[Drivaar]

I was wondering if anyone could explain what makes a shock "good"...

Does it mean it absorbs road irregularities better? Lasts longer?

In many cases, people seem to be switching to "better" shocks that are actually stiffer than the OEM sport shocks... which means ride is going to get worse, no?

Advice is much appreciated! Thank you.

[Stuart@BMRAutowerkes]

Conceptually speaking, a good shock is one that performs it's intended purpose well. OP, what's the intended purpose?

Most people change shocks with the aim of giving the car better handling because the shock absorber will absorb the shift in weight when cornering, or to better suit lowered springs. An inherent tradeoff in this is that it usually means a stiffer shock, thereby comfort is reduced.

However not all 'sports' shocks are uncomfortable, and that is usually what people would regard as a good shock. We all have our own preferences and tastes for comfort levels but there's a general consensus over what is acceptable for daily driving and a 'good' shock would be deemed so.

Consider perhaps the Koni FSD shocks, quite widely regarded as improving handling without a decrease in comfort, in some cases comfort is improved. There is a review of it on tirerack here

However, the Koni FSD for example isn't as 'good' as the Koni sport dampers if you are looking for even better handling (race track purposes etc)

As for what makes a good shock in terms of construction, materials, fluid viscousity, design etc, I'm not too sure and that is something I am wondering, particularly with reference to coilovers.

[HighlandPete]

I'm thinking in a similar way, are we talking performance and/or quality of build/manufacture.

Shocks and damping performance is a compromise, based on what ride/handling balance we are looking for. Good to one guy, is poor to another.

Also there is a lot of personal perceptions as to what is good and bad, many want a hard sporty feel, so a simply change to a 'sporty' set of shocks, (dampers in the UK).

But unless the damping is matched to the right springs and other suspension components and settings, could be a very poor riding/handling vehicle. So even a quality product could be a poor performing shock, on the wrong setup.

Also remember a sporty damper, even with matched springs, doesn't always equate to a faster road car point to point. May just feel faster.

Really we should first decide what we want from a shock, set the priorities, comfort, handling, the condition of the roads we drive, etc. Some designs and damping valving/settings fit better in the middle ground than others.

HighlandPete

[Drivaar]

Right... the question is, over time as shocks deteriorate, does the ride comfort decrease? Seems to me that for the most part, the shocks become softer, so ride comfort actually increases while handling should decrease?

Thanks bmroxm5 for the review. I didn't realize TireRack did reviews for that stuff too.

I wish the TireRack reviews actually compared replacement shocks with the BMW sport package instead of non-sport package! (That would seem to make more sense...)

[michaelthepsycho]

A good shock in terms of performance is one that is stiff enough to keep your tires on the ground while not too stiff to be upset by a mid-corner bump, thus losing grip. They have to be calibrated according to the smoothness / bumpiness of the track. Stiffer inspires more confidence from lack of body roll but does not equate to better road-holding.

[captainaudio]

Originally Posted by michaelthepsycho

A good shock in terms of performance is one that is stiff enough to keep your tires on the ground while not too stiff to be upset by a mid-corner bump, thus losing grip. They have to be calibrated according to the smoothness / bumpiness of the track. Stiffer inspires more confidence from lack of body roll but does not equate to better road-holding.

+1

There is a common misconception that the stiffer the suspension the better the handling and that comfort and performance are mutually exclusive. It is the job of the shocks (dampers is really a better term) to keep the springs from oscillating (think of the floaty suspension in older large american cars) and to keep the contact patches in contact with the road surface (that is why they are called contact patches).

I recently swapped out the stock sport suspension shocks for Koni FSDs and was able to improve both handling and comfort. Suspension tuning can be somewhat of a black art and if you don't know what you are doing you can cause more harm than good.

Car magazines and companies like Tire Rack test various aftermarket setups and publish the results. Keep in mind that race track tend to be smoother than public roads and what works on a track may n0ot be the best setup for a daily driver (and vice versa).

Ride quality will not necessarily increase as shocks wear out as suspensions are desgned to work with properly calibrated shocks, Shocks can "freeze" as they wear out and not allow proper suspension travel and if they become too soft the suspension can hit the bump stops which will equate to a very harsh ride.

CA

[Drivaar]

Thank you all for the great responses!

One question though: seems like fundamentally, ride quality and handling MUST be at odds, since ride quality means there is more give, and better handling means the shock is pushing back harder on the road to keep the tire planted.

That said, I like the observation the Koni FSD folks have made, which is that in a straight line, for the most part, you want the shocks to be softer for comfort.

I think some of the high-end cars with electromagnetic variable dampers constantly make this adjustment... (I've read it feels sterile though...)

[HighlandPete]

Originally Posted by Drivaar

Thank you all for the great responses!

One question though: seems like fundamentally, ride quality and handling MUST be at odds, since ride quality means there is more give, and better handling means the shock is pushing back harder on the road to keep the tire planted.

That said, I like the observation the Koni FSD folks have made, which is that in a straight line, for the most part, you want the shocks to be softer for comfort.

I think some of the high-end cars with electromagnetic variable dampers constantly make this adjustment... (I've read it feels sterile though...)

The Adaptive Drive/Variable Damping Control in the latest 5-series is pretty good, switchable on the fly, but it is not as predictable as a passive damping setup. Least we can say it is 'different'.

You are right about ride and handling being at odds, so compromises must be included. The Koni FSD concept, (Mercedes use a similar damper in their passive Agility Control package) does go a long way to overlap the two areas of primary and secondary ride qualities. I use the Koni FSD in my 330d wagon, and it makes a far better balance of handling and comfort.

Worth looking at the linked thread, over in our UK section. Kevin Bird is a highly respected tuner in the UK, includes getting a 'better' suspension system.

http://www.e90post.com/forums/showthread.php?t=401537

Note the attached artical in BMWCar magazine. I totally agree with much of the reasoning, makes so much sense to engineers, like myself.

HighlandPete

[Tag]

Originally Posted by Drivaar

One question though: seems like fundamentally, ride quality and handling MUST be at odds, since ride quality means there is more give, and better handling means the shock is pushing back harder on the road to keep the tire planted.

Shocks don't push or pull for that matter, they provide resistance AKA dampening to the compression and rebound of the springs.

[stressdoc]

You want to keep maximum friction from your tires. Shocks/dampers buffer the movement of the different masses -- sprung and unsprung.

Quality shocks in a matched system with the right springs, sway bars, bushings and tires makes a world of difference.

My experience with the 335 has been a bit of a love/hate relationship. The car is an amazing mix of luxury tourer and exciting performance car. The N54 engine in original stock form has perhaps the finest power curve of any affordable car ever. The suspension, however, is a bit of an odd duck. IMO there are two serious weak links: open differential and RFTs. The suspension is designed around those compromises, and there are no cheap or easy solutions. It is not enough to just swap out for extreme perf non-rfts and a Quaife. The RFTs require soft bushings (and dampers) to improve ride quality, but compromise suspension geometry under stress. Open differential requires soft rear sway. The basic goal is to emulate the suspension of the M3, which is designed around an LSD and non-rfts, but with better control of the N54's low end torque. And perhaps more consideration of a comfortable daily driver experience.

The system:
1) Quaife or wavetrac LSD
2) Extreme perf non-rft tires; Yoko advan neova AD08, Dunlop direzza Z1, Bstone RE11.
3) Quality coilovers or matched damper spring set. My choice: AST 4100 w/ Swift 350/600
4) M3 control arms & bushings
5) M3 or euro M sways
6) M3 strut brace & rear chassis brace.
7) Lightweight forged alloy wheels -- under 20 lbs., 18"
8) Lightweight rotors

The cheap route is to get the old BMW perf kit.

Experts like Harold (HPA), Kevin Bird, et al no doubt could provide better advice.