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#1. RE: [E36M3] Weekend report :) (GC coilover review, other stuff)...LONG - from Kit Wetzler
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Date: Thu, 25 Apr 2002 03:03:37 -0700 From: Kit Wetzler <kitwetzler@mindspring.com> Subject: RE: [E36M3] Weekend report :) (GC coilover review, other stuff)...LONG > Huh? How is 100# to compress 1 inch and 200 pounds to compress 2 inches > progressive? F=kx where k is the spring rate and x is the displacement. More force is required to compress a spring 1" than 2". Spring rate is the rate of linear INCREASE per inch in force required to move that spring. :) It gets progressively stiffer the more you compress it. Sure, it's a linear spring rate, but it takes a progressly larger force to compress it. -kit
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#2. RE: H&R Sport Spring Rate? - from Bob Stommel
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Date: Thu, 25 Apr 2002 07:45:08 -0500 From: Bob Stommel <rstommel@iquest.net> Subject: RE: H&R Sport Spring Rate? Here are the spring rates of various springs for the E36 M3: Spring Front Rate Rear Rate Stock E36 M3 105 335 LTW E36 M3 138 402 Eibach Pro Kit M3 148 428 Sachs M3 coilovers 215 395 H&R 29910 (Sport) 200 380 H&R 29910 DTM 345 515 Except for the DTM springs, all of these are progressive. Unfortunately, I've never seen any data on the rate changes as the springs compress. Somebody would have to spend a lot of time testing them on a spring tester and record the various changes in rates through the compression range. I'm sure the manufacturers have done this, but they don't publish the data. The range of spring travel depends on type of shocks used, shock settings, total weight of car, weight distribution, etc. So you can't really generalize on how a progressive spring will react for all E36 M3s. This is why one person may find a certain suspension setup to be great on his/her car, while another person with a similar (but not identical) car will say it's too stiff, too soft, sways too much or too little, hits the bump stops, etc. HTH, Bob Stommel Monkey Wrench Racing (a tiny little division of SPG Motorsports) Indianapolis >Date: Wed, 24 Apr 2002 21:50:58 -0700 >From: "Chris Teague" <cteague@cox.net> >Subject: H&R Sport Spring Rate? >Since we are comparing spring rates and progressive >vs. non-progressive, anyone have any idea what the >spring rate(s) are for the H&R sports as compared to >stock and Eibach? >Are they really progressive in the compression range >used on the M3? >Chris >97 M3/4 >with the H&R Sports/Eibach/Koni DA's
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#3. Re: Eibach M3 Springs - from Bob Stommel
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Date: Thu, 25 Apr 2002 08:13:55 -0500 From: Bob Stommel <rstommel@iquest.net> Subject: Re: Eibach M3 Springs When you look at these charts, keep in mind two things (these apply only to "track" suspensions, not to OEM street suspensions): (1) After the car is down off the jacks and has slightly compressed the spring with static weight, the typical spring travel in compression with aftermarket shocks (Konis, Bilsteins) is about 3 inches total travel (in the very tight corners and under heavy braking). The stiffer the shock in compression, the less the travel. For other areas on the track, the springs and shocks are going through micro-movements. So a better spring test would collect data through smaller increments of movement starting from the static weight compressed length and moving down 3 inches. The critical range is 0-2 inches. Hint: If you want to measure the amount of shock/spring travel for any given car, track, etc., put a zip tie on the bottom of the shock rod and then look at it after a few laps. I use bright, fluorescent orange zip ties for this because they are easy to see under the wheel wells. You can find them in any Honda "performance" shop. ;-) (2) It's not just the amount of force for compression and rebound that matters, but also the rate of compression and rebound. The rate of movement is controlled by the shocks during the transitions (corner entry and corner exit). In mid-corner, after the car has "taken a set", the springs and swaybars do most of the work. So focus on the suspension parts that affect the behavior you want to change for the particular phase of the corner that needs to be corrected. If you want to change the car's behavior on corner entry or corner exit, change the spring rates and/or the shocks. If you want to change the car's behavior in mid-corner, change the spring rates (at full compression for your particular car) and/or the swaybars. HTH, Bob Stommel Indianapolis >Date: Wed, 24 Apr 2002 15:52:53 +0000 >From: "Ron Buchalski" <rbuchals@hotmail.com> >Subject: Re: Eibach M3 Springs >Comparing this data to: >http://www.bmw-m.net/techdata/spring.htm >and >http://www.uucmotorwerks.com/html_techtip/techtips/e36_m3_spring.htm >(some of the same data) >The front springs are moderately stiffer than stock and Dinan, but the rear >springs are SIGNIFICANTLY stiffer than stock. Based on Eibach's statements >about creating a spring set with proper front-rear balance, does this imply >that the rear springs of a stock E36 M3 are way too soft? >How do these spring rates compare to H&R OE Sport and Sport springs? >-rb
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#4. Re: Rear wheel lifting during autox - from Dorffer, Rich
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Date: Thu, 25 Apr 2002 09:42:41 -0400 From: "Dorffer, Rich" <RDORFFER@CleIndians.com> Subject: Re: Rear wheel lifting during autox Eric says > > Front roll stiffness really helps reduce oversteer on > our cars due to the difference in the front and rear camber curves. > So try stiffening the front sway bar and see if that helps. I was full > stiff rear soft front and not happy with the understeer. 2 notches > stiffer in the front dramatically helped reduce the understeer. Isn't it contradictory to say "Front roll stiffness really helps reduce oversteer" and "2 notches stiffer in the front dramatically helped reduce the understeer". One of these statements appears incorrect and I am not sure whether I truly agree or disagree with you. Regards, Rich
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#5. Speeding Ticket Advice? - from Dorffer, Rich
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Date: Thu, 25 Apr 2002 09:59:26 -0400 From: "Dorffer, Rich" <RDORFFER@CleIndians.com> Subject: Speeding Ticket Advice? Peter says > > I got a ticket on the 12th -- radar recorded me at 68 in a 40. This is the > first time I got a notice that says "Mandatory Appearance", so I'm a little > freaked out. If you want to be freaked out, be freaked out about the ticket in general (fines and court costs) and the impact it may have on your insurance premiums (i.e., increased premiums). > Anyone know of a good traffic attorney in the SF Bay Area? Lot's of people here from the Bay, I am sure someone here can help. > Can a lawyer help me get this plead down to something reasonable? Yes, quite possibly they can. Maybe they can't. I myself got my last speeding ticket (42 in a 25) along with a seat belt infraction (which really got me pissed since I was wearing mine at the time but took it off to get my wallet when the cop approached the car) plead down to a non-moving violation just for appearing in court. I plead not guilty to both counts (since I was going to court, might as well fight the speeding ticket too) at my first appearance and went for trial at a later date. I showed up just to try to get the seat belt infraction eliminated (at a minimum) or thrown out along with the speeding ticket (best case scenario) if the cop didn't appear (Cleveland...so they were busy and just trying to move things along). The court was packed (lot's of more interesting cases than mine based on what I saw). The cop appeared at the last minute (much to my chagrin but they do get paid to appear) but he wanted to leave and told the DA that when she approached him. The DA approached me and asked why I came and I told her that I was going to fight it (I had very little idea what I was doing, I had no representation with me, but I had done some homework about radar and potential problems in the area I was cited) and she agreed to make it a non-moving violation (tail light out), confirming with the cop if he was alright with this, if I plead "no contest" prior to my case ever being called. I considered myself quite lucky since I did not have to do anything really and only got hit with $120 in fine and court costs with just one non-moving violation. > I'm afraid that the mandatory appearance means bad things... am I wrong? No, it typically results whenever the speeding ticket exceeds a certain prescribed amount (say more than 20mph over the posted speed) or you have had a certain number of moving violations (points). YMMV and I am not a lawyer. Good luck though. Later, Rich
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#6. Re: Weekend report (looking ahead on track) - from KLchmn@aol.com
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Date: Thu, 25 Apr 2002 10:05:28 -0400 From: KLchmn@aol.com Subject: Re: Weekend report (looking ahead on track) Donna writes: >LOL! You should go out with Sherman Koo, the master of >teaching 'looking so far ahead.' That's who taught me to look far ahead! Also, don't forget the Sherman mantra: 'check your mirrors, check your gauges, breathe'. The last time I had Sherman 'the German' as an instructor was at Buttonwillow. Sherman had me talk him through some laps telling him what I was looking at. Since he does this every time, I had a surprise for him. Going down the back straight (clockwise, for those who know), I rattled off the usual "I'm scanning down the track past the flag station, no problems, found my turn in mark, now I see the coast line, the Pacific ocean, hey! there's Hawaii!" Sherman liked it! Cheers, Kirk Lachman Sin City Chapter '95 M3 #21 I-stock
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#7.Michelin MXX3 234/40/17 - from Dorffer, Rich
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Date: Thu, 25 Apr 2002 10:34:08 -0400 From: "Dorffer, Rich" <RDORFFER@CleIndians.com> Subject: <WTB> Michelin MXX3 234/40/17 My bad luck with tires continues. Anyone have one unused Michelin MXX3 234/40/17 kicking around that they would like to sell. I was trucking in to work this morning when the brand new one I just put on my car had its sidewall separate (no pot hole, no explanation, properly inflated when I left this morning). Tire Rack is completely out and the tire does not carry a warranty anyway since it has been discontinued. I have three other brand new ones that I had planned to combine with the one new one that was on my car this week so if I can't find one, is anyone interested in buying any of the three spares I may soon have? Thanks, Rich
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#8. Re: [E36M3] Who Cares about spring rate linearity in rebound - from The Buch
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Date: Thu, 25 Apr 2002 07:44:03 -0700 From: The Buch <the_buch@telus.net> Subject: Re: [E36M3] Who Cares about spring rate linearity in rebound Chester .. I think you have a good argument .. two additional thoughts I would add: 1. The total deflection of the suspension would vary in a relative sense for progressive and linear - take the example of supporting an additional 400# where a linear spring of 200#/" and a progressive spring of 175#/" for the first inch and 225#/" for the second inch would both have the same deflection .. then, less than 400# of compression force would result in the progressive spring deflecting more than the linear spring and more than 400# would result in the linear spring having the greater deflection. 2. Just by the way they work, are shocks and struts not also progressive? If so, on compression this would match a progressive spring nicely, but on rebound, the progressiveness of the shock and spring would actually be mismatched. This would suggest a higher rebound dampening for initial extension travel, which I would agree would ultimately lead to a sluggishness at the last part of the extension travel through static height where the spring acceleration is lower? Regards, Doug Chester Wong wrote: > --- The Buch <the_buch@telus.net> wrote: > > Would it be fair to say that for a given bump, requiring compression of > > the suspension to absorb the energy transmitted from the road into the > > suspension, that every spring will have the same amount of potential > > energy stored in it in the compressed state (yes this ignores any > > differences in the energy losses to the compression dampening of > > differing struts or shocks)? This energy now needs to be reconverted > > back into kinetic energy on rebound, so that as the suspension extends > > through equilibrium the upward velocity of the car would be identical > > for progressive or linear springs of any rate (again assuming similar > > energy absorption in rebound dampening). Yes the 'feel' might be > > slightly different because the initial acceleration would be higher in a > > progressive spring and then decrease - is this the sensation of > > bounciness that Chester refers to? But I hypothesize that the > > performance of the suspension in managing weight transfers created by > > This will probably be the last time I comment on this as I'm not out to > convince the world... > > But...yes, total energy stored would be the same for a given bump; however, for > the same bump, the spring will compress more for the linear rate spring than > the progressive rate spring. Just keep F = kx in your head. If k is a > function of x, then you can subsitute k back into the equation and you'll get > something definitely not linear. > > Anyway, in your given scenario, yes, the initial force the spring is exerting > back onto the rebound part of the dampener is greater for the same displacement > of the spring. Force is also related to acceleration, right? So...if you have > your dampeners tuned (rebound-wise) so that it can handle the small, choppy > bumps with ease, when you compress the suspension past the small amplitude > (think big bump), the force is much greater for a progressive spring. This > returning force can accelerate the assembly past the static ride height and > will also feel like the wheel is jumping up. Now let's say you tune the > rebound so that the big bumps don't do this. Well, now on the small > undulations, your suspension will be sluggish....so you'll feel the slight > bounciness as well. > > At any rate, it is my belief that going with a progressive rate spring..you > need to compromise on the settings. To me, this compromise is unnecessary > since one can go with linear rate springs and tune the shock to the spring. > Not sure why people would consider progressive rate springs unless it's for the > sole purpose to prevent bottoming out a suspension if you lower the car. Also, > the theory sounds good...for the first initial displacement, the spring rate is > light, but when you're cornering and pass the small displacement, the spring > magically stiffens up and offers better roll resistance. Sounds good on paper, > but you most likely need a dampener that can match this varying spring rate. > > Just my $.02 > Chester > > ===== > > __________________________________________________ > Do You Yahoo!? > Yahoo! Games - play chess, backgammon, pool and more > http://games.yahoo.com/
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#9. Tire size advise? - from Paul Rubio
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Date: Thu, 25 Apr 2002 11:00:29 -0700 (PDT) From: Paul Rubio <redoctagon@yahoo.com> Subject: Tire size advise? Well fellas, Its about that time...I was out driving the other day on one of my favorite routes(Kings Mt. Road for those interested) when I hit some some type of random runoff as I down shifted...and for one glorious, yet brief moment but not too brief as to miss a couple of heart beats, my rear tires slid out very unexpectedly and unnaturally(at least to what I'm use to). Well to make a long story short, I recovered and made it home alive. Checking my tires, I confirmed my suspicion; after 26000 miles it was probably time to retire these bad boys. Question, is it normal the outer part of the tire to be more worn than the rest of the tire? I assumed yes because of negative camber? I'd like to replace them with slightly larger tires, but... has anyone had/heard of any problems putting P235/45/ZR17 f and P255/40/ZR17 r tires on stock '99 M3 Wheels? I vaguely remember someone mentioning that there may be problems with ASC+T computer getting confused at highway speeds? Any advise would be appreciated. paul __________________________________________________ Do You Yahoo!? Yahoo! Games - play chess, backgammon, pool and more http://games.yahoo.com/
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#10. Re: [E36M3] Who Cares about spring rate linearity in rebound - from Ron Buchalski
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Date: Thu, 25 Apr 2002 18:01:42 +0000 From: "Ron Buchalski" <rbuchals@hotmail.com> Subject: Re: [E36M3] Who Cares about spring rate linearity in rebound Chester, I'm sure this thread won't be over for a long time! Let me add some thoughts to the mix... Isn't it true that the design of Bilstein's (monotube) valving is such that it's velocity-sensitive? http://www.bilstein.com/products/mono.html The spring steel valving discs deflect different amounts based on the rate of oil flow, thus providing a variable amount of damping based on the velocity of the piston movement. If you had a fixed size oil passage in the working piston that allows a fixed maximum flow rate of oil, slow or small piston excursions that push oil at or below this fixed oil flow rate would be hardly damped, and any piston excursion that pushed the oil at a rate above this maximum flow rate would be damped at a fixed amount. The spring steel valving discs will deflect a variable amount, dependent on the flow rate of the oil (assume that the valving discs are linear springs, so F=kx), to provide a variable amount of damping. So, Bilstein's monotube dampers should be well-suited to linear or progressive rate springs, since they only react to the velocity of the working piston within the monotube. And, while it should be possible to use different rate valving discs for compression and rebound, I don't know if standard Bilstein dampers are made this way, or if compression and rebound damping are the same. Perhaps the custom valving program allows this to be done. Koni, on the other hand, allows you to manually adjust the rate of oil flow through the working piston, but it's still a static setting once it's adjusted. The SA damper only allows rebound damping, while the DA allows compression and rebound damping to be adjusted independently. Whether this is better than Bilstein's variable valaving design, or just different, probably depends on the application (street, track, race). They have a short video on their website that talks about damper technology: http://www.koni-na.com/shock_video.ram (It's a realplayer movie, and the quality isn't too good). Now, back to linear vs progressive springs. For a given amount of force (say, 500lb), the linear spring will compress a linear distance, (F=kx) and the rate of compression should be constant. A progressive spring will not compress a linear distance, and it's rate of compression should also be non-linear, since it's offering a variable amount of resistance to the force. In fact, as the spring compresses, it's rate of deflection should initially be faster than the linear spring, and become slower than the linear spring, as it nears the end of it's compression for the given load. Conversely, a linear rate spring should return it's stored energy linearly, while a progressive rate spring will return it's stored energy in a non-linear way, starting much quicker and slowing as the spring rate decreases. So, perhaps Bilstein's valving disc technology is better suited for use with progressive rate springs (provided they aren't riding on the bump stops). Also, through this discussion, bump stops have been mentioned, but I think we're talking about two different things. There are external bump stops that are installed below the RSM or upper strut mount, and there are internal bump stops (at least, Bilstein has them). I think that bump stops were mentioned in this thread, but the distinction between internal and external was not made. A nit... Anyhow... Eibach says that they use progressive rate springs to provide a better all-around spring for street use, since the environment varies much more than you'll experience on paved race tracks. So, for small amounts of suspension travel, the spring will travel a longer distance, and smooth out the ride. For larger travel distances (acceleration, braking, hard cornering), the springs will stiffen up as they compress, firming up as needed to limit the travel distance. I think the main reason to use progressive rate springs is to allow a car's ride height to be lowered, but still retain near-stock spring rates for small amounts of spring compression. Ultimately, you're limited by suspension travel, and the springs must control the amount of spring travel for a given amount of force. If you reduce the distance of travel (by changing the ride height), you need to compensate with a firmer spring. So, once again, it's a tradeoff. Racers use linear springs, and can live with very low ride heights, and a stiff ride 100% of the time. Street cars are more suited to progressive rate springs when ride height is decreased. We did determine that stock M3 springs are linear, right? My $0.02, -rb >Date: Wed, 24 Apr 2002 21:56:27 -0700 (PDT) >From: Chester Wong <chester_p_wong@yahoo.com> >Subject: Re: [E36M3] Who Cares about spring rate linearity in rebound > <snip> > >This will probably be the last time I comment on this as I'm not out to >convince the world... > <snip> > >Anyway, in your given scenario, yes, the initial force the spring is >exerting >back onto the rebound part of the dampener is greater for the same >displacement >of the spring. Force is also related to acceleration, right? So...if you >have >your dampeners tuned (rebound-wise) so that it can handle the small, choppy >bumps with ease, when you compress the suspension past the small amplitude >(think big bump), the force is much greater for a progressive spring. This >returning force can accelerate the assembly past the static ride height and >will also feel like the wheel is jumping up. Now let's say you tune the >rebound so that the big bumps don't do this. Well, now on the small >undulations, your suspension will be sluggish....so you'll feel the slight >bounciness as well. > >At any rate, it is my belief that going with a progressive rate spring..you >need to compromise on the settings. To me, this compromise is unnecessary >since one can go with linear rate springs and tune the shock to the spring. >Not sure why people would consider progressive rate springs unless it's for >the >sole purpose to prevent bottoming out a suspension if you lower the car. >Also, >the theory sounds good...for the first initial displacement, the spring >rate is >light, but when you're cornering and pass the small displacement, the >spring >magically stiffens up and offers better roll resistance. Sounds good on >paper, >but you most likely need a dampener that can match this varying spring >rate. > >Just my $.02 >Chester _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp.