Rear integrated coilovers

[Naebdyret86]

Hi everybody.



I just purchased a D-BM-12-STREET D2 coilover kit for my e30 90' 325i



This setup have rear integrated coilovers instead of the traditional springs in the rear subframe.



And now i have been wondering... "there might be a manuel in the coilover case that explains this" but i havent recieved them yet, so... Am i suppose to remove the original springs in the subframe and only use this new coilvers, and just leave the spot empty in the subframe? Or do you still have the springs in? My own guess would ofc be to remove all the original stuff, and run the new coilovers only. But just to be sure, since i have had a hard time finding the answer online Google/youtube ect. I just wanted to ask in here :) Hope someone can get me clear on this.


Best regards Andy

[nrubenstein]

Yes, you are supposed to remove the stock spring.

Note that the E30 shock towers are lightly held in by some spot welds and are prone to fatigue failure.

My recommendation would be to return the kit and get one with the spring in the stock location. There’s no benefit to running a “true” rear coilover in a street car.

[Motheye99]

I've never installed true rear coils like you have. However in my research they replace the standerd spring. Did it include a relocation mount for the bottom of the coil over? Also are you adding and reinforcement's to the shock tower? Your going to punch a whole in your trunk if you're no carful.

[ForcedFirebird]

I agree with nrubenstein.

We have them on one of the endurance cars, been running 3 yrs without an shock tower reinforcement. Also have a client we swapped an m52 for him, he had them on his street car for several years without issues, but not a bad idea to add extra reinforcement.

On another note, the guy owner of the race car that has them is having trouble with spring rates. Most of the kits are sold with similar rates that a divorced spring setup would need. We are having over steer issues with them.

[Naebdyret86]

Aha, i didn think of reinforcements, but now i do deffiently, i would look into some reinforcements.. any recommendations? vids or so? or are we just talking stuff like this? https://store.garagistic.com/bmw-rea...-reinforcement



Well the car are gonna see some trackdays and some drifting, and i just wanted it to be different for the handling and looks :)



And hence to the bottom of the rear coilover, i guess it just fits like a standard damper? I know the front needs welding ofc.

[nrubenstein]

Aha, i didn think of reinforcements, but now i do deffiently, i would look into some reinforcements.. any recommendations? vids or so? or are we just talking stuff like this? https://store.garagistic.com/bmw-rea...-reinforcement



Well the car are gonna see some trackdays and some drifting, and i just wanted it to be different for the handling and looks :)



And hence to the bottom of the rear coilover, i guess it just fits like a standard damper? I know the front needs welding ofc.

There is no meaningful difference in handling unless you also modify the trailing arms to the point where it’s no longer possible to put a spring on them.

[Naebdyret86]

There is no meaningful difference in handling unless you also modify the trailing arms to the point where it’s no longer possible to put a spring on them.

but anyways ;D they are ordered and on there way, i just think the looks kinda stand out, and really just wanted to try it for myself. i got an old bilstein suspension on it since my kw 1 coilovers gave up, so i think its gonna make a lot of difference.


i that the kinda reinforcement you were talking bout?

[Motheye99]

Aha, i didn think of reinforcements, but now i do deffiently, i would look into some reinforcements.. any recommendations? vids or so? or are we just talking stuff like this? https://store.garagistic.com/bmw-rea...-reinforcement



Well the car are gonna see some trackdays and some drifting, and i just wanted it to be different for the handling and looks :)



And hence to the bottom of the rear coilover, i guess it just fits like a standard damper? I know the front needs welding ofc.

If you do go with a true coilover, and you plan on drifting the car. Serious reinforcement needs to be done. Look at the DTM E30 M3. They had true rear coils and tied the rear strut mount into the cage and had serious steel. Remember the rear shocks on stock E30'S doesn't take the whole load of the car. The spring does. True coilover stress the rear strut tower 100's of lbs more than stock. Mind you these rear towers are a weak point stock.

Tldr: your going to break shit fast if you don't seriously reinforce the strut

[e30davie]

having the spring attached where the shock attaches would be more lever arm for the spring, you can use a softer spring and your spring gets more travel. Could be seen as an advantage i guess. heck of a lot of work though to reinforce when you could just slap in some normal springs in the normal spot for basically the same effect.

here is some delicious DTM things,

http://www.m3motorsport.co.nz/#!/products/suspension-and-steering/dtm-rear-suspension

20k and you still dont get the rear shock towers reinforced. i suppose the idea is if you are going down this route you are tying your roll cage into the rear suspension.

[Andre3127]

Can someone please inform me as to why people want a true coilover setup? Divorced or coilover, they do the same job.

[AndrewBird]

See here:

https://www.masonengineering.net/products/bmw.php?bmw_id=e30

[earthwormjim]

Can someone please inform me as to why people want a true coilover setup? Divorced or coilover, they do the same job.

Due to the leverage disadvantage with the stock location, you need seriously high rear spring rates if you're also running even moderately high spring rates in the front. 600# springs in the front, might need 1200# springs or higher in the rear to have a balanced set up. That's a lot of stress on the trailing arm and subframe mounts. Trailing arms are already known to fail with stock parts, hence the reinforcement welding mods that are quite popular. The wedging force that is applied to the mounts is lessened the further out you can mount the spring.



With a coilover, you do not need anywhere near as high of a spring rate, to get the same effective spring rate felt by the wheel. However, I would think reinforcing the shock tower would be critical to be able to run the spring rates that would warrant this conversion in the first place. If you're keeping relatively low spring rates, than there's little point in doing the conversion.

You can also probably gain some suspension travel.

[ForcedFirebird]

600# springs in the front, might need 1200# springs or higher in the rear to have a balanced set up.

2:1 is not a normal ratio for a divorced setup (should be closer to 1.3:1), but you are correct in the spring rate being closer to 1:1 with true coils.