Setting Proper Sag

[Guest frankdugo]

thanks rachet, you can bet it's never going to stop

[dlaing]

Frank, this is just me, but I've always assumed that there is no "factory suspension set-up", and that dealers do wotever they please, which could be lots o' things -- meaning, anything from nothing a-tall to just about anything you can imagine, and possibly some things you can't. Now I don't b'lieve I'm being too overly presumptuous here, but IMHO any GOOD dealer should at least attempt to get things roughly sorted, particularly for the weight and riding style of the novice who isn't likely to know how to do his own chassis setup (or more often, doesn't know it needs to be done!), just so's the guy doesn't bottom out over his first nasty pothole followed by a dismount via a flying vault over the bars in pike position with a half-twist into the path of an oncoming Kenworth.

 

Dealers typically sell bikes without concern about spring rates. 'Nother words -- one rate fits all. This is where all the problems begin. Unfortunately, it only gets worse from here. The typical response to typically undersprung suspension is to dial up more preload in an attempt to compensate. Unfortunately, there's no free lunch here, and no compensation to be had thereby. . . it's impossible to get the sags in an acceptable range with the wrong spring rate. <_>

 

Seems to me that far too many harbor a false justification for dangerous inaction (read that confusion/ignorance/fear). It seems to give rise to the rationale that if they don't do anything a-tall with suspension that they're "safe" because they're riding on "normal" settings for "normal" riders. IMHO there is no "normal" suspension setting of any kind. Best assume that whenever you take delivery, regardless of whether its bog-stock spankin' brand-new, or PO'd, it sure as hell ain't set up for YOU in any case, and you need to start with the basics of spring rate, sags and preloads first and work thru damping rates and ride height (on both ends if adjustment is available) to finish it off.

Now SOMEBODY's just gonna go wild with apoplexy here and insist this is all wrong. But pay no attention, the woods heareabouts 'r full o' at least a coupla delusional nut-logs besides meself. FWIW, here's a little something to start with:

I wouldn't say the it is all wrong...

Actually I think Ratchet did a much better job than most of the pros.

 

Take a read of the laden and unladen sags at both ends. With the stock 120 mm travel at both ends, you should have ROUGHLY 30-40 mm laden sag and 15-20 mm unladen sag. If you're looking for softer settings, go higher in this range, but the laden/unladen sags should ideally be on a 2/1 ratio. If you're much outside of this range, you can SOMETIMES get both laden and unladen sags closer to your "target range" by adding (or subtracting) preload. Front and rear sags should match as closely as possible -- or at least not be wildly off, particularly in opposite directions. If you can't get close to this range by adjusting preload, your spring rates are not properly matched to your weight, and you're well advised to re-spring.

If you are looking for softer settings, going with more sag is not the answer.

The answer can be allusive, but basically for a softer ride you want more "sag ratio". That is, a little more than a 2:1 ratio for comfort, and a little less than a 2:1 ratio for sport.

The common recommendation for the track is less sag. I don't think this is because it is very slightly firmer, but because of you don't need the extra room for topping out if you have a predictable road ahead of you and you get more cornering clearance. On the street, potholes an nasty bumps potentially await you around every turn, so it is wise to simply have a firm enough spring and more than 30% laden sag to ensure topping out room.

Rider weight can offset the numbers. A 50Kg jockey will want quite a bit less than a 2:1 ratio, ie., a soft spring with a fair amount of pre-load, and 200kg sumo wrestler will want a greater than 2:1 ratio, ie., a very firm spring with very little pre-load.

The bottom line is you want spring rates and settings that rarely or never bottom out, but offer Comfort, Compliance and Control.

 

Another way to look at this is per my handy-dandy rule o' thumb. Assuming you've got 30-40 mm laden sag, you should have ~18 mm +/- 5 mm DIFFERENCE between laden and unladen sag at each end. If you're +3 mm on the fork, you want to be +(something close) mm on the shock, and vice-versa. If you measure too far outside this range on the high side at either end, the spring rate is too soft. Outside this range on the low side, the spring rate is too stiff.

As mentioned from the beginning of this thread, some of the Suspension Pros recommend different settings front and rear. Specifically a little less sag and a little more ratio at the rear. AAYMMV and I don't know for sure which is better. So, Ratchet and some pros could be right and the other pros wrong. On our shaft driven bike, where less active travel at the rear could be a good thing, a firmer spring with lots of sag could be ideal.

In any case, you can try Ratchets numbers or my numbers, or anywhere in between, and you should be much better off than stock.

Once again, here are my recommended numbers (subject to change if I ever get around to trying a firmer than 550#shock spring)

 

REAR Sachs

10mm unladen 8.3%

30mm laden 25%

FRONT

20mm unladen 16.7%

35mm laden 29.2%

 

And be sure to modify the numbers based on the logic presented in this amazing thread.

 

EDIT! Egads! I just took a gander at the ancient history of this thread from about a year back. If somebody starts dreaming up definitions out o' thin air and fabricating their own rules again, I'm outta here. This stuff is challenging enough without a loose bucket o' venomous false delusions rolling around on a pitching deck. . . Good frickin' grief, ain't life way too short for blithering absurdity?!?! Come to think of it, based on past history, it's only a matter of time before it starts again. . . [sigh] . . . <_>

The anticipation is killing me...

[Guest ratchethack]

The anticipation is killing me...

Um, Dave. With all due respect (however much that is), it seems the anticipation lasted even less than I'd anticipated.

 

HINT: It's you who's killed it (again).

 

So now it seems we return once again to those somewhat less than thrilling days of yesteryear. . . [sigh] . . .

 

And now I bid this thread a somewhat less than fond adieu.

 

But before I depart, anyone interested in suspension setup best beware. I'm obligated in the best interest of all concerned by virtue of heading off potential disasters before they begin, as well as by mastery of the obvious, to point out that when you see something like this:

Once again, here are my recommended numbers (subject to change if I ever get around to trying a firmer than 550#shock spring)

Keep in mind that by his own admission in his posts, this is the recommendation of someone who's never had his own suspension set up properly (at either end) the entire time he's owned his Guzzi -- (however many years of riding it badly set up this is), despite having replaced the entire front end and the shock -- and (again by his own admission) still has it wrong enough at both ends today to want YET ANOTHER re-spring at both ends. Will the pattern repeat itself into perpetuity? . . .[sigh]. . . I'm terribly afraid that only time will tell. . .

 

[dlaing]

Um, Dave. With all due respect (however much that is), it seems the anticipation lasted even less than I'd anticipated.

 

HINT: It's you who've killed it (again).

 

So now it seems we return once again to those somewhat less than thrilling days of yesteryear. . . [sigh] . . .

 

And now I bid this thread a somewhat less than fond adieu.

 

But before I depart, anyone interested in suspension setup best beware. I'm obligated in the best interest of all concerned by virtue of heading off potential disasters before they begin, as well as by mastery of the obvious, to point out that when you see something like this:

 

Keep in mind that by his own admission in his posts, this is the recommendation of someone who's never had his own suspension set up properly (at either end) the entire time he's owned his Guzzi -- (however many years of riding it badly set up this is), despite having replaced the entire front end and the shock -- and (again by his own admission) still has it wrong enough at both ends today to want YET ANOTHER re-spring at both ends. Will the pattern repeat itself into perpetuity? . . .[sigh]. . . I'm terribly afraid that only time will tell. . .

 

Adieu Monsieur,

From the admission of my posts, I would not ADMIT that I have not had my own suspension set up properly.

What constitutes properly is subjective.

My suspension is set far better than stock, and I admit there is room for improvement.

I have considered sending the suspension off for re-valving at the recommendation of those that have done so.

I have considered experimenting with different fluid levels and spring rates.

I set my front fluid level to a number from one book, but finally learned that another number is what Guzzi recommends, so there may be room for improvement there, but I am only off by 5mm.

My Ohlins fork springs I assume are stock, which should indicate they are too soft, but my sag numbers for the front shamefully fall into what Ratchet might criticize as being improper, 36mm laden and 26mm unladen or a 1.38:1 ratio!!!! So, according to Ratchet's magic numbers, my OEM spring must be too firm despite the fact that it regularly bottoms out. Do I listen to Nurse Ratchet and go softer springs or do I do what I think would be most beneficial and get a firmer pair of springs, or do I leave well enough alone and stay with the OEM springs?

At the rear, I replaced the Sachs with a customized Penske that adds about 9mm stroke or 18mm travel to the rear end. IMHO this really helps make the bike ride more comfortably. My sag numbers at the rear are ~31.3mm laden and 5.5mm unladen or a 5.7:1 ratio, so apparently my 550#/inch spring is too soft by Ratchet's magic numbers. Here I am more inclined to believe a firmer spring might help, or even better, a progressive spring, since like the front, the rear still bottoms out (as best I can tell).

PLEASE NOTE:

I selected the 550#/inch spring based on the experiences of forum members here that weigh about the same that I do.

One of the forum members tried 550 and 500 and greatly preferred the 500, and the other was happy with the 550.

Either is a huge improvement of the stock that is probably somewhere around 400/450#/in. In any case, my added travel makes under-springing less of an issue.

The tenth of a millimeter accuracy at the rear is based on the average of a series of measurements to the nearest millimeter that took into consideration stiction.

The measurement at the front was done by Nurse Ratched, back when he was less ornery...

[BrianG]

This thread is either humorous or pathetic.......

 

Mostly because there's not a rider amongst us that could actually tell the difference between the performance given at 50/50 or 2/3 or 25/75 when ya throw in some damping variables...... never mind this silly arguing over trivial variances theoretically espoused by the "suspension experts". :rolleyes

 

If you're not bottoming or topping out, and both ends rise and fall together, Bob's your uncle.......

[dlaing]

This thread is either humorous or pathetic.......

 

Mostly because there's not a rider amongst us that could actually tell the difference between the performance given at 50/50 or 2/3 or 25/75 when ya throw in some damping variables...... never mind this silly arguing over trivial variances theoretically espoused by the "suspension experts". :rolleyes

 

If you're not bottoming or topping out, and both ends rise and fall together, Bob's your uncle.......

The problem is some of us give advice to others 'round here, and it would be nice if people followed the advice and did not end up with the wrong springs.

I bottom out with the experts' numbers.

So, how do we set the numbers so that you don't bottom or top out.

I know 35mm laden and 30mm unladen would not bottom out, if they only make springs that firm for the front, rear should be no problem getting what everis necessary for those sag numbers, maybe 1500# springs. But I can guarantee the ride would be too harsh.

[Guest ratchethack]

This thread is either humorous or pathetic.......

 

Mostly because there's not a rider amongst us that could actually tell the difference between the performance given at 50/50 or 2/3 or 25/75 when ya throw in some damping variables...... never mind this silly arguing over trivial variances theoretically espoused by the "suspension experts". :rolleyes

 

If you're not bottoming or topping out, and both ends rise and fall together, Bob's your uncle.......

. . .[sigh]. . . Here I was trying to quit this thread. . . but alas and alack. I simply can't let this one slide. . .

 

Whooooooa there, big fella. I b'lieve you differ widely with wot's well known and established, my friend. Big time.

 

Despite the well confused and well confusing gyrations of a select few who can't seem to tell the difference, (er, maybe only one, and I sympathize -- it's gotta be one godawful distraction to the un-initiated), this stuff is far beyond theory and speculation -- and has been for the better part of the last century. It's evolved with technology just like everything else, but it's far from much ado about nothing!

 

I'm no Johnny Racer-boy, merely a dedicated and unrepentant Road Geez. And I can't be entirely sure wot you're referring to with the numbers you gave above, but it looks like you mean laden sags?? I'm here to tell you that I can most certainly detect significant differences in handling when I make adjustments to preload and sags at far less than the numbers you posted! Changing spring rates (which directly changes BOTH laden and unladen sags) can make (and without question has made) the kinds of differences on the road that're properly classified as "transformational", in a positive direction. I've achieved such as this many times on many moto's with such kinds of dramatic improvements to handling and ride. There's nothing unique to Guzzi's in all of this, and I'm afraid there's no denying it, either.

 

Yours seems to be the second post of this nature on this Forum, as I recall. The first was from someone awhile back who obviously considered himself an expert on suspensions, and who thought himself very well qualified to make a proclamation, having been riding for 30 years, I think he said. He said something to the effect that he'd not even heard the term "sag" applied to moto suspensions until several years ago. His take seemed to be similar to your own -- that is, beyond "softer" and "harder", there's no need for any further attention given to suspension. Since he'd been unaware of of the concept of "sag" for decades, I reckon his less than well-considered conclusion must be that it's something someone dreamed up to sell something!

 

Now I'm sure that a century ago this mindset would properly fit the leading moto suspensions of the day. But f'er cryin' out loud, ain't it pretty obvious that (like tires and engines fer cryin' out loud!) moto suspensions are just a tad more sophisticated and capable -- not to mention SUPERIOR in delivering better handling today, or do you take exception to this idea also?!

 

It's interesting to me that suspension setup naysayers seem to be the ones who have obviously never had their suspensions properly set up. And how would anyone ever know wot it's like to get it right (or at least somewhere in the right area of the ballpark) if they've never ridden a properly set up and well-matched chassis??

 

Hm. I reckon the notion of a spherical planet is still rejected, somewhere. And ain't ignorance not only bliss, but ain't the cure always apt to be utterly rejected by some -- regardless o' the facts?!?!

 

Must be that all those racing teams spending all that time and attention on suspensions chasing better lap times are wasting their time, eh?

 

Must be the likes o' Paul Thede are snake oil salesmen, too, eh? Hm. . . I never bought anything from RaceTech, but his principles of suspension dynamics and tuning, which are taught in the most well-known Professional Moto Suspension Tuning classes offered in the US (see link below and link to his company Web site), seem to've caught on pretty well. D'you reckon there's nothing behind any of it other than sales training?

 

http://www.racetech.com/articles/SuspensionAndSprings.htm

 

Enquiring minds. . . (well, you know)

[dabore84]

Well, I just took measurements on my bike, here are the results:

 

Back

unladen 20 mm

laden 50 mm

 

 

Front

unladen 30 mm

laden 40 mm

 

I also think there could be something wrong with the front fork. When I am on the bike, I push the fork down and release it, I hear a click.

What do you think?

[Guest ratchethack]

Well, I just took measurements on my bike, here are the results:

 

Back

unladen 20 mm

laden 50 mm

 

 

Front

unladen 30 mm

laden 40 mm

 

I also think there could be something wrong with the front fork. When I am on the bike, I push the fork down and release it, I hear a click.

What do you think?

Dabore, wot you've provided is a good start! IMHO you could benefit hugely from a re-spring at the rear in the stiffer direction and at least more preload on the fork, possibly a fork re-spring in the softer direction as well. After considering the principles offered here:

 

http://www.racetech.com/articles/SuspensionAndSprings.htm

 

http://www.strappe.com/suspension.html

 

and for final set-up, here:

 

http://www.peterverdonedesigns.com/oilheight.htm

 

. . . wot do YOU think??

 

If you're interested, I'm pleased to help. But no one here can carry the whole load for you and tune your chassis for you over the Web. Speaking for myself, merely one among many here, I'm always pleased to help -- as long as you're sincere about wanting the help.

 

-- Cdr. Hatchracket, Esq.

[dabore84]

Dabore, IMHO you could benefit hugely from a re-spring at the rear and at least more preload on the fork. After considering the principles offered here:

 

http://www.racetech.com/articles/SuspensionAndSprings.htm

 

http://www.strappe.com/suspension.html

 

and for final set-up, here:

 

http://www.peterverdonedesigns.com/oilheight.htm

 

. . . wot do YOU think??

 

If you're interested, I'm pleased to help. But no one here can carry the whole load for you and tune your chassis over the Web. Always pleased to help if you're sincere about wanting it.

 

-- Cdr. Hatchracket, Esq.

 

 

All help is welcome I am still a young driver (23) and in the learning phase. Yeah, I know, you learn whole your life.

 

For the improvements I'll need to wait for payday 23 may, so I wont be doing anything on the bike until then.

 

Now I am just , soon and then . ( ) I am not fat (ofcourse little bit, more big boned ), but I weight with clothes and all other stuff on me, about 260 lbs. So new (stiffer) springs should be a tremendous improvement. But what about that click in the front forks, what could that be?

I didn't figure out yet if it is in the left or right shim, or both.

 

No I am off to a BBQ.

 

[Guest ratchethack]

. . .what about that click in the front forks, what could that be?

I didn't figure out yet if it is in the left or right shim, or both.

Hm. Sorry, Dabore. Y'got me by the tweeter on that one. It could be any of a great many things??

 

I'd see if I could narrow down the exact location of the source, but that's just me.

 

I've got a mechanic's stethoscope that'd be just the thing. Know any medical folks? A length of tube with a friend to help bounce the bike may suffice.

[macguzzi]

Oh no not again you guys need your own forum

[Guest ratchethack]

Oh no not again you guys need your own forum

Hey Mac. This is a Technical Forum. The topic is Setting Proper Sag.

 

Looks like there are a few with sincere interest here.

 

If you don't like it, aren't interested, and have nothing to offer, wot the feck are you doing here?

 

Enquiring minds. . . (well, you know).

[BrianG]

........Changing spring rates can make the kinds of differences on the road that're properly classified as "transformational".............

 

Ya, I doubt it...... that is, within the laden sag range I mentioned.

 

Particularly when you consider the effect of variable damping rates added into the equation... as I mentioned and you conveniently ignored...

 

I also think there could be something wrong with the front fork. When I am on the bike, I push the fork down and release it, I hear a click.

What do you think? knownothing.gif

 

.......... But what about that click in the front forks, what could that be?

 

 

If you have not isolated that "click" to the fork leg I'd bet a big fat steak that it's your head bearing..... a bit too loose and likely greaseless!

[Guest ratchethack]

Ya, I doubt it...... that is, within the laden sag range I mentioned.

 

Particularly when you consider the effect of variable damping rates added into the equation... as I mentioned and you conveniently ignored...

Brian, I ignored the damping effect you threw in the mix because it's meaningless here. Damping can only mask the ability to detect the changes in sag you proposed. No amount of damping wotsoever, short of approaching lockup of the cartridges (made impossible to achieve by every mfgr I know of), can possibly overcome real-world changes on the road due to changes in sag settings of the degree you proposed.

 

May I assume that your observations and conclusions are based on something other than speculation and conjecture? If so, I reckon you've actually made the kinds of significant changes to sags that you've proposed above on your own fork, and then failed to notice any effects a-tall afterward on the road?

 

If this is actually wot you're proposing here, I reckon it might be something of a first in moto history unless you're not paying attention enough to care or somehow can't detect considerable changes to suspension and handling in general? Not only would it be contrary to my own repeat experience and expectations, but it would be contrary to the wisdom and experience of the highly qualified Suspension Pro's who've been setting up suspensions for many decades over their professional careers (see prev. link to article and Website of Paul Thede, of RaceTech) -- not to mention racing teams -- all of whom seem to have an altogether different understanding than your own.

 

But when it comes to suspensions, as we've seen demonstrated here so profoundly and repeatedly, I reckon there's always somebody who's always gonna b'lieve that they're special, and the leading wisdom and knowledge of the Pro's doesn't apply to them, or their moto. . .

 

And wottayagonna ever do with that mentality??

 

Not much, I reckon.