The GS is notorious for a squishy suspension...

[chilloutdamnit]

But should it be this squishy? http://www.youtube.com/watch?v=DV6MXpUPpVI

I was cleaning up some rust on my front fork with wd40 the other day. Now my suspension is ULTRA squishy. Like more squishy than a dirtbike. If I lift up the bike a tad bit, the whole suspension decompresses.

What's the verdict, gstwins: Abnormally squishy or just an abnormally slow to notice things owner?

[xunedeinx]

Mine is about that ssquishy.


Minus the -squeaky,squeaky-squeaky- sound.

[bombshelter13]

Looks about like mine looked before throwing in some new springs (.80 Sonic Springs have me nice and comfy in the city where I do most of my riding, but I'm not that heavy).

[noiseguy]

Eh. May want to check your fluid level and condition. Put the front on blocks to decompress the suspension, pull the fork plugs and measure your air gap

[chilloutdamnit]

Just installed a set of progressive springs with 10w oil and the suspension is much improved. I still seems a bit squishy when compared to my buddies sv, but I guess that is just the nature of progressive springs.

[chilloutdamnit]

Quick question about the fork oil level. The instructions aid to add oil to 140mm, but when I did that, I found I used much less than the 350ml recommended by others on this site.  Will adding more oil stiffen up the front or should I adjust the preload more?

[bombshelter13]

Are you measuring the gap with the forks fully extended? A 140mm gap with the forks fully extended is more fork oil than the same gap size with the forks compressed.

[XLAR8]

fork oil amount is in the owners manual and progressive springs aint that good (not good for alot of cornering) and beside that they will still be squishy at first then tighten up the further they go down

[chilloutdamnit]

I measured fully compressed and cycled the forks ~10 times to get oil distributed. Maybe I didn't drain all the oil out?

Although the ride is much improved, it bothers me that the forks seem just as squishy as they did with the stock springs.

[burning1]

The 350ml value is a starting place. Go by oil level, not that figure. 140 is going to be wildly different than the 350ml level you hear about. 350ml is the starting volume when using the OEM level of 91mm. 91mm is way too high when using aftermarket springs, and will result in hydraulic lock and blown fork seals. 100mm is absolutely the highest you should go with aftermarket springs.

A couple of things immediately come to mind... 1st; 10 weight oil seems way too light. I ran 15 weight in my race bike, with emulators. Some have suggested going as far as 20 weight, but I wouldn't do it unless you're a really heavy guy.

Rule of thumb though... Before mucking with the oil level too much, get the sag values correct. Adjust your preload spacers so that you have 5-20mm of static compression, and 30-50mm of rider compression. If you can't get both those values in range, you have the wrong springs and there's nothing you can do with the fork oil to fix your front end.

Next... If your ride feels very uncontrolled (your forks overshoot, buck you off, squishy under braking) it probably means that your fork oil is too thin. Re-fill with a thicker oil. If your forks seem controlled, but you want better bottoming resistance, add some oil... Bring the level up to 120mm... Then add oil in 10cc incriments until you no longer use all the forks range of travel under normal riding conditions.

These are kind of basic steps, and should get you in the ballpark of correct, assuming that your spring selection was good.

To respond to bombshelter13's comments... Fork oil is always measured with the forks compressed. If you measured any other way, you did it wrong.

[chilloutdamnit]

Thanks Burning, you've answered all of my questions. I had to use 10w oil because my local shop was whack and didn't order the 15w for a week after I placed an order. I will check the sag values and make sure the preload is adjusted correctly and will mix in some 20w in order to stiff them up a bit.

[bombshelter13]

Measure fully EXTENDED, not fully COMPRESSED.

[chilloutdamnit]

Ok, I checked the sag values and I have 32mm static and 8 mm rider sag. I'm not sure it's possible to get the numbers in the range you mentioned with progressive springs. I might be able to get the rider sag to fall in the correct range if I shorten my preload spacer (I have a 1" rather than 0.75" spacer as recommended by the manufacturer).

[burning1]

Measure fully EXTENDED, not fully COMPRESSED.

Installing the springs and spacers raises the oil level by 80mm or so. The fork cap takes up 20-30mm. The suspension has about 110mm of travel. I'll leave it to you to figure out what will happen if you set the oil level to 140mm with the forks fully extended.

[burning1]

Ok, I checked the sag values and I have 32mm static and 8 mm rider sag. I'm not sure it's possible to get the numbers in the range you mentioned with progressive springs. I might be able to get the rider sag to fall in the correct range if I shorten my preload spacer (I have a 1" rather than 0.75" spacer as recommended by the manufacturer).

Is it possible you have those numbers reversed? Typically, rider sag (measured with you on the bike) is greater than static sag (the bike it's self.) Those numbers seem pretty decent, though as someone mentioned earlier, the fact that you're using dual rate springs probably changes the target measurement off a little. On straight rate springs, 10mm static and 40mm rider would be more or less ideal, though a little variance on that would be fine.

If you thing the suspension is blowing through travel too quickly, go to 15 weight oil. As you mentioned, you could remove about half the 10 weight oil and replace it with 20 weight for the same affect. Pulling 120cc of oil out would be a good starting place.

For better bottoming resistance, raise the oil up. Remember that the oil level creates a pnumatic spring inside your forks; so it won't provide more damping, it will create a highly progressive spring that really comes into play at the bottom of travel.

[chilloutdamnit]

Is it possible you have those numbers reversed?

No, those are the numbers I measured... although I don't think I got all my weight on the pegs when I measured rider sag. Guess I gotta measure it again  .

I did put 100 miles on the bike today. It was a great improvement over the stock springs. It feels like my front end is stuck to the ground. It was much better on the highway as well-- I didn't feel like the bike was unstable at all. The rear suspension is starting to show it's weakness, but I think I'll hold off on upgrading for a few thousand miles.

[burning1]

I'm confused, because the numbers you are giving me are impossible. There's no way that the forks extended when you sat on the bike as those measurements would suggest.

[RichDesmond]

With the progressive springs set the oil level to 110mm. That's measured from the top of the tube down to the surface of the oil (so it's really the air gap you're measuring) with the spring and spacer removed and the fork tube fully collapsed.
Normally I recommend 35mm of sag, but progressively wound springs force you into more of a compromise between preload and sag. To get to 35mm you'd have to use a lot of preload, which is bad. To keep the preload reasonable run a little more sag 40mm. These numbers are total sag, bike and rider. Here's a writeup on measuring/setting it.

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

Get your sag and oil level set correctly before messing with oil weight.

[chilloutdamnit]

I'm confused, because the numbers you are giving me are impossible. There's no way that the forks extended when you sat on the bike as those measurements would suggest.

My mistake, I gave you the static and difference of sag and static. I am seeing around 32mm static and actually 47 mm sag (I remeasured this morning).

Even though these numbers are not ideal, the ride felt much better than stock. Hopefully I can tinker more with the suspension in the future and the ride will only get better!

Thanks for all your help guys.

[burning1]

Hi Rich,

Thanks for clarifying.