First ride and question about sag

[Rob F]

I had my new to me 2007 out for my first ride and gotta say it's just like you guys on the forum have described.
I would like to dial in the rear suspension and am trying to wrap my head around on how to go about doing this.
I have studied the "Sag" concept and half ways understand it. Take the 2 measurements and subtract and proper sag should be equivalent to 1/3 of wheel travel.
I know lifting the bike with a jack gets the extended height but how do you get the compressed height to determine what total wheel travel is?
Another issue is that the previous owner had installed a Progressive 465 with RAP but 1" lower than stock #465-5014B. I found the specs for the shock extended and compressed measurements but would be tricky to measure 1/3 of that at the shock travel while sitting on the bike.
Any insights?

 

[Fawlty]

@dduelin is very knowledgeable about all this. I am sure he will be along to advise and assist you. Good luck.

 

[Al st1100]

Here is an article that explanes it. . put a hose clamp or a wire tie loosely around the fork, while wheel/forks are up,tight enough so it slides but does not fall. put the bike down, sit on it, the back up and take your measurments. stock travel on a 1300 front is 150 mm rear is 120mm

 

[Larry Fine]

I use a simple gauge as to the best rear ride height: required steering effort.

If the bike resists leaning in response to counter-steering force, raise the rear.

If it falls over too easily in response to counter-steering force, lower the rear.

Doing this automatically compensates for your weight and any other factors.

I adjusted my rear suspension using this guide, and my ST steers effortlessly.

 

[Rob F]

I was more concerned about the rear shock. I just did an oil change in the front using 10w and filled to the height stated in the SM.
Just trying to figure out the rear shock adjustment as it is a 1" shorter than oem.
I think that have come up with a way to measure. According to specs the 1" shorter 465 has only 86% of travel ( 42mm) compared to the stock travel ( 49mm).. If i set it so it has 28mm of travel left when i am on, that should be about right

 

[Rob F]

I use a simple gauge as to the best rear ride height: required steering effort.

If the bike resists leaning in response to counter-steering force, raise the rear.

If it falls over too easily in response to counter-steering force, lower the rear.

Doing this automatically compensates for your weight and any other actors.

I adjusted my rear suspension using this guide, and my ST steers effortlessly.

I like your suggestion as it will save me a lot of Math calculations. Just trying to find the base line for now.

 

[Larry Fine]

I like your suggestion as it will save me a lot of Math calculations. Just trying to find the base line for now.

I look at it this way:

I am not going to set my suspension contrary to best handling to satisfy any rules-of-thumb.

After all, if best handling is the goal, why not use it as the guideline? And yes, no math required.

 

[dduelin]

The primary reason behind measuring and setting rear sag to target is to get the shock operating in the middle third of its range. After setting preload to sag 25-33% of total available travel under your normal riding weight enough travel is left to absorb most bumps and also to not top out when the bike rides over a hole or dip. Next the relationship between sag under weight of unladen bike and bike loaded with rider and normal cargo tells whether or not the spring rate is correct for the rider. I believe both of these are worthy goals even if some measuring and math is involved. We can help with the math but you need a wheel chock or at least a helper for the sag measurements. Properly set up suspensions are safer and handle better. However, lowering just the rear has changed the original steering geometry and compromises will have to be made because only the shock is shortened. Lowering the stock forks can make up about 10 mm of the 25.4 lost. Lowering the rear slows steering response but you might like it. There really isn’t a choice.

if the rear suspension travel is now approximately 106 mm with the Progressive shock try and set sag between 27 and 35 mm under your riding weight.

 

[JohnK]

I agree a little effort on the measure assures a better handling bike and starting with tech measures. - Stock or modified it’s worth the effort to know the travel of front and rear.
Doing a race tech spring mod. I am going to pay attention to the finer adjustment afterwards with the counter steer test. That seems to me the best way to find ones happy place of which is different for all of us.

 

[Rob F]

The primary reason behind measuring and setting rear sag to target is to get the shock operating in the middle third of its range. After setting preload to sag 25-33% of total available travel under your normal riding weight enough travel is left to absorb most bumps and also to not top out when the bike rides over a hole or dip. Next the relationship between sag under weight of unladen bike and bike loaded with rider and normal cargo tells whether or not the spring rate is correct for the rider. I believe both of these are worthy goals even if some measuring and math is involved. We can help with the math but you need a wheel chock or at least a helper for the sag measurements. Properly set up suspensions are safer and handle better. However, lowering just the rear has changed the original steering geometry and compromises will have to be made because only the shock is shortened. Lowering the stock forks can make up about 10 mm of the 25.4 lost. Lowering the rear slows steering response but you might like it. There really isn’t a choice.

if the rear suspension travel is now approximately 106 mm with the Progressive shock try and set sag between 27 and 35 mm under your riding weight.

Ok i am going to ask a real dumb question but it has eluded me all along.
I get the concept of setting at middle third. How do you determine the total wheel travel in order to cipher that measurement ? I know that jacking up the bike gives you the extended spec but how is the retracted spec achieved ( from axle nut to a fixed point)? I tried to measure the exposed chrome of the shock rod but can't get in past the spring to get a measurement. I suppose setting a 1800lb Hereford on the back would do it but i'm not up for that.
I am good with math if i have all the figures. So no help needed there but i do appreciate your offer.

 

[dduelin]

The shock sets the limit of rear suspension travel. Stock travel is 123 mm. If yours is 86% of that the travel rounds to 106 mm. 25% and 33% of that sets a range to shoot for.

If you get the distance between a fixed point above the axle nut and the nut at full extension on the center stand that is D1. Then place the bike on its wheels. Remove all adjustable preload. Find a way to measure that fixed point to axle nut with you on the bike to get D2. Example might be D1 is 200 mm. D2 is 170. 200-170= D3 (rider sag) is 30 mm. Good, right in the middle with adjustments left for adding a passenger or to tune steering “feel” that Larry mentioned. Add preload if necessary to get D1 - D2 in the targeted range. After we get rider sag in target range measure sag again with no rider weight on the bike. This is static or free sag. It should be 5 to 10 mm. If 0 to 5 mm the spring is too soft - it took some adjusting preload on the spring to get rider sag in range but with no rider the spring tops out.

On my ST I stuck a piece of masking tape on the stock passenger grab handle. I placed a mark on the outside edge of the handle. I used a piece of window blind batten to measure distances. A dot of Sharpie marker on the batten where it crosses the mark on the tape mark marks the D figures. This allowed my wife to easily help me ~ there was no interpreting the tape measure markings. Tick mark, tick mark for the assistant leaving me to use a tape on batten at leisure for accuracy. I could do it alone later with a little thought. I have a wheel chock bolted to the garage floor. With a bike held vertically in place I sat on the bike backwards and made my own tick marks. Taping a batten to the fork slider or swing arm gets the measurement against a known fixed point to get measurements without help. They aren’t as accurate but good enough for my amateur purposes.

 

[SMSW]

I'd suggest taking 3 measurements each time and averaging them. Stiction - static friction will yield somewhat different numbers each time you measure sag, When I did my bike, I lifted the unloaded bike slightly, and let it drop to its unloaded position held up by the suspension. That took two people to hold the bike upright without (or while trying to NOT) influencing the sag. In fact, I did three tries for each of Dave's measurements, and then did a second set of 3 that I called Trial 2. My individual measurements might have varied as much as 12 mm, from highest to lowest but the averages of the numbers yielded Trial 1 and Trial 2 with a max difference of 2.3mm for one measurement and an average sag for the loaded bike of less than 1mm (this is Trial 1 compared to Trial 2).

Why am I suggesting you complicate matters? Because years ago (for sure more than 50), in a school lab, we were given blocks of various materials and a ruler, a metal rule, calipers, and micrometers. The object was to measure each item 3 times - pick up item, pick up measuring device, measure, put it all down and repeat. Big surprise to us kids was we got different numbers even with the calipers and micrometer on supposedly single size hunks of metal. They call this metrology - the science of measurement. Averaging several measurements (carefully taken) will minimize your errors. You do have to try to be consistent. Sloppy work yields sloppy results.

 

[dduelin]

I'd suggest taking 3 measurements each time and averaging them. Stiction - static friction will yield somewhat different numbers each time you measure sag, When I did my bike, I lifted the unloaded bike slightly, and let it drop to its unloaded position held up by the suspension. That took two people to hold the bike upright without (or while trying to NOT) influencing the sag. In fact, I did three tries for each of Dave's measurements, and then did a second set of 3 that I called Trial 2. My individual measurements might have varied as much as 12 mm, from highest to lowest but the averages of the numbers yielded Trial 1 and Trial 2 with a max difference of 2.3mm for one measurement and an average sag for the loaded bike of less than 1mm (this is Trial 1 compared to Trial 2).

Why am I suggesting you complicate matters? Because years ago (for sure more than 50), in a school lab, we were given blocks of various materials and a ruler, a metal rule, calipers, and micrometers. The object was to measure each item 3 times - pick up item, pick up measuring device, measure, put it all down and repeat. Big surprise to us kids was we got different numbers even with the calipers and micrometer on supposedly single size hunks of metal. They call this metrology - the science of measurement. Averaging several measurements (carefully taken) will minimize your errors. You do have to try to be consistent. Sloppy work yields sloppy results.

Yes, I agree. I lift and settle and take multiple measurements to get an average. I typed the reply quickly on an iPhone while waiting on someone to arrive and cut it to a minimum of text.

 

[Rob F]

The shock sets the limit of rear suspension travel. Stock travel is 123 mm. If yours is 86% of that the travel rounds to 106 mm. 25% and 33% of that sets a range to shoot for.

If you get the distance between a fixed point above the axle nut and the nut at full extension on the center stand that is D1. Then place the bike on its wheels. Remove all adjustable preload. Find a way to measure that fixed point to axle nut with you on the bike to get D2. Example might be D1 is 200 mm. D2 is 170. 200-170= D3 (rider sag) is 30 mm. Good, right in the middle with adjustments left for adding a passenger or to tune steering “feel” that Larry mentioned. Add preload if necessary to get D1 - D2 in the targeted range. After we get rider sag in target range measure sag again with no rider weight on the bike. This is static or free sag. It should be 5 to 10 mm. If 0 to 5 mm the spring is too soft - it took some adjusting preload on the spring to get rider sag in range but with no rider the spring tops out.

On my ST I stuck a piece of masking tape on the stock passenger grab handle. I placed a mark on the outside edge of the handle. I used a piece of window blind batten to measure distances. A dot of Sharpie marker on the batten where it crosses the mark on the tape mark marks the D figures. This allowed my wife to easily help me ~ there was no interpreting the tape measure markings. Tick mark, tick mark for the assistant leaving me to use a tape on batten at leisure for accuracy. I could do it alone later with a little thought. I have a wheel chock bolted to the garage floor. With a bike held vertically in place I sat on the bike backwards and made my own tick marks. Taping a batten to the fork slider or swing arm gets the measurement against a known fixed point to get measurements without help. They aren’t as accurate but good enough for my amateur purposes.

Ok, thanks for that and will give it a go whenever the weather smartens up around here. Maybe July? ( snowing at the moment)

 

[SMSW]

Ok, thanks for that and will give it a go whenever the weather smartens up around here. Maybe July? ( snowing at the moment)

We have smart weather down here. Sometimes its too dang smart.