Taymar

I sent out my 951 M030 shocks for a rebuild, as the fronts were blown and leaking.

I got them back today and tested them a little before I put them on the car. I'm seeing inconsistent results between shocks and was hoping I could get some opinions on what to do next.

All shocks have been set to full soft, the rears by compressing fully and rotating the top section counter-clockwise, the fronts by using the adjuster tools and turning them fully clockwise. I have wound a spare nut onto the threads and am using a piece of pipe to press on the nut, so I'm not applying any force to the adjusters.

The rears:

One rear compresses very easily for the first 1/2" and I can hear bubbles. After that it firms up and seems to require a uniform force to compress it the whole way.

The other rear compresses very easily for the first inch or so, same bubble sound. After that, it compresses like the first one.

If I fully compress both rears and let them extend, they seem to do so at the same rate, until the last inch where one extends quicky, the other one does so half an inch later.

The fronts:

One shock is pretty easy to compress fully. It seems uniform and I can almost do it with one hand. It takes about 12 seconds to fully extend.

The other front is considerably harder to compress. I can only just compress it with both hands, leaning on it with a block of wood. After the first couple of inches of compression, it gets even more difficult. Once it's fully compressed and I let go, it's fully extended in about 6 seconds.

This is my first time dealing with adjustable shocks, or shock rebuilds so I'm not really sure what is 'normal'.

Any opinions would be a big help.

Dougs951

Where did you send them for rebuilds?

Taymar

To Koni North America.

Arominus

No two shocks are exactly the same, the only way to match the adjusters up would be with a shock dyno. Did they replace valving? or reuse the existing? Have you talked to your rebuilder yet? the shocks may need a little time to settle from shipping as well. Leave them sitting in an "as installed" orientation for a few days and see what it does.

ramius665

How much did Koni charge for the rebuilds? They quoted me $100/labor and $165/parts for each shock about 18 months ago.

Taymar

It was just over $800 all in, for all four shocks.

I am not 100% sure what they replaced on the fronts, they said the cost would vary depending on how many parts needed replacement.

On the rears, they don't stock parts for these shocks any more so they only used the housings, swapping over all the internals from a comparable new shock.

Is a shock dyno something that race shops would have? I may try and find one locally and see if they can check them all out. I appreciate that you can't really tell much by testing by hand.

I've set them all standing up against a wall and will see if there's any improvement, thanks for the tip.

I'd estimate that right now, one front shock requires about 120lbs more weight to fully compress than the other.

harveyf

I think the general consensus is that you can only spot really major problems (such as a shock that compresses in about 2 seconds) with a hand test. What you can exert by hand is just so different from in-service loadings that it is totally apples and oranges. I think you have to trust Koni that they know what they are doing.

Here is an link about shocks that might help you learn what you are dealing with. It will answer your question about shock dynos and much more.

http://farnorthracing.com/autocross_secrets6.html

mj951

Nice link, thanks!

Taymar

Thanks Harveyf, the information on that site definitely helped me get a better overall understanding.

I called another shock rebuilder yesterday who said some of what I'm seeing isn't necessarily uncommon for newly rebuilt shocks. They also explained that the only way to know for sure is to dyno test them, so I think I'll get that done for peace of mind. It'll also give me a printout which (assuming I can make sense of it or get some help) might help me with where to set the adjustment.

TrevorW

I purchased new Koni Str.t's for my e46, had similar issues. This was the response from koni:
Trevor,
The self-extension of a shock absorber or strut after being compressed that is often seen in a low or high pressure nitrogen gas charged shock is simply a side effect of the presence of the gas charge in the shock. The self-extension does no actual work in the function of the shock, it simply is a side effect of its presence. The KONI STR.Ts are a twin-tube low pressure gas charged design where the oil in the shock does the actual function and the gas charge helps very slightly raise the temperature and pressure range of the oil. Since the STR.Ts have a low pressure internal nitrogen charge to begin with, the shocks may not self-extend fully and at the same rate when brand new simply because the initial friction and stiction of the piston rod seal and guide assembly might initially overcome the internal gas' tendency to push the piston rod back out. Since the shocks are brand new, they have not had the chance to actually work together enough for the various parts to "wear in" together and reduce the initial friction so that the shock might self-extend. It would not surprise me at all if after some use on the car, that same shock might self-extend once some brand new friction was reduced by the parts getting used to working together.

Taymar

Thank you. It's sounding like the air pocket in the rear shock and the different extension speeds on the front are not anything to worry about. The difference in force/weight needed to compress the fronts might need a bit more investigation it seems like.

Dougs951

are your fronts adjustable?

One could be adjusted differently

Taymar

Yep, fronts and rears are adjustable. All four are set to full soft. Koni said I can send them back for a retest for peace of mind, they've been awesome to deal with at every step of the rebuild. One of the shocks did get a bit banged up during shipping so it may be worth it just to rule out that there's no damage.