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      03-10-2020, 02:09 AM   #45
David.m
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Quote:
Originally Posted by Nezil View Post
This is very interesting indeed... but also surprising. The spring sits inboard of the damper (and bump-stop) on the M2 and most other cars, which would suggest that it compresses less than damper. If the damper is already on the bump-stop at rest before lowering, the springs will be doing almost nothing. The bump-stops on modern cars are designed to be somewhat progressive, and a bit like a spring in themselves, but it doesn't seem right to be driving around on the stops.

RealOEM shows that the M2 has the same shorter bump stops as the M3 and M4, but different springs and shocks. If what you're saying is true, there really isn't any valid reason to fit lowering springs on the rear without addressing the bump-stop issue.
What I was told is that M2 stock suspension at stock height has approx 10mm of compression before contact with the bump stop. I was responding to/questioning the suggestion that lowering 10mm will improve handling when in fact doing so effectively leaves no room for further compression before the bumpstop comes into play.

I'm currently stock and on our country roads at speed it's not hard to bottom out and sometimes the rebound is violent enough to throw me out of the seat. Makes life interesting when you're using the steering wheel to both steer and hang on to, and legs to both brace yourself and shift gears! I've bought some Ohlins R&T which apparently fix the rear suspension issue.

Possibly the M3/4 shocks allow for more travel before contact with the bumpstop? I don't know.
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      03-10-2020, 06:58 AM   #46
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Quote:
Originally Posted by David.m View Post
Though with the M2 that will have the rear shocks almost resting on the bumpstops (info I learnt from a guy who tarmac rallies his M2C & has gone to custom coilovers). Can't see how handling would be improved?
10mm of stock travel seems to be an impossibly small amount of tolerance to me.
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      03-10-2020, 08:47 AM   #47
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Quote:
Originally Posted by VisualEcho View Post
10mm of stock travel seems to be an impossibly small amount of tolerance to me.
Yeah, there is literally no way it has a little more than 3/8" of travel before bottoming out. Hell, the stock suspension probably drops near that much when someone sits in the car.



OP, I didn't want to read all the pages, but why not run a HAS (height adjustable spring) kit? You can keep the stock dampers, and adjust height, while not being nearly as expensive as coilovers. You obviously aren't able to adjust rebound or compression as you would on coilovers, but that's why you pay less than 1/2 the price. You simply set it to what you want and forget it.

As for tire wear on your old cars, if you had camber wear from running springs, something definitely wasn't done correctly. In my stancy pants days running almost double digit camber, I could have tires last 10,000 miles easy. Either you didn't get an alignment after installing the springs, the person who did the alignment didn't know what they were doing, or the machine wasn't calibrated properly.
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      03-10-2020, 09:26 AM   #48
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Quote:
Originally Posted by VisualEcho View Post
10mm of stock travel seems to be an impossibly small amount of tolerance to me.
It's 10mm of travel to contact with the bumpstop, from there you add whatever compression of the bumpstop allows but of course resistance increases as it compresses until you eventually bottom out.

This is info I was given by a guy who has had custom coilovers made for his M2C. Have to say it's not inconsistent with some of the violent rebound I get on our country roads. I'm installing some Ohlins R&T in a few weeks so before I remove the oem I'll mark the stock ride height on the shock & verify travel to the bumpstop.
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      03-10-2020, 09:49 AM   #49
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I think what youíre saying is that itís 10mm of shock travel until contract with the bump stop. Travel at the wheel will be slightly larger because the suspension geometry will compress the spring less, then the shock, then the wheel.

If this is correct, and I donít doubt it from other posts Iíve read, then youíll get ~15mm travel (at the wheel) of the rear spring rate, then a combination of rear spring plus bump stop until they both compress to the point of being solid. How far that travel is depends on the combination of the bump stop and spring.

You have to understand that the bump stop in our cars is not a solid block of rubber, itís part of the spring / shock / geometry design, and a change to it can make a big difference. Itís completely reasonable that BMW May have designed it to operate this way, and lowering springs alone (or coil over kits that arenít true coil overs in the rear) will need some modifications to the bump stop if youíre lowering.
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      03-10-2020, 10:36 AM   #50
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Quote:
Originally Posted by Conissah View Post
Quote:
Originally Posted by VisualEcho View Post
10mm of stock travel seems to be an impossibly small amount of tolerance to me.
Yeah, there is literally no way it has a little more than 3/8" of travel before bottoming out. Hell, the stock suspension probably drops near that much when someone sits in the car.



OP, I didn't want to read all the pages, but why not run a HAS (height adjustable spring) kit? You can keep the stock dampers, and adjust height, while not being nearly as expensive as coilovers. You obviously aren't able to adjust rebound or compression as you would on coilovers, but that's why you pay less than 1/2 the price. You simply set it to what you want and forget it.

As for tire wear on your old cars, if you had camber wear from running springs, something definitely wasn't done correctly. In my stancy pants days running almost double digit camber, I could have tires last 10,000 miles easy. Either you didn't get an alignment after installing the springs, the person who did the alignment didn't know what they were doing, or the machine wasn't calibrated properly.
I thought people where saying the HAS kits also are not good for stock dampers.
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      03-10-2020, 10:42 AM   #51
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Bee Pee has a great post that talks about cutting down the rear bump stops with the MP Coil Overs here: https://f87.bimmerpost.com/forums/sh...center+gravity

There is also a post on the F30 forum about bump stops that's quite informative by FaRKle! here: https://f30.bimmerpost.com/forums/sh....php?t=1621134
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      03-11-2020, 08:41 AM   #52
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All things being equal, a lower center of gravity will reduce load transfer during both lateral and longitudinal acceleration, which increases total available traction during corner, but may decrease traction slightly during forward acceleration. Of course, the key words here are "all things being equal". After lowering, you need to get the alignment checked and make sure toe is unchanged (or improved) from stock settings. Negative camber will increase at both ends with a lowered car, but that is probably a good thing.

Street cars, even M cars, are full of compromises. Ride height is one of the main ones and is also one of the compromises owners can fix with aftermarket options provided they're willing to lean that compromise a little more towards performance and a little away from day-to-day drivability.
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      03-11-2020, 02:58 PM   #53
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I'm happy with stock ride height and wheel arch appearance tbh
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      03-11-2020, 09:06 PM   #54
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Checkout this thread if people think 'dropping it' is a fast and easy way to better handling

https://www.m3post.com/forums/showthread.php?t=339168
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      03-12-2020, 12:49 AM   #55
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Quote:
Originally Posted by Montaver View Post
I cant comment on Audi, but neither BMW nor Porsche sell lowering springs for their cars. BMW has a HAS kit which has revised bump stops and spring rates.

Springs generally don't make your car handle better for a couple reasons -

1. The spring rates are higher than the dampers are valved for, which means the dampers struggle to control movement particularly on rebound. This creates a 'bouncy' feeling.
2. They reduce the shock travel before you hit the bump stops, which effectively massively increases the spring rate. When the shock bottoms out that energy is transferred back through the chassis reducing grip. Suspension travel is key to handling road undulations.

I have never seen any evidence of lowering springs improving a well setup car (i.e. an M car). If you want to put springs on for aesthetics go for it, but saying that manufacturers design their cars to be lowered on springs doesn't make sense.
this.

Sorry to the other people that replied and I didnít get a chance to reply but honestly donít buy into the ďitís aftermarket thus betterĒ without meaningful investigation.
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      03-12-2020, 11:35 AM   #56
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Quote:
Originally Posted by Karmic Man View Post
Checkout this thread if people think 'dropping it' is a fast and easy way to better handling

https://www.m3post.com/forums/showthread.php?t=339168
Good link. Some good info there. But I wouldn't say his conclusion was that lowering != improved handling. His conclusion was that lowering could make handling worse because the less travel is not always offset by increased spring rate and/or because the reduced travel/changed spring rate is not matched with proper damping rate. Totally agree with that.

In my mind, stand-alone (i.e. not coil-over) adjustable dampers (or more aggressively damped) is a major need for this car right now. Well, at least for me.
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      03-12-2020, 07:00 PM   #57
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Quote:
Originally Posted by Karmic Man View Post
Checkout this thread if people think 'dropping it' is a fast and easy way to better handling

https://www.m3post.com/forums/showthread.php?t=339168
Exactly, improving suspension is way more than just 'lowering it'. Sacrificing suspension travel without the appropriate damping control will not improve performance, often quite the opposite.

I think the stock suspension is very well rounded on the M2C, particularly at medium to high speeds. It lacks the outright feel and control of a coil over setup but that's to be expected. It's better out of the box than the EDC on my E90 M3.

Once you have experienced a properly sophisticated damper (i.e. Ohlins, MCS etc.) it's hard to go back
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      03-14-2020, 12:03 AM   #58
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Quote:
Originally Posted by Karmic Man View Post
Checkout this thread if people think 'dropping it' is a fast and easy way to better handling

https://www.m3post.com/forums/showthread.php?t=339168
That thread was extremely informative, but because it was based on the F80, not all of it applies to our cars exactly.

We do have the same subframes and suspension components except for springs and and shocks. The M2 front springs are different between the DCT and 6MT cars, which is a little surprising, but also makes sense if the DCT is slightly heavier.

The most important take away that I get from the linked thread is the motion ratio of 96% for the front, and 83% for the rear. If what David.m's friend said is true, 10mm of shock travel before bump stop equates to 12mm of travel at the wheel. That's not a lot at all.

I'd heard from other posts that the Dinan coil over kit is more compliant yet flatter than stock, and I think I understand how that could be possible. Dinan states that their kit has springs that are 18% stiffer than stock at the front, and 5% stiffer than stock at the rear. They recommend 0.75" lower at the front, and 0.5" lower at the rear, and they provide shorter bump stops for both front and rear. If it's true that the stock M2 is basically riding on the bumps stops a lot of the time, and therefore has a far higher effective spring rate than the spring alone, a kit with a higher spring rate (like the Dinan kit) can still end up more compliant, cause slightly less compression and therefore be flatter (because of the higher spring rate), all before the now shorter bump stop comes in to play.

The MSS kit that's discussed in another thread appears somewhat similar, but they don't provide a replacement rear bump stop, and that concerns me... a lot. MSS allows zero drop from stock, but if the rear bump stop is being engaged almost all the time, their trick multi-rear spring setup will be less effectively at best, and meaningless at worst.

I'm going to be replacing the shock top hats on my suspension probably next weekend, in order to retrofit an M2C / M3 / M4 Carbon and Aluminum strut brace. At that time, I'm planning to remove the dust covers from my shocks both front and rear to investigate both the amount of travel before bump-stop engagement, and if the bump stops are compressed during normal driving.

It would be cool to set up a GoPro in the fender, but I'm going to wrap a small cable tie around the shock strut and see how far up it moves in a short drive. If it ends up touching the bump stop when I take a look, we won't know how much bump stop compression happens on a typical drive, but we will know that it happens often... and I suspect it will.

Obviously coil over systems usually come with their own bump-stop systems, but Bee Pee's experience with the MP coil overs suggests that the BMW ones are designed to only be used at the MP specified height; any deviation requires modifications to the bump-stops.
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