indraporsche

I am doing installation of Koni shocks from P964, which is 15 mm longer shaft than the P993 Row Boge shocks.

And the new P964 Eibach springs are also taller than the P993 Row springs.

Can i just cut the new Eibach springs to make it shorter to fit the Koni shocks that also have 15mm longer shaft. (i won't do anything about the shocks) to install to my P993 Carrera.

I just want the Row height for my P993.

Is this the correct actiont to take (cut the springs) ?

Thank you

AOW162435

In some parts of the US, this is acceptable behavior.

If you want ROW ride height, the most popular suspension change is to go with ROW Porsche M030 coils and Bilstein HD shocks.

Cutting coils is, well, rather crude.


Andreas

RallyJon

Ideally, you would shorten the shaft as well. Keeping the piston in the middle of its travel is key. Think about where the piston will be with short springs and a long shaft.

David in LA

How about using a torch and just heating the coils until they settle to the desired height?!?

indraporsche

Cutting coils is rather crude, yes i definitely agree, but i don't have another option beside use this longer Eibach or back to Row with Koni.
This thing that still make me confuse, will it be better to cut/heat the coil, or i would be better use the Row Spring with Koni ?
The Row shock will not be used again, it is bad already.

Keeping the piston in the middle is key - very good opinion, so which is better,, keep the 15mm longer shaft or shorten the shaft, as i think the differences is not much, only 15 mm compare to the whole long of koni which is 195mm ( the Row shocks is 180mm)

RallyJon

The exterior length doesn't matter. Put a zip tie on the shaft with it fully compressed and then extend it to measure the actual travel. Then fit it to the car and use the zip tie again to see where you are along the travel. If you don't have at least 2.5" of compression travel at your static ride height, it's going to be a jarring ride.

indraporsche

Very clear explanation RallyJon, thanks, i'll do exactly as you said. i consider shocks problem solved.

Any suggestion about the springs ? Perhaps i better use that Koni with Row, or will be better with shortened/heat compressed Eibach ?

38D

Cutting a spring changes the spring rate (makes it much stiffer). You'll never get the stiffness the same on both sides of the car and will end up with an evil handling car.

indraporsche

It is a hard choice, using the Row, or modified the Eibach (by cutting, or modified the spring perch lower. Will decide later, still confuse.

Anyway thanks a lot to all.

PS : the Eibach spring is softer than the Row when i pushed ny hand.

Steve Weiner-Rennsport Systems

Colin is absolutely correct. You'll ruin the springs by heating or cutting them and never know what rates you actually wind up with. Further, shock valving MUST match spring rates and the marriage between the shocks & springs isn't going to be a good one.

MDamen

Heating the springs affects the temper, which will weaken the spring. Cutting the coils doesn't affect the strength, but it increases the spring rate. The spring rate is a direct inverse function of the number of coils. If you cut half the coils you will have double the spring rate. If you cut 1 out of 8 your spring rate will go up by 8/7.

Also be careful you aren't bottoming out that longer shock when using a shorter spring.

indraporsche

I'm going to try Koni with Row springs first, and if the ride is not good, i'll try another possibility Koni with Eibach without modification (plus a new modified spring perch to make the spring seat lower, so i don't need to cut or heat the springs).

And about the shocks, if it is possible, i'm going to shorten it to fit the Upper Concave Washer seat lower and make it exacly the same with the Oem Row shocks ( doesn't mean cutting the length of the shafts that have adjusters).

Colin 90 C2

I think you may find that the Eibach spring compressed height is almost the same as the ROW spring.
As you found out, the Eibach spring compressed easier because it is a progressive spring while the ROW spring is a linear spring.
You will get slightly different cornering characteristics between the two.

As others have said, don't cut springs. You will get a bouncy ride and your shocks will not live a long life.

Garth S

If you are planning to machine the seat on the Koni shaft downwards by 15mm, you may wish to continue while in the lathe to extend the length of threads on the shock body. I did this on the Bilsteins, seen below - but cannot determine from your pictures whether it is possible on the Konis. Regardless, the lower threads make it feasible to use taller springs, so eliminates the argument about modifying springs.

BTW, which ROW springs are you referring to? The 993 ROW MO30 front springs are a progressive design in both coil spacing - and use of a tapered ( decreasing diameter) spring wire stock. I have tried Eibachs and H&R springs, and they both use constant diameter wire with variable coil spacing: these two manufacturers allow the top coils to bind/lock together under compression such that the spring rate increases because only the bottom 2/3 of the length is working.
I think that you would find that the MO30 is a very capable spring - but it is taller than the Eibach ( and H&R) for the same chassis height; therefore, lower threading on the shock body, or dropped lower spring perches are required.

indraporsche

I think you may find that the Eibach spring compressed height is almost the same as the ROW spring.
As you found out, the Eibach spring compressed easier because it is a progressive spring while the ROW spring is a linear spring.
You will get slightly different cornering characteristics between the two.


Very good point Colin, i don't even think about this possibility. I'll try that.

If you are planning to machine the seat on the Koni shaft downwards by 15mm, you may wish to continue while in the lathe to extend the length of threads on the shock body. I did this on the Bilsteins, seen below - but cannot determine from your pictures whether it is possible on the Konis. Regardless, the lower threads make it feasible to use taller springs, so eliminates the argument about modifying springs.

BTW, which ROW springs are you referring to? The 993 ROW MO30 front springs are a progressive design in both coil spacing - and use of a tapered ( decreasing diameter) spring wire stock. I have tried Eibachs and H&R springs, and they both use constant diameter wire with variable coil spacing: these two manufacturers allow the top coils to bind/lock together under compression such that the spring rate increases because only the bottom 2/3 of the length is working.
I think that you would find that the MO30 is a very capable spring - but it is taller than the Eibach ( and H&R) for the same chassis height; therefore, lower threading on the shock body, or dropped lower spring perches are required.

extending the length of threads on the shock body, that's what i have in mind too. Sure it could be lengthen by 15mm to the lowest.

which ROW springs are you referring to?
Mine is 993.343.531.00 (marked red), If i'm not mistaken the M030 is 965.343.531.01 (marked orange green).
The car is come from Great Britain WPOZZZ99ZSS31xxxx, i think should have the Row height.
My Eibach spring have constant diameter wire as you can see in the picture above.
these two manufacturers allow the top coils to bind/lock together under compression such that the spring rate increases because only the bottom 2/3 of the length is working.
Very clear explanation, i can understand more about it, so i have to try the eibach without any modification, (or perhaps just lengthen the thread of the shocks).

Great answers to all, very helpfull.