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Calling all geniuses, couch mechanics, 'net blowhards, and speculators. Oh, and real people who really know something are welcome too.
Big Question:
Are the Bilsteins at the link below, exact replacements for Porsche PASM shocks? (Of course I am going to DIY) http://www.pelicanparts.com/catalog/..._pg1.htm#item0
I spoke to Pelican and they didn't know if these Bilsteins were the exact shock in the car (they are cheaper of course). I find is surprising that Bilstein would build a sophisticated shock like this for such low volume use... but what do I know.
Small Questions:
- Anyone heard of 997.2 shocks leaking? I got like 175K out of my Boxster Ss shocks and I only changed them due to a broken spring.
- Any tips for replacing them? I don't want to do the springs. Pelican and other suppliers make two versions of the fronts: one with a cable set and the other not. Does anyone know the difference?
- So what is causing the cupping? The shocks? The alignment? Pics of the tires and before/after alignment numbers below.
Issues: Cupping front tires and leaky shocks.
I discovered last night that my front tires are cupping on the inside (no vibration or noise). I immediately attributed this to the out-of-spec negative camber I had put into the alignment circa 1.5 years ago. So, off to the alignment shop today (Bavarian in KOP), where they did an alignment with the fronts to spec and rear to spec but less negative camber per my request. They came back and told me all four shocks were leaking. Darn.
Readers of my posts will know that I drive my car all year, all weather with snow tires and proudly take the car on baja photographic activities in the Jersey marshes. Yes, the car takes a pounding there. If leaking shocks are the cost of my use, then so be it.
Another observation: I have complained about an odd floating at 80 MPH on the Jersey turnpike and now turn on Sport mode anytime I am on the highways. I didn't do this when the car was new to me... so.... I suspect this is because the shocks were just going bad.
If it has the cable then its a PASM shock. If not, then its non adjustable damping. You should be able to reuse the original spring but you will need to get a spring compressor to take the tension off and take it apart to reuse it and the other parts.
I have a 2009 C4S. My rear shocks are slightly weeping according to my shop. Not severe enough to do anything yet, but on my future to do list. I have 65k miles on the car. Tire wear seems normal so far with factory alignment settings.
Yes cupping is a symptom of worn shocks. http://www.monroe.com/en-US/support/Symptoms/Tire-Wear
It sounds like your shocks have been going bad for a while, probably gradually so its hard to notice, and you've been trying to compensate with Sport mode. If it was bad enough to cause cupping, well then when you get new ones prepare yourself for an improvement that I am sure will be, uh, shocking.
Camber does indeed contribute to uneven (inner) tire wear. How could it not? Just look at it! (And check out the link.) But, it is a question of overall use. The idea is for the extra inside wear when driving straight to be balanced by the extra outside wear when cornering. Guys who strike that balance will notice even wear in spite of the extra camber. Guys who don't corner enough for the camber they've got will notice the inners wearing faster. More camber isn't necessarily "better", its really just another compromise or tradeoff, just like everything else.
Some updates... for those who like staring at train wrecks, you can follow my neurotic ride through this decisioning process....
Chuck, thanx for the Monroe link. I spoke to a few experts and they generally point to failing shocks for the cupping like Monroe shows. I thought it was the negative camber I had dialed in.... my Ford engineer friend (now in the service side at Ford) said too much negative camber can do the same thing... but now I suspect it is actually the shocks doing the cupping...... the cupping is recent but the negative camber was there a long time and didn't show on my winter tires. So, maybe when I get another alignment after the shock replacement, I will dial in the negative camber again... I really liked the way it makes the car turn in.... makes it a bit twichy but that is a much more fun drive.
Bilsteins: So far, my research is showing the Bilsteins are not the same as the Porsche design... the PASM cables come out the bottom for one thing and have been knows to fail. Others complain of clunking after a few thousand miles. Some love them. Data is a year or so old. Typical eh? I talked to Pelican Parts and they didn't know who made the Porsche part and could not know if the Bilsteins they list (as an OEM supplier) were the actual shock or not.
So I am learning a few things through this process..... I am making some assumptions of course... when it comes to more technical things like PASM shocks where Porsche has some secret sauce in there, OEM does not mean the exact part. It appears to be true for many other things I replaced on my cars... I did a heat exchanger in my Boxster that came in a white, no label box, and had the exact manufacturer markings on it and was way cheaper than the Porsche labeled.... same for spark plugs, sway links and other such parts.
To sum, it looks like I will be opening my wallet for the Porsche stuff..... I haven't found the cheapest yet, but some of the P-dealers discount and I am seeing big differences in prices out there.
Have you considered Bilstein B16 Damptronic coilovers? Yes they are more expensive than Bilstein's fixed height the shocks, but you get adjustable ride height, corner balancing capabilities, and a better suspension for aggressive street & track usage. You should be able to find a set for around $3K shipped to your door through one of the forum sponsors. I paid about $2800 for my 997.1 set during a holiday sale. The Bilstein normal setting falls somewhere between the OEM normal and sport mode, and the sport mode is stiffer than OEM sport. I would expect 997.2 to behave the same.
Or what about sticking with OEM? Doing a quick Internet search I'm seeing OEM shocks from online Porsche dealers as low as $2600 for a set for your model. Compare all this to about $1800 for Biltsein's B8 Damptronic shocks only.
Camber does indeed contribute to uneven (inner) tire wear. How could it not? Just look at it!
You are looking at the car stationary. On the road -- where it counts -- under way -- when it counts -- the camber flattens out.
Both of my cars have had the factory recommend camber (front and rear) and in one case the Boxster had even more negative camber and tire wear is even as long as toe is correct. The rear tires want to have some toe out so underway -- when it counts -- the rear tires move forward and that toe out becomes zero toe.
More data: I pulled the wheels and fronts are NOT leaking but the rears are. So..... not sure what to conclude here but the following:
1 - Cupping in front is NOT due to leaking shocks. So it must have been the negative camber I put in there or.... I have a wearing control arm. I suspect it was the negative camber.
2 - Rear tires are wearing perfectly even.... with me taking out the negative camber, and with leaking shocks.
3 - Bounciness I felt at high highway speeds and therefore my increased use of SPORT setting points clearly to the failing rear shocks.
BTW, the shocks are stamped with both the Porsche part number and the Bilstein logo, so there ya go, these are Bilsteins. It appears from my research that I can not get white-label Porsche shocks as there is no true Bilstein equivalent - the Bilsteins I see available on Bilstein's website all show the rear PASM cable coming out of the bottom where the Porsche model are from the top.
Pics below.. note it has been raining and there is water on the boot, that is not oil. I pulled both fronts but only one rear. No need to pull the other rear as I will replace both. I needed to pull both fronts because maybe only one was bad and therefore causing cupping... but no, both clean.
Rear Shock - I wiped the top of the cylinder so it looks clean but it was oily grime. You can see oil and grime on the lower part of the spring... it was all oil grime gunk down the shock tube - clearly leaking. The white towel is from a wipe right along where the silver piston enters the shock.... it was oil.
Front... notice the "white" ring around the top of the cylinder where the piston enters? That is just dry and clean and not from my wipe. The white rag is perfectly clean from a wipe around where the piston enters the cylinder. No leak.
I have a 2009 C4S. My rear shocks are slightly weeping according to my shop. Not severe enough to do anything yet, but on my future to do list. I have 65k miles on the car. Tire wear seems normal so far with factory alignment settings.
Of course the question is how do you know when to replace them? All I can say is that I was getting a floaty sensation at high speeds on the highway that resulted in my changing my behavior and always turning on the SPORT mode to stop it. I joked it was making me seasick. To be honest, it was not much... at least it wasn't like the old Monroe stagecoach commercials or where you push on the fender and count the rebounds. Nothing like that... the system had to be loaded up to show.
10-28-2015, 07:37 PM
Leaking Shocks, Tire Cupping, Alignment Specs - Oh My!
