Penske double action shocks.

[Keith Robinson]

Just acquired a new 'toy'; a Formula Ford with gas shocks. I don't have any experience with this car or the shocks.
I understand Nitrogen is usually used in these shocks, if I put compressed air in them (they currently read zero pressure) just for slow speed testing what could possibly go wrong ??

[Rick Kirchner]

well technically, since air is 85% nitrogen, the only advantage of bottled nitro really, is the lack of moisture. If you get moisture in there it will like be hard to get out. The moisture is what causes the majority of the pressure variation with temperature.

[DaveW]

^^^^

Actually, 78% N2, but you are right - the thing to worry about is the moisture.

[Keith Robinson]

^^^^

Actually, 78% N2, but you are right - the thing to worry about is the moisture.

Thanks guys;
That's the only thing I could think of, expansion of the moist air (as with tires). As a mid pack driver I don't think I would even notice that but the idea of rust on the inside of my Penskes doesn't appeal to me!
Update; I have found a MotoX suspension specialist not too far away, I'm going to see him next week. Rather then buy all the equipment myself this might be the cheapest solution.

[true racer]

The main reason that nitrogen is used in shocks is because of the pressure required. Penske recommends 250 psi which is difficult to obtain with any standard air compressor. A second reason, as was mentioned, is that nitrogen is "dry" compared to compressed atmospheric air which contains water from humidity.

I have run Penske shocks (and Fox too, which are very similar) on Formula Fords for a long time. The higher pressure is required to keep the oil from foaming as it passes through the valves. There are other reasons as well. In my experience, I usually begin with the 250 psi figure and then experiment from there, but rarely get below 200. With the double adjustable shocks, you have a lot of things to play with and I try to get a good basic setup with the compression and rebound adjustments before I experiment with pressures. For a good starting setup, you may never have to stray very far from the standard figure. You will find the shocks Soooooooo much better than the non canister type shocks that you will wonder how you ever drove a FF without them.

To use nitrogen, you should buy an inflation valve, available from Penske or from Pegasus, a small nitrogen regulator which is available from a welding supply store, and a small bottle of nitrogen also from the welding supply. Once you have the tools, you may start using nitrogen in the tires as well. Hope this helps.

[EricP]

The main reason that nitrogen is used in shocks is because of the pressure required. Penske recommends 250 psi which is difficult to obtain with any standard air compressor. A second reason, as was mentioned, is that nitrogen is "dry" compared to compressed atmospheric air which contains water from humidity.

I have run Penske shocks (and Fox too, which are very similar) on Formula Fords for a long time. The higher pressure is required to keep the oil from foaming as it passes through the valves. There are other reasons as well. In my experience, I usually begin with the 250 psi figure and then experiment from there, but rarely get below 200. With the double adjustable shocks, you have a lot of things to play with and I try to get a good basic setup with the compression and rebound adjustments before I experiment with pressures. For a good starting setup, you may never have to stray very far from the standard figure. You will find the shocks Soooooooo much better than the non canister type shocks that you will wonder how you ever drove a FF without them.

To use nitrogen, you should buy an inflation valve, available from Penske or from Pegasus, a small nitrogen regulator which is available from a welding supply store, and a small bottle of nitrogen also from the welding supply. Once you have the tools, you may start using nitrogen in the tires as well. Hope this helps.

^ that’s what I did. Wasn’t too expensive. One thing: make sure they are fully pressurized before you do setup/alignment!. Yeah, I forgot that the first time after I took all the alignment stuff down and put away the scales... got to practice setting it all up again...

[Keith Robinson]

The main reason that nitrogen is used in shocks is because of the pressure required. Penske recommends 250 psi which is difficult to obtain with any standard air compressor. A second reason, as was mentioned, is that nitrogen is "dry" compared to compressed atmospheric air which contains water from humidity.

I have run Penske shocks (and Fox too, which are very similar) on Formula Fords for a long time. The higher pressure is required to keep the oil from foaming as it passes through the valves. There are other reasons as well. In my experience, I usually begin with the 250 psi figure and then experiment from there, but rarely get below 200. With the double adjustable shocks, you have a lot of things to play with and I try to get a good basic setup with the compression and rebound adjustments before I experiment with pressures. For a good starting setup, you may never have to stray very far from the standard figure. You will find the shocks Soooooooo much better than the non canister type shocks that you will wonder how you ever drove a FF without them.

To use nitrogen, you should buy an inflation valve, available from Penske or from Pegasus, a small nitrogen regulator which is available from a welding supply store, and a small bottle of nitrogen also from the welding supply. Once you have the tools, you may start using nitrogen in the tires as well. Hope this helps.

Thanks for the information; I have had the shock seals replaced and the shocks filled with nitrogen by the local MX bike expert. I may buy my own 'kit' at some time but I'll try a couple of races first to get used to the car.
ApexSpeed community always comes through, thanks to you all.
See a lot of you at Elkhart Lake I guess!!??

[true racer]

Thanks for the information; I have had the shock seals replaced and the shocks filled with nitrogen by the local MX bike expert. I may buy my own 'kit' at some time but I'll try a couple of races first to get used to the car.
ApexSpeed community always comes through, thanks to you all.
See a lot of you at Elkhart Lake I guess!!??

Keith, the seals do leak somewhat and due to the high pressures and small nitrogen reservoir capacities, a small amount of leakage will result in a large pressure drop. Most racers who use this type of shock carry a bottle to the track and "check" pressures each morning. Checking in this case means just recharging to the proper pressure. If you try to actually check the pressure with a digital tire pressure gauge for example, the small amount of gas lost in the checking process is enough to significantly lower the resulting pressure. The equipment is a rather small investment when you can spend the money on it.

We will be at Road America in the big blue trailer of Regogo Racing. Looks like we have 5 cars going.

Robert Metcalf

[problemchild]

Thanks for the information; I have had the shock seals replaced and the shocks filled with nitrogen by the local MX bike expert. I may buy my own 'kit' at some time but I'll try a couple of races first to get used to the car.

Keith, Many of us have their Penske shocks not leak. I have 7 sets in use now and none leak. I certainly don't check them every morning. The shocks will function properly as long as they have 80-90 psi in them, although you certainly want the pair on each end of the car to match. Many FF racers set them at 100-125 psi. You are probably fine to have them checked by a friend with a gauge occasionally. If you do have a leaker, get it fixed. You will certainly make it through a weekend with a leaker, by putting a blast of air in before each session. These are low-maintenance items that will last years of light duty if in good shape. Most of us put far more use on them in the trailer, as you likely will from BC to RA, and back.

[true racer]

Keith, Many of us have their Penske shocks not leak. I have 7 sets in use now and none leak. I certainly don't check them every morning. The shocks will function properly as long as they have 80-90 psi in them, although you certainly want the pair on each end of the car to match. Many FF racers set them at 100-125 psi. You are probably fine to have them checked by a friend with a gauge occasionally. If you do have a leaker, get it fixed. You will certainly make it through a weekend with a leaker, by putting a blast of air in before each session. These are low-maintenance items that will last years of light duty if in good shape. Most of us put far more use on them in the trailer, as you likely will from BC to RA, and back.

OK, I stand corrected. That's just my experience.

[Bob Wright]

Shocks (Penske, Dynamic, etc) should be serviced by someone who knows the product and has the correct parts. As Greg mentions, they will last a long time with light use and should not leak at all. Transporting the car over long distances can be brutal on them. I have been educated by my crew chief over the years not to ignore the shocks and get them checked on a regular basis (1 to 2 years or sooner if you run full seasons).

Shameless plug:

Anze Suspension
516-671-3960

Angelo has worked with me for longer than I care to think both as crew chief and shock guru. He is a Penske dealer and services most major brands.

[true racer]

Shocks are not difficult but they do require a bit of experience to get them valved and adjusted correctly for the car and driver in question. I agree with the other responders that a good shop should be employed for this if the owner of the car does not have this experience. Keith says he has done this with a shop in his area.

And if the shocks can be run as low as 80 to 90 psi effectively on a FF, this is great. Lowering the pressure will effectively soften the shock action, particularly in bump. I had a situation once in which we went faster with a particular car the softer we adjusted the shocks. Eventually, we could go no softer and began to lower the pressure. The ultimate cure for the problem in this instance was to revalve the shocks and then restore the pressure to a higher figure. We won the Runoffs with this car.

I will agree that the shocks do not leak much. A slight weeping of oil around the shaft seal is the tell-tale sign. But they can leak without leaving oil around the seal. Since you cannot effectively check the pressure to find out if they are 10 or 20 pounds low, especially after a long tow, it seems like good practice to reset the pressure once you get to a race. If you have the equipment with you, why not recharge them first thing the next morning too, just to make sure? Its not difficult and ensures that you are running with whatever pressure you have determined to be the best for your application.

Bottom line is everyone does what works for them. I was only trying to help Keith out by relaying my experience with such shocks.

[Keith Robinson]

Shocks (Penske, Dynamic, etc) should be serviced by someone who knows the product and has the correct parts. As Greg mentions, they will last a long time with light use and should not leak at all. Transporting the car over long distances can be brutal on them. I have been educated by my crew chief over the years not to ignore the shocks and get them checked on a regular basis (1 to 2 years or sooner if you run full seasons).

Shameless plug:

Anze Suspension
516-671-3960

Angelo has worked with me for longer than I care to think both as crew chief and shock guru. He is a Penske dealer and services most major brands.

Thanks for information; the shocks seals were replaced by a Moto X gas shock expert.
When I towed to Indianapolis I had blocks under the frame of the car, holding it solid, so shocks didn't 'work' the whole trip!
Gas shocks are a 'new world' to me, all the input is much appreciated !!

[billtebbutt]

Others may disagree, but I would never willingly lash a car down to blocks for a tow (unless there was a corner missing )

It would seem to impart a lot of "rigid" stressing to the chassis, likely in ways/places not designed for it. Tie down the wheels, let the shocks do their job, check em at the race.

cheers
bt

[Keith Robinson]

Others may disagree, but I would never willingly lash a car down to blocks for a tow (unless there was a corner missing )

It would seem to impart a lot of "rigid" stressing to the chassis, likely in ways/places not designed for it. Tie down the wheels, let the shocks do their job, check em at the race.

cheers
bt

The trailer suspension doesn't allow any undue 'shock' to the car; worked fine for 7000km trip to IMS and back.
Thanks for your concern.