Quote:
Originally Posted by HighlandPete
Do you think BMW would approve the M Performance springs for the adaptive suspension?
I've a feeling BMW won't cover the change, can imagine the response will be something like "the adaptive package is designed to run on 'xxx' springs so any change will not be compatible".
Personally I find it hard to see how the variable damping will work with a much stiffer spring, OK will give some kind of ride/handling balance. But whether balanced to the damping parameters, that will be the test.
I've the 5-series with 3 mode settings, comfort, normal and sport. I sense with the stock springs that 'normal' gives the best damping/spring balance. Looking very critically at the damping, even though the other two settings work well, it is clear each is a compromise on damping the spring. Comfort when pushed, is giving that slightly underdamped feel, sport tends towards that over-damped, the over powering feel on a spring. Very subtle, but still there to sense.
It is really what we'd expect, as this is what happens with passive damping, when we play with damping rates on a given spring. But I do wonder when we change springs to a stiffer and shorter spring, how the variable function can adapt to the stiffer spring. In comfort mode, I sense the spring will overwhelm the damper setting, hence the comments of a "bit bouncy", the spring is not 100% controlled. Will the sport setting be enough damping for the new spring rate? That is what I'd be thinking. To me it is as if you'd want to turn up the damping rate parameters by xx% as well.
I suppose it depends on what you want, and what compromises you are willing to live with, but an experiment all the same.
HighlandPete
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Your questions and concerns are mine as well.
I don't have definitive answers, so I gotta go with what I think I know.
I will be asking about the warranty though, as I don't need to try the springs to get that answered.
Without getting a definitive answer I can't say yes or not.
How will it work? Can't say as no one has tried it yet.
Again my sense is that the dampers have plenty of "head room" by which they can handle a firmer spring.
A firmer spring needs more force to compress it a given distance, compared to a lighter/softer rate spring, so it actually moves/travels a shorter distance for a given bump.
Consider a given bump, with a lighter/stock spring rate, hitting that bump may compress the spring 3 inches, damper takes care of it.
With a heavier spring rate, hitting that same bump may compress the spring only 2 inches. So actual damper travel distance isn't too much concern, even with a minor 10mm shorter spring, which is about 1/2".
Compression and rebound damping is the greater concern.
With a static damper that is designed to handle a certain spring rate I would be more concerned that it wouldn't handle the spring as well as the valving can't adjust. It's tuned for a given spring.
People have put on firmer rate springs in cars using OEM shocks and then report a "bouncy" ride. That's because the damper can't control the action of the firmer and shorter spring as quickly as a damper designed for it, so the ride will be bouncy/springy. The internal valves are set for a certain level of fluid flow through them to control the spring. Since it has no way to alter the valve openings it's not able to handle the different level of fluid flow.
A shorter spring won't compress as far on a given bump, but the energy sent through the spring is still there, and thus the fluid will likely need to flow at a faster rate, as it needs to do so in a shorter period of time as the spring is not moving as much.
I'm guessing that the adaptive damper can handle it as it has the capability to adjust the valve openings, and if it needs to flow a given amount of fluid in a shorter time it can open and close the valves as needed.
Will it work? Can't say positively.
But, I'd like to try it. If the cost is reasonable it would be worth it as I don't want to go with non BMW springs, per the warranty question.
There's a fellow member on here who is running M Perf dampers with the stock springs and he likes the improvement a lot. The problem he could have had is that the system is under sprung and over damped, which would result in a jarring ride on smaller bumps (too much compression damping) and can cause the tire to skip off the pavement (too much rebound), but he says it's very nice. Leads me to think that the tuning/valving of the M Perf dampers is very near the adaptive dampers. Again, I'm giving it a guess, as I can't be positive.
BTW, my 135i with RFT's was under sprung and over damped, and the rear end would literally jump off bigger bumps. Switching to non RFT's helped stop that as the tires could now absorb some of the compression energy.
Adaptive in my 335i has only 2 settings, comfort and sport.
The difference is noticeable. In comfort ride is smoother, meaning, the bumps and dips are better absorbed. Handling wise, it's as one would expect it's "softer" as I can feel the ends off the car dipping down farther, and it allows greater body motion left/right and fore/aft.
Sport mode allows more of the road surface to be felt, but it's far from objectionable, it's very nice. Yet, as I've said, it's still soft for a "sport" suspension. It can easily use more spring. Handling is crisper, chassis responds quicker as there is less dipping all around, and even body sway is better controlled.
As you pointed out, it's a compromise. But having adaptive dampers helps that compromise. I'm surprised BMW didn't use adaptive dampers for it's
M Performance setup. My guess as to why not is because I think the cost would have been too much. When M adaptive was first released I think it was around $900. With DHP adaptive and VSS is $1000. You can look at it like the adaptive cost less or the VSS cost less, or a little off each one, as I think VSS was $300 on it's own.
I guess I'm considering putting my money on the adaptive dampers being much better and more capable than the stock sport dampers.
If it's works I think the adaptive dampers with M Perf springs may even be better than the M Performance setup due to their ability to control the spring dynamically. I can't see removing the adaptive system to go with M Perf.
M Perf is more for cars with either the stock suspension or the sport suspension.
If it doesn't work I may be able to sell the springs to someone who is looking to install the whole setup, and I can sell at a discount.
But if it does work, sweet.
