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post #1 of 18 (permalink) Old 09-26-2005, 04:06 PM Thread Starter
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A little suspension help?

After Nolan's getoff at Blackhawk we started considering what my suspension needs are as I continue to do track days. I'm riding an '05 GSXR 600 and I weigh 118lb (sans gear) and about 123-125lb with full gear. The bike is completely stock.

I was running stock suspension and finally set the sag for my weight. The problem is, to get the proper rider sag (currently 31.75mm, recommended 30-35mm) I end up with static sag of 19.05mm (recommended 5-10mm). Any ways to adjust static sag while keeping the rider sag within range?

Unfortunately, I didn't get to test out the sag settings at Autobahn this weekend since it rained all day. We were planning making compression and damping adjustments once I rode for a little while - currently compression and damping are at stock settings. Just double checked them to make sure they were accurate.

Thanks in advance for any suggestions - I'm new at this, so please explain everything like you're teaching a 4-year old . I could've let Nolan post all of this stuff, but I'm trying to learn as much about my bike as possible so he doesn't have to do everying for me .

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post #2 of 18 (permalink) Old 09-26-2005, 04:28 PM
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Quote:
Originally Posted by KimF4i
After Nolan's getoff at Blackhawk we started considering what my suspension needs are as I continue to do track days. I'm riding an '05 GSXR 600 and I weigh 118lb (sans gear) and about 123-125lb with full gear. The bike is completely stock.

I was running stock suspension and finally set the sag for my weight. The problem is, to get the proper rider sag (currently 31.75mm, recommended 30-35mm) I end up with static sag of 19.05mm (recommended 5-10mm). Any ways to adjust static sag while keeping the rider sag within range?

Unfortunately, I didn't get to test out the sag settings at Autobahn this weekend since it rained all day. We were planning making compression and damping adjustments once I rode for a little while - currently compression and damping are at stock settings. Just double checked them to make sure they were accurate.

Thanks in advance for any suggestions - I'm new at this, so please explain everything like you're teaching a 4-year old . I could've let Nolan post all of this stuff, but I'm trying to learn as much about my bike as possible so he doesn't have to do everying for me .
the only way to adjust static sag is with new springs that are different rates. whenever the rider wt is out of the range of the current spring rate, the static sag will be out of wack when you set the rider sag correctly.

i think there are spring rate calculators on racetech.com and some other sites as well. google spring rate calculator and some stuff should come up.
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post #3 of 18 (permalink) Old 09-26-2005, 04:38 PM
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I wouldn't worry to much about static sag. The rider sag is where it's at or at least to start with.

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post #4 of 18 (permalink) Old 09-26-2005, 05:08 PM
 
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Quote:
Originally Posted by JRSMAIL
I wouldn't worry to much about static sag. The rider sag is where it's at or at least to start with.

That is about right. Remember that those numbers are as you said......recommended. When I set up bikes I don't look at "static" or "free" sag numbers. Just want to make sure that there is some there.
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post #5 of 18 (permalink) Old 09-26-2005, 06:55 PM
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basically-

too stiff of spring might seem soft in the initial travel because there is no pre load on it but then it will be too hard later in the travel when your leaned over, big bumps and under braking.

too soft of springs do the opposite, they'll be stiff initially because the pre load is cranked but then it will be too soft later in the travel.

Call around to the different suspension people and find out what they recomend as far as ride heights, the stock shock doesn't have adjustable height so you might have to raise or lower the fork tubes to get the proper geometry (steering angle, trail) or maybe even different sag numbers.

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post #6 of 18 (permalink) Old 09-26-2005, 07:12 PM
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Two things Kim....

One... can you send me where you got the sag ratio for your weight on the GSXR? I run the same bike on the track and would like to rectify my problems as well (now that I'm getting faster Vrroooom).

Two... Are you considering new tired for the GSXR for the track? People at BHF warned me about pushing the stock set too far....

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post #7 of 18 (permalink) Old 09-26-2005, 07:12 PM Thread Starter
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Quote:
Originally Posted by JRSMAIL
I wouldn't worry to much about static sag. The rider sag is where it's at or at least to start with.
This is the answer I was hoping for .

I'm certainly not riding fast enough yet to really push the limits of my suspension. I just want to have a good setup for my current skill set. As my skills get better (hopefully!) I will take a closer look at switching out stock components to those better suited for my weight. As long as my current setup is safe and feels comfortable I'm OK with waiting on any expensive suspension mods.

Thanks for all of the input guys!!

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post #8 of 18 (permalink) Old 09-26-2005, 07:28 PM Thread Starter
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Quote:
Originally Posted by BusaGirl
Two things Kim....

One... can you send me where you got the sag ratio for your weight on the GSXR? I run the same bike on the track and would like to rectify my problems as well (now that I'm getting faster Vrroooom).

Two... Are you considering new tired for the GSXR for the track? People at BHF warned me about pushing the stock set too far....

Nolan downloaded set-up instructions from Go Star Racing. It takes you through step-by-step instructions for setting preload (front and rear) and damping (compression and rebound). There wasn't a specific sag to weight ratio - it's all about following the steps.

You'll need a couple of friends to help and several hours of time. We were able to set the sag with the two of us 'cause Nolan can lift the rear of my bike while I measured. For rear preload you basically have to find the unloaded (rear end totally off ground), normal (bike just sitting there), and fully loaded (rider + full gear) length of the rear suspension and do calculations accordingly. Then you move onto the front preload. Go Star Racing details everything for you (much better than I just did). Make sure you have a calculator, pen, and plenty of patience!!

Oh, and you can find the stock preload, compression, and rebound settings in your owner's manual.

And to answer your second question - I switched to Michelin Pilot Powers. Since I still ride on the street, I didn't want a full-on race tire. I've been really happy with them so far. The stock tires were sacrificed in a massive smoking burnout

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post #9 of 18 (permalink) Old 09-26-2005, 07:38 PM
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Kim, here is a better way to get sag. See below.

Technicalities: Suspension and Springs

Beyond nuts and bolts

By Paul Thede

Figure 1

What's all this ruckus about suspension these days? It seems everyone is clued in that suspension setup can be a key to riding fast and safely, but how do you do it? No matter what shock or fork you have, they all require proper adjustment to work to their maximum potential. Suspension tuning isn't rocket science, and if you follow step-by-step procedures you can make remarkable improvements in your bike's handling characteristics.
Figure 2

The first step to setting up any bike is to set the spring sag and determine if you have the correct-rate springs. Spring sag is the amount the springs compress between fully topped out and fully loaded with the rider on board in riding position. It is also referred to as static ride height or static sag. My company, Race Tech, (909/594-7755) has an advanced method of checking spring sag that I'll describe.
If you've ever measured sag before, you may have noticed that if you check it three or four times, you can get three or four different numbers without changing anything. We'll tell you why this occurs and how to handle it.

Rear end

Step 1: Extend the suspension completely by getting the wheel off the ground. It helps to have a few friends around. On bikes with sidestands the bike can usually be carefully rocked up on the stand to unload the suspension. Most race stands will not work because the suspension will still be loaded by resting on the swingarm rather than the wheel. Measure the distance from the axle vertically to some point on the chassis (metric figures are easiest and more precise; Figure 1). Mark this reference point because you'll need to refer to it again. This measurement is L1. If the measurement is not exactly vertical the sag numbers will be inaccurate (too low).

Step 2: Take the bike off the stand and put the rider on board in riding position. Have a third person balance the bike from the front. If accuracy is important to you, you must take friction of the linkage into account. This is where our procedure is different: We take two additional measurements. First, push down on the rear end about 25mm (1") and let it extend very slowly. Where it stops, measure the distance between the axle and the mark on the chassis again. If there were no drag in the linkage the bike would come up a little further. It's important that you do not bounce! This measurement is L2. Step 3: Have your assistant lift up on the rear of the bike about 25mm and let it down very slowly. Where it stops, measure it. If there were no drag it would drop a little further. Remember, don't bounce! This measurement is L3.

Step 4: The spring sag is in the middle of these two measurements. In fact, if there were no drag in the linkage, L2 and L3 would be the same. To get the actual sag figure you find the midpoint by averaging the two numbers and subtracting them from the fully extended measurement L1: static spring sag = L1 - [(L2 + L3) / 2]. Step 5: Adjust the preload with whatever method applies to your bike. Spring collars are common, and some benefit from the use of special tools. In a pinch you can use a blunt chisel to unlock the collars and turn the main adjusting collar. If you have too much sag you need more preload; if you have too little sag you need less preload. For roadrace bikes, rear sag is typically 25 to 30mm. Street riders usually use 30 to 35mm. Bikes set up for the track are a compromise when ridden on the street. The firmer settings commonly used on the track are generally not recommended (or desirable) for road work.

You might notice the Sag Master measuring tool (available from Race Tech) in the pictures. It's a special tool made to assist you in measuring sag by allowing you to read sag directly without subtracting. It can also be used as a standard tape measure. Measuring front-end sag is very similar to the rear. However, it's much more critical to take seal drag into account on the front end because it is more pronounced.

Ffront end

Step 1: Extend the fork completely and measure from the wiper (the dust seal atop the slider) to the bottom of the triple clamp (or lower fork casting on inverted forks; Figure 2). This measurement is L1.

Step 2: Take the bike off the sidestand, and put the rider on board in riding position. Get an assistant to balance the bike from the rear, then push down on the front end and let it extend very slowly. Where it stops, measure the distance between the wiper and the bottom of the triple clamp again. Do not bounce. This measurement is L2.

Step 3: Lift up on the front end and let it drop very slowly. Where it stops, measure again. Don't bounce. This measurement is L3. Once again, L2 and L3 are different due to stiction or drag in the seals and bushings, which is particularly high for telescopic front ends.

Step 4: Just as with the front, halfway between L2 and L3 is where the sag would be with no drag or stiction. Therefore L2 and L3 must be averaged and subtracted from L1 to calculate true spring sag: static spring sag = L1 - [(L2 + L3) / 2]. Step 5: To adjust sag use the preload adjusters, if available, or vary the length of the preload spacers inside the fork.

Street bikes run between 25 and 33 percent of their total travel, which equates to 30 to 35mm. Roadrace bikes usually run between 25 and 30mm. This method of checking sag and taking stiction into account also allows you to check the drag of the linkage and seals. It follows that the greater the difference between the measurements (pushing down and pulling up), the worse the stiction. A good linkage (rear sag) has less than 3mm (0.12") difference, and a bad one has more than 10mm (0.39"). Good forks have less than 15mm difference, and we've seen forks with more than 50mm. (Gee, I wonder why they're harsh?) It's important to stress that there is no magic number. If you like the feel of the bike with less or more sag than these guidelines, great. Your personal sag and front-to-rear sag bias will depend on chassis geometry, track or road conditions, tire selection and rider weight and riding preference.

Using different sag front and rear will have a huge effect on steering characteristics. More sag on the front or less sag on the rear will make the bike turn more quickly. Less sag on the front or more sag on the rear will make the bike turn more slowly. Increasing sag will also decrease bottoming resistance, though spring rate has a bigger effect than sag. Racers often use less sag to keep the bike higher off the ground for more ground clearance, and since roadracers work with braking and steering forces greater than we see on the street, they require a stiffer setup. Of course, setting spring sag is only the first step of dialing in your suspension, so stay tuned for future articles on spring rates and damping.

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post #10 of 18 (permalink) Old 09-26-2005, 07:42 PM
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20 mm of free sag is not an issue for the front forks.

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post #11 of 18 (permalink) Old 09-26-2005, 08:26 PM
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Thank you for the information! Good stuff! I think I'm going with Diablo's ... maybe it will be my birthday present from me to me!

Quote:
Originally Posted by KimF4i
The stock tires were sacrificed in a massive smoking burnout
! I would have loved to see the yellow girl smoke!

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post #12 of 18 (permalink) Old 09-26-2005, 09:17 PM
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Make sure the person who is taking the measurments knows what they are doing.

If you have between 30 & 35 mm front and rear you're at a good reference point. Thats rule of thumb for every newer model sport bike.

I have spent more time than you would believe getting my suspension rite on my SV. But I started rite where you are at. I have had my front forks apart 150 times to get them where they are at messing with fork oil, preload, damping, rebound, EVERYTHING!

Once the bike starts doing funny things underneath you or you are fighting it to go faster and it won't let you, then you probably need to mess with suspension.

The bikes the MOTO GP guys and AMA guys are riding if you look close when they are racing, are still doing funny, wiggly, nasty things underneath them, and they are the pro's, and have pro mechanics.

Keep good tires on the bike and check your tire pressure EARLY IN THE MORNING BEFORE YOU RIDE, stay loose on the bars, look through those corners, toes on the pegs and relaxed. Ride your bike and have fun.

NEVER NEVER NEVER NEVER RIDE YOUR BIKE ON THE TRACK HARD WITH TIRES YOU "THINK" MITE NOT BE OK.

If you stopped to think... Hmmmmmm... may be I need new tires, YOU DO!

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post #13 of 18 (permalink) Old 09-26-2005, 09:33 PM

 
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Great advice from a damn good rider.

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post #14 of 18 (permalink) Old 09-26-2005, 10:44 PM
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should've put that in my earlier post
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post #15 of 18 (permalink) Old 09-27-2005, 08:22 PM
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Quote:
Originally Posted by BusaGirl
Two... Are you considering new tires for the GSXR for the track? People at BHF warned me about pushing the stock set too far....
Fast racers like Dano put on two to three sets of tires each weekend, so you can get race take offs for a great deal, plus its only $20 to have the tires put on and balanced at the track.

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post #16 of 18 (permalink) Old 09-29-2005, 03:19 PM
 
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Quote:
Originally Posted by ClevisR6
the only way to adjust static sag is with new springs that are different rates. whenever the rider wt is out of the range of the current spring rate, the static sag will be out of wack when you set the rider sag correctly.

i think there are spring rate calculators on racetech.com and some other sites as well. google spring rate calculator and some stuff should come up.
The rate for springs you're looking for depands on your riding style. For example, I'm 5.8 145lb and RaceTech calculator said I need 0.85 spring. It was way to soft on heavy breaking and I went with 0.90
Good Luck
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post #17 of 18 (permalink) Old 09-29-2005, 03:32 PM
 
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Quote:
Originally Posted by KimF4i
This is the answer I was hoping for .

I'm certainly not riding fast enough yet to really push the limits of my suspension. I just want to have a good setup for my current skill set. As my skills get better (hopefully!) I will take a closer look at switching out stock components to those better suited for my weight. As long as my current setup is safe and feels comfortable I'm OK with waiting on any expensive suspension mods.

Thanks for all of the input guys!!
Common mistake....It has nothing to do with pushing the limits. You get better, more comfortable and controlable feel of the bike at any speeds. The suspension is the first thing you wanna take care of. And you wanna choose the best stuff you can afford.
I wouldn't go with RaceTech or anything like that. All they do is selling the products. And they don't care how you''re gonna put it in. From my experience, that is the most important part.
Stop by at any CCS round or contact suspension guys to get it fully installed and diled in @
Lithium Motorsports (Ryan) 712-546-7747
or
TrackSide Engenering (Ed) 414-453-6720
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post #18 of 18 (permalink) Old 09-29-2005, 03:56 PM
 
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Quote:
Originally Posted by racingxtc7
Fast racers like Dano put on two to three sets of tires each weekend, so you can get race take offs for a great deal, plus its only $20 to have the tires put on and balanced at the track.
I've got plenty Dunlop take offs. Some of them are in very good shape. I use different sets for practice and races. Sometimes I only put a few sprint races on them. Dirt cheap!!!!! Let me know.
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