06-06-2019, 03:08 PM | #23 |
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There's lots to consider when changing suspension components, i.e. springs and dampers. If bump stops are taking frequent load/impact then something isn't right.
A shorter spring may provide the desired drop but the spring rate needs to be higher to offset the shorter operating range. Most good quality aftermarket springs have a higher rate, but, it needs to be sufficient for the damper pistons to be kept in their designed operating range relative to the damper body so as to avoid the risk of damper pistons bottoming-out inside the dampers. Big drops + OEM dampers can = trouble. BMW OEM dampers are a real weak point and can struggle to arrest the momentum of the chassis which then brings the bump stops into play, but, we really shouldn't be relying on bump stops as part of a suspension setup except to help prevent damage. Prior to having Ohlins R&T fitted to my car it was running OEM dampers and AC Schnitzer springs. The rear bump stops were removed (Ohlins R&T has internal bump stops) and we could have a good look at them. I'd always felt that the ACS rear springs were too soft for the F31, and this was evidenced by the stops - they were shot (split at one of the narrower parts of the stop).
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06-06-2019, 05:49 PM | #24 | |
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06-07-2019, 01:28 PM | #25 |
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Nope. I ran shorter bump stops when I had EDC with Eibach springs (and am xDrive).
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06-08-2019, 11:55 PM | #26 |
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Today while playing around with my front springs I decided to grab some pics of the Bilstein front strut bump stops.
Bilstein uses an "upside down" configuration, which means the main shock body is at the top of the strut and the piston shaft is mounted to the bottom of the strut. In a conventional setup the main shock body is contained within the strut, and the piston shaft is mounted to the top hat. To take apart the strut there's a 17mm nut on the bottom of the unit. After that's turned off use a 5mm hex to unscrew the piston shaft out of the strut body. You need to turn this screw clockwise to screw it into the strut body and out the inside of it. Once the top of the piston shaft is released to the inside of the strut you can pull the shock out. You can see the shock, bump stop, and piston shaft coming out of the strut body below. Here's a pic of the bare shock and the bump stop, which is 2.5" long. It's also quite soft (softer than the E39/E60 bump stops). I bet in the B8 struts a stiffer (and possibly shorter) bump stop is used. One thing I found interesting is that when I did a bump stop engagement measurement with my Eibach springs I saw that at static ride height the bump stops were already engaged and compressed 0.5". Since the stops are so soft I didn't really feel this initial engagement while driving. I ended up cutting the bump stop a bit anyways though to remove the static height compression. Maybe I'll see if Bilstein will tell me what bump stops they use in the B8s and sell me a set.
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06-24-2019, 08:31 PM | #27 | |
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06-24-2019, 11:54 PM | #28 | |
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I have a Bilstein B12 kit on the way to me now for my xDrive 340i and it was a good thing I saw this else I might have gone blindly into the install and have bottoming issues in the rear with my B8 struts. My kit is the 5-22 with the Eibach springs that will low by 25mm in the rear. So it looks like you are telling us that we can either chose from the 2.5 inch F80 or the 2.25 inch Dinan/E60 ones. Which one would you recommend based on your extensive testing? The shorter Dinan/E60 ones has an extra .25 inches of travel and is softer, which may match up well to the Eibachs while the F80 ones will probably eat up the 25mm drop in the rear. Thank you in advance! Last edited by dsc888; 06-25-2019 at 12:17 AM.. |
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06-25-2019, 04:16 AM | #29 |
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@dsc888 I installed the M3 bumpstops on B6 Damptronics with Dinan springs, so maybe 5mm taller ride height than what you are going for. There is about half and inch or more of travel before the bumpstop is engaged in the back.
As for the front, it would seem the M3 bumpstops are raising my ride height. Currently have a two finger gap in the front vs a one finger gap in the back.
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06-25-2019, 10:51 AM | #31 | |||
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If your spring rates are within the F3x and F8x OE spring ranges I'd say yes, if they're significantly stiffer than those, then the E60 one might be more comfortable.
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06-25-2019, 12:31 PM | #32 | |
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Option one is swap the M3(31336859768) with the OEM (31336791507), they are about 0.25" longer, but much softer to compress. Option two is figure out how much the M3's are compressing, and shave them down to match the ride height I would like to achieve. Option three is get different springs that will raise the back up some(idk right now the rear of my car seems to have a half inch side to side difference, so there's something going on) I have a feeling the 245/45 tires are helping absorb and smooth the impacts. We'll see when I hit that first pothole I wasn't able to avoid. Overall I have to say the ride has been excellent, and I am happy I waited forever for the B6's to finally be released. I do feel more imperfections in the road, along with a bit more vibrations from the engine.
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06-25-2019, 12:47 PM | #33 |
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if you are putting in a m3/m4 competitive springs, would you recommend to change to the bump stops that came with that spring setup or keep the oem f30 ones?
ha read Farkle response! Last edited by bariaga1; 06-25-2019 at 01:56 PM.. |
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06-25-2019, 01:38 PM | #34 | ||||
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06-25-2019, 02:20 PM | #35 | |
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That sounds about right. So that would mean that I definitely need to trim them like FaRKLe stated in his post as the Eibachs drop my rears by 25mm or about an inch vs 3/4 of an inch that the Dinans do. I’m guessing that riding on the OEM bumpstops on soft OEM springs was OK but may be undesirable with aftermarket firmer setups. How is your car riding so far? Do you have any issues with “crashing” noises over moderate bumps? |
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06-25-2019, 02:33 PM | #36 |
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Thanks Farkle! You da man.....
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06-25-2019, 02:44 PM | #37 | |
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Interestingly, I had bump stops replaced on my Honda Odyssey after out of spec ones were installed at the factory causing them to slide on downwards and causing a “popping” noise when I hit a moderate bump as the strut hit the floating stops. The new ones fit tightly on the shaft of the strut now. I wonder if the E60 ones will have the same issue if they don’t fit tightly in the cup like you said. And finally, I think you mentioned earlier that when you cut the stops, you ONLY keep the narrower end that faces down towards the strut housing, right? So in essence, you are DISCARDING the “wider” base end that touches the top mount? Or so I have it backwards? Thank you again! |
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06-25-2019, 10:18 PM | #38 | |
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You're correct that when you cut bump stops you cut at the wider side that touches the top mount. That side is the hardest and compresses the least, and if you cut away at the smaller side, then you lose softer initial spring rate of the stop.
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06-26-2019, 11:50 PM | #39 |
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A million thanks, FaRKle!
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06-27-2019, 04:26 AM | #40 |
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I'm about to do the opposite and probably remove the whole first level. I have a feeling I need more than what I could accomplish by shaving the back. I'll try to do the impossible and remember to take pictures along the way.
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06-27-2019, 02:18 PM | #41 |
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If you remove the smaller, damper-side first then the initial spring rate of the bump stop engagement will be higher and the transition will be less smooth. For example, let's say the bump stop is progressive starting at 50lbs/in and ramping to 250lbs/in (these aren't actual figures for the bump stop). Instead of boosting the spring rate by 50lbs/in on initial engagement you might be boosting it by 100lbs/in.
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06-27-2019, 05:30 PM | #42 |
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Slight threadjack sorry but along the same vein. i just grabbed the dinan bumpstops (from FaRKle! actually) and have my install scheduled for the dinan springs and shockware next Wednesday before M School track day. Can someone tell my what they are running for alignment specs? I want something aggressive but my driving is 99% street so I can't push it. i know the front isn't adjustable but I've heard guys can get -1.25 or a touch more. I am thinking of maxing out whatever I can get out of the front and then doing -1.75 for the rear which I believe is adjustable. Please tell me what you are running or send me a link to another thread.
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06-27-2019, 05:42 PM | #43 | |
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Front camber: max negative (probably about -0.60 or -0.70deg each side) Front toe: 0.03 to 0.10deg toe in each side Rear camber: -1.0 to -1.25deg each side Rear toe: 0.10 to 0.15deg toe in each side
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06-27-2019, 06:15 PM | #44 | |
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I'm not sure if I will modify the M3 or the Original bumpstop as of right now, that will be something to determine this weekend.
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