Rehabbing my busted stock suspension -- ST coilovers from suspension source were cheaper (at $850 shipped) than replacing bad stock shocks. Went ahead and got new tie rods, front and rear droplinks and ball joints too.

People talk good things about rear sways for handling, so I got one of those too.

Any idea of how to gauge whether the stock strut topmounts need to be replaced while I'm in there?

 

Only if you see the towers mushrooming then yes you might have done troubles. But I'd also recommend m7 strut tower defenders and h-sport rear control arms.

Enjoy!

 

maybe a dumb question, but how what does mushrooming look like? any distortion in the rubber part?

 

I heard you need wheel spacers (at least 5mm) with the ST Coilovers. Is this still the case?

 

When the top strut mounts mushroom they literally have a mushroom shape to them. The upper strut mount bolts will also stick out instead of point straight up through the mount. I had this happen on my E46. The shop had to hammer the strut mounts back into shape.

My R56 doesn't have strut defenders and the strut mounts look fine at 44k miles with a lowered suspension.

 

Here is the visual:

a

 

You did not mention how many miles you have on your old suspension, or where you live, but assuming more than 35K miles (when one my front shocks failed and dented the upper strut tower), you are likely to have at least some mushrooming of the upper strut mounts by now. The rubber enclosure may, or may not be, cracked - easy to check when you have the strut assembly out of the car.

If the rubber is cracked - replace the strut mounts.
If the strut tower is mushroomed (see video link in another reply), then the strut mount plate is mushroomed as well - replace the strut mounts.
If neither of the above conditions exist, check that the bearings are spinning freely, add some lube, and you can re-install the strut mounts on your new suspension.

The other consideration in replacing the upper strut mounts is camber management. If you intend to lower the car, you will pickup more negative camber. That may, or may not, be what you want. For autoXing and DEs, more negative camber helps with the turn it. At the expense of accelerated inner tire shoulder wear and some straight line stability. If you intend to keep the car a 90+% daily driver, you will want to dial some of the additional negative camber back out. To do that, you need adjustable camber plates. There are many to choose from, and selecting one deserves a thread of its own (can't go wrong with either Vorshlag or Hotchkis), so do your homework!

If you lower the car "enough" to pickup negative camber on front axle, you will do the same on the rear axle as well. If you like it - great, it's free. If you don't (inside shoulder tire wear), you will need adjustable rear control arms to dial it back out.

If you change suspension geometry, you will want to get the car competently aligned (i.e.: not at the cheapest tire shop) as well.

Or, resist slamming the car too much, and save yourself the trouble and expense of dialing out unwelcome negative camber all around.

Hope this helps,
a

 

Thanks for all the great info! The chassis has 163k on it, with 10k so far in NYC. It came from Connecticut.

I am going to inspect it this weekend and will order new mounts if needed.

I'm planning to get the car aligned after I put 3-500 miles on to "settle" the springs per the vendor's instructions. I'll be doing it at RCT performance in Queens, who do alignments on my Porsche.

 

Camber on the front McPherson struts does not change no matter how much you lower. You will need camber plates to change camber.

 

Sorry, you are wrong.
The opposite is the case - McPherson struts are some of the worst offenders for camber and toe change during compression (vs. multi-link suspension), but most car manufacturers employ them for low-cost and ease of packaging reasons.

It's simple geometry.
If you visualize the what happens to the strut assembly as it shortens (either under load, or due to shorter springs), the wheel hub angle to the road will inevitable pickup negative camber. At least up until the angle of the strut to lower control arm crosses 90 degrees (it starts at below 90 degrees by design).

Often times that's good - you want more negative camber to help with outer wheel traction during a turn. As the weight transfers to the outside corners and the car "leans away from the turn", extra negative camber compensates to maximize tire contact patch with the pavement.
Sometimes that's bad - significant camber and toe change as you hit a bump or road dip at speed can introduce unintended directional change if the dip is not perfectly perpendicular to the direction of travel.

Similarly, toe and caster are also changed, but that's a conversation for another day.

To visualize the above (if you've never taken suspension apart), explore the following illustration:
a

 

Disagree. On MINIs, the static camber gain from lowering at the front axle is very little. There is certainly some change due to the camber curve on Mac struts, but the amount you get from just the lower arm is close to none.

From lowering my car around 2 inches, I ended up with -0.9 degrees up front, -3 degrees at the rear. Camber plates and adjustable rear controls arms were in order.