Damping Technology

[xwhatsit]

how would you know its better than what you have now??

I've got 27-year old Honda FVQs. Of course they'll be better.

Will have to investigate these further.

[cowpoos]

Ohlins Superbike forks use 25mm internals, and we don't use or believe in, use, or recommend 25mm cartridges unless you are stuck with them.

excuse my ignorance. on this subject at times..but why is it you do not recommend use of 25mm cartridges?? I realise your AK20 kits are a 20mm cartridges [I use them on my racebike for the record]...but surely with the larger diameter you are displacing more oil per mm of travel through the piston allowing damping to build faster..I also realise the design of and the tuning has alot to do with performance..but I'm only repleying to the genralised comment you made about size...

another thing...because with the larger piston...you would be able to use larger shims...would the larger diameter shims provide a less sudden spring back under direction changes..and more progressive bending?

[vifferman]

how would you know its better than what you have now??

It's a matter of trust, until they're actually fitted and fettled and tested. So it's a risk until that happens (even with a reputable brand, which may have been set up wrongly).
Unless your current shock is totally farkt, in which case almost anything will be better.

The trust comes in a couple of flavours, the most basic of which is, "Well, I've forked out more Shekeldollarz than it would have cost me to have my existing suspension overhauled, so it stands to reason it'll be better. I hope..."
The second is, "These guys have a good reputation, one which they want to keep and enhance, so I'm paying good coin knowing that if for any reason this shock isn't what I'd hoped for, they'll put it right." This is typically right, but may not be the case if you've overstated your ability or requirements, and ended up with an oversprung, overdamped shock set up for RacerX, and with insufficient adjustment in it to make it workable for the riding you really do, which is commuting, with the occasional gentle open-road ride on shitty bumpy roads.

[Robert Taylor]

excuse my ignorance. on this subject at times..but why is it you do not recommend use of 25mm cartridges?? I realise your AK20 kits are a 20mm cartridges [I use them on my racebike for the record]...but surely with the larger diameter you are displacing more oil per mm of travel through the piston allowing damping to build faster..I also realise the design of and the tuning has alot to do with performance..but I'm only repleying to the genralised comment you made about size...

another thing...because with the larger piston...you would be able to use larger shims...would the larger diameter shims provide a less sudden spring back under direction changes..and more progressive bending?

As far as relative displacement of oil goes for any given distance of fork movement the Traxxion 12.5mm rod in its 20mm tube is the winner, at least on that score. Arguably ( and Max will beg to differ ) the response of 22mm od shims against 17mm is better. I have already seperately detailed what I see as the virtues of the bending shim stack mid valve. Then theres top out springs which we played a hell of a lot with last season, settings now adopted by Ohlins.

Sam Smith NZ600 No1 was the first to race with these cartridges and had previously raced with Traxxion that he was very happy with. He tried the Ohlins and instantly liked them better ( sorry Max ) and the settings almost one year later are better again, because Ohlins and ourselves never stop refining. There is no perfect setting!

If anyone would care to see just how incredibly easy it is to change fork springs with the Ohlins cartridges I will happily show them, this is one of the many detail features that is way cool, eliminating the pain in the butt nonsense of fiddling around with the top cap standard nonsense. No worries about setting the cap distance to equalise side to side and ensure the right range of rebound clicks etc, it winds down onto a shoulder, perfect and quick everytime. Very very well thought out and almost worth it on that score alone. Race bike suspension is also not only about performance, it is also about the ease of being able to make setting changes quickly and effortlessly.

TTX concept gas charged Ohlins cartridges in the future. Ohlins work at the very highest level of MotoGP and this technology is slowly trickling through to production.

[Mental Trousers]

The only thing you didn't roll out there are the Ohlins girls. Nice plug Robert.

[JD Racing]

It is indeed very interesting and there is no textbook material about it! The Ohlins 25mm piston used in their cartridges has huge flow area and no restrictor stop plate for the shim stack. Its flow rate is greater than the previous check plate piston arrangement. BUT, it also modulates the flow by opening the door only as much as is required, not its open by this amount and thats what youve got!

The spring force on that checkplate can indeed be tuned ( within the limitations of such a system )but you are always having to be mindful of introducing harshness. As you will know, we often remove midvalves and fit check plates in mx stuff to give more compliance etc. In road and road race stuff there is only a third of the travel than mx so the damping has to ''build'' right away, not a mm or so later when the train is already runaway.

When in the Ohlins cartridges we ''binned'' the old style pistons and went to the ''mid valve'' type the rider feedback and lap times improved.

I think it's possible to come up with just as good a solution using a different approach, if you think of how the Ohlins PRX valve works and apply that to the midvalve setting you have something that builds cartridge pressure rapidly without a harsh blow off. A shim stack midvalve needs a large shim deflection to prevent harshness at high shaft velocities, this puts a lot of strain on the shims which can lead to them taking a permanent set.

[Robert Taylor]

The only thing you didn't roll out there are the Ohlins girls. Nice plug Robert.

Not intended as a plug as such, stating the relative merits. And yes many of the native Scandinavian women are not very ugly

[JD Racing]

Yes bumps are bumps and we have a very high ratio of circuits with them. I cannot answer for your circuits but we have a lot of emphasis on reducing excessive rear end acceleration squat off slow exit speed corners. Thats an area we work with lots with rear shocks. .

A lot of the problems associated with this can be alleviated by the rider getting wise with his gearing and his engine mapping, most racers think the thing has to be screaming it's nuts off to go fast, lots of engine tuners and dyno operators spend all their time looking at the wrong end of the graph, get that sorted and the thing will drive rather than wanting to wheelie and spin up.

[Pancakes]

....................... And yes many of the native Scandinavian women are not very ugly

and when you post up some pics we can see if your lying or not. heheheheh

[Robert Taylor]

I think it's possible to come up with just as good a solution using a different approach, if you think of how the Ohlins PRX valve works and apply that to the midvalve setting you have something that builds cartridge pressure rapidly without a harsh blow off. A shim stack midvalve needs a large shim deflection to prevent harshness at high shaft velocities, this puts a lot of strain on the shims which can lead to them taking a permanent set.

Yes that is so but most particularly in mx application where they use very thin shims with little support on huge ports. A racing cartridge using this principle would ideally be serviced twice a season anyway and any sacked out shims replaced. A shim stack will modulate flow in a more controlled fashion than a spring. Note that the poppet on the PRX valve has nose shims that give a smooth transition from bypass bleed choke off to opening, compensating for the semi abrupt opening of a spring.

Thick less compliant nose shims give an abrupt ''knee'' on a dyno curve, thin compliant shims give a rounded knee.

Note that the Penske high speed compression adjuster is a preloadable shim stack, in all fairness a very nice piece of kit with a wide response range.

I will talk about high speed compression adjusters at another time, recent Ohlins technology with the TTX36 range has rendered their fitment almost academic.

Moderators any chance of moving the last few posts to a new thread entitled ''Damping Technology''? It has all strayed off the original subject and I think it needs to pick up from my second response to Max.

[JD Racing]

The secret lies in using a shim to allow initial deflection opening the ports a little before the whole assembly lifts.

I wouldn't be so quick to consign high speed adjusters to your bin just yet, the TTX 36 with it's limited fitment range is the only high end shock on the market to do this. I would imagine that the through shaft TTX as used by the Yamaha factory teams in GP's and WSB will eventually filter it's way down to the street market then we'll be using high and low speed compression and rebound.

[Robert Taylor]

A lot of the problems associated with this can be alleviated by the rider getting wise with his gearing and his engine mapping, most racers think the thing has to be screaming it's nuts off to go fast, lots of engine tuners and dyno operators spend all their time looking at the wrong end of the graph, get that sorted and the thing will drive rather than wanting to wheelie and spin up.

Agreed, but also ( logically ) the engine delivery shouldnt be so softened that it is over-compensating for lack of rear shock low speed damping squat control.

[Robert Taylor]

The secret lies in using a shim to allow initial deflection opening the ports a little before the whole assembly lifts.

I wouldn't be so quick to consign high speed adjusters to your bin just yet, the TTX 36 with it's limited fitment range is the only high end shock on the market to do this. I would imagine that the through shaft TTX as used by the Yamaha factory teams in GP's and WSB will eventually filter it's way down to the street market then we'll be using high and low speed compression and rebound.

No they are not in the bin as such, its just that the basic incarnation of the TTX36 does alleviate a good part of the need for it, at least in a mass market situation where you dont have a highly skilled factory technician to hand. The TTX concept is the future for Ohlins and will filter through to other models, as much was stated at the recent Ohlins distributor conference.

Already we have been building TTX36 to order for models such as SV650 on the back of Glen Williams stunning results at the recent Greymouth street races.

The through rod damper such as TTX40 is a stunning piece of kit but does require a high level of set up skill. We adapted one to fit into one of Craig Shirriffs race bikes and won races with it.

I will elaborate further about the reality of this technology when I have a little more time. The application, costs and ability of end users to understand tuning are THE overriding factors about what ends up in the marketplace for such aftermarket products.

[Coyote]

Most of this just flew over my head.

Where do you go to learn this jargon? Do you have to take an engineering course at uni or something?

[F5 Dave]

Great thread.
Amateur side question: So shims have a service life? Presumably more so in MX applications & certain arrangements more than others (light shims mentioned). How would the punter know? How does the tech know to replace?, presumably they take a set like a worn set of reeds?