[uucdigest] Friday, February 7 2003 Volume 03 : Number 6097
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Send 'em to [EMAIL PROTECTED] |__________________________________________________________________ In this BMW UUC Digest: Re: [uuc] E36 sways, WTB M3 rear Re: [uuc] E36 sways, WTB M3 rear Re: [uuc] E36 sways, WTB M3 rear Re: [uuc] E34 525iA post balance shimmy Re: [uuc] E36 sways, WTB M3 rear Re: [uuc] E28 M5 FS $5000.00 Re: [uuc] E36 sways Re: [uuc] E36 sways, WTB M3 rear Re: [uuc] E36 sways, WTB M3 rear [uuc] Understeering Drivers was re: E36 bars/weight transfer ---------------------------------------------------------------------- Date: Fri, 7 Feb 2003 12:38:35 -0600 From: [EMAIL PROTECTED] Subject: Re: [uuc] E36 sways, WTB M3 rear "Neil N." <[EMAIL PROTECTED]> wrote: > If the information below is accurate (which I have no reason to doubt), > then simply changing to the M3 rear bar (+1 mm compared to 325) wouldn't > have as large an impact as going to the whole set. Neil, Everything is relative and +1mm bar diameter increase is not much, but getting a stiffer rear bar will promote oversteer/reduce understeer. > As Matt said, part of the equation is the ratio of F/R stiffness, > and that's why the smaller (-1.5 mm compared to 325) front bar helps > reduce M3 understeer in connection with the larger rear bar. Not. Front M3 sway bar is a LOT more effective than larger 325/328 sway bars due to the M3 bar's attachment to the middle of the shock tower vs. control arm on regular E36 cars. > I'd try to go for the whole M3 set. He can't. Non-M3 E36 strut towers do not have a sway bar attachment bracket on the shock tower. > Chris Baker <[EMAIL PROTECTED]> wrote: > > Just to better my own understanding, is this correct? What I've been > > told, by what I thought were reputable sources, was that increasing > > the stiffness of the rear bar actually transferred more weight to the > > front inside tire, increasing grip there and reducing understeer. I > > know I've seen Gary comment on this before and thought his comments > > were along the same lines - is that right Gary? Chris, I'm not sure about the theory, but you are basically right in your conclusions. Here is the handling adjustment matrix you want: HANDLING ADJUSTMENTS Adjustment To Increase Understeer To Increase Oversteer - - - -------------------------------------------------------------------------- Front Tire Pressure Decrease Increase Rear Tire Pressure Increase Decrease - - -------------- Front Wheel Camber More Positive More Negative Rear Wheel Camber More Negative More Positive - - -------------- Front Springs Stiffer Softer Rear Springs Softer Stiffer - - -------------- Front Sway Bar Larger (Stiffer) Smaller (Softer) Rear Sway Bar Smaller (Softer) Larger (Stiffer) > Regardless of the theory, It sounds like there is something to be > gained from an M3 bar. I definitely can't get away with $350-$400 > for a new aftermarket bar set, Sure you can! > so is there any reason I shouldn't just try an M3 rear bar? It wont make much difference. But if you get it for free or at most $50, than have fun. alex f ------------------------------ Date: Fri, 07 Feb 2003 13:58:09 -0500 From: "Dave Kelley" <[EMAIL PROTECTED]> Subject: Re: [uuc] E36 sways, WTB M3 rear > > Anybody got a used 96+ M3 rear bar they want to sell? > > Thanks, > > Chris B. > I have a front and a rear M3 bar from a 98. Make me an offer! Dave Kelley 98 M3/4 94 325i ------------------------------ Date: Fri, 07 Feb 2003 13:59:47 -0500 From: "Dave Kelley" <[EMAIL PROTECTED]> Subject: Re: [uuc] E36 sways, WTB M3 rear > Chris, > If the information below is accurate (which I have no reason > to doubt), then simply changing to the M3 rear bar (+1 mm > compared to 325) wouldn't have as large an impact as going > to the whole set. As Matt said, part of the equation is the > ratio of F/R stiffness, and that's why the smaller (-1.5 mm > compared to 325) front bar helps reduce M3 understeer in > connection with the larger rear bar. I'd try to go for the > whole M3 set. HINW (Hope I'm not wrong), Neil Unabashed plug, Chris. I have the whole set! :-) Dave Kelley 98 M3/4 94 325i ------------------------------ Date: Fri, 07 Feb 2003 13:15:35 -0600 From: Dennis Wynne <[EMAIL PROTECTED]> Subject: Re: [uuc] E34 525iA post balance shimmy Warped brake rotors? Could be the cause if it is that bad under braking. Could be a bent rim, did they rotate the tires (I don't know if your car has the same size all the way around or not) while working on it? Maybe you had the bent rim on the rear and they rotated back to the front? You can also try getting a balance at a place that uses those "road force" balance machines. They don't just spin the wheel/tire, they apply road force type pressure to the tire as it spins. That way any imperfections in the tire will be factored into the balance. Way back when I had my Fiat X1/9 I had the tires balanced before a trip. They vibrated worse on the drive home from the tire store, so I went back. They swore they balanced them all. I watched them put them back on the machine and most were off - but one was OK. Then they turned the wheel on the machine and re-ran it - it came up out of balance. I asked them to run the machine without ANY wheel/tire on it - it came up about 1 oz out of balance! They refunded my money and I stopped at another place and had the tires done correctly. Dennis 330i silver/black/manual/sp/pp/xenon/cd At 10:15 AM 02/07/2003 -0500, Beaudette, Roland wrote: >The car has had an imbalance present since I picked it up last December, >primarily felt during braking. It was quite disconcerting to brake at >highway speeds. Replacing the thrust arms using 750 bushings really helped >as the vibration was reduced to minor pulsating during braking. The next >step was to have the wheels balanced. I used a local Goodyear place that >had treated my alloy wheels fairly well in the past. Now, following the >balance, the car vibrates heavily under breaking again (like when I first >picked it up). > >Have it rebalanced? Suggestions are appreciated. The next item to replace >would be the lower arms (unless someone has a better idea). > >Cheers, > >Roland ------------------------------ Date: Fri, 07 Feb 2003 14:17:25 -0500 From: "Dave Kelley" <[EMAIL PROTECTED]> Subject: Re: [uuc] E36 sways, WTB M3 rear > He can't. > Non-M3 E36 strut towers do not have a sway bar attachment > bracket on the shock tower. I thought they "would" still fit and attach at the stock E36 mouting points? Or in any case, he can just pick up some M3 front struts and swaybar links! I was thinking about installing my M3 bars on my other E36, but hadn't really looked at it yet! Dave Kelley 98 M3/4 94 325i ------------------------------ Date: Fri, 7 Feb 2003 14:20:14 -0500 From: "mike" <[EMAIL PROTECTED]> Subject: Re: [uuc] E28 M5 FS $5000.00 - ----- Original Message ----- From: "Truxtun Jayne" <[EMAIL PROTECTED]> > I have owned & maintained the car for 6 years, never tracked, raced or > smoked. Includes Conforti chip, track pipe, K&N filter, outdoor car cover Hmmm, statements like that always make me wonder what the chip, track pipe and K&N filter are for then, eye candy? haha, just teasing Mike ------------------------------ Date: Fri, 7 Feb 2003 14:23:39 -0500 From: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> Subject: Re: [uuc] E36 sways > Going to a larger front bar and NOT matching it with a larger > rear bar will only increase understeer Interestingly enough, this is not always the case, especially with a macpherson strut front suspension. Especially when you get someone more concerned with asthetics than performance. Lots of people are tempted to lower the front of the e36 such that the fender gap is equal front and rear. This is obviously incorrect because the rear fenders come down farther down than the fronts, lowering the front until they are equal means you lower the front a lot more. (Measure the height of the side skirts to the ground to see what I mean) The problem is that when you lower the car that much, you get out of the favorable camber curve. When a macpherson strut's control arm is anything close to or beyond perpendicular to the strut, you get a host of problems, like camber actually increasing with roll! lots of times when you are in these situations (stock class autoX for example, where you aren't limiting the roll up front with springs) you can actually reduce understeer by going to a larger front sway bar. -kit - -------------------------------------------------------------------- mail2web - Check your email from the web at http://mail2web.com/ . ------------------------------ Date: Fri, 7 Feb 2003 13:32:26 -0600 From: [EMAIL PROTECTED] Subject: Re: [uuc] E36 sways, WTB M3 rear "Dave Kelley" <[EMAIL PROTECTED]> wrote: > > He can't. > > Non-M3 E36 strut towers do not have a sway bar attachment > > bracket on the shock tower. > > I thought they "would" still fit and attach at the stock E36 > mouting points? If you manage to attache an M3 sway bar to the stock E36 non-M3 mounting point (hole in the control arm), you will effectively downgrade to a much narrower front sway bar. > Or in any case, he can just pick up some M3 front struts and > swaybar links! Not so simple Front M3 shocks with sway bar brackets come from only two sources: the dealer$$$ or the junk yard. The former are hideously expensive for POS Boge shocks. The latter are not that much cheaper at around $100/per for dead shocks (they are ALL dead after 30+K miles ;-(. > I was thinking about installing my M3 bars on my other E36, but > hadn't really looked at it yet! I have. My other E36 is my wife's 328i. After I installed Eibach sways on my car, the M3 bars went straight into storage. alex f ------------------------------ Date: Fri, 7 Feb 2003 14:34:50 -0500 From: "James Moran" <[EMAIL PROTECTED]> Subject: Re: [uuc] E36 sways, WTB M3 rear From: <[EMAIL PROTECTED]> > Neil, > Everything is relative and +1mm bar diameter increase is not much, but > getting a stiffer rear bar will promote oversteer/reduce understeer. I dunno the numbers we're talking about, but going from a 19mm to a 20mm bar will increase its stiffness 23%. Torsional stiffness is proportional to diameter^4. > Chris, > I'm not sure about the theory, but you are basically right in your > conclusions. > Here is the handling adjustment matrix you want: > > HANDLING ADJUSTMENTS > > Adjustment To Increase Understeer To Increase > Oversteer snip There are exceptions to the conventional balance/stiffness paradigm. On cars with strut front suspensions, especially VWs, a stiffer front anti-roll will keep the front suspension in a more optimum camber range, increasing front grip and actually reducing understeer. Is this the case with an E36? Dunno. Has anyone suggested camber correcting mounts to increase static negative camber? Jim Moran '88 M6 ------------------------------ Date: Fri, 07 Feb 2003 11:47:56 -0800 From: [EMAIL PROTECTED] Subject: [uuc] Understeering Drivers was re: E36 bars/weight transfer Understeering Drivers was re: E36 Bars/weight transfer: On an E36 with //M3 swaybar style swaybar mounting, a nice front bar where stock springs are required, is the 24mm bar from the earlier E36 4 doors. This slight increase in diameter gives IMO a correct increase in roll stiffness to compensate for the extra traction when using R compound tires and/or better shocks and struts. Thicker than that for a front bar with stock springs was easier to drive but did not give me a faster autocrosser, just proved how wrong the butt dyno can often be. These bars are easily available as take offs for $100. or less. There is also a factory 26mm bar on some E36 S packages for control arm linked swaybars. Takeoffs of those may be hard to find since there is no reason to sway if you have a bar that thick already. If you think you need a thicker front bar than 24mm (M mountings) or 26 (control arm links) first try different shock valvings and alignment changes. Also a rule of thumb for larger front bars is, the thicker the front bar, the lower you make the rear tire pressure. Never underestimate the effect of this. For some people following this swaybar thread, your car might be setup fine for anything you want to do with it already. Just that your rear tire pressures are too high. How many of you set your rear pressures by starting high and going lower? Exactly. Start low and go high. Start your rear tire pressure so low that the tail will twitch at the slightest nudge of the steering wheel whether you want it to or not. Then increase _only until the car will do just what you want but no more. Example: E30, special 1 inch front sway bar, stock (15mm?) swaybar rear. Front pressure set so sidewall rollover is exactly on the edge of the tread. That setup for autocross was 50-54psi front depending on temperature, pavement type, and course speeds. Rear tires pressure worked like a charm at around 27psi. This arrangement was more difficult to drive at the limits. Its limits were greater than if I used a thinner front bar and higher rear tire pressure. Stopwatches don't lie, and this car was a powerful autocrosser no matter who drove it. The factory rear bar, with stock springs, also is fine as is. Add solid bushings if you want or class rules allow it. Weight balance on a car sitting still is different than weight transfer on a car in motion. If you want to get the rear to come around better, try braking harder and/ or lifting the throttle later. Guaranteed to get the tail lighter as you enter the turn than previously. Frequently however the difference between the car plowing like a pig into a cone versus darting around the gate like a pirouetting ballerina requires modification of the contents of the driver seat. Sadly, that is the most overlooked option amidst a pile of prematurely worn out tires and used performance parts for sale ads. Run on street tires. Install a harness. Keep your springs stock. Get a good alignment and accurate tire pressure gauge. So when trying to cure a handling problem, its not always the car. Many times, its an _understeering _driver. Can any amount of performance part$$ can compensate for that? Enjoy, 'jk ------------------------------ End of [uucdigest] V3 #6097 *************************** | | In memory of Michel Potheau - friend, enthusiast, founder of the BMW CCA. |________________________________________ | Please visit these UUC-approved BMW parts vendors/service providers: | (listed alphabetically) | | Autoscope-Motorsports - http://www.autoscope-motorsports.com | |==================================================== | | Koala MotorSport . BMW technical information, special tool sales/rental | http://www.koalamotorsport.com | |==================================================== | | Taylor BMW - http://www.taylorbmw.com - Doc Bimmer! | UUC Motorwerks . http://www.uucmotorwerks.com |__________________________________________
