e46 M3 suspension setup, or how to not downgrade your car with suspension mods

[bigjae46]

The JRZs are a high performance damper with a relatively short service life.

I have TC Kline doubles. I think these are the best balance between performance and daily drivability. TC Kline does extensive testing so it makes setup relatively easy. On track I'm pretty damned close to MCS equipped cars on Hoosiers and slicks - maybe 1-2 seconds off. My limitation is spring rates, I need more spring rate to run tires stickier than an NT01 or RR. I am at the limit on the rear shocks.

The TCKs even with 600 fr/700rr springs are surprisingly comfortable on the street.

TCKs get my votes unless you are running a racing slick or Hoosier.

[cobra]

The JRZs are a high performance damper with a relatively short service life.

...

I don't understand this statement. What about them makes their service life shorter?

[bigjae46]

I don't understand this statement. What about them makes their service life shorter?

Typical rebuild interval that I've seen is 10k-20k miles or 4-6 years. I'm not a damper expert to tell you why that is. I'm assuming higher pressures = higher wear? MCS and Moton aren't that different from JRZ for service intervals.

[WestBankM4]

Why doesn't anyone use AST suspension on the E46 M3 chassis? I ran AST 5100's on my '95 M3 in the past and they were absolutely quality, looks like they're paired up with Moton now?

I personally went with ST XTA's (same as KW2's minus the shock body coating) for my E46 M3 build and thus far, I gotta say I'm pleasantly surprised. Ideally I'd like to get everything dialed in after finishing up some other work on the car.

[IamFODI]

I remember reading somewhere that, in damper piston seals, there's typically a tradeoff between longevity and friction. You can make one that lasts a long time, or one that has low friction, but it's very hard to have both. Can't help but feel like that explains the difference between, say, a stock-replacement Bilstein damper (somewhat stiff ride relative to spring rates, lasts forever) and something like a Moton (moves like butter, needs constant rebuilds).

If this is true, it might help explain JRZ's short rebuild intervals.

It also makes me feel like Öhlins is doing something magic. IDK how else mine could have lasted this long, given the punishment they've seen...

[bigjae46]

Why doesn't anyone use AST suspension on the E46 M3 chassis? I ran AST 5100's on my '95 M3 in the past and they were absolutely quality, looks like they're paired up with Moton now?

Vorshlag was the only BMW tuner that I could think of that was selling ASTs for BMWs. I think Vorshlag has not kept up with the newer cars so they kind of fell off the map.

I've learned its less about the actual damper and more about the vendor taking the time to setup and test the dampers for their intended use. There is value in knowledge.

Bimmerworld & MCS is a good example. You can buy MCS dampers, call Bimmerworld who has ran the damper on the track and be pretty much setup correctly out the box. You can get a JRZ damper which is probably just as good...maybe better...but you're going to spend more time and money getting the suspension dialed in unless there is a BMW tuner that supports JRZ that I don't know about.

Which is the same reason why I use and recommend TC Kline. In 2014, I saw TC at Road America in a new F82 M4 with his coilovers installed doing track and street testing. I used TC's recommendations for springs and damper adjustments. Made 1 adjustment to the dampers and didn't make another change until I removed 500 lbs and installed a rollcage. I swapped my TCKs from the 330 to the M3 back in 2013, he told me a little secret to keep the non-M plates for added negative camber. Works fantastic!

Now...since I've become aware of the flat ride concept I have changed my thinking a little bit especially when it comes to spring rates and compliance. Some advice I have received is not in total agreement with flat ride but it's not far off either.

[CrisSilberGrau]

Why doesn't anyone use AST suspension on the E46 M3 chassis? I ran AST 5100's on my '95 M3 in the past and they were absolutely quality, looks like they're paired up with Moton now?

I personally went with ST XTA's (same as KW2's minus the shock body coating) for my E46 M3 build and thus far, I gotta say I'm pleasantly surprised. Ideally I'd like to get everything dialed in after finishing up some other work on the car.

From the local pool of guys that use AST on either the F87 or the E46 I've only heard good things. All of those accounts are mostly for the 5100s and nothing else.

I'm on TCK DAs, but they have been rebuilt once under me, and are not leaking pretty badly again and im looking at viable options for what my use case is. I've mentioned to some members here that I'd like a more "hardcore"/GTS spec style suspension, something that will see a decent amount of track duty but will still be daily at least 2 or 3 days a week in the summer.

Easiest option:
Buy new TCK DAs and maybe go from 400F/600R to 450/500F - 650/700R

OR
MCS 2way NR coilover rear
AST 5100/5200 coilover rear

I'm teetering between MCS and AST, looking to participate in a time attack competition. If anyone has some info on the above MCS/AST id appreciate it. Car is around 3280lbs without me and a full tank. Will either run 265 or 275 square.

[elbert]

I remember reading somewhere that, in damper piston seals, there's typically a tradeoff between longevity and friction. You can make one that lasts a long time, or one that has low friction, but it's very hard to have both. Can't help but feel like that explains the difference between, say, a stock-replacement Bilstein damper (somewhat stiff ride relative to spring rates, lasts forever) and something like a Moton (moves like butter, needs constant rebuilds).

That's pretty much it -- stiction.

Why doesn't anyone use AST suspension on the E46 M3 chassis? I ran AST 5100's on my '95 M3 in the past and they were absolutely quality, looks like they're paired up with Moton now?

AST acquired Moton a few years ago. One of the founders of JRZ and one of the people from Moton (Lex) then went off to form MCS.

The reason you don't hear about AST anymore is because their most vocal backer (Vorshlag) stopped selling them and switched to MCS. AST had some "teething issues" to put it politely. Not sure how AST is now.

I'm teetering between MCS and AST

I would go with MCS in that case because you will probably get better tech support from your vendor, assuming you buy from someone who knows what they're talking about.

[cobra]

Typical rebuild interval that I've seen is 10k-20k miles or 4-6 years. I'm not a damper expert to tell you why that is. I'm assuming higher pressures = higher wear? MCS and Moton aren't that different from JRZ for service intervals.

I remember reading somewhere that, in damper piston seals, there's typically a tradeoff between longevity and friction. You can make one that lasts a long time, or one that has low friction, but it's very hard to have both. Can't help but feel like that explains the difference between, say, a stock-replacement Bilstein damper (somewhat stiff ride relative to spring rates, lasts forever) and something like a Moton (moves like butter, needs constant rebuilds).

If this is true, it might help explain JRZ's short rebuild intervals.

It also makes me feel like Öhlins is doing something magic. IDK how else mine could have lasted this long, given the punishment they've seen...

This makes sense. Shaft seals generally are on a scale of high friction/high sealing ability to low friction/low sealing ability. The rest of the shock doesn't really follow the same logic so if the shock isn't leaking it's probably fine.

Ohlins is kind of notorious for needing rebuilds, at least in my experience. They use low tension seals in many places for ultra buttery smooth action but they don't last.

Vorshlag was the only BMW tuner that I could think of that was selling ASTs for BMWs. I think Vorshlag has not kept up with the newer cars so they kind of fell off the map.

I've learned its less about the actual damper and more about the vendor taking the time to setup and test the dampers for their intended use. There is value in knowledge.

Bimmerworld & MCS is a good example. You can buy MCS dampers, call Bimmerworld who has ran the damper on the track and be pretty much setup correctly out the box. You can get a JRZ damper which is probably just as good...maybe better...but you're going to spend more time and money getting the suspension dialed in unless there is a BMW tuner that supports JRZ that I don't know about.

Which is the same reason why I use and recommend TC Kline. In 2014, I saw TC at Road America in a new F82 M4 with his coilovers installed doing track and street testing. I used TC's recommendations for springs and damper adjustments. Made 1 adjustment to the dampers and didn't make another change until I removed 500 lbs and installed a rollcage. I swapped my TCKs from the 330 to the M3 back in 2013, he told me a little secret to keep the non-M plates for added negative camber. Works fantastic!

Now...since I've become aware of the flat ride concept I have changed my thinking a little bit especially when it comes to spring rates and compliance. Some advice I have received is not in total agreement with flat ride but it's not far off either.

You have some good points. You can have a really nice shock but if it isn't tuned properly it's going to function worse than a properly set up "budget" shock like a Koni.

I would hope these companies like jrz/moton/ast are putting effort into tuning each vehicle individually but maybe they aren't.

[bigjae46]

I would hope these companies like jrz/moton/ast are putting effort into tuning each vehicle individually but maybe they aren't.

They don't typically tune to specific cars. JRZ provides a damper that physically fits and provides a damper set up to some sort of calculation. It takes a Bimmerworld, Vorshlag, Turner, etc to fit the damper and try out spring rates and damper settings.

KW says they test on each car they sell a suspension for. Not sure I believe it, KWs are so stiff they ride like crap.

[WestBankM4]

Thanks for the replies regarding my question about AST. I remember I was number one or two with their 5100's, so early in fact that they were indeed having "teething issues", specifically portions of my kit that were incorrect after delivery by Vorschlag. They had a specialist from Holland flown in to assess the situation, I thought that was extremely odd at the time.

[STAATS]

They don't typically tune to specific cars. JRZ provides a damper that physically fits and provides a damper set up to some sort of calculation. It takes a Bimmerworld, Vorshlag, Turner, etc to fit the damper and try out spring rates and damper settings.

KW says they test on each car they sell a suspension for. Not sure I believe it, KWs are so stiff they ride like crap.

I agree it's probably a little unrealistic to think they have tested every suspension package option they sell on every car but given their on/off close relationship with BMW Motorsport (BMW Motorsport | KW suspensions) I would be surprised if they didn't put in testing effort into their BMW M kits... This is why I have never understood the hate for KW in the US... they are super common in Europe and BMW clearly backs them, I can't remember what GTS/CS model it is but it is the factory suspension for one of their M3/4 fitouts.

[WestBankM4]

I agree it's probably a little unrealistic to think they have tested every suspension package option they sell on every car but given their on/off close relationship with BMW Motorsport (BMW Motorsport | KW suspensions) I would be surprised if they didn't put in testing effort into their BMW M kits... This is why I have never understood the hate for KW in the US... they are super common in Europe and BMW clearly backs them, I can't remember what GTS/CS model it is but it is the factory suspension for one of their M3/4 fitouts.

It was the M4 GTS fitted with KWCS 3-way from the factory.

Has there been a lot of hate with KW products? I wanted KW's for the E46 but I was told the ST's are KW's, just doesn't have the anti-corrosive coating on the shock body. I naturally went with ST's, otherwise it was going to be KW2's. Can someone confirm that ST XTA's are basically KW2's?

[bigjae46]

I agree it's probably a little unrealistic to think they have tested every suspension package option they sell on every car but given their on/off close relationship with BMW Motorsport (BMW Motorsport | KW suspensions) I would be surprised if they didn't put in testing effort into their BMW M kits... This is why I have never understood the hate for KW in the US... they are super common in Europe and BMW clearly backs them, I can't remember what GTS/CS model it is but it is the factory suspension for one of their M3/4 fitouts.

BMW likely does the testing and tells KW what they want. Europe is one thing where the roads are generally smoother. The bumpy roads in the US require a more compliant suspension.

[r4dr]

I agree it's probably a little unrealistic to think they have tested every suspension package option they sell on every car but given their on/off close relationship with BMW Motorsport (BMW Motorsport | KW suspensions) I would be surprised if they didn't put in testing effort into their BMW M kits... This is why I have never understood the hate for KW in the US... they are super common in Europe and BMW clearly backs them, I can't remember what GTS/CS model it is but it is the factory suspension for one of their M3/4 fitouts.

The KW Motorsports and KW consumer (V1, V2) products seem to be different. KW Motorsports stuff in Europe is the real deal, and a lot of people from Manthey to BMW customer racing run their dampers. Emotion Engineering is the only one I'm aware of in the US that works with KW Motorsports products.