Spring choice m030US vs ROW vs HR
 

I have a 2001 Boxster S with US m030 suspension .I need to replace a shock and have found a great deal on a new set of 4 Bilstein sport. They are slightly shorter than stock and I am seeking advice on what springs to use.
Easiest is to reuse my m030 US springs and ideal is probably ROW m030 (costing about $450) maybe another option is a set of HR lowering ones found locally for $250.
I have searched and read what little I can find . I,m not even sure I will actually see a drop with new ROW springs vs already set/sagged US springs . With HD springs already in my possession is it worth the effort and expense to change them

I probably can't help much, but I just replaced my stock base-model springs with ROW M030 springs on new HD Bilsteins. The amount of lowering is hardly noticeable (less than 1/2").

As far as I can tell, there isn't a big difference in spring rate on the front, but the rear is much stiffer; it's so much stiffer that it borders on too stiff for me. One of my buddies was thinking about doing the same thing to his base model, but after driving mine, is reconsidering doing it because it is so much stiffer.

Of course, suspension stiffness is a subjective thing. We are both in our fifties, and have lots of race miles under our belts, so maybe we just both got that stuff out of our systems.

Depends on the spring rates and ride height. Getting your springs, dampeners, corner balance and alignment to all play nice is an art. ROW M030 is a sure thing to get 1" lower and a bit stiffer with Porsche proven and tested spring rates. Unknown HR lowering springs?? I don't know...

I am in my 60,s and have driven P cars since the mid 70,s .This is my first water pumper other than briefly owning a 951 in the late 80,s. I have my own corner scales and access to alignment equip. but other than checking and moving some weight ,without coilovers changing corner balance is difficult on the Boxster chassis.
The drop from m030 is supposed to be about 20 mm front and 10 mm rear. I have read the spring rate I already have is the same just a little higher ride height. I suspect the springs I have (US m030 ) should have sagged at least slightly in 65,000 mi.
I don,t want a major drop and am likely not going to use H&R but was considering it since everything will be apart.

The question is whether you like the ride comfort and ride height of your existing US M030 setup?

If so, then replace the shocks and you're done.

If not, you'll have to trade off whether the possibly slight additional drop from the ROW M030 is worth the $450. Or if you want even more drop, then maybe the $250 H&R's come into play. Both of these options may change the ride comfort.

Comfort is highly subjective so only you can decide if the US M030 is comfortable enough or if you think that something stiffer would be ok. You might want to find someone with a ROW M030 and/or the H&R's and get a test ride to see what you think before you commit.

Topless was kind enough a few years ago to give me a ride-along in his car when I was considering the move to PSS9's - afterwards I was convinced that was the way that I wanted to go.

I had pss9 and m030 sways in my 993 . I don,t want to spend that kind of money on this car.
I have read somewhere (Insite perhaps) that US and Euro (ROW) spring rates and shock valving are the same ,just a small drop. I can do either while apart . I have no objections to the ride stiffness of my current US m030 suspension just need to replace one shock and got a real good buy on a set of 4 Bilstein sport.

found the spec for ride height and measured mine. The US m030 springs I have are sitting at the low limit on the front which makes them about equal to the regular height of ROW springs . They are at the mid point of +/- 10 mm on the rear making them equal to the Row rears at their high end.
If the spring rates are the same US vs ROW. (as I have read) then it seems hardly worth changing them . The car might even end up sitting higher with new springs

Hello johnsjmc,

i would just replace the shocks with new ones. Worn shocks also can also lead to a little lower ride height.

Don't forget to replace the strut bearings and also check ad replace the rubber bearings for the stabilizers. These parts simply wear and age over the years.

Regards, Markus

It's my understanding that the ROW M030 spring rate is slightly stiffer than the US M030 rate.

If it were me, I'd just replace the shocks, bearings, and bump stops.

There is a rather long analysis of the m030 vs row m030 used on a 996 which I found on rennlist . It does find some difference in spring rates and shock valving between them. I have been unable to find anything definitive about the 2 986 suspension pkgs. At least one post by insite ( I think) suggests the spring and shock valving is the same only the static ride height is different.
At this time I,ve got new bumpstops and new Bilstein yellow sport struts.
Has anyone run their springs without the thin plastic compensating plates If I leave them off my ride height will be a few mm lower.
I am not tracking the car just fast road use.

IIRC, if the springs are shorter, that have to have a different spring rate

I don't know if this is true on the Boxster platform but I do know that the primary difference for most Bilstein Sport vs Bilstein HD shocks is the shaft length of the shock making it shorter overall. The HD's can be used with stock springs but the Sports "generally" require shorter springs like those made by H&R, Eibach etc. Again - not knowing the specifics of the M030 springs - but it would seem like you would at least want springs like those.

The ride height as delivered is approx. 10 mm lower. That doesn,t necessarily mean the spring wire length is shorter or longer. It could be exactly the same but with the coils set slightly closer together. If the wire dia and wire length is the same then the torsion length and rate remains the same.

Also yes the sport shocks have shorter shafts (by 1/2 to 1 in). That might increase the static preload on the springs at droop but they should sit at the same ride height compressed .

good point

There are specs, perhaps in Porsche service literature or parts manual, on spring wire thickness and ride height. I seem to recall the US-spec M030 had the thickest wire. I believe most of the lowering that happened on the euro-spec springs happened at at the front of the car and not as much as at the rear.

(Edit: found the ride height specs from the service manual - attached.)

But for the sake of philosophical argument, let's just assume for a moment that the spring rate on us spec vs euro spec M030 wire were the same. In this case, the bump stops would be engaged sooner (with less spring deflection required to engage the bump stops), thereby raising the effective wheel rate for the M030 spring sooner compared to the us-spec M030.

I used the specs and measuring method above and found my existing US M030 springs with 18 in wheels is sitting at the low limit front and rear ie 145 mm front and 150 rear as I said in an earlier post.(#7)

Hello johnsjmc,

as said - test it with the Bilstein Sports (think you mean Bilstein B6 with Bilstein sports). http://web1.carparts-cat.com/default.aspx?230=1&36=0&35=171&32=11523&34=0,10012 1&14=1&10=7DDCC6C3FC6D449EA5BA497A87B2DED4018001&1 2=130

I think the overall ride comfort will be less with this shocks, because B6 are stiffer than stock. I don't think it's not that important if they are only a little bit shorter. Overall ride height is adjusted by the springs.

My recommendation is always to use components that are tested to fit together. What's why a M030 setup has completely different components from a stock setup. Porsche does a lot of driving tests with their cars and i think the undercarriage is tuned very good from the factory.

But if you can't get the OEM shocks or if you are on a budget there is only one way to go - testing.

If you change the ride height, don't forget to do a full alignment to the car when the chassis/undercarriage has sat down.

I tested Startech shocks that where designed for my other car with stock springs. But the pressure stage of these dampers was really too high for the stock springs. Really good for cornering, but no comfort. So the only option was to use progressive lowered springs or other shocks. I decided to go back to new OEM standard shocks, because the overall costs for springs, installation and alignment where higher and the car would have had less comfort with that spring/shock combination. And i don't like cars that hop over every little stone – maybe that is because i'm getting older. ;)

Regards, Markus

Not the best for seeing ride height but this is mine on bilstein b8 shortened shocks and eibach springs. I had h&r springs before. I think the eibach are a little lower and stiffer. Rides pretty well..depending on tyre size and side wall stiffness. It's comfy on 17s.
http://i51.photobucket.com/albums/f3...719_160641.jpg

I,ve gone ahead and installed the Bilstein sports(B8) using my stock US m030 springs Feels good ride height not changed ,not perceptively stiffer . Have a slight rattle from front right over bumps still though.