The BMW UUC Digest
Volume 2 : Issue 77 : "text" Format
Messages in this Issue:
Re: GC rear shock mounts
Re: GC rear shock mounts
Re: GC rear shock mounts
Re: Is this a record?
Re: Is this a record?
Re: Is this a record?
Battery life
Re: Cross drilled? (was: Time for F rotors and pads -
Re: Cross drilled? (was: Time for F rotors and pads -
Re: [e36 M3] SS brake lines
----------------------------------------------------------------------
Date: Wed, 10 Mar 2004 17:55:15 -0500 (EST)
From: Mark Andy <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: Re: GC rear shock mounts
Message-ID: <[EMAIL PROTECTED]>
Howdy,
On Wed, 10 Mar 2004, J. Ochi wrote:
> The GC mounts that your picture shows are the track-only ones, with a
> spherical bearing. What you probably want are the GC mounts with a
> urethane insert. The urethane ones are VERY durable - I used to go through
> the stock ones in 15K-20K miles. The GC ones have been in for over 60K
> miles, without any problems or signs of wear, and that's with much stiffer
> shocks than the Konis I was using with the stock mounts. The GC shock
> mounts also have a lifetime warranty, so if they do wear out, you can get
> replacements for free.
>
> I don't remember what class you autox the 325 in, but I think the GC shock
> mounts will take you out of stock...
I'm running in STX locally and maybe a national event this year (buying a
house & getting married, autox is getting cut back this year!). Last I
recall, STX had "SP level" wording in the works, which would explicitly
allow plates like this...
So what's more recommended, the "street" plates with the poly bushing or
the "race" plates with the spherical bearing? Seem like the poly bushing
wouldn't have as much rotational compliance, but I don't know how much
that matters. Also that the poly bushing would be a little more tolerant
of wear compared to a spherical bearing. I can't see a spherical bearing
ever "creaking" though! :-)
Its definately also nicer that the poly bushing plates are cheaper...
Cheaper is good right now!
> Installed correctly, you won't get any banging/squeaking/creaking. I've
> heard reports that if you don't tighten up the top shock nut correctly, you
> may get squeaking and creaking, but haven't experienced that myself. Most
> of those reports, though, are a little suspect - they tend to come from
> proponents of the JT Design rear shock mount...
What does "tighten the top shock nut correctly" mean? Like folks tend to
over tighten or under tighten?
> Yup, exactly. No more pulling on the trunk carpet. Works great if you use
> the Koni S/A shocks that you have to compress and turn to adjust.
Yep, which I'll have. This is definately an advantage of this design for
me.
> The slotted shock mount holes are only found on the shock mounts with the
> spherical bearings. If I remember correctly, Jay told me the slots are for
> use if you go to a full coilover setup in the rear. If you use the
> separate shock/spring setup in the stock location, you push the mount one
> way. If you relocate the rear spring into a coilover configuration, you
> push the mount the other way for more wheel clearance between the tire and
> the spring.
Ah. Ok, I guess that kinda make sense.
Thanks for the info (and to everyone else that's replied as well!)
Mark
------------------------------
Date: Wed, 10 Mar 2004 16:39:22 -0800
From: "J. Ochi" <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: Re: GC rear shock mounts
Message-ID: <[EMAIL PROTECTED]>
At 02:55 PM 3/10/2004, Mark Andy wrote:
>I'm running in STX locally and maybe a national event this year (buying a
>house & getting married, autox is getting cut back this year!).
Congrats!
>So what's more recommended, the "street" plates with the poly bushing or
>the "race" plates with the spherical bearing? Seem like the poly bushing
>wouldn't have as much rotational compliance, but I don't know how much
>that matters. Also that the poly bushing would be a little more tolerant
>of wear compared to a spherical bearing. I can't see a spherical bearing
>ever "creaking" though! :-)
For the rear shock mounts, get the street version with the poly
bushing. You don't need very much rotational compliance, and unless you
have very sensitive shocks (Motons, JRZs, Penskes, Koni 28xx, etc.), you
won't get any performance improvement with the spherical bearings.
Another problem is that the rear shock towers are a little delicate - I'd
be worried about ripping out the top of the shock tower if you use a
spherical bearing and a stiffer than stock shock. Also, with street use,
you'll wear out that spherical bearing in pretty short order, and have to
replace it probably at least every year.
If your car is a street car, get the street stuff. Unlike the "ricer" ads,
the GC race stuff is really intended for race cars - cars that will be run
on a track, and maintained like a race car. Personally, I'm a bit fed up
with the idiots you tend to see on many of the "forums" who brag about
putting in spherical-bearinged race suspension components in their street
car, then whine about the clunking noises that their car makes 10K miles
later. Then whine some more when they find out that they have to replace
several hundred dollars worth of spherical bearings every year to fix the
clunks...
>What does "tighten the top shock nut correctly" mean? Like folks tend to
>over tighten or under tighten?
Yup, they over or under tighten. Or, they don't use a nylock or a jam nut,
so it loosens up.
Jim Ochi
------------------------------
Date: Wed, 10 Mar 2004 19:54:16 -0500
From: ben keyes <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: Re: GC rear shock mounts
Message-ID: <[EMAIL PROTECTED]>
Brian Daley wrote:
> I was aware of that, just pointing out a source for
> the GC urethane street RSMs that had been mentioned
> at what I thought was a decent price. I couldn't even
> find the part on GC's website.
they're down the page when you follow the "BMW" link in
both the urethane & solid/spherical version.
> What do you find crappy about the JTD RSM's?
> Just curious as they seem very similar to the GCs.
they always end up stuck to the shocks which can be
a major pain to take apart (and you can damage the shock
if you're not really careful. additionally they're not as
robust a design, I forget in what way, my smarter
engineer friends tell me & I believe them. the JTD's
have always been the same or more expensive than the
GC ones & they're not guaranteed for life, so why mess
around ? the $89 price on that site you referenced is
marginally cheaper than GC themselves tho, so that's
not a bad thing.
Ben
------------------------------
Date: Wed, 10 Mar 2004 17:46:38 -0800
From: Herman Chan <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: Re: Is this a record?
Message-ID: <[EMAIL PROTECTED]>
I replaced the original battery in my E36 (8/92 production) at the
end of 8/2001 but could have probably milked it a little longer if I
wanted to live dangerously.
Ironically, the batteries were one of the more durable components of
the early E36s.
Herman
------------------------------
Date: Wed, 10 Mar 2004 21:33:42 -0500
From: "Steve Stoner" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Subject: Re: Is this a record?
Message-ID: <[EMAIL PROTECTED]>
My 5/97 production M3 with 74K is still running fine on the original battery. That
means I'm coming up on 7 years.
I top it off with distilled water every once in a while.
[Attachment of type application/ms-tnef removed.]
------------------------------
Date: Wed, 10 Mar 2004 19:02:31 -0800
From: jkerouac <[EMAIL PROTECTED]>
To: Steve Stoner <[EMAIL PROTECTED]>
Cc: [EMAIL PROTECTED]
Subject: Re: Is this a record?
Message-ID: <[EMAIL PROTECTED]>
Steve,
You got me beat by a month, but 'Jack has been On the Road 20k
miles more.
I agree, its important to keep Ms.Varta topped up with water. I think a
lot of batteries get prematurely replaced because owners or mechanics
fail to do so.
Barry
Steve Stoner wrote:
My 5/97 production M3 with 74K is still running fine on the original
battery. That means I'm coming up on 7 years.I top it off with distilled
water every once in a while.
------------------------------
Date: Wed, 10 Mar 2004 22:53:20 -0500
From: "Karl Zemlin" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Subject: Battery life
Message-ID: <[EMAIL PROTECTED]>
When I was 15 (would have been 1977) my great grandmother was still driving
her '56 Studebaker President - salmon and white. 35,000 miles on the car
and the battery was original - this was in northern Minnesota.
She traded the car on a new Dodge Reliant (I think). The dealer gave her
$1500 for the Studebaker. It broke my heart. That car was in great shape.
http://summerville-novascotia.com/Studebaker/1956StudebakerPresidentClassic.
jpg
------------------------------
Date: Wed, 10 Mar 2004 23:09:41 -0500 (GMT-05:00)
From: Maverick <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: Re: Cross drilled? (was: Time for F rotors and pads -
Message-ID: <[EMAIL PROTECTED]>
I am planning on using cross-drilled (probably Zimmerman) rotors when I replace brakes
on my 96ti sport. Either direct replacement, or if I get ambitious 325 fronts (with
the proper calipers). I am not sure of the benefit of the drilling in cooling, but I
am sure they help when driving in the rain. I have several times been driving in rain
and had to wait for the brakes to clear water to get them to working. I am talking
several car lengths worth at speed, and as far as I am concerned, any reduction is a
positive one.
David
-----Original Message-----
From: Brian Daley <[EMAIL PROTECTED]>
Sent: Mar 10, 2004 2:56 PM
To: [EMAIL PROTECTED]
Subject: Re: [UUC] Cross drilled? (was: Time for F rotors and pads -
Search the ARCHIVES:http://www.mail-archive.com/[EMAIL PROTECTED]
-----Original Message-----
From: "chet.dawes" <[EMAIL PROTECTED]>
>The cooling effect of the drilled holes is minimal and probably offset
>by the reduced heat capacity of the rotor due to the lost mass. The
>airflow is perpendicular to the drilled holes and moves outward in the
>radial direction from inertia and the pressure created by the fins on
>the interior of the rotor not in/out of the drilled holes. If anything,
>it could destroy the flow characteristics of the cooling passages and
>allow air to escape (assume for a second it does travel in/out of the
>holes) through a shorter path permitting less heat transfer to the air
>from the rotor surface. The radiant heat transfer from the additional
>surface area is the only 'real' added cooling. I believe even that is
>minimal.
Chet,
I don't disagree with your conclusion, but wouldn't the air flowing through the vented
rotor draw air through the drilled holes as it passes across them due to the Venturi
effect? This stuff gets complicated in a hurry. I guess it's a matter of knowing
which of these effects are significant. A lot of engineering seems to involve
determining what simplifying assumptions you can make and still have a model that
remains close enough to the behavior of the physical system to be useful.
>The reduced mass rotational inertia argument falls apart (within reason,
>we're not talking huge changes here) when you recognize that heat
>capacity is what you're after. The stock solid rotors on my 318ti have
>nearly half the rotational inertia of the vented variety. However, all
>else being equal (piston diameter, rotor diameter, pads, swept area,
>etc) the car just plain will does not have the braking capacity and
>therefore is slower because you'll boil the fluid and over-heat the pad.
>That's why I have 328 calipers and vented rotors on the car!
I wasn't suggesting that the reduced rotating mass was beneficial to braking, just
beneficial in general. A lighter rotor means less unsprung weight, and less rotating
mass to accelerate. As I said, pretty much irrelevant on a street car, but every
little bit helps in a serious race effort.
That said, I replaced the pads and rotors at all 4 corners on my 325ic last weekend.
Maybe it's my imagination, but I swear I can feel a difference (decrease) in
acceleration. The car just *feels* heavier. I didn't think to weigh the new rotors
before I put them on. I wonder what the increase in mass is compared to the old
rotors.
>Effectively your braking capacity is directly proportional to the added
>heat capacity (mass) of the rotor. SO if you increase the mass by 25%,
>your ability to absorb braking energy (transferred to heat) just went up
>about 25%. Yes, the rotor has to absorb the energy/heat before it can
>transfer it to the surrounding air!
Good point! The average temperature of the rotor would increase due to the reduced
mass but I was speculating that the increased surface area might increase the rate of
heat transfer out of the rotor enough to offset it. The increased temperature
differential between the rotor surface and the air would also increase the rate of
heat transfer out of the rotor as well, no?
>You don't want the rotor to hold
>heat (that's why vented is so much better than solid of the same mass),
>you want it to absorb and dissipate it as quickly as possible. Holding
>heat in the rotor means transferring it to the pad/fluid/wheel bearing
>etc. and obviously that's not the goal. Adding mass changes the rate of
>temperature change (slower) in both directions heating and cooling (as
>Gary indicated). However, increased mass means less temperature rise
>for the same energy absorption, so the same braking maneuver that would
>over-heat a lighter mass rotor would not with a higher mass rotor with
>more capacity.
I guess that's what it comes down to - the limiting factor is heat capacity, as the
rotor will always have to absorb heat faster than it can dissipate it so the more heat
it can absorb the harder it is to induce fade.
Thanks for the insight!
Brian
__________________________________________________________________________
In memory of Michel Potheau - friend, enthusiast, founder of the BMW CCA.
UUC Motorwerks - BMW Performance Fine-tuning and home of the Ultimate
Short Shifter - accept no substitutes!
908-874-9092 . http://www.uucmotorwerks.com
------------------------------
Date: Wed, 10 Mar 2004 23:20:53 -0500 (GMT-05:00)
From: Maverick <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: Re: Cross drilled? (was: Time for F rotors and pads -
Message-ID: <[EMAIL PROTECTED]>
I pretty much agree with this reply and I have come to pretty much come to these same
conclusions, except for one other advantage to cross-drilled or possibly slotted
rotors---clearing water when driving in rain.
I have several times had a problem with this. One heavy rain storm I was doing about
60 on nice fresh BFG KDW's and had to hit the binders and I know I went at least 4 to
6 car lengths before I had any break effect at all and probably another 2 to 3 until
had full breaking power.
I don't know about the rest of you folks, but BMW's fix of dragging my foot all the
time while driving in rain is ludicrous.
David
-----Original Message-----
From: "chet.dawes" <[EMAIL PROTECTED]>
Sent: Mar 10, 2004 10:30 AM
To: [EMAIL PROTECTED]
Subject: [UUC] Cross drilled? (was: Time for F rotors and pads - thinking Zimmerman
(TMS))
Search the ARCHIVES:http://www.mail-archive.com/[EMAIL PROTECTED]
Okay, I'll bite.
'Drilled' rotors:
Originally were developed when pads sucked and out-gassed like crazy to
help allow gasses to escape from the pad/rotor interface. Since pad
technology has improved drastically in the last 40 years, the need for
drilled rotors has become a marketing tool and a way for companies to
extract a few more bucks from consumers for the 'cool factor' of drilled
rotors. I have absolutely no problems with that aspect as long as
people are honest about why they do it.
Yes, Porsche's high end 'drilled' rotors actually have cast holes. The
reason is drilling into a cast iron surface creates stress risers and
due to the residual stress in the cast rotor will cause cracks after
sufficient heat cycling. That's also why drilled rotors have chamfered
holes (the good ones are NOT a 45 degree flat chamfer) and are usually
peened for additional strength at the hole to reduce this tendency.
The cooling effect of the drilled holes is minimal and probably offset
by the reduced heat capacity of the rotor due to the lost mass. The
airflow is perpendicular to the drilled holes and moves outward in the
radial direction from inertia and the pressure created by the fins on
the interior of the rotor not in/out of the drilled holes. If anything,
it could destroy the flow characteristics of the cooling passages and
allow air to escape (assume for a second it does travel in/out of the
holes) through a shorter path permitting less heat transfer to the air
from the rotor surface. The radiant heat transfer from the additional
surface area is the only 'real' added cooling. I believe even that is
minimal.
The reduced mass rotational inertia argument falls apart (within reason,
we're not talking huge changes here) when you recognize that heat
capacity is what you're after. The stock solid rotors on my 318ti have
nearly half the rotational inertia of the vented variety. However, all
else being equal (piston diameter, rotor diameter, pads, swept area,
etc) the car just plain will does not have the braking capacity and
therefore is slower because you'll boil the fluid and over-heat the pad.
That's why I have 328 calipers and vented rotors on the car! For a
motorcycle with nearly no limit to the rotor diameter, they use solid
rotors (very thin) with minimal swept area and reduce mass and therefore
inertia by cross drilling since the heat capacity is so far above what's
needed to stop something that weighs that little. Feel is more
important than capacity in that case.
Effectively your braking capacity is directly proportional to the added
heat capacity (mass) of the rotor. SO if you increase the mass by 25%,
your ability to absorb braking energy (transferred to heat) just went up
about 25%. Yes, the rotor has to absorb the energy/heat before it can
transfer it to the surrounding air! You don't want the rotor to hold
heat (that's why vented is so much better than solid of the same mass),
you want it to absorb and dissipate it as quickly as possible. Holding
heat in the rotor means transferring it to the pad/fluid/wheel bearing
etc. and obviously that's not the goal. Adding mass changes the rate of
temperature change (slower) in both directions heating and cooling (as
Gary indicated). However, increased mass means less temperature rise
for the same energy absorption, so the same braking maneuver that would
over-heat a lighter mass rotor would not with a higher mass rotor with
more capacity.
Obviously there is a trade off and you'd ideally size the rotor to the
mass of the vehicle and it's intended use (speed, tire grip, and braking
conditions) so you don't have more capacity than will be needed in the
worst case. That allows minimal rotational inertia with the greatest
energy absorbing capacity for the application. Too much of a good thing
applies since pads have a temperature dependency on their effectiveness.
In practice, drilled rotors have little or no benefit in my opinion. I
would not waste your money buying them drilled. If you want to scrape
away the pad glaze, buy your rotors slotted. Very little stress change
in the cast rotor since it does not go all the way through and a better
"cheese grater" effect, or pad bite than chamfered holes (more of a
cheese slicer I suppose). Look at high end road racing cars, most are
running slotted floating rotors these days as opposed to drilled rotors
for exactly those reasons.
Ultimately if you want to stop faster, it takes tires with more grip to
do so. If you want to brake harder more often, you need fade resistance
(heat capacity) and cross drilling does not help in that department.
Any *potential* cooling advantage is offset by lost swept area and heat
capacity.
Sorry for the long-winded response.
Chet Dawes
(you asked for an engineer's input....) :)
From: [EMAIL PROTECTED]
I can only think of two advantages to drilled rotors:
1. Cooling.
2. Scraping the glaze off the pads before it transfers to the rotors.
Disadvantages:
1. Unless you increase the size of the rotor, you have less metal to
heat
up. Braking converts motion to heat, so you don't want to reduce heat
capacity.
2. Your pads will not last as long (the cheese grater effect).
I'd stick with a good quality rotor (like Balo), choose better pads and,
if
your brakes are fading, switch to higher temp brake fluid and improve
cooling by ducting more air to the brakes.
Well, you asked.
Scott Miller
From: Brian Daley <[EMAIL PROTECTED]>
I'd also add 3. Reduced rotating weight (the best kind to get rid of!)
Of course this is entirely irrelevant in a street application.
Less metal to heat up, but more surface area to dissipate heat. Heat
capacity isn't really the critical factor - you don't want the rotors to
absorb heat, you want them to radiate heat. Reduced mass might have an
effect on the probability of warping though, not sure about that aspect.
Any engineers out there who know the math to calculate the net effect of
lost mass vs. increased surface area?
I'd also add 3. Increased likelihood of cracking around the drilled
holes (although this seems to be largely a matter of religious belief on
both sides of the argument). If I recall correctly the big dollar
"drilled" rotors on Porsche GT2's etc. aren't actually drilled, the
holes are cast into the rotors. Any materials scientists out there who
know about the grain structure of cast iron and how drilling affects it?
Brian
Added mass causes the rotor to heat and cool more
slowly. Added surface area increases convection. The
answer is it depends. With long stops and long
cooling periods in between the added mass may be
better. With many shorter stops, the added cooling
may be better. It also depends on if your brakes are
ducted properly to take advantage of the extra
cooling.
Gary [no answer today] Derian
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__________________________________________________________________________
In memory of Michel Potheau - friend, enthusiast, founder of the BMW CCA.
UUC Motorwerks - BMW Performance Fine-tuning and home of the Ultimate
Short Shifter - accept no substitutes!
908-874-9092 . http://www.uucmotorwerks.com
------------------------------
Date: Wed, 10 Mar 2004 20:37:06 -0800
From: "Marco Romani" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Subject: Re: [e36 M3] SS brake lines
Message-ID: <[EMAIL PROTECTED]>
I can get brembos for around $50, I haven't found floaters for less than
$130. The Euros do look cooler ;-) but you will not get any improvement in
braking.
cheers,
Marco
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of Sean Cordone
Sent: Wednesday, March 10, 2004 11:19 AM
To: [EMAIL PROTECTED]
Subject: Re: [UUC] [e36 M3] SS brake lines
Search the ARCHIVES:http://www.mail-archive.com/[EMAIL PROTECTED]
Wasting money on the M3? Hah, well yeah, that's probably true, but the
incremental cost for the Euro rotors is really nominal IMHO, so I'm checking
'em out. The design relative to the US spec rotors is compelling to me. And
who hasn't wanted to check out all the E36 Motorsport Euro gear that we
didn't get stateside?
As for the SS brake lines, I'll probably pass.
I've always run ATE Super Blue, but after running a few gallons through the
lines the benefits of bleeding start to approach 0. <\sarcasm>
--SC
> Marco Romani wrote:
>
> > the biggest bang for the buck for pedal feel is bleeding your brakes.
You
> > will get a slightly better pedal feel for SS lines. And I replace mine
> > every two years on the race car. A more aggressive pad will help pedal
feel
> > the most.
>
> also, most SS lines need to be replaced most often than the stock rubber
> ones. for a street car it seems like overkill.
>
> > BTW - IMHO you wasted $$ on the floating rotors. I have never warped
the
> > regular ones (even without ducting) and they're not "that much" heavier.
>
> I agree. floating rotors are only better at fade resistance & add nothing
to
> street performance of the car (unless you're braking enough to induce
> fade which means you're driving too hard on the street IMHO). given that
> you can get solid brembo replacements for ~$50/rotor I seriously doubt
> that you'll get anything close to 3x the use out of the floating ones
either,
> esp
> on the street.
--
_____________________________________________________________
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Powered by Outblaze
__________________________________________________________________________
In memory of Michel Potheau - friend, enthusiast, founder of the BMW CCA.
UUC Motorwerks - BMW Performance Fine-tuning and home of the Ultimate
Short Shifter - accept no substitutes!
908-874-9092 . http://www.uucmotorwerks.com
------------------------------
End of [bmwuucdigest] digest(10 messages)
**********
