why would moving more fluid build damping faster? when your all your doing is displacing fluid? be it a 12mm or 12.5...14mm 16mm shaft?? I'm not saying your wrong...far from it...I'm just curious??Originally Posted by Robert Taylor
Forum whore
why would moving more fluid build damping faster? when your all your doing is displacing fluid? be it a 12mm or 12.5...14mm 16mm shaft?? I'm not saying your wrong...far from it...I'm just curious??
Moped rider
The compression adjuster is between the main body and the gas (and oil) reservoir. So for the oil to flow past the compression adjuster oil must be forced from the main body in to the reservoir. What does this is the shock shaft entering the main body effectively making the volume of the main body smaller. There is a small amount of travel that is consumed before full damping is realised as the oil starts to flow from the main body to the reservoir past the compression adjuster as a function of shaft displacement.
So if you have a bigger diameter shaft it moves more oil faster, this in turn means that you have a smaller amount of travel before full damping force is realized. Hence a bigger shaft builds damping faster.
Kiwi back at home!
It is interesting to note as how expendable income increases more and more bikes are coming out up-specced to include niceities such as ohlins.
S Model Ducatis. Factory Aprillia. The SP R1.
And with that you get a quality product cheaper as economies of scale mean that an SP is cheaper than the sum of its extra parts!
Forum whore
Robert, the factory fitted Ohlins forks on such models as Aprilia RSVs, Ducati 999s etc, what's your opinion on those?
Forum whore
yep...understand the concept...and the general workings of it...but at the end of the day...for a givin shaft size a shock will be tuned a certain way to get a certian result...within other perameters of course...but you are still displacing fluid,to get resistance...and valving of sorts to achieve this...
eg...if you have a 20ltr bucket and a 10litre bucket...both full of water...throw a brick with a theoretical volume of 500mls in each...you will displace 500mls out of each??
Forum whore
Lets look at it from a different angle. You have two graduated vessels with the same amount of fluid in each. You also have two shock shafts of identical length, one though is 12mm diameter and the other is 16mm. You drop one of each into each vessel, which vessel now has the highest high tide mark?
Remember that shock absorbers have a set fluid capacity. If as TDC eluded to, if you move the fluid faster ( through the compression adjuster ) you will create more damping. For any given amount of shaft movement a bigger diameter rod will move more fluid.
To test the shaft speed theory try pushing a door faster and faster that is fitted with a closing damper.
''Displacement damping'' is exactly how 99% of production and aftermarket shock absorbers work. The problems inherent in this long standing technology include trying to successfully control the torque induced squat that modern day high horespower / torque Superbikes will impose on them. Because damping doesnt happen to an appreciable degree until the shock is moving it is in simplistic terms always playing catch up after the force placed upon it. That means that the internal damping calibration ( shim stack opening pressure, bypass bleed jet selection etc ) has to be a firmer than ideal. That ultimately is a factor that limits maximum available mechanical grip.
Taken straight from MotoGP technology the new Ohlins TTX36 has only a 14mm shaft and ( almost) doesnt rely on shaft displacement to ''build'' damping. The main shock piston is a solid slug with no shims on it and it forces fluid through an internal recirculating twin tube design, flow through the side loading compression and rebound adjusters ( which have the shim stacks ) is five terms more than a conventional shaft displacement damper. The moment that shaft moves the damping is instant. That in turn means that the damping calibration can in fact be softer meaning more mechanical grip, more sidegrip equals more corner speed, equals more exit speed etc etc.
Sam Smith debuted these shocks late in our road race season, winning all races with it against some very aggressive race sharp experienced Aussies. And ''Crash kid Seaton'' won first time out in Superbike at Manfield, breaking the long standing lap record. Until he started to slow because of the pain from his busted shoulder he had the length of the pit straight lead on his own team mate. These results with out of the box settings to be further optimised.
When Ohlins start making commercially available fork inserts using TTX technology that will be wonderful. Of course they are already being used in MotoGP.
Forum whore
Yes, good. Use the same hardware as the aftermarket Ohlins. But the Italian test riders always insist on internal damping settings that ( obviously ) best suit their smooth fast Autostradas and first world Euro roads. And that of course is the main market, we are but a drop in the ocean in comparison. For our tight twisty and bumpy roads that riders prefer to ''scratch on'' we can further optimise the internal settings. To date I would personally have recalibrated about 70 pairs.
In any event, that the tolerancing is more precise and there being a lot less friction these forks can get away with firmer settings.
The product is very tunable and small fiddly internal setting parts are available that are otherwise not available with oem suspension eg shaft bleed jets, high speed poppet springs etc. For those reasons tuning of oem shocks is always limited. If we were comparing airplane to airplane we would be talking higher attainable altitudes.
This reply highlights that we provide full and proper back up, when asked for. We have a handful of dedicated suspension technicians ( and it will remain a handful ) who I can entrust to do such work and converse directly with me. People that do such work need to be very dedicated, have all the equipment ( much of it Ohlins specific ) , machining / processing skills, Ohlins specific servicing and set up techniques / precautions etc etc. NOTE, resellers of this product are not neccessarily service techs!
A post will follow later detailing my concerns about some appalling work being done around the country and ''five minute experts'' misrepresenting that they have the knowledge and skills to service Ohlins ( indeed any ) suspension units properly
Forum whore
Ahhh, I figured they would be good stuff given the price premium on their bikes... I assume the R1SP is good gear also.
When you buy an RSVR or 1098, do they spring it to suit (your weight and riding style)? Or is that still something that requires a little aftermarket fettling by someone like yourself? I'd hope for the $30k that would be something they'd offer as standard?
Forum whore
No, it is like buying any bike off any manufacturer, no spring options supplied. The higher price for a bike reflects the higher standard of oem components ( and lower volume production for the bikes you quote ) and it is not as if dealer margins are wonderful. In fact there are many people who have opened motorcycle shops thinking they were going to ''make a killing'' Then the reality dawns that it is actually a very complex ''dog eat dog'' trade with tight margins, very tight margins on the bikes themselves. Compounding that a current environment that is levying / taxing / bleeding small business dry. If you are a franchised dealer you have to beat to the distributors drum, it is not all wine and roses. And try 70-80 hour weeks if you have the mentality to do the job thoroughly.
If you have seen ''in pit garage shots'' recently of MotoGP you might have seen the odd guy wearing an Ohlins shirt. These guys are techs assigned to the top teams, who have paid a not insubstanial sum to Ohlins for a service contract. You purchase the tools of trade and then you purchase the services of a trained specialist tech. Be it racing or a guy buying a bike from a shop. The retail margins just do not allow for such extra foc support, especially when the market at large demands lower and lower prices.
I eluded to this in a very recent Kiwi Rider article.
Moped rider
I think I understand the point you are making.
Thanks to Robert's beaker analogy we understand that a larger diameter shaft displaces more fluid for a given stroke. The thing that has not been explained given you "or a givin shaft size a shock will be tuned a certain way to get a certian result" comment, is that it seems to be a rather constant amount of displacement / oil movement required to get the compression circuit working properly, regardless of most other design factors.
We keep repeating that a large shaft shock will travel less distance before building damping than a small shaft shock. Now lets consider the tuning effects you alluded to of this phenomenon. With a smaller shaft size the shock will travel further before building damping, the key thing is that the unsprung mass (unsprung mass = the weight of all of the parts swinging up and down controlled by the suspension) will have developed quite a bit of speed while waiting for the damper to apply control to the unsprung mass. By the time the shock apples its force to the unsprung mass (or has built damping) to apply the desired levels of control to it, unfortunately the unsprung mass now has built a lot of inertia and in fact is getting to be like a runaway train. This in turn means that the shock must now apply more control forces than would otherwise be necessary (if it had less dead stroke, or took less time to build damping) to the unsprung mass to bring it under control. This means that the shock is always playing catch up with the unsprung mass. So to answer your question in a round about way, yes they are tuned to suit the design, but as a rule of thumb the smaller the shaft size the more overly aggressive (read harsh) the damping has to be to bring the unsprung mass under control. This in turn compromises mechanical grip, tyre life, wet stability, dynamic ride height control (critical on more powerful bikes as Robert pointed out). Worse to compensate for the overly harsh damping most OEM's fit softer than desirable springs to try and hide the above described effects and keep your kidneys from turning to pulp.
There are some other reasons for this are not so easy to understand at first glance for increases in the amount of shock shaft travel required to build damping. We automatically assume that the fluid in the shock is not compressible, this is however not the case. All suspension fluid has some water in with the oil (lower grades of fluid tend to have a LOT more) this enables the fluid to bind with gas molecules which makes it slightly compressible further delaying the on set of compression damping for a given shaft displacement.
Worse again most OEM shocks have a bladder to separate the oil from the gas (Öhlins uses an impervious aluminum piston with elaborate sealing measures) but in a very short space of time (just a few thousand K's) the gas starts to migrate through the bladder and dissolve in to the oil, making suspension fluid more compressible and enabling the onset of cavitation at higher shaft velocities.
These are just some of the reasons why the best adjusted OEM suspension in the world simply does not have good or in many cases acceptable performance. If by some miracle of production tolerances etc it does, sleep well in the knowledge that it will only be a fleeting thing....
Would you like some CANDY!?!?!
Really? I am not in disbelief, but some elaboration would be enlightening. Are the high/low speed damping adjustments that have appeared on say, the front of the R6 and the rear of the GSXR for show and not go? I've never thought to mess with the adjustments anyway.
But make them simple words, my mind is weak*.
Also, in regard to oil filters, I just recently purchased a Suzuki genuine oil filter, it was $15. How could anyone bypass a $15 filter? That's less than a tank of gas for most bikes. Crazy to think anyone would bother with any other part at that price.
* Just kidding, your pitch has been spot on so far. Keep it coming, it's very interesting
Forum whore
That is a brilliant description of the whole mass and momentum issue that we are always trying to control. Exactly why ( were money supply and rules allowing ) lightweight wheels ( etc ) can be so beneficial.I think I understand the point you are making.
Thanks to Robert's beaker analogy we understand that a larger diameter shaft displaces more fluid for a given stroke. The thing that has not been explained given you "or a givin shaft size a shock will be tuned a certain way to get a certian result" comment, is that it seems to be a rather constant amount of displacement / oil movement required to get the compression circuit working properly, regardless of most other design factors.
We keep repeating that a large shaft shock will travel less distance before building damping than a small shaft shock. Now lets consider the tuning effects you alluded to of this phenomenon. With a smaller shaft size the shock will travel further before building damping, the key thing is that the unsprung mass (unsprung mass = the weight of all of the parts swinging up and down controlled by the suspension) will have developed quite a bit of speed while waiting for the damper to apply control to the unsprung mass. By the time the shock apples its force to the unsprung mass (or has built damping) to apply the desired levels of control to it, unfortunately the unsprung mass now has built a lot of inertia and in fact is getting to be like a runaway train. This in turn means that the shock must now apply more control forces than would otherwise be necessary (if it had less dead stroke, or took less time to build damping) to the unsprung mass to bring it under control. This means that the shock is always playing catch up with the unsprung mass. So to answer your question in a round about way, yes they are tuned to suit the design, but as a rule of thumb the smaller the shaft size the more overly aggressive (read harsh) the damping has to be to bring the unsprung mass under control. This in turn compromises mechanical grip, tyre life, wet stability, dynamic ride height control (critical on more powerful bikes as Robert pointed out). Worse to compensate for the overly harsh damping most OEM's fit softer than desirable springs to try and hide the above described effects and keep your kidneys from turning to pulp.
There are some other reasons for this are not so easy to understand at first glance for increases in the amount of shock shaft travel required to build damping. We automatically assume that the fluid in the shock is not compressible, this is however not the case. All suspension fluid has some water in with the oil (lower grades of fluid tend to have a LOT more) this enables the fluid to bind with gas molecules which makes it slightly compressible further delaying the on set of compression damping for a given shaft displacement.
Worse again most OEM shocks have a bladder to separate the oil from the gas (Öhlins uses an impervious aluminum piston with elaborate sealing measures) but in a very short space of time (just a few thousand K's) the gas starts to migrate through the bladder and dissolve in to the oil, making suspension fluid more compressible and enabling the onset of cavitation at higher shaft velocities.
These are just some of the reasons why the best adjusted OEM suspension in the world simply does not have good or in many cases acceptable performance. If by some miracle of production tolerances etc it does, sleep well in the knowledge that it will only be a fleeting thing....
On a typical motocross track the rear suspension unit undergoes approximately 17,000 compression cycles every lap. Therefore by implication it also undergoes 17,000 rebound cycles.The point here is that suspension action ( for want of a better word ) ''reverberates'' between compression and rebound strokes constantly, and at high frequencies. Immediate damping response, excellent calibration of settings and the lowest possible friction in both unit and the whole moving system is a must.
The oem shock in the Triumph 675 ( great bike ) has ( for example ) the rebound damping curve from hell. The shim stack is so stiff that it would only begin to work as it should with a spring rate 70% or more higher than that fitted. So in order to make the rear end less harsh the rebound clicker has to be wound out as a ''band aid'' partial fix. The problem with that is it then becomes too ''loose'' on the excessive amount of free bleed it has now been given. This will be especially noticable as wallow in high speed slow radius corners with bumps and depressions.
So in a perverse sort of way perhaps it is just as well that nitogen migrates through the gas bladder and in combination with the unrefined oxygen molecules turns the oil into a milkshake....
The ( unwanted ) hysterisis in that and many other oem shocks is to use a pun ''quite shocking''. One big bag of cost cutting compromises.
Forum whore
it was...answered my question 100%
Forum whore
Thanks for the encouragement. This series of posts needs to move to a suspension header because the original post was about oil filters!
The current R6 forks are arguably the best oem forks available at present, if only because they have externally removable compression body assemblies. A suspension tuners delight as quick and easy compression shim stack changes can be effected without pulling the forks apart. If YMC see fit on later models to change it to bigger bore 25mm piston type then even better.
The high speed compression adjusters on these oem forks ( and shocks ) are little better than decoration and suit marketing / sales. ''Look, just like a MotoGP bike'' Very very wrong. As well as being skeptical about marketing hype I am also skeptical about what one reads in magazines. Very often what is reported is ( shall we say ) economical with the truth. Or their testers are not ''onto it''!!! Magazines are always mindful of attracting advertising dollars so dont wish to upset the manufacturers by telling it exactly how it is. Such issues are exacerbated in a small country where there is much less of a money go round.
Honest answers come from engineers who are totally subjective and will cut straight through the bu.....t. Last August I was present at an MX test session with Ohlins engineers in a Swedish forest. They were evaluating the standard WP suspension in the current 07 KTM250s prior to fitting in their first Ohlins test prototypes. The test riders reported that the WP suspension wasnt actually too bad....candid up front honesty. Of course they set about then developing their own shocks to work significantly better.
Anyway back to the R6. The dual high / low speed compression adjuster in the front fork consists of a low speed bypass bleed and needle. Nothing unusual in that, exactly as we see in normal single clicker compression adjusters. The high speed adjuster is simply a collar that sits over the shim stack with a linear wind coil spring preloading it. And that preload is externally adjustable. Great idea in principle.
Experience with Sam Smiths racing R6 was that it was very rare to have the low speed clickers any further in than 12 clicks, and mostly out a few clicks further. This to achieve best fork response / overall balance and side grip. In a road application you would have the settings softer.
The problem is that unless the low speed clicker is any more than 6 clicks out ( the suspension is harsh at these ''inward'' settings ) the high speed adjuster loses 90% or greater of its effectiveness. That is because further than 6 clicks out there is now so much bypass free bleed oil flowing that there is no longer enough fluid pressure to open the shim stack far enough for the effect of the spring tension to have any modulating effect. Think of it like a river about to burst its banks, if you can bleed away some of the water you will stop it from doing so.
We had been forewarned by Ohlins that this adjuster didnt work so well. But wanting to see it for ourselves we also tested it on our suspension dyno and on the road. In Sams bike we actually threw away all of the internal high speed compression adjuster components because it was no more than unwanted extra weight along for the ride.
This coming week I am fitting an Ohlins cartridge kit into a K7 GSXR1000, this kit discontinues the high speed adjuster for much the same reason. Our experience is also that very few people understand how to adjust such devices, even those that are designed for function rather than marketing.
Note that the new Ohlins TTX36 shock doesnt have an independent external high speed compression adjuster. As eluded to in previous posts the damping happens almost instantaneously, as TDC said you are not dealing with a ''runaway train''. Much better ''real time'' instant control means that the damping calibration can be appreciably softer. On the dyno they are indeed a lot softer, and that in turn largely negates the need for extra external adjusters.
Hope this explanation helps.....
And with respect to the original post about oil filters...not everyone does it including many oem part numbers, protective sealing in a plastic film. Thereby isolating from dust ingress and absorption of moisture from atmosphere....
Hired tool
Shit this is good reading. It's far better than a bedtime story. Thanks Robert
Ok im coming out of my closet just this one time, I too kinda have a curvy figure which makes it worse beacuse im a guy. Well the waist kinda goes in and the bum pushes out. When I was in college the girls in my year would slap me on the arse and squeeze because apparently it is firm, tight...
I wear jeans
.....if I find this as a signature Ill hunt you down, serious, capice?
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