"Downgrading" Brakes to 335i

[volumex]

Hey guys

So I have a 335i and I'm weighing up costs and feasibility to upgrade the rear end specifically around getting a fkn LSD.

My 2 options are:
1. Buy an e90 M3 rear subframe for $3500 with control arms, diff, axles, hubs
2. Buy an aftermarket LSD for $1600 and then pay $1000 to upgrade my existing diff, then pay the ~$1000+ extra on m3 control arms and aftermarket rear toe arms, etc

Now I am not running extreme power nor do I want to. I intend to redo all the bushes in the subframe when I buy it, blah blah blah.

Basically, the cost will increase drastically if I need to buy E90 m3 brakes along with it. I want to know if I can just use my existing 335i brakes on the rear subframe spindles. Will a 335i disc bolt on?

Then secondly, obviously as the front end I'll just do a standard m3 control arm upgrade so the front brakes will be fine, but can anyone shed any light on whether suspension will be affected? Can I use the same coilover kit with a rear subframe but a 335i front end? Will I have to change the wheel carriers at the front in order to use m3 aftermarket suspension? If thats the case then does the front 335i sway bars no longer fit and will I have to upgrade to M3 specific sway bars?

Definitely a few questions in there, but $2600 for a mfactory diff and then like $700 for rear adjustable toe arms.. why not just do the m3 conversion and polyurethane the bushes.

I am familiar that the tailshaft needs to be modified for this conversion also, but yeah I just don't want to bother with the brakes unless it's an upgrade to f80 (which I have read the thread for here also)

Any input, advice, insults, comments, you name it feel free

[bbnks2]

Originally Posted by volumex

Hey guys. So I have a 335i and I'm weighing up costs and feasibility to upgrade the rear end specifically around getting a fkn LSD.

This is a loaded post...

Originally Posted by volumex

My 2 options are:
1. Buy an e90 M3 rear subframe for $3500 with control arms, diff, axles, hubs

If you're paying more than $1700 for a complete M3 rear-end you're overpaying. Maybe another $200 for a m3 driveshaft max... Definitely wouldn't pay more than $2,000 all-in. Then add another $200 to have the driveshaft chopped and welded to length. Call it $2300 all-in.

Originally Posted by volumex

2. Buy an aftermarket LSD for $1600 and then pay $1000 to upgrade my existing diff, then pay the ~$1000+ extra on m3 control arms and aftermarket rear toe arms, etc

If all you do is straight lines stuff you can put an mfactory helical into your 335/135 pumpkin for $1000 if you can do it yourself (if it's a bolted ring gear). If you do road course or auto-x definitely pony up for a clutch type diff. The M3 diff will be worlds better if this is the type of driving you do.

The M3 rear subframe has a lot of benefits but more for road course. The subframe is beefier, the axels are beefier, the diff has better cooling and is more robust even if you want to put an aftermarket LSD into it later...

However, option two is a strong consideration. If you're just doing straight line stuff then all you need is a cheap helical and some control arms.

Bushings are a moot point because the rear subframe bushing in the M3 subframe suck too. Go to delrin or solid. The control arm bushings are a whole thread in itself... you can google about that.

Originally Posted by volumex

Now I am not running extreme power nor do I want to. I intend to redo all the bushes in the subframe when I buy it, blah blah blah.

So sounds like you don't really need the beefier axels of the M3 rea-end. Again, what is the purpose of the build?

Originally Posted by volumex

Basically, the cost will increase drastically if I need to buy E90 m3 brakes along with it. I want to know if I can just use my existing 335i brakes on the rear subframe spindles. Will a 335i disc bolt on?

The M3 rear-end should come with brakes. If not, The calipers are dirt cheap but rotors are big money. I just spent $1,000 replacing mine. Bought from FCPEuro.

No, the 335i calipers will not bolt on to the M3 spindles. There are very few inexpensive options for upgrading M3 brakes as well. They are a floating caliper so Plan to buy the brass bushings for the guide pins to tighten up the slop of the stock rubber guide pins.

Originally Posted by volumex

Then secondly, obviously as the front end I'll just do a standard m3 control arm upgrade so the front brakes will be fine, but can anyone shed any light on whether suspension will be affected?

In the front? No. Not unless you put in the front M3 spindles... then you'll need the convert your coilovers to M3. Most coilover companies will sell you the bottom sleeves to convert into M3 style mount.

Originally Posted by volumex

Can I use the same coilover kit with a rear subframe but a 335i front end?

If you don't change anything on the front end then of course you can continue to sue the same suspension in the front lol...

Originally Posted by volumex

Will I have to change the wheel carriers at the front in order to use m3 aftermarket suspension?

Yes, if you buy M3 style coilovers then the fronts will not work with your 335i spindles. You would need to convert to M3 front spindles or order coilovers in a mismatched set with 335i front fitment and M3 rear fitment...

If you use the M3 rear-end you can use your current coilovers though... You do NOT need to convert to M3 coilovers. All you need to do is swap back in your rear lower control arm that the strut mounts to. They are interchangeable. The m3 arm IS lighter so it sucks having to ditch it but the strut mounts differently so to save money you can just use the 335i lower arm.

Originally Posted by volumex

If thats the case then does the front 335i sway bars no longer fit and will I have to upgrade to M3 specific sway bars?

Sway bar fitment is not affected but the M3 rear sway is much stiffer than the 335i/135i's... You will want to upgrade to the E92 M3 front sway or maybe even the E93 front sway to keep the car balanced.

Originally Posted by volumex

Definitely a few questions in there, but $2600 for a mfactory diff and then like $700 for rear adjustable toe arms.. why not just do the m3 conversion and polyurethane the bushes.

I think there is definitely cost savings in buying the M3 rear-end. The M3 diff is great. Of course I put in Condor sumbframe and diff bushings. That expense stays the same. AS stated above, you can do all sorts of stuff with the control arms... that's a whole other thread.

Originally Posted by volumex

I am familiar that the tailshaft needs to be modified for this conversion also, but yeah I just don't want to bother with the brakes unless it's an upgrade to f80 (which I have read the thread for here also)

I believe the F80 brake swap would be superior to M3 brakes but I don't know if anyone made a bracket to adapt them to an M3. So, that would be another perk to keeping the 335i rear-end. Like said above, M3 brake upgrades are costly. Most are going straight to a Stoptech kit. there was a group buy for some retrofit kit but it looks like most everyone got scammed except for the first few people.

And again, what is the purpose of the car? Are you running faster lap times than a spec 46 at your local roadcourse? because.. those cars have smaller/shittier brakes than a 335i... are you doing it because you need it? because you want the bling? or because you're actually building a racecar and you think you need better brakes? Brake ducts and a good pad is all you really need on any of these cars until you're hot lapping at an advanced level and trying to drop those last few tenths of a second off your lap times.

[volumex]

Appreciate the response mate and I should clarify a couple of things

Firstly with currency I should have specified this is AUD.

We don't have access to cheap wrecked M3's here, and they're just not cheap at all. For $3500 you'd be getting the subframe, axles, diff, control arms, hubs and that's about it. I know the axles are overkill, but they'd be nice to have.

Brakes, yeah I'm not tracking so I don't care for stronger brakes. The stock 335i ones are more than enough hence wanting to use them and not shell out for the M3 brakes.

An MFactory LSD internal is $1600 alone over here, thats not including anything else. Maybe doing the swap myself is feasible? A lot of people have recommended getting professionals to do it. Maybe I'll look into it a bit more.

If you use the M3 rear-end you can use your current coilovers though... You do NOT need to convert to M3 coilovers. All you need to do is swap back in your rear lower control arm that the strut mounts to. They are interchangeable. The m3 arm IS lighter so it sucks having to ditch it but the strut mounts differently so to save money you can just use the 335i lower arm.

This is very useful info. Thank you so much for this.

I think also I failed to explain is that if I do need to upgrade to M3 (e90) brakes, I'd have to swap out the front wheel carriers. Therefore M3 suspension will need to be used, and my question is will the sway bar be affected by this? Would I need an M3 based one instead of just the e90/335i. EDIT: Wait sorry read your post again, you said swaybar fitment is not affected. This is also very good info

However, keeping the 335i lower control arm makes much more sense. I can just use an aftermarket e90 swaybar and m3 control arms in the front and be done with that, so the last piece of the puzzle is how do I get 335i discs and calipers into the rear end. Or what is the best brake kit/combination to upgrade to that'll fit a 335i front end and a m3 rear end.

Appreciate the response though mate made things much clearer

[bbnks2]

Originally Posted by volumex

Appreciate the response mate and I should clarify a couple of things

Firstly with currency I should have specified this is AUD.

We don't have access to cheap wrecked M3's here, and they're just not cheap at all. For $3500 you'd be getting the subframe, axles, diff, control arms, hubs and that's about it. I know the axles are overkill, but they'd be nice to have.

Brakes, yeah I'm not tracking so I don't care for stronger brakes. The stock 335i ones are more than enough hence wanting to use them and not shell out for the M3 brakes.

An MFactory LSD internal is $1600 alone over here, thats not including anything else. Maybe doing the swap myself is feasible? A lot of people have recommended getting professionals to do it. Maybe I'll look into it a bit more.



This is very useful info. Thank you so much for this.

I think also I failed to explain is that if I do need to upgrade to M3 (e90) brakes, I'd have to swap out the front wheel carriers. Therefore M3 suspension will need to be used, and my question is will the sway bar be affected by this? Would I need an M3 based one instead of just the e90/335i. EDIT: Wait sorry read your post again, you said swaybar fitment is not affected. This is also very good info

However, keeping the 335i lower control arm makes much more sense. I can just use an aftermarket e90 swaybar and m3 control arms in the front and be done with that, so the last piece of the puzzle is how do I get 335i discs and calipers into the rear end. Or what is the best brake kit/combination to upgrade to that'll fit a 335i front end and a m3 rear end.

Appreciate the response though mate made things much clearer

The brake balance is fine with just the rear. You dont HAVE TO do the front brakes and knuckles... you HAVE TO used M3 brakes in the back. No one is making custom caliper brackets to fit 335i calipers to an M3 lol

[volumex]

Originally Posted by bbnks2

The brake balance is fine with just the rear. You dont HAVE TO do the front brakes and knuckles... you HAVE TO used M3 brakes in the back. No one is making custom caliper brackets to fit 335i calipers to an M3 lol

Sorry bro my OCD won't tolerate mismatched brakes

[DR-JEKL]

Ive done full M3 driveline retrofit, gets expensive as you need m3 shocks/springs (or in my case ohlins coilovers) then brake pedal is mushy need the m3 master cylinder also...

Know guys who have done M3 diff subframe and just used m3arms etc but didnt install the m3 uprights hubs. (thats the cheaper option)

few of us in Australia have done the swap if you search