Setting Proper Sag

[dlaing]

From SlowKitty's thread on how his or her bike handles, I thought the points that Ratchet brought up are important and deserve there own thread before it distracts from helping slowkitty find a solution.

 

SNIP

As for mere mortals , I find the vast riding population not only needs guidelines on setting sags, but way too many often suffer terrific ride and handling problems without them.

 

So after studying it for many many years and mucking about with my suspension and upgrading it substantially over the years (with very positive "real world" results!), here's wot I came up with for "general purpose" riding for riders of all weights. For further clarification, I believe this applies to MOST riders, from those simply doing the "comfortable Sunday afternoon riding" to those doing the most aggressive "sporting" riding -- but not necessarily "road racing", and certainly not track competition:

 

Assume we are talking about a V11, where both front and rear wheel travel are 120 mm.

 

The difference between laden and unladen sag measurements (both front and rear) should ideally be 18 mm, +/- 5 mm for general purpose road work.

 

If the difference is LESS THAN 13 mm, the springs are too stiff.

 

If the diff. is GREATER THAN 23 mm, the springs are too weak.

 

FWIW, I sat on Todd's LM. I reckon he's got his sag difference set around 6-8 mm.

 

I reckon Grandma would much prefer a 30 mm difference.

 

Disclaimers and caveats abound, and of course YMMV depending on variables too numerous to mention.

 

This is intended to be a general guide, and all strenuous objections are welcome -- but by all means, please bring a logical, rational basis for your argument -- and direct experience is a big plus!

Your

Mileage

May

Vary

 

 

I replied in that thread:

 

Assume we are talking about a V11, where both front and rear wheel travel are 120 mm.

 

The difference between laden and unladen sag measurements (both front and rear) should ideally be 18 mm, +/- 5 mm for general purpose road work.

 

If the difference is LESS THAN 13 mm, the springs are too stiff.

 

If the diff. is GREATER THAN 23 mm, the springs are too weak.

 

FWIW, I sat on Todd's LM. I reckon he's got his sag difference set around 6-8 mm.

 

I reckon Grandma would much prefer a 30 mm difference.

 

Disclaimers and caveats abound, and of course YMMV depending on variables to numerous to mention.

 

This is intended to be a general guide, and all strenuous objections are welcome -- but by all means, please bring a logical, rational basis for your argument -- and direct experience is a big plus!

Your

Mileage

May

Vary

From my experience, the 18mm target sounds like a good target for the rear with a Sachs shock.

I think lighter rider may need less and heavier riders more because of the ratio of the bike to rider weight, but it is not a big difference.

I think the front springs should provide less sag difference than the rear spring because of the need for the front suspension to handle bottoming.

Ohlins suggests

Without rider:

Rear: Road and Track 5-10 mm

Front: Road and Track 25-30 mm

With rider:

Rear: Road and Track 30-40 mm

Front: Road and Track 35-48 mm

Notice they recommend more difference in the rear, but then again the rear wheel travel is about 140mm. Other experts generally recommend firmer springs and less sag than Ohlins does, and I agree with them, up to a point.

I think if you take the tighter Ohlins numbers you would be doing very well:

Without rider:

Rear: Road and Track 10 mm

Front: Road and Track 25-30 mm

With rider:

Rear: Road and Track 30 mm

Front: Road and Track 35 mm

For a difference of about

Rear: 20 mm

Front: 5-10 mm

 

What you set your sag to should also take into consideration geometry.

I find that a high rear and a low front make the bike handle better.

Some of that can be adjusted by moving the triple clamps down the forks, but more sag in the forks than at the rear is a good thing.

My front is 26mm/36mm with a difference of 10mm. I think I need a stiffer spring up front, so I guess for my front the 18mm±5 does not meet my needs, and I need a little less than 10mm difference.

But my rear is 6mm/31mm for a difference of 25mm. I think I need a stiffer, but more importantly a more progressive rear spring. Probably 8mm/28mm would be about ideal for me. But my Penske rear suspension is probably about 136mm of travel as opposed to the 120mm Sachs. If I was using the Sachs, 18mm rear would be just about perfect.

[badmotogoozer]

How to check sag:

[dlaing]

Ratchet Replied

Things that make me go, "Hm": knownothing.gif

 

Interesting feedback, Dave. Let's consider:

QUOTE(dlaing @ Jul 17 2007, 07:01 AM) *

 

I think lighter rider may need less and heavier riders more because of the ratio of the bike to rider weight, but it is not a big difference.

 

Hm. So you're saying a 150 lb. rider would need less sag difference, or a greater spring rate relative to the combined vehicle and rider weight of a 250 lb. rider? I can't disagree more. The difference in laden and unladen sags is related to spring rate and overall laden weight alone -- regardless of the ratio of rider weight to overall weight. knownothing.gif

QUOTE(dlaing @ Jul 17 2007, 07:01 AM) *

 

I think the front springs should provide less sag difference than the rear spring because of the need for the front suspension to handle bottoming.

Hm. I don't recall in recent memory (or ever, for that matter) any air-spring assisted fork bottoming, unless it's suffered a blown seal. Do you? I believe that with a rising rate air spring assisted fork, this is for all practical purposes nearly impossible enough to forget about under normal circumstances, barring something like a crash. My zip-tied forks (for indication of extent of compression travel) on many motorcycles I've owned tell me it's never happened to me, despite some fairly substantial whomping loads on the fork. ohmy.gif Is there some reason you believe that "the need to handle bottoming" would be more of a concern for a fork than for the rear shock -- and that this should be a reason to target unbalanced front/rear sag differences?

QUOTE(dlaing @ Jul 17 2007, 07:01 AM) *

 

What you set your sag to should also take into consideration geometry.

I find that a high rear and a low front make the bike handle better.

 

Hm. What makes a high rear "high" and a low front "low"? Relative to what? What kind of geometry are you referring to here that would make the handling "better"? Relative to what? How long is a string? knownothing.gif

QUOTE(dlaing @ Jul 17 2007, 07:01 AM) *

 

Some of that can be adjusted by moving the triple clamps down the forks, but more sag in the forks than at the rear is a good thing.

 

Hm. A "good thing" based on Ohlins specs, a flying guess, a stab in the dark, or what? knownothing.gif Generally, I disagree with this as a blanket statement, but that's just me.

 

NOTE: The sag difference is wot we've been talking about here. It might be important to understand that you can increase or decrease both laden and unladen sags while keeping the difference between them the same. wink.gif

QUOTE(dlaing @ Jul 17 2007, 07:01 AM) *

 

My front is 26mm/36mm with a difference of 10mm. I think I need a stiffer spring up front, so I guess for my front the 18mm±5 does not meet my needs, and I need a little less than 10mm difference.

 

Hm. To each his own. But if you go to stiffer fork springs with an already relatively "tight" 10 mm sag difference on your Ohlins fork, I would predict a Todd Eagan-esque "rock hard" ride that would (at least in my case) tend to knock my back teeth loose on many of the favorite roads I ride, and force me to take pain killers with me. I ain't interested in that, and I suspect that somewhere around 99% of riders (given the choice -- especially after sampling) would agree. But o' course, I can only speak for myself. . .

QUOTE(dlaing @ Jul 17 2007, 07:01 AM) *

 

But my rear is 6mm/31mm for a difference of 25mm. I think I need a stiffer, but more importantly a more progressive rear spring. Probably 8mm/28mm would be about ideal for me. But my Penske rear suspension is probably about 136mm of travel as opposed to the 120mm Sachs. If I was using the Sachs, 18mm rear would be just about perfect.

 

Hm. I consider progressive vs. straight rate entirely transparent relative to rates, and therefore sag differences. But that's just me.

 

Hm (Part VII). I would tend to agree that with a 25 mm difference, it would seem that not only are you a little soft in the rear by rate, but that this would not work well with such a relatively stiffly sprung fork with just a 10 mm difference. IMHO the most balanced suspension has sag differences front and rear fairly closely matched. And yet you want to go even stiffer on the fork springs? knownothing.gif

 

So the manufacturer of the component would make a difference relative to the sag difference guideline? Based on what? Travel? IMHO a difference in travel from 120 mm to 136 mm is so trivial relative to the dimensions we're talking about that your 2 mm difference is hardly significant.

 

Just another thought that seems to fit here:

 

Now it seems to me that you and many others no doubt, believe that Ohlins suspension components represent "the pinnacle" of suspension development for motorcycles. I would not deny that they are very good components. But neither would I ever tend to believe that Ohlins or any other manufacturer owns the "benchmark" for some kind of a fictious conditio sine qua non in suspension. IMHO, despite all the groupthink and hype that tends to surround and drive the popularity of such items, such perfection does not, cannot, and never will exist. As I've mentioned before, when you're dealing with a motorcycle that's in the neighborhood of 150 lbs. overweight compared to many of its displacement, considerably underpowered relative to many of half its displacement, with a walloping 40 lb. rear wheel hub assembly with a transmission in it, unfavorable fore-aft balance, a relatively flexible spine frame, etc. . . when it comes to the design of the current crop of "high zoot" suspension components, such considerations become a "great equalizer" among suspension components on the Guzzi, making subtle differences in their design (if not the overall basic function) of suspension components that much less of an important differentiator.

 

BAA, TJM & YMMV

 

How to check sag:

I warned there would be diatribe!

[dlaing]

Things that make me go, "Hm": knownothing.gif

 

Interesting feedback, Dave. Let's consider:

QUOTE(dlaing @ Jul 17 2007, 07:01 AM) *

 

I think lighter rider may need less and heavier riders more because of the ratio of the bike to rider weight, but it is not a big difference.

 

Hm. So you're saying a 150 lb. rider would need less sag difference, or a greater spring rate relative to the combined vehicle and rider weight of a 250 lb. rider? I can't disagree more. The difference in laden and unladen sags is related to spring rate and overall laden weight alone -- regardless of the ratio of rider weight to overall weight. knownothing.gif

The spring rate should match the needs of the combined weight of bike and rider.

Selecting a spring with an 18mm deflection from rider weight is only matching the rider's weight and not the bike's

Selecting a spring based on bike and rider combined sag also does not match the bike and rider's combined weight because the preload throws the numbers off.

So, using a fixed target does not work perfectly.

[dlaing]

QUOTE(dlaing @ Jul 17 2007, 07:01 AM) *

 

I think the front springs should provide less sag difference than the rear spring because of the need for the front suspension to handle bottoming.

Hm. I don't recall in recent memory (or ever, for that matter) any air-spring assisted fork bottoming, unless it's suffered a blown seal. Do you? I believe that with a rising rate air spring assisted fork, this is for all practical purposes nearly impossible enough to forget about under normal circumstances, barring something like a crash. My zip-tied forks (for indication of extent of compression travel) on many motorcycles I've owned tell me it's never happened to me, despite some fairly substantial whomping loads on the fork. ohmy.gif Is there some reason you believe that "the need to handle bottoming" would be more of a concern for a fork than for the rear shock -- and that this should be a reason to target unbalanced front/rear sag differences?

Excellent question!

I don't know if I have a good answer. Here is an attempt, but if someone else could help answer, please do!

The progressive action of the air spring does help negate the need for less rider only sag in the front than the back.

The front needs less rider only sag because of what happens when the weight shifts forward to the front during breaking. During acceleration the weight is also shifted to the rear, but for complex yet obvious reasons any bottoming of rear suspension during acceleration is less critical to stability than bottoming of forks during braking.

 

 

QUOTE(dlaing @ Jul 17 2007, 07:01 AM) *

 

What you set your sag to should also take into consideration geometry.

I find that a high rear and a low front make the bike handle better.

 

Hm. What makes a high rear "high" and a low front "low"? Relative to what? What kind of geometry are you referring to here that would make the handling "better"? Relative to what? How long is a string? knownothing.gif

I was thinking relative to how it came when purchased.

As far as making the bike handle better, I think it is possible the front cannot go too low, within the limits of fender and wheel risking contact.

As for the rear, again, I am not sure it can go too high, although I would not push it because of shaft angles. For me, I am happy with it being higher in the rear than how it was when I bought it and lower in the front.

I have not gone lower in front because I have a problem of sliding forward too much in the Corbin saddle. Ergonomics trumps handling

 

 

QUOTE(dlaing @ Jul 17 2007, 07:01 AM) *

 

Some of that can be adjusted by moving the triple clamps down the forks, but more sag in the forks than at the rear is a good thing.

 

Hm. A "good thing" based on Ohlins specs, a flying guess, a stab in the dark, or what? knownothing.gif Generally, I disagree with this as a blanket statement, but that's just me.

 

NOTE: The sag difference is wot we've been talking about here. It might be important to understand that you can increase or decrease both laden and unladen sags while keeping the difference between them the same. wink.gif

Based on my limited amateur road riding experience and Ohlins specs and general sag recommendations from various experts.

By saying, "more sag in the forks" I meant and should have said, unladen sag.

Yes we are discussing rider only sag, but it all interacts, and is all important.

[BrianG]

I find that I prefer 15% unladen and 30% laden sag at both ends. I had tried the stiffer front idea mentioned but found that the bike didn't absorb bumps (when heeled over hard) symmetrically. I found that the mis-matched spring rates caused a pitch moment that I found disconcerting.

 

If I find the front end bottoming I raise the oil level or add a little compression damping (if possible). You do have to be a bit cautious with raising the oil level. Too much will give you hydro-lock bottoming of the fork.

[dlaing]

QUOTE(dlaing @ Jul 17 2007, 07:01 AM) *

 

My front is 26mm/36mm with a difference of 10mm. I think I need a stiffer spring up front, so I guess for my front the 18mm±5 does not meet my needs, and I need a little less than 10mm difference.

 

Hm. To each his own. But if you go to stiffer fork springs with an already relatively "tight" 10 mm sag difference on your Ohlins fork, I would predict a Todd Eagan-esque "rock hard" ride that would (at least in my case) tend to knock my back teeth loose on many of the favorite roads I ride, and force me to take pain killers with me. I ain't interested in that, and I suspect that somewhere around 99% of riders (given the choice -- especially after sampling) would agree. But o' course, I can only speak for myself. . .

10mm rider only sag might be brutal using Marzocchi shocks and factory recommended compression settings

[dlaing]

 

QUOTE(dlaing @ Jul 17 2007, 07:01 AM) *

 

But my rear is 6mm/31mm for a difference of 25mm. I think I need a stiffer, but more importantly a more progressive rear spring. Probably 8mm/28mm would be about ideal for me. But my Penske rear suspension is probably about 136mm of travel as opposed to the 120mm Sachs. If I was using the Sachs, 18mm rear would be just about perfect.

 

Hm. I consider progressive vs. straight rate entirely transparent relative to rates, and therefore sag differences. But that's just me.

 

Hm (Part VII). I would tend to agree that with a 25 mm difference, it would seem that not only are you a little soft in the rear by rate, but that this would not work well with such a relatively stiffly sprung fork with just a 10 mm difference. IMHO the most balanced suspension has sag differences front and rear fairly closely matched. And yet you want to go even stiffer on the fork springs? knownothing.gif

 

Yes, but you will notice I also said I would go firmer and more progressive at the rear.

This would balance better with the front.

 

QUOTE(dlaing @ Jul 17 2007, 07:01 AM) *

 

My front is 26mm/36mm with a difference of 10mm. I think I need a stiffer spring up front, so I guess for my front the 18mm±5 does not meet my needs, and I need a little less than 10mm difference.

 

Hm. To each his own. But if you go to stiffer fork springs with an already relatively "tight" 10 mm sag difference on your Ohlins fork, I would predict a Todd Eagan-esque "rock hard" ride that would (at least in my case) tend to knock my back teeth loose on many of the favorite roads I ride, and force me to take pain killers with me. I ain't interested in that, and I suspect that somewhere around 99% of riders (given the choice -- especially after sampling) would agree. But o' course, I can only speak for myself. . .

QUOTE(dlaing @ Jul 17 2007, 07:01 AM) *

So the manufacturer of the component would make a difference relative to the sag difference guideline? Based on what? Travel? IMHO a difference in travel from 120 mm to 136 mm is so trivial relative to the dimensions we're talking about that your 2 mm difference is hardly significant.

Travel is relevant. I believe it should translate proportionately, so 120mm to 136mm is the same ratio as 18mm to 20.4mm, a difference of 2.4mm. But yah, certainly I am not going to lose sleep over 2mm, but the math is simple. 120mm divided by your magic 18 equals 6.66666666666666. (Is Ratchet guided by Satanic voices in his head? Just Kidding! )

 

Just another thought that seems to fit here:

 

Now it seems to me that you and many others no doubt, believe that Ohlins suspension components represent "the pinnacle" of suspension development for motorcycles. I would not deny that they are very good components. But neither would I ever tend to believe that Ohlins or any other manufacturer owns the "benchmark" for some kind of a fictious conditio sine qua non in suspension. IMHO, despite all the groupthink and hype that tends to surround and drive the popularity of such items, such perfection does not, cannot, and never will exist. As I've mentioned before, when you're dealing with a motorcycle that's in the neighborhood of 150 lbs. overweight compared to many of its displacement, considerably underpowered relative to many of half its displacement, with a walloping 40 lb. rear wheel hub assembly with a transmission in it, unfavorable fore-aft balance, a relatively flexible spine frame, etc. . . when it comes to the design of the current crop of "high zoot" suspension components, such considerations become a "great equalizer" among suspension components on the Guzzi, making subtle differences in their design (if not the overall basic function) of suspension components that much less of an important differentiator.

 

BAA, TJM & YMMV

Sounds good to me!

Perfection is never obtained.

The pinnacle is subjective. There are many excellent suspension options out there.

[dlaing]

I find that I prefer 15% unladen and 30% laden sag at both ends. I had tried the stiffer front idea mentioned but found that the bike didn't absorb bumps (when heeled over hard) symmetrically. I found that the mis-matched spring rates caused a pitch moment that I found disconcerting.

 

If I find the front end bottoming I raise the oil level or add a little compression damping (if possible). You do have to be a bit cautious with raising the oil level. Too much will give you hydro-lock bottoming of the fork.

That translates into 18mm unladen and 36mm laden with an 18mm rider only.

Probably just about what Ratchet recommends.

Maybe you guys have the numbers right.

I would bottom too much with 15/30% sag at the rear.

I measure sag sitting in my "normal" 75% rearward position in the saddle, but when I ride I sometimes slide back, and more often, not by choice, slide forward.

When slid forward, I would not be surprised if sag numbers approach the balanced front and rear numbers that you guys use. Still I find the front to be too soft. But setting the fork fluid higher could fix that without reducing my sag.

I do think a progressive spring in the shock would better match front forks air spring.

[Guest ratchethack]

. . .Selecting a spring with an 18mm deflection from rider weight is only matching the rider's weight and not the bike's

Selecting a spring based on bike and rider combined sag also does not match the bike and rider's combined weight because the preload throws the numbers off.

Dave, I don't know any suspension Pro or credible setup routine I've read that would agree with this. I't not simply a semantic problem, IMHO. You've posted a fundamental misunderstanding and made a gross misstatement. It appears that you've overlooked the fact that preload adjustment DOES NOT HAVE ANY EFFECT WHATSOEVER on spring rates.

 

When you're following the basic rough setup guideline of achieving laden sag that doubles unladen sag measurement (that is, a 2:1 laden to unladen sag ratio), and if you maintain this as closely as possible with preload adjustment, it's ONLY THE SPRING RATE that determines the difference between laden and unladen sags -- not the preload. This is clearly illustrated in my general guideline for 18 mm +/- 5 mm sag difference, less than 13 mm indicating spring rate too stiff, and greater than 23 mm indicating spring rate too low.

 

Please understand that springs support the weight of the bike in both laden and unladen sag readings!

 

If what you've said above were somehow possible, and 18 mm deflection from rider weight is only matching the rider's weight to the spring rate, and not the bike's weight, what happened to the weight of the bike when the rider got on? ANSWER: The weight of the bike is still supported by the springs, just as it was before the rider got on! The object is to correctly match spring rates to the combined load of rider and bike, and this is how sags are correctly measured.

I would bottom too much with 15/30% sag at the rear.

How do you know this? Have you tried it? I suspect not.

 

It appears to me from your sag numbers that you gave in Cat's thread that you're poorly matched as far as spring rates go (especially WRT the all-important front-rear rate balance), and I'd expect some pretty bad road manners as a result. Brian nailed it above by his experience. After I up-rated my fork springs and before I uprated the shock spring, I'd experienced much the same thing. It'd be quite another matter, and quite a bit better, IMHO if you were off in the same direction at both ends, but you're off in OPPOSITE DIRECTIONS, 3 mm outside and BELOW my 18 mm, +/- 5 mm on the fork, and 2 mm outside and ABOVE it on the rear shock. IMHO your excessive rear sag difference indicates you need a slightly stiffer rear spring rate. If you could go up-rate on the shock spring to the point where you got 18 mm or so difference, I think you'd find that you would rarely, if ever bottom-out, just as it should be. Likewise, if you were to go down-rate on the fork springs and get them more evenly matched to the rear, and have them both closer to 18 mm difference, I believe you'd be greatly pleased with the improved balance, road-holding, and ride improvements on the road -- again, exactly as Brian noted.

 

BAA, TJM, & YMMV

[dlaing]

Dave, I don't know any suspension Pro or setup regimen I've read that would agree with this. I't not a semantic problem, IMHO. You've posted a fundamental misunderstanding and made a gross misstatement. It appears that you've overlooked the fact that preload adjustment DOES NOT HAVE ANY EFFECT WHATSOEVER on spring rates.

 

When you're following the basic rough setup guideline of achieving laden sag that doubles unladen sag measurement (that is, a 2:1 laden to unlden sag ratio), and if you maintain this as closely as possible with preload adjustment, it's ONLY THE SPRING RATE that determines the difference between laden and unladen sags -- not the preload. This is clearly illustrated in my general guideline for 18 mm +/- 5 mm sag difference, less than 13 mm indicating spring rate too stiff, and greater than 23 mm indicating spring rate too low.

 

Please understand that springs support the weight of the bike in both laden and unladen sag readings!

 

If what you've said above were somehow possible, and 18 mm deflection from rider weight is only matching the rider's weight and not the bike's, what happened to the weight of the bike when the rider got on? ANSWER: The weight of the bike is still supported by the springs, just as it was before the rider got on!

You are not getting it.

You suggested that 18mm rider only sag produce the same ride for any rider weight.

This is not true.

FWIW preload does have an effect on rider only sag, but that has little relevance t this argument.

What is relevant is that for all intensive purposes rider only sag is the best measurent to indicate whether or not a spring is firm enough as deflection is proportional to rider weight. But it is not proportional to bike weight unless you had no preload.

Let me see if I can help you understand this. For simplicities sake we will use non-real world extreme number:

Bike wet weight 250 kg

Rider 1 Willie Shoemaker weight 50 kg

Rider 2 Sumo Sammy, weight 250 kg

Sitting over the rear axle for simplicity's sake

 

To get an 18mm rider only deflection Willie Shoemaker would need a spring rate of 100kg/18mm and since 18 goes into 100 5.555555555555 times the required spring would be 5.5kg/mm

 

To get an 18mm rider only deflection Sumo Sammy would need a spring rate of 500kg/18mm and since 18 goes into 500 27.77777777778 times the required spring would be 27.8kg/mm

 

Now this would be all well and fine, but the spring must also support the bike's weight.

Ideally the bike weight also would have an ideal deflection, MEASURED WITHOUT PRELOAD. If you select the spring rate based on rider weight, only one rider's weight will be the perfect match for the bike.

 

More math to come...I have to get to work <_>

[Guest ratchethack]

You are not getting it.

You suggested that 18mm rider only sag produce the same ride for any rider weight.

Dave, with all due respect, I submit it is YOU who aren't getting it, my friend.

 

The 18 mm guideline I came up with does not change with rider weight, just as the available suspension travel does not change with rider weight. It means that spring rates must match load. Nothing more, and nothing less.

 

You've evidently invented something that to my knowledge has never been used before in suspension setup, "rider only sag". I submit that there is no such thing, since there's no turning off gravitational effects on the motorcycle!!

 

You've got to get yourself unstuck from obsessing on preload, Dave. It's clearly got you off in the weeds. I think you're still missing the principle that preload is irrelevant to spring rate, and that preload is taken out of all consideration when calculating spring rate vs. load using the guidelines I came up with, while maintaining a 2:1 laden-to-unladen measurement ratio.

 

Sags are ONLY properly measured as stated above with spring rates measured against the COMBINED weight of rider and bike vs. bike only -- regardless of preload! Sag is not and cannot be measured on rider weight alone! Spring rates are correctly determined simply by measuring the deflection (or sag) achieved with rider on, and rider off the bike.

 

It's really just that simple.

[dlaing]

Willie Shoemaker's weight plus half the bike's weight is 175kg

Sumo Sammy's weight plus half the bikes weight is 375kg

Without preload, 175kg will deflect Willie Shoemaker's 5.5 kg/mm spring 64mm

Without preload, 375kg will deflect Sumo Sammy's 27.8 kg/mm spring 27mm

Following the 18mm rider only sag rule, Willie Shoemaker is under sprung and Sumo Sammy is over sprung.

Most of us on this forum are riding bikes of the same weight and our weights are not that different, but a different rider only sag will be required for our various weights.

OK, now I am late for work

[slowkitty]

I am definitely NOT GETTING IT .....

 

Will digest the data slowly (so so glad I have time to tweak the old girl slowly ....)

 

Sorry to put you guys through this.

 

Cheers

 

Cat

[Guest ratchethack]

Following the 18mm rider only sag rule,

[. . .sigh. . .]

 

I'm only going to give this one more shot, then I'm done.

 

Dave, now it appears that after inventing "rider only sag", you've invented a "rule" -- the "rider only sag rule"! I disavow any association wotsoever with this fictious concept, and this non-existent, and dangerously misleading rule!

 

The 18 mm +/- 5 mm general guideline I came up with is the difference between laden and unladen sags. BOTH laden and unladen sags are determined (either in part or in their entirety) using the weight of the bike. The laden sag combines weight of the bike AND rider.

 

THERE IS NO "RIDER ONLY" SAG MEASUREMENT, AND NO "RIDER ONLY" SAG RULE!!!!

 

--- Not here, not anywhere else, not now, not ever, never will be. NO PRELOAD CONSIDERATIONS ARE INVOLVED IN SETTING UP SUSPENSION TO DETERMINE SPRING RATES!!! PRELOADS ARE PROPERLY USED ONLY TO MAINTAIN AN APPROXIMATE 2:1 LADEN VS. UNLADEN SAG SETTING!!!!!