Wanted: Hornet 900 rear shock

[Drew]

Wot?

Guy wants a Ohlins for a Horny 900. Told him where to geot one. Got one told him how shit hot it is.

He's been in touch with RT already.

The real advantage with a linkage setup is that you can get faster shaft movement as you load it up. That means the spring rate AND the compression valving is ramping up faster as you bottom out. That's very hard to organise with a direct couple.

I worry about shit like: If shocks were under tension, rather than compression they could be a shitload smaller and lighter.

Isn't that what rising rate means? It's what I mean when I say it.

The shock has to work in both directions, why would it matter what way it goes first?

Or do you mean just the spring? The damping unit can be seperate completely, just try and design better than Suzuki did with the rotary damper. (Which I still think should work better than a shock).

[Ocean1]

Isn't that what rising rate means? It's what I mean when I say it.

Yeah, and like I said you can get that wihout a linkage, the rate change just isn't quite as much and the curve isn't quite as suitable.

The shock has to work in both directions, why would it matter what way it goes first?

Or do you mean just the spring? The damping unit can be seperate completely, just try and design better than Suzuki did with the rotary damper. (Which I still think should work better than a shock).

What I meant was, imagine if the shock had a tension spring around it that pulled it shorter. Stick it under the swingarm and mount it from the bottom of the crankcase. It's probably been done, most things have.

The reason shocks weigh what they do is they've got to take load without buckling. Things under tension don't buckle, and the tensle strength of the shaft, say, would be managed by an 8mm shaft. The mass could be less than a quarter of a standard unit.

If Suzuki coppied the rotary damper from a Morris Minor I can see how that might have been a mistake. There's a bunch of existing hydraulic actuators of different shapes and that could be used the other way around, as dampers. At least the general design could. A linear compression shock isn't nescessarily the best, but they are simple, and fairly cheap to make.

[Robert Taylor]

Unfortunately I google 46dr ohlins (pages only in NZ) and only find me talking about it .. crikey

This listing in single tube ''street performance line'' was introduced a few years back when the world economy was ''falsified'' by casino banking and brazen speculation. It didnt sell well at that time because people moreso at that time wanted the ''bells and whistles'' version. It was withdrawn from production and sale. But recently it has been reintroduced as the broken world economy is good timing for it. Considering its quality, longevity, rebuildability and the fact its a budget level shock that ACTUALLY ABSORBS BUMPS AND DELIVERS GREAT RIDE HEIGHT CONTROL it is well priced. Also inclusive of post factory setup ( by ourselves as the local NZ distributor ) for our local conditions.

[Robert Taylor]

Get the eye sizes, and buy anything the same. Then get it sprung and valved, and made the right length for the Hornet.

Can't see any reason someone would sell an ohlins shock for a Hornet unless it's written off. Given how bad the standard one is.

Thats too much of a blanket statement, it implies that anything that will closely match the fitment criteria will be able to be successfully revalved and sprung. That is ( so often ) very much not the case. If its a shock with a restrictive piston ( requiring replacement ) and unsuited spring rate then the cost of doing so can be as close as up to 2/3rds of the cost of an Ohlins 46DR.

And then if you havent got a suspension dyno and database that includes the force curves for a Hornet specific 46DR how then are you going to magically get the valving right first time?

[Robert Taylor]

The one called the Ohlins Streetline model number HO322 which is still a $(4 digit number)

Tho Robert Tayor has on his shelf a returned up-spec one,
(Ohlins HO 201 type 46HRCS with remote reservoir and preload)
which the price could possibly be negoiated .... tho still end up being a $(4 digit number)

Yes that is correct and it would assist the customer it belongs to if you were able to deal direct with him. He wants to get into another shock and if I desist from ''clipping the ticket'' on the way through you could get into this higher spec shock at a very good price. It minmises his loss, you get a better price and I get to sell another shock, everyone wins.

[Robert Taylor]

You're so limited by Honda's cost saving, non linkage budget rear end. It sucks!

You are gonna be exceptionally lucky to get one for $(less than four digit number).

You could probably, chuck a stumpy pipe underneath, and replace the swing arm with something decent with a shock for teh same money. Not Ohlins of course, but probably just as good as a direct action Ohlins can work anyway.

The cost and dramas associated with grafting in another swingarm and linkage from another bike are nowhere as simplistic and low cost as you make out. Notwithstanding also that many oem shocks have pistons with such restrictive port sizes they just wont absorb nasty bumps, and no amount of revalving will correct such deficiency.

The correct Ohlins listing for that model with pre setup specific to the rider , loading and road conditions will far and away provide the very best overall value for money, and very very minimal hassle.

[Robert Taylor]

Now, I'm no expert. But there's very good reasons to avoid the extra complexity and mass of linkages. With direct coupled shocks there's not only fewer moving parts but there's fewer highly loaded and poorly sealed needle rollers to wear out and sieze and generally completely fuck up the relationship between the shock and rear wheel.

'Course to get the same rising-rate effect from a direct coupled item makes for a higher spec'd, more precisely controled shock valveing system. Like most KTMs. Which possibly partly explains why they're a few Kg lighter than the competition, eh? And certsainly explains why they don't have reliablility issues associated with needle rollers running in mud.

Linkage bearings only sieze up through lack of maintenance, and its not rocket science to service them. Its just that many MX riders are too lazy to do so.

Direct acting cannot provide a rising rate effect like a linkage and control cannot be done totally on the valving. You have to have a secondary piston ( and / or needle ) that provides a stepped increase in damping force at a late position in travel.

KTM are now largely moving away from PDS ( and its many compromises ) in favour of linkage style systems. Why? Because they are superior. Just look at all their current MX models and emerging new Enduro models.

Id also challenge the weight thing. Sure you dont have the weight of the linkage set. But a direct acting PDS style shock needs a much heavier rate spring which in itself adds to the weight of the shock enormously. Also the extra internal piston and bits and pieces inside the shock exacerbates that issue even further. If you get the opportunity pick up a PDS MX shock and then a shock for a similiar capacity model that has a linkage. You will be shocked! Id say that the weight difference overall would be very minute.

[Robert Taylor]

All that is probably good on the dirt. Show me a performance bike that runs direct. Not that the Hornet matches that description, but the rear shock is SOOOOOOO bad that an upgrade is nearly a safety requirement.

On a road bike, the rising rate is more important. As is keeping the shock cooler.

NO! NO! NO! On an MX bike the rising rate is very important, given that they do jumps. Heat control is also massively moreso an issue in MX. We largely only have rising rate on road bikes to give some modicum of acceptable ride height control for well fed riders and those who carry passengers. This so they dont run off to the manufacturer complaining that they sold them an undersprung bike.

Direct acting can be made to work very well on road bikes. A true racing linkage only has a bout a 5% progression and on the current ZX6 there is no progression at all, to speak of.

( Hey can I have some of the stuff that you are smoking? )

[Robert Taylor]

Well, it lives on a farm, sorta. And I guess you could call it's owner somewhat agricultural...

But it's a better machine than it's rider knows how to manage. Actually I've rarely had cause to wrinkle the seat from rear suspension performance. The front occasionally worries me.



The real advantage with a linkage setup is that you can get faster shaft movement as you load it up. That means the spring rate AND the compression valving is ramping up faster as you bottom out. That's very hard to organise with a direct couple.

I worry about shit like: If shocks were under tension, rather than compression they could be a shitload smaller and lighter.

No, the spring rate requirement and the valving to control it all will remain essentially very similar. The Buell ''stretch shocks'' are a living case in point. And they are a costly mongrel of a thing to rebuild.

[Robert Taylor]

Yeah, and like I said you can get that wihout a linkage, the rate change just isn't quite as much and the curve isn't quite as suitable.



What I meant was, imagine if the shock had a tension spring around it that pulled it shorter. Stick it under the swingarm and mount it from the bottom of the crankcase. It's probably been done, most things have.

The reason shocks weigh what they do is they've got to take load without buckling. Things under tension don't buckle, and the tensle strength of the shaft, say, would be managed by an 8mm shaft. The mass could be less than a quarter of a standard unit.

If Suzuki coppied the rotary damper from a Morris Minor I can see how that might have been a mistake. There's a bunch of existing hydraulic actuators of different shapes and that could be used the other way around, as dampers. At least the general design could. A linear compression shock isn't nescessarily the best, but they are simple, and fairly cheap to make.

But an 8mm shaft in such a single tube diplacement style shock would displace so little fluid it would be nigh impossible to get enough initial ''knee'' of low speed compression force. Shafts are made of such large diameter PRIMARILY to get decent displacement of fluid at small and low speed shaft movements. Without that decent amount of fluid displacement ( and this is before the piston shim stacks start to move ) there would be way too little damping force buildup to give decent initial ride height position control. Many shafts in terms of minimal strength could in fact be 10mm but a 16mm / 5/8 inch shaft will for the same given distance of movement move a lot more fluid.

Sure its easy to build a shock cheaply. Just rely moreso on a heavily preloaded spring to give a crude form of ride height control without having to spend an enormous amount of development and road test time perfecting a sophisticated piston and valving stack. And once you know the spring force involved its easy to configure a low cost ''velocity squared'' type rebound curve. Use low cost materials and production techniques, low cost fluids etc. Acceptable performance at best but nothing stunning and you will still feel those abrupt bumps.
Low cost shock options are a dime a dozen but also higher cost premium quality shock manufacturers exist where you want a shock that actually does absorb bumps, gives ride height control and is reliable

But if you use higher spec materials, temperature compensation techniques, low friction materials and very precise tolerances, higher quality fluid and a LOT of time developing a bespoke piston and valving combination THAT ACTUALLY WORKS VERY WELL then the cost does ramp up. Also what a lot of people forget is that the most committed and forward thinking suspension manufacturers will allow a small percentage to fund ongoing R@D. We all crave new developments and that has to be funded from somewhere.

Coilover spring and damper combinations remain the best overall design and in terms of packaging they are light years ahead of other fanciful designs that ( cynically ) have been more of a marketing exercise on too many occassions

[Ocean1]

Linkage bearings only sieze up through lack of maintenance, and its not rocket science to service them. Its just that many MX riders are too lazy to do so.

I did say I wasn't an expert Robert.

But I'd still suggest that manufacturers are taking a design easy path with those linkage bearings. Perhaps maintenance periods like that are OK for competition machines, but most dirt bikes use the same general arangement and it's simply not reasonable to expect a trail bike to be completely striped and cleaned that regularly, hence the grease nipples retro-fitted to many.

Speaking of which I see Ossa tried teflon DU bushes, (for wheel bearings as well!) which required almost a per-ride strip, clean and lube schedule. They've released an "upgrade" kit.

Direct acting cannot provide a rising rate effect like a linkage and control cannot be done totally on the valving. You have to have a secondary piston ( and / or needle ) that provides a stepped increase in damping force at a late position in travel.

A geometry that starts with the shock at, say 45 deg to the swingarm and ends with it at 90 deg represents a rising rate does it not? And there are hydraulic control mechanisms that vary a cylinder's velocity steplessly throughout it's stroke. I've just never seen them on a motorcycle.

KTM are now largely moving away from PDS ( and its many compromises ) in favour of linkage style systems. Why? Because they are superior.

Yes, I know. And yet they've built best-of-breed dirt bikes with PDS systems against "superior" opposition for how long? I wonder how much of their changes are simply a matter of maintaining a marketable price. Or at least changing to a configuration that makes the most of a limited suspension build for production machines in their current marketplace.

[Robert Taylor]

I did say I wasn't an expert Robert.

But I'd still suggest that manufacturers are taking a design easy path with those linkage bearings. Perhaps maintenance periods like that are OK for competition machines, but most dirt bikes use the same general arangement and it's simply not reasonable to expect a trail bike to be completely striped and cleaned that regularly, hence the grease nipples retro-fitted to many.

Speaking of which I see Ossa tried teflon DU bushes, (for wheel bearings as well!) which required almost a per-ride strip, clean and lube schedule. They've released an "upgrade" kit.



A geometry that starts with the shock at, say 45 deg to the swingarm and ends with it at 90 deg represents a rising rate does it not? And there are hydraulic control mechanisms that vary a cylinder's velocity steplessly throughout it's stroke. I've just never seen them on a motorcycle.



Yes, I know. And yet they've built best-of-breed dirt bikes with PDS systems against "superior" opposition for how long? I wonder how much of their changes are simply a matter of maintaining a marketable price. Or at least changing to a configuration that makes the most of a limited suspension build for production machines in their current marketplace.

No worries, my explanations were offered as clarifications, eg the shaft size thing. Note that I took the trouble to explain at length and only directly took the mickey out of Drew who has got to be smoking some stuff that Id like!

Yes you will get a moderate rising rate effect with such inclination, but for dirtbikes not without futher aids such as positional internal bottom out cups and pistons. This we see in the Ohlins aftermarket PDS shocks for KTM, and believe me they are way better than the WP shocks.

With PDS I disagree that it has merits that overall make it better than linkage bikes. Its not that PDS IS ''bad'' per-se. They are just not better and if they were everyone would be doing it.

[Ocean1]

Note that I took the trouble to explain at length and only directly took the mickey out of Drew who has got to be smoking some stuff that Id like!

Meh, bastard won't give me any either.

With PDS I disagree that it has merits that overall make it better than linkage bikes. Its not that PDS IS ''bad'' per-se. They are just not better and if they were everyone would be doing it.

What I was trying to get at was that if you had perfect velocity and positional control on your shock then the linkage is redundant. And there are industrial control systems out there that, while not perfect are bloody close.

Anyway. Why aren't you telling ma about cost effective improvements for Buell's XB12X Showa forks?

[Robert Taylor]

Meh, bastard won't give me any either.



What I was trying to get at was that if you had perfect velocity and positional control on your shock then the linkage is redundant. And there are industrial control systems out there that, while not perfect are bloody close.

Anyway. Why aren't you telling ma about cost effective improvements for Buell's XB12X Showa forks?

Applying such control systems is not neccessarily straightforward, it can be a can of worms

Ill have to do some research on those forks, give me a little time, Ive been away for a month and have lots to catch up with. Perhaps send me a prompt

BTW, I love the Ineptocracy statement, sad but true. There are those that vote for a living and those that work for a living................

[Warr]

...... if you were able to deal direct with him. He wants to get into another shock and if I desist from ''clipping the ticket'' on the way through you could get into this higher spec shock at a very good price. It minmises his loss, you get a better price and I get to sell another shock, everyone wins.

Yep ... I'll take the hint