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      12-27-2012, 07:51 AM   #1
TexasZed4MC
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H&R sport spring info

I swear I searched at least a dozen different ways to find this answer to no avail. I am trying to find out, just how much harder are the H&R Sport springs on your stock shocks? The car has 48k on it and figure they will need replacing soon anyway, which points me to coilovers. But for the sake of the argument, are the sport springs worth the price saving? We all know that basically once you get the ride height set on coilovers you pretty much leave them alone. anyway. Oh forgot remember the car does see the track guys.
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      12-27-2012, 10:03 AM   #2
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I don't recall any specific threads on this, it usually comes up as part of general discussion.
How fast they will degrade OE shocks is hard to say, but for a tracked car it will definitely be sooner.

IMO, for a tracked car I wouldn't consider springs..
The biggest advantage of COs is the ability to corner balance and also to tune for rebound & compression. (if DA)
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      12-27-2012, 11:22 PM   #3
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I track my car and am running H&R springs. Went this route as an interim approach until the stock shocks need replacing, then it's coil over time (or unless the Ohlins GB happens first (yah right!)).

The improvement over stock is very noticeable. I found the stock springs crashy, bouncy, and generally crap. These improved on that, as coilovers will further improve things again. They don't ride any harder than stock - if anything the car feels more planted over the bumps.

If you buy them make sure you get the 15mm pads for the rear.
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      12-28-2012, 08:48 AM   #4
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I'm having the Eibach/Bilstein vs KW V3 debate right now. My car will likely live out its days as a weekend fun car (no track, maybe an autocross), and a softer suspension with progressive rate springs will handle the bumps and improve performance on the street. I'm sold on the reviews of the KW's other than the fact that I don't need all the adjustability; I'll probably set it and forget it. I guess the shocks can compensate for wear over time with some minor tweaks.

Ideally I'd like something with the same performance as stock, but with a better ride and a very minor drop. A better ride does more than just make the car more comfortable - it will make it last longer on the street. Every pothole loosens the fit and finish, and before you know it, things that you never thought could rattle are doing exactly that.

I've read mixed reviews of the Bilsteins, and really spring/shock combos in general. The Eibachs seem to give the drop I want with approximately the same ride quality as stock (maybe slightly stiffer and less crashy), but the hesitation of a lot of forum members to go this route has me questioning why.

The question for me really comes down to, is it actually possible to improve ride quality AND performance? I don't buy the argument that it's possible to lower the car and get a more comfortable ride. I see it as a gimmick repeated by people trying to sell you something. Lowering the car reduces suspension travel, meaning you will need a higher spring rate to avoid bottoming out... and that reduces ride quality. Firmer springs distribute the car's load around corners to all four wheels better (unless you hit a bump), improving tire contact patches and increasing maximum grip. But again, firmer springs sacrifice ride quality. Going the other way (softer) should do the opposite, right? Is there something magical about aftermarket coilovers (suspension geometry, etc) that allows you to improve ride and performance? Or do they simply allow the user to optimize the car via multiple methods of adjustability? In my (in)experience, it's a sliding scale - you either have comfort or performance, until you deviate so far outside of the optimum category that both performance and comfort are reduced at the extremes... too soft or too hard, and you sacrifice both.

Lastly, if coilovers did in fact improve handling and comfort at the same time, why would a $60k car not come with them stock? Is the Honda Ebay aftermarket really that far ahead of BMW? No...
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      12-28-2012, 04:02 PM   #5
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Quote:
Originally Posted by pokeybritches View Post
The question for me really comes down to, is it actually possible to improve ride quality AND performance?
Yes. When I first put on the V3s I noticed two things:

1. It's less harsh. The stock suspension has softer springs and bmw notoriously compensates by having stiffer shocks. By going with slightly stiffer springs (the kws are progressive, but at full compression they're 2x stiffer in the front) and softer shocks, the whole thing rides smoother and less jarring when you hit a bump.

2. The High speed damping is much better. There's a curve with some uneven pavement at the end of a fast stretch of road right before I get home. On stock suspension you can feel your tires leaving the pavement. With the V3s, you can feel the tires staying in contact with the ground the entire time.

Before I could feel myself hopping sideways ever so slightly, now it feels like I'm in control.

I am riding at max height in the front of the V3s with the rear to match though. It's only a modest 0.5" drop, but I still scrape on the occasional ramp unless I go at it diagonally and super slowly.

Quote:
Lastly, if coilovers did in fact improve handling and comfort at the same time, why would a $60k car not come with them stock? Is the Honda Ebay aftermarket really that far ahead of BMW? No...
AFAIK It's not about them being coilovers, it's because they have better components. The coilover aspect just lets you adjust height and a few other niceties.
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      12-28-2012, 05:53 PM   #6
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The Z4MC's suspension is too soft at the front which allows pitching on braking and lifting on acceleration, which makes the steering floaty and imprecise, and at the rear it's too stiff, which makes the ride very uncomfortable. The 3 centre coils of the rear springs are 19mm thick whereas the front springs are just 11mm thick: obviously there's a huge mismatch between front and rear spring rates, yet BMW cars supposedly have a weigh balance F:R of 50:50.

I've fitted AC Schnitzer Racing suspension (basically Bilstein PSS9 made to ACS's specification), which has rear springs of 16mm and front springs of 14mm, which redresses the mismatch of F:R spring rates. Instantly, this helps to overcome the inherent ride and handling problems of the Z4MC with OEM suspension. The adjustable dampers then permit the fine tuning of the spring oscillation rate so that for street use there is sufficient damping to make the car sufficiently compliant on uneven and bumpy surfaces, yet by simply adjusting the rebound/compression on the dampers, the oscillation rate of the springs can be increased so that the suspension is far more reactive for track use.

The fact the spring rates of the F&R suspension of the ACS suspension is a much closer match than OEM, means that the load-shifting caused by braking and acceleration is reduced, irrespective of damper adjustment, which in turn, translates into better handling. In the case of the Z4MC, the softer rear springs give a great ride with no loss to handling.

I also have a Z3MC to which I fitted KW V3 (with genuine coilovers at the front) and with OEM suspension the Z3MC is way too soft with excessive bodyroll, and KW V3 and H&R ARBs have transformed the handling of that car, and with damper adjustment the car can ride like a sedan or be suitably stiffened to give awesome track handling without a rock hard ride.

Yes, you can have a suspension that can give you the best of all worlds, BUT, you've got to make the damper adjustments to make the car perform optimally on the street and then make further adjustments to make the car handle optimally on the track. IMO, it's no big deal to make the changes when required and no different than getting dressed in different clothes to do specific jobs.

With regard to KW V3, there is separate adjustment for rebound (at the top of the dampers) and bump/compression (at the bottom of the dampers). This adjustment is easy to do on the front dampers, but on the rear dampers, this is much more tricky, especially for bump/compression. I like being able to make separate damper adjustments but if you don't intend going on track much, then the single adjustment of rebound and bump/compression, as used on the ACS Racing suspension works well too.

In the case of the Z4MC, the ACS suspension lowers the rear end by a fixed 10mm and I've lowered the front by 20mm to increase the rake angle. I wouldn't want to go any lower.

Hope this helps.
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      12-29-2012, 03:32 AM   #7
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Thank you very much for the responses! Hopefully I didn't threadjack, but I had the same question about whether it was worth it to do spring/shock or go straight for coilovers.

I'm glad someone was able to answer how you could get both ride and performance improvements. Much appreciated!
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      12-29-2012, 01:55 PM   #8
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Quote:
Originally Posted by pokeybritches View Post
I'm having the Eibach/Bilstein vs KW V3 debate right now.
pokeybritches, if by "Eibach/Bilstein" you mean the Bilstein B12 Pro-Kit, which includes non-adjustable Bilstein shocks and Eibach spings, then exactly the same decision I'm facing now.
I found lots of positive feedbacks for the KW V3 kit, but since I never track my car the V3 seems an overkill. The Bilstein B12 Pro-Kit goes for about a half of V3 price, hence it's very sexy - but I cannot find solid reviews from Z4M owners.
I would highly appreciate if you can post (or PM me) the pros and cons you found, regardin the Bilstein/Eibach set.

Quote:
Originally Posted by exdos
I've fitted AC Schnitzer Racing suspension (basically Bilstein PSS9 made to ACS's specification)
I have asked AC Schnitzer for a price, and they forwarded me to their local dealer who quoted 2708 Euro (!) for their suspension kit. That's like 50% more expensive than KW V3 or Bilstein PSS10.
exdos, if you can share this information, how much did you pay for the ACS set, and where did you buy it from? Thanks.
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      12-29-2012, 03:26 PM   #9
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exdos, if you can share this information, how much did you pay for the ACS set, and where did you buy it from? Thanks.
I bought my ACS Racing suspension secondhand off a UK car forum, shortly after I bought the car in March this year. They'd been for sale for about 2 months and nobody else seemed to want them and so I made a ridiculously low offer for the kit and I got it for my price and they've only done about 2k miles. One of the best bargains I've ever had. If I'd had to pay full price for the kit I would've bought KW V3 again.
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