rear strut mounts: 20370AA200
92-94 Legacy rear top hats: 20373AA200
If you want to replace your front strut mounts, you will need these part numbers:
90-94 Legacy nonturbo front strut mounts: 20320AA100
90-94 Legacy turbo front strut mounts: 20320AA110
With the guidelines above, any 02-07 Impreza spring (RS/TS/OBS/WRX/STi) will work on any 90-94 Legacy.
Any 02-04 Impreza (RS/TS/OBS/WRX/STi) strut will also work. But 05+ struts will not work without modification.
This is all to the best of my knowledge, using the information already presented in this thread, and my Subaru parts catalogue at work. Some of the above part numbers may not be necessary, but all necessary part numbers are listed.
If your fitment or compatibility question isn't answered here, it's likely answered in the Suspension Information Compendium.
Finally, if anyone more qualified would like to correct anything above or has something else to add, they are welcome to do so.
According to this thread:
http://forums.nasioc.com/forums/showpos ... ostcount=5
90-91 rear springs taper to 95mm at the top. We suspect this is the ID of the spring.
And according to this thread:
http://forums.nasioc.com/forums/showpos ... stcount=78
04+ Impreza rear springs taper to 100mm at the top using the ID.
The reason we suspect it's the ID is if you look at the other info from the first thread the rear spring top diameter is 125mm for non-tapered first gen springs and 130 for 02-03 impreza springs. In the other thread the rear suspension top diameter is listed as 100mm ID or 126mm OD. These rear springs wont fit with first gen rear spring perches, per this thread: http://bbs.legacycentral.org/viewtopic.php?t=21883 So the measurement has to be an ID measurement, which means the rear spring top diameter is 100mm for 04+ impreza.
Now, 95mm for 90-91 legacy rear spring top diameter, 100mm for 04+ impreza rear spring top diameter, the difference is 5mm. That is theoretically workable.
So what does this all mean? Well, it means theoretically you should be able to use 04+impreza rear suspension(including STi) if you use 90-91 legacy rear spring perches and top mounts. If 90-91 rear spring perches and top mounts are separate units you should be able to use sti gc rear top mounts. If they are one single unit, you'll have to use them, or find sti rear top mounts that are tapered.
Anyway, though this might be of use to someone.
EDIT: Psychoreo has confirmed this works.
EDIT #2:
I'm currently using 04 US STi struts with JDM GDB C-F Pink springs. The springs are listed as a 20mm/20mm front/rear drop for STi's. STi's are 10mm/10mm lower than WRX Sedans to start with, and 1mm/10mm lower than WRX Wagons. My hub to fender measurements are 343mm/311mm. Stock is 393mm/364mm. This setup provides a 50mm/53mm drop. This means a stock 04 US STi setup should be a 30mm/33mm drop or 363mm/331mm. A stock US WRX Sedan setup should be 20mm/23mm or 373mm/341mm. A stock US WRX Wagon setup should be 29mm/23mm or 364mm/341mm
These numbers are all based on my original measurements of my 90 Sedan LS 4WD so your ride heights may vary.
EDIT #3 by DerFahrer: Final clarification.
PLEASE READ THOROUGHLY before asking your question.
If you have a 90-91 Legacy, you can use 04-07 Impreza springs as direct replacements. The 90-91 Legacies have tapered rear springs like the 04-07 Imprezas do, so they will fit. Below are 04 WRX sedan part numbers as an example.
04 WRX sedan front springs: 20330FE861
04 WRX sedan left rear spring: 20380FE830
04 WRX sedan right rear spring: 20380FE820
From my post below, here are the part numbers you will need to have to use 04-07 Impreza springs on your 90-91 Legacy.
04 WRX front top hat: 20323FA000
04 WRX front rubber spring seats: 20325AA000
(all 02-07 Impreza front top hats and rubber spring seats are the same)
91 Legacy rear upper rubber spring seats: 20375AA011
04 WRX rear lower rubber spring seats: 20375FC001
(all 02-07 Impreza rear lower rubber springs seats are the same)
04 WRX front strut bearing washers: 20326AA000
(all 02-07 Impreza front strut bearing washers are the same)
You can use 04-07 Impreza rear tapered springs on your 92-94 Legacy, but you will need to switch to the 90-91 strut mount setup. To do so, or if you just want to replace your strut mounts, you will need these part numbers:
91 Legacy left rear FWD strut mount: 20370AA030
91 Legacy left rear 4WD strut mount: 20370AA010
91 Legacy right rear FWD strut mount: 20370AA020
91 Legacy right rear 4WD strut mount: 20370AA000
If you have a 92-94 Legacy, you can use 02-03 Impreza springs as direct replacements. The 92-94 Legacies do not have tapered rear springs, and neither do the 02-03 Imprezas. Below are 02 WRX sedan spring part numbers as an example.
02 WRX sedan front springs: 20330FE230
02 WRX sedan left rear spring: 20380FE630
02 WRX sedan right rear spring: 20380FE620
From my parts catalogue at work, here are the part numbers you will need to have to use 02-03 Impreza springs on your 92-94 Legacy.
02 WRX sedan front top hat: 20323FA000
02 WRX front rubber spring seats: 20325AA000
(all 02-07 Impreza front top hats and rubber spring seats are the same)
92 Legacy rear upper rubber spring seats: 20375AA030
02 WRX rear lower rubber spring seats: 20375FC001
(all 02-07 Impreza rear lower rubber springs seats are the same)
02 WRX front strut bearing washers: 20326AA000
(all 02-07 Impreza front strut bearing washers are the same)
You can use 02-03 Impreza rear non-tapered springs on your 90-91 Legacy, but you will need to switch to the 92-94 rear strut mount setup. To do so, or if you just want to replace your strut mounts, you will need these part numbers:
92-94 Legacy rear strut mounts: 20370AA200
92-94 Legacy rear top hats: 20373AA200
If you want to replace your front strut mounts, you will need these part numbers:
90-94 Legacy nonturbo front strut mounts: 20320AA100
90-94 Legacy turbo front strut mounts: 20320AA110
With the guidelines above, any 02-07 Impreza spring (RS/TS/OBS/WRX/STi) will work on any 90-94 Legacy.
Any 02-04 Impreza (RS/TS/OBS/WRX/STi) strut will also work. But 05+ struts will not work without modification.
This is all to the best of my knowledge, using the information already presented in this thread, and my Subaru parts catalogue at work. Some of the above part numbers may not be necessary, but all necessary part numbers are listed.
If your fitment or compatibility question isn't answered here, it's likely answered in the Suspension Information Compendium.
Finally, if anyone more qualified would like to correct anything above or has something else to add, they are welcome to do so.