Ya baby, it's all good

[ALdad]

2000 sport. Ok, changed tires to 120/70 ,160/60 Diablos. Had a 180 on it. Droped front 8mm. Front sag now 23free,33mm rider ,rear is 25/37. + on comp/dmp. on front couple clicks past half way and more on rear I'll have to figure out where I am on rear I think I'm about 3/4 + in. Next time tank is off I'll add a bit more preload. I can't believe how much lighter the rear end feels, much better. Before, it was like I was riding around with a serious load in my shorts. No more speed wabble in corner with abrupt throttle chop, not that this is my deceleration technique of choice but it does sometimes happen in the real world. I do anticipate a shorter tire life as I now feel it spin sometimes when I get on it out of corners. I am not totally comfortable with this light feeling yet on this bike. My monster spun and ate tires when I rode hard but maybe it was the shorter weelbase that made the rear feel more confident? Maybe I just need a coulple of weeks. Anyway I'm loving it,Thanx for the advice on this spectacular fourm, Thanx Senor Rachethead. Now I cant wait to modify the cush drive as per the recent thread. Cheer!! Alan

[Guest ratchethack]

Por nada, mi compadre.

 

Sounds to me like you've got her pretty well dialed-in, my friend.

 

Ain't it a beautiful thing when you discover wot she's had in her the whole time, once she's allowed to express herself??

[dlaing]

2000 sport. Ok, changed tires to 120/70 ,160/60 Diablos. Had a 180 on it. Droped front 8mm. Front sag now 23free,33mm rider ,rear is 25/37. + on comp/dmp. on front couple clicks past half way and more on rear I'll have to figure out where I am on rear I think I'm about 3/4 + in. Next time tank is off I'll add a bit more preload.

Senor Ratchethead recommends 15/30% front and rear.

 

I recommend the following:

REAR Sachs

10mm unladen 8.3%

30mm laden 25%

FRONT

20mm unladen 16.7%

35mm laden 29.2%

 

MODIFIERS (all are rough guesses or opinions...what is your's)

*Racing, subtract 1 to 5 mm from laden sag.

*Touring, add 1 to 5 mm to laden sag.

*Frequent two up, subtract 1 to 6 mm from rear laden sag, and subtract about half of that from front sag. Note: this is assuming sag is measured without passenger.

*Ohlins, add 5mm to rear laden sag.

*Progressive springs, add 2mm to laden sag and subtract 1mm from unladen sag.

*Short legs, add laden and unladen sag at a ratio of maybe 4mm additional laden for every 5mm additional unladen. (because shock needs to be firmer as travel decreases)

*Rider weight greater than 80kg, add 1mm rear laden sag for each additional 20kg, and 1mm front laden sag for each additional 40kg

*Rider weight less than 80kg, subtract 1mm rear laden sag for every 20kg less than 80kg and subtract 1mm front laden sag for every 40kg.

*Personal preference, (no sag nazis here) add or subtract whatever you want to laden and or unladen sag numbers. wacko.gif

 

Your spring rates appear to be good, although maybe a bit on the firm side, especially at the rear.

The rear end feels light an spins coming out of turns, which indicates too firm of a rear end.

This leaves me a little perplexed as to the right direction to head in, but I think you will find that a little less rear sag and less rear compression damping should help.

[Guest ratchethack]

Senor Ratchethead recommends 15/30% front and rear.

Err, actually, I b'lieve you'll find I've never made this as a recommendation.

 

Wot I've suggested as GUIDELINES are:

 

15-20/30-35% unladen/laden for general purpose road work, and a 18 mm +/- 5 mm difference between laden and unladen sags -- for BOTH FRONT & REAR -- as is consistent with the RECOMMENDATIONS of most Pro's in the business, as well as the directly quoted statement of Paul Thede, Pres & CEO of the foremost Professional suspension training organization in the USA, Racetech, per previous posts.

 

In Sport Rider Magazine, Issue : August 1995, Thede said:

 

"Using different sag front and rear will have huge effect on steering characteristics. More sag on the front or less sag on the rear will make the bike turn more slowly."

 

This is consistent with every credible source I've found. I don't think Paul's too likely to've changed his mind on this in the last 12 years, but of course,

 

TJM & in the case that you're racing something such as bar stools or ice boats, YMMV

 

SOURCE:

 

<a href="http://www.racetech.com/SubMenu.asp?cMenu=...showPage=street" target="_blank">http://www.racetech.com/SubMenu.asp?cMenu=...showPage=street</a>

[dlaing]

Err, actually, I b'lieve you'll find I've never made this as a recommendation.

Mea Culpa. I obviously took the following post too literally, as well as your defense in the same thread of the 15/30%. Sometimes I forget you argue only to spite me.

Along the same conceptual lines, I thought of a way to hopefully de-confuse Dave, as soon as he makes his way back to an unsupervised screen. . .

 

ASSUMPTIONS:

 

Front and rear target sag measurements are kept the same for correct fore-aft chassis balance.

 

In setting up the sags, a 2:1 laden-to-unladen ratio (in mm) will be maintained as closely as possible by adjusting preload accordingly.

 

For general purpose guidelines, 15% of total avaliable suspension travel (120 mm) = unladen sag = 18 mm.

 

For GP guidelines, 30% of total available suspension travel = laden sag = 36 mm.

 

For GP guidelines, an 18 mm +/- 5 mm difference in sag measurement is about right.

 

Let R = rider weight

 

Let G = Guzzi weight

 

Let R + G = combined rider and Guzzi weight

SNIP

[Tom M]

In Sport Rider Magazine, Issue : August 1995, Thede said:

 

"Using different sag front and rear will have huge effect on steering characteristics. More sag on the front or less sag on the rear will make the bike turn more slowly."

 

That has to be a misprint. I thought that adding more sag in the front is like sliding your forks up through the triple clamps, it reduces rake and makes steering quicker, right? The same goes for reducing rear sag, you're effectively raising the rear which should make the bike steer quicker.

 

From another article in Sportrider magazine ( http://www.sportrider.com/tech/146_9508_tech/index.html )

"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."

[Dan M]

That has to be a misprint. I thought that adding more sag in the front is like sliding your forks up through the triple clamps, it reduces rake and makes steering quicker, right? The same goes for reducing rear sag, you're effectively raising the rear which should make the bike steer quicker.

 

From another article in Sportrider magazine ( http://www.sportrider.com/tech/146_9508_tech/index.html )

"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."

 

Right Tom. Raising the rear or lowering the front decreases rake & trail which will quicken steering. (or more accurately, reduce steering effort)

[Guest ratchethack]

That has to be a misprint. I thought that adding more sag in the front is like sliding your forks up through the triple clamps, it reduces rake and makes steering quicker, right? The same goes for reducing rear sag, you're effectively raising the rear which should make the bike steer quicker.

No misprint, Tom. While what you say is true -- changing sag front or rear changes rake and trail, and by itself will affect steering quickness, changing the sag IS NOT the proper way to correctly adjust steering quickness!

 

Thede made the point that a mismatch of sags front and rear has consequences to steering quickness, and added that a small mismatch makes a HUGE difference.

 

Setting the sags correctly is done as a priority over any adjustment for steering quickness, and should always be independent of making adjustments to rake and trail!

 

Rake and trail adjustments are correctly done by adjusting the height of the fork tubes in the triple clamps. Alternately, and where available, it can also be changed by adjusting the length between shock eyes. Neither of these affect sag settings.

 

Andy Trevitt at Sport Rider put it this way:

 

Raising the front of the bike or lowering the rear will lengthen trail, slowing steering but benefiting stability. You can change front ride height by moving the forks in the triple clamps, and rear ride height can be altered by lengthening or shortening the shock.

For definitions and fundamentals, I have found the following sites very helpful. Understanding the simple principles involved will make this clear. Note that Paul Thede, source of the quote in question, is Pres and CEO of the company (Racetech), quoted in the second link below, where you will find the quote (at bottom of the page), exactly as it was correctly published in SportRider:

 

<a href="http://www.strappe.com/suspension.html" target="_blank">http://www.strappe.com/suspension.html</a>

 

<a href="http://www.racetech.com/articles/SuspensionAndSprings.htm" target="_blank">http://www.racetech.com/articles/SuspensionAndSprings.htm</a>

 

For fine-adjustment of the fork (only) I recommend Pete Verdone's write-up on fork air gap settings here:

 

<a href="http://www.peterverdonedesigns.com/oilheight.htm" target="_blank">http://www.peterverdonedesigns.com/oilheight.htm</a>

 

Hope this helps.

[dlaing]

In Sport Rider Magazine, Issue : August 1995, Thede said:

 

"Using different sag front and rear will have huge effect on steering characteristics. More sag on the front or less sag on the rear will make the bike turn more slowly."

I vote misprint.

When changing the geometry is limited by how far you can go with the forks and the limited adjustability of the rear end, it is perfectly fine to use sag to adjust the ride height.

Yes, you do not want to stray too far from ideal sag, but all you are giving up is travel.

Compare the rear travel of a V11 five speed tonti to the travel on the spine frames.

We have a lot of travel we can give up in order to obtain a ride height suitable for someone with short legs.

But better handling for our bikes SEEMS to be found with the rear end up higher than stock.

In my opinion ALdad SHOULD use sag to adjust his rear end height to be higher, although I certainly could be wrong as handling is subjective, and he may prefer a slower turning bike.

[Tom M]

Ratchet,

I was just pointing out that the quote in your post from the 1995 SR article is ass-backwards and probably a misprint because I know Thede knows what he's talking about. If you click the link to Sport Rider in my post above you will see that the quote at the bottom of my post is attributed to Paul Thede from Race Tech, and it directly contradicts the quote in your post.

 

Your quote:

"More sag on the front or less sag on the rear will make the bike turn more slowly."

 

My quote:

"More sag on the front or less sag on the rear will make the bike turn more quickly.

[Guest ratchethack]

Well spank me naked, Gertrude!

 

Tom, you and Dave (EDIT -- and Dan!) are CORRECT!

 

The quote is bass-ackwards!!

 

Shame on me for not paying closer attention, and profuse apologies all around. . .

 

12 years is a long time to have a misquote still out there on the Web, wouldn't you think??

 

Many thanks for pointing this out, Tom. I reckon I can't refer people to that link anymore. . .

 

EDIT: I sent an email to the Webmaster at Racetech notifying them of the error. We'll see if anything happens.

 

EDIT (PART II): Despite Dave's post above, and the incorrect contention of others over many years to the contrary, I've actually never made ANY specific RECOMMENDATIONS to anyone about suspension settings whatsoever -- nor would I be so presumptuous to do so, since it's neither an exact science, nor are there any specifically "correct" settings according to preferences and riding styles, terrain covered, etc., etc, etc.

 

AGAIN, wot I've occasionally SUGGESTED to those who either ask outright, or for those who seem to be either lost or "fishing", is GUIDELINES for STARTING POINTS based on RANGES of sag settings that, BTW, are only possible to achieve with correctly matched spring rates to load, as noted above.

 

I repeat that (unlike others, apparently) I have NOT dreamed any of this up out of thin air, or relied in any part simply on "what seems right" to me! These guidelines are generally those of suspension Pro's such as Paul Thede at Racetech, among many others, including leading moto magazine editors. Since the entire world of moto suspensions seems frightfully skittish about PUBLISHING any such guidelines (liabilities being wot they are), and hard to find, I believe them to be occasionally very helpful to have close at hand for some riders for general road riding purposes.

 

I've also picked up a number of helpful general principles of suspension dynamics that, while simple enough, seem anywhere from confusing to unfathomable to others. . . much as they were for me many years ago. . .

 

Seems to me that without SOMETHING to work with for starters, many would otherwise be shooting in the dark, making incorrect assumptions, and potentially winding up with something potentially unsafe, or more often at least not particularly enjoyable to ride -- not to mention the common state of most riders, IMHO, who suffer under delusions that crappy handling is the best their bikes are capable of -- and for all they know, crappy is as good as it gets!!

 

I'm not assuming that very many pay any attention wotsoever to my non-professional, shade-tree blatherings here, but if someone wants to sue me for damages based on a crash due to my SUGGESTED GUIDELINES, I reckon I ain't too legally exposed on an "open source" Web board. FWIW, I sure wish I'd had suspension GUIDELINES many decades ago -- it would've shortened the learning curve considerably. . .