The Robert Taylor suspension thread

[Pixie]

Sorry to dissapoint, the loss of a linkage transfers the complication into the insides of the rear shock. In terms of top level road race, linkage systems are very much in vogue, despite the external complication. Maybe another day I will elaborate.

Robert,with regards to some road bikes,I once read that some linkage systems offer little,if any, rate change.

I plotted the wheel travel versus shock travel of a 1996 Bandit 1200.
Measuring the distances at the axle and between the shock mounts,with the shock removed.I plotted 34 points,one every 5mm of wheel travel.
I found the rate was a fairly constant 2.4 to 1 over the whole shock travel.

There are other reasons for linkage systems.They may allow the use of space that a cantilever arrangement ( early Yamaha ) would occupy.Or may be purely a marketing ploy.

[Robert Taylor]

Robert,with regards to some road bikes,I once read that some linkage systems offer little,if any, rate change.

I plotted the wheel travel versus shock travel of a 1996 Bandit 1200.
Measuring the distances at the axle and between the shock mounts,with the shock removed.I plotted 34 points,one every 5mm of wheel travel.
I found the rate was a fairly constant 2.4 to 1 over the whole shock travel.

There are other reasons for linkage systems.They may allow the use of space that a cantilever arrangement ( early Yamaha ) would occupy.Or may be purely a marketing ploy.

Yes, some linkages are very linear and others quite progressive.

Current lack of time precludes writing a ''War and Peace'' length novel, but...

For any given uniform rear axle upwards velocity a link system varies the shock shaft speed. The faster the shock shaft speed the greater the damping force. This progressivity in damping force is achieved geometrically.

In a linkless system there is only a smidgen of ''geometric'' progressivity. The increase in damping force is achieved by secondary pistons and tapered needles in the WP design. ( Actually it is an Ohlins design, licensing fees being paid to Ohlins after a court case established that KTM who own WP ''acquired'' the technology in a less than normally acceptable way ).

In the PDS system now employed by Ohlins the secondary piston enters a bottoming cup with a lead in taper that gives a much more seamless transition than their first design as in the paragraph above. A triumph of simplicity.

Both systems have their merits and flaws. Suffice to say that were the linkless PDS system a great technological leap then the Japanese factories would have followed suit long ago. External complexity ( the link ) is favoured over internal complexity ( a PDS shock with lots of internal parts and more setting parameters )

Personally, I think the WP PDS shock is a very average piece of equipment and an ex World champ that used the product will back me up on that. But those are mine and his opinions, without the need or stomach to start WW3.

So what about combining the two? NOT SO CRAZY on an MX bike. Final bottoming control on an MX bike is ''afforded'' by a longish bump rubber, really quite crude. So why not use an internal bottoming cup inside the shock with a small piston, much like you see in front forks. And make that piston tunable with a shim stack. Get rid of the 45mm long external bump rubber and substitute it with a 10mm long one, just for peace of mind. And because bottoming control is now rather more sophisticated and effective it negates the normal setting compromises with the main piston valving and selection of main spring rate.

96 and 00 retired NZMX125 champ Andrew Hardisty currently rides a Suzuki RMZ450, a bike with link type rear suspension. Initially we supplied him with a ''standard'' Ohlins rear shock, which he was very happy with. But, because I wanted to answer the question I then built him a second Ohlins shock with an internal PDS piston and short bump rubber. Because we added that I softened off the internal low speed and therefore high speed compression valving and fitted a spring one rate softer. Andrew loved the performance of this shock so much he proffessed that he wanted to sleep with it! This bike is being retired and he wants a similiar shock built for his new RMZ250.

Many MX shocks could be built in this way but of course the price is significantly higher. Many works MX bikes have this technology, including the MX2 Ohlins kitted world champion winning Kawasaki last season.

Of course nothing is as new and revolutionary as many would have you beleive. A number of early 80s Husqvarna MX / Enduro bikes had very long travel twin shocks with very minimalist external bump rubbers. These shocks have internal bottoming out cups and ( non shim type ) pistons inside them.

[F5 Dave]

In part of the lost data I had an eloquently written post (I’m counting on the data never being retrieved so I can claim this) about some random thoughts I was having on shock shaft speed. My meagre understanding is that the linkages afford somewhere just above an overall 2:1 ratio which has the advantage of slowing the shock absorber, however it would appear there was a sweet spot of ratio where 3:1 would be too steep of a ratio, perhaps as the shock needs some travel for the piston to open the shims hence is harsh until has moved this much.

As I’d stated a friend’s RZ500 has a very stiff spring & presumably a high ratio & short shock movement. One wonders if there is any hope for an upgrade but perhaps a more modern shock with shimming off the piston would react better to the high ratio? However the cost would hardly match the bike.

as an aside my understanding is GP bikes, for a while at least - trying to combat the ‘stiff frame & suspension doesn’t move much when leant right over’ patter had a slight falling rate at some point built in.

[DMNTD:Me]

A special thank you to you Robert for providing springs,valving and setting up my ZX10 this week (Came from Bay City mc).
I genuinely appreciate it mate

[Robert Taylor]

In part of the lost data I had an eloquently written post (I’m counting on the data never being retrieved so I can claim this) about some random thoughts I was having on shock shaft speed. My meagre understanding is that the linkages afford somewhere just above an overall 2:1 ratio which has the advantage of slowing the shock absorber, however it would appear there was a sweet spot of ratio where 3:1 would be too steep of a ratio, perhaps as the shock needs some travel for the piston to open the shims hence is harsh until has moved this much.

As I’d stated a friend’s RZ500 has a very stiff spring & presumably a high ratio & short shock movement. One wonders if there is any hope for an upgrade but perhaps a more modern shock with shimming off the piston would react better to the high ratio? However the cost would hardly match the bike.

as an aside my understanding is GP bikes, for a while at least - trying to combat the ‘stiff frame & suspension doesn’t move much when leant right over’ patter had a slight falling rate at some point built in.

There is an Ohlins listing, now out of production, but we have built over the years a handful of these shocks off the spec card. People have valued these bikes enough to justify the cost and the very real performance improvement. The valving inside the original ''gap filling device'' is little better than a checkplate.

I still have the very compressed front wheel off my one that I comprehensively wrote off. If emulators had been available at that time I am sure the wheel would be compressed a few less centimetres!

Your text re link ratios is essentially correct. Many of the later Hondas also have a start ratio that requires stiff springing, this seems to go round in circles, many ways of skinning the cat.

[F5 Dave]

Careful Robert people will think you've actually ridden a bike.

Yeah he'll probably be up for a shock when he finishes the project (has been some years already haha), forks are upside downies & 17" wheels with a zillion kilos removed. Will be considerably nicer than the std fair so will be worth spending some money on, if not the full boogie spec.

Many shocks seem to wear out the hard anodising of an ally body, has nickasil plating become popular as a bona fide repair/upgrade? Maybe at that point the cost doesn't warrant continuing on top of a kit.

[Robert Taylor]

Careful Robert people will think you've actually ridden a bike.

Yeah he'll probably be up for a shock when he finishes the project (has been some years already haha), forks are upside downies & 17" wheels with a zillion kilos removed. Will be considerably nicer than the std fair so will be worth spending some money on, if not the full boogie spec.

Many shocks seem to wear out the hard anodising of an ally body, has nickasil plating become popular as a bona fide repair/upgrade? Maybe at that point the cost doesn't warrant continuing on top of a kit.

Please dont tell anyone, it is a past life. I used to like riding them, before I became much much more excited about the supenders on them.

Usually when you get to see a ''bellmouthed'' body tube it is too late for any form of recovery and any of the plating processes are quite expensive, tolerancing is also a big problem.

As yet I havent evidenced anyone overseas doing this and frankly I would doubt that it will happen.

[The Pastor]

what about shimming up suspension? is this a good or bad idea?

[boomer]

what about shimming up suspension? is this a good or bad idea?

depends how short you are i guess and if ya have enough strength in ya arms and legs to get u up there.. but i gotta say .. "WHY WOULD YA?"

[kiwifruit]

I'm off to sample the TEN with its new ohlins bits, cheers Robert

[kiwifruit]

Well...
the new suspension is amazing, totally changed the bike

It has so much more grip, feels loads safer, able to gas it up earlier and lay it down much harder. Heaps better under brakes, feels solid tipped over, no more skipping around.....
Really starts working well at higher speeds on closed private twisty roads.
Can't rave enough about it.

Twas a salubrious weekend

[Sanx]

closed private twisty roads

Ah yes - the 'closed' roads ...

[Robert Taylor]

what about shimming up suspension? is this a good or bad idea?

Internally or externally???????????????????????????????????????? ???????????????

[The Pastor]

Internally or externally???????????????????????????????????????? ???????????????

your the expert not me, ive just heard about "the coin trick" andive been trying to find some information on it to no avail.

My understanding would be internal - but what would i know.

[Robert Taylor]

your the expert not me, ive just heard about "the coin trick" andive been trying to find some information on it to no avail.

My understanding would be internal - but what would i know.

Tell me then about this ''coin trick'' .