Upgrade path for a track focused 135 N54

[d k]

Hello

Looking for some suspension info here....

I would like to know what the brain trust here recommends for a 400-450 hp track focused car?

I am planning on doing the 1M body conversion in the front for tire fitment and havent decided what I will do in the rear yet.

My question is should I swap over everything to M3 style or keep as much of the stock suspension as possible and upgrade whatever parts necessary?

One of the things I will definitely do is a proper clutch lsd.
I dont know if its more cost effective and beneficial to go with M3 diff (and subframe) or get an auto 335 diff and just do an lsd (osg, mfactory).

Is it worth changing over the lca's?

One benefit would be coilover selection.
There are a lot more proper, track worthy coilovers available in the M3 fitment than the 135.

Am I wrong?

I would like to hear some thoughts...

David

[HP Autosport]

Any of the high end offerings from JRZ, MCS, Moton also have applications from the 135i. Typically they use the same front strut housing with the M3 using adaptor sleeves for the larger diameter spindle. You will need to convert the rear to the E9x M3 rear lower camber links to use the most of the higher end coilovers since no one I know makes the rear damper pin to pin mount. As a matter of fact we just help set up a complete MCS two way external reservoir system for a customer in NY. See photo.

You will definitely want to upgrade to all M3 control arm bits or more. If it's a track focused car and you are not opposed to monoballs, SPL has a full line of suspension components.

As for the LSD, have Dan at Diffsonline build you a 2 or 3 clutch custom diff.

Clutch master and a couple of others have upgraded clutches with more clamping force to handle the power output.

Feel free to PM, email or call us to discuss anything you need in detail.

[bNks334]

Originally Posted by d k

Hello

Looking for some suspension info here....

I would like to know what the brain trust here recommends for a 400-450 hp track focused car?

I am planning on doing the 1M body conversion in the front for tire fitment and havent decided what I will do in the rear yet.

My question is should I swap over everything to M3 style or keep as much of the stock suspension as possible and upgrade whatever parts necessary?

One of the things I will definitely do is a proper clutch lsd.
I dont know if its more cost effective and beneficial to go with M3 diff (and subframe) or get an auto 335 diff and just do an lsd (osg, mfactory).

Is it worth changing over the lca's?

One benefit would be coilover selection.
There are a lot more proper, track worthy coilovers available in the M3 fitment than the 135.

Am I wrong?

I would like to hear some thoughts...

David

Something I am learning is that the front wheel base is already wider than the rear. I have 255 square with aggressive tire fitments (17x9 ET25 front and ET45 rear) and my front tire track is over 2" wider than the rear. If anything, I'd want to do a rear conversion to square things back up. All the tire fitment in the rear is INBOARD. A widebody front end while keeping the stock rear would make the imbalance even worse.

The rest has been beat to death in threads here... search. Every bushing in the car is too soft and so is the suspension. An LSD is a must. The e-diff will slow you down on the track and the car makes too much power to run an open differential (code the e-diff off).

[d k]

Originally Posted by bNks334

Something I am learning is that the front wheel base is already wider than the rear. I have 255 square with aggressive tire fitments (17x9 ET25 front and ET45 rear) and my front tire track is over 2" wider than the rear. If anything, I'd want to do a rear conversion to square things back up. All the tire fitment in the rear is INBOARD. A widebody front end while keeping the stock rear would make the imbalance even worse.

The rest has been beat to death in threads here... search. Every bushing in the car is too soft and so is the suspension. An LSD is a must. The e-diff will slow you down on the track and the car makes too much power to run an open differential (code the e-diff off).

I have been searching....like crazy

Im not too worried about the track width difference as much as I am worried about getting grip from the front.
If anything, the imbalance is towards understeer. So getting a 275 square is a priority. Also I plan on doing the rear as well, I just dont know how..

[bNks334]

Originally Posted by d k

I have been searching....like crazy

Im not too worried about the track width difference as much as I am worried about getting grip from the front.
If anything, the imbalance is towards understeer. So getting a 275 square is a priority. Also I plan on doing the rear as well, I just dont know how..

Yeah that's what I am trying to tell you... you can get 275 square with a wide body front end, but just because you have 275 square doesn't mean the car is actually neutral or the wheel setup is actually square... The will still be heavily under-steer biased since the rear width will be significantly shorter than the front width... all the rear tire clearance is inboard (very high offsets to fit 275). You'd have to run some really low rear offset tires and pull/shave your rear fenders to get a true square 275 setup. To fit 9.5" wheels and 275's out back you need around ET58. The same 9.5/275 setup up front would would need ET30. That right there is a 28mm per side difference (56mm total = 2.3" wider front track than rear). A wide body kit up front would allow you to bring those front wheels out even wider (lower offset)...

It's just something I wanted to throw out there for you to consider when setting the car up. The rear wheelbase, that puts all the power down, could use more help than the front. Hence why staggered setups actually work pretty well on a 1 series.

[d k]

So, with all that - is it wothwhile and beneficial to switch everything over to the M3 arms/subframe/spindles, or is it possible to get the same out of an upgraded 135 setup?

Are there any geometry differences going with a M3 setup?