GS550 Progressive Fork Spring Help

[Guest]

I have a 79 GS550 and am in the middle changing out the original front springs for new progressives. I ran into an issue though. The new springs are much longer. Almost the same length as both of the old springs combined. Are the new ones designed to replace both springs or does it need to be compressed down to fit? Or worst of all, did I get the wrong springs? I ordered the ones listed on progressive's website. If anyone has first hand experience with this and could shed some light I would be very appreciative. I currently have the bike torn apart in my friend's garage and he needs to leave soon, so time is short.

[RichDesmond]

I have a 79 GS550 and am in the middle changing out the original front springs for new progressives. I ran into an issue though. The new springs are much longer. Almost the same length as both of the old springs combined. Are the new ones designed to replace both springs or does it need to be compressed down to fit? Or worst of all, did I get the wrong springs? I ordered the ones listed on progressive's website. If anyone has first hand experience with this and could shed some light I would be very appreciative. I currently have the bike torn apart in my friend's garage and he needs to leave soon, so time is short.

Replace both the old springs. Cut a new spacer so that you have about 3/4" of static preload. See the "Note A" directions here:

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

Did you get spacer material and instructions with them??

[8ball]

The progressive springs instructions indicate that they don't need a spacer for the 79 GS550. I have them in my 79. I found that I needed about a 1 to 1.5"" spacer, though, to get the correct sag. because without a spacer, the static sag (with no rider) was about 2.5". I used 1/2" PVC pipe with a couple fender washers (3/4" PVC is just slightly too big in diameter). The front end that's on it now is from an 82 550M and the spacer in it now is about 3/4" tall if I recall correctly. (same springs) I only use the spacers now because I don't use the air assist preload that the 82 forks have since I swapped in the Progressives from the other forks.

[8ball]

Also, I found that 195mm fork oil level, springs removed and forks fully compressed, was a good setting. The 140mm in the instructions was way too harsh. The manual spec calls out an amount of oil, not a level. That amount translated to an oil level of 205mm, but with the spacers in and the rider sag set at 1", the ride height was a little higher, so I used the 195mm.

[OldManBrooks]

I really appreciate all the help. I decided to go with the stock oil amount of 165ml and inserting a spacer that required just a bit more compression than the stock springs I took out. I decided on this length spacer primarily because I didn't have any PVC and wasn't able to drive to the store, and because I happened to have two identical sockets that were not being used and happened to fit just about right. They were perfect diameter and about 1.25" long. With this setup the rider sag is 1.125". I've had the bike for a little over a month and it had a leak in the fork seal when I got it, so I didn't know how the suspension should feel. It did seem a bit bouncy in the rear and dead in the front. Now it feels solid in the front and inspires much more confidence. It truly is marked improvement. I can't wait to get the rear suspension done. I'm just waiting on new bushings for the Hagons I ordered. It came with the wrong ones.

Anyway, all of that was a long way to say, thank you. It's riding much better.

[8ball]

Your right in the ball park, there. Sockets are a clever solution.

[OldManBrooks]

I wanted to post an update after some more riding. I notice that when slowing to a stop the forks don't always rebound until I accelerate again. Can someone tell me if this is normal? I'm thinking I might put in some longer spacers. If my thinking is correct, this should increase rate of rebound and make the forks stiffer. Please correct me if I'm wrong.

[RichDesmond]

I wanted to post an update after some more riding. I notice that when slowing to a stop the forks don't always rebound until I accelerate again. Can someone tell me if this is normal? I'm thinking I might put in some longer spacers. If my thinking is correct, this should increase rate of rebound and make the forks stiffer. Please correct me if I'm wrong.

Definitely not normal, at least if the forks don't come up at all as you complete the stop. It is normal for the forks to extend some as you accelerate away from a stop.

If the former case, you have something causing all that stiction, and you need to find it and fix it. Adding a bunch of preload may alleviate the symptom somewhat, but causes other problems.

[OldManBrooks]

RichDesmond,

Thanks for the info. I will have to take them apart this weekend. Everything looked good when I put them back together. I pumped them a few times before inserting the springs and everything seemed ok. Also, I didn't notice it on the short ride home. I noticed it the next day. It doesn't happen over bumps. It's only under hard braking, when the weight shifts forward.