[ajsalida]

Originally Posted by justpete

True enough. Developing the skills to be able to understand what's going on with the car on the track is best done with a car that does not drive like a track car, imho.

Just trying to help clarify a few things, not trying to be negative.

Good comments. On the rear subframe mounts, they are particularly soft on the e9x non-M3, and that becomes very apparent once other things are made stiffer/firmer. The entire rear subframe walks around under power and over mid corner bumps/washboard. That is my direct experience and stiffening them up eliminated that, rear is much more planted and predictable.

About the LSD, of course having a true LSD is better than not in just about every situation. However bad it is these cars still have a type of LSD the e-LSD so it is not a true open diff as some seem to suggest. My objection to the LSD crowd is they jump in at every instance and say you MUST have an LSD before putting a rear bar on. Well I don't agree mainly from a cost benefits point of view. You can do shocks springs bars and subframe bushings (plus a few other things) all together for less than an LSD.

If you have the money and if you have the skills and if you have the WHP to make a true LSD vs e-diff something that is reasonable/important, sure, go for it. Glaring shameful omission from the factory on our cars IMHO, does not mean I'd feel compelled to go out and drop 2500 or whatever on one.

The rear bar issue is overblown here by some. I certainly think folks should reconsider putting ONLY a rear bar on. Similar stiffness front and rear bars though, esp off a similar/identical chassis like the M3 are fine. Of course you have to balance it with the springs esp in rear. Somebody with H&R race may wish to rethink, same with 700 lb/in coilovers. Rear M3 springs are 520 or so lb/in IIRC using same bar so there is a ways to go before you're getting beyond those specs on Eibachs or V1's.

But my car, for example, XI springs are stiffer than OEM non-XI sport. Eibachs are about as stiff as OEM sport. Rear bar is fine and in fact very enjoyable with front bar. I first put the rear bar on without a front bar, that was fun for about a day or so.

Oh, also have Koni SA's. I would completely rethink all of this if I went with TCK DA koni based coil overs or something in that range, AND went full FBO or ST, and had a MT instead of AT, and this car was intended to be a track weapon instead of a GT type cruiser that it is. No stranger to race tracks myself, but I do know when to quit modifying my main street car to be more like a track car. Which has not always been the case, learned the hard way.

edit: I think a different way to say all this is the following, suppose you had up 2500 to spend on making your street car daily driver handle better. What would you do first? Well I would (intelligently) upgrade shocks springs F&R bars bushings. Pull out the pins in front. Get a good alignment. Nail all that stuff down and debug it all out the ass then worry about camber arms and toe links, LSD etc. as time money and knowledge/skill accumulate.

[justpete]

Originally Posted by ajsalida

Good comments. On the rear subframe mounts, they are particularly soft on the e9x non-M3, and that becomes very apparent once other things are made stiffer/firmer. The entire rear subframe walks around under power and over mid corner bumps/washboard. That is my direct experience and stiffening them up eliminated that, rear is much more planted and predictable.

Absolutely, they are surprisingly soft and this is very apparent under power. This is also my direct experience however it has also been my experience that this was excellent feedback about my ability to manage smooth transitions, turn-in, braking, etc. Certainly it isn't something improved driving alone will eliminate but instead is something that provides a means of minimizing its effect. And then it comes time to eliminate it with solid bushings.

Originally Posted by ajsalida

About the LSD, of course having a true LSD is better than not in just about every situation. However bad it is these cars still have a type of LSD the e-LSD so it is not a true open diff as some seem to suggest. My objection to the LSD crowd is they jump in at every instance and say you MUST have an LSD before putting a rear bar on. Well I don't agree mainly from a cost benefits point of view. You can do shocks springs bars and subframe bushings (plus a few other things) all together for less than an LSD.

If you have the money and if you have the skills and if you have the WHP to make a true LSD vs e-diff something that is reasonable/important, sure, go for it. Glaring shameful omission from the factory on our cars IMHO, does not mean I'd feel compelled to go out and drop 2500 or whatever on one.

An e-diff will burn up rear brakes, ask me how I know.

I think the LSD-before-rear-bar reaction comes up because increasing rear roll stiffness is often done without regard to what it really does. And in doing so tricycling becomes more likely and thus an LSD becomes critical to managing to keep torque steering to the road. However, the stiffer bar is responsible for taking traction away from the driven wheels so the solution isn't an LSD it's a less stiff roll bar.

Best leave the rear bar stock or even disconnect it altogether so the rear tires are always providing drive traction. An LSD then gets to be an LSD instead of a rear bar effect cancellation device.

Agreed that leaving out a Salisbury-type LSD is a shameful omission, the e-diff is a pale imitation at best imho. I know from experience taking corners became an entirely different sensation with the LSD installed and clearly faster although this predated the installation of a logging system so I can't back that up with measurements, it's just my sense of it fwiw.

Originally Posted by ajsalida

The rear bar issue is overblown here by some. I certainly think folks should reconsider putting ONLY a rear bar on. Similar stiffness front and rear bars though, esp off a similar/identical chassis like the M3 are fine. Of course you have to balance it with the springs esp in rear. Somebody with H&R race may wish to rethink, same with 700 lb/in coilovers. Rear M3 springs are 520 or so lb/in IIRC using same bar so there is a ways to go before you're getting beyond those specs on Eibachs or V1's.

Well the M3 is a heavier car and its rear springs can be only so stiff and offer the typical road-going BMW consumer a sellable ride so its bar is stiffer than other models. That doesn't make it better. Getting the ride height right and keeping the roll center from getting too far away from the cg height will minimize roll under weight transfer. This obviates requiring an overly stiff rear ARB to otherwise manage the problem which is necessary to running without a rear bar or at least a very weak one to optimize road contact for the driven wheels.

Originally Posted by ajsalida

But my car, for example, XI springs are stiffer than OEM non-XI sport. Eibachs are about as stiff as OEM sport. Rear bar is fine and in fact very enjoyable with front bar. I first put the rear bar on without a front bar, that was fun for about a day or so.

Oh, also have Koni SA's. I would completely rethink all of this if I went with TCK DA koni based coil overs or something in that range, AND went full FBO or ST, and had a MT instead of AT, and this car was intended to be a track weapon instead of a GT type cruiser that it is. No stranger to race tracks myself, but I do know when to quit modifying my main street car to be more like a track car. Which has not always been the case, learned the hard way.

Chassis setup is crazy complicated, just take a look through the user manual for the chassis part of lapsim software by Bosch-Motorsport. FWIW I went the full track car route while requiring it be merely street legal. I have street wheels and tires that have the same rolling radius but more clearance than the track wheels and tires. They also have sidewalls that are less stiff and make it streetable afaic but then I literally couldn't care less about ride quality but chuckhole protection is kinda important around here.

The track wheels and tires are very nearly flush in front without enough room to put a finger between the tread and the wheel arch. Jumping up and down while hanging on to the open passenger door does not cause the tire/fender clearance to visibly change, only the very stiff tire sidewall flexes. That's a stiff suspension. Hit a chuckhole at street speeds and it ain't going anywhere without a flatbed...

I knew this going in but elected going with a full race suspension for track use. I'm not convinced it's possible to make a full race suspension that can be streetable when the car is set up with a low front ride height and wide as possible track. There just isn't the physical clearance to allow less aggressive valving to do anything useful.

Originally Posted by ajsalida

edit: I think a different way to say all this is the following, suppose you had up 2500 to spend on making your street car daily driver handle better. What would you do first? Well I would (intelligently) upgrade shocks springs F&R bars bushings. Pull out the pins in front. Get a good alignment. Nail all that stuff down and debug it all out the ass then worry about camber arms and toe links, LSD etc. as time money and knowledge/skill accumulate.

This is the big question alright. The key though is defining what handling better actually means. Since we generally don't take corners on the street at track speeds extra camber really isn't necessary, looks cool though but that's about it. Camber plates will help tighten up steering response _and_ let you change the front alignment at the track for the track.

Proper alignment would be for the street, with zero toe if running M3 front control arms, and carefully marked on the plate but then also aligned for the track with max camber and the correct amount of toe out, also carefully marked on the plate. Then all you have to do is move the arrow between the marks. This alone makes a huge difference both on the street and the track for not much money.

If running a stock suspension the problem becomes finding a properly engineered solution which is why I personally went with the Performance Suspension with the odometer at 897mi. Reasonably good design, did what I wanted, and got me where I wanted to be. Improved handling on the street without being twitchy and worked very well with the camber plate upgrade. A bit over $2500 but not if buying used or doing some of the work yourself. Best bang for the buck imho.

Pretty tough to really upgrade the suspension without spending a ludicrous amount of money. The cost just keeps going up with the hp too. And it becomes increasingly difficult to keep the car streetable for most once it's all spherical bearings and rigid arms and ball ends, etc. A race car ain't comfortable. And a comfortable car ain't a race car. Again, it's just my opinion and worth exactly diddley 'cuz it's driven by my biases toward full track performance. I mean what kind of loon puts a full fire suppression system in a street car?!

[ajsalida]

Pete, this is actually a great discussion instead of the pissing contest it maybe was devolving into. Let me make one more attempt to justify my position WRT the LSD and rear bar. All of your comments are correct in situations at or near traction limits in corners. Thing is I don't go there on the street, not in this car for sure, and nether do many/most folks here on this board.

I like the feel of the rear bar in sub 99% situations, it has a crisper turn in feel that the car was completely lacking before. I can feel the weight diagonally transfer across the car under braking and going into a corner, feel the outside front plant, the rear want to just very slightly rotate around it, and then the car stay neutral under power coming through and out. This is AWD remember, it plowed like a tractor before. This level of feel and responsiveness was totally missing from the stock car, or even after Koni/Eibachs.

So up to say 90% of the limit in this car, for me, I like it. I spend little/no time at the limit on the street, except in ice and snow and then not intentionally. People who play autocross or road racer on the street are retards IMHO, if you spend a great deal of time on a track you know that too. No way to know traction or other hazard conditions with enough confidence to exploit the limit capabilities of modern cars sanely, esp where I live (mountains).

Now would an LSD enhance all this? I'm sure it would and maybe someday I'll get one. For now for me the rear bar works well with the rest of the mods and provides a more nimble responsive feel.

The extra 1/2 degree of neg camber in front is another example. It adds to quickness of steering feel (with 0 front toe alignment), but total is only 1.4 deg neg that is with the eibach's drop (XI remember so even slower steering rack than non XI). Cheap reversible mod in lieu of other more expensive approaches that changes feel substantially without going overboard like camber plates might be for a street car. Is it the best choice for limit performance on the track? No way, but again I am not interested in that for this car.

This car is a year round AWD car in the high mountains of Colorado, 8k ft ASL. I want it to be fun and comfortable all year long, and it is. I wanted much crisper responsive handling than stock (which was horrible frankly) without being harsh or brutal track-like rattle can for those few extra tenths (or hundredths) a lap. Seems to have hit that target more or less, and for not too much coin.

[justpete]

Originally Posted by ajsalida

Pete, this is actually a great discussion instead of the pissing contest it maybe was devolving into. Let me make one more attempt to justify my position WRT the LSD and rear bar. All of your comments are correct in situations at or near traction limits in corners. Thing is I don't go there on the street, not in this car for sure, and nether do many/most folks here on this board.

No intention on my part to minimize your justification, my bad. It's that bias thing again. There's the track and everything else involved in getting there and back. Ha. Kinda blinds me ya know?

Yeah, going to the limit on the street is seriously not a good thing. Sadly some find out the hard way. Have had nearly two dozen motorcycle and car accidents over the years and thankfully the only injuries were to me and my pride, and checkbook come to think of it. Stupid is as stupid does I guess. Starting to run tracks put it all in stark relief for me, shame it took so dang long...

Originally Posted by ajsalida

I like the feel of the rear bar in sub 99% situations, it has a crisper turn in feel that the car was completely lacking before. I can feel the weight diagonally transfer across the car under braking and going into a corner, feel the outside front plant, the rear want to just very slightly rotate around it, and then the car stay neutral under power coming through and out. This is AWD remember, it plowed like a tractor before. This level of feel and responsiveness was totally missing from the stock car, or even after Koni/Eibachs.

Very cool -- first time I've heard anyone describe correctly what's going on and why it matters under what conditions, thanks very much for that! This is exactly what to expect with an overly stiff rear bar. But you're using it to provide more weight transfer to the outside front tire for crisper turn-in, unloading the rear wheels more than usual allowing some marginal rotation, and then smacking the rear wheels into the road on acceleration to help power out of the turn. Excellent!

I swear I never thought about this limited use of a heavier rear ARB on the street, makes perfect sense now that you described it. And it's interesting to note that the suspension change didn't help with steering quickness, etc. It shouldn't by itself. Just adjusting tire pressures can have more impact on steering.

Originally Posted by ajsalida

So up to say 90% of the limit in this car, for me, I like it. I spend little/no time at the limit on the street, except in ice and snow and then not intentionally. People who play autocross or road racer on the street are retards IMHO, if you spend a great deal of time on a track you know that too. No way to know traction or other hazard conditions with enough confidence to exploit the limit capabilities of modern cars sanely, esp where I live (mountains).

I do tend to 'practice' turns on the street but not at the limit. Agreed that unknown conditions on the street don't come with corner workers, only with 911. That goes double for being in the mountains fersure.

Originally Posted by ajsalida

Now would an LSD enhance all this? I'm sure it would and maybe someday I'll get one. For now for me the rear bar works well with the rest of the mods and provides a more nimble responsive feel.

It really wouldn't except near the limit. A good one is four to five grand and you do get what you pay for in this instance, imho, money is best spent elsewhere. If you've got the nimbleness that works for you then there's nothing to fix so there's nothing to upgrade, right? Upgrade fever strikes everybody, btdt, but honestly we all end up spending long green without real justification. Not that it's not fun, don't get me wrong, it is, btdt too. Wouldn't ever want to be accused of keeping anyone from having fun.

Originally Posted by ajsalida

The extra 1/2 degree of neg camber in front is another example. It adds to quickness of steering feel (with 0 front toe alignment), but total is only 1.4 deg neg that is with the eibach's drop (XI remember so even slower steering rack than non XI). Cheap reversible mod in lieu of other more expensive approaches that changes feel substantially without going overboard like camber plates might be for a street car. Is it the best choice for limit performance on the track? No way, but again I am not interested in that for this car.

OK, sure, a small amount of camber probably helps with the extra weight transfer trying to push the outside front tire over so it would contribute to more predictable steering, makes sense. I forgot the steering ratio is lower with xi, thanks, makes even more sense now.

Camber plates get rid of the elastomers in the upper strut mounts and replace them with a spherical bearing. Now the steering has no real play at its hinge point nor is there any windup which makes the steering quicker and more precise. Being able to set caster and camber yourself actually turns out to be a secondary benefit. I really didn't understand the recommendation as being preferred to M3 control arms and all the stuff I wanted to do. Now that I look back on this process I'm glad they wouldn't take my money. Was beginning to think my name was Phillip J Fry...

You're absolutely right of course that camber plates would be a wasted expense for a street car that won't see the track. Lots better way to spend a grand, installed, plus the cost of two alignments one of which would never be used.

Originally Posted by ajsalida

This car is a year round AWD car in the high mountains of Colorado, 8k ft ASL. I want it to be fun and comfortable all year long, and it is. I wanted much crisper responsive handling than stock (which was horrible frankly) without being harsh or brutal track-like rattle can for those few extra tenths (or hundredths) a lap. Seems to have hit that target more or less, and for not too much coin.

Couldn't agree more, thanks again for explaining, you clearly understand the chassis dynamics. Beats spending a bunch of money shotgunning the handling in the hopes that something good would come of it.

Weirdly it took me a couple of years to convince the shop I still thought the car was a quiet, caddilac-riding mall chariot. Got the suspension, intake, exhaust, ssk, camber plates, wheels and Pirellis, and strut brace in the first year or so and then the diff and CDV delete at the end of last summer. It took a couple of months after the diff was installed until they believed me I guess. Point is everyone's threshold is different and I keep forgetting that.

[Raptor04]

Thanks for the feedback and conversion, which is where I was trying to go from the beginning...

[Raptor04]

Ajsalida, can you tell me what you would rethink if you had TC Kline DAs on your car, which is what I have on the rear of my car?

[ajsalida]

Originally Posted by Raptor001

Ajsalida, can you tell me what you would rethink if you had TC Kline DAs on your car, which is what I have on the rear of my car?

What are you running in front if you only have TCK DA rear? TCK SA? If you do not have something similar to that in front that is what I would do first.

Looks like you have an XI as well. Basically the process is to stiffen everything up to the next level for higher loads and more responsiveness at the expense of comfort and isolation. Where I would begin to rethink is here: This is where you go with camber plates in front and then sort out spring rates and sway bars and more aggressive alignments.

Full rear subframe (not the inserts) & diff bushings and the rest of the rear M3 bits. Stiffer (not solid) motor and tranny mounts. You have no M3 bits that will transfer over in front but I believe someone makes press-in control arm bushings.

You are mainly systematically removing softer more compliant rubber parts of the car that take up suspension loads, and replacing them with stiffer more precise elements that do not deflect or deform as much under higher loads. I would not ever go solid in a street car, prefer delrin over poly where possible.

The "line" here for me is camber plates. Most have a big spherical bearing and eliminate the rubber in the upper strut mount. This is great for super sharp steering and adjustment, but drive a car with them through a colorado winter and you may wish you hadn't done it. But once you go camber plates, might as well bring everything else up to the task.

The thing is, you make something super stiff (say camber plates) the next thing in the chain becomes the soft part and it flexes. So you have to take a systemic approach, and things need to be at comparable levels of stiffness.

Eventually you weld in a full roll cage because the unibody is too soft, and drive around in a car to buy beer with completely gutted interior and no passenger seat. Then the softest thing in the car is your head and you'll bounce it off a roll bar tube if you stop too fast so better wear a helmet...then there's tire brakes etc.

So this brings up a CAUTION. The most important thing to upgrade first in a car is the driver. To that end I would never recommend anyone go over that camber plate line, preferably far before that, without getting a lot of track time in the car they are modding. Drivers schools, HPDE, autocross, whatever. You need to develop the skills and intuition to understand, exploit, and carefully approach the limits of the stuff you are changing in the car. Modding is an iterative process.

If you ski or snowboard, modding your car's suspension all at once is like you are going from big fat puffy soft tourist rental skis to race skis. You can get over your head in milliseconds. You have the skills fine, you don't, hello orthopedic ward or worse. Ideally you are far faster than the car, and have already developed some knowledge & skill to empirically assess what is going on with each new level of mod.

Good luck, hope this helps.

[ajsalida]

This may be a good place to bring up something I find useful in many areas, which is the idea of the four levels of mastery. It is kind of hokey but it applies to a lot of areas of life.

Level 1: Unconscious incompetence: you don't even know you don't know.

Level 2: Conscious incompetence: you know you don't know

Level 3: Conscious competence: you know you know (and that is actually correct)

Level 4: Unconscious competence: you do the right thing without even thinking about it, superior skill is now instinct.

Most of humanity spends their entire life in all areas at Level 1. One should feel fortunate to reach level 2 in any activity, that is the beginning of knowledge. Aspire for level 3 in something, anything. Level 4 is out of your hands, god's will if you prefer.

[DrRobert]

Originally Posted by justpete

I think the LSD-before-rear-bar reaction comes up because increasing rear roll stiffness is often done without regard to what it really does. And in doing so tricycling becomes more likely and thus an LSD becomes critical to managing to keep torque steering to the road. However, the stiffer bar is responsible for taking traction away from the driven wheels so the solution isn't an LSD it's a less stiff roll bar.

Best leave the rear bar stock or even disconnect it altogether so the rear tires are always providing drive traction. An LSD then gets to be an LSD instead of a rear bar effect cancellation device.

Hi,

Not trying to hijack this thread, but I was just emailing with Harold at HP Autosport (Quaife LSD distributor) about this topic a few days ago, and thought his comment to me about this was interesting and relevant to your discussion. Here is what he said:

"I don't recommend a rear bar as it takes away traction in a turn that you just added with the LSD. The car will feel flatter in a turn, but actually has less traction."

FWIW, he did recommend the M3 front control arms, front anti roll bar, and subframe bushings to go with the LSD.

Robert