Ok, I've got the Dinan rear swaybar and Beastpower brackets, very happy with this setup..
Does anyone know if Dinan do a front swaybar? Or is it better to go ACS front and back? Also will the same Beastpower brackets work on the front too?
Are the ACS ones made by Eibach?
Anyone have a pic of the front OEM swaybar?
Ok, I've got the Dinan rear swaybar and Beastpower brackets, very happy with this setup..
Does anyone know if Dinan do a front swaybar? Or is it better to go ACS front and back? Also will the same Beastpower brackets work on the front too?
Are the ACS ones made by Eibach?
Anyone have a pic of the front OEM swaybar?
The ACS swaybars are the same as those found in Eibach's 28/18mm P/N 2054.320 kit selling for $380 at sites like eap4parts.com
Dinan sells a 27mm front bar, but it's the same size as stock. It offers no significant benefit. My guess is it was released for the 540i with it's 25mm bar, before the 2000 M5 was rolled out.
Beastpower rear brackets are excellent and almost mandatory for Dinan or Eibach oversize rear swaybars. Of course you already know that.
The Eibach 28/18 swaybars fit many applications, but they are optimized for their pro 540i spring kit. This Eibach package contains a higher rate rear spring and a stockish rate front spring, compared to stock 540i or M5. The added rear spring bias & 18mm bar work together to maintain decent balance in conjunction with their oversize 28mm front bar. Throwing Eibach bars on an M5 with stock springs will likely result in an understeer condition similar to stock, except body roll will be lessened. Some folks may like this result, but it will not significantly improve performance...as measured with a stopwatch. The key to speed is to create a neutral condition that prevents the front tires prematurely losing traction & "giving up" early. Body roll is strictly a secondary concern...and better roll control offers a false sense of performance.
The need for a larger front bar on an M5 is highly questionable, unless you are running non-stock springs with heavy rear bias & tons of negative camber in the front. Such a combo does not work on the street. All street-tuned M5's will understeer like a pig (or Mustang), unless they have aftermarket springs with lots more stiffness in the rear or an oversize rear bar or a SMALLER front bar. A larger front bar will further abuse the already overworked front tires which means even more understeer. This is not the hot setup. I think a larger, adjustable Dinan rear bar with Beastpower brackets is the best option for folks using stock springs.
Track-level handling will not come from larger swaybars. You need high rate linear springs. Racers invariably use modest size swaybars in conjunction with high rate springs. Some really serious M3 racers choose appropriate springs rates that allow them to remove the rear swaybar! This allows them to put power down sooner & exit corners better. Swaybars transmit forces across the chassis. This upsets traction on both sides of the vehicle when only one tire contacts a road surface imperfection, almost like a solid axle setup. This transfer of torsional force through a swaybar is referred to as suspension crosstalk. Swaybars do not control transients imposed by brakes, acceleration or changes in throttle position, so they have limited value. Swaybars only address lateral pitch. On a laboratory-smooth skidpad with a skilled driver capable of holding steady throttle, swaybars will offer high G's & roll control when you're driving in smooth circles. In real life, they are a very poor substitute for adequate spring rates. Soft springs adversely impact the cars ability to enter or exit corners with changes in braking and throttle. Higher rate springs are needed to maintain stability and manage weight transfer fore and aft during decel dive & accel squat. If you have to wait for the car to pitch & settle/set every time you apply brakes or throttle, the car will not be nimble or responsive.
Hope this helps
Last edited by Lscman; 15th January 2004 at 17:13.
Lscman covered it very well there. ACS sways are the same as Eibach. The frint sway is a PITA to install and will cost a lot in terms of labor time. I cannot tell you if it is worth it as I have never noticed a large difference with one installed on an M5.
The ACS swaybars are the same as those found in Eibach's 28/18mm P/N 2054.320 kit selling for $380 at sites like eap4parts.com
Dinan sells a 27mm front bar, but it's the same size as stock. It offers no significant benefit. My guess is it was released for the 540i with it's 25mm bar, before the 2000 M5 was rolled out.
Beastpower rear brackets are excellent and almost mandatory for Dinan or Eibach oversize rear swaybars. Of course you already know that.
The Eibach 28/18 swaybars fit many applications, but they are optimized for their pro 540i spring kit. This Eibach package contains a higher rate rear spring and a stockish rate front spring, compared to stock 540i or M5. The added rear spring bias & 18mm bar work together to maintain decent balance in conjunction with their oversize 28mm front bar. Throwing Eibach bars on an M5 with stock springs will likely result in an understeer condition similar to stock, except body roll will be lessened. Some folks may like this result, but it will not significantly improve performance...as measured with a stopwatch. The key to speed is to create a neutral condition that prevents the front tires prematurely losing traction & "giving up" early. Body roll is strictly a secondary concern...and better roll control offers a false sense of performance.
The need for a larger front bar on an M5 is highly questionable, unless you are running non-stock springs with heavy rear bias & tons of negative camber in the front. Such a combo does not work on the street. All street-tuned M5's will understeer like a pig (or Mustang), unless they have aftermarket springs with lots more stiffness in the rear or an oversize rear bar or a SMALLER front bar. A larger front bar will further abuse the already overworked front tires which means even more understeer. This is not the hot setup. I think a larger, adjustable Dinan rear bar with Beastpower brackets is the best option for folks using stock springs.
Track-level handling will not come from larger swaybars. You need high rate linear springs. Racers invariably use modest size swaybars in conjunction with high rate springs. Some really serious M3 racers choose appropriate springs rates that allow them to remove the rear swaybar! This allows them to put power down sooner & exit corners better. Swaybars transmit forces across the chassis. This upsets traction on both sides of the vehicle when only one tire contacts a road surface imperfection, almost like a solid axle setup. This transfer of torsional force through a swaybar is referred to as suspension crosstalk. Swaybars do not control transients imposed by brakes, acceleration or changes in throttle position, so they have limited value. Swaybars only address lateral pitch. On a laboratory-smooth skidpad with a skilled driver capable of holding steady throttle, swaybars will offer high G's & roll control when you're driving in smooth circles. In real life, they are a very poor substitute for adequate spring rates. Soft springs adversely impact the cars ability to enter or exit corners with changes in braking and throttle. Higher rate springs are needed to maintain stability and manage weight transfer fore and aft during decel dive & accel squat. If you have to wait for the car to pitch & settle/set every time you apply brakes or throttle, the car will not be nimble or responsive.
Hope this helps
Thanks Lscman that sure does!
I'm in the process of getting the ACS DFC system for the M5, hence was alittle worried about the front stock bar not being able to "keep up" with the other bits and didn't want it to be a limiting factor. With just the Dinan rear bar and BP brackets, it did make a big difference. I thought the front would be similar to the rear bar, hence the post..
Throwing Eibach bars on an M5 with stock springs will likely result in an understeer condition similar to stock, except body roll will be lessened. Some folks may like this result, but it will not significantly improve performance...as measured with a stopwatch. The key to speed is to create a neutral condition that prevents the front tires prematurely losing traction & "giving up" early. Body roll is strictly a secondary concern...and better roll control offers a false sense of performance.
The need for a larger front bar on an M5 is highly questionable, unless you are running non-stock springs with heavy rear bias & tons of negative camber in the front.
Well Said!!
it always seems that everyone wants the biggest swaybars available, to get the flattest cornering. You gotta have some weight transfer!
__________________
Mike
91 M5 Alpine White II, Silver Gray 3/90 production
17x8/17x9 M system with PS2, 20mm touring roll bar; Ground Control Coilovers; EAT Chip, CD43; bmw/nardi blackline steering wheel, 3.8 Cam Gears
08 535i / 6 speed
Space Gray; Gray; Sport/Premium/Nav
00 M5 Ti Silver; Imola/black sportiv --Sold
Engine:
Supersprint Headers, Dinan CAI kit and MAFS, Throttle Bodies, Cams, Ported heads, Exhaust, Custom dinan software, Evosport Pullies, Dinan clutch and lightened flywheel; Ignition solutions plasma coils
Suspension:
Dinan Stage 3 with front and rear Strut Tower Braces, Beastpower Sway bar brackets, Dinan Wheels with 275/285 PilotSport, X5 Thrust arm bushings, Stoptech 355mm 4 piston front, 355mm 2 piston rear brake kit, Dinan 3.45 diff
Interior/Misc:
Eurodash, updated steering wheel, Bluetooth retrofit, Sirius Retrofit, hardwired V1, Widescreen Mk4 nav, M audio retrofit, Ice Link, BSW Stage 1 speaker upgrade, bmw towbar
Lscman covered the tuning aspects of F & R swaybars pretty well, as well as the importance of having adequately high spring rates for performance applications. All of this is more important as power level and vehicle weight increase.
An additional point to make is that a primary purpose of large-diameter sway bars, particularly in the front, is to keep the tire contact patches on the ground. Said another way, to keep the tires from tilting away from perpendicular to the ground as the vehicle rolls on its suspension in a corner - by limiting the amount of roll. From this perspective, manufacturers use stiff sway bars to compensate for ride-oriented low spring rates. This sets up a compromise between what is gained (with respect to cornering force) by keeping the contact patches on the ground vs. overloading the outside contact patch (hello understeer), although the suspension will "set" at corner entry a little quicker with stiff sway bars.
As Lscman points out, real race cars use much higher spring rates and rely less on sway bars. Anything we would care to drive on the street on a daily basis is a compromise that gives away some cornering power.
The severity of tire-tilting, of course, varies with suspension design. The struts used by BMW in the front are not so good in this regard, but the rear is quite good. A full double wishbone front suspension would likely be better, but it's possible to get this wrong as well. And then there's the C2/C3 (1963-82) Corvettes, where both front and rear suspension designs are dreadful. One needs very stiff springs and very stiff sway bars to begin to be able to tap the potential of today's tire technology, and then you run into lack of structural stiffness of the vehicle as a limit.
The example of high rate track springs coupled with a smaller rear swaybar offers the best of both worlds (if you ignore the need for a kidney belt). Stiffer swaybars are good, but they must be biased to provide neutral handling. Swaybars are a nifty way to reduce body roll without impacting ride quality a lot.
As Dick noted, keeping the tire tread flat on the road surface is important. Traction is greatly reduced when the tire sidewall is serving as tread and the inner tread is lifting. McPherson strut suspensions do not dynamically gain much negative camber upon compression or positive camber during droop, so static negative camber must be dialed in or body roll must be controlled to maintain grip. Cutting edge SLA suspensions found on the Lincoln LS and Cadillac XLR gain loads of neg camber upon compression, so their tires can better maintain contact patch with substantial body roll. These two vehicles have dynamic camber gain which is much better than having to dial in negative static camber. Static negative camber only works for track....such a setting eats inner tread on the street. In fact, the dynamic camber gain in the Cadillac chassis actually overcompensates to allow for tire rollover distortion. BMW has done amazing things with a suspension that has the upper control arm missing. IMO, the competition is slowly encroaching.
Last edited by Lscman; 15th January 2004 at 21:09.
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