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Thread: How To create a rear strut spacer; raise the rear of a B13

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2011-06-26 22:58:19
How To create a rear strut spacer; raise the rear of a B13
First the obligatory warning: I really don’t know what the hell I’m doing. I consulted various knowledgeable people throughout this process, but nobody was with me doing the physical work to say “uh, that doesn’t look right”. I used parts of the car in their non-OEM locations and used the same material in cutting boards in my suspension, so be warned that this could all go horribly wrong. Anybody who follows in my footsteps without using your own judgment and experts is just asking for trouble. I am not, nor will I ever profess to be, an expert. I only have about 100 miles on this set-up, so there's still plenty of time for issues to crop up.

Intro and background research (skip to next section to the How-To if you like):

This How-To was a long time in the making. My B13 Sentra has Hyperco Gen 2 springs combined with CSKs, red in the rear and yellows in front. The result combo was a brilliantly handling DD that could stand up to a few road course track days. But it also resulted in the rear end sag that is common with this setup. I have been told that the fender heights, front and rear, are different and thus create the illusion that there is a sagging rear when there really isn’t. That may be true, but I hated the way it looked and even with 195 width tires I would hit the fenders with the rear tires on hard bumps. Measuring the top of the wheel well to the ground showed a difference of approximately an inch front and back.

My first attempt to fix this was to use a 1” aluminum spacer on top of the rear strut. These were made by Overkill Engineering M and were not drilled correctly, but that wasn’t my biggest problem. Using a top of the strut spacer requires longer studs in the tophat. After seeing ShawnB’s thread on lengthening the front tophat studs, I tried to do the same in with the rear, but the tophat was welded together making the removal of the OEM studs very difficult. It would either require welding to cut out the OEM bolts and to put in the new studs, or drilling holes in the bottom of the upper spring perch to be able to push the OEM studs out and get the new ones in. That was more work than I had anticipated. The next few ideas included using a spacer in the spring itself or between the spring and spring perch, such as the following links:

AFCO Adjustable Coil Spring Spacer - Speedway Motors, America's Oldest Speed Shop
Rubber Coil Spring Spacer - Speedway Motors, America's Oldest Speed Shop

But the energy suspension ones wouldn’t fit OEM spring dimensions and the other two seemed iffy. Plus, I’m not too sure they would actually raise ride height as much as they would increase spring rates by compressing the spring even more. Then I fell on the ideal solution… if I had a truck:
Amazon.com: Daystar KF09115BK Comfort Ride 1" Leveling Front Strut Spacer Kit: Automotive
These were the right material and included “stud-extenders”, which would have been ideal as there would be no need to remove the tophat. But Daystar wouldn’t tell me the specs on their products to see if I could use one of their kits on my car. I tried to find stud-extenders on my own, such as these (McMaster-Carr), but I couldn’t find the right size with a 6M female thread.

I should also mention here that some very knowledgeable forum members have corrected the hyperco stance by cutting one of the dead coils off their front hyperco springs with apparently no ill-effects. I decided not to do this as it would further lower the front and I was already having enough problems scraping speed bumps with my Lower Control Arm Brace. So for me, further lowering the front to resemble the stance at the rear was not an option for me.

Finally, I found several threads on Subaru forums about creating their own spacers for their cars, such as this one: DIY: Strut spacer lift templates! - Subaru Outback - Subaru Outback Forums. I decided to go this route, while also attempting to use the front tophats from a B13 on the rear of the car so I could remove the studs. I got the front tophats from a part-out and I got the spacer material as recommended in the Subaru threads, HDPE. I decided on ¾” HDPE for my spacer. I ordered it from here: Polyethylene HDPE LDPE Sheet | Industrial Plastic Supply, Inc.. I got a 12x12 sheet, which was enough to cut out at least 5 spacers. It cost $20 for the sheet and $13 to ship it regular UPS. When browsing that page, beware as there is both HPDE and LDPE products listed. I’m not sure what the difference is but all the threads I saw specifically recommended HPDE, so that’s what I went with.

Here are picture comparisons of the front and rear tophats with the fronts on the right:

Parts I used:
1 12x 12 sheet of HPDE of ¾” thickness (Polyethylene HDPE LDPE Sheet | Industrial Plastic Supply, Inc.)
2 front tophats from an NX2000. I’ve heard any B13 would do, but I can’t confirm that.
6 grade 8 2” 5/16th bolts, with corresponding nuts, washers, and lock washers

12mm socket and box wrench for the strut tower bolts
17mm socket and box wrench for lower strut bolts
19mm off-set wrench and allen wrench to the top strut nut (for Koni red strut)
Jack and jackstands
Impact wrench
Spring compressors and corresponding impact socket
Drill and drill bits for the HPDE
Jigsaw for the HPDE
Tools to adjust rear sway bar (if necessary)

The How To:
First, determine how wide of a spacer you wish you use. I measured from the ground to the top of the wheel arch through the center of the wheel (front then rear pics):

My front was at 23 ¾” and the rear at 22 5/8”, a difference of nearly an inch. Therefore I decided to try a ¾” spacer. If I had it to do over again, I would measure the car at rest, and then jack the rear up 3/4" to see how I liked the stance. This might be a decent way to estimate the possible resulting stance and to make a more informed decision as to what size spacer to use.

Jack up the rear of the car and secure it with jackstands. Remove wheels.
Remove brake line from strut.
Remove rear seat and use 12mm socket and box wrench to remove the 6 OEM nuts on top of the strut tower.
Use impact wrench (or breaker bar) and 17mm impact socket to remove the two lower strut bolts that attach it to the spindle.
Remove the strut/spring assembly.
Use spring compressors to relieve spring pressure off the top hat. Use 19mm off-set wrench and allen wrench to remove the nut on top of the strut (this is on a Koni red), and remove tophat.

Creating the spacers:
Disassemble the extra front tophats.
Initially I made a full template of the upper portion of the tophat (as seen below), but I found it would simply be easier to make a circle out of cardboard to replicate the black metal center of the tophat that rises above the studs and use that to draw the cutting line on the HDPE (ensuring enough space around it for the rest of the spacer.

I used a large drill bit to make a starter circle inside the circle to be cut as a way to get the jigsaw in the middle.

I then cut out that middle circle.
By placing the inverted tophat top piece into the cut circle, it made it easy to drill the stud holes in the HPDE, then putting in the studs to secure it in the HDPE to trace the outline of the tophat.

Cut along your outline and you have one ready to go spacer! Repeat for the other tophat and confirm fitment.

Here it is test-fitted:

While test fitting, note and mark on the spacer which side points towards the front of the car. This will be important during the installation of the reassembled strut/spring as it may spin on you.

Upgrading the top hat studs:
First review ShawnB’s excellent write-up on this : http://www.sr20-forum.com/suspension-brakes-tech/13941-how-upgrade-your-oem-strut-mount-studs.html
Use a hammer to back out the OEM studs from the “Strut mounting insulator” #54322 in the following image.

For my ¾” spacer, I determined that a 2” long bolt was sufficient for my purposes. I went grade 8 since the spacer would mean that only the bolts would take all of the strain as the metal black cap that normally fits into the strut tower middle hole would now be well below that hole. Make sure the head of the bolt is narrow enough to not rub the upper spring perch once the tophat is reassembled. Also note that with a 2” long bolt on the end, getting the reassembled strut/spring unit back into position in the wheel well was difficult, a 2 ½” bolt would have made it very difficult.
Using 5/16th bolts, retapping was not necessary. I had my bolts welded into place in the strut mounting insulator for $10 by a local welder.

Reassemble the tophat. I cleaned up the tophat before putting it back together and put some white lithium grease in the areas that rotate. I don’t think those pieces will ever rotate in the back, but I also don’t want them making noise. Here’s the finished product:

It is the reverse of disassembly. Ensure that the little arrow on the top of the upper spring perch is pointing out towards the mounting bracket the strut uses to mount to the spindle:

Torque the top strut bolt to spec and remove the spring compressors.

The longer stud bolts made wedging the assembled unit back into place in the wheel well pretty difficult. The addition of the spinning portion of the tophat to the process made it pretty difficult to do without help. I eventually carefully let the assembly rest upright on the parallel link and then used a jack on the rear spindle to slowly move the strut up. With the strut bolts almost hitting the strut tower, I was able to align tophat studs and use the jack to push them through the strut tower. Once I got a nut on each stud, I released the jack and aligned the lower portion of the strut into the mounting points on the rear spindle. With the strut sitting ¾” lower, getting it aligned was a bit more difficult, but it eventually fell into place. I got the 17mm strut bolts in and torqued, then I added a washer, lock washer, and nut to the tophat studs on top of the strut tower and tightened it all down to spec.

I noticed that with the height difference, my Progress rear sway bar was now hitting the parallel link, so I adjusted the heim link out a bit and checked for binding/contact. This may or may not be applicable to you.

Reinstall rear tires, put the car back on the ground and look to make sure everything is secure and tightened to spec. Take a few easy test drives without the back seat to listen for clunking and to ensure that the spacer has not moved or had any other issues.

Here are my before and after measurements, measuring from the floor to the top of the wheel arch through the center of the wheel:
Before: 23 ¾”
After: 23 5/8”

Before: 22 5/8”
After: 23 3/8”

After front:

After rear:

Before rear:

After rear:

New stance:

More new stance images. I wanted to get both sides but I didn't have a lot of room on the driver's side to take the pic so please forgive the wacky shot. Hopefully you can see enough of the tire to fender gap for the pics to be useful.

So far I have flogged it on about 50 miles of very twisty backroads and it handles pretty much the same as before. I am getting no noise in the back, either mid-corner or on hard bumps. And in the few places I had been scraping my STi muffler prior to the spacer install, I have not yet scraped with this new stance. I’m not going to win any Hella-Flush awards, but now the rear pretty closely matches the front and that makes me happy. Thanks to Ameen, BenFenner, and Vadim, among many others, who helped me during this process.
Last edited by Isfahan on 2011-07-08 at 00-54-31. Reason: Added a few more random thoughts after chewing the cud for a bit.
2011-06-27 17:49:19
Very cool. Guess I'll cross post this here. Maybe the mods can take it out of the H&R/AGX thread if they want.

I had this idea and i even got the top hats but never got time to implement it and I didn't have it all worked out like you do.

Would probably want to use oem bolts up top I guess they are castle nuts but I think the hardware and the welds are good.

Looks really well thought out. Also can you get some pics up like in late afternoon or morning. Its hard to see the gap with those high noon pictures. I do the same thing all the time too when I'm taking pics.

The Hyperco gen 1s had the worst saggy but problem imo, but the Forester is notorious for even having it stock. I used shorter tires to help but several compaines offer a similar spacer for lifts and visually evening out the drop. Perfectly safe. Usually they are billet aluminum iirc because it won't crack or deflect under load.
2011-06-27 17:55:46
Yeah, I will try to get a better pic or two this evening, especially now that the car is washed! I had billet aluminum spacers made initially, but I decided not to go with them because I was afraid they would make more noise and the HPDE will conform a bit so I thought it might have a snugger fit. It seems like the HPDE is pretty tough and resilient, it can withstand at least 2700psi of compressive force. Hopefully it holds up.

As to the OEM bolts, I'm not sure which ones you are referring to? The OEM studs are nowhere near long enough to fit with a spacer. And I don't think the welds on the new tophat studs do anything but prevent the bolt from spinning when tightening the nut on top of the strut tower. I also don't think the OEM studs are grade 8, but that is a pure assumption on my part.
2011-06-27 18:01:00
the oem nuts have that wider seat on them you know?

The SE-R is really looking pretty good too man.
2011-06-27 18:31:53
I get it now. The new hardware I put in was 5/16th's standard, so the OEM 6M nuts would not have fit.
2011-06-28 13:22:48
when u first posted about this, i thought you were trying to put the top piece on the rear spring part. now i understand you used the whole frt part top and spring part in the rear. funny thing is if you have a progress style rear bar and csks. this mean you can use all frt strut housings and hats lol.

great job. i think your trick and the one i'm working on. even the flamed lowering springs will work better on our cars now.
2011-06-28 16:51:02
I'm not sure I understand what you mean? I used the entire front tophat in place of the rear tophat in this project. The spring and strut were the same for the rear, both before and after. I just replaced the parts directly above the spring. And I'm not sure why someone would want to use the "flamed" lowering springs in conjunction with this spacer? This spacer does not give you any more suspension travel, so springs that are too short and too soft will still crash against the bumpstop just as often and would diminish the life of the strut just as quickly. However, this spacer will ruin the stance that most people try for when using lowering springs.
2011-06-29 16:24:41
i'm just saying. if you were building csk's and have a prorgress rear bar, and using a rm or hyperco spring there would be no need to try and find rear strut housings and tops. cause to get rid of the reverse rake and do your trick you only need frt strut parts.

and i was just saying with extended travel top hats like i'm planing h&r's eibachs etc would be more bearable.
2011-07-02 04:18:07
Added some more stance pics at the end of the How-to post. Hopefully the lighting is a bit better to see the stance. That's with backseat and various tools in the car, and with a full tank. It still sits a little back, I probably could have gone a full inch with the spacer, but I think it looks so much better and the scraping with the muffler is very much reduced!
2011-07-03 20:38:23
nice. i have actually been planning something like this for my g so i can get about 5/8" to 3/4" higher for tire clearance. just like you i have been looking at the truck style spacers but all are usually an inch longer or more so it would be higher than oem. i think this with something like a flat top mount type piece would add shock travel like these do:
custom upper shock mounts = more suspension travel for lowered cars - G20.net - Forums

Note for those who dont know: these are for a G20 front which is not a strut design like the B Chassis, Originally designed by MEP, Current production by DMSentra who also does the rears, i have a set and they are a great upgrade and are similar to Ground Control top hats.
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