2008 Subaru Impreza Wagon

Sedans have a softer suspension than SUVs. I think they make SUVs with stiffer suspensions because people are more likely to roll a taller vehicle with the same spring rate. My goal is to go over stuff without a jarring ride. So if I were to buy an SUV, I would look for softer springs (while still maintaining the ride height). Although I would keep stock sway bars and maybe increase the torsion strength of the rear.

Lifting a car is done by increasing the height between the strut towers and the wheels. The height can be increased by a few different methods:

• Taller struts
• Lift kits: spacer between the strut and strut tower
• Stiffer springs
• Springs with stock spring rate but greater unloaded height
• Spring spacer above the coils
• Spring spacer within the coils

Stiffer springs will suck for maintaining traction off-road: the suspension should be able to travel to maintain contact with the ground.

Taller springs need extra precompression to install the spring into the strut. The same precompression can be achieved with a spring spacer above the stock springs, but with possible loss of upward suspension travel: more details. Above instead of below the coils to not add inertia.

A spring spacer within the coils also precompresses the spring, but will increase the spring rate by reducing the number of acting coils.

In order to not alter the suspension angles of the A arms or trailing arms, spacers can be placed above the suspension subframe so that everything is moved down along with the wheel. That way the suspension keeps it's original design: the arc the wheel travels remains the same.

However, moving the suspension subframe down does not increase the ground clearance for said subframe. What's going on down there? What are the low points of the bottom of the car?

Most lift kits are sold as spacers to be placed above the strut under the strut tower. 2“ or taller kits should include spacers for the subframe as well. 1” lift kits I've seen do not use subframe spacers. I hope the slight alteration to the geometry has acceptable performance.

The range of motion of the suspension is limited in both directions. Upward motion is limited by a bumper stop on the shock. In some cars, the bumper stop is not within the strut. See Westcott Designs on YouTube.

Depending on the vehicle, the droop (maximum downward position) is limited by either suspension bind or the shock limit.

If the original suspension is capable of added range, then a softer spring rate is desired as it allows greater motion going over rough terrain.

An increased coil count can give a lesser spring rate, but if the spring is sufficiently precompressed in the strut, the car will ride higher.

The taller ride height (with only a change in spring) affords more upward motion and less downward motion for the wheel unless the damper/shock travel is also increased.

Will more average movement hurt the stock shock? gowesty doesn't mention any harm.

Some DIYers use the taller Subaru Forester struts which are 2“ taller than stock Impreza struts. Adding 2” to the ride height is enough to warrant subframe spacers. johnnyoptions on reddit Immortan Jon on YouTube

Taller struts, including taller shocks and springs could give added range, but then suspension arms would also need to be capable of a greater arc. A suspension is made to move the wheel through a certain trajectory. The trajectory arc changes in shape if you use a taller strut without longer control arms.

So should I get Forester struts or a lift kit plus taller springs? Even if I chose Forester struts for the added range, the stiffer springs will not allow that added range. So either way I'd be looking for custom taller springs. Although finding custom springs is difficult depending on which country you live in.

It would be good to compare side by side the suspensions of a Crosstrek and an Impreza. Is the 2008 Impreza suspension the same as a 2013 Impreza suspension, so I could actually compare the 2008 Impreza with a 2013 Crosstrek?

With stock struts, a bit of added wheel travel can be had by rim offset.

Scary message from Primitive Racing:

Spacers for the suspension subframe do not move the CV joint located at the engine transmission. The axle goes from the transmission to the center of the wheel.

If as I assumed, the lowest point of the intended range is limited by the full extension of the shock, then even with taller springs, the lowest point is unchanged.

My strut tower spacers are 1“ aluminum at front and 1.5” rubber compound for the rear. I would like a bit more lift, so I could add springs with a taller unloaded height. The wheels will be lower, so the CV axles will be continuously more stressed, but will not be overextended as the shocks limit the lowest wheel movement.

How much more continuously stressed is a good question. I wonder how much this affects fuel economy? Maybe there isn't much added stress, and only overextension is the bad actor.

The lowest point in the arc of the wheel is really extreme even without a lift! Perhaps the extreme + 2“ is what damages the CV joints? How much of the time are you applying stress to the CV joints while soaring over a hill with full throttle? Most street driving will never have the wheel reach the extreme, unless there is a huge crater of a pothole. Off-road action can provide extremes.

Robbie said the CV axles are at more of an angle turning than they are at maximum droop.

How does the lowest point (droop) with Forester struts compare with stock Impreza struts? If droop is 2” below stock, is there a way to limit it? Perhaps a custom top hat where the shock bolts to the strut will extend the strut piston to limit droop.

Is there actually a problem? Don't all vehicles with greater ground clearance require a CV joint at a greater angle? Has lifting your Subaru adversely affected / seriously shortened the CV life? subaruoutback.org My question on subaruoutback.org

Factors affecting lift: spring rate (kg/mm), unloaded height

Among other factors, the number and turn diameter of the coils affect the spring rate. The unloaded height depends on the spacing between the turns. None of this is advertised but at least I can visually inspect and count the number of turns.

My 2008 stock springs have exactly 4 coil turns. Spring rate is 183lbs/in 3.27kg/mm (extrapolated from Rallitek being 20% stiffer). The unloaded length of my stock 2008 front springs is 30cm left and 30.3cm right, although they were probably longer when new.

For comparison, the free length of Primitive Racing 0.25“ lift KSFS-52 (chart below) is 260mm (source: email).

For the 3rd generation Subaru Impreza, the Outback Sport model has the same suspension with a 6mm lift from taller tires. Crosstrek is the smallest of the current Subaru SUV: Crosstrek/XV, Forester, Outback, Ascent.

2008-2010 WRX springs fit. So maybe this applies. Here they say 2012 front Impreza springs fit on a 2008, so maybe the 2013 XV/Crosstrek springs with more coils will also fit?

Stock coil spring rates from kingsalami on wrxforums.com:

Aftermarket coil springs:

Why are the 2018 springs softer than the 2013? Maybe the length of the control arms and the locations of the struts. In which case I shouldn't estimate spring stiffness just by the weight of the vehicle. I could look into Forester and other Subaru spring rates.

I'm not sure about cost, but maybe the solution is to contact spring manufacturers to fabricate custom springs.

Moog Option

My course of action

The cheapest solution when wanting to increase ride height and/or spring stiffness.

Full coil spacers: Spring Rubbers Overview and Installation by FaRKle0079 on YouTube. Another Another.

Peg spacers: How To Install Coil Spring Spacers by Thousanddollarcarguy on YouTube.

In case the spring spacers are metal rather than flexible like rubber: “Should be fine as long as the bump stop is fully compressed before the spring runs out of travel. Typically with a solid axle vehicle you'd add an equivalent sized bump stop extension and shock relocation brackets.” Oricle10110 on Reddit

Placed on coil springs with few coils, the spring may bind before the bump stop is touched. Will this make a sound, where coils touch that wouldn't touch before?

With an elastic spacer, the spacer can also be a bump stop. If the spring binds right at the surface of the bump stop, the spacer may deform 1cm and the bump stop is also compressed. Thus, the decrease in suspension travel may just be from the combined bump stop. A stiffer bump stop is beneficial when the vehicle is carrying a larger load.

The softer ones are more meant to assist a spring by providing energy absorption and a slight progressive resistance to avoid the thud of bottoming out, or to avoid a slight wheel rub.

JSO Racing recommends using the gap between compressed coils for determining the height of the spacer. He goes on to say that his red spacers aren't capable of much lift, that their purpose is to absorb the hard hits. Especially if the shock is worn out.

Harder rubber would be chosen if lift is desired, also resulting in a stiffer spring.

I've seen destroyed spacers in reviews on Amazon.

I've seen ones that looked old but still intact, which were being replaced in this video by Suardi Tan, though not sure why they were being replaced, he removed red and placed green. There is a product on Amazon where red is the softest and green is the stiffest.

CARBITS TV took out 2 year old spacers (made of urethane) to reinstall them for this video. He doesn't recommend the clear ones on Amazon, saying they got yellow and started forming cracks with age. So the quality of the material matters. He also added harder spacers for lift because he was having wheel rub when he put wider stance wheels.

If the spacing between coils is lesser and the number of coils is greater, the deformation will be less and the spacer more likely to survive.

With greater deformation tearing can result, especially if soft spacers sit precompressed at rest, and especially if the spring bottoms out.

These products I list because there are tons of reviews, not because of merit:
https://www.amazon.com/product-reviews/B087X1LF1V/
https://www.amazon.com/product-reviews/B07GFHF9NQ/

Seems to me the most durable material would be akin to the high hardness used for automotive bushings.

If carrying load, high hardness will provide the most support to prevent vehicle sag. After all, you are only working with one coil of many, so make that one count.

Since loads mostly go on rear springs, the benefit of within-the-coil spacers is best applied there. The effect will still be felt on the front as there will be less body roll during corners, and unstiffened front springs can still track the ground with greater movement.

With the vehicle at rest on the suspension, choosing a spacer less thick than gap between coils will allow a soft ride until the coil contacts the spacer.

If lift is desired, it will come by increasing the spring rate of a single coil. Thus, this solution is a poor man's dual coil rate spring.

On a Subaru Impreza 2008-2011, the trailing arms are attached to the subframe, mounted on the side rather than underneath the subframe. A longer trailing arm or a slotted attachment point could be used to move the rear wheels back to the center of the wheel arch.

GodSpeed adjustable length rear trailing arms for WRX/STI

Unfortunately, Foresters use the same length trailing arms:

With the longer trailing arms, the caster would be shifted back towards original spec (caster defined as the angle of the strut tower).

Ok. It's been done.

The trailing arm was welded to be longer and a slot was added to adjust the attachment point of the strut. The rear wheels returned to the middle of the wheel wells.

The wheels needed toe-out with the longer trailing arms, within the range of the existing toe-in adjustment. The bottom “A arm” of sorts is the combination of toe adjusting bar and the bottom control arm. The trailing arms have enough play from the bushings that they can rotate to the slightly more longitudinal direction.

The longer trailing arms also resulted in negative camber despite the taller ride height. The lower control arm was swung back from it's forward swept position to be closer to a right angle, but the top A arm remains in its original location.

In order to add camber adjustment, the attachment points for the lower control arm were slotted as well. Now the rear suspension has camber, caster and toe adjustment: an alignment shop's ultimate nightmare.

However, based on the position for -1 degree of camber. I think some camber bolts would have been sufficient. I would have tried that first if it wasn't so impossible to get anything in Peru. Sometimes you get lucky, but you can spend a whole day looking for something with no results. Peru is chaos in so many ways, and I had run out of patience.

YouTube videos on car lift projects

To reduce stress on existing suspension parts with a new configuration, loosen and retighten bolts to relieve stress to the bushings. Bolts should be tightened with the weight of the car on the suspension. Also good to add grease to bolt threads to prevent rust so they don't seize with age.

“It's normal. On my 08, the passenger side front is always a bit higher. I've been on 3 different springs types and 2 different sets of struts. All the same result. only thing the change it would be bags or coils to make it level all around.” 2015 WRX suspension is uneven, nasioc.com

2002-2003 had left and right rear springs?

Before I found out, I got some replacement springs thinking the driver side spring was shot. The $80 replacement springs were supposed to be equivalent to OEM, but disappointingly lowered the front by 2cm. So I left the new one on the passenger side and used the old one from the passenger side on the driver side to even out the height difference.

Part Number: 20204AG011 (or 20204AG01B)

However, my bushings were fine. It ended up being the left strut tower bearing that had gone bad. While everyone says to replace the entire strut cap, a local shop in Peru forced the bearing out and then Frankensteined a new bearing with spot welds to assure retainment.

After driving my car through a thousand miles of rocky mountain hell, I inspected the bearing and it was still smooth. Although the top hat has some lateral play, I don't remember if that's how it started out.

Dimensions for front shock bump stops, part 20321AG011:
Height [mm]: 80.2
Inner Diameter [mm]: 26.2
Width [mm]: 50

Unusual bucking when taking off in first gear, Reddit

Problem getting into reverse gear, nasioc.com

Run with out splash guard? nasioc.com

Same key format used between 2008 and 2014.