Suspension Set-Up Help Wanted

[MickM]

Hope everyone has a very merry Guzzi Xmas. Would like some advice. My 02 LM has now done 6600km and I'm finding it's still too stiff for me. I've backed the front compression damping almost completely off and am running similarly light at the rear and I'd still like better compliance over broken surfaces. Still running original 10wt fork oil. Please understand that I don't ride it hard .... if I get to within about 15mm of the tyre shoulder I've done well. What I'd like is better compliance and good turn in. Has anyone tried either 5wt oil or a lighter spring in Marzocchi's ? Any recommendations ? Had a search thru the archives but couldn't find anything really going this direction ... I admire you blokes that can go hard enough to actually want it stiffer ! My other question is grips ... I've done an anti-vibe mod incorporatig custom cro-moly bars filled with lead plus big end weights and it's really pretty good but I figure different grips might be a worthwhile extra step. I'm using a standard sort of foam grip - any recommendations for a significant step up ? Many thanks in advance.

[g.forrest]

Hope everyone has a very merry Guzzi Xmas. Would like some advice. My 02 LM has now done 6600km and I'm finding it's still too stiff for me. I've backed the front compression damping almost completely off and am running similarly light at the rear and I'd still like better compliance over broken surfaces. Still running original 10wt fork oil. Please understand that I don't ride it hard .... if I get to within about 15mm of the tyre shoulder I've done well. What I'd like is better compliance and good turn in. Has anyone tried either 5wt oil or a lighter spring in Marzocchi's ? Any recommendations ? Had a search thru the archives but couldn't find anything really going this direction ... I admire you blokes that can go hard enough to actually want it stiffer ! My other question is grips ... I've done an anti-vibe mod incorporatig custom cro-moly bars filled with lead plus big end weights and it's really pretty good but I figure different grips might be a worthwhile extra step. I'm using a standard sort of foam grip - any recommendations for a significant step up ? Many thanks in advance.

try backing off rebound damping then you may find you need to increase your compression damping

[dlaing]

foam grips are good for vibration.

I prefer ProGrip Gel grips because it gives a better grip while still sopping up some vibes.

Gel gloves help, but I have not found a good quality pair of gloves with gel palm.

Tell us your weight.

I believe the stock suspension has too much high speed compression damping.

This may be some of the harshness you are feeling.

But you may also be feeling some harsh bottoming out.

So, you may actually need stiffer springs.

Bottoming out can be tested with a thin zip tie.

How the bike handles also provides clues.

Penske's website has some excellent tips in their pdf manuals.

But their webpage is under construction...

If comfort is what you are after, you might want light compression damping and just enough spring rate to eliminate bottoming on almost all the roads you ride.

Progressive springs may be what will help you the most, but racers often scoff at progressive springs.

 

try backing off rebound damping then you may find you need to increase your compression damping

That will especially help if the suspension packs down and the effective travel lessens durring series of bumps due to rebound being out of balance with spring rate and compression damping.

[MickM]

Tell us your weight.

I believe the stock suspension has too much high speed compression damping.

This may be some of the harshness you are feeling.

But you may also be feeling some harsh bottoming out.

So, you may actually need stiffer springs.

Bottoming out can be tested with a thin zip tie.

How the bike handles also provides clues.

Penske's website has some excellent tips in their pdf manuals.

But their webpage is under construction...

If comfort is what you are after, you might want light compression damping and just enough spring rate to eliminate bottoming on almost all the roads you ride.

Progressive springs may be what will help you the most, but racers often scoff at progressive springs.

That will especially help if the suspension packs down and the effective travel lessens durring series of bumps due to rebound being out of balance with spring rate and compression damping.

 

Thanks guys. I haven't tried putting a zip tie on it but I don't get the sense that it's bottoming. I weigh 175lb and have 25mm laden sag in the front ... which would seem about right. No real complaint with the handling for how hard I ride it - it's great in faster, flowing stuff but, and I know this is my fault, in tighter stuff it will often turn in good for me but I then find myself having to stand it up a bit and have a second go at picking a radius. The tubes are 12mm up to accomodate spacers between clip-on and fork crown. Tyre profiles are still good with no apparent flat section at the rear or cupping on the front. It's the sharp, high speed compression 'thump', only using a little travel, which I'd like to fix and which is common on our shit Aussie roads. I don't have any issue with the rear, seems fine even with my wife on.

I can see value in a progressive fork spring with softer static rate and maybe 5wt oil to restore a more useful range of adjustability ? Any thoughts if this would be the right track ? Thanks again.

[dlaing]

Forum member Ratchethack is very close to your weight and he has put a lot of thought and effort into suspension setup, and he is very happy with the results he has gotten.

You could look up his posts on the subject, or he may throw in his

He has been dialing in some Wilbers shocks that I am interested to hear about

Personally I tend to favor the lighter fork oil or suspension fluid, so I would give the 5W a try.

Do select a premium brand as they are not all created equally.

Unlike the difference between synthetic and dino oil, it is more difficult to determine the difference in quality from marketing hype.

Ohlins makes good oil, but it is expensive.

[Guest ratchethack]

Thanks guys. I haven't tried putting a zip tie on it but I don't get the sense that it's bottoming. I weigh 175lb and have 25mm laden sag in the front ... which would seem about right.

Mick, I've completed a thorough mapping of my '00 Sport suspension, so I've "had the course" so to speak. I've replaced both fork springs and rear shock (custom order), as well as fork fluid (went to lighter-than-stock, 125/150 synth. CARTRIDGE FORK FLUID) and re-set spacer length, fork height, air gap (oil height) etc. Guzzi models have widely different stock spring rates and suspension components from the factory. My fork and shock springs were hopelessly out of ideal target sag ranges (both laden and unladen). As I recall, I was getting something on the order of 50 mm laden sag on the fork with stock springs and preload spacers, the unladen sag was impossible to preload in target range in the correct ratio with laden sag, and I weigh the same as you. Your bike has a slightly different Marz fork than mine, and I highly suspect entirely different stock spring rates. If your laden sag measurement is 25mm, this is an indicator that y'er fork springs may be too stiff for your weight/laden load, depending on unladen sag and how the spacer preload is set. Looking at just laden sag is only partially helpful at best, and may be completely misleading. The relationship between laden and unladen sags is the key to getting the proper spring rate, both front and rear.

 

I applaud your efforts. I've found that most riders ignore suspension setup entirely, and many who say they've done it are poorly informed and consequently wind up with a wallowing sow, thinking that this is as good as it gets. Unless working from a frame of reference of some kind , how would they ever know? I'm continually amazed at the number of riders who believe that suspension setup means simply compression and rebound damping adjustment. But to each his own. Without doing suspension setup correctly, as I have said lo these many years, I submit this as a fact: there is ZERO percent possibility of achieving the handling that y'er Guzzi was designed with and is capable of. IMHO, it's capable of wonderful handling on the road, but then I'm merely a Road Geez, not a Boy Racer or any flavor of a Wannabe. By modern standards, the Guzzi is merely a "Cannabe" anyway -- so I reckon we're a perfect match.

 

Here's a quick and easy test to see if y'er fork spring rates are correctly matched to y'er riding load:

 

DISCLAIMER: This is just MY OWN handy "rule o' thumb". There WILL BE disagreement on this, & YMMV!

 

Measure laden and unladen sags. The difference between them should be ~18mm, +/- 5 mm.

 

If the difference is GREATER than 23 mm, the spring rate is too low.

 

if the difference is LESS THAN 13 mm, the spring rate is too high.

 

If you're within the sag tolerance above, you can set preload spacer length and air gap for optimum fork travel according to the following links, which I've found extremely valuable for chassis setup. Hope this helps.

 

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

 

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

 

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

[Dan M]

Hey Mick,

 

There is a pretty good suspension set up video here - go to the "track wrenching" section.

 

http://www.onthethrottle.tv/

[MickM]

Many thanks guys for the well considered ideas and the links ! I've gone back and done several sets of measurements and found I consistently get 9mm between unladen and laden sag .... so it has probably got a touch too stiff spring in it for me. It does appear to be well balanced because it is at least ... or as best as my wife can detect, have both ends moving in parallel. So after much head scratching the intention is to take 5mm off the preload spacer, swap to a standard volume of 5wt oil, soften the rear a bit to match and see how it goes. If that gives me a touch more compliance in the first bit of bump travel I'll be happy to call each of you a genius ! Thanks again.

[dlaing]

So after much head scratching the intention is to take 5mm off the preload spacer, swap to a standard volume of 5wt oil,

Reads like a good plan

You might want to measure the fluid going out and going in.

It could be that it was previously over-filled with oil.

Keep in mind that taking 5mm off the spacer will lower the bike nearly 5mm and reduce the volume of air that you are riding on.

This could actually make your ride harsher.

So, you may also want to lower the fluid level.

If you are not bottoming with the standard volume of fluid, you could try going to a slightly lower volume of oil to allow greater compliance.

I am not sure how low you can go. You don't want to deprive the dampers and sliders of oil.

[Murray]

35mm sag would be better 25mm is a good track setting 10-15mm for the rear.

[Guest Phil Daw]

Hope everyone has a very merry Guzzi Xmas. Would like some advice. My 02 LM has now done 6600km and I'm finding it's still too stiff for me. I've backed the front compression damping almost completely off and am running similarly light at the rear and I'd still like better compliance over broken surfaces. Still running original 10wt fork oil. Please understand that I don't ride it hard .... if I get to within about 15mm of the tyre shoulder I've done well. What I'd like is better compliance and good turn in. Has anyone tried either 5wt oil or a lighter spring in Marzocchi's ? Any recommendations ? Had a search thru the archives but couldn't find anything really going this direction ... I admire you blokes that can go hard enough to actually want it stiffer ! My other question is grips ... I've done an anti-vibe mod incorporatig custom cro-moly bars filled with lead plus big end weights and it's really pretty good but I figure different grips might be a worthwhile extra step. I'm using a standard sort of foam grip - any recommendations for a significant step up ? Many thanks in advance.

 

Try reducing the rebound damping front and rear, restore some front compression damping for braking

and potholes!

Also, check the rear shock absorber linkage is free and properly greased.

My bike is like a magic carpet after similar mods.

Best of luck

Phil

[Guest ratchethack]

Keep in mind that taking 5mm off the spacer will lower the bike nearly 5mm and reduce the volume of air that you are riding on.

This could actually make your ride harsher.

A very good point, Dave. But it appears his spring rates are mis-matched to load on the high side, so he's certainly not getting close to full fork travel. Since air spring only comes into effect at the end of fork travel, a change in air spring effect of 5mm less preload would not be likely to make the fork perceptibly stiffer whatsoever in his case. It should be pointed out that changing the spacer length has no effect on the air gap setting (see link at Pete Verdone's site above). In the order of things, by my experience and that of the Pro's (see links above), best leave air gap adjustment for the "fine tuning" phase after getting laden and unladen sags set in the target range with preload spacers. If you don't get the sags and preload right to begin with, you'll wind up with the impossible task of chasing bad handling with air gap, compression & rebound settings, fork height, etc.... and then y'er off on a rabbit trail to nowhere. . . . .

[dlaing]

A very good point, Dave. But it should also be pointed out that changing the spacer length has no effect on the air gap setting (see link at Pete Verdone's site above). In the order of things, by my experience and that of the Pro's (see links above), best leave air gap adjustment for the "fine tuning" phase after getting laden and unladen sags set in the target range. If you don't get the sags and preload right to begin with, you'll wind up with the impossible task of chasing bad handling with air gap, compression & rebound settings, fork height, etc.... and then y'er off on a rabbit trail to nowhere. . . . .

Yes, only the the air gap setting has effect on the air gap setting, but lowering the preload decreases the air gap.

The less air gap, the greater the air spring effect.

If we know that the preload is being taken off we know the air spring rate will increase and compliance will be reduced.

If our objective is compliance and we know we are not currently bottoming out, then we can predict that removing preload without lowering the fluid level will reduce compliance.

Finding out how close he is to bottoming is pretty trivial and could save alot of time trying to set the fluid level later.

I would not lower the oil level without determining how close to bottoming he is.

If he is five millimeters from bottoming now and he lowers it fve millimeters, then he won't want to lower the fluid level.

But if he tests that he is 15mm from bottoming, then he has some room to lower the fluid level.

I test for fork bottoming by aggresively braking over a speed bump, dip in the road, and or a patch of bumpy road.

 

While the expert, Pete Verdone, writes that fluid level is the final step, he also writes:

"If the fork is bottoming under hard braking, the oil height will need to be raised. If the fork is not still soaking up bumps in this situation, oil height will need to be lowered."

From what I understand, Mick is experiencing the fork not soaking up bumps.

Using one's intelligence to predict an outcome can save work in the future.

There may be no need for him to go back and reset the fluid level.

But I guess if you have the proper syringe, it would be pretty trivial to reset the fluid level.

[Guest ratchethack]

. . .So after much head scratching the intention is to take 5mm off the preload spacer, swap to a standard volume of 5wt oil, soften the rear a bit to match and see how it goes. If that gives me a touch more compliance in the first bit of bump travel I'll be happy to call each of you a genius ! Thanks again.

Mick, I forgot to mention that many Marz forks (including my 40 mm USD's) have a provision for infinite preload adjustment within (I think) 10-20 mm or so. When the fork caps come off, (back compression & rebound damping adjusters off full counter-clockwise first -- don't ask me why, this is wot the Guzzi manual calls for ), you'll find the fork caps threaded to the cartridge rod assemblies and locked in position with jam nuts just beneath the caps. If you crack them off and leave the jam nuts where they were from the factory, take a measurement of the remaining free threads on the cartridge rod assemblies (mine were 22mm). Assuming they haven't previously been meddled with, you have a "factory setting" starting point for a frame of reference. If you want to decrease preload by 5 mm, spin the jam nuts counter-clockwise to (in my case) 17 mm threads remaining and lock the fork caps back on at that point. No cutting spacers, and Bob's y'er Uncle. .

 

BTW - As long as y'er at it, it's an ideal time to check the air gap. In your case, I'd be more concerned about having the right and left the same than I would be about the height (as mentioned above, with those stiff springs, y'er not riding on the air spring much, anyway), but that's just me. With springs and retainers out and the wheel blocked up at full bottom-out (fork tube scrapers against the lower fork castings), measure the oil level from the top of the stanchions. It should be 100 mm, measured not at the front or aft, but on the "side" of the stanchion. If they're within ~5 mm of this point, it'll be fine. Wilbers instructions refer to it this way: "Luftkammer = 100 mm". Ya just gotta love that term, ja?

[MickM]

Mick, I forgot to mention that many Marz forks (including my 40 mm USD's) have a provision for infinite preload adjustment within (I think) 10-20 mm or so. When the fork caps come off, (back compression & rebound damping adjusters off full counter-clockwise first -- don't ask me why, this is wot the Guzzi manual calls for ), you'll find the fork caps threaded to the cartridge rod assemblies and locked in position with jam nuts just beneath the caps. If you crack them off and leave the jam nuts where they were from the factory, take a measurement of the remaining free threads on the cartridge rod assemblies (mine were 22mm). Assuming they haven't previously been meddled with, you have a "factory setting" starting point for a frame of reference. If you want to decrease preload by 5 mm, spin the jam nuts counter-clockwise to (in my case) 17 mm threads remaining and lock the fork caps back on at that point. No cutting spacers, and Bob's y'er Uncle. .

 

BTW - As long as y'er at it, it's an ideal time to check the air gap. In your case, I'd be more concerned about having the right and left the same than I would be about the height (as mentioned above, with those stiff springs, y'er not riding on the air spring much, anyway), but that's just me. With springs and retainers out and the wheel blocked up at full bottom-out (fork tube scrapers against the triple clamp), measure the oil level from the top of the stanchions. It should be 100 mm, measured not at the front or aft, but on the "side" of the stanchion. If they're within ~5 mm of this point, it'll be fine. Wilbers instructions refer to it this way: "Luftkammer = 100 mm". Ya just gotta love that term, ja?

 

Hey, thanks for that ! Had a look at the w/s manual to find the way in which the top bits go together but didn't realise there was any adjustability in it. My forks have never been opened so makes me wonder if the factory assembly may be a bit hit and miss and mine was set at the upper range of available preload ? I've now done a zip tie test and even under the most aggressive braking I'm game to attempt there's 22mm of leg exposed. While the internal bump stops are obviously set to prevent the base castings getting into the stanchions, I'm clearly some way from bottoming. Be interesting to check what distance, springs aside, represents absolute full bump ? So no question, the springs are too stiff .... it does seem from several comments I've read in the archives that Guzzi fitted a range of springs for whatever reason and you can't know what's in there until you measure them. Once I get it apart I'll do a crude rate test using my shop press with bathroom scales. Appreciate the comment on oil height as that's clearly a better idea than using specified volume. Thanks once more.

 

As an aside I was ogling a Ducati Sport 1000 on Saturday (the dual seat one) and was thinking it was pretty swish .... then thought about the desmo drama, then the chain and how my wife would winge about muck on her jeans. Pretty quickly my mind turned to pushrods, a shaft and easy cleaning and I walked out very content with what I've got. I think it's a healthy thing to ask yourself sometimes why we all bought Guzzis in the first place .......