01-15-2020, 06:20 AM | #1 |
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Rear axle PU bush replacement - worth it?
Hey all
I have a bit of a dilemma that I'd appreciate some opinions on from more experienced folk here. I have done a few searches but couldn't find the exact info I was hoping for. Mine is an M140i, but the suspension and componentry is basically identical to the F30 cars. My current chassis mods are as followings: - Front strut bar (Ultra Racing - nothing special) - Rear underbody brace (OEM) - Front F8x lower and upper control arms - SuperPro differential bushes - SuperPro subframe bushes - Bilstein B14 I have a set of H&R swaybars that are waiting to go in. It will be a hefty/expensive job. I was wondering whether the rear control arm bushes would be worthwhile to do whilst the subframe is disconnected. I'd be looking at the SuperPro range. https://superpro.com.au/find/superpr.../cid-999501544 Can anyone care to offer their opinions or experiences as to whether replacing the rubber bushes at the rear with PU would be worthwhile? There are quite a number of them, owing to the various arms on that multi-link rear end. I had previously considered Hardrace sealed monoball rear arms, but have been told that aftermarket arms aren't ever as beefy as OEM parts so not to bother with them. https://www.hardracesuspension.com.a...55&car_type=17 |
01-15-2020, 08:19 AM | #2 |
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I got all bushings in my former E91 changed to powerflex PU bushes.
That made a huge difference. More precise steering and more suttle rear end. I would change if you are on it anyway
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10-16-2020, 04:23 PM | #4 |
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Posted the below on the babybmw forums but copying on here as most of the F3x chassis shares the same parts as on the F2x (minus xDrive, of course).
----- Well, here it is, the last of the handling mods and the result of 4 years' worth of research, trials and tinkering to get the car exactly how I wanted it. We finally managed to coax the stock rubber bushes out of the rear arms and replaced them with the polyurethane (PU) kind from SuperPro. First impressions were largely moot. The rear had always been stiff, owing to the subframe bushes (also SuperPro PU), but I wasn't quite sure whether there was really any material difference from the change to the rear arms. However, after a few more KMs, it is quite apparent that imperfections in the road are now more apparent. The rear is, for the lack of a better word, tighter. It feels like the B14s are made to work more, but in no way does it make the ride harsher/crashier. I've always been impressed with the way the B14s managed to round off sharp feedback even though it was just as stiff as the stock adaptive dampers with Eibach Pro and Eibach SP Pro spring kits. I can't help but note that this type of aggressive feel might not be to everyone's taste. But I love it and each to their own. It has, however, raised my suspicions as to whether the B14s are under-damped/over-sprung, as I feel the rear being a smidget more bouncy over undulations. But then again, I'm not an expert and it could just be due to a greater transfer of road feedback. Having said that, the general feeling is still very much one of "control" and "tight". We got these rear arm bushes as I was experiencing some axle tramp when losing traction under power. This was more prevalent in the wet. Initial launch trials in the dry point to a tied-down rear end with a smooth and controllable breakaway point, which is basically very similar to my initial thoughts when we had the rear underbody brace and subframe bushes installed (both done separately). This just adds a little extra. For context, other handling-related mods on the car: - Quaife LSD - Rear underbody brace - Front tower strut bar (Ultra Racing) - Front F8x control arms - H&R swaybars + adjustable endlinks (SuperPro) - Rear subframe PU bushes (SuperPro) - Rear diff PU bushes (SuperPro) - Bilstein B14 Did I say this would be the last handling mod? 🤣🤣🤣 The next stage would be to re-spring and re-valve the B14s, although that won't happen for some time as I explore the current setup. |
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10-19-2020, 03:59 AM | #5 |
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That's a nice setup, although personally I found the H&R bars to be too stiff with Ohlins R&T and am replacing them with Eibach units - the rear is already in and the front is being done in a couple of weeks' time along with SuperPro rear subframe poly bushes.
Interested in whether you noticed any significant changes/benefits by replacing the diff bushes with poly units.
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Current : F31 330sD, remapped, Ohlins Road & Track, Millway camber plates, Quaife LSD, Stoptech brakes + Pagid RSL1 pads all round, Weichers front strut brace, Eibach front & rear anti-roll bars, Michelin MP4S.
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10-20-2020, 02:56 AM | #6 | |
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10-20-2020, 11:35 AM | #7 |
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If your suspension is like mine (2013 335 xi F30) and if you have access to a lift the rear sway bar, which should be the same as my xdrive, is really easy. I added some Powerflex bushing inserts when I dropped the rear subframe. I don't know about your front swaybar but the front on my xdrive is pretty easy as well. I supported the engine from below and lowered the front subframe (didn't have to drop it completely) and it was fairly easy to change out. I followed the instructions for the Dinan sway bars.
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2013 BMW 335xi F30 N55 PWG/VRSF DP/ER CP/Injen CAI/AA FMIC/JB4 map 7/Fuel= E50 w/ E85:93oct/Stock LPFP & HPFP/CATuned coilovers/Megan Racing Rear Swaybar/Powerflex Rear Subframe Bushing Inserts/Dual aFe Power Mach Force Mufflers/Resonator Delete/MHD & BMS Race BEF
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10-20-2020, 12:16 PM | #8 | |
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As per my previous post, what are your thoughts about poly bushes for the diff ?
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Current : F31 330sD, remapped, Ohlins Road & Track, Millway camber plates, Quaife LSD, Stoptech brakes + Pagid RSL1 pads all round, Weichers front strut brace, Eibach front & rear anti-roll bars, Michelin MP4S.
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10-21-2020, 07:50 AM | #9 | |
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I'm trying to stick with the H&R at this point, changing the sways is a lot off effort on the F30.I'll be slowly adjusting the stiffness and see how it rides, currently am on 10 Front 12 Rear, feels pretty good. On the firm side and not crashy, unless the roads are very very bad.. |
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10-21-2020, 07:53 AM | #10 | |
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10-21-2020, 08:31 AM | #11 | |
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Current : F31 330sD, remapped, Ohlins Road & Track, Millway camber plates, Quaife LSD, Stoptech brakes + Pagid RSL1 pads all round, Weichers front strut brace, Eibach front & rear anti-roll bars, Michelin MP4S.
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10-22-2020, 07:44 AM | #12 | |
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Subframe bushes made a material difference to NVH, but also really tightened up the rear end under power. Noticeably better traction. The diff bushes I'm pretty sure just added NVH without much else that I could notice. |
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