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05-24-2018, 03:12 PM | #23 | |
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Personally, I just bored out the stock bushings a bit. You can also add a small spacer (washers) the brackets to reduce the clamping effect. Or, get aftermarket bushings for the stock bar... Reducing rake is generally not going to increase front-end grip but rather have the opposite affect. If you think the stock bar is too soft you might want to try raising the front end a bit at the same time to reduce the moment arm affect. Last edited by bNks334; 05-24-2018 at 03:20 PM.. |
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05-24-2018, 04:25 PM | #24 | |
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Yes I'm on coilovers. TCK SA front with 7" 7k swift, Bilstein monotube rear with 10" 12k swift. I thought the stock bar was too soft with stock springs. With the coils the H&R bar was way overkill and with absolutely no bar it's just a touch too much oversteer oriented. Think it still needs some bar, but stock bar (26.5) may still be too much.
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05-24-2018, 08:33 PM | #25 | |
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I measure rake from the side skirts right next to the jack points. Without knowing your front and rear ground clearance and other settings like static camber it's hard to make a suggestion. Raise the rear? Lower the front? Increase front spacers? Reduce sway bar bind and reassess? Before you do anything I would check to see if youre bottoming out your rear struts and causing a spike in rear wheel rate. You may find that you're getting into the bumps stops like both myself and Felix found. Read through the 10 page ohlins thread I linked to and you'll see that he actually moved to a 14k spring and a bigger rear bar to alleviate the bump stop enaggement. You are running longer 10" springs though so I am guessing you have a lot of spring preload in the rear and the issue may not be as bad. No one likes to believe in the 1:3 ratio but lower the rear of the car onto the ground and watch how you lose 3" of suspension travel when you use 700lb springs and that is just from the weight of the car lol When you have afternarket coilovers with only 4.25" of usable travel that becomes a big deal... Last edited by bbnks2; 05-24-2018 at 11:00 PM.. |
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05-25-2018, 08:05 AM | #26 | |
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As for preload, I have the front and rear set to where the springs are barely free at full droop. So from my understanding, there shouldn't be any preload. If I raise it a bit, yeah. When you say 1:3 ratio are you referring to spring rate or rake?
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05-25-2018, 09:32 AM | #27 | |
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If you have a 10" rear spring at 700lbs, and it has no preload on it, you might have a pretty long shock adjustment range in the rear. Without preload I would guess that you're practically sitting on the bump stop at static ride height (~1") and your ride height is fairly low like 4-4.25"? Crawl under there and take a look. Zip tie the strut to see how far it gets pushed into the bump stop. Maybe I am wrong but I am curious to see your results and measurements. Definitely something to rule out before you go playing with anything else. Last edited by bNks334; 05-25-2018 at 09:48 AM.. |
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05-30-2018, 03:28 PM | #28 | |
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Happy to measure the strut, but confused at what you're looking for. Shock travel without spring installed? Or suspension travel all bolted up by jacking the at the arm? Help me out here.
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06-02-2018, 08:01 PM | #29 | |
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Measure the available strut travel with the car on the ground. Then jack the car up and measure total strut travel at full droop... I might move to a 7k/20k spring setup. 16k still seems too soft and I don't want to have to raise my ride height through spring preload just to gain a bit more bump travel. Here is what I mean by measure the rear strut travel: Last edited by bbnks2; 06-02-2018 at 08:19 PM.. |
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06-03-2018, 08:59 AM | #30 | |
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On another note, what's leading you to feel you need such a high spring rate in the rear?
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06-03-2018, 05:37 PM | #31 | |
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Look at the above picture... I put my car on the ground and I lose 2.33" of my 3.25" of suspension travel (700lb sprung weight / 300lb effective spring rate = 2.33"). As soon as I turn into a corner the car is riding on the rear bump stops. Why is that bad? Because of the exponential increase in rear stiffness when the bump stop is engaged, as covered earlier. By moving to a 20k spring I'll be able to gain a bit more bump travel (700lb/350=2). The 20k spring will support the weight of the car better. Not all coilovers have the same travel so I asked if you could measure yours to compare. I am guessing that riding on the rear bump stops is misleading a lot of people to think their rear setup is too stiff when in actuality it's too soft and they are just riding on the bump stop. |
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06-03-2018, 06:13 PM | #32 | |
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06-04-2018, 09:00 AM | #33 | |
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Here is his assessment of the rear OE suspension and his aftermarket Ohlins suspension. https://www.1addicts.com/forums/show....php?t=1075240 You can see in his posts how the stock suspension rides on the bump stop which is exactly what I am trying to combat now myself with aftermarket suspension. This is intentional design on a street car for softening harsh bumps, but it creates a handling imbalance when stop engagement is not tuned properly from front to rear. You can see that even with 14k rear springs fe1rx only has 1" of travel before getting into the Ohlins bump stop which is the same thing as only having 1.3" of bump travel up front... (***** this is fairly blanced on an Ohlins setup but not my YCW). The linear spring rate then gets progressively stiffer as the bump stop compresses. You want bump stop engagement to happen at both ends of the car AT THE SAME TIME or the handling will shift as the suspension transitions from leaning on the springs to leaning on the bump stops. Also, It makes sense the YCW rear struts I use would have less stroke (only 3.25") than the front since the rear struts only have move 80% as much as the front to achieve the same movement at the wheel (rear strut motion ratio is .7x? and front is .9x?). It's just a matter of getting the right bump travel distribution F:R to ensure the car stays neutral in roll. I have roughly 50/50 bump/droop distribution in front and I need the same in the rear to match. I plan to adjust the shock body shorter to achieve this. Right now in the rear I have 40% bump and 60% droop so the rear is going to get into the bump stop a bit earlier than the front causing brief over-steer characteristics as the car takes a set. I need 3/8" more rear bump travel! *****Looking back, I was surprised to see how little the stock bump stops contribute to the effective wheel rates. It's clear that the much stiffer YCW bump stops would have a much more significant impact on effective wheel rates than the soft stock bump stops that don't contribute much until they are compressed by over 1". Also, looking at the testing felix did of the Ohlins suspension, their stroke is significantly reduced by an internal damper that begins being engaged at as little as 3" of compression up front. This may induce under-steer in many Ohlins specific setups depending on spring rates. Last edited by bbnks2; 06-04-2018 at 10:42 AM.. |
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06-04-2018, 06:51 PM | #34 |
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OK, so put the car up and checked. Hard for me to look at it accurately without taking the dust boot off, BUT, pinching through the boot I have conservatively 3.25 at full droop, and somewhere right around 0.75 at ride height.
//Edit: Front droop is ~ 3.3" and best I could figure about 1.25" compressed. Really tight in there at ride height so that's really more of a guess. What I did note is that the bump stops themselves are HUGE! Between the long damper and the tall bump stops, I'm not confident that I'm not spending half my time driving just bouncing off the stops. Ride height from floor to bottom of rocker panels is 6" front and 6.75" rear. So, in terms of rectifying this, as I understand it: I have two things that need to be done. 1: I need to get these band-aid bilsteins off the car and a replacement set of proper rear dampers. Then once I do that, measure available droop again, and compare to the front. 2: Obtain an appropriate length and rate spring to actually support the weight of the car and preserve travel. Then I can start looking at fine tuning.
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06-04-2018, 07:30 PM | #35 | |
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I am just pointing out that problems arise when you choose springs that engage the bump stops at different times. If you have .75" of bump travel in the rear, you would need the front to have roughly 1" of bump travel for the front bump stop to come into play at the same time as the rear in roll. There is nothing wrong with getting into these large bump stops since they are so soft. You just need to make sure youe effective wheel rates are balanced so the bump stop engagement happens on both ends of the car at the same time. I'd need to have every detail to help you further than pointing you to this potential concern. 6/6.75 would be right around stock. You measured to the bottom of the side skirt? Last edited by bbnks2; 06-05-2018 at 07:54 AM.. |
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06-04-2018, 07:55 PM | #36 | |
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Yeah I did. I'll measure the ride height again tomorrow. It's definitely not over stock height.
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06-26-2018, 04:05 PM | #37 |
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Welp, I made it out to the time attack this weekend and had fully intended on doing some sway bar testing. Practice and first timed runs went great. Between first and second heat, I had planned to sway out my H&R front bar for the stock bar to get some subjective and objective comparisons. While I was trying to remove the H&R bar, though, one of the bolts broke free on the back side where it was welded? to the subframe. Now it just spins. I'll probably have to drop the subframe to get it out and replace it with a regular bolt I guess...
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03-26-2019, 10:28 PM | #38 | |
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Thoughts as an alternative strategy to running the oem bar? |
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03-27-2019, 07:37 AM | #39 |
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Adding the stock sway back in is a hell of a lot easier than swapping springs. You can definitely set a car up without swap bars. It's just a matter of knowing what scenarios you might want to do that... it's good to get a it of roll resistance from the sways so you don't need to run crazy high spring rates.
Last edited by bbnks2; 03-29-2019 at 10:01 AM.. |
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03-27-2019, 08:46 AM | #40 |
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To update.
I've gone back to the stock bar, increased rear spring rate to 1:3 ratio, stock rear bar, added LSD. Definitely the best balance for oscillation and traction for the car. At this point I'd advise a stiffer front bar if sticking with the stock Msport suspension, but if fiddling with spring rates I'd stick with stock bars all around.
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