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Discussion Starter #1
Okay so I finally found some time to try and get my rear suspension done thinking it would be easier than the front, but it hasn't. I'm using koni yellows and eibach springs and ran into some problems/concerns when assembling it all. After getting the spring compressed on one, I found the top bolt to be stuck and would rotate with the rest of the strut, leading me to take it to a shop to remove the top bolts off both shocks. This caused my first problem as when I went to reassemble the new shock, I didn't have the alternate oem one for reference. Additionally, the koni shocks came with two bolts each (as opposed to the single one holding the oem one together), and neither could screw very far down the shock when I tried to assemble it due to the plastic threading. I didn't know if possibly the smaller of the two would be used to rest underneath the top hat, considering the front shocks had one already on there, but since neither could screw down all the way, I ruled this out. Also, a small white plastic piece was included that I was unsure of what to do with. In the pictures below you'll see that I have the shock assembled, but when installing I found it very difficult to clear the lower metal plate that secures the bottom part of the shock, even with one side unbolted. At this point I was almost certain that I had assembled both shocks incorrectly, and while installing, I also had the spring shift out of center at the bottom, which I found concerning. I feel like the problem is stemming from the top hat not going down more, but I'm really not confident in any of it, though I have no oem shock assembly to confirm my suspicions, so I'm posting here. Lastly, the shock looks to be off center within the spring, but I saw that on both the oem ones when I took them out, so I wasn't too worried about that. Should I use the lower perch instead of the upper, because when I did the front I didn't use the lower perch (though I did use Figs upper control arms) and that dropped the front a good bit. I don't mind some rake but I don't want my car's back end to be super high as it is now. Sorry for the essay lol I just want to avoid any confusion. I feel like I'm missing a few key points and have looked at numerous tutorials but they all give self explanatory steps, such as: "Compress spring, then reassemble strut" etc.. Thanks for any help I just need to get my car off jacks and on the road again.
 

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Discussion Starter #3
Okay so I ordered two strut mounting kits because one of the rubber pieces ripped during the install. Upon arrival I noticed that of the 5 parts included, all seemed to be of good quality. I figured the big rubber ring was to be placed between the spring and hat, and the two other rubber pieces were for the bumpstop and cushion under the metal plate that is secured by the top bolt. However, I don't know where the metal tube is supposed to go and am wondering if this is part of my problem. I'm going to try to reassemble both of the shocks soon and am thinking of moving to the lower perch and using the bolt that was on the oem strut so i can tighten the top hat down more. Any advice?

For reference: 2001-2005 Lexus IS300 Strut Mount - Monroe 905930 - Rear - PartsGeek.com

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First time checking this site in awhile :)

Flip the spring seat. I did the same. Flipping that will clear up a lot of confusion I'm sure.The white/teflon piece for the STR.T were more of a cup. I think that is just a scraper type seal that goes over the piston?

In my case I contacted Koni via email on their website and they were very quick in replying.

See my thread: Need opinions Eibach/Koni STR.T spring seat

I re-used my bump stop as it was still fine. Does yours look like this:
 

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Discussion Starter #5
First time checking this site in awhile :)

Flip the spring seat. I did the same. Flipping that will clear up a lot of confusion I'm sure.The white/teflon piece for the STR.T were more of a cup. I think that is just a scraper type seal that goes over the piston?

In my case I contacted Koni via email on their website and they were very quick in replying.

See my thread: Need opinions Eibach/Koni STR.T spring seat

I re-used my bump stop as it was still fine. Does yours look like this:
Thanks man. But damn, does that mean I had the spring seat on backwards for the front as well? I was driving with the front done for around two weeks with no issues.

Anyways, I’ll try to fix the spring seat on both today. How far down did you bolt your top hat? Did it look similar to mine because I’m confused as to why there’s so much threading on the shock, yet the screw won’t tighten down very far. Also, there’s two of them...

But still, thanks for the spring seat advice man that should resolve most of my concerns.
 

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The front spring seat looked correct. Although I think there should be some thread engagement through the top nut. Did you have to drill the top strut mount like in this thread post #16? Koni Shock installation and help Thread

I had to drill mine just like in the thread above. The STR.T's are not adjustable like the yellows and the assembly for the top strut mount was different. All I had to do was tighten a nut while holding piston with an allen key. Didn't have the barrel nut or the nut on the top of the piston.

Worst case forward those pictures to Koni with your concerns. They were quick to respond in my case.
 

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Don't feel too bad about having the spring seat upside down, its been done before often. Someone had done that on some new Bilsteins I bought cheap because they didn't like them, I only realised what was wrong and why they were sold, when I went to put my own springs on them before installation. If you have a circlip, the spring holder should slip over the top of it holding it in place, if the spring holder is upside down it just sits flat on top of the circlip and the circlip can potentially let go at any time. A shop had done the previous spring installation. Try looking up Google images for a schematic view of the parts and order your unsure of.
 

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Another tip, don't tighten the bolt on the bottom rubber mount of the shock when it is hanging free. Tighten it with the spring compressed the same as when wheel is on and the car is resting on the springs or the rubber mount will be twisted inside the end of the shock when you driving around. It will side load the shocks and shortening the life of the rubber mount.
 

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Discussion Starter #9
Thank you guys for all the advice, thankfully I was able to finish them a day ago. I flipped the spring seat and used the oem bolt so I could tighten them down more. After that they fit in pretty well, though I find it strange still that the rear springs required much less compressing than the front. Regardless of that, I’m just glad the car is driving again. I’m thinking of getting an alignment done maybe at the end of next week.
 

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The front springs are shorter and stiffer than the rears which makes them harder to compress, I had the same trouble, it also depends on the type of spring compressor you use can make it more difficult.
 
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