Upgrade to M3 suspension | Worth It?

I'm about to purchase a ZHP here in the next month or so and am planning out upgrades to the car. For sure an S54 will be installed in the first 12 months. Before I do that, I want to make sure the suspension and braking are up to the task of handling the extra power and speed. I know a full M3 suspension can be installed and that is definitely an option. However, I do want to make sure that is the best decision for my build. The goal is to have the suspension be as light as possible (M3 suspension heavier?) and adjustable as necessary. Regardless of using the ZHP or M3 suspension I am likely to install Ohlins or KW to have something good for both high performance driving events and the street. Brakes would be upgraded as well. Again the goal is lightweight and whatever is needed to slow down the car from 100+mph. Don't want overkill and that usually means heavy brakes and higher unsprung weight. So a good brake kit using the stock ZHP setup is fine if that works.

So should I do the extra expense of buying and installing the M3 suspension knowing that it will need a refresh, etc. Or keep the ZHP suspension and just upgrade from there. Key point - will the M3 differential work with a stock ZHP rear end? If not, then that might answer my question. But then I could always install a limited slip upgrade from Quaife. Again looking for less weight but enough to handle the S54 power.

Thoughts?

No, the M3 diff does not bolt in to the ZHP subframe. You'd have to swap the entire M3 rear end.

If you're doing a street/HPDE hybrid, you can stick with the OEM M3(edit: Z4M) FCABs, maybe add a strut bar, if keeping the ZHP rear, swap out the lower rubber bushing with a ball joint, run aluminum subframe bushings and go have fun.

There aren't that many places to save unsprung weight, the big one being lightweight wheels.

I'll let some one else chime in on the brakes.

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Originally Posted by DeathTrap

No, the M3 diff does not bolt in to the ZHP subframe. You'd have to swap the entire M3 rear end.

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Thanks for the confirmation. Looks like if you keep the ZHP subframe you are stuck doing a differential upgrade with an aftermarket company. That can be a plus as then you can change gearing, but it is expensive. But you do get a new differential vs who knows how many miles on a used M3 one.

Wheels will definitely be one of the first places to upgrade. Might even go down to 17s to save on weight.

Bimmerworld is confident that a pad and rotor upgrade will be enough to handle the extra speed/power. Just chatted with them today. Still open to other suggestions.

No you don't need M3 suspension. If you're going to upgrade to coils or whatever later, that will be enough. In fact, for some suspension kits, they only make an M3 version and just apply it to the non-m. I'm pretty sure the brakes will be able to stand up to it. I think the rotor size for the M3 (regular M3, not CSL/ZCP) is nearly the same size. Just change compounds to reduce fade.