when i pulled the inserts out of the wreck (one red, one black boge, go figure) there was what appeared to be clean motor oil in the housing. is this common practice? if so how much is poured in prior to reinstall?

kevin

I've heard of this being done. It is to help "cool" the shocks I believe. I would say the weight, out weight (ha) the cooling effect.

Paul

yes it is put in for cooling.... I would think about 3-4 oz should be ok

Bilsteins go in dry - should be ok with the others

When I got the front Koni inserts for the 911 from Jason at Paragon, he recommended no oil.

-Rusty

Dont be confused here folks. Some of the original inserts used OIL in the shock tube.

The racers use ANTI FREEZE to keep things cool.

ALL 911 Carrera's that came with Boge struts had oil in the strut tube.

Rare that you run across cars that still have the OE shocks in them.

B

the car had 3 koni reds, the boge was an odity. then i remembered today the kid i bought the wreck from hard curbed 2 pass side front fuchs. bet he ruined the strut unit on the first go round.

kevin

i have another koni so i have set of fronts. whats the general consensus? to oil or not to oil?

kevin

Well Brad, that finally explains why when I took the front shocks off the 70 1.7 it had anti-freeze in the struts w/the Koni's. I was like WTF! when I disassembled the struts cuz it made a mess on the garage floor. Blair was laughing pretty hard too! Those Koni's are in my car now...still waiting for some koni's....Did you ever get a price?

Geoff

i wonder why racers would use antifreeze? antifreeze does not transfer heat that well. ( if you put over 67+% in a wasser motor it will run hot ). i guess it would keep the parts from rusting.

Rusting? Wouldn't oil also retard rust? Anyway, I read some time ago on PP911BBS that only the Boge inserts had the oil to transfer the heat to the outside of the strut housing. All others went in dry. I suppose if you knew what you were doing, you could drill holes in the strut for cooling.

Tryan,

I have no idea why racers used anti freeze. I dont do it.. but I have seen other racers pulling their hair out trying to keep the antiF in the struts and not on the ground.

Heat within our strut tubes is a big deal. Your sticking a tube inside of a tube. The heat has nowhere to go. That is why you see so many external resovoir shocks these days.

B

Uhmmmmm, NO!

Heat is maybe .01% of an advantage of using an external resovoir shock and only because of the extra fluid. The rest of the 99.99% is that is allows you another way to meter(control) the fluid in compression forces. All external resoviors have at the very least a floating piston with air on one side and fluid on the other. Most that offer bump adjustment on the resovior itself have another piston and/or metering valve with different size passages.


-Tony C

Sure.. come on. Its sales point right on the sticker on the box. "better cooling" LOL

I read it on the sticker and on the website !!

B

At least we will have something to discuse over lunch rather than our normal bs about buying businesses and trivial things like that.

-Tony

This isn't that complicated. Lets look at a few things:

1) the strut insert (shock) absorbs a huge amount of energy.
2) the engergy absorbed is converted to....(drum roll)... HEAT.
3) the strut insert is isolated inside the strut tube surrounded by a jacket of stagnant air.
4) air is a poor conductor of heat, so heat transfer to the strut tube is slow.
5) heat buildup will degrade the effectiveness of the shock. (shock fade)
6) oil is a much better heat conductor than air.
7) replacing the narrow air jacket surrounding the strut insert with oil should greatly increase the heat transfer from the strut insert to the strut tube.
8) the strut tube is much more effective at shedding heat because it is in the path of outside airflow.
9)The volume of air between the shock insert and the strut is very small, so it doesn't take much oil to fill the void. Weight is a non-issue.

I'm really currious to hear a counter argument to this. It seems pretty straight forward.

-Ben M.

the most important bit here is "stagnant air".
stagnant air is a very good insulator.
moving air is a very bad one. thus moving air is very good to cool things.

now, has anyone ever thought about a design that would move air through the strut tube/housing?
that should work just fine and eliminate the oil mess ...

just my 17 cents ...
Andy

well, that was one big circle. i'll just put a 1/2 cup of oil in upon reinstall. now 30wt, 10-40. detergent or non?

kevin

Castor oil Kevin, helps with the bumps too.
Geoff

the ones on my rectum? " rectum? hell it damn near killed him".

kevin

just curious about the antifreeze. if it leaks out, it would be less of a chance of crashing you or someone else.


pull my hair out, no. i don't have any hair left to pull out. are eyebrows okay?


i would think that a thinner oil would transfer heat better.
might be wrong, but i did eventually passed all three quarters of thermodynamics. barely.

also isn't there a big disclaimer on an antifreeze jug that warns of potential paint damage? couldn't be to good for the paint on the inserts.

If antifreeze leaks out, won’t the oil?

If oil gets on the brake pads/rotors isn’t that just as bad or worse?

Might be the reasoning behind why some guys go the anti-freeze route.

Hey, you’re the one who wanted to hear a counter argument to this.

Har har har.

You've got a better chance of getting internal shock oil on your brakes/tires/pavement from a shock blowout than you do of getting your "cooling oil" on anything. The only way it's going to leak out on anything is if you're taking the strut apart in your garage. (Or if you're Andy drilling cooling holes in yoru strut tube )

-Ben

Thats why the crap keeps leaking out! DOH!!!!!

From the factory 944 manual FWIW:

"The shock absorber housing may be filled with thin oil or ATF to improve cooling.

However the shock absorber housing should not be more than max. 2/3 full, if cartidge is touching bottom of housing.

If too much oil is added it would run out of housing when hot. This would automatically cause incorrect diagnosis (defective absorber)."