[ajsalida]

OP, are you still running e9x M3 rear bar and stock front bar? That might be part of the problem.

[AtlasM]

Originally Posted by ajsalida

So wait now longer stops are bad? My point was many stops will work, depending on how low you've dropped the car. You want as much unimpeded bump travel as you can get for whatever height you've dropped. If you are bottoming out now with 52mm then going to 60mm is not going to help much. And no 70mm will not work well either. The problem is with the shocks not the bump stops.

edit: Are you sure about those numbers? I don't think OEM ZSP is longer than OEM XI. I think the stops on my xdrive car were longer than 60mm.

Getting stops that are a bit longer/stiffer is desirable but I also don't want to go too long. It's a combination of the 52 mm to 60 mm increase plus the rubber stopper ring on there.

I have the still fully-assembled original xDrive front struts hanging out in my garage and measured the bump stops at 60 mm last night. Didn't take a pic, but I'll try to get one.

ZSP is 70 mm:

Originally Posted by ajsalida

OP, are you still running e9x M3 rear bar and stock front bar? That might be part of the problem.

I am, it's an E93 M3 rear bar, but I have adjustable end links front and rear that were properly dialed in by my alignment shop. Doubt that's the source of the issue.

[feuer]

Originally Posted by AtlasM

Well, I'm going to do an experiment. I ordered the E9x M3 front bump stops. Once I have them on the car I'll test them out in the couple places I have the most trouble with bottoming. Not expecting a miracle, but hoping for an improvement.

Originally Posted by AtlasM

E36 M3 are 52 mm, E9x xDrive & M3 are 60 mm, E9x ZSP are 70mm. I don't think the ZSP bump stop on a lowered xDrive would be a good option.

Originally Posted by ajsalida

I thought the PS stops were SHORTER than ZSP???

AtlasM
I honestly think and hope that those 8mm difference and the bump stop disign will help with the issue of the strut shaft bottoming out at least while they are new.

ajsalida
per link from post#1 Performance are longer than ZSP

31 33 6 767 333-01 ZSP Front bump stop 2.75", weighs 58 g
31 33 8 036 012-01 Perf (Ver.1) front bump stop 2.94", weighs 63 g

33 53 6 767 335-01 ZSP Rear bump stop 2.88", weighs 51 g
33 53 8 036 000-02 Perf (Ver.1) rear bump stop 3.06", weighs 75 g

[ajsalida]

Originally Posted by AtlasM

I am, it's an E93 M3 rear bar, but I have adjustable end links front and rear that were properly dialed in by my alignment shop. Doubt that's the source of the issue.

The point was that a soft front bar vs stiff rear one will cause lots more weight transfer to front corner, and wheel motion, under side loads and on one-sided bumps. A stiffer front bar would keep that under control more. wouldn't help on symmetric bumps (where both L+R wheels move the same in sync), but it would on potholes and such.

[AtlasM]

Originally Posted by ajsalida

The point was that a soft front bar vs stiff rear one will cause lots more weight transfer to front corner, and wheel motion, under side loads and on one-sided bumps. A stiffer front bar would keep that under control more. wouldn't help on symmetric bumps (where both L+R wheels move the same in sync), but it would on potholes and such.

The spot where I most frequently bottom out the front suspension is a symmetric bump. It's this highway on-ramp that's under construction where there's a weird transition. You go down a concrete slab, cross a mostly-level stretch of asphalt, then go up another concrete slab. The asphalt is really poorly blended into the concrete and it's probably a 10-15 degree angle, so it's a sharp transition. Going down the one slab to the asphalt is kinda bad, going from the asphalt up to the second slab is worse.

[ajsalida]

Originally Posted by feuer

AtlasM
I honestly think and hope that those 8mm difference and the bump stop disign will help with the issue of the strut shaft bottoming out at least while they are new.

ajsalida
per link from post#1 Performance are longer than ZSP

31 33 6 767 333-01 ZSP Front bump stop 2.75", weighs 58 g
31 33 8 036 012-01 Perf (Ver.1) front bump stop 2.94", weighs 63 g

33 53 6 767 335-01 ZSP Rear bump stop 2.88", weighs 51 g
33 53 8 036 000-02 Perf (Ver.1) rear bump stop 3.06", weighs 75 g

The PN for front bump stops you listed are also listed for M-sport (aka ZSP) up to 3/2007, not the OEM add-on performance suspension upgrade kit with the yellow springs. Furthermore the 2nd PN is for OEM ZSP from 3/2007-on:

http://www.realoem.com/bmw/enUS/show...24#31338036012

Point is time-wise they went with shorter stops for OEM ZSP package mid 07 model year.

I do not think you can get true performance kit stops (that came with the yellow spring kit and not the same as M-performance) separately. But I haven't looked into that kit in a long time. They had 2 versions I'm sure you know. And I've read they were shorter than ZSP, which is why everyone wanted them back then but they were N/A. I actually wanted these instead of e36M3 back when I first lowered my car, but couldn't get them. That was ~4-5 years ago maybe things have changed.

Also it just does not make any sense to have longer stops with shorter/lowering springs but who knows WTF those BMW guys were up to. They screwed up the XI suspension massively so my faith in them is seriously diminished.

[ajsalida]

Originally Posted by AtlasM

The spot where I most frequently bottom out the front suspension is a symmetric bump. It's this highway on-ramp that's under construction where there's a weird transition. You go down a concrete slab, cross a mostly-level stretch of asphalt, then go up another concrete slab. The asphalt is really poorly blended into the concrete and it's probably a 10-15 degree angle, so it's a sharp transition. Going down the one slab to the asphalt is kinda bad, going from the asphalt up to the second slab is worse.

OK yeah then a bigger bar won't help with the bottoming part in that situation.

[AtlasM]

Originally Posted by ajsalida

The PN for front bump stops you listed are also listed for M-sport (aka ZSP) up to 3/2007, not the OEM add-on performance suspension upgrade kit with the yellow springs. Furthermore the 2nd PN is for OEM ZSP from 3/2007-on:

http://www.realoem.com/bmw/enUS/show...24#31338036012

Point is time-wise they went with shorter stops for OEM ZSP package mid 07 model year.

I do not think you can get true performance kit stops (that came with the yellow spring kit and not the same as M-performance) separately. But I haven't looked into that kit in a long time. They had 2 versions I'm sure you know. And I've read they were shorter than ZSP, which is why everyone wanted them back then but they were N/A. I actually wanted these instead of e36M3 back when I first lowered my car, but couldn't get them. That was ~4-5 years ago maybe things have changed.

Also it just does not make any sense to have longer stops with shorter/lowering springs but who knows WTF those BMW guys were up to. They screwed up the XI suspension massively so my faith in them is seriously diminished.

I pulled the part number for the PS for an E92 335i with build date 8/11 on RealOEM. It gave part # 33500444832. The ECS Tuning page for that part number has detailed photos.

The main thing I notice is the front bump stops have the stopper rings on them like the stock xDrive and E9x M3 front bump stops.





Those do look different from the ones with the white stopper rings in the pics I found in feuer's links. Unfortunately I can't quite make out a full part number from this picture. But the overall look is very similar to the M3 bump stops.

[ajsalida]

At this point I think you should just get some different stops and try them. BTW I think those rings are so the dust boot has something to hang onto, and aren't for changing stiffness or anything.

[asrautox]

I'm running the M3/Z4 stops with Koni Sports and Dinan springs. Zero issues bottoming out or pot-hole explosion'ing . Rides like stock but lower without the float.

[Washington335i]

You have the correct bumpstops - E36 M3 - on the fronts. Your stock xi bumpstops were 2.6". The E36 M3 bumpstops are 2.1". That extra .5" gives you additional strut shaft travel to compensate for the lowering springs. Adding LONGER bumpstops is not going to cure the "bottoming out" feeling; it will make it worse. The E9X M3 front bumpstops are 2.9" and will not fit anyway as the diameter of the bumpstop hole is too large for E9x non-M3 strut shafts. And the idea that a "softer" bumpstop might make the bottoming out less abrupt is not accurate either since the E36 M3 bumpstop comes from the lightest car of all the bumpstops you are talking about - it is the softest. The E9x x-drive, E9x ZSP, and E9x M3 are all firmer, and longer = you will make your problem worse. I assemble BMW suspensions every day and have every one of these bumpstops in my shop side by side.
Best regards, Chris

[AtlasM]

Originally Posted by Washington335i

You have the correct bumpstops - E36 M3 - on the fronts. Your stock xi bumpstops were 2.6". The E36 M3 bumpstops are 2.1". That extra .5" gives you additional strut shaft travel to compensate for the lowering springs. Adding LONGER bumpstops is not going to cure the "bottoming out" feeling; it will make it worse. The E9X M3 front bumpstops are 2.9" and will not fit anyway as the diameter of the bumpstop hole is too large for E9x non-M3 strut shafts. And the idea that a "softer" bumpstop might make the bottoming out less abrupt is not accurate either since the E36 M3 bumpstop comes from the lightest car of all the bumpstops you are talking about - it is the softest. The E9x x-drive, E9x ZSP, and E9x M3 are all firmer, and longer = you will make your problem worse. I assemble BMW suspensions every day and have every one of these bumpstops in my shop side by side.
Best regards, Chris

I guess the E9x M3 bump stops may be a non-starter then. What is the shaft diameter on the xDrive shocks?

I was hoping to accomplish a stiffer bump stop, not a softer one. My thought was the stiffer bump stop would help make up for the FSD shocks going super-soft on sharp impacts. But if the E9x xDrive and M3 bump stops are too long I'm not attached to them as the solution.

Actually I had already been looking at a potential alternate solution: aftermarket polyurethane progressive bump stops with stiff compression curves. I found a couple potential options from Speedthane and Penske. Both of them have just over a 15 mm hole for the strut shaft, the Speedthane is 58 mm tall and the Penske is 60 mm.

So the Speedthane 58 mm would be only a couple mm longer than the E36 M3 but presumably a good bit stiffer. Think those might do the trick?

Speedthane:







Penske:

[rothwem]

You need some of these:

http://www.4wd.com/Jeep-Lift-Kits-Je...3OQaAsyz8P8HAQ



You'll be jumping dunes in no time!

[ajsalida]

OP, I hope you have a good dental plan. Those stops will knock your fillings out.

The other poster was correct, e9x M3 strut shafts are larger diameter so those stops won't fit. I have PTSD from finding that out the hard way.

[AtlasM]

I canceled the order on the E9x M3 stops, they hadn't shipped out yet anyway so no big deal.

I called RE Suspension, the company that made the graphs in my post above. Between the Penske and Speedthane stops, the Speedthane ones are a closer match for the car. The Speedthane bump stops come in red (soft), white (medium), and blue (stiff) versions. They said that generally the white Speedthane stops are similar in stiffness to the OE bump stops on heavier cars like ours. On lighter cars like Miatas the red ones are similar to OE.

What I'm thinking is, while the E36 M3 stops might be the right length, they're not stiff enough so that when the shock gets to the end of its travel, I get a hard bottoming out. The FSDs go soft on sharp bumps and are more inclined to hit the end of the travel in this situation. So with the blue Speedthane stops, which are stiff but still progressive, they are more likely to help stop the car from hard bottoming like is happening on the E36 M3 stops now.

At least that's the theory. All I know is I want to try something different from the E36 M3 stops because the front suspension isn't working how I want it to work.

And yes, it also occurs to me that something like Koni Yellow or Bilstein B8 would not need this hard of a stop, and who knows if the FSD + hard bump stop combo really rides any better than say Yellows on full soft, but hell, I've got the FSDs already and I want to try and make them work.

[feuer]

Is 12mm non M vs 14mm m3 and I personally don't think that will affect how the bump stops functions, or how it would function. I had MBenz bump stops on my e36 with zero adverse effect. From w201 AMG as they are stiffer than regular and the front struts are almost direct swap and require a little work to fit. I had some sitting around and used them. Ride was a dream. Koni yellow and Eibach Pro kit.

[AtlasM]

Well the strut shaft hole was not my only concern about the E9x M3 bump stops, it's also the length which is longer than the E9x xDrive according to Washington335i. I was assuming they were the same length because in this picture, the E9x M3 stops don't look much longer than E36 M3.



I had measured my old E9x xDrive bump stops at 60 mm, so I guessed based on this picture of the E9x M3 stops next to the ~52-53 mm E36 M3 stop, that the E9x M3 was also 60 mm. But Washington335i says the E9x xDrive are 2.6" which is 66 mm, so maybe my old ones had become compressed over time. He puts the E9x M3 at 2.9" which is longer than the xDrive.

Looking at the picture again, my assumption could easily be incorrect for 2 reasons:

1. The E36 M3 stop looks brand new and the E9x M3 stop is worn out.

2. Both stops are laying on the ground, and the rubber ring of the E9x M3 stop has it sitting at an angle, not flat on the ground, so it doesn't look quite as long as it really is.

My main goal is to get something stiffer than E36 M3 stops but not necessarily longer. I'm hoping that a stiffer bump stop will help cushion the end of the shock travel more.

On something like a Koni Yellow or Bilstein B8 that have a good amount of compression damping, the E36 M3 front stops are a good match because they give a bit more travel and the shock takes care of the rest. But on the FSDs where they relax the compression damping in response to a sharp impact, I believe a soft bump stop like the E36 M3 lets the shock slam too hard into the end of its travel.

I was actually thinking of going with the Speedthane blue stops before the post about the E9x M3 stops being potentially too long, so that just pushed me over the edge to make the change.

[Washington335i]

Correction: I mixed up the E9x M3 with the E9x PS bumpstops. The E9x PS (v.1) bumpstop is 2.9". I am not sure what the e9x m3 bumstop is. Sorry for any confusion. I do know that the m3 rod shaft is thicker, so the e9x m3 bumstop is not a good choice. Yes, it will fit over the e9x non-m3 shaft, but will be loose and will not stay in place. So, the dust tube that is supposed to protect the rod shaft will not do its job, plus you might even herar the bumpstop and tube fall back after every big bump.
Best regards, Chris

Originally Posted by AtlasM

Well the strut shaft hole was not my only concern about the E9x M3 bump stops, it's also the length which is longer than the E9x xDrive according to Washington335i. I was assuming they were the same length because in this picture, the E9x M3 stops don't look much longer than E36 M3.



I had measured my old E9x xDrive bump stops at 60 mm, so I guessed based on this picture of the E9x M3 stops next to the ~52-53 mm E36 M3 stop, that the E9x M3 was also 60 mm. But Washington335i says the E9x xDrive are 2.6" which is 66 mm, so maybe my old ones had become compressed over time. He puts the E9x M3 at 2.9" which is longer than the xDrive.

Looking at the picture again, my assumption could easily be incorrect for 2 reasons:

1. The E36 M3 stop looks brand new and the E9x M3 stop is worn out.

2. Both stops are laying on the ground, and the rubber ring of the E9x M3 stop has it sitting at an angle, not flat on the ground, so it doesn't look quite as long as it really is.

My main goal is to get something stiffer than E36 M3 stops but not necessarily longer. I'm hoping that a stiffer bump stop will help cushion the end of the shock travel more.

On something like a Koni Yellow or Bilstein B8 that have a good amount of compression damping, the E36 M3 front stops are a good match because they give a bit more travel and the shock takes care of the rest. But on the FSDs where they relax the compression damping in response to a sharp impact, I believe a soft bump stop like the E36 M3 lets the shock slam too hard into the end of its travel.

I was actually thinking of going with the Speedthane blue stops before the post about the E9x M3 stops being potentially too long, so that just pushed me over the edge to make the change.

[AtlasM]

Originally Posted by Washington335i

Correction: I mixed up the E9x M3 with the E9x PS bumpstops. The E9x PS (v.1) bumpstop is 2.9". I am not sure what the e9x m3 bumstop is. Sorry for any confusion. I do know that the m3 rod shaft is thicker, so the e9x m3 bumstop is not a good choice. Yes, it will fit over the e9x non-m3 shaft, but will be loose and will not stay in place. So, the dust tube that is supposed to protect the rod shaft will not do its job, plus you might even herar the bumpstop and tube fall back after every big bump.
Best regards, Chris

Interesting. That jives with this picture where the BMW PS bump stop (second from the left) is slightly taller than the E9x non-M rwd bump stop (on the left).



So the E9x M3 bump stops could very well be closer in length to the E9x xDrive, since both are a bit taller than the E36 M3 bump stops. This is the E36 M3 vs. E9x M3:



Even so, I still think the Speedthane 58 mm bump stops are probably a better choice than the E9x M3 stops. They're closer in height to the E36 M3 stops vs. E9x M3 stops, and there's actual information on them being both progressive and (hopefully) stiff enough to catch the FSDs from slamming into the end of their travel.

I'm not so sure the strut shaft diameter is a big issue, since according to this, the E36 M3 strut shafts are also 14 mm like the E9x M3, vs. the 12 mm on my car. I can tell you when I've had a the front of the car up in the air and taken a wheel off the car, when the suspension droops, the E36 M3 bump stop stays up at the top of the strut.





The diagram of the Speedthane bump stop shows its inner diameter is 0.595" which is just over 15 mm. So in theory that could be looser than the M3 bump stops on the 12 mm strut shafts, but just as an example, this kit for Minis, which also have 12 mm diameter struts, uses the soft red Speedthane bump stops. Not that this means conclusively they will stay up where they're supposed to on 12 mm diameter strut shafts, but hey, at least it's something.

[AtlasM]

I got the Speedthane bump stops put on the car today.

My mechanic said they're extremely snug on the strut shafts, so whatever concerns there might have been about inner diameter are no problem. Maybe they'd be tough to get on M3 shocks but they certainly won't be dropping down the strut shafts. The only thing to note is the diameter of the Speedthane stops is much narrower at the top compared to BMW OE stops so a little zip tie engineering was necessary to keep the dust boots held up around the top of the bump stops, but they're secure now.

My overall initial impression is that the front of the car feels less crashy over bumps compared to the E36 M3 bump stops. I didn't get a chance to test them out on my absolute worst trouble spot because that construction zone got smoothed out. "Luckily" there are plenty of other shitty expansion joints and frost heaves around here for me to try. There's one highway on-ramp with a few bad frost heaves in it that didn't completely bottom out the front suspension before but certainly gave it a good thwack. The car still doesn't like this on-ramp but it does feel more secure when hitting those frost heaves.

I'm not going to go crazy with intentionally running over bad bumps, but I'll post an update once I've had more of a chance to drive around on them. So far though I am liking them.

[AtlasM]

I've had a few more days to try out the Speedthane bump stops and now I'll go ahead and say they made a HUGE difference.

I've run over some pretty bad bumps, some that are both wheels like expansion joints and bad road transitions, some just one wheel like potholes, and I've only once managed to do something that approximated bottoming the suspension. That was when I put one wheel in a pretty decent sized pothole. Even then, there was no huge crash bang feeling like with the E36 M3 bump stops.

There is NO additional ride harshness. Really the ride comfort is much better because the front of the car isn't crashing over bumps. The bump stops are doing their job and stopping the shocks from bottoming out.

I took a front wheel off the car to check out how exactly my mechanic did the install, and basically he stuck the dust boots to the spring perch rather than the top hat of the strut (my camber plates in this case). When the suspension droops, the dust boot stays down at the spring perch but when the wheels are on the ground, the dust boot covers up the bump stop. With the E36 M3 bump stops, the opposite was the case, the dust boot stayed up at the top but it didn't reach all the way down to the spring perch when the suspension was at full droop.

Also, while the top nut of the FSDs may be 12 mm like the stock struts, the actual strut shaft is much larger than that. The Speedthane bump stop is really squeezed on there, and its inner diameter is a hair over 15 mm. I need to take a front wheel off again to replace a cracked hubcentric ring on one of my front wheels so I'll take some measurements and pictures of what all this looks like.

I know the FSD shocks catch a bad rap on here because of their "pothole explosion" type behavior, but based on how they now handle bumps with these bump stops, I really think that the issue is not with the shocks themselves but that they've been paired with the wrong bump stops. Yes, they do go soft in response to sharp bumps. That's what they're designed to do. But combine that behavior with a relatively heavy car with less suspension travel due to lowering springs, and while the E36 M3 bump stops are short enough to gain back some travel, they're way too soft to properly stop the shocks from bottoming out. The front of the car is now smooth and handles bumps great.

My goal when I chose the FSDs and B&G springs was to get the ride height exactly where I wanted it without resorting to coilovers, while also having a nice comfy ride, at least for a car running 19" summer tires and a performance suspension. With the Speedthane stops in front, that's now a reality.

The rear of the car has never really had this problem to the extent that the front has, but I've noticed it does occasionally have some excessive motion on big bumps, even though I've got Whiteline rear subframe bushings and Monroe upper & lower shock mounts. I'm so happy with the improvement from the Speedthane bump stops that I'm thinking about getting some for the rear.

[feuer]

I'm really glad it work out for you. Kind of confirms engineers and mine as well reasoning that sometimes slightly higher/taller bump stops help. They are progressive so even though you will "bottom out" the bumps sooner the ride would be smoother as you will not bottom out the strut which is a horrid experience. Thank you for sharing and I hope you will not be scalded for going with higher/taller bump stops! I sure did..