Ok so I recently bought my first street bike (04 GS500F) and am looking into upgrading the stock suspension. I've search around the forums for as much information as possible and it seems that the Kat 600 shock is a good bolt on upgrade for the rear suspension so I don't really have any questions there unless you have some other suggestions or advice. My main question is about upgrading the suspension in the forks. I'm new to this so I'm still kind of lost. It looks like most people upgrade their forks with progressive springs from http://www.progressivesuspension.com. I was searching around on their site and when entering Year/Make/Model of my bike they did not list the GS500.

Also when you buy the springs do you chose the stiffness or are they all the same? I weigh about 180 with all my riding gear on.

I was in this situation no so long ago.  Kat 600 rear (for me, about your weight) works out really well.  It'll raise the height of the bike for sure, so be aware of that.

On the front, I have .85 linear sonic springs with 15w oil (recommended by Rick at sonic for street riding/my weight; you're a little lighter, so may want to go .80...drop him a line and ask).  After doing a ton of research, I came to the conclusion progressive springs really won't offer much benefit on the GS.  If you want a sportier suspension, go linear (in my opinion).

New suspension makes a world of difference.  Having done several things to the bike, if I could only do one it'd be suspension.  It feels like a whole new bike the first time you ride it.

What roads do you ride? I am about your weight (10pounds more, in gear) and I find my Kat750 very stiff for my commuting. The spring it shelf is perfect for my weight (7mm free sag / 35mm rider sag) but my roads are bumpy.
I am installing a R6 shock which is a happy medium between GS and Kat next week, I would recommend you search a bit about it (disregard what buddha says though.. )

In the front I also run sonics, .90. They also are a bit stiff for commuting but I they work fine on track.

Of'course depending on what you want to achieve, and how much you want to spent, there are other options.

The cheapest is heavier oil, increased oil height (more progressive "spring" rate), and cutting the original spring sorter (or even better binding some coils)

If you're interested in upgrading the front end, I'm selling the one I build for my race bike -- check out my signature.

For the rear shock - Kat 600 and Kat 750 are sprung very similarly. They are good for heavier riders, but lighter guys might want to consider the R6 shock swap. The Kat 600 comes with a ~12kg/mm spring, where the R6 shock is ~10kg/mm. Stock is ~8kg/mm.

The Kat 600/750 shock is exactly the same length as stock, IIRC. If you have not adjusted pre-load on your stock shock, the Kat shock will make the bike sit higher, only because the spring doesn't compress as much when you get on the bike. If your sag is correct on both shocks, the ride height should be the same.

Ok I think I'm going with some linear .85-90 front springs, either race tech or sonic. I'm still trying to figure out what all will work on the rear end. I saw a nice 08 gsx650f shock I want to buy but I'm not sure if it will bolt on. Dose anyone know if this shock will fit?

Quote from: Rkulp on April 28, 2011, 06:09:21 PM
Ok I think I'm going with some linear .85-90 front springs, either race tech or sonic. I'm still trying to figure out what all will work on the rear end. I saw a nice 08 gsx650f shock I want to buy but I'm not sure if it will bolt on. Dose anyone know if this shock will fit?

I think the gsx shocks require modification to the linkage.  .90 will probably be too stiff.  The suspension is just right with .85, maybe even a little stiff, but tolerable and the benefit is worth it (and it matches well with the Kat).  Rick at sonic can help you out; drop him a mail.  They're great over there.

Yeah, I am over 200 lbs with all my gear and find the .90 a tiny bit too stiff for the road. Probably should have gone with .85's but it is borderline.

Quote from: Pelikan on April 28, 2011, 11:14:44 PMI think the gsx shocks require modification to the linkage.  .90 will probably be too stiff.

Springs are matched to the rider/bike weight. There's no way of knowing if the springs are too stiff without knowing who's riding.

He said he's 180 with gear.  I'm about 190 with gear.  Ergo, it might be too stiff for him, which is why I suggested he speak to Rick.  .90 would be a touch punishing for someone in our weight range on surface streets, methinks.

Is there some other factor involved beyond rider weight, riding style, and road surfaces that I'm unaware of?

You're right. I missed the 180lb part. .90s are almost certainly too stiff. Generally, the lightest weight spring that doesn't bottom is going to give the best ride. Too stiff, and you're asking the tire to cope with greater forces than necessary, and transmitting more impact through the rider/bike than you should.

Too stiff a spring can compromise handling and safety just as easily as too soft a spring.

Quote from: Rkulp on April 27, 2011, 10:16:38 PM
Ok so I recently bought my first street bike (04 GS500F) and am looking into upgrading the stock suspension. I've search around the forums for as much information as possible and it seems that the Kat 600 shock is a good bolt on upgrade for the rear suspension so I don't really have any questions there unless you have some other suggestions or advice. My main question is about upgrading the suspension in the forks. I'm new to this so I'm still kind of lost. It looks like most people upgrade their forks with progressive springs from http://www.progressivesuspension.com. I was searching around on their site and when entering Year/Make/Model of my bike they did not list the GS500.

Also when you buy the springs do you chose the stiffness or are they all the same? I weigh about 180 with all my riding gear on.

Let me jump in with a few things.

First, like most suspension people these days we strongly prefer straight rate springs to progressively wound ones. There's an explanation up on our website at http://www.sonicsprings.com/catalog/straight_vs_prog_tech_article.php
How much does it matter though? It depends on a few things, but the short answer is that the heavier you are and/or the harder you right the bigger difference the straight rate springs will make. They are always going to be at least a little bit better, but a lighter weight rider who just does commuting and day trips may not be able to feel much difference. And any aftermarket spring is going to be a huge improvement over stock.

Rate: at 180 geared up you should be in either a 0.80 or 0.85. If you're a "normal" rider (whatever that is ) then the 0.80s. If you're pretty aggressive, lots of lean angle and heavy braking, or doing track days, then the 0.85s. (Racing would call for 0.90s)

Harshness: This is usually due more to compression damping or too little sag than spring rate. If you feel like a spring is "too stiff" first check your sag. Total sag should be around 35mm, and a little more (but no more than 40mm) is ok too. Many people install aftermarket springs with the same total spring/spacer length as stock, on the GS500 that's guaranteed to give you too much preload and too little sag. If your sag is less than 35mm, shorten the spacer by the amount of sag you lack.
If your sag is good then go to a slightly thinner fork oil. If you have 15w in there now try 10w. If that ends up being too "bouncy" then a mix of 10 and 15w should be good.
If you think that you may want to experiment with fork oil weight it's a good idea to buy the oil locally so that you can easily stick to the same brand. The weights vary between brands, so if you switch you're introducing an unknown variable to the equation.
Emulators are also a good mod, they smooth out the compression damping curve (make it more linear) and reduce harshness over sharp bumps.

Brand: In straight rate springs the most common brands you'll see are Race-Tech, Traxxion and Sonic Springs. Ohlins and Eibach are also good, and I'm sure that there's others. (disclaimer: For those of you that don't know, I own Sonic Springs) From a quality and performance perspective they are virtually identical. Same alloy (ASTM-A1000), same processing steps. So buy from the vendor that you feel will give you the best combination of service, support and price.

Finally, that's a killer deal that burning1 has on his forks. For anybody who that spring rate is right for, jump on it.

Great advice Rich. I'm a new rider so Im not very aggresive. I'll be buying some .80 sonic springs as soon as I get a rear shock. Looking for a kat 600 now but still wondering if the gsx650 will fit.

Hi Rich, I really appreciate that you weighed in on this discussion.

Quote from: Rkulp on April 30, 2011, 05:20:34 AM
still wondering if the gsx650 will fit.

Lots of those out there in great condition, unlike the Kat 600s.  would be nice. 

i am same weight and have been looking for a while, at the help of the forums members I've narrowed my decision to the sonic springs. Just debating .80 or .85, I will be carrying saddlebags and tankbag so I am not sure if this makes a difference. I will not be doing track days and I have alot of bumps and potholes in Philly. Really in a toss up on which one to do.