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03-30-2021, 12:39 PM | #1 |
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Z4M suspension options that are NOT KW V3
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What is the best suspension setup to run for street and occasional track that's also economical? I'm in an area with a lot of potholes so reliability is important. KWV3 is reputed to be the best on this forum but at $3K I wonder if there are any other good options? I thought the stock setup was a bit soft, especially how it dived and pitched under braking and acceleration. Maybe my stock shocks were a bit worn. Should I give it another try? (Except with Bilstein replacement since stock struts are twice the price) I saw one thread here of someone's bilstein pss10 exploding after a pothole so I'm not considering that as a viable option. I'm currently running fortune auto coilovers but they crash too harshly on big potholes. possible because I'm moderately lowered, but more likely a design flaw with the coilover, i.e. not enough suspension travel, or terrible hockey puck style bump stop (the two are related), or due to the lack of rubber shock mount. Should I just bite the bullet for KW and not look back? |
03-30-2021, 06:59 PM | #2 |
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You can go the custom route, but to be honest, it seems KW is the “best” out of the box. I am finally happy with my setup, but is a mix and match of parts of different makes, all high quality, but required a bit of effort, time and money.
An alternative route is PSS10 and linear springs All that said, you can achieve a good setup without spending 3k I would start with Front Bilstein B6 with OE springs and modified bump stops Rear Bilstein B6 with 500# TCK Line springs Maintain the OE rear ride height This will give you a good starting point, if you want more body control change the front sway. Our cars already have CSL rear sway. If you can afford, get the front M3 CSL sway, otherwise H&R is good. Last edited by maupineda; 03-30-2021 at 07:24 PM.. |
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03-30-2021, 07:38 PM | #3 |
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I know mine isn't an M but just a z4c 3.0si with the "M" sport suspension. I just changed mine over to B4s. I wanted a more comfortable ride but I also AutoX about 2 times a month with 2 drivers so it sees quite a bit of use. Love the shocks, rides much better but still handles great. Kept the OEM springs but did upgrade the mounts, ball joints and control arm bushings. Also added rear reinforcement plates in the rear. I drive the car about 14k miles a year and it isn't a daily so many long drives was killing my back before, not any longer after the switch.
I would just go the B6 route. Hope this helps. |
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03-31-2021, 07:30 AM | #4 |
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Just a reminder, KW V3 is still a very street friendly setup, in that don't expect it to be the best on the track either if you are aiming for every last second (ask me how I know even if its not on the Z4), and the design itself also lead itself to be a limiting factor if you ever go wide wheels on the Z4M (ask me how I know as well).
Also, all coilovers can fail, one of my KW Clubsport failed after barely 5k km, for some mysterious reason that KW can't figure out either, all I heard from KW is 'I have no gas pressure, main seal is bad, and leaking oil', which really isn't making me feel comfortable about the other 3. Marginally less pricey you can go after TCK's single adjustable which you can choose your spring rates to match your car's use. Koni shocks also seems to be easier to find a rebuilder for. A track friend-enemy of mine loved his BC racing setup on his S2K until he finally switched, probably the best of the 'across the pacific' coilover setups off the shelf, he put in some 4 years of very hard miles on them never a single problem.
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03-31-2021, 09:17 AM | #5 |
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Suspension is a HUGE compromise when you talk about a double duty car. Anything good on the street won't be as good on track and vice versa. Finding your happy place on the street - track spectrum will be difficult and expensive if you do not know others running other suspensions you are interested in.
When I was suspension hunting, I was able to experience KWs and TC Kline's. For me, I liked KWs for the street, but they have more body roll on track. TC Kline's were the inverse. Super stiff on roads but felt awesome on track. In addition, both aren't the most budget friendly. Ultimately I went with FA 500s, because I wanted to learn more about suspension set up before having multiple adjustment/variable points and it was one of the best SA kits available that was reasonable price wise (looking at you JRZ). Plus, the cheaper rebuild cost and ability to upgrade later is attractive. I have had FAs for almost 3 years now, and think I have ironed out the bugs I experienced. I started with the upgraded bearings in front and went with swift springs (9k and 11k) and had two issues after install. First, I was bottoming out in the front causing tire rub. Turned out I was running too low and a simple ride height adjustment fixed that. The second issue I experienced was some of the "crashing" in the rear when driving over a sharp bump. Ride height changes didn't fully fix this for me, so I concluded that it was a combination of the linear rear spring design and not enough rear spring length. After some deep dives on the interwebs I found a potential solution on an E36 forum, which is running TC Kline rear "beehive" progressive springs (600lb in my case) and height adjusters instead. This design allows for gradual compression and more spring travel, and has completely eliminated the rear end crashing for me while street driving without much impact for track use. While it took some dialing in, I have been pretty happy with it afterwards for a dual duty car. Next year I fall in the rebuild window, and will be looking at upgrading to the 510 spec and putting better camber plates on. Just for further frame of reference, the other cars in the stable include both a 2017 M2 and 2017 MINI John Cooper Works, both with non-EDC stock suspension. I would say out of the three, the JCW is the most firm on the road and the M2 is the most comfortable, with the Z4M falling in the middle of the two. Hope this helps!
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03-31-2021, 09:27 AM | #6 | |
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What does the "modified bump stops" mean? Assuming cutting them down some and this only comes into play when you bottom the suspension to the point they are hit? How do the 500# TCK Line Springs compare to OEM? Assuming they are stiffer, what is the up and downside to this?
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03-31-2021, 07:38 PM | #7 | |
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03-31-2021, 09:08 PM | #8 |
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Is that something you found out from personal experience?
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04-01-2021, 09:04 AM | #9 |
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Yes, and from measuring actual suspension travel and all that jazz. the moment you lower the car, the moment you compromise a car with already little travel, out of the box, there are only 40mm of suspension travel before hitting the bump stops. lower the car, and you need to deduct from it and adjust bump size accordingly or you just ride on them more often, however, is not that easy, as the bump stop stiffness works in combination with else all. cutting them is a half way job but there are not bump stops options you can chose from anyway, so it is as good as it gets. In general, it is best to keep the ratios the same for bump and droop travel, that is why the moment this car goes lower, the ride goes down the shit pipe.
My car as stands has more suspension travel than stock, a bit stiffer spring rates (about 10% only) and "uprated" damping (H&R struts with B8 Non-M rears), and it rides well and absorbs bumps well, if fact, the faster the better and more compliant it gets as the B6/B8 shocks are digressive and become more compliant with speed, but is not Cadillac compliant ride, is still stiff and will always be. I also have a 7mm higher ride height at the front and my coils are maxed, so I can not go any lower than that, which is fine by me, the car looks ok and I prefer proper suspension travel and geo over a slamed look. The option I gave you above would keep ride height stock, but with the B6 you must cut the bump stop or you ride on them 85% of the time as there will be only 10mm of travel before engaging them since they are 30mm taller than the OE items. I used to have no brand name coils (SCALE), then H&R, then H&R with softer springs (swift + TCK Line), and the ride improved significantly when moving to those springs for a harmonized frequency (1.7Hz front, 1.9Hz rear), but even then the ride was too busy, so is not only the springs but most importantly the shocks. The rear B8's made the most improvement of all the things I did. B6/B8 items are good, but tend to be overdamped with too much rebound, but so is the issue with most (if not all) aftermarket socks. For the rear just choose B6 from the non-M as that would be a bit less stiff, and for the front, there is no option because the Z4M strut body is unique and you need B6 specific. I made the mistake to order B8's from the Non-M and they were too short and I had to cut the rear bump stop to compensate, but if you choose the B6 then no need to faf with anything as long as you keep the rear height as OE. if you hop into the NAM3 forum, you can find all my posts there on the suspension work I did on my Z4M, and my car is finally where I wanted it to be, in a few years time, I will get rid of the H&R coil strut and use a B6 strut as they are digressive and the H&Rs are not, but I will need to adapt the strut bodies to accept coil over perches and keep my swift springs. my setup is: H&R coil over struts with 250# fronts and OE top hats TCK Lines 600# rears with Non-M B8 Bilstein shocks with the H&R height adjusters I also added the monoball RTAB bushings and the car is rock solid going down the road with the suspension doing its work, no more wiggling of the rear when going over crests and bumps and no added NVH Is my setup perfect? no it is not, shocks still have too much rebound, which jack the car down when the road gets too bumpy, and the ride is still a bit busy, the only way out of it is custom dampers, which are way too expensive. you need to budget at least 3.5K for that, but you would get what you want. you just need to know exactly what you want LOL Suspension tuning is, and will always be, A COMPROMISE. Last edited by maupineda; 04-15-2021 at 12:55 PM.. |
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04-01-2021, 08:12 PM | #10 |
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I’m on GC school kit with really low spring rates (375/450), and find it to be very comfortable for everyday driving.
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04-15-2021, 11:37 AM | #11 |
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3002 tii are you lowered? or stock-ish ride height. I'm thinking of just raising my ride height as a cheap test to see if that improves anything.
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04-15-2021, 12:53 PM | #12 |
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08-10-2021, 10:28 AM | #13 |
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I'm running the BC Racing option on my '04 e85 3.0i. I opted for the recommended spring rates from BC (forget values offhand) and upgraded to swift springs.
I got my example with the factory suspension intact but completely worn out. I replaced the front control arms with the OEM+ option from Meyle and the Polyformance upgraded FCABs. I also added the reinforcement plates for the strut towers during installation of the coilovers (front and rear) and upgraded the strut tower brace to a solid triangle option (front only). Also replaced the tie rods (inner/outer) and swapped my rear trail arms were with an adjustable monoball option. Ride height is approx 1/2" below the factory "M" level. Handling was markedly improved relative to how I received the car. My example had the "M" suspension and was slightly lower and stiffer from the factory. I suspect my revised suspension is not far off from the factory ride quality so many miles ago. I had it set fairly stiff initially and have since backed it off somewhat to improve cruising comfort (its not a track car). Overall I'm pretty pleased with it minus a lack of travel in the rear. It's usually a non-issue but railroad tracks or other significant bumps on both sides makes the back end "hop" more than I would like. Contact stays pretty consistent, but its unsettling in the seat as a passenger. I know the KW's are the gold standard according to the forums but I wanted to try something different. Time will tell if I've been foolish or this was an acceptable option for a car that will likely never see a track. I haven't driven a car with the KWs but I suspect mine is a bit more harsh. Overall NVH is still perfectly acceptable for a convertible. The wind noise and creaky interior are still the dominant noises in the cabin. |
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08-15-2021, 04:57 AM | #14 |
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KW best out of the box? Who came up with that? Gold standard?? Lolol they are not..
KW are okay(ish) at best for the price you pay. They are by far not the best out of the box, but then for more upmarket suspension parts, your paying more. As said above, it's all a trade off. For those willing to endeavour further, take a look at Penske or Intrax.
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08-15-2021, 08:41 AM | #15 | |
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Those would be more comparable to Penske/Intrax/AST/Moton/ohlins https://www.kwsuspensions.net/racing/competition_5a/ OF course very very expensive, but what isn't that is race related KW is of course a brand that is very pro-active in motorsports.
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08-15-2021, 05:52 PM | #16 |
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So true, I looked at a set (2 front struts) used from kw racing.a few months back Just the 2 fronts were over 8k pounds used.. so yeah they make some great stuff too. I am getting Intrax to custom build my front struts as the car sits way to low for off the shelf stuff.
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12-08-2021, 12:14 AM | #17 | |
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12-08-2021, 06:00 AM | #18 |
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^^^ yes, the frequency will be way off for what a balanced setup should be. The rear ideally should be quicker to settle after hitting a bump and because where the spring is relative to the damper, it needs to be about 80% more than the front to be a tad stiffer so the damper is settled in sync with the front axle.
That is why the OE setup is ~220 and rears ~440, though the rears are progressive, but in the 2in of bump travel that matter, that is around the number. To make it stiffer (don’t know why one want that) and to keep the same balance you see where the rear would need to be. I went from similar rates that came with the H&R coils to 225 and 600 and the car is very balance, still too stiff for my liking but very poised and balanced and you do feel how both axles go in harmony. Though my stiffness is now due to the shock valving which I cannot do much about unless I have custom job done, but it is fine as is and much better than what I had before I tried 500/500 350/500 (estimated for the H&R based on e46 setups) 250/600 (liner Swift and TCK springs) If I chose again, it would be 225/500 Last edited by maupineda; 12-08-2021 at 06:10 AM.. |
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12-08-2021, 07:00 AM | #19 |
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I admittedly don't know a lot about suspension but I'm looking for something better than stock but still not too harsh, is that possible?
What do you guys think about the H&R setup that Turnermotorsport sells? https://www.turnermotorsport.com/p-1...er-suspension/
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12-08-2021, 03:03 PM | #20 |
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Maupineda, did you get those OE numbers yourself or from a forum post on here? the fronts are progressive too.
The fact is a lot of forum members, tckline, ground control, have had success with stiffer fronts, despite the flat ride theory specifying that rear should be stiffer by X percent. So there's not really a known right or wrong here. shocks are also a factor as stiffer shocks force the vehicle to settle quickly making the flat ride thing of less critical importance. grannyknot unfortunately there's no absolute right answer here, everyone has their own opinion, however H&R (and most aftermarket performance options) will be stiffer than stock from what I've read on zpost. whether it's "too harsh" is subjective. |
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12-08-2021, 04:41 PM | #21 | |
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I’ve run few different combos myself between my AST and TCKs on my previous 3.0si and now the above on the M, and 375/450 is very comfortable for everyday. I don’t have any issues with settling over low speed bumps. If anything I found tire choice and size had more of an impact on how the car behaves over uneven roads (for my current setup). I noticed this when switching to my winter tires. |
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12-08-2021, 05:42 PM | #22 | |
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Not to turn this into a spring rate thread but I'm running very similar F400/R500 linear springs and they are perfect for my needs. Even this is way more on the conservative side to what is normally used. As we both know there is so much more to do with ride quality than the spring rate. I have found that Bushings, Damper Mounts and Camber Plates all come in either Rubber, Poly or Spherical. This can translate to a significantly softer or harder feel than considering only the spring rate alone.
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