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02-09-2018, 03:49 PM | #23 | |
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02-09-2018, 08:27 PM | #24 |
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Your concerns are completely unfounded thus far. If roll resistance exceeds chassis stiffness then yes you'll have failure points pop up like the subframe welds on older generations. However, that doesn't seem to be a concern on our cars.The spring itself being 1000lb doesn't cause any more "stress" then adding roll resistance with a sway bar does... And if you run the springs so soft that you're riding the bump stops then think about how much stress that puts on the chassis since nothing is damping load... if you were concerned about failure points then I'd look at the upper strut mounts since they have been known to blow through to the trunk.
The rear springs are not 100% effective because they mount closer to the chassis where they get leveraged less. For ever 1" of wheel movement- and you've only got about 4 1/2" to play with as dictated by your strut stroke- the spring only compresses 1/3". Hence why a 1000lb spring is only as effective as a 300lb spring in the rear. I remember from another thread that people are running longer rear springs than I do... at full droop (car in the air) do you have preload on the rear springs to achieve your current ride height? That might be the source of your damping issue... Or, inadequate damping. Take all preload off the rear spring, if present. I keep getting told ycw probably aren't all that great, yet, the spring rates, spring lengths, and damping all appear to be more ideal than everything else people are paying more money for. If I set my rear dampers to max damping the car will completely jack down even with 900lb springs Last edited by bbnks2; 02-09-2018 at 09:08 PM.. |
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02-10-2018, 09:50 AM | #25 | |
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TCK is a great damper. It should be a concern if you're rebounding is maxed out on a TCK damper, because they have quite a bit of rate in there. FWIW - After a rear bar I settled to about mid-setting on my rebound and it was very happy within that range. Maxing out rebound trying to force rotation is a sign that something is up - And I don't agree that forcing more spring is ultimately the solution. OP - Do what you want, but in the end there are people that do calculations on a computer and math and will disagree until theyre blue in the face that say you're wrong....and others that tend to throw away and setup cars based on feel and times. Last edited by Kgolf31; 02-10-2018 at 02:35 PM.. |
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02-12-2018, 05:28 AM | #26 |
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Everytime i read your Posts here in the track area i am just confused.
I wrote my thoughts concerning spring rates etc. last year because i was having crazy Problems with my car... In the end it came out that the PU Bushings were to blame. Still i donīt understand that it seems so Different in what spring rates most of the german guys here run and what spring rates you american guys run: The KW Clubsport e.g. for the 135i AG Model has spring rates of 70N/mm in the front, 80N/mm in the rear (same as my ST XTA). The same Setup for the 1M is 110N/mm in the front and 120N/mm in the rear. Concerning the results from the different Setups you guys drive that should result in massive understeering, because the front axle is way to hard. I had both Setups already in my car (With OEM Roll bars and ST XTA Dampers (similiar to V2)) and both worked really well (besides the Problems going straight because of the PU Shit).... Also the most Setups from race Shops around the nordschleife do not use this 1:2 front to rear measurement for their spring rates... |
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02-12-2018, 07:49 AM | #27 | |
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You're setup with a car running 400 lbs in the front, and 457 lbs in the rear. The rear is crazy soft - like, not even remotely close on wheel rates compared to the front. That setup is like trying to copy cat a E36 spring rate setup - They are COMPLETELY different cars. My car drove fine: |
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02-13-2018, 08:35 AM | #28 | ||||||
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Lots of different points being made within this thread so Ill to stick to debating one thing at a time. First Ill address the side conversation taking place. Then, Ill get back to the OP.Please skip to the the end of this post now for my suggestions to the OP if you don't feel like participating in the side conversation...
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OP stated he does not appear to have enough rear rebound damping to run a higher spring rate. I was pointing out that I can run a 900lb spring at 3/7 damping without issue. It makes me wonder, is the damping really that poor with TCKline valved coilovers, or, does OP just have too much damping dialed in and he is riding on springs basically once the strut has been compressed? Or, does he have the rear springs preloaded? That would cause the return rate of the spring to be higher necessitating more rebound damping to control droop travel. Quote:
BC coil-overs are the only ones I know of that come with a stock spring rate like what you mention 10k/11k (98/107 N/mm) and it rides awful. Quote:
The car doesn't just under-steer because the front wheel rate is higher than the rear. You have to exceed the tires ability to maintain grip first. Driving style is the #1 contributing factor to causing ANY kind of traction loss. If you just cornered slower the car wouldn't break traction, right? Whether or not the aforementioned springs rates are stiff can be a bit subjective and is completely relative to the rest of the cars setup ride height, tires, track width, alignment, damping, etc Quote:
A quick google: Hypercoil: https://www.hypercoils.com/spring-rate-calculator/ Koni: http://www.truechoicekoniracingservi.../worksheet.pdf Eibach: https://eibach.com/america/p-101-sus...worksheet.html Eibach: https://eibach.com/de/sites/default/...rings-EN_0.pdf As a reference, spring rates for the E82/135i are: BMW M sport = 120/350 lbs/in. Dinan = 144/490. Cobb = 148/457. BMW performance = 160/420. Swift Spec-R springs = 201/ 503. Moton SS kit comes with 360 front and 620 rears E92/M3 specific Swift Spec-R springs are 279/670. F82/M4 specific Swift Spec-R springs are 279/726. Seems to me that spring manufacturers have all specd springs to provide a ratio of at 1:2-1:3 to achieve a neutral effective wheel rate. Literally every car manufacturer in existence does the same. The question that you might be able to answer for us is... what do the German track bros know that BMW, Porsche, Mercedes, Eibach, swift, hypercoil, and others all don't? The math is just meaningless anyway, right? Quote:
Ok, so lets go back to OPs issue. His car is understeering which means he is exceeding the grip available at the front tires. The answer here is not USUALLY to stiffen the rear (unless we are talking on-power exit understeer), as others have already stated and I never suggested he do that. That was a side conversation. What we really need to know from the OP is where in the corner is the understeer occurring? OP can try the following (I am no expert, but this is based on what I have learned): Some generic things: Lower the front ride height modestly if not already done so. A lower ride height = lower roll center = greater distance between COG and RC = more roll torque = more grip. Run stickier front tires Reduce the front track width (remove spacers) = lower roll center = more roll = more grip Increase rear track width (opposite of above). Less rear roll = more front load distribution. This is one of those dont take grip away from the opposite end things though Reduce front toe-in Decrease front tire pressures (I run 26-28psi cold and aim for <34psi hot). Decrease front spring rate (not suggested as youll introduce bind without making the springs longer and the ride height will be slammed). Decrease front sway bar rate. If OP has the stock sway bar in, he should do what I did and remove the stock sway bar mounts from the sway bar. With the mounts glued to the stock bar the bar can't pivot and it is also contributing to compression rate and not just roll rate. Corner entry understeer: *Decrease rear rebound damping Less rear damping = more weight shifting forward more quickly over the front wheels = more grip. *Decrease front Compression damping More dive = more weight shifting forward more quickly over the front wheels = more grip. *These recommendations assume weight transfer IS NOT already happening fast enough (OP stated he is running max rear rebound damping). If Weight transfer is already happening too fast, and under-steer is being caused by overloading the front tires, then you would want to do the opposite of this and INCREASE rear rebound to prevent the front tires from becoming overloaded under heavy braking. See page 24/26 for a more in-depth explanation here: http://www.kaztechnologies.com/wp-co...ak-Updated.pdf Corner exit understeer: Increase front rebound damping Less rearward weight transfer = more front grip = less corner exit understeer. Increase rear compression damping Less rearward weight transfer = more front grip = less corner exit understeer. There are plenty of things that can be done to balance the car Which one is best for OP will depend on his setup Last edited by bbnks2; 02-13-2018 at 11:41 PM.. |
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02-13-2018, 05:58 PM | #29 | |
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02-13-2018, 10:50 PM | #30 | |
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As for the sway bar, the mount bushings were molded to my sway bar. I had to heat them up and cut them off. Now the bar is free from bind for me... Last edited by bbnks2; 02-15-2018 at 08:47 AM.. |
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02-14-2018, 02:02 AM | #31 | |
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Sorry for Offtopic, hope itīs ok since it is still somehow connected to the original Topic.
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I am 100% percent sure, that the spring rates for the 135i KW Clubsport 2 Way with Uniball Camber Plates in the front are: Front 70N/mm, Rear 80N/mm (in the rear there isnīt a linear spring but a progressive one, so the 80N/mm is the middle value of the spring). The Setup for 1 M-Series and M3 from KW for the Clubsport is 110N/Mm in the Front and 120N/mm in the rear (here the rear has a linear spring and a helper spring). I know a lot of cars which got a Setup from Raeder Motorsport, which is a famous Workshop around the Nurburgring. On one 335I for Example they installed 110N/mm in the front and 80N/mm in the rear (with KW Clubsport Dampers). So almost exactly the other way around most of you guys are stating. Also Öhlins uses 60 and 70N/mm F/R for their Road & Track Version for the AG Model 135/335i. Bilstein Clubsport have the same odd rates... I will try to install a 120N/mm spring in the year just to see how the car will behave with them installed. What i just donīt get ist how can most of the cars here in Germany (and i talk about most n54 powered cars, not e36 or others) run in your opinion such a wrong spring rate Balance? |
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02-14-2018, 07:17 AM | #32 |
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I asked you for that answer... you give me one logical reason for doing it. I've already spend hours typing out the logical reasoning for NOT wanting to do it. Your only rebuttal appears to be "but all the cool kids in Germany do it."
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02-15-2018, 01:36 AM | #33 |
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You Sound so offensive, i donīt want to offend anybody just to say :-)!
I really donīt know any reason for it, what i know is that the most cars using this Balance are really fast (07.30 NOS BTG) and that KW theirself uses this rates. And i highly doubt that KW uses These rates without a reason or because they drive so bad? I just want to understand why |
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02-15-2018, 07:20 AM | #34 | |
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Maybe they run a really staggered tire setup? Maybe they've just compensated for it with driving style? Maybe they run a lot of rake? Too many variables to say... Like I already said, you can combine 20 different other tweaks to get the car balanced back out. Tweaks you wouldn't have to do if you just started with a neutral base... Last edited by bbnks2; 02-15-2018 at 07:47 AM.. |
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02-17-2018, 02:41 AM | #35 |
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UUC has a weekend sale going on, so I bit the bullet and ordered the 19mm rear bar. It's going to suck to install, but hopefully it fixes the issue.
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02-17-2018, 03:06 PM | #36 |
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This is the most peculiar thread. I wonder how many people actually drive their cars competitively / at the grip limit versus just reading other people's posts and regurgitating the same bad information.
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02-17-2018, 06:18 PM | #37 |
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None of us. We don't even own cars at all. Thank god you're here.
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02-17-2018, 08:17 PM | #38 |
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So, where is all this good information that you can provide in response to the op? Did you even read the thread?
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02-18-2018, 10:57 AM | #39 | |
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I ran the car on several different rates. I started with 400/850 w/stock rear bar and a reasonable front (27mm adjustable). It was such horrific push I can't possibly describe. Those who aren't experiencing it are simply underdriving the car, period. Kyle warned me about it when I mentioned wanting to try it (he ended up at 400/700 with a 19mm rear bar and slightly softer front than me), but it was still there, very badly. I switched to 575/1200 (because the car was rolling well out of its camber curve up front as well), and went to a 20mm rear bar). It was much, much better. I've switched shocks and don't campaign the car very much anymore. I'm at 450/850 with a 20mm rear bar and 27mm front bar. Even at 575/1200, the car rolls a LOT because of how bad the motion ratio is in the back, it's hardly any wheel rate at all. The stock spring rates for the car are biased nearly 3x (160/420). Yet it still pushes pretty badly. Just adding a mountain of camber does not solve this. It's a wheel rate of 150/135, because of the motion ratio. I would use as a starting point a similar wheel rate target if you want to keep the stock rear bar. So, starting with a 400lb spring, you're looking for a wheel rate of around 320lbs, or a 1000lb spring. Of course, after going to a larger front bar, you'll want to add the requisite rear rate to compensate for it. I ran the numbers to keep my balance on 450 fronts with a stock rear bar, and it required (I think) around a 1350lb spring. That's why people add bar / run a lot of spring. Look up the OEM M3 rear sway bar size and you'll see that a lot of the justification on here makes very little sense unless you're keeping the open diff. It's substantially larger than what either of us ran. |
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02-18-2018, 02:24 PM | #40 | |
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Is the M3 rear sway hollow like the front? |
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02-19-2018, 06:26 AM | #41 | |
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Suggestions like running mega-soft front rates and unhooking the front bar on a car with a miserable camber curve to begin with. Suggestions that "OMG these consumer level coilovers for the street have softer rear rates so that's optimal!" Suggestions that because a shock can jack down a spring it's great for a given spring? Come on... And for some reason people here continue to suggest mega-soft rates. I'm sure I know why, because they're running pretty awful cheap dampers without even bothering to look at a shock dyno, and wonder why the car rides poorly, so soften the springs as a band-aid. The way I see it, there are two reasonable options to balance the car, run a lot of rear spring (which again, looking at wheel rates, isn't that much), or run something like the 20mm bar I have, the 19mm UUC bar Kyle has, or an OEM M3 rear bar (the route I'd go now if I were developing the car). The vert bar is larger than the sedan/coupe bar. Given the front camber curve, I would run as stiff as one reasonably could up front for a given surface while still maintaining some semblance of compliance. The front of the car is also really limited on static camber (the highest numbers I'm aware of were in the mid/high-3s for Kyle, and I don't know that many others have been able to get there. When I had the JRZ plates, I also had offset bushings and was at mid-3s. Still not really enough. It was okay on RE71s as they don't seem to want as much camber as other tires, but if I'd run BFGs or a Hoosier on the car, I'd be doing everything I can to maintain camber in roll / increase static camber. The rear of the car is basically the exact opposite, in that it gains a ton of camber in roll, so you really don't need very much back there (especially with these soft rear rates, the rear will compress a ton, I know Kyle has some picture of the rear wheel totally buried in the well in Pittsburgh). This picture was on 575/1200, and it is still rolling a ton, and you can see the deflected front tire going positive even with ~3.4 degrees of camber. |
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02-20-2018, 06:35 AM | #42 |
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Oh, you mean this one? Granted, this was cause of a massive dip/bump...but yea, that shock did compress probably to it's full extent lol
I like this one as well. |
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02-20-2018, 09:00 AM | #44 |
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