Suspension upgrade options: 125 coupe non M-sport

[ozimmer]

I have a stock 2010 125i coupe which I use as a daily driver & for weekend cruises, but is never likely to see track use. As a "mature" driver, I want to err on the side of compliance & comfort over outright performance. My goals are to reduce skittishness (esp. the rear end) over minor bumps, and a modest drop of around 20-25mm.

With the current non-sport suspension the wheel centre to fender lip distances are 365mm(F) and 360mm(R) creating a large gap of around 50mm at the top of the tyre to underside of the fender/ mudguard. Tyres are 17" RFT's (205/50 front and 225/45 rear). While I intend to ditch the RFT's at some time in future, the current tyres still have plenty of tread, so I am looking for an upgrade that can work with RFT and non-RFT's. My budget rules out coilovers or the BMW perf suspension kit.

Having searched many threads on suspension upgrades, I have shortlisted several permutations of springs & dampers against a budget of ~A$1000 (parts only):

1. Eibach pro or H&R OE Sport springs with Koni yellows or FSD.
2. Above springs with Bilstein dampers (e.g.., Bilstein B12 pro-kit with Eibach springs).
3. BMW M-sport springs (OE springs on sport 125/ 135) with any of above dampers.
4. BMW performance springs with above dampers (but may exceed my budget).

My concern with the Eibach pro springs is the drop - notionally 1.2" (~30mm), but I have seen pics on this forum of cars with little or no gap at the top of the front tyre, which is lower than I want to go. I understand the other springs I mentioned above should offer a drop of 15-25mm against the non-sport springs (although I stand to be corrected).

Also, my non-sport 125 has no rear anti-roll bar. Is an A/R bar essential given my goals, or should I focus on springs/ dampers first?

In particular, as anyone with the OE M-sport springs upgraded the dampers only - option 3 above?

thanks in advance for feedback.

[John_01]

It sounds like the BMW performance suspension would be a good match for your requirements. However its not the best value for money compared to buying springs and dampers separately. Since our Australian roads aren't great, you will probably want to get rid of the runflat tires quite soon after making the change.

Did you see this thread showing the Eibach pro kit and H&R OE sport?
http://www.1addicts.com/forums/showthread.php?t=343630

Adding anti roll bars is a very good idea for a comfort oriented setup because it adds body control with almost no penalty in ride quality. The front bar is simple and cheap to install, but unfortunately the rear bar installation is a much bigger job. If you just want to install the front bar it won't be hard to find a used M-sport front bar because so many people have upgraded. It may be possible to go straight for the E92 M3 front bar, but I just don't know if you will notice any issues due to being without any rear bar.

[ozimmer]

many thanks for your feedback John

re: the thread showing the Eibach pro kit and H&R OE sport:
http://www.1addicts.com/forums/showthread.php?t=343630

This reinforces comments elsewhere that the H&R springs create a more raked appearance - the degree of which may also be related to the dampers. Your comments about A/R bars make sense ... I am thinking that may be a 2nd / 3rd stage after the springs & dampers and replacing the run flats.

cheers

[TS135i]

Surely someone in OZ has the complete M-sport suspension kit sitting in their garage. That along with an E92 FSB rear 135i RSB might be what you are looking for, you could even keep the RFT's.

[froop]

I'm not sure if a set if dampers and springs will completely remove the rear end skittishness. Most people say that it is due to the soft subframe bushings. I'd suggest also addressing those at the same time. Probably powerflex or whiteline inserts to fit within your budget. I think the whitelines can even be purchased within Australia and they're very cheap. Also DIY install.

Let me know if you're planning on getting a set. I've been meaning to get one for my E88 lol.

http://www.eziautoparts.com.au/cross...rrencyC%5D=AUD

[John_01]

froop makes a really good point. Its hard to know what you mean by skittishness, but IMO you will probably still feel underwhelmed with the cars roadholding unless you do something about the wobbly stock rear subframe bushings. The problem caused is the rear axle tends to steer in weird directions due to cornering and braking forces. I have the genuine BMW M3 rear subframe bushings fitted to my 135i as an upgrade, but that required the entire rear end components to be removed at a significant cost. Installing inserts for the existing bushings should cost a lot less. It be possible to install the rear sway bar at the same time as the inserts, but I'm not 100% sure.

[froop]

Originally Posted by John_01

froop makes a really good point. Its hard to know what you mean by skittishness, but IMO you will probably still feel underwhelmed with the cars roadholding unless you do something about the wobbly stock rear subframe bushings. The problem caused is the rear axle tends to steer in weird directions due to cornering and braking forces. I have the genuine BMW M3 rear subframe bushings fitted to my 135i as an upgrade, but that required the entire rear end components to be removed at a significant cost. Installing inserts for the existing bushings should cost a lot less. It be possible to install the rear sway bar at the same time as the inserts, but I'm not 100% sure.

Rear sway requires dropping of the rear subframe unfortunately so if he's going to do rear sways may as well do M3 bushings. Expensive job though.

[ozimmer]

Thanks for the suggestions guys.

I've seen comments elsewhere about changing rear subframe bushings, but given the amount of labour to do so, I was / am hoping to make an improvement without that amount of work.

re: "skittishness": I find the rear loses traction easily over minor bumps, eg paving repairs and cats eyes, even under modest acceleration in a straight line. I've played around with rear tyre pressures between ~32 to 40 psi and yet to find a good setting. I appreciate the RFT's may be more blame than the suspension. Either way, it does not provide as much confidence compared to my previous Golf GTI on the same size tyres (225/45 17).

If anyone in Sydney has M-sport or (even better, BMW performance) springs & dampers in good condition for sale, I am interested.

[froop]

I'll actually be doing a complete suspension haul over within the next month or so, so mine might actually be available haha.

To be honest though, other than for the drop, I'm not entirely sure whether it will provide the improved performance you are looking for. I would seriously suggest getting some whiteline or powerflex inserts for the rear subframe bushings. They just push into the stock bushings and don't require that the whole subframe be dropped. I think it's possible to install them without even lowering the subframe from memory.

Once you do that, if it's still skittish, then consider upgrading the shocks and springs.

If you want to go down that route we can try DIY install it together as I've been meaning to get a set for the E88.

As for the RFTs, if you're set on staying with them, consider eventually getting PZero RFTs. They phenomenally better than the Bridgestone RE050A's in terms of both grip and comfort levels.

[John_01]

Firmer springs and dampers will definitely help the body control and make the car more precise. I expect the stiffened subframe bushings to be a good combination with firmer and lower suspension. The two aspects work together in the way the car is affected by cornering loads. You will end up with a car that is more predictable and steers more accurately. In an ideal situation it would nice to have upgraded anti roll bars as well, but it will probably depend on whether you are flexible with the budget.

[kobeballer96]

i have H&R sport springs on my M sport dampers and the ride isn't bad at all, pretty steady on autobahn speeds going over 250km, and i track my car onces in a while. Its my DD.

[ozimmer]

Thanks for the feedback everyone...

Kobeballer96: your set-up of H&R sport springs (OE Sport?) + M-sport dampers could be a good option. While the term "drop" is relative, do you have photo, or have you measured the wheel centre to fender distances F & R?

Froop: thanks for the link to the Nolathane bushing kits which I reviewed. I'll also investigate the Whiteline & powerflex options you suggested. In the meantime, I am happy to give you a hand with your suspension upgrade/ overhaul - if you seek assistance.

[ozimmer]

Resurrecting this thread, as I have now had BMW performance springs (thanks UR25IO) with Bilstein B8 dampers installed by Advan last week. Over Christmas I also fitted whiteline inserts in the rear subframe bushes, using the excellent DIY elsewhere on this forum. Having now been for several drives, the changes are positive as long as the roads are mostly smooth-ish. The car feels tauter and rolls less, as was expected. My confidence on sweeping curves is higher, as it quickly adopts a set and points true. While I can induce some axle tramp & "skipping" over bumps if I try, it recovers sooner with far less of the TC flashing light effects from the dash than before.

Ride is overall better than I expected - more than acceptable on most roads around Sydney that I use regularly, even over speed humps. Roads with frequent patched sections or undulations induce a mild jiggling which could become annoying if those roads make up a large % of your driving. In any case, I have experienced no "crashiness" or bottoming, even over the worst bumps. Drop is around 20mm compared to the non M-sport suspension, which is close to what I sought. Curiously the RH front is about 6-7mm lower than the LHF, which I will monitor as I don't recall it being noticeably different before. I still have reasonable ground clearance, so it passes the driveway test without scraping the exhaust tips.

If cost was no issue, I would have gone with the complete BMW PS package and M3 suspension bits, but this was not something I could justify (to myself or to my better half).

Next step may be to install a bigger front sway bar … and of course replace the RFT's when they wear down, with regular tyres. In the meantime, I intend to rack up the km on my favourite driving roads.

[John_01]

Good to hear it worked out. Bilsteins and PS springs are a quality option. A few people have commented the B8s are firm, but perhaps its just what you need for good handling. A front sway bar seems a logical upgrade, but I'd probably be tempted to spend the money on tires first. I think it would help both comfort and performance.

[ozimmer]

thanks John (& others who offered advice) …. you're probably right about the tyres as the next logical step, but the scottish part in me can't justify ditching half worn tyres, even if they are RFTs. Perhaps some hard cornering will shorten their life.

ps: a pic of the rear suspension attached. Colour coordinated spring, damper body and whiteline inserts was not intentional, but an unexpected benefit!

[TheSt|G]

You really should ditch the RFTs as soon as possible. They are simply horrid from a ride quality, performance, noise, and general comfort perspective.