e46 M3 suspension setup, or how to not downgrade your car with suspension mods

[Obioban]

So how did you get 13.5 front ride height when you were running them?

I machined some spacers to lower the the strut in the camber plate 😜

These days, however, Barry at 3DM makes a lower strut spacer that has the same result.

[lvm3sm46]

So how did you get 13.5 front ride height when you were running them?

[Obioban]

I'm returning to update this, mrgizmo is correct. I tried a 7" 300# spring on Ohlins and it maxed out at 12.75" from fender to hub center. I took that measurement after a 30 mile drive after install so I am going to assume its going to get lower. I think I am going to try 8" next to hopefully get me to 13.5- 14"

Ohlins can’t run that high— you’ll be all bump no droop.

They have exceptionally little total travel (92mm up front IIRC, some of which is bump stop). You pretty much need to set your ride height to optimize bump/droop travel to have them be able to function. If you want to go off that, you need to alter the top or bottom shock mount to match.

[lvm3sm46]

FWIW, Ohlins comes with a 8" 400 front spring and that provides almost an inch drop with stock front mounts.

If you try running a 350 7" spring at 13.5 ride height, you will be almost at the very top of adjustment threads on the collar after preloading the spring appropriately (ride height and spring preload same adjuster).

I tried a 336 7" spring and could not get it to more than barely above 13.25 after maxing out the adjustment collar/preload. The tire rubbed.

Rears at 628 I believe are 6" long (they might be 5", ill need to check).

Sent from my SM-G950U using Tapatalk

I'm returning to update this, mrgizmo is correct. I tried a 7" 300# spring on Ohlins and it maxed out at 12.75" from fender to hub center. I took that measurement after a 30 mile drive after install so I am going to assume its going to get lower. I think I am going to try 8" next to hopefully get me to 13.5- 14"

[Thoglan]

Ohlins spring perches are 65mm-- they work with 65mm or 2.5" springs. GC can sell you upper perches to match. Then you can buy springs from anyone, in 65mm or 2.5".

Just flicked them an email thanks. Presumably the turner perches will fit as well though seeing as both camber plates work with the stock perches?

[puma1824]

I would begin with getting the corner weights of your car, the functional range of travel of your front springs, and the travel of your shocks.

I got the travel of the shocks from Eibach. I need to get functional range & corner weights after all installed. The car is still being assembled.

Metal to metal travel (total shock travel):

• Front: 130.3mm (5.12in)
• Rear: 169.7mm (6.68in

[Obioban]

Thanks so much for the write-up. I have things to learn and need to find a shop that can help set up. I did find out more technical details on my Coilover kit. I wonder if I need to change the spring rates because it's going on an m3 touring conversion. Hmm, where to begin???


PRO-STREET Coilover Kit (Height Adjustable) BMW M3 E46 - Part # 2072.711

Metal to metal travel (total shock travel):

• Front: 130.3mm (5.12in)
• Rear: 169.7mm (6.68in

Spring Size:

• Front: 6” long 400lbs (2.5” I.D)
• Rear 6” long 450lbs (2.5” I.D)

Wheel Specs:

• Offset Front: ET+44
• Offset Rear: ET+27
• Bolt Pattern: 5 x 120
• Factory Setup, Front: 19 x 8.5
• Factory Setup, Rear: 19 x 9.5
• Factory Tire Size, Front: 235/35/19
• Factory Tire Size, Rear: 265/30/19
• Weight, Front: 23.15 lbs (10.5 kg)
• Weight, Rear: 25.02 lbs (11.35 kg)

I would begin with getting the corner weights of your car, the functional range of travel of your front springs, and the travel of your shocks.

[puma1824]

Thanks so much for the write-up. I have things to learn and need to find a shop that can help set up. I did find out more technical details on my Coilover kit. I wonder if I need to change the spring rates because it's going on an m3 touring conversion. Hmm, where to begin???


PRO-STREET Coilover Kit (Height Adjustable) BMW M3 E46 - Part # 2072.711

Metal to metal travel (total shock travel):

• Front: 130.3mm (5.12in)
• Rear: 169.7mm (6.68in

Spring Size:

• Front: 6” long 400lbs (2.5” I.D)
• Rear 6” long 450lbs (2.5” I.D)

Wheel Specs:

• Offset Front: ET+44
• Offset Rear: ET+27
• Bolt Pattern: 5 x 120
• Factory Setup, Front: 19 x 8.5
• Factory Setup, Rear: 19 x 9.5
• Factory Tire Size, Front: 235/35/19
• Factory Tire Size, Rear: 265/30/19
• Weight, Front: 23.15 lbs (10.5 kg)
• Weight, Rear: 25.02 lbs (11.35 kg)

[Obioban]

Looking at converting my ohlins R&T to flat ride while I have them out to rebuild/service. What is the solution for the upper spring perch on the front? For instance if I'm getting a 2.5" spring that wont fit the standard radial bearing on the front (https://www.fcpeuro.com/products/bmw...g-31331090612a) correct? I have ground control street camber plates.

EDIT: just found these: https://www.ecstuning.com/b-turner-m...su4680777~tms/ Presumably they fit my camber plates as well?

Ohlins spring perches are 65mm-- they work with 65mm or 2.5" springs. GC can sell you upper perches to match. Then you can buy springs from anyone, in 65mm or 2.5".

[K-Dawg]

Ground Control camber plates are available with 2.5" spring perches, so maybe they would sell just the perches.

[Thoglan]

Looking at converting my ohlins R&T to flat ride while I have them out to rebuild/service. What is the solution for the upper spring perch on the front? For instance if I'm getting a 2.5" spring that wont fit the standard radial bearing on the front (https://www.fcpeuro.com/products/bmw...g-31331090612a) correct? I have ground control street camber plates.

EDIT: just found these: https://www.ecstuning.com/b-turner-m...su4680777~tms/ Presumably they fit my camber plates as well?

[lvm3sm46]

cobra I added above they are for Ohlins.

The Hyperco springs have a deflection 4.796 with a load of 1438#, outside diameter is 3.465.

As for the Ohlins I keep hearing they dont have much travel.

[cobra]

cobra 2.5 diameter but not really sure if these are considered straight wound or barrel they call them OBD (optimum body diameter) I cant find their travel numbers anywhere .

https://3dmmotorsport.com/collections/hyperco-coilover-springs-2-5-id/products/hyperco-coilover-spring-id-2-5-length-7

Its going to take me some to digest what you are explaining to me.

Those are Hyperco springs. You can email them to find the specifications. They appear to be barrel springs and are only 2.5" at the ends (so more like 3" in the middle). I bet they have quite a bit more travel. So depending on which shock setup you're running you might be able to run the 7" length without issue!

[lvm3sm46]

cobra 2.5 diameter but not really sure if these are considered straight wound or barrel they call them OBD (optimum body diameter) I cant find their travel numbers anywhere .

https://3dmmotorsport.com/collections/hyperco-coilover-springs-2-5-id/products/hyperco-coilover-spring-id-2-5-length-7

Its going to take me some to digest what you are explaining to me.

[cobra]

So 3DM is recommending a 7" spring for the 300 pound rate I want to run in the front. You guys have me worried that it won't get me the travel I need or the recommended height of 13.5.

Anyone have first hand experience with the 7" 300lb spring rate?

What diameter? Barrel or straight wound? You can look up spring specs on the eibach website. They will tell you the travel available before it binds. For example a 2.25" 7" 300lb spring has a travel of 4.32" (https://eibach.com/us/i-409-eibach-coilover-spring.html)

Statically, the front corner sprung weight is 781lbs. With a motion ratio of 0.94 you can estimate that it will compress (781/300)/0.94 or 2.77". This leaves 1.55" left for compression. If your shock has less than that, you're good. If not, it will bind before reaching max compression. I would add a buffer in there of 1/4 to 1/2" because you don't really want to coil bind and this isn't a perfectly exact thing. There will be subtle variations between cars and ride height.

So how do you determine your travel from ride height? It's complicated because part of that travel is in the bump stop. To be perfectly conservative you can consider metal-to-metal travel.

All that said, I am running a 14" ride height and need a 9" spring to not bind. It's okay because it runs inside the wheel. If you run a barrel spring or a 2.5 spring you can run a shorter spring because they have more travel and you might have no choice because otherwise it would rub the tire. There are some options.