Cobra's Custom Shock Project

[L0okitzRaj]

blessing us with more info! Thanks!

Also, thanks for helping with the v3s. They ride amazing, as enjoy_m3 said!

[heinzboehmer]

Super cool project and very interesting info on the different shock types. I'm very surprised at how little travel the konis have. Mine do seem to be crashy over bumps (running koni + eibach pro kit springs). Should probably look into that. Shorter bump stops (not ideal, but better than what is on there now) and shorter camber plates should help.

Out of curiosity, how did you measure travel when driving? Linear displacement sensors and a microcontroller or something fancier?

[cobra]

Super cool project and very interesting info on the different shock types. I'm very surprised at how little travel the konis have. Mine do seem to be crashy over bumps (running koni + eibach pro kit springs). Should probably look into that. Shorter bump stops (not ideal, but better than what is on there now) and shorter camber plates should help.

Out of curiosity, how did you measure travel when driving? Linear displacement sensors and a microcontroller or something fancier?

Yeah, it's pretty eye opening to realize how the suspension sits relative to the bump stops. The bump stops I've seen are gradual but ramp up in force very progressively, so you can't necessarily tell when you hit them. I would say anyone who is running the Konis to get camber plates to get some bump travel back, or raise it up. Shorter bump stops will help but when you hit them it will be more of a dramatic change, and could cause some unwieldy handling.

Data logger. I am using the generic kit which is not mountain-bike specific. It's OK, not the best, and has some bluetooth dropouts, but it gets me useful data.

https://motioninstruments.com/

[Bry5on]

This is the best thread. I’m the one who spaced up my dinan springs for exactly this reason. I also feel that the konis have too much high speed compression damping and have been looking into alternative options to correct that. Sounds like you headed down the same path, for I’m guessing similar reasons.

Also, it looks like KW really hit the mark on maximizing the travel window on lowered cars. Well done.

Last, you mentioned mountain biking. We should meet, check my avatar photo I’m in Berkeley, we can invite Heinz too and scheme up some good projects..

[cobra]

This is the best thread. I’m the one who spaced up my dinan springs for exactly this reason. I also feel that the konis have too much high speed compression damping and have been looking into alternative options to correct that. Sounds like you headed down the same path, for I’m guessing similar reasons.

Also, it looks like KW really hit the mark on maximizing the travel window on lowered cars. Well done.

Last, you mentioned mountain biking. We should meet, check my avatar photo I’m in Berkeley, we can invite Heinz too and scheme up some good projects..

Hell yeah! I don't currently ride mountain but want to get back into it soon.

I had forgotten it was you who raised up their Dinan springs. That's definitely a good idea.

The Konis have almost no high speed compression damping. The fronts blow off around 4 in/s at 125lbs, and are only making 150lbs at 20 in/s. The rears are even less, blowing off at 50lbs and still only making 100lbs at 20in/s. Of course, these are my Konis with 30k miles on them, but still. I bet a fresh set isn't far off. What you're probably feeling is harshness due to lack of control and then bottoming.

[Bry5on]

Hell yeah! I don't currently ride mountain but want to get back into it soon.

I had forgotten it was you who raised up their Dinan springs. That's definitely a good idea.

The Konis have almost no high speed compression damping. The fronts blow off around 4 in/s at 125lbs, and are only making 150lbs at 20 in/s. The rears are even less, blowing off at 50lbs and still only making 100lbs at 20in/s. Of course, these are my Konis with 30k miles on them, but still. I bet a fresh set isn't far off. What you're probably feeling is harshness due to lack of control and then bottoming.

Hm that might be right. It’s tough to tell sometimes where it’s coming from, and our roads really aren’t great, so I could see myself eating up that whopping 1/2-3/4” of travel I have. Low speed compression damping actually feels pretty well matched to my car’s mass and the Dinan springs, but the car feels harsher than it should over small bumps for these spring rates. I’d be really curious to take yours out for a spin to see if it’s just me. I’m also coming back to BMWs after a hiatus with porsches, which the modern ones are tuned quite well.

Did you measure anything representing stiction on the struts? This could also be driving what I’m feeling, more likely from the front at least, because McPherson.

[Mayan-Viking]

This is pretty dope. Well done.

[George Hill]

Great thread.

Just a fyi, Dinan runs shorter bump stops with their spring/koni package.

[cobra]

Great thread.

Just a fyi, Dinan runs shorter bump stops with their spring/koni package.

I read that once before, but my kit (complete spring + shock kit direct from Dinan) did not include any different bump stops, and they don't show any shorter bump stops in photos. Where did you get this information?

[George Hill]

I read that once before, but my kit (complete spring + shock kit direct from Dinan) did not include any different bump stops, and they don't show any shorter bump stops in photos. Where did you get this information?

When you buy the Dinan Konis they come with a factory bumper stop that has been partially cut down. I kick myself for not documenting it better, let me see what I can find...

[dukeofchen]

When you buy the Dinan Konis they come with a factory bumper stop that has been partially cut down. I kick myself for not documenting it better, let me see what I can find...

Would be great to know, PO put the Konis I have on and by now I'm sure the bump stops are due a change. Would love to reduce the crashiness of the setup over bumps and potholes.

Didn't see any products or pictures on their website for E46 applications but they do sell bump stops like these for the E39 M5. Wonder if they still offer them, or if cutting stock ones or alternative bump stops would do the trick. Also saw that Koni offers a variety of bump stops - anyone have insight into which of these might be the best application?

Not to derail the thread – all I have to say is I'm beyond impressed with the dedication to this project even though it's beyond my comprehension.

[tlow98]

I believe Dinan calls the bump stops the “supplementary ride kit” or something like that. Definitely, it used to exist and as the way they used to sell them. They also used to sell just e36 M3 front bump stops with that kit as they are shorter, as well. Z4M bumps stops are nearly the same as well, iirc. All of this is from memory, but I’m quite certain it was some combination of the above.

[Tbonem3]

They sell E36 bumps and cutdown mounts for their E9x kit as well.

[cobra]

Regardless of whether they include cut down bump stops or not, the issue is that the Koni shock bodies are the same length as stock. So if you lower the car you're eating up some of that bump travel. The Dinan springs are only 13% stiffer than stock yet they eliminate 25% of the bump travel. So raising them up is a good call. Bry5on raised his 1/2" which would put you just under stock height still.

But it won't look as cool so there's that.

[Casa de Mesa]

Cobra this is pretty inspiring stuff!! Freaking gnarly as hell.

Interesting your choice of shocks were Fox. I see above you said:

The dampers are matched accordingly and are pressure balanced at all speeds. I would say the tune is something between a street and track setup – firm but still compliant enough to handle anything from a bumpy mountain road to smooth high speed curves."

Did you valve the shocks each time based on the spring rates you were swapping out? My assumption is yes... but curious if this is a step you took each time or if the valving was wide enough to care for all spring rates you experimented with.

One of the biggest light bulb moments for me in my car tuning (or de-tuning, lol) history has been:

1. Set the car's ride height, measure the hub to a fixed point so I could reference it later (the typical hub to fender on these cars)
2. Jack the car up, remove the spring, reconnect the shock/strut.
3. Raise the control arm to static ride height
4. Observe how little the suspension can actually move before you bottom out

Your diagrams save quite a bit of time in this regard!