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

[tlow98]

i talked with TC a while back when I was considering 700 rear, and he told me his SA’s would not support 700#. Maybe he’s made some changes?

Thanks for the heads-up. That's probably ok in my situation, anyway. As Obioban pointed out my car is lighter anyway.

[Tbonem3]

A lighter car would need a damper capable of GREATER rebound, not less fyi.

More vehicle weight effectively reduces spring rate.

[Obioban]

A lighter car would need a damper capable of GREATER rebound, not less fyi.

More vehicle weight effectively reduces spring rate.

I read his post as he can get away with a 600 lb spring instead of 700.

[D-O]

I spoke with TC recently and he was adamant that the fronts would require camber plates. He seems unaware that there is a hack to run the E36 hats.

He really stressed the need to not go too stiff in the rear as it would inhibit putting the power down when exiting a corner. He said "you can do almost anything you want with the front, but you have to be very careful in the rear."

Jesse

[Tbonem3]

Esp true if you have a bigger rear sway bar AND/OR if you've gutted the rear, which is much easier to do than the front.

[D-O]

Esp true if you have a bigger rear sway bar AND/OR if you've gutted the rear, which is much easier to do than the front.

Indeed. He did mention that they often go with no rear sway on their track cars.

Jesse

[tlow98]

I spoke with TC recently and he was adamant that the fronts would require camber plates. He seems unaware that there is a hack to run the E36 hats.

He really stressed the need to not go too stiff in the rear as it would inhibit putting the power down when exiting a corner. He said "you can do almost anything you want with the front, but you have to be very careful in the rear."

Jesse

Interesting stuff, thank you. I could have sworn TC used to sell their SA kit sans Camber plates for $1800-1900. Maybe I'm delusional.

[Thoglan]

I made an interesting observation on my setup with ohlins w/ standard ohlins springs, 3DM strut spacers and GC Street Camber plates. Current ride height at the front is even lower than recommended at ~13.25" hub to fender and my bump:droop is still off, at about 40.5mm bump:52mm droop. Which is about 44:56 in terms of % of total travel. This means to reach the proper bump travel (approx 60% according to this thread) my ride height would have to be about 12.8" hub to fender. At what point is the trade off in height not worth it for achieving enough bump? Additionally, for those who have swapped out the standard ohlins springs for shorter/lower spring rate springs, how did you get anywhere close to proper bump travel without completely slamming the front? I would assume a shorter spring and a lower rate would put the ratio even further out than it already is unless I'm missing something.

My car is a euro spec M3 if that makes a difference. I have read the uprights are different?

[Obioban]

I made an interesting observation on my setup with ohlins w/ standard ohlins springs, 3DM strut spacers and GC Street Camber plates. Current ride height at the front is even lower than recommended at ~13.25" hub to fender and my bump:droop is still off, at about 40.5mm bump:52mm droop. Which is about 44:56 in terms of % of total travel. This means to reach the proper bump travel (approx 60% according to this thread) my ride height would have to be about 12.8" hub to fender. At what point is the trade off in height not worth it for achieving enough bump? Additionally, for those who have swapped out the standard ohlins springs for shorter/lower spring rate springs, how did you get anywhere close to proper bump travel without completely slamming the front? I would assume a shorter spring and a lower rate would put the ratio even further out than it already is unless I'm missing something.

My car is a euro spec M3 if that makes a difference. I have read the uprights are different?

The 3DM strut spacers are for US cars only-- they correct for the difference in the uprights with US cars. If you took them out, you should be able to be back in optimal bump/droop at a reasonable ride height. That said, for more bump travel (less droop), you'd want to raise your car.

[Obioban]

Interesting stuff, thank you. I could have sworn TC used to sell their SA kit sans Camber plates for $1800-1900. Maybe I'm delusional.

They did.

You can still piece it together, since they sell all the components individually, as well.

[repoman89]

I made an interesting observation on my setup with ohlins w/ standard ohlins springs, 3DM strut spacers and GC Street Camber plates. Current ride height at the front is even lower than recommended at ~13.25" hub to fender and my bump:droop is still off, at about 40.5mm bump:52mm droop. Which is about 44:56 in terms of % of total travel. This means to reach the proper bump travel (approx 60% according to this thread) my ride height would have to be about 12.8" hub to fender. At what point is the trade off in height not worth it for achieving enough bump? Additionally, for those who have swapped out the standard ohlins springs for shorter/lower spring rate springs, how did you get anywhere close to proper bump travel without completely slamming the front? I would assume a shorter spring and a lower rate would put the ratio even further out than it already is unless I'm missing something.

My car is a euro spec M3 if that makes a difference. I have read the uprights are different?

Maybe it’s too early to be thinking about this, but don’t you want to raise your ride height to gain bump travel and decrease droop travel? For example if you went to 13.75” hub to fender you’d gain about 13mm of bump travel at the expense of 13mm in droop travel. And the lower you go the less bump travel you have, up to the limit of riding on the bump stops all the time at like 11.5” (not that it’s necessarily possible to achieve that)

[Thoglan]

repoman89 Oh, yes it's possible I have it backwards lol. Embarrassing. I'll have to play around with ride height and see what happens to the droop.

[cobra]

Can anyone comment a little more on bump/droop travel? I am looking at fitting some shocks and it might change the ratio in the rear. As a reference, my Koni shocks have 228mm of metal-to-metal travel and measure 600mm from the lower mounting bolt to the shoulder on the shaft. Some quick measurements shows that with Dinan springs, it is sitting about 40% into its travel statically, which is exactly what the OP suggests as a target. It also has 137mm of travel beyond that point, not counting the bump stop, which is significantly more than the 50mm in the OP.

Obioban, was the 50mm bump travel until it hits the bump stop or actual shock stroke?

If I fit the shorter shocks I'm looking at, it will affect the ratio. If I want the total compressed length to be the same (knowing this doesn't cause any rubbing/interference issues), I might end up with a 35/65% split instead. Thanks!

[Obioban]

Can anyone comment a little more on bump/droop travel? I am looking at fitting some shocks and it might change the ratio in the rear. As a reference, my Koni shocks have 228mm of metal-to-metal travel and measure 600mm from the lower mounting bolt to the shoulder on the shaft. Some quick measurements shows that with Dinan springs, it is sitting about 40% into its travel statically, which is exactly what the OP suggests as a target. It also has 137mm of travel beyond that point, not counting the bump stop, which is significantly more than the 50mm in the OP.

Obioban, was the 50mm bump travel until it hits the bump stop or actual shock stroke?

If I fit the shorter shocks I'm looking at, it will affect the ratio. If I want the total compressed length to be the same (knowing this doesn't cause any rubbing/interference issues), I might end up with a 35/65% split instead. Thanks!

The 60:40 is a ballpark range, but that 60 is partially bump stop. Ideally, you want a good amount of travel before the bump stop engages, as the bump stop functions as another (and progressive) spring-- so when you're in the bump stop, spring rate increases, grip decreases.

The 50mm I meant as the bare minimum. Some shocks have WAY less then the 228mm of your Konis. E.g. my old Ohlins had 92.5mm of front metal to metal travel. The less you have, the more critical it is optimize the use of it. The Konis have so much that the 60:40 really isn't that critical to focus on-- unless you do something extreme, you're unlikely to be outside of it.

What shocks are you thinking about moving to?

[cobra]

The 60:40 is a ballpark range, but that 60 is partially bump stop. Ideally, you want a good amount of travel before the bump stop engages, as the bump stop functions as another (and progressive) spring-- so when you're in the bump stop, spring rate increases, grip decreases.

The 50mm I meant as the bare minimum. Some shocks have WAY less then the 228mm of your Konis. E.g. my old Ohlins had 92.5mm of front metal to metal travel. The less you have, the more critical it is optimize the use of it. The Konis have so much that the 60:40 really isn't that critical to focus on-- unless you do something extreme, you're unlikely to be outside of it.

What shocks are you thinking about moving to?

Ok gotcha. Seems to me like relying too much on the bump stop is bad for performance. Maybe it's good for making a car that feels comfortable traveling in a straight line, and still hold it up when cornering, allowing OEM's can use soft spring rates while keeping a sporty feeling?

Wow, 92.5mm up front is short! My front Konis have 143mm metal-to-metal up front. I haven't taken any measurements about how far in it sits statically yet, but will post it up here when I do.

I know for the rears, when I lift the rear of the car in the air, the wheels droop a LOT. I can't imagine them ever getting that far down while cornering. Any more, and the spring starts to gets loose. So it's very possible I can reduce that droop travel and still never reach it because the shock has so much travel. I will try to do my best to maintain the same amount of bump travel so it's not bottoming out on rough roads.

The shocks will be custom with triple-adjustable piggyback monotubes - I will share more as I get closer. Right now I'm just in the measuring stage.