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08-10-2019, 09:49 AM | #24 |
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Just a quick note to say I have just installed meyle balljoints (part number 314-710-0005-INT, at Pelican Parts) for the trailing arm and toe. They looked quite good with negligible bind.
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08-24-2019, 10:17 AM | #25 |
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Good to hear! I’ve been debating contacting Bimmerworld to see if they made an update after OP’s complaint or buying some TRW/Meyle/Lemforder Arms to get the spherical bearings. Keep us updated!
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08-25-2019, 03:10 PM | #26 |
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That is a good find. Much cheaper than my convoluted experience!
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08-29-2019, 05:47 AM | #27 |
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Yes, but we have you to thank for that.
Also, did you see the toe arms we have made, as posted on a few boards (see https://www.e90post.com/forums/showthread.php?t=768710&page=2), with the following note: Hey guys. We have manufactured rear toe arms for the e82 and e9x non-M. The design principle is a curved arm, but with dimensions better suited to the non-M suspension. These are made of billet 6061-T6 aluminum and have been precision CNC machined to accept either balljoints or bushings (which can be either stock bushings or much stiffer Group N bushings, or even some polyurethane bushings), or any combination of balljoints and bushings depending on individual preferences. They can be anodized in any colour. They can also be made either in the standard length (412 mm) or +3 mm for extra toe. Because you can select balljoints or bushings, or any combination, you can tweak your effective spring rates in increments (measured in lb/in). So, for example, on effective spring rates: - 2 balljoints: 0 - 1 balljoint and 1 regular bushing: 15 - 2 regular bushings: 30 - 1 balljoint and 1 Group N: 56 - 1 regular bushing and 1 Group N: 71 - 2 Group N: 112 Assuming the contribution of a full set of stock bushings is an equivalent of 109 lb/in, then that can be fully compensated with a set of MRP toe arms with 2 Group N bushings, and the other 4 arms can be only balljoints... Just trying to gauge interest at this point so please reply if you might be interested in this product... |
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08-29-2019, 05:59 AM | #28 |
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I would also note that so far I quite like my setup which uses 3 Group N bushings - one each in the toe and trailing arms, plus one on the inboard side of the lower camber arm (the rest being balljoints except for the normal bushings on the outboard side of the M3 upper arms). Since the Group N bushings are very stiff, they provide not only additional spring on compression but also additional rebound, below normal or static height. Above static height, they work against the metal spring, pulling the suspension back to static height. I have a 521 lb spring and say about 180 lb equivalent spring rate from all the bushings. So on compression, below static height, together they add up to about 700 lb, but above static height the effective spring becomes around 340 lb. This helps the sway bar do its job and the car levels very quickly...
So there is a reason besides rules to use Group N... a Stay tuned |
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08-29-2019, 09:30 AM | #29 |
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Have you, or anyone else, found a similar style ball joint that will work for the rear upper arms?
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08-29-2019, 12:11 PM | #30 | |
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a Stay tuned |
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08-29-2019, 01:44 PM | #31 | |
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Stiff, short rear springs could potentially come unseated under full droop as set by the shock. Potentially rubber bushings could keep the springs seated by preventing the suspension from getting to this mechanical limit. |
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08-29-2019, 01:48 PM | #32 | |
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With respect to the toe arm I ultimately replaced my machined/ball-jointed toe arm with an SPL part. The only real benefit in doing this was to gain the ability to adjust toe with a turnbuckle rather than the eccentric bolt. I do my own string alignments on hub stands, and I find that the turnbuckle really makes my life easier when aligning. |
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08-29-2019, 03:13 PM | #33 | |
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I have 39k street miles on my Rogue toe arms and they're still tight. The rod ends they use aren't FKs strongest but the original NJM series are holding up just fine. I even bought (higher spec) replacements but they just sit in a drawer, waiting. I've replaced the Seals-it WS series rod end seals twice due to rubber cracking, however. I'm thinking of switching to the RERS series boots, but why fix it if it isn't really broken? FWIW, I just installed Lemforder 3067901 spherical bearings in the hubs for the trailing arms. A bit of initial stiction, but once overcome the movement is smooth and easy.
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08-29-2019, 04:06 PM | #35 | |
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Second, on the above, I hear you, but consider this: if I have a 521 lb spring and bushings that equate to 180 lb, while the spring is pushing toward droop with a force of 521 (below static height), won't the bushing be pushing toward static with a force of 180, so shouldn't that be subtracted from the force of the steel spring at positions below static (droop positions) just as it is added to the force of the steel spring at positions of compression. It's an opposing force at positions of droop. I think it has to be subtracted at those positions. If that's true, then I effectively have different spring rates depending on whether the wheel is at compression (add bushing) or droop (subtract bushing) which helps the sway bar do its job.... a Stay tuned |
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08-29-2019, 04:12 PM | #36 | |
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08-29-2019, 07:20 PM | #37 |
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Although I think the right calc has to also take into account the unsprung weight of the corner, which represents additional work (besides fighting the spring) the bushing has to do at droop to pull the wheel back to static.
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09-11-2019, 09:10 PM | #38 | |
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a Stay tuned! |
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09-11-2019, 09:27 PM | #39 | |
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a Stay tuned! Last edited by Angel67; 09-11-2019 at 09:57 PM.. Reason: Clarification |
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09-13-2019, 09:38 AM | #40 |
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Fe1rx- have you looked into the affect the adjustable rear guide arm may have on rear caster angle?
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09-25-2019, 02:36 PM | #41 |
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The rear caster varies very dynamically with suspension travel. Typical values would be -4° at full droop to -11° at full compression. I can't see any benefit in making a small change in rear caster by adjusting the guide arm, and I suspect any such change would have a detrimental effect on rear bump steer (although I have no numbers to prove it). To minimize that possibility my opinion is that the trailing, guide and upper arms should remain OE length.
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09-25-2019, 03:33 PM | #42 |
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The Benefits - Measured
I have data from 2018 (pre-spherical) to compare to 2019 (spherical). In both cases the car has a wing and a splitter, but the 2019 splitter is "improved". The track is the Mosport GP (AKA CTMP GP) and the lap times are comparable at 1:34. 2018 was cooler so had more power, but 2019 corner speeds were a bit higher, giving about the same lap time.
Plotting steering angle against lap distance reveals that the spherical car requires less total steering input, despite the fact that the cornering speeds are generally higher. Lower trace is GPS speed vs distance. Another way to plot the same data is as an x-y plot of steering wheel angle vs. lateral acceleration. Once again it is clear that less steering angle is required for the spherical car to produce the same lateral acceleration. Actual understeer can be estimated by calculating corner radius from lateral g and speed, calculating ackermann angle from wheelbase (2.66 m) and corner radius, and comparing the ackermann to the actual steered angle at the tire by dividing the logged steering wheel input by the steering ratio (16.36 near center). The method is mentioned in Bob Knox's "A Practical Guide to Race Car Data Analysis" if you want to chase down the details and the limitations of the method. Whatever its limitations, it is probably good for comparing two setups of the same car, as we have here. This method shows a reduction of understeer mid corner of up to 1°. My hypothesis is that going spherical (and solid RSFBs) reduces compliance steer effects and loss of camber. This reduction provides greater total grip, reduced understeer, and thus less total steering input being required. |
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09-26-2019, 01:16 PM | #43 |
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Great use of data! Spherical is in blue?
It seems there is a noticeable improvement, but where would you rank this upgrade relative to others?
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09-26-2019, 01:50 PM | #44 | |
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As to rating the mod, most mods don't show up so decisively in the data, so that is satisfying. And one never has enough data ... From the driver's seat, I would call the change subtle (vs M3 arms all around and M3 RSFBs), but of course there was no possiblilty of testing before and after back-to-back. The absolute best bang for the buck in terms of feel would be replacing the RSFBs with M3 bushings. Now they are solid, but I have no idea how much just that mod changed things from the M3 bushings. In a perfect world I would do one change at a time and have data from each change. Of course, I didn't and don't. |
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