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08-13-2019, 10:18 PM | #1 |
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Rear upper m3 arms hitting chassis
Has anyone run into this issue? I recently switched out my dinan rear shock mounts to akg black mounts to reduce the suspension travel in the rear. Initially it was to prevent the passenger rear tire from hitting the fuel filler neck.
After a few canyon runs the issue appeared to be fixed...until I started working on my rear brakes last weekend. Not only is the tire still hitting the fuel filler neck, but my rear m3 arms are hitting the chassis. Has anyone else run into this problem with rear m3 arms? I have some suspension “packers “ (picture below) someone told me about in a different thread. I guess I need to insert one to reduce travel a little more and see how things are but I am really curious if anyone else has run into this and what you did to resolve it. It’s possible this was occurring with the dinan mounts and I didn’t notice. However, after seeing the tire is still hitting the fuel filter neck, I am still suffering from too much suspension travel, so it’s possible the upper m3 arm contacting the chassis is still occurring with the akg mounts as well. Rear suspension setup: m3 upper arms, m3 lower camber arm, m3 TC Kline DA rear shocks, 600lb TC springs, toe arms, white line rsfb. Would love to hear other people’s experiences.
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Last edited by houtan; 08-14-2019 at 12:53 AM.. |
08-14-2019, 06:20 AM | #2 |
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Almost looks like the bump stops are too short...
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135i - E82.N54 2009 BSM - MHD / xHP / DCI, PR CP & 7.5" Race IC / N55 mid & Borla . . WL RSFI, Koni, Eibach & Dinan CP's, M3 CA's / EBC Red's & Firehawk 500's X1 - E84.N20 2013 MGM - JB4 - The Wife's, now with new turbo & ewg |
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Dackelone10590.50 |
08-14-2019, 08:56 AM | #3 |
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Are they upside down? Can't remember which arm back there is installed the other way.
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08-14-2019, 09:01 AM | #4 |
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^^
They are handed. Someone else on here (not me honest) had a professional shop install them wrong.
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08-14-2019, 09:30 AM | #5 |
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From this thread....
https://www.1addicts.com/forums/show....php?t=1079383 The M3 Guide Rod is forged aluminum with inboard ball joint and outboard rubber bushing. The forged bodies of the LH and RH arms are identical but installation of the bushings makes them handed. The bodies are curved (downward), not for installation clearance issues, but to ensure that the compressive failure of this member will be by progressive bending. The ball joint used at the inboard location effectively doubles the stiffness and halves the deflection under axial loading versus the OE Guide Rod, which will alter (and presumably decrease) compliance steer effects. Also from post #72 is discussion about wrong installation.
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08-14-2019, 11:08 AM | #6 |
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Very interesting. I just got a set of replacement rear arms that I was about to install as well. And I have almost the same setup as you, except I'm using the 135 rear shock and camber arm not the M3 one.
I'm also using the stiffer Monroe upper shock mount, not sure how it's dimensions compare to the AKG ones though. How low is your car? |
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08-14-2019, 03:07 PM | #7 |
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Thanks for the posts.
@shocknawe, I am 99% sure they are not installed updside down. But anything is possible and it wouldn't be the first time I did something wrong! Based on the fe1rx link, I have mine installed just as the picture in his op. gjm120, I believe the excerpt you posted is for the guide rod, which gets mounted curve side down, but points angled forward sort of. The arm in my pictures that is making contact to the chassis is the wishbone, I believe that should be mounted with the curve side up, which is how I have it. @dtla, My car is not that low imo, but the best way to tell the ride height is to look at the pictures in my "garage". My guess is I have a half to one finger gap in the rear. @1and1, I do think the bump stop may be to short and I need to add one or two packers to limit travel.
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Last edited by houtan; 08-14-2019 at 03:46 PM.. |
08-14-2019, 03:32 PM | #8 | |
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Another consideration is that maybe you have things switched and have the guide rods in the wishbone spot??? As a last resort, you could always consider going back to the stock 135i wishbone that is straight. It has the same bushing/bearing setup as the M3 version, so the only performance penalty is just a little extra weight from the steel vs. aluminum. Last edited by duder13; 08-14-2019 at 03:39 PM.. |
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08-14-2019, 03:53 PM | #9 | |
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08-15-2019, 05:12 PM | #10 | |
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I remember it being pretty damned hard to install them backwards as they are handed.
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08-16-2019, 08:41 AM | #11 |
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Thanks for double checking.
I discovered something interesting yesterday afternoon. So I jacked up the passenger side suspension to mimic being on the ground and took some measurements. It seems the amount of suspension travel I have is equal to the amount of space between the wishbone and chassis. So once the bump stop starts to compress the camber arm would be touching the chassis.
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08-21-2019, 11:07 AM | #12 |
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Finally got everything back together.
Here are the packers I used, which are 17mm ID and the same as the one that came with the shock. https://performanceshock.com/index.p...oducts_id=1127 They are an 1/8" thick, so I started with adding three more to each side. I am guessing that leaves me with around 3/4 of suspension travel. Going to drive around like this for a few thousand miles. If there is no contact, I may remove one.
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08-22-2019, 09:03 AM | #13 | |
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Are the TC Kline struts adjustable (threaded body)? To solve the contact issue without sacrificing bump travel, I would raise rear ride height 3/8" with spring pre-load, turn the dampers up 1-click to compensate, and then make the strut body longer by 1/4" or so. If changing the strut length isn't an option then use the packers or look for a better/longer/stiffer bump stop. Remember that the contact point between the wishbone and chassis is inboard from the strut. The wishbone will not travel in 1:1 fashion with strut travel. Motion ratio... If you have 1-2" travel at the strut then the wishbone may only move something like 3/4-1.5." Looks like TCKline is using very tall stock style "spring supporters." You may only have 1" of travel until you get into the bump stop but the bump stop probably compresses another 3/4-1" under load. The evidence of contact is clear but maybe something just got jammed up between there? Can you jack the entire rear-end up, then use another jack to jack up one tire until you get into the bump stop (full compression)? Then take another pic? I can do the same tonight and see where I end up with the M3 subframe. Last edited by bbnks2; 08-23-2019 at 11:47 AM.. |
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08-23-2019, 11:31 AM | #14 | |
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08-23-2019, 11:46 AM | #15 |
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08-23-2019, 12:31 PM | #16 |
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Thanks for the replies
dtla1, yeah you are right, I am running the m3 lca. bbnks2, I plan to look at where everything is at when the bump stop is engaged, but I would need to remove my rear spring and I didn’t have time. In truth, I got Falken azenis 615+ tires mounted like three weeks ago and I just want to go drive lol. So I put it back together with the added Packers. I did take a picture of the travel with the suspension fully unloaded and I believe the amount of travel was more than three inches. Is that what you are referring to as bump travel? Appreciate the insight into the travel between the shock and arm is not 1 to 1. The TC Kline shock bodies are not threaded unfortunately. Just the spring perches are adjustable. Turner makes an upper mount that is adjustable, but i don’t think it works with the size of the TC shaft. I wish it was something that was stuck between the arm and body causing the contact, but I can clearly see where it is hitting. One side directly in the arm and the other side on the break sensor wire bracket.
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Last edited by houtan; 08-23-2019 at 12:38 PM.. |
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08-23-2019, 05:08 PM | #17 | |
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I put two bricks under my tire to fully compress the suspension into the bump stop. I have quite a bit of clearance between the wishbone and the chassis still. See below. I have an adjustable arm in place of the m3 whishbone but that shouldn't make much difference anywhere near what you're seeing. I sit at like 4.5" of ground clearance to the bottom of the rear side skirt. How low do you sit? Seems really odd the arm would ever hit the chassis there... my diff would be dragging on the ground if the rear squated that much lol Last edited by bbnks2; 09-03-2019 at 07:16 AM.. |
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08-23-2019, 06:19 PM | #18 |
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OP your M3 arms looked to be installed correctly. Upper arm should bend upward with the forward link should bend downwards. Here are pics from my 135i.
I think your problem is with your bump stops. On the upper spring perch.. there should be a rubber bump stop to prevent the car from bottoming out. Have you tested IF your rear shocks are blown out? Try compressing the shock off the car. This could be the cause. IDK about those plastic spacers on the shock body. Looks sketchy to me. As for your tire rubbing on the RR... I would buy a set of 5mm or 7mm spacers for the wheel WITH new bolts. $100. 10mms will rub. Dackel
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08-23-2019, 07:52 PM | #19 |
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Yeah I think hes already got the solution. Packers are fine. It's more of a question of why... I was thinking of moving to m3 spec struts since I have the m3 rear end. I reused my stock camber arms and struts for now. If I'm going to have too much bump travel with m3 struts then that's an issue lol.
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08-24-2019, 09:32 PM | #20 |
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So here are the measurements from the bottom of my wheel to bottom of fender. These are with the packers installed which reduced travel 3/8”.
Static height: 22.5” Compressed: 21” Off the ground: 26.25 My rear rocker is about 6” off the ground. That’s from the actual rocker not the little rock protector/mini mud flap thingy. My wishbone clearance looks like yours now. I actually went on a canyon run today and drive really hard. No issue with the arm to chassis Contact. So I am really happy about that. I love my new tires too. Last edited by houtan; 08-25-2019 at 01:39 AM.. |
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08-24-2019, 09:44 PM | #21 |
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Thanks dack. I am currently running a 3mm spacer and that is the absolute max that would work . I posted some pictures in the fuel filler thread. I literally have zero extra space on either the inner and outer fender.
I don’t think anything is blown so that’s good. Even if a 10mm spacer could fit , it probably wouldn’t fix the rubbing issue. I removed my spring and shock and checked for myself. It’s going to rub either way. So limiting travel seems like a great solution. Especially since I didn’t have this problem with B8 |
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