Suspension question not Corvette
07-09-2012, 02:46 PM
#1
Le Mans Master
Thread Starter
Suspension question not Corvette
OK, so this is not Corvette or even car related, but suspension is somewhat universal and there are a lot of smart people on this forum that I think could give very sound advice regardless of the platform. I trust you guys more than I do the 25 year olds on the motocross forums.
I have always been into motorcycles, particularly motocross racing. I transitioned to HPDE and time trials after several years of motocross racing back in the nineties. For many reasons including money and personal interests I am going to get back into motocross racing (this time GNCC style off road).
Anyway, I am looking into a new bike, for the first time on some of the new motocross bikes to be released in 2013, they are going to offer Pneumatic forks (basically a shock with the springs inside). They tried this in the mid 70's with failure.
Instead of using actual springs inside the forks, they are going towards air pressure. Here is an excerpt from their description.
this new fork is easier to tune. Equipped with Schrader valves atop the fork caps, the standard air pressure of 33 psi can be adjusted within a range from 32 psi to 36 psi—the equivalent of installing softer or stiffer replacement springs—to accommodate varying rider weights and speeds. Air alone fulfills the pressurization needs; there’s no need for nitrogen or other inert gasses. Of course, as per usual motocross bike expectations, the fork and shock are also fully adjustable for compression and rebound damping settings.
Now here is my concern. If they are using plain air and not nitrogen would it not be susceptible to temperature fluctuations? Those forks are going to get pretty warm once they get moving and that doesn't even take into the consieration of outside air temperature. If they are adjustable from 32-36 psi, I would imagine that only a couple pounds either way will have a dramatic effect and once the bike gets hot or it gets hot outside, the air will expand in the chamber and the bike will become increasingly stiffer as you ride it (not a good thing).
Suspension fads come and go in motocross and I am concerned about whether to stick with the tried a true spring in fork style or go with this new Pneumatic design?
I have always been into motorcycles, particularly motocross racing. I transitioned to HPDE and time trials after several years of motocross racing back in the nineties. For many reasons including money and personal interests I am going to get back into motocross racing (this time GNCC style off road).
Anyway, I am looking into a new bike, for the first time on some of the new motocross bikes to be released in 2013, they are going to offer Pneumatic forks (basically a shock with the springs inside). They tried this in the mid 70's with failure.
Instead of using actual springs inside the forks, they are going towards air pressure. Here is an excerpt from their description.
this new fork is easier to tune. Equipped with Schrader valves atop the fork caps, the standard air pressure of 33 psi can be adjusted within a range from 32 psi to 36 psi—the equivalent of installing softer or stiffer replacement springs—to accommodate varying rider weights and speeds. Air alone fulfills the pressurization needs; there’s no need for nitrogen or other inert gasses. Of course, as per usual motocross bike expectations, the fork and shock are also fully adjustable for compression and rebound damping settings.
Now here is my concern. If they are using plain air and not nitrogen would it not be susceptible to temperature fluctuations? Those forks are going to get pretty warm once they get moving and that doesn't even take into the consieration of outside air temperature. If they are adjustable from 32-36 psi, I would imagine that only a couple pounds either way will have a dramatic effect and once the bike gets hot or it gets hot outside, the air will expand in the chamber and the bike will become increasingly stiffer as you ride it (not a good thing).
Suspension fads come and go in motocross and I am concerned about whether to stick with the tried a true spring in fork style or go with this new Pneumatic design?
07-09-2012, 03:47 PM
#2
The problem I can see is not whether the gas is chemically inert or not, it is if there is moisture in the gas. Nitrogen has the advantage of being 'dry' as it is manufacutered, Compressed air requires additional treatment to remove the water. The water vapor (humidity) in the gas is what really screws up hot pressures in my opinion. Otherwise it would be a straight calculation to measure the temp of forks and the expected rise in 'spring' pressure as temp increases.
07-09-2012, 05:04 PM
#3
Melting Slicks
I don't have an answer, but a lot of Mountain Bike forks are like this. I was very happy with mine. Very light weight and can adjust for any terrain.
Steve A.
Steve A.