Fork Oil Change

[BrianG]

OK guys, I've been following this thread very closely.  Servicing my suspension is one of the items I have listed to do this off season. I now know that I have to replace my springs, front and rear. I weigh 230# and my MG has 17,000 plus miles and want to go through everything to improve handling   and to make sure everything is up to snuff.

 

Couple of questions for you all.

 

1. Are the Ohlins much more difficult to service than the others. My guess, yes.

2. Is it important to stick with Ohlins springs or are there other mfg. who make springs to fit ?

3. I have never serviced cartridge forks before so should I just send it all to an Ohlins service center or would someone else, like Traxxion be able to handle it?

 

65515[/snapback]

 

You will find that 1.05 or 1.10kg springs are right for you. I'm 225 lb and love mu 1.05's..... but I do like a cushier ride.

 

Cartrgdge forks all service more or less the same. I doubt that you'll find much difference in the Marz and Ohlins fork service process.

 

Spring manufacturer is no biggie. Just get a good quality spring.

 

Traxxion did my Marz forks but couldn't alter the valving and didn't like the stock units, so the replaced them with Max's new units. I'm in love! He can certainly optimize the Ohlins units.

[Guest ratchethack]

Gents, I'll admit I had a few reservations about progressive springs in the Marz forks after all the feedback on this forum against 'em. Not to stick it in anyone's eye, but thankfully, those concerns are now history.

 

To recap, I was chasing no "boy racer" illusions, just wanted a better front-end that would improve handling for mountain riding and not only NOT beat me up on the way there and back, but actually provide something resembling greater comfort. The stock .6 kg/mm springs just weren't cuttin' it.

 

As I gave the fork it's first sorting out with the new Wilbers .7 - 1.0 kg/mm springs, my concerns leaped to the forefront when I immediately ran into relatively short travel. But after discovering the overfill phenom (see previous posts) and then drawing the excess fork oil down to a 100 mm air gap, it was a brand new world.

 

I'm now getting 95 mm of travel with "inspired" riding (no holes or bumps, just flat pavement), which I figure is close to where I want to be along with shortened spacers, raised fork tubes, and targeted sag settings. So now I'm glad I stuck with what I originally believed would best meet my objectives after a lot of research and 2 prior experiences converting to progressive fork springs. The lack of brake dive has been a huge improvement, but I'm also enjoying a smoother, more compliant, yet not-at-all-soft ride.

 

In all of this, the discovery of the inherent problem of getting all the fork oil out, resulting in the overfill problem might be most helpful to others here, since I haven't seen the problem mentioned prior to this discussion. Could it be that no one's run into this before?!

 

If you've been doing it yourself - and may I say PARTICULARLY if you have a shop do it - may I suggest that you make sure that the air gap is the measurement used - not the recommended 400 ml volume. Depending on how much old oil doesn't come out (it seems to vary ) you're looking at the potential for serious air spring/hydraulic limit to fork travel.

 

Keep on truckin'

[dlaing]

Can you use up the full 120mm if you hit the brakes in a drainage dip, pot hole or speed bump?

Just to clue casual readers in on the effects of air space, here is the Ohlins graph:

[Guest ratchethack]

Can you use up the full 120mm if you hit the brakes in a drainage dip, pot hole or speed bump?

Dave, I don't have the answer to this yet, but judging from the tests I've done so far, I'm expecting that really hard, square-edged bumps will likely get it pretty close to 120 mm, if not all the way there.

 

NOTE TO OTHERS AS A FYI: Sorry for any redundance here, I'm in the process of learning this stuff as I go. (The Marz is my first cartridge fork.) Richardson (Guzziology) has helped quite a bit. For those who've been following this thread, the Ohlins air spring graph posted by Dave can be used to illustrate how overfilling affects fork action. The design of all cartridge forks are similar, and they all follow the same operating principles, so lacking a graph from Marzocchi, I'm confident enough using the Ohlins numbers as a general guide for the Marz 40 mm USD.

 

At my last fork oil change, when I followed the manual's 400 ml refill method (for the 3rd time) and at the same time installed the new springs with stock spacers, *something* was very very wrong. I found that the air space on the compression side was on the order of 60 mm, and the rebound side was on the order of 40 mm!!

 

This is so extreme that nothing even close is mapped on the Ohlins graph. Extrapolating from the sequence of air gap (oil level) curves on the graph, I estimate that at 100 mm of fork travel (stroke), 40 mm air space on the rebound side was providing an air spring force of somewhere around 500 kgf, when it should have been 240 kgf at the same stroke with the air gap properly set at 100 mm.

 

Keep in mind that the air spring force is on top of the force of the fork springs themselves, which in my case is a (slightly) rising-rate to begin with. It's pretty easy to see how the "overfill effect" from adding fork oil by volume without getting all the old oil out can result in a huge spike up in force that restricts fork travel. According to Richardson, abnormally high air pressure from too small an air gap also introduces a prohibitive amount of fork stiction by causing the fork seals to collapse tight against the fork tubes. The symptoms are a stiff, shortened fork action that approaches something close to "hydraulic lock".

 

Hope this helps

[txrider]

Here's some more general info on setting fork oil height-

 

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

[BrianG]

Can you use up the full 120mm if you hit the brakes in a drainage dip, pot hole or speed bump?

 

With only 100mm of airspace don't you run out of travel a bit shy of 100mm of travel?

 

 

ratchethack...... are you now running the Wilbers .7 - 1.0 kg/mm springs? I'm thinking that maybe I'd give the progressives a go, and swap them this winter. What spacer length did you settle on?

[Guest ratchethack]

Great additional supporting info, txrider. Thanks. I don't recall seeing this on Verdone's site before, maybe it's new? I note that he recommends making incremental changes to the air space by only 2-3 mm when fine-tuning. I had been thinking in terms of 5-10 mm changes.

[Guest ratchethack]

With only 100mm of airspace don't you run out of travel a bit shy of 100mm of travel?

ratchethack...... are you now running the Wilbers .7 - 1.0 kg/mm springs?  I'm thinking that maybe I'd give the progressives a go, and swap them this winter.  What spacer length did you settle on?

65749[/snapback]

Brian, with 100 mm airspace, so far I'm getting 95 mm of travel, but this was only with fairly aggressive street riding on flat pavement, no bumps or holes, and no "inspired" mountain riding, which is what I'll be tuning for. Per post above, I'm guestimating that as soon as I get out there for a proper "mountain test" that fork travel will go to 100-110 mm or even more without any change to the current settings.

 

Yep, I'm running the Wilbers .7 - 1.0 progressives from Todd at GuzziTech. The spacer length I'm currently using is 105 mm. This gives me 33% static and 21% unladen sag. I'll be experimenting next by stacking up the spacers a few mm with the expectation of achieving something close to 30% laden (static) and 19% unladen (free) sag to see what this is like. It might be helpful to note that despite their rating, the Wilbers progressives seem to be just "mildly" more progressive in their action than straight-rate springs, judging by their action, and the sag numbers and preload I wound up with for starters.

[BrianG]

Brian, with 100 mm airspace, so far I'm getting 95 mm of travel, but this was only with fairly aggressive street riding on flat pavement, no bumps or holes, and no "inspired" mountain riding, which is what I'll be tuning for.  Per post above, I'm guestimating that as soon as I get out there for a proper "mountain test" that fork travel will go to 100-110 mm or even more without any change to the current settings.

65752[/snapback]

 

Ok...... I forgot that the airspace is measured at full compression!

[Guest ratchethack]

Continuing the fork setup with the new springs. I dunno if it's possible to do a "stoppie" with a V11, (don't really care). But I got 109 mm of travel by cranking down hard enough on the front Brembos to get a howl of protest out of the Metzeler Z6, and it felt like the rear was fixin' to leave the tarmac.

 

This must have me pretty close to "in the zone" as far as ideal fork travel. Any opinions? TIA

[txrider]

I sent an inquirey to Traxxion Dynamics asking about general guidelines on determining correct fork oil level and here's the response I received-

 

" John,

Unfortunately, the Marzocchi forks on your V11 are some of the worse designed and functioning forks we have ever seen. The cartridge is crude at best. There is no real valving to speak of in the cartridge. The cartridge has all kinds holes drilled in weird locations, it’s a mess. So I would take the recommend oil level from the manufacture with a grain of salt.

 

The oil level is for the most part there is keep the fork from bottoming out. So if the forks bottom you need to add more oil. Of course this is all relative to spring rate. For example on one V11 we used 120mm oil level but we also had 1.05kg springs in the forks. Your stock fork springs are some where in the neighborhood or .82kg so a little higher oil level may be required to keep the fork from bottoming. However, as you have discovered if the oil level is too high then the fork will become harsh. About the best thing I can suggest is to at minimum upgrade the springs. I simply do not think you will be able to come up with a decent compromise with the stock springs. Check your sag numbers and you will see that most of the fork travel is used up by the weight of the bike. Our spring kits for the V11 are $109.95.

 

I will tell you that all the bikes we have worked on that the V11 would benefit the most from our AK-20 Kit. The stock valving is just so poor. If you want to try a set we will do a free install for you. If you can get a group of guys together for a group buy then I can get you a pretty good discount on the kits themselves.

 

Let me know if you have any interest or if you have any other questions. Thanks!"

 

This is from Mike Hardy, Sales Manager with Traxxion.

 

Then as a follow up to my inquirey on quantity of buyers required and price break he responded-

 

"John,

No problem at all.

 

As far as the group buy goes, the AK-20 Kits are $999.95 and include the Axxion Valved Cartridges, Springs matched for the riders weight, and two quarts of oil. If you can get 5 + riders committed then I can give you 10% off the AK-20 kits plus a free install.

 

The benefits I’m not sure I can even put into words. The suspension would be light years ahead of anything out there. Bump absorption would be increased by ten hold. You would immediately notice the forks would not dive to the bottom of the stroke under breaking and no more harshness.

 

We also offer a 100% money back guarantee. If you do not like the setup and agree that it completely transformed your bike then we will return your forks to stock and give you your money back.

 

If you can get a group buy together then I will see if there is a little extra love we can show on your purchase.

 

Let me know if you have any other questions. Thanks!"

 

So, there's more possibilities to making the forks better although that price is still pretty high. I'm not quite sure I'll spend the bucks for for the A-20 kit but I will buy the springs. So, if anyone is interested contact Mike Hardy at Traxxion. I have no axe to grind on this other than to improve the way my own bike's suspension works and share what little info I come across during the process.

[Guest ratchethack]

Hmmmmm, interesting. Quite a pitch. Coupla things. This'll probably draw some ground fire...

 

O' course, there's a point of diminishing returns for everyone when it comes to upgrading here. Let's assume that $1K actually buys you current state-of-the-art performance in an upgraded fork. As has recently been pointed out in another thread, with a machine that's so inherently limited in terms of it's chassis to begin with, what return of usable value can be expected? Do you (I, we) have a chassis that can actually take advantage of it?

 

There are exceptions here 'n there, but most of us aren't racing our Guzzi's. My overwhelming perception is that despite popular delusions to the contrary, for most riders, what happens on racetracks has very little to do with what happens on the road. IMHO, this is profoundly significant to the selection of tires and suspension, which are critically important to have properly set-up, adjusted and matched to the way they're actually used.

 

Let me be the first to admit it - I'm a bit of a Road Geez. Since many chassis shortcomings show up only at the most extreme kinds of conditions encountered on the track - or when the chassis is wrung out at "ludicrous speed" on the road with pegs and knees on the tarmac, I tend to keep myself blissfully ignorant of most of 'em. I'm pretty sure I wouldn't (and probably couldn't) push even a current racing chassis hard enough, and/or enough of the time on the road to the point where the latest high-zoot fork would make much of a real-world difference.

 

If the above email is any indication, the level of invective that Traxxion slings toward products they hope to replace with their own gear might be proportional to the price they expect you to pay for their whiz kit...

 

Sure the Marz cartridges are "crude at best". Frankly, relative to current racing gear, so's the rest of the bike. As was pointed out recently in another thread by a few who oughta be qualified to really know and understand, we're riding on a pile of left-over, half-baked engineering mixed in with a big dollop of left-over '60's to '80's technology.

 

If you could get 'em to continue the "candor" , what do you s'pose Traxxion would have to say about the spine frame and swingarm? How about the whopping unsprung mass of that boat-anchor bevel-drive? Then there's the rear shock... Compared to current racing tackle, the V11 is a fabulous disaster of compromises... Sow's ear, etc...all of which may in fact be hopelessly non-competitive on the track - but I reckon there's more'n just a few of us duffers who happen to find the whole mess a couple 'o giant notches above "delightfully adequate" for the road.

 

"Suspension light years ahead of anything that's out there!" Hmmmmm.......Profuse apologies to the V11 Faithful here, but to use another cliche, mightn't we be looking a little bit like putting lipstick on a pig? We're certainly virtually unlimited WRT our options, but how far is it reasonable to go with "improvements"? Let's see...If I'm not using anything remotely resembling racing tires on anything remotely resembling a racing chassis, and I'm not in fact, racing - exactly what's the point of strapping on racing forks?! Just who's zoomin' who here, Gents?!

 

I'm sure Traxxion offers very fine leading-edge products perfectly suited for the track. As far as benefits that Hardy's "not sure [he] can even put into words", well, speaking only for myself, I reckon that for a relatively low investment, I've not only covered all the basics WRT upgrading my fork with proper springs and setup, I b'lieve I've put the benefits into words in this thread (see above).

 

I don't know this to be the case here on this forum (and I'm not suggesting this), but I'm always amazed when people spend thousands upgrading a complex and highly adjustable machine before making an honest attempt to realize the benefits of what they already have by simply getting it properly sorted.

 

It seems that for many, it's less of an effort to pay someone to take the whole confusing mess away and replace it with something that they may not understand any better, but at least the new high-dollar racing gear with the latest pedigree can be presented in positive-sounding expletives with great enthusiasm by a salesman? I reckon you've gotta really WANT to believe?! This seems to be the market that the moto-aftermarketers cater to for most of their business these days.

 

Now anytime I figure I can get something like a real-world "80% improvement" into some major component of my "half-arsed" chassis for a hundred bucks and change on an upgrade, this makes perfect sense. But spend ten times that for the next "20% improvement", leaving the rest of the bike behind? - naaah, I'll pass. But that's just me, and as always, YMMV.

 

Irascible Curmudgeon signing off.

[Guest trispeed]

Hi all, I have read this entire thread and found that almost all of the info is re: pre-2003 bikes that have different forks than my 2004 V11. I have 43mm Marz. with rebound damping adj. on both sides and no compression adj. Any info re: these forks? I am geting almost 40% static sag and 25% free sag at the moment.

[Guest ratchethack]

Trispeed, the principles involved in setting the sag apply to all forks and all shocks. The discussion on air space applies the same with your forks too. Both your sag numbers are out of range according to the "rule of thumb" numbers mentioned in this thread. An easy and inexpensive way to achieve an immediate improvement in ride and start getting dialed in would be to go longer on the spacers. I'd try an additional 10 mm length and then check your sag. 10 mm might be a tad too long, but going forward, it's easier to shorten a new spacer than to add a few mm. This would more'n likely improve your ride, but you might find that the free sag would then be out of range on the low side. If this were the case, it'd be an indicator that you need higher-rate springs.

[dlaing]

"Unfortunately, the Marzocchi forks on your V11 are some of the worse designed and functioning forks we have ever seen. The cartridge is crude at best. There is no real valving to speak of in the cartridge. The cartridge has all kinds holes drilled in weird locations, it’s a mess. So I would take the recommend oil level from the manufacture with a grain of salt."

 

"Suspension light years ahead of anything that's out there!"

 

While I think Traxxion must produce an excellent product, and they have me sold over RaceTech, they sure do talk the talk!

I suspect LE and Computrack are a bit more professional....but I don't know if they make anything with tuneable regressive damping.

While a thousand dollars is a lot of money, I'll bet that suspension upgrade is not light years better, but a pretty good value for making the bike more comfortable, predictable, stable, etc.

While the frame is not the most race ready rigid thing out there, the best thing you can do for the frame is to protect it from jarring forces by installing a compliant suspension.

I love arguing with Ratchet and I my scottish ancestored half is fully inclined to agree with him, but not the Norwegian half that got blissfully suckered in by the Pretty Swedish Ohlins forks, and will get suckered into Ohlins for the rear as soon as I can clear some debt....now if I had just bought a Scura to begin with...