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-   -   Another Bilstein Outback story (http://legacygt.com/forums/showthread.php?t=200481)

Impatient 01-26-2013 11:36 PM

Another Bilstein Outback story
 
Good info coming: I just acquired FRONT Bilstein HDs. I will compare dimensions to stock Legacy struts and Outback struts (actually the 05+ KYB aftermarket version).

Bilstein HD's are in between in length, especially if you factor in the spec B tophat. Haven't mounted them yet, but expect HD's to lower front ride height less than 0.75 inch if I use stock Outback XT 5M springs. There will be less clearance with the tire than stock OB, but slightly better than with Legacy strut. The HD is approx 1/2 inch longer bottom bolt to basket compared to Legacy strut, and about 0.75 inch shorter than OB strut. The max spring length (loaded) should be 0.25 inch less than loaded OB strut or Legacy strut (yes, I think OB & Legacy accomodate same spring length).

I think this could be somewhat useful info for OBXT owners who want something better than KYB. Some others have done similar with LGT springs (Easton), and with LGT lowering springs (BAC5.2). Some others with Spec B struts and some spring, but not sure if anyone else has done with OBXT springs.

My concern is that the HD front will be stiffer than what I want....but we'll see. Currently running 00-04 JDM Bilstein which are softer, ride GREAT, handle just fine, but actually raise the front ride height...which I don't like.

Legacy struts would probably be 0.5 inch lower than the HD's....with Outback springs.

I'm probably going to try the HD's with Outback XT 5M springs with about 1/3 of the coil cut (on the bottom side)....or the full OBXT 5M spring (I have both, as well as LGT 5M...which are shorter/softer...or I guess I could even use some spec B front springs I acquired). In the rear, I have some adjustability, just need to get the front right, then the rear can be dialed as needed.

Moderators / veterans: Where should I be posting this stuff for maximum benefit? Hate to do new thread. Will double post over on Subaroutback.org.....just warning you.

Impatient 01-26-2013 11:37 PM

Got things installed today: Front Bilstein HD's (for Legacy GT with required spec B tophats). I had lots of springs to choose from (more than the dealer http://www.subaruoutback.org/forums/...s/rolleyes.gif). For the front, chose my OBXT 5M springs (std for my car) except I've cut them down a bit (about 1/3 bottom coil).

I changed the front first and drove it around before changing up the rear. It was a definite improvement. I REALLY like these HD's. They really work like premium shocks/springs should. The JDM Bilsteins with OBXT springs in the rear were still a little funky, still skipping off speedbumps the fronts just ate for breakfast. But overall car was better. Front hub-to-fender is about 16.25". I haven't had 100% stock in awhile, but I think this is 0.75" lower than stock.

Then dove into swapping the rear springs. Flipped a coin and installed Legacy GT wagon springs. They are similar to OBXT springs, but shorter. I think the wire-size is identical, or maybe the LGT's are the slightest bit thicker. The JDM Bilstein rear shocks I've had for awhile are height adjustable. I left them at the height closest to the 02-04 rear OB KYB's. But these Bilsteins don't have as long a shaft as the KYB's, so the OBXT springs I've been running with them were a bit crammed. They already were better than the KYB's IMHO, but had their quirks with those springs. The LGT springs were an easier fit (less pre-load). This changed the car manners more than I thought it would. The rear now feels MUCH softer, though I'm pretty sure spring rate should be the same. I can now roll over speedbumps with a LOT LESS trepidation. Ride feels much more luxurious...I was thinking this is what attracted me to the Outback vs the Forester in the first place....but ride is better than brand new while handling is improved. All in all it feels much more sophisticated. Rear hub to fender is now ~ 16.5".

So for the moment, I think I have made a significant upgrade. I will keep an eye out for "settling" and if I feel like blowing another afternoon, I might raise the rear lower perch height by 1 notch (~ 10mm). ****EDIT: I ended up doing this, see http://legacygt.com/forums/showpost....9&postcount=24 below with pics ****

Summary:

front: stock Swaybar, Bilstein HD's (35-118305 & -312), spec B tophats (20320AG01A) and stock OBXT 5sp springs cut by about 1/3 coil (bottom). STI / Legacy Spec B (rubber) LCA bushings.

rear: Cobb 22mm RSB with mount reinforcements, Legacy GT stock wagon springs, JDM 00-04 "Lancaster Special" custom Bilsteins. I'm sorry, but I have no idea how you can get these except from Japan....and frankly the BTS kit is probably the better way. But if you are lucky to find these, they're certainly more comfortable and sophisticated-feeling than the 02-04 rear KYB's.

PS, I've had the 05+ aftermarket KYB's in front, along with the 04- KYB's in back. I switched to the aforementioned JDM rear Bilsteins. That was an improvement. Then swapped in the matching front JDM Bilsteins. Ride improved 200%, but ride height was INCREASED over stock http://www.subaruoutback.org/forums/...lies/frown.gif. So bit the bullet to buy these front HD's. If you want to use the rear HD's, you WILL have to use spacers.

**** I really shouldn't recommend cutting springs, will not be responsible if they blow up on you, but I think it worked for me....so far.****

**** I don't know if you can use the front HD's with tires larger than stock. The lower perch is much closer to the tire than normal Outback strut perches****

**** this is not a race setup, but seems VERY satisfying as an aggressive DD solution. Anyone that has the money to tweak their engine or exhaust really ought to consider doing the Bilsteins first. IMHO http://www.subaruoutback.org/forums/...es/biggrin.gif ****

**** I never load the rear down with a lot of weight. So this is not necessarily a solution for you "cargo haulers." My normal load is either nothing or a sub-30lb mountain bike.****


Here is something EVERYONE can do:

http://legacygt.com/forums/showpost....0&postcount=55

Lower than mine, but utilizes the readily available Bilstein HD's in the rear as well.

*****Thank you Easton for all your inspiration and advice******

SCASEYS 01-29-2013 10:01 AM

wait, cut the springs?
Turbodog, is that you?

Impatient 01-29-2013 08:35 PM

snob.

BAC5.2 01-29-2013 08:45 PM

Cut springs? Really?

Impatient 01-29-2013 11:25 PM

come drive it

Impatient 01-29-2013 11:25 PM

some pics comparing:

1) Legacy GT strut (no spring, showing yellow bumper),
2) Bilstein Legacy GT HD strut (with spec B tophat...which adds a little height compared to stock OB tophat: YES it does!!!))
3) OBXT strut / spring
and on the other picture
4) the silver JDM Bilsteins I found with stock OBXT spring cut by 1/3 coil. these use normal USDM tophat, not the spec B tophat)

http://www.subaruoutback.org/forums/...q-dscf3023.jpg

http://www.subaruoutback.org/forums/...q-dscf3035.jpg

All bottom mount holes are lined up, so any variation at top of units shows dimensional differences.

note, legacy shortest, then HD, then stock OB (actually an 05-09 KYB aftermarket), then longest is the silver JDM Bilstein.

each little square on my floor is 1/2 inch.

Mount them on the car, loaded down, things obviously change: the JDM's are the tallest, then OB, then HD (shortest). I THINK the JDM's are tallest, not because of the strut body length, but because of the gas pressure (in conjunction with the fact that the strut CAN extend further), and the HD's have lower perch and shorter travel, but gain back a bit because of the Spec B tophats. I never mounted Legacy struts, but assume the shortest of the bunch mounted, in actual use. I would have thought that JDM's would have equalled stock OB, since lower body is identical SIZE (although smaller perch...no "basket"), but they extend further and weight of car doesn't comepletely negate Bilstein gas pressure.

Kelvrick 01-30-2013 02:59 PM

Do you plan on swapping in the full length outback xt spring soon? I'd be very interested in that.

BAC5.2 01-30-2013 03:35 PM

Quote:

Originally Posted by Impatient (Post 4269312)
come drive it

I'm not sure I would want to. There are a LOT of reasons to not cut a spring.

Quote:

Originally Posted by Impatient (Post 4269313)
Mount them on the car, loaded down, things obviously change: the JDM's are the tallest, then OB, then HD (shortest). I THINK the JDM's are tallest, not because of the strut body length, but because of the gas pressure (in conjunction with the fact that the strut CAN extend further), and the HD's have lower perch and shorter travel, but gain back a bit because of the Spec B tophats. I never mounted Legacy struts, but assume the shortest of the bunch mounted, in actual use. I would have thought that JDM's would have equalled stock OB, since lower body is identical SIZE (although smaller perch...no "basket"), but they extend further and weight of car doesn't comepletely negate Bilstein gas pressure.

Gas pressure in the shock/strut doesn't impact the "stiffness" of the strut. The gas charge really only acts to prevent foaming of the oil. Remember that the gas charge is on TOP of the oil, but the strut is controlled by the motion of a piston IN the oil.

The height difference is almost entirely related to the fact that the Bilstein is an inverted strut vs. the standard strut that the OB comes with. That means that in the Bilstein, the piston rod is pointing downward, and the oil is in the upper portion (the exact opposite of the stock setup).

Impatient 01-30-2013 07:50 PM

Quote:

Originally Posted by Kelvrick (Post 4270437)
Do you plan on swapping in the full length outback xt spring soon? I'd be very interested in that.

R U talking front or rear? But I think the answer is no, regardless.

Rears: been there, done that. This is better.

Maybe if the fronts explode, I'll have to. :eek:

Or maybe when it's time to sell.

Impatient 01-30-2013 08:32 PM

Quote:

Originally Posted by BAC5.2 (Post 4270522)
I'm not sure I would want to. There are a LOT of reasons to not cut a spring.

I witnessed the TurboDog thrashing. After that, I almost didn't do it, and after doing it, I thought of not mentioning it. But right now, after ~2K miles, I can't think of anything wrong with it, and have to ask, what is the alternative? LGT springs are softer, and cramming the full OBXT spring in there might not ride well either I tried to find a commerically available solution, and just plain didn't find one. I don't want my car as low as yours (to each his own)...nor any spacers, and I've learned that preloading too long a spring onto a shock or strut doesn't necessarily work well either.

Gas pressure in the shock/strut doesn't impact the "stiffness" of the strut. The gas charge really only acts to prevent foaming of the oil. Remember that the gas charge is on TOP of the oil, but the strut is controlled by the motion of a piston IN the oil.

The height difference is almost entirely related to the fact that the Bilstein is an inverted strut vs. the standard strut that the OB comes with. That means that in the Bilstein, the piston rod is pointing downward, and the oil is in the upper portion (the exact opposite of the stock setup).

I'm anxious to learn why this matters. To my thinking, all relevant dimensions were identical except the available height (extended length) and any "extension force" within the damper. Strut body, tophat structure, and actual spring were identical. i would have thought loaded by vehicle weight, the spring would have compressed the same regardless of the damper, but this must have been the mistaken assumption.

But my lawyer tells me to not recommend anyone else cut their springs :icon_roll

DK76 01-31-2013 12:42 PM

4 Attachment(s)
Just to contribute. Got Billstein Spec-B HD installed on my OBXT. 1/2 spacers in the rear.

BAC5.2 01-31-2013 01:15 PM

My car isn't that low, and there's no issue using spacers. You always have the option of custom springs. Eibach used to, and probably still does, make custom springs. IIRC they weren't that expensive.

The principal of an inverted strut is kind of simple, when you think about it. Gas is always on TOP of the oil, right? In a standard strut, that gas is up at the maximum extension of the piston rod (where the piston will never travel). Because of this, standard struts are typically limited in extension but have relatively large compression displacements. The exact opposite occurs in an inverted strut, where the gas is captive up by the strut mount. Inverted dampers can extend quite a ways, but are usually limited on compression strokes. Damper oil viscosity, piston diameter, piston orafice diameter, etc. all play a role as well.

The force required to overcome the effect of the gas in the strut is likely very small between two struts.

ssbtech 01-31-2013 03:32 PM

BAC, I'm still interested in those spacers...

BAC5.2 01-31-2013 04:00 PM

PM me your e-mail, and I'll send you pics straight from my phone.


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