Forum search & shortcuts

Linkage fork curiou...
 

[Closed] Linkage fork curious

Posts: 35201
Full Member
 

Would you like a fork that has a lower spring rate so improved small bump sensitivity but that still does not collapse under braking or big hits?

Don't care about small bump sensitivity. These are just words from a marketing blurb. I can do that with tyre pressure

Less stiction so again better small bump compliance?

see above

Less flex for the same weight or less weight for the same flex?

Like a bit of flex thanks, not bothered about the weight of forks since ohh I don't know when...

<span style="font-size: 0.8rem;">simpler damping circuits that give more sensitivity and adjustment?</span>

I don't care about the internals, they can be simple or complex, I can adjust my forks as much as I need currently linkage forks are not inherently better at this

<span style="font-size: 0.8rem;">To be able to work with a low spring rate even under hard braking? No more chatter over braking bumps just a wheel that tracks the ground and allows you to brake hard over rough ground?</span>

To be clear, I use coil Ohlins, it tracks just fine, and smooths out chatter well enough, don't brake over rough ground, your tyre needs to grip and turn, either brake before or brake after

All these and many other advantages are possible It doesn’t even need to have a lot more pivots – the telever type design has two extra simple pivots that are not highly stressed

"many other advantages" again, you sound like marketing, will it make me more attractive to women?

Like I said, Linkage forks need to be substantially better in performance, packaging, price, servicing for me to consider one. I've ridden two, quite far apart in terms in years (I bet that's more MTB linkage forks than most folk) both were/are massively inferior to their tele counterparts in some major ways. Like the way we change gears, suspension on a mainstream MTB is settled. I would rather these are refined to be as best they can be than throw the baby out with the bathwater and start all over again because some amateur engineers on t'internet perceive them as slightly inferior to their pet brain-fart

Perfect is the enemy of good (Voltaire, probably)


 
Posted : 03/04/2019 8:50 am
Posts: 91173
Free Member
 

stuff that you see in off-road racing that can produce higher damping forces at the end stroke

Pretty sure my old 66s did this? RC2X it was called. Or do you mean something more complex?

Don’t care about small bump sensitivity. These are just words from a marketing blurb. I can do that with tyre pressure

Not without introducing other compromises you can't. But this is a matter of taste. Small bump plushness does make a fork feel nicer when riding around but makes little difference on really rough stuff where it counts. But then again, low friction does make a difference, which also affects small bump sensitivity so the two are linked.


 
Posted : 03/04/2019 9:08 am
Posts: 0
Free Member
 

Despite generally being butt ugly, I've always been open to linkage forks due to the potential to tune in additional suspension characteristics such as anti dive.

That was until this morning when I did a bit of head scratching and pondered whether anti-dive is actually a good thing...

When you think about it, the fork diving will weight the front end, increasing traction and steepening the head angle, aiding turn in and agility.

So perhaps anti-dive isn't all it's hyped up to be, except in instances where the rider ain't so hot at timing their braking.

That said, whilst I'm not sure I want my bike looking like a praying mantis, I'm still open to alternative approaches; can't help but think this would produce a far stiffer fork, which in turn would be smoother due to reduced bushing bind; as a bonus, it's pretty darn sexy too

https://www.pinkbike.com/news/the-real-story-of-that-single-sided-carbon-fork.html


 
Posted : 03/04/2019 11:08 am
Posts: 0
Free Member
 

I think the main advantage of a linkage fork is avoiding bushing bind. But I suspect a better solution may be a different approach to MTB fork bushings!

Yes.

But also fun to see some new tech stuff around.
Maybe a market niche for XC racer and similar?
Not really an solution for long travel all mountain bikes, enduro bikes and downhill?


 
Posted : 04/04/2019 10:11 am
Posts: 91173
Free Member
 

That was until this morning when I did a bit of head scratching and pondered whether anti-dive is actually a good thing…

This is the real question. No-dive forks have been around for a long time and never taken off.

If you are going down something steep and are already going slowly with your weight back, a really slack HA helps. But if you were to brake into a corner and the fork didn't dive, you'd have to go round that corner still with the super slack HA. So that might be a lot harder. You might find it harder to get round some sharp hairpin if you couldn't lean over the front and make it shorter.

It might be that we've arrived at a solution to multiple problems purely by accident, in the form of telescopic forks.


 
Posted : 04/04/2019 10:19 am
Posts: 2559
Free Member
 

Yup – that is one of the major advantages chief along with being able to tailor axle paths and leverage ratios to give rising rates and travel dependent damping using simple dampers. MUch cheaper and simpler than complex dampers. You don’t see rally cars with sliding pillar suspension do you which is the car equivalent of tele forks – the system used in Morgans

Yes but Morgans have a "steel is real" chassis that breathes with the trail, so its OK.


 
Posted : 04/04/2019 10:24 am
Posts: 2559
Free Member
 

Also, most cars have McPherson strut front suspension, which does rely on a sliding pillar to take some loads (but not the big ones). Which some bike forks do.


 
Posted : 04/04/2019 10:40 am
Posts: 0
Free Member
 

You don’t see rally cars with sliding pillar suspension do you which is the car equivalent of tele forks

As greyspoke says, McPherson struts are used in rally cars, so the damper takes some of the lateral and longitudinal loads.


 
Posted : 04/04/2019 10:51 am
Posts: 0
Free Member
 

As greyspoke says, McPherson struts are used in rally cars, so the damper takes some of the lateral and longitudinal loads.

Yup.

Pretty sure my old 66s did this? RC2X it was called. Or do you mean something more complex?

They did this by altering the oil volume in an open bath damper. Position sensitive damping in closed systems can be introduced in a number of different ways and the precise position that it kicks in can be controlled. EXT have an hydraulic bottom out that kicks in by using an extra sheath inside which the damper piston enters towards the end of it's travel that diverts the oil flow. Vorsprung are doing position sensitive damping by adding another open bath damper to the spring side that only kicks in during the last 50mm of travel. External and internal byspass shocks take this one step further and have multiple bypass holes along the length that the shock stroke, allowing oil to be diverted at different rates and at different points in the shock stroke.

A big advantage of using teles, is that they allow for more effective damping as they are using a linear leverage ratio. Rear dampers are starting to go in the right direction by getting longer, allowing more of the bump absorption to be done by the damper - but the longer they get the harder they are going to be to package in a linkage fork.

From what I gather, high leverage ratios develop higher shaft speeds quicker and can feel spiker - where as lower leverage ratios can offer better control at the expensive of a little bit of initial friction. Needless to say, in the motorsports world - offroad vehicles tend to use pretty low leverage ratios and huge dampers.


 
Posted : 06/04/2019 3:32 pm
Posts: 7001
Full Member
 

Is anyone linkage curious enough to go all in. If I lived nearby (I know, excuses excuses) I would be right in there:

https://www.ebay.co.uk/itm/BMW-chrome-Mountain-bike-full-suspension/123719819034?epid=944178544&hash=item1cce469f1a:g:8q8AAOSw-6Bco7H6


 
Posted : 06/04/2019 7:06 pm
Posts: 0
Free Member
 

For clarity, when I said that teles have linear leverage ratios - I meant 1:1 leverage ratios.


 
Posted : 06/04/2019 8:17 pm
Posts: 0
Free Member
 

One supposed story is that the wide spread use of telescopic forks was due to the large number of barrel making machines/borers after the war, giving the motorcylce mnufturers a cheap supple of tubes. BSA for even mnufturered arms in house.


 
Posted : 07/04/2019 1:08 pm
Posts: 44845
Full Member
 

correct simon - more that they now had the technology to make long straight strong tubes with preciusion bores


 
Posted : 07/04/2019 1:18 pm
Posts: 2559
Free Member
 

Is anyone linkage curious enough to go all in. If I lived nearby (I know, excuses excuses) I would be right in there:

https://www.ebay.co.uk/itm/BMW-chrome-Mountain-bike-full-suspension/123719819034?epid=944178544&hash=item1cce469f1a:g:8q8AAOSw-6Bco7H6/blockquote >

There you are, an mtb fork that uses a sliding pillar for some loads, but a linkage takes the big for-and-aft ones.


 
Posted : 07/04/2019 1:31 pm
Page 2 / 2