Hi guys,

Because the naked GS hasn't been available for a while, I bought a GS500F with slightly scraped fairings (standstill drop/kickstand slip) and stripped it, since that's cheaper than stripping an un-scraped one. I did the mod where you re-mount the stock headlight in the Drag Specialties bracket and put it as high as I could get it, as other people who've done this mod show in their pics: top of the headlight nearly touching the bottom of the gauge cans - the back of the left* part of the headlight basically is touching the cable that comes down from the left gauge can.

However - there's one particular ramp I take a lot (it's to the plaza two blocks from my house, which I go to a lot - stop there every day on my way to work) where the front forks will bottom out and the bottom of the headlight will tap the plastic of the mudguard over the front wheel. Already have two nice scratches from the ridges right at the bottom of the F headlight - I'm not too concerned about this as long as it doesn't get worse: they're not deep, and the front fender's already on the winter painting list since I wanna go flat black for next season anyhow.

Thing is, I need to stop it from getting worse. Right now the scratches are shallow enough that they should be fine once I paint the piece over in the winter, but if they get much deeper I'll need a new mudguard unless I want them to show.

For the moment, I've put adhesive back weather stripping foam on both points of contact (bottom of headlight and some in the spot on the mudguard it hits) and am gonna try to avoid taking that particular ramp - which is a bit of a pain, as it means choosing between two lefts at lights (one of which is a sensor that doesn't like to go off for bikes) or a three block detour down sidestreets to enter from the opposite side.

I'd like to get a proper solution though: that is, stiffen up the front suspension so it doesn't bottom out so easily. My options seem to be Sonic Springs, Progressives or spacers and heavier fork oil, but I'm not sure which of these would be best for me.

My bike is my primary commuter: I don't race, and only rarely go on highways. Most of my riding is in 50-60 kmh city areas. I weigh about 170 lbs last time I weighed myself. Occasionally (maybe once or twice a week) I'll ride two up with my girlfriend, who weighs about 125 pounds. I might put some stuff in a tankbag, but the most I typically ever have in their is a six pack and some groceries.

What set of springs do you guys think would suit me best? Sonics or Progressives? I'm leaning towards Sonics, as they seem well regarded, but I don't know enough to be sure. I'd like a solution that's not too stiff when I'm riding on my own, but is enough to handle the weight if my GF happens to be riding with me.

Thanks in advance!

* left from the perspective of someone sitting on the bike, not from the perspective of someone looking at the headlight

How much do you weigh?

Sonic Springs are one option (www.sonicsprings.com) Progressive Springs are another.

Sonic springs, at their recommended rate, will be pretty stiff. Progressives are just a bit stiffer than stock; like 2/3 of the way from stock to Sonic springs.

My setup (below) gets used on my commuter bike. I weigh 170#. I think it's a bit stiff still... but a vast improvement over stock for handling and braking. I used to bottom out all the time; that never happens now.

I weight 170, about the same as you. Your sig doesn't mention the brand of your springs, which are you using?

In my opinion, the correct solution is to fix the headlight bracket so that the forks will not contact the headlight when fully compressed. In general, it's never a good idea to have a bike setup so that there are clearance issues under full compression.

Other than that, there are a few fixes. If you want to be absolutely sure that the suspension cannot hit the headlight, you might be able to make some spacers that fit on the inside of the forks around the bottom of the damper rod. This mod would physically reduce your suspension travel so that the headlight doesn't hit. With that mod, you must also stiffen the springs and damping significantly so that you don't blow through your reduced travel. As you can imagine, you're making some major sacrafices to your ride quality and bump handling with this mod. Although I describe it, I'd honestly recommend it about as much as I'd recommend jumping in front of a car.

If you don't mind risking hitting the headlight again, you can install stiff springs and heavier oil, and hope that it doesn't compress all the way.

Using Sonic springs. There are other straight-rate spring brands as well; I assume they are all the same. Sonics work well and were the least expensive source.

Agreed that ideally headlight should not be in a no-clearance situation at full suspension jounce, but it sounds like the interference is very minimal (just kissing the top at full jounce.) Were this a safety item (like, say, a brakeline that's too short at full fork extension) I'd agree the root cause needs fixed. In this case, I think it's more discretionary.

I'm yet to bottom out the forks in any situation while commuting, with the upgraded springs. It used to happen every time I entered my driveway with the old ones.

Quote from: noiseguy on May 09, 2011, 06:53:58 PM...My setup (below) gets used on my commuter bike. I weigh 170#. I think it's a bit stiff still... but a vast improvement over stock for handling and braking. I used to bottom out all the time; that never happens now.

The 0.80s should be fine for your weight. You might try oil that's a little lighter, if you have 15w go to a 50/50 10w 15w mix.

Rich Desmond, you're the first one to recommend reducing the weight of oil as a remedy for this - I've heard people mention using heavier oil, so now that you've mentioned using lighter oil I'm a bit confused.

Could someone clarify what the effects are of heavier or lighter oil in the forks? Which one will help stiffen them up a bit?

I believe my bike has the stock fork oil in it, which I think is 10W (correct me if I'm wrong).

Quote from: bombshelter13 on May 10, 2011, 07:29:24 AM
Rich Desmond, you're the first one to recommend reducing the weight of oil as a remedy for this - I've heard people mention using heavier oil, so now that you've mentioned using lighter oil I'm a bit confused.

Could someone clarify what the effects are of heavier or lighter oil in the forks? Which one will help stiffen them up a bit?

I believe my bike has the stock fork oil in it, which I think is 10W (correct me if I'm wrong).

The problem with the stock forks is that the springs are too soft, and the damping is a bit light. Stiffer springs and thicker oil fix that. However, everyone's preferences are a little different, and noiseguy thought that the setup we recommended for him felt too stiff. Normally, that "stiff" feeling isn't due to springs but to the heavier oil. So backing off some on the oil weight should make the ride more comfortable for him.

I'm going to go to 15W oil and see what that does for me. I'm only 160# and I bottom out pretty easily.

If I were to get a slightly beefier spring than stock, which Sonicspring would I look at, for example?

Also, can someone explain "preload" to me? Does that indicate how much the springs compress just sitting in the tube unmounted? And spacers would add preload as well?

Going down in oil weight was just meant for me. I'm at 10W now, so that dial's set... I remind myself that I changed the front and rear suspension at the same time; changing the rear shock stiffened up the back a lot, so I don't have a clear A-B comparison for just changing out the front.

The Sonics are a vast improvement over stock, which is why they're still in there.

0.80 kg/mm are the softest straight-rate springs available from Sonic.

Progressive Spring for this bike is .58/.80 kg/mm. Note that the highest spring rate is still the lowest straight rate available.

Stock is something like 0.45 kg/mm, so any of the above is an improvement.

Here's a whole thing on front springs. RichDesmond has an account here and is associated with Sonic Springs. There's a article linked here regarding progressive vs. straight rate springs you might find interesting.

http://gstwins.com/gsboard/index.php?topic=50975.0

Oil needs to be mached to the springs - generally, to rebound damping. Hold your bike level, apply the front brake, push through the handlebars, and then let them bounce back. If the front end overshoots on the upstroke before settling to it's resting sag, you need thicker oil.

Our GS500 suspensions are not independently adjustable for rebound, but on fully adjustable bikes, having too much rebound and not enough compression will tend to cause the bike to bottom out. In those cases, softening up the rebound damping will help prevent bottoming.

Quote from: twelvepoint on May 10, 2011, 10:36:42 AM
I'm going to go to 15W oil and see what that does for me. I'm only 160# and I bottom out pretty easily.

If I were to get a slightly beefier spring than stock, which Sonicspring would I look at, for example?

Also, can someone explain "preload" to me? Does that indicate how much the springs compress just sitting in the tube unmounted? And spacers would add preload as well?

Going to 15w will help slightly with the bottoming, but at the expense of being too much rebound damping for the stock springs.
0.80s would be right for your weight.
You're correct on preload, it's the amount the spring is compressed with the fork fully extended. Preload's a tricky thing, a little bit is essential (15mm is a good ballpark figure if the spring rate is right) but too much has very bad effects on a bike's handling and even stability. It's important to realize that adding preload does not "stiffen" the spring at all, and in fact with the bike's weight on the suspension the spring is not compressed any further than it is with less preload. We have an explanation of that here:

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

Quote from: noiseguy on May 10, 2011, 10:57:45 AM
Going down in oil weight was just meant for me. I'm at 10W now, so that dial's set... I remind myself that I changed the front and rear suspension at the same time; changing the rear shock stiffened up the back a lot, so I don't have a clear A-B comparison for just changing out the front.

The Sonics are a vast improvement over stock, which is why they're still in there.

0.80 kg/mm are the softest straight-rate springs available from Sonic.

Progressive Spring for this bike is .58/.80 kg/mm. Note that the highest spring rate is still the lowest straight rate available.

Stock is something like 0.45 kg/mm, so any of the above is an improvement.

Here's a whole thing on front springs. RichDesmond has an account here and is associated with Sonic Springs. There's a article linked here regarding progressive vs. straight rate springs you might find interesting.

http://gstwins.com/gsboard/index.php?topic=50975.0

Have you measured your sag? Total sag should be about 35mm, if it's less than that trim the spacers by the amount you lack.

Rich, I just remember that I set them to the height you recommended I recall it was between 35 and 45 mm.

Not to threadjack; I'll check the rebound and see if it passes the test burning1 suggested.