Replacement shock recommendations

[jerry]

I have just been informed by Koni that the shocks currently on my car are not rebuildable.
I would be interested in any recommendations for a 1981 PRS club ford. Price and simplicity is very important. Opinions please!

Best Wishes,

Greg Kokolus
NCF#56
PRS RH-01
Phila Region SCCA

[JDUB]

I have been told by a reputable source that the best bang for the buck is a new set of Ohlins
ST44s.. You can go to [url="http://www.shock-shop.com"]www.shock-shop.com[/url] to read up on these..

[Curtis Boggs]

I'd be very surprised if those Koni's weren't rebuildable. You should contact Truechoice to get the correct answer - they are the Koni experts.

For small cars such as FF's, Penske is the best choice. Ohlins has a design handicap that doesn't allow good grip with cold or cool tires - once the tires are hot, they are as good as anything else, but until then they are a handicap.

[DENIS]

The older Koni 30 series shock (still I like them) are considered a non rebuildable shock. If this is what you have.

I've been told that Truechoice can or has modified them with a special valve to charge them, which was not on the original.

[JDUB]

Hello Richard,

Thanks for the information on a Koni rebuild facility, it looks like they really tear into them.

The Penskes are a great shock indeed.. I am interested in hearing more about the Ohlins shock's design flaw?

The statement that the shocks work poorly until the tires are warm leads me to think that the oil viscosity in the units you have seen may have been too high which would lead to stiff action until the fluids warmed up with the tires but that's just a shot into the dark..

81 PRS RH02 #45

[Curtis Boggs]

The problem is fluid inertia being the overriding factor in the initial buildup of damping forces just as the shaft begins to move. With the twin tube design, ALL of the fluid must move for ANY fluid to pass from one side of the piston to the other. Granted, now that they have bleed shims available, that problem is reduced somewhat, but not nearly enough. The 4-way Penskes, with their twin adjuster shaft, passes a lot more fluid thru a much shorter passageway. On the 3-way Penskes, the problem is still there in bump movement, but totally free movement (or the lack thereof) in bump is not as critical as it is in rebound for grip production. The Ohlins "low speed" adjusters are really more of a "lower midrange" adjuster.

We once tried a special Ohlins shock that had a series of small holes near the base of the inner tube that acted as a bypass. It helped a bit, and the difference could be seen on a very expensive linear dyno, but it wasn't until we made our own bleed shims (about a year before Ohlins made any themselves) that we saw any real improvement. But still not enough.

Ohlins has also made a piston arrangement that allowed a small amount of fluid to go around the o-ring behind the band seal on the piston. Once the piston moved a bit - maybe .010" - the o-ring sealed up the passage. We never tried it ourselves, but I heard that it helped, but sometimes was erratic. I don't think that they are still producing it.

I also think that, at least for our small cars, that the Penske cannister is much better, especially the latest version.

A fun experiment would be to install the Penske 4-way shaft and the lasest cannister design onto the Ohlins T44 body.