Sonic springs and air pressure

[Guest]

I had to replace a fork seal and thought I would replace the springs as well. I ordered some of the sonic springs. I see a lot concerning the fork oil, but nothing on what to do about the air damping. They seem to be against air damping systems, but don't say whether you should leave air out of the system or not once you have the springs installed. Anyone know? I would like to go for a ride tomorrow so I don't think their customer service will answer in time.

[phydeauxmutt]

Air does not "damp" the system at all, it is actually a supplemental spring.

If you get your "sag" set right, the only air you will need is what will be trapped in there naturally when you put the cap on.

What springs did you get?

What oil are you using?

My bike is on the heavier side (me, too), so I went with the 1.1 rate and am using 10w oil. GREAT ride, good control.

[tkent02]

I sometimes use a tiny bit of air to fine tune, some times it seems to ride a tad smoother, sometimes not. The springs you bought were probably sized correctly for no air. Should be able to ride without it just fine, or they will still hold air just fine like they always used to.

Up to you.

[bwringer]

With appropriately sized fork springs like your Sonics, don't use any added air.

Using air as a supplemental spring is a lousy idea -- you're depending on the fork seals to maintain an absolutely perfect seal at all times.

[tkent02]

Meh, perfection is not all that critical.

[Grimly]

With appropriately sized fork springs like your Sonics, don't use any added air.

Using air as a supplemental spring is a lousy idea -- you're depending on the fork seals to maintain an absolutely perfect seal at all times.

I'm starting to agree with that.
For decades, the European GS850s had no air-assistance in the fronts, and I was quite used to that. With the fitment of a GS1000 front setup, with air caps, I thought I'd try it. It's a pita. When it keeps air in, it can be good, but it leaks out and the balance of both legs is critical.
If I retain the GS1000 legs, I'll just fit uprated springs and forget the supplemental air - or fit a set of L legs+yokes - or recondition the 850 ones. At least I have some choices, but air in the front isn't really one of them any more.

[RichDesmond]

I had to replace a fork seal and thought I would replace the springs as well. I ordered some of the sonic springs. I see a lot concerning the fork oil, but nothing on what to do about the air damping. They seem to be against air damping systems, but don't say whether you should leave air out of the system or not once you have the springs installed. Anyone know? I would like to go for a ride tomorrow so I don't think their customer service will answer in time.

Don't use any added air pressure with the Sonic springs. Added air will make the overall rate too stiff, and too progressive.

[Rob S.]

I sometimes use a tiny bit of air to fine tune, some times it seems to ride a tad smoother, sometimes not. The springs you bought were probably sized correctly for no air. Should be able to ride without it just fine, or they will still hold air just fine like they always used to.

Up to you.

Got to agree. I'm replacing my faulty equalizer tube, and am going to try running about 10 psi.

Manual says that stock is 7.5 psi and never change that, BUT that it can hold up to 35. Go figure. Before I replaced my springs, I had to run high 20's to keep it from bottoming out.

[Who Dat?]

I'm replacing my faulty equalizer tube, and am going to try running about 10 psi.

Manual says that stock is 7.5 psi and never change that, BUT that it can hold up to 35. Go figure. Before I replaced my springs, I had to run high 20's to keep it from bottoming out.

If you replaced your springs and still bottom out, you did not order the right springs.

If you did order the right springs and still bottom out, you don't have your preload set correctly.

What is your "sag" measurement? Ideally, it should be 20-25% of available travel. Since most of our bikes have 5-6 inches of travel, that would be about 1 inch of "sag". If you get more than that, adjust your preload spacer.

Air is a wonderful spring. When it's there. It is very predictable, but one of its predictable qualities is that pressurized air WILL escape, if possible. It is better to use proper (metal) springs to hold the bike than to rely on air that might or might not be there to help.

[Rob S.]

Before I replaced my springs, I had to run high 20's to keep it from bottoming out.

Racetech, IIRC .90 (non-progressive). It certainly doesn't bottom out now. Although the 2015 Sportster "SuperLow" I just rode for two weeks did.

[phydeauxmutt]

Maybe shoulda got the 1.0 or 1.1 springs.

What is your "sag"?

[Rob S.]

Maybe shoulda got the 1.0 or 1.1 springs.

What is your "sag"?

IIRC, there were three choices, and I went with the middle one. Probably should have gone with the firmer.

How would I measure sag?

[RichDesmond]

IIRC, there were three choices, and I went with the middle one. Probably should have gone with the firmer.

How would I measure sag?

http://sonicsprings.com/catalog/setting_sag_street_tech_article.php

Unless you're a very light guy the 1.0s would have been better.