The Robert Taylor suspension thread

[Robert Taylor]

Interesting point containing 2 posts (ie: the Suzuki rotary damper), Tim are you talking about the Rotary steering damper that originally came from the Scott steering damper? Or the traditional slide damper?

The problem with most dampers is trying to get them without wicked freeplay. Which reminds me my Ohlins str dmpr needs bleeding or a decent service.

I suppose most early/simple dampers are just orifice devices comprising little more than the adjustment needle hole. Never thought about it much.

Speed activated sounds like a good idea, but really you may be better with a variable damping to movement angle. I guess traditional dampers do this to an extent as they have to react by opening the shims which will only happen after a certain amount of travel. Hold on that's the reverse, Duh.

I wonder if the top of the line ones are nitrogen charged to avoid cavitation?

There had been talk of suspension fluid that became more viscous as you passed current through it, imagine the possibilities of uP control, but I guess that never got anywhere or was impractical.

Sorry Robert I guess you will feel a bit like you are explaining simple things to the masses who seem unable to grasp the concepts fully enough. But have enjoyed your past articles in KR. Which is good as they are otherwise totally lacking in the sort of expertise to produce said articles.

The Scotts steering damper is actually made by Ohlins, Scotts just make the fitting kits and market the package rather well. Ohlins make approximately 10,000 per annum for Scotts and to that end instal a Scotts etching on the top faceplate. Many have tried to copy and there is something about anodising colours that look like a cheap tart that attracts some customers. But they havent emulated the quality, performance, full responsive adjustments and longevity. Indeed the presence and unreliability of the cheap nasty ones has created more of a market for the Ohlins / Scotts dampers as people have come to realise they would have actually saved money by purchasing the ''real deal'' in the first place! Sorry if that sounds one eyed, but this is exactly what has happened.

A steering damper doesnt work on displacement like a conventional shock absorber, it just moves fluid from one side of a chamber to the other through a restricting adjustable needle into a bore. The principle is simply progressive, the harder the deflecting influence the harder the damping, which it needs to be, within sensible well tested design limits. The rotary dampers ( Ohlins / Scotts ) introduce external low speed and high speed compression adjustment, but frankly that is good for Enduro / MX and less so for road / road race. There is also a weight penalty.

Because there is no displacement of oil as in a shock absorber there are relatively no ''pressure balance'' issues that are often crudely dealt to by raising the gas pressure. The trouble with raising gas pressure is you can significantly raise friction because the lips of the seals are pressed harder and harder onto the shaft. That can be significant.

In truth in a steering damper any pressurisation only needs to be very very slight and nitrogen gas pressurisation is overkill. Ohlins have very successfully done it with an expansion reservoir and checkvalve poppet for many years. And it is the predominant damper in road racing throughout the world. For the most extreme hot conditions ( very rare here, perhaps Paeroa street races ) there is a further elegant solution they have of a simple floating piston preloaded by a very light spring, i.e just a very light ''whiff'' of preload to compensate for heat induced expansion, and to prevent cavitation without inducing seal drag.

Beware of touchy feely marketing lines like for example ''speed activated'' etc. Usually employed by companies who are in fact doing nothing new or clever and are trying to gain marketing traction.

Your Ohlins damper does indeed need servicing as it has probably gone through a few million cycles by now. If it was a cheap one it would often be throwaway. We have the proper service kit to do the job, the only one in the country.

[Robert Taylor]

yeah read about the idea in the early 90s but heard little more about it.

Having a simple harder/stiffer may be of little use as the valving would have to exponentially change with the increase in viscosity, unless the change was pretty subtle it would leave the high speed damping too stiff on 'sport setting' and low speed too soft on 'comfort'. Heck my stepmahs Laser car had dash push button (orifice) adjustment in early 90s

Actually depending on use maybe around town it wouldn't matter too much if the compression damping was bugger all in your people mover. On a bike it would be a drag as lack of low speed compression damping makes the bike fairly unsettled esp in side to side transitions.

Yes, you are onto it. Motorcycle application throws in a load of complex issues and really this stuff is not yet developed well enough. The fluids that ''polarise'' are also incredibly expensive.

[Pumba]

Man this stuff is gold, keep it comming Robert this great reading.

Now where did I put my cheque book.

[Robert Taylor]

Thanks Robert.
It must feel like you are talking to a bunch of cabbages sometimes but rest assured this stuff is gold to most of us.....even if some of it does get lost in the translation. You know better than anyone how much crap is spruiked by salesman so it's a rare and much appreciated opportunity for us to pick your brain for unbiased information. I'm off to scrub the top mount transverse type steering damper off my list of trademe/ebay searches, thanks mate.

Now, about those teenage daughters.....

No not at all, this in part makes me semi accessible as I am so busy at race tracks it is almost to the point of rudeness. Just dont expect my response to any questions to always be as quick as I have achieved recently.

My daughters are going to grow up to be tories, just like me. Any candidates for their attention must be first able to handsomely pass a written multi question test. Following that a viewing of my small arms locker.

[Sketchy_Racer]

Hi there Robert

Thanks for the professional insight you give to suspension tuning. There is some really, really cool information there.

And you show you know your product inside out, which is better than any marketing scheme i've ever seen.

Now, i race a RS125 and im getting to a point where im wondering if suspension would start to make a difference.

To give a perspective of my riding level, im 3.3 seconds off the lap racord.

Now i have just replaced the three year old tyres with some new ones, and thought now the time to think about suspension.

Currently, i have dont Zero setup (not even setting sag) and i am on standard settings on everything.

How much of a difference to lap times would setup make? Am i talking points of a seconds. Or seconds as a whole?

Cheers,

-Glen

[F5 Dave]

Interesting, thanks for the response, must fire the damper up when i get the 500 near back on the road (project), but then I'll also be looking at the rear Ohlins starting with the spring which using my scales & a press appears at only 5.5kg, seems way too low, initial (gentle) test ride didn't seem too bad but I'd suspect 6.5 would be better for a 150kg bike with a overall ~2.2 ratio, but we'll see in a few months.

Talking of enduro bikes & dampers I'd love to try a damper on my GasGas, people rave about them but it is hard to see the benefits until you've tried one. Funny I had seen the Scotts advertised as such & then they later appeared with Ohlins on them & I assumed they'd bought the company.

Glen I hope at least the bike still doesn't have Si's total FB spring on it, he'd have to be 30kg heavier than you. Plenty of decent articles on the web for a starting point for setup, although Kevin Cameron's Sportbike Performance Handbook is a great starting point. (Eric Gorr does a great dirt one too).

[SPman]

Is this one of the best threads on KB at the moment, or what!

With regard to the "Ohlins" twin shocks on XJR s, are they re-buildable, or is it better to junk them and fit genuine Ohlins or Hagon rear shocks and/or springs better suited to weight?

[jimbo]

Hi robert,I have been following this thread since the first post.Excellent.Ive learnt more about suspension in the last couple of weeks than in the previous 3 decades. many thanks.Please continue

[TDC]

Is this one of the best threads on KB at the moment, or what!

With regard to the "Ohlins" twin shocks on XJR s, are they re-buildable, or is it better to junk them and fit genuine Ohlins or Hagon rear shocks and/or springs better suited to weight?

Ohhh Nooo don't fit Hagon (or mention) rear shocks or Robert will stop talking to you

[Sollyboy]

Robert, I was looking at an earlier aprillia 1000 with oem ohlins forks fitted , but on closer inspection found the general build quality of the forks to be very poor , like poor machineing and casting etc , are there a few grades of ohlins product round cause just looking at them they looked terrible, would they still perform ok if their a second grade product?

[Robert Taylor]

Hi there Robert

Thanks for the professional insight you give to suspension tuning. There is some really, really cool information there.

And you show you know your product inside out, which is better than any marketing scheme i've ever seen.

Now, i race a RS125 and im getting to a point where im wondering if suspension would start to make a difference.

To give a perspective of my riding level, im 3.3 seconds off the lap racord.

Now i have just replaced the three year old tyres with some new ones, and thought now the time to think about suspension.

Currently, i have dont Zero setup (not even setting sag) and i am on standard settings on everything.

How much of a difference to lap times would setup make? Am i talking points of a seconds. Or seconds as a whole?

Cheers,

-Glen

In truth the biggest immediate improvements are going to come from those newer tyres and your own personal riding development. As will ensuring you stay lean and mean and sharp. Ie no mind altering substances etc.

Optimising what you have will give more mechanical grip and an improvement in your speed. But it is as much about a term that the Japanese go on about all the time, ''rider feel''. If you are getting good feedback from your supension and feel ''connected'' to the track then that raises your confidence level to push harder. There is no magical setting that suits every track without adjustment, and for the very top riders we have different internal valving settings for differing tracks. Riders are different also, some give excellent feedback ( Sam Smith, Craig Shirriffs ) some just as excellent but you have to put up with their fiery attitude issues ( Shaun Harris ) Get well Shaun so I can remind you that your politics suck (!)

There is another aspect of suspension tuning that is most specific to the 125's. That is, a dynamic ride height that optimises fairing attitude through the air and maximises top speed. Or to put it another way if the fairing is not correctly positioned for the air to pass over it with as little possible drag then you will scrub off speed. As 125s dont have excess horsepower you look for everything possible to optimise speed. Perhaps this pre-occupation is more relevant to fast flowing Euro tracks but it still bears thinking about. And for the committed actually testing it on tracks such as Pukekohe. Looking at peak revs will be some form of indication.

At least from the Ohlins perspective the preload on the rear shock spring should be set so that the rear end is just topped out ( no static sag ) And to the best of my memory rider sag fully kitted sitting in race position around 15mm. But on our bumpy low grip level tracks that might well produce bad bump absorption characteristics and limit the ultimate amount of mechanical grip available. If you cannot achieve an approximate correlation of zero sag and approximately 15 rider your spring rate is incorrect for your personal stats. The front dynamic ride height will also influence fairing attitude.

As much as for reasons like the above it is impossible to pre-calculate how much improvement there will be in lap times, there are too many variables. And the best shock absorber available isnt going to gift you more speed if it is not sprung and set up properly.

There are other forms of racing where the suspension set up becomes subservient to other factors. Formula Ford race cars are low horsepower and very often you tune the supension to take away grip as too much speed is actually scubbed off by having too much...Our own Toyota racing series cars are a proper aero function car, at high speed the rear wing produces approximately 2 tons of downforce. The suspension setup is basically subservient to maintaining correct overall chassis attitude for best aero function ie minimum straight line drag in harmony with maximum downforce.

Its a long story but we ''inherited'' the dampers on these cars, built by a company in Italy who used 30% Ohlins parts content in them and the other 70% a hodgepodge of badly engineered cheap and nasty parts. Suffice to say when these landed on my doorstep I hit the roof and complained to Ohlins, the result being the Italian Ohlins distributor got canned. The second result being we re-engineered them to attain a better level of performance and the expected reliability. That being achieved we changed the internal setting of these for the last season, it is a control class so all dampers have to be exactly the same. I got criticised by some armchair critics because the cars didnt look like they were riding the bumps as well as they had the previous season. That was perfectly true but also true was that the cars were faster because of better aero function....

Anyway, 125 road race shocks. The ultimate limiting factor is the valving in the stock shock is none too clever and nor is the response range of the clickers. The end result is a little akin to ''fixed orifice damping'' It works, but only to a certain level. Ohlins dont assemble for resale road race 125 dampers. The odd TZ125 Ohlins damper you have seen we built off the spec card from production parts ex Ohlins. In the case of the RS125 the cylinder head of the shock ( the main casting that all else assembles to ) is only available as a part from the Ohlins racing department. Because it is very low volume it is high cost and that elevates the price of the shock unit to $1750, were I to make a decent margin it would ( should ) be more. Having said that I have 3 under construction at present. A well set up one of these will ultimately help you lap faster, there are those who will say dont bother. That is probably true at this stage because there are other more immediate areas that will give you a better bang for buck. But the detractors would also benefit were they to fit the product, so be wary of sweeping statements economical in considering fairly the full perspective .

[Robert Taylor]

Is this one of the best threads on KB at the moment, or what!

With regard to the "Ohlins" twin shocks on XJR s, are they re-buildable, or is it better to junk them and fit genuine Ohlins or Hagon rear shocks and/or springs better suited to weight?

They technically are, but not economically. Normally the chrome on the shafts pit easily and this is not always visible immediately. If so they are throwaway. The shafts are Japanese with a low grade chroming process, longevity is not expected because the bikes are basically legislated off the road after only a few years. Inbuilt obsolescence.

And we are taking them here...

The genuine Swedish product has good quality highly refined steel and proper pre-chroming and chroming processes. I have pulled apart Ohlins twin shock MX shocks nearly 30 years old and often re-installed the same shafts.

The proper Swedish listing is a very different animal to the ''Japanese domestic market consumption only'' model. The parts are entirely different with respect to quality and dimensions, and the ''sum of all those parts'' performs as it should with a proper damping curve. Appropriate springing is always fitted for the individual rider and loading.

With reference to another post answering your question I would indeed talk to you if you bought cheap shocks, but youd probably be seeking conversation with your chiropractor first and foremost.....Remember you only get what you pay for.

[FROSTY:Me]

Just a point here for all those using Roberts services.
Being able to give him informed feedback will mean you'll get best bang for buck from his trackside services.
Having notes clearly showing what suspension settings you are using really are like gold.

[limbimtimwim]

I've read conflicting things about this. Is altering the viscosity of the fluids in suspension components a valid way of changing their behavior for the better?

I can understand if I filled my suspension with treacle it would be terrible, and likewise I guess if I filled it with something very thin the suspension wouldn't do much except bounce around.

But are smaller changes something that can be done to alter characteristics for the better?

[Robert Taylor]

Robert, I was looking at an earlier aprillia 1000 with oem ohlins forks fitted , but on closer inspection found the general build quality of the forks to be very poor , like poor machineing and casting etc , are there a few grades of ohlins product round cause just looking at them they looked terrible, would they still perform ok if their a second grade product?

The forks you mention are as individually anonymous to me as your own personal identity.

The only second tier ''Ohlins name only'' products ''available'' are the ones fitted to some Yamaha models that were built for Japanese domestic market consumption only and never intended for export out of Japan. The majority shareholder in Ohlins flexing its muscle, and NZ ( as a country of often ''challenged'' thinking ) is taking cast offs.

Not all Aprilia models have Ohlins forks. Right at this moment I have both a set of Aprilia Ohlins forks to service and a set of Showa forks from a cheaper Aprilia variant. The work instructions for the Showas is to rework them internally to take away harshness and get them to ride the bumps better, to match the rear Ohlins shock that has been fitted. I looked at both of these sets of forks this afternoon side by side and would have to say that the ''external'' quality looked great on both of them.

You say ''an earlier Aprilia 1000 model'' but no elaboration of overall condition. The Ohlins product on those Aprilias is fairly chunky in construction but very poor? First and only time Ive ever been told that, maybe as an engineer ( started my carreer with aircraft ) my perception of quality is different to yours....

Point of fact the overall quality is very very high and so is the ultimate longevity. Much more so than a Japanese fork the overlap where the lower tube threads into the lower castings is substanially longer and stronger than in a Japanese sportbike fork. There are 2 current popular litre class Japanese sportbikes that will develop movement between the lower tube and bottom casting over time, especially if the rider likes pulling wheelies and is a late braker. When that happens it is a costly job. The Ohlins forks never develop that problem but if you bend a tube you can replace just that tube only as it is designed to be seperated from the casting. And guess what, cheaper than a Japanese fork to rebuild...

Ohlins road and track forks also flex less under heavy braking and therefore ( the great disadvantage of inverted forks ) will not bind as readily. In inverted forks there is a bushing just above the oil seal and a second bushing further up roughly located halfway between the upper and lower triple clamps. The upper fork tubes can actually deflect a horrible amount under heavy braking meaning the bushings are no longer on the same centreline. The Japanese ''engineering by accountancy'' semi fix is just to increase clearances.

For all their limitations ''right side up forks'' remain a lot more compliant under conditions that induce fork flex, simply because the primary bending moment is happening above the bushings...

Cynically, I would suggest the ''lighter and lighter'' trend with modern Japanese sportbike forks also has a little to do with material costs. Many of these latest sportbike forks are very nicely ''turned out'' on the outside but
underneath the outerwear can hide a whole load of horrible compromises. As one overseas road race suspension tuner I know will reluctantly testify, ''she wasnt a girl''.

The new coatings do indeed work, but only when mated with either genuine seals or the very highest quality aftermarket seals who supply to oem. The coating itself is only virtually a wafer thin ''veneer mist'' Looks like MotoGP but thats where it stops.

So we go inside the forks, theres one brand of litre class bike that for years has had a cartridge with a top bushing that is not on the same centreline as the out of round cartridge tube. To exacerbate that ( and this is common to all the oem stuff ) when the cartridge is bolted in it almost always cocks a little to one side because the lower casting surface it abuts against is not perpendicular to the fork tube! AND... one of the current crop of 600 sportbikes has the cheapest nastiest front fork cartridges that you have ever seen. As a term of relativity last years cartridges look as if they would have come out of the Ferrari factory ( although that rather flatters them ) This years look like a lowest level budget replacement that would be made in China for resale by SuperCheap auto.

As an aftermarket company with a reputation for quality, engineering and performance excellence Ohlins pay very close attention to precise tolerancing and assembly truth. And the product is very tunable with an enormous setting bank of information readily accessible from the factory and other distributors. Point of fact we have our own database of knowledge and experience to further optimise the product performance for our often nasty road and track conditions.

Last year Yamaha Motor Australias road race team raced with YZFR1SP's, equipped standard with Ohlins suspension at both ends. A very high baseline to start from. They wiped the floor and that has continued into 07 season. The SP model is not available for 07 and they have only just started racing with the 07 model, Ohlins cartridges installed inside the oem forks.

The most ultimate quality and performance levels cost. The current Ohlins customer level Superbike forks cost around NZ$17,000 and they are still some way from what Valentino and Casey have access to. Valid only for F3 class in NZ but am happy to accept orders.....

As a side subject, with the posts that I have thus far submitted I have genuinely got a kick out of submitting material that people have valued and I thank the many who have made kind comments. As I have made and put my name to up front remarks about the abysmal quality, mediocre performance and poor backup of many cheap products I fully expect some retort by ''ghost writers'' My answer to that is I have no respect for those who make a living out of products that effectively misrepresent standards of performance and quality. And I especially have antipathy for those who provide no backup and those who are doing a lousy job through use of substandard parts, lack of appropriate tools, training and experience etc.

Is anyone having problems with adjustment range with the oem Ohlins steering damper fitted standard to the most current model ZX10? If so we are currently testing a cost effective cure that we think will improve its performance substanially.