2.5" coilover sleeves in stock rear location?
 

I want to build a set of coilovers with Koni Yellows. Would it be possible to run 2.5" springs and perches in the rear stock lockation? It looks like every OEM style kit uses a 5 or 5.5" spring, which is harder + more expensive to get perches for.

Yea. Early bc kits came with standard 2.5 dia springs 7 in in length. I had that kit paired with swifts. I believe they still have that option if you upgrade to swift springs as thats swifts standard 60-70mm dia in variable lengths
Just call BC tell them you want to upgrade your standard kit to swift and you need the rear conversion which consist of the gold rear lower hat and the top black hat which has the adjustments on it for ride height. They should sell it to you.

Keep us posted

Did you have any noise issues with that kit? Once I piece everything together I will definitely make a thread.

I did not.

No need to ask- they sell them:

https://store.bcracing-na.com/linear...ter-p5720.aspx

They also sell the collars (at least that's what I think these are):

https://store.bcracing-na.com/rear-h...37x-p4916.aspx

We're in business! So just to price this all out:

Koni Yellows - $1000 (+/-100)
Set of 500/450lb 8Lx2.5"ID springs - $220
Front Koni sleeve kit- $70
Rear BC-Racing 2.5"ID sleeve kit- ~$150

$1440 altogether.... a little rough as Konis for my Hondas were half the price, but it is what it is.

Fortune auto also has a swift upgrade
Maybe price out their rear setup.

Just thinking about it i have an extra pair on 7 inch springs 2.5 dia
12k though.
Lmk ill let em go cheap!

Doesn't look like FA sells the upgrade parts separately. I'm looking to go 9K all around or 9K/8K

So the rears are easy. What are you doing for the fronts?

For the fronts, all 30 series Koni shocks can use a threaded sleeve kit with a special circlip:

Koni 30-0000-0005: Threaded Spring Perch Sleeve For 50mm and 30 Series | JEGS

So the fronts are even easier.

Interested seeing how this ends up, hopefully you can source everything without too much guesswork, definitely a worthwhile project!

Covers the bottom spring perch. What about the top?

Stock top hats. Standard practice for lower end coilovers.
Only real guesswork will be the spring rates; but I think 9K/8K is a pretty safe bet for a mildly lowered street G. I'm at 27.75/27.5 F/R now, and I'm going to run tires that are 26.6" tall all around. I'd like to tuck a little bit so hopefully I'll be at ~1.25-1.5" lower than stock, which combined with the Koni's shortened shafts should make everything line up perfectly. Hopefully I won't even need a camber kit....

Found a pic of your exact plan on a 350z:


https://cimg4.ibsrv.net/gimg/www.myg...a5387e5bf.jpeg

Super interested in this setup myself...

Oooo.... link? Any pics of the rear?

https://my350z.com/forum/autocross-r...i-yellows.html

OP said he had lowering springs in the rear. Also mentioned that the stock top hat needed grinding to avoid making noise/rubbing the spring. And that the springs would unseat during full droop.

I'm thinking a modified tophat and some sort of helper spring would do the trick. On monday I think I will call Koni and verify that your above linked perch/thread does fit the 370/G37 shock body.

Very excite!

I just had another crazy idea. I half did this with my Civic. I got ST coilovers, but the rears blew, so I got Koni Yellows in the back. Well, the Tein Basis has spring rates I want, and all the hardware I need. I'm guessing their front spring is designed to fit snug to the top hat. Only mystery is the difference in the range of adjustment for the Koni vs the Tein front shock.... but we know that the Tein front spring is 225mm, which is not far off from the 8" (203mm) spring I was originally gonna get. Best part is the whole Tein kit is only like $100 more than all the hardware I was gonna get, and I can probably sell the shocks. I'm gonna go that way instead (Tein Basis springs/rear sleeves + Koni Yellow shocks)

Does the tein kit have a linear rear spring as well?

No guarantee you'll be able to use any of the front tein stuff with the koni shock though. The coilover perch you initially linked is for 2.5" ID spring and if the 350z shock is any indicator a smaller diameter spring may not work. Plus the tein tophat may not fit the top of the koni shock. Worse case scenario you can just run the basis as is, but its still a gamble.

The Basis Z uses 2.5" ID springs and the stock top hat, so it should work with this. I'll order a 500lbx2.5IDx9L springs just in case. They're cheap.

Definitely watching this one, my COs have about 75k miles on them so it's time :)

I found a set of old stock Street Advances for $700. Measured my gap again... just need 1.5", which these can do. They have the spring rates I want, and adjustability. If they blow, then I will mess with the Konis. But $700 for these are hard to beat.

Wow, this is definitely interesting. I contacted Koni regarding this exact thing back in March when I was shopping for coilovers. Maybe in the next year or so when I get tired of my Stance XR1, I'll give this setup a shot. I wonder if a true-type rear setup is possible. I'd be sold.

I am not sold on the true style coilover thing. Big reason is I'm pretty sure it kills backspacing clearance. I would just compensate with higher spring rates in the stock location.

Street Advances are no go it looks like, but I did order a set of Basis Zs. Should be here Friday and hopefully I'll be able to install them over the weekend. I'm going to run with them for a while and if I hate them transition over to the Konis.