Spring lengths/ custom coilovers

[hopeful]

I bought the custom coilover DIY kit from IE. long story but I can't get a response from them about spring lengths.

https://www.iemotorsport.com/product/rear-adjustable-height-spring-perches-e30/

https://www.iemotorsport.com/product/front-coilover-kit-e30/

Does anyone know what the front and rear spring lengths should be? I intend to use IRP front camber plates and am pretty certain for b8's up front and was thinking about the adjustable mustang shock for the rear. I also plan on running style 5's with spacers.

This is for a sedan that barely gets driven, I would like to start taking it to lapping events in the few months of summer we get and weekend drives. I think I've got a rough idea of what I want for rates but am not certain. Was thinking 450 out back and 650 upfront (I see eibach Canada let's you order direct from them). I can't see a better shock than the b8 upfront as nothing else is inverted, although I like adjustability.

[hopeful]

I also need a solution that allows the top spring perch to rotate, saw that BC sells this piece individually but I don't know if the shock diameter matches

[hopeful]

https://www.tcklineracing.com/webdocs/Items/Details177.cfm

So I was not aware there was a double adjustable shock available for the e30. I came across this Koni race shock that seems to do it. Anyone know which shock it is tck is using for the front? The rear seems rebound adjustable only?

[hopeful]

https://www.koni-na.com/en-US/NorthAmerica/Products/Accessories/Race-Double/

So apparently the double adjustable is called their 8611 series, I don't know the dimensions of the OE strut, 51mm ID? Depth?

[Northern]

large diameter strut housings are 51mm OD, something like 45mm ID. 45mm and 43.5mm koni inserts work.
Bilstein 325iX B6/HD will work in a shortened RWD 51mm strut housing, but the iX valving is way softer than RWD, so ideally you'd get them re-valved. For whatever reason, the Koni iX inserts don't seem to be that way.

For spring/strut rotation, you can also use a thrust bearing that matches the spring diameter and have it sit directly above the spring.
Depending on thickness of the thrust washer stackup, this could cause issues with how the spring sits on the seat, so you may need additional parts like a helper spring adapter.

I have 5" 450lb springs front, 4.5" 650lb springs rear from the GE Group buy back in 2013ish. 1" sectioned from the strut housings seems to be low but functional.

https://www.r3vlimited.com/board/forum/e30-classified-forums/retail-classifieds/251964-german-engineering-coilovers

If you don't want to go super low, you could do a 5" in the rear on a late model and probably be fine. I just say this because I don't know how common the 4.5" length is.
6" would work in the front, but assuming you section more from the strut to match, lower adjustments will be close to touching the tire.

[hopeful]

large diameter strut housings are 51mm OD, something like 45mm ID. 45mm and 43.5mm koni inserts work.
Bilstein 325iX B6/HD will work in a shortened RWD 51mm strut housing, but the iX valving is way softer than RWD, so ideally you'd get them re-valved. For whatever reason, the Koni iX inserts don't seem to be that way.

For spring/strut rotation, you can also use a thrust bearing that matches the spring diameter and have it sit directly above the spring.
Depending on thickness of the thrust washer stackup, this could cause issues with how the spring sits on the seat, so you may need additional parts like a helper spring adapter.

I have 5" 450lb springs front, 4.5" 650lb springs rear from the GE Group buy back in 2013ish. 1" sectioned from the strut housings seems to be low but functional.

https://www.r3vlimited.com/board/forum/e30-classified-forums/retail-classifieds/251964-german-engineering-coilovers

If you don't want to go super low, you could do a 5" in the rear on a late model and probably be fine. I just say this because I don't know how common the 4.5" length is.
6" would work in the front, but assuming you section more from the strut to match, lower adjustments will be close to touching the tire.

Thanks for the help, since I last posted I did find quite a bit of information all in different posts, much of it from yourself.

Sad to hear that about the Bilstein iX inserts as I thought I'd figured it out. The DA konis are $600 each for the front,, cost prohibitive. I read on a Porsche forum last night about Elephant racing in Vaughan offering Bilstein revalving in house. I'll give them a call today and see what it would cost with the IX inserts as I'd still prefer these to anything else due to the inversion.

I saw those spring bearings, I think I still want a bearing that fits into the perch that goes at the top. I'm sure either works work I just feel the latter is a more traditional method.

[hopeful]

large diameter strut housings are 51mm OD, something like 45mm ID. 45mm and 43.5mm koni inserts work.
Bilstein 325iX B6/HD will work in a shortened RWD 51mm strut housing, but the iX valving is way softer than RWD, so ideally you'd get them re-valved. For whatever reason, the Koni iX inserts don't seem to be that way.

For spring/strut rotation, you can also use a thrust bearing that matches the spring diameter and have it sit directly above the spring.
Depending on thickness of the thrust washer stackup, this could cause issues with how the spring sits on the seat, so you may need additional parts like a helper spring adapter.

I have 5" 450lb springs front, 4.5" 650lb springs rear from the GE Group buy back in 2013ish. 1" sectioned from the strut housings seems to be low but functional.

https://www.r3vlimited.com/board/forum/e30-classified-forums/retail-classifieds/251964-german-engineering-coilovers

If you don't want to go super low, you could do a 5" in the rear on a late model and probably be fine. I just say this because I don't know how common the 4.5" length is.
6" would work in the front, but assuming you section more from the strut to match, lower adjustments will be close to touching the tire.

I've got yet another question for you, how much room does the 4.5 rear spring leave? And in the front, what is the longest total length possible? I'm wondering if I can run eibach tender springs in addition to the 2.5 up front and 2.25 outback, just wondering what I can do before I start taking everything apart. Also I think I will just go with the torsion release bearing as you mentioned.

I'm probably over thinking it, but just thinking if I can run a softer tender spring it would help for comfort. Thoughts? My wheel setup will be style 5s on spacers, 10 and 15mm. I really want this thing to handle well.

[Northern]

I've got yet another question for you, how much room does the 4.5 rear spring leave? And in the front, what is the longest total length possible? I'm wondering if I can run eibach tender springs in addition to the 2.5 up front and 2.25 outback, just wondering what I can do before I start taking everything apart. Also I think I will just go with the torsion release bearing as you mentioned.

I'm probably over thinking it, but just thinking if I can run a softer tender spring it would help for comfort. Thoughts? My wheel setup will be style 5s on spacers, 10 and 15mm. I really want this thing to handle well.

Front: Longest I'd go is 6", but it could limit your ability to go low depending on front tire width/how close it is to hitting.


The rear springs in this setup were done so you can tuck an early car with high rear arches. Tender springs shouldn't affect spring rate because they should be fully compressed unless the car is off the ground.

That said, running a shorter rear shock usually limits the travel of the rear spring anyway, so there's not really a point to running a helper/tender in the rear unless you're on stock length shocks and really want the spring to not be loose when you jack the car up.