A lot of testimonials documented (as my self) the shi... I mean soft spring rate on our beloved GSs

I am considering to change the springs... however I would like, before doing this, know your thoughts about fitting air valves on the top of the nuts of the front forks!

Maybe could improve the performance when riding in poor quality streets. It would add increase the nonlinear behaviour when compressing the forks hard.

something like this




What do you guys think? Any previous experiences?

Some complementary material that I found.


http://forums.sohc4.net/index.php?topic=108201.0

Could be cheaper than proper springs but certainly not better. There has to be a reason all the manufacturers got away from air assisted forks.

Proper springs, valve emulators, and fresh oil are going to be much better.

That said, I think you should try it. I like to see people try things out on the GS500.

I have been using air-spring (as in no coil spring) shocks on mountain bikes for over a decade. You have to have an air chamber that specifically is designed to hold air. On the GS they will probably leak.

On mountain bikes they leak enough air between rides (daily) that it requires topping up normally. Some are better than others.

Further, increasing air pressure will increase the probability of air bubbles forming (foaming) in the oil. Another reason not to mix air and oil. You could use nitrogen instead...

Or just replace the springs, or cut them and add a spacer. Way easier, way more reliable, and way less likely to blow a seal when you go over a bump.

As mr72 says MTB has been using air for the spring in their forks AND rear shocks ,for not ten, but more than  20 years. The first forks did use a straight air/oil interface, but most nowdays have a separated chamber. But remember the crossection of of motorcycle and mtb forks isn't that different, but the rider/bike weight is many times greater on a motorcycle, so the pressure required to work as air only would be prohibitive ( all sorts of seal pressure and stiction problems).
That said I did experiment with air spring only forks on my MX bikes in the 70's and got some good results but the bikes were much lighter. The progressive nature was very helpful in those days ( short travel).
I was using air assist in my racing bike forks recently as it allows a quick and useful tuning aid, but the pressures were lowish. Worked well . For the road, a increasing rate could be helpful in some circumstances, but as mr72 says, the right spring rate is better. And cutting springs works well, IF you do the calcs properly and are careful with your workmanship and heating ( you have to reseat the cut spring).

Meh.

The first step is to get the suspension sprung for your weight. This means replacing the progressive springs with linear rate springs. Why? Because linear weight springs are consistent throughout their range. RaceTech has a good calculator for the springs you need based on your weight.

Once that is done you can focus on improving the damping. Oil level and viscosity makes a big difference and assists with tuning. If you really want to get happy step up to cartridge emulators, which are relatively cost effective and make the forks more tuneable.   

+1 better springs AND emulators, check 'mikesXS'.

I agree with new springs and emulators.  IMHO adding air to the forks is a bandaid approach in an attemp to achieve better handling. 
More importantly note that the first schrader valves installed on the fork caps by any OEM were there, in fact, to bleed off any built up pressure between motos or heats to allow the forks to perform as designed (at 0psi). 

Ok guys.. new springs will be!

After reading all your arguments I am convinced that trying something different do not worth the trouble.

I found a shop that has a stiffer spring.. I am not sure if they are progressive or linear... however I will check personally.

There are not many options here in my country..  but at least I found one (i will continue to search more).

I would like to thanks each one of you. This was something that I was thinking but never got somebody with proper knowledge to talk to.

Seriously, THANKS!

No such thing as "progressive springs" unless the closer coils actually bind ( not a good thing).  A progressive wind does NOT give you a progressive rate. If you put them on the bottom of the forks they will travel straighter though that's it.  Sorry but physics is a Buddha Loves You. Check out any spring calculator. Do you see any variable for inter coil distance. There is a reason...
Emulators will make a HUGE difference to the rideability of the bike, IF you tune them properly. If not they can make it worse. Read the instructions and check out Youtube for tuning tips. I have put them on every pair of conventional forks I have had for decades. They can ransform a bike from nasty front end to heavenly ( OK maybe not quite that much).

Quote from: gregjet on April 07, 2018, 01:17:28 PM
No such thing as "progressive springs" unless the closer coils actually bind ( not a good thing).  A progressive wind does NOT give you a progressive rate. If you put them on the bottom of the forks they will travel straighter though that's it.  Sorry but physics is a Buddha Loves You. Check out any spring calculator. Do you see any variable for inter coil distance. There is a reason...

Unfortunately they exist and are common OEM springs. Here's a good write-up about progressive versus linear springs. Progressive springs are a little more comfortable for the average rider, but if you want consistent, predictable performance linear springs are the only way to go. 

I repeat , " progressive springs" are not progressive rate. If you wish to believe they do, feel free, but it shows a lack of understanding of physics and engineering.
The rate of a spring is dependant on the length of wire, the modulus of elasticity of the material, the diameter, of the wire. To calculate the spring rate of a coil spring you use the number of coils, the coil diameter and the the overall length to give you the actual lenngth. Then you need the wire diameter and the elasticity of the material to calculate  the spring rate per length. Intercoil distance in not included.
"Progressive" springs are a marketing "have".
You can make a spring progressive by having a section of different intercoil distance AND having that section coil bind. This is NOT a good way to make a spring.
The spring you see with a closer intercoil distance at one end is to ensure the spring travel in a straight line instead vectoring off to one side , especially during short displacements.