From e36m3_at_bmw-m.net Tue Dec 18 10:41:18 2001
Date: Tue, 18 Dec 2001 12:28:35 -0600
From: E36M3 <e36m3_at_bmw-m.net>
To: E36M3 <e36m3_at_bmw-m.net>
Errors-To: admin_at_chemsoft.net
Subject: [E36M3] E36M3 #1857

• 4 -------------------- Date: Tue, 18 Dec 2001 00:14:41 -0500
  From: "Tom Tice" <tetice_at_triad.rr.com>
  Subject: Re: bump stops on bilsteins - One More Time
  

Just to follow up Jeremy's original post, note some additional contacts that I had with Bilstein following Jeremy's but in the same time frame. I have included them here below for the benefit of anyone who wasn't tuned in to the list at that time.

I left Jeremy's account intact below in case anyone wants to capture one complete account of the info from Bilstein. Sorry for the length of this to anyone who is thoroughly tired of the Bilstein thread. There certainly seems to be no consensus.

One final thought on the differences in ride quality among those who have experienced Bilsteins. Tires can make a huge difference in ride quality. With my ultra stiff sidewall track tires, the car is unbearably harsh on the road. With my full tread, softer sidewall RE730s, it is quite acceptable. Perhaps those of you with the ultra performance street (S02s,S03, Pilots) tires are much closer to my track tires. I couldn't live with that either - but the handling on the track is great - I wouldn't want it any softer!

Tom Tice
'98 M3/4 - very happy with Bilsteins and H&R Sports '99 540/6 - ultra smooth road car (easy to be happy with the Bilsteins as I can switch to this car when I grow tired of them)

***=> First Message

Not so fast on that warrantee issue. Jeremy was kind enough to share with me the number of the guy at Bilstein that he talked to regarding the trimming of the bumpstops.

After pushing him a bit further on this issue he is doing some serious backpedaling (my perception). He says now that H&R recommends the trimming of the bumpstops (implying that it is not Bilstein's recommendation). When specifically asked about the warrantee, he first indicated that this would have no effect but that the warrantee doesn't cover any racing or "motorsport related" use. He also indicated that trimming the bumpstop will increase the chances of the shock being damaged in some form or fashion and the warrantee doesn't cover damage (i.e. due to a pothole, rough ride off the track, etc.).

Finally, he admitted that any warrantee decision would not be up to him anyway and that I should contact one of their sales representatives. I tried both east and west coast sales guys today but never got hold of either one. So unless one of these guys is willing to put something in writing, Bilstein certainly had the ability to weasel out of any warrantee claim. I'll let the group know if I find out anything different.

As for riding on the untrimmed bumpstops, while I haven't opened mine up yet those that I have experience with on other Bilsteins consist of a compressible foam. So riding on the initial portion of the bumpstop is not like having a solid suspension, only one with a different (i.e. stiffer) spring rate. Obviously if you compress the bumpstop far enough it will reach a point where it will compress no further but that should be (my guess) and inch or better in travel. If you have the H&R race springs you may well have the suspension effectively bottomed out but I wouldn't really know until I see how the bumpstops are actually constructed.

***=> Second and Follow up post

Well last night I actually opened up my Bilsteins and I agree with John's description below of the Bumpstops - medium soft rubber which is quite a bit firmer than the foam types I have seen before. However their diameter is quite a bit smaller as well would have an effect on their compressibility. They are just a hair under 3 inches long and the upper portion is somewhat hollow which would also increase its initial compressibility.

As for the warrantee. I spoke to the Bilstein East Coast sales guy today. I trust that he would give me the straight scoop as I have personally worked with him in the past (to put on joint BMW club/Korman open house autocross when he worked for Ray Korman). By the way he is a BMW enthusiast and also drives a E36 M3. In any event, his view is that trimming the bumpstops by 20 or 25 mm would have no effect on the warrantee - it would be judged like any other warrantee claim. You are really only removing about 1/3 of the bumpstop and the remaining bumpstop would adequately protect the shock from bottoming out type damage.

Furthermore, his view was that trim or no trim, the effect on the ride quality with H&R sports would not be perceptible as it would only behave like an incrementally increased spring rate. He reminded me that the M3 represents about 900 lbs at each corner and the force of 900 lbs would have no problem compressing the rubber bump stop.

My opinion is that I suspect this is true with respect to small undulations in the road or bumps like those associated with expansion joints. I suspect that one would notice a difference on jarring bumps such as a good sized pothole and that a rim bending type of pothole would be just as rough for either case as it fully compresses the bumpstop. The "ride quality" will still primarily depend on the valving of the struts and the spring rates.

Since my car is on jackstands and the struts are lying on my bench, I see no harm in removing 1/3 of the bumpstop in case it actually helps.

If they were already on my car, I'd seriously consider if it was worth the effort.

Tom Tice
'98 M3/4
'99 540/6

> -----Original Message-----
> From: Jeremy Lucas [mailto:jlucas_at_columbus.rr.com]
> Sent: Monday, December 17, 2001 10:19 PM
> To: E36M3
> Subject: Re: [E36M3] Re: bump stops on bilsteins
>
>
> Date: Mon, 17 Dec 2001 22:19:36 -0500
> From: "Jeremy Lucas" <jlucas_at_columbus.rr.com>
> Subject: Re: [E36M3] Re: bump stops on bilsteins
>
> ----- Original Message -----
> From: <Stan.Shaw_at_Excell.Net>
> > A data point, I asked Turner Motor Sports whether they would trim the
> bump
> > stops before shipping the units, and I was asked why. When I
> responded that
> > there was quite a bit of reputation associated with the Bilsteins
> needing
> > the bump stops trimmed. It was suggested that the email lists were
> rumor
> > mills.
>
> Stan, Talk to Lou at the Bilstein San Diego, CA office. (800) 537-1085.
> I had several conversation with him about this and he also conferred
> with other people with Bilstein back in June. Attached below is the
> information that I got from him that I sent to the list and with follow
> ups to another lister. I don't think it a matter of having a "problem"
> if they are not trimmed, it's just that your ride could be a little
> smoother trimmed.
> ____________
>
> Original Post:
> After all the discussion & confusion about trimming the bump stops on
> the
> front shocks a week or so ago, I made several phone calls to both
> Bilstein
> and H&R. I have a 95 M3 with Bilsteins and H&R 29910 springs that did
> not
> lower evenly when putting in the springs -- the front only went down
> about
> 10mm whereas the rear went down at least 20mm -- my biggest indication
> that
> the front might be on the bump stops. Once I got through playing
> voicemail
> tag with the right people, here's what I found out:
>
> 1) Bilstein says to cut 25 mm off their front bump stops. So I asked if
> I
> do this modification myself, does this void the warranty? They said no,
> only if you open up the actual shock portion, not just disassemble it.
> Just
> be careful not to strip the allen head in the bottom when disassembling,
> after taking off the 17mm nut on the bottom; a little heat helps with
> the
> allen head. So I ask why do they say to trim the bump stops? After
> much
> discussion and conferring with others in Bilstein the answer comes back
> "because even with stock springs & ride height the shocks are very close
> to
> the bump stops and also that H&R recommends it". Bilstein also
> cryptically
> noted that trimming the bump stops doesn't always seems to cure the
> uneven
> lowering based on customer reports. On a side note I asked him about
> revalving, and I was surprised it that the cost was only in the $50
> range
> per shock.
>
> 2) On to H&R, after the voicemail tag.... Answer: trim the bump stops
> 20mm
> for the 29910 springs. I ask why didn't something come with my springs
> to
> say that. He says it should have been in the box with the springs, and
> that
> trimming should cure the uneven lowering effect that I have right now.
>
> Hope this helps clear things up,
> ____________
>
> 1st Follow-up:
> According to them, they are fine with stock springs. It's just when you
> lower the car that you have a problem. I also asked them about the fact
> that the struts seem to be a hack job from the regular E36 and they guy
> didn't know anything about the original origin since that was quite a
> while
> ago.
> ____________
>
>
> 2nd Follow-up:
> I talked to Lou some more today. Especially in a sport application like
> the
> M3 the bump stops are about 15-20mm from the normal ride height, which
> he
> said is common in a lot of their OEM applications too. You have to
> remember
> that touching the bump stops doesn't mean your out of travel, your just
> starting to add a resistive force to the motion of the shock (kind of
> like
> having stiffer springs).
> ____________
>
> Hope that puts to rest the rumor mill. BTW, it is true that just
> because you see it on a list (even one as good as this) that doesn't
> make it true, and that you should always follow up and do your own
> checking.
>
> Jeremy
> 95 M3 still waiting to be trimmed at the next time I need to do some
> front suspension work
>