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Single pivot vs. Dual pivot

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Single pivot vs. Dual pivot
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flag orange5
Posted: Jul 17, 2008 at 5:49 Quote
Whilst in theory a genuine 4 bar, or linkage driven bike will have different characteristicts to a single pivot, in practice the difference in the path of the rear axle is tiny. The main thing that linkages do is allow designers to decide the leverage on the shock. This can be done on a simple single pivot like an Orange by placement of the shock mounts. The way a bike handles has alot more to do with geometry etc.
The thing that hadrly any designs get around is that every time you change gear at the front the chain line is in a different place relative to the pivot. And you hardly notice any change in the performance - so no wonder the difference in the shape of axle paths make little difference. It's kind of proved by the fact that Turners used to be Horst link, now they're faux bar (so effectively single pivot) and the ride is almost identical, according to magazine tests. It's just a quality make, by someone who understands geometry & how to put a frame together.
The ideal design if it could be light enough is like the Brooklyn Machine Works, or the gearbox bikes, where there's a high pivot that pedals as it should because the chainline runs along the swingarm. And because of the high pivot, the suspension works most efficiently (like on a motocross bike). Where high pivots are a pain is on a normal design, as it causes kickback & locks out the suspension when you pedal hard.

Anyway, in practice, don't buy a bike based on theory or what a magazine says, ride a few & buy the one that works best for you.

Do people actually find this interesting...? Just wondering if it's just me.

chasing trails
flag ctd07
Posted: Jul 17, 2008 at 6:18 Quote
There seems to be some confusion about what exactly a single pivot is, but just think about it literally for a moment:

Single Pivot (wheel path pivots around one fixed center) = Where the axle of the wheel pivots around only one axis (pivot point) e.g. Kona, Orange, Cannondale judge. The extra linkages on the Cannondales and Konas are there to support the main pivot thus adding stiffness and also to manipulate the shock rate throughout its travel, however, a shock rate can still be manipulated on a simple single-pivot system (i.e. Orange) by altering shock mounting placements, pivot placement e.t.c. - virtually any ratio curve can be achieved, but pedal induced feedback into the suspension system cannot be eliminated, just catered for by adjusting shock rates throughout the wheels travel and pivot positions.
The simple single-pivot system provides the most natural movement for bump absorption as the wheel isn't fighting against any linkages in order to move (think: Iron Horse DW link - very unnatural linkage movement!).

Virtual Pivot (Multiple linkages create a 'virtually' pivoted wheel path by constantly altering the central pivot point of the wheel throughout its travel, e.g. Santa Cruz, Intense M6, Yeti 303dh e.t.c.) = This system gives more leeway over how the shock rate curve and the wheel axles path through its travel can be altered (it is more natural for a wheel for it to move rearwards under impact, as a bike tends to travels forwards), this system can be designed to better separate pedal and braking induced feedback and can combine a 'virtual' ['pivot-free'] wheel path along with altering shock rates in order to give a more propiatory shock rate curve. Due to the inherent complexity of this design, there may be 'anomalous' unwanted characteristics from the suspension.

ICT (Ellsworth)/FSR (Specialized) (Multiple pivots used to slightly alter a single pivot wheel path) = These systems also use multiple pivots to alter wheel path and shock ratios in a similar way to virtual pivot designs, but the wheel's axle is still connected to one pivot point (generally on the chainstay), these systems create a constantly moving pivot point for the rear wheel throughout its travel, using linkages to guide the wheel path and generate the desired shock rate curve. This system can be designed to achieve a measure of separation of pedal and braking induced feedback.

Disclaimer: These explanations are based on my own understanding and research of the aforementioned designs. I have a keen interest in suspension design as well as a background in engineering. I am happy to be proved wrong/refuted on anything I have written, but please do not do so without backing up your statements or at least trying to state some form of fact, as it isn't helpful!
flag wowxl00k1tsgr33n
Posted: Jul 17, 2008 at 7:50 Quote
Hummeroid wrote:
wowxl00k1tsgr33n wrote:
dual pivots uasually getalot better traction than single pivots less rotation pionts equal faster rebound while more equal slower rebound i have a big hit wich is a single pivot and no matter how low a turn the spring or how much i turn the rebound to slow i will still "Drift" every now and then wich meens my back is way to stiff dual pivot is better for racing while becuase you get more traction but if u wana have alot of fun youed want a single becuase its easier to slide and i personaly like stiffer duallies anyway.

first off, NO, did you read the thread? Big hits are a horst link, not a single pivot.

Second, WHY did you bring this back up?!?!

Ok buddy a horste link is a single pivot how many pivot pionts do you think a big hit has? And wtf f*ck are you talking about the question of this thread is single pivot vs. dual pivot. QFT^^^
flag woohill
O+
Posted: Jul 17, 2008 at 8:28 Quote
wowxl00k1tsgr33n wrote:
Hummeroid wrote:
wowxl00k1tsgr33n wrote:
dual pivots uasually getalot better traction than single pivots less rotation pionts equal faster rebound while more equal slower rebound i have a big hit wich is a single pivot and no matter how low a turn the spring or how much i turn the rebound to slow i will still "Drift" every now and then wich meens my back is way to stiff dual pivot is better for racing while becuase you get more traction but if u wana have alot of fun youed want a single becuase its easier to slide and i personaly like stiffer duallies anyway.

first off, NO, did you read the thread? Big hits are a horst link, not a single pivot.

Second, WHY did you bring this back up?!?!

Ok buddy a horste link is a single pivot how many pivot pionts do you think a big hit has? And wtf f*ck are you talking about the question of this thread is single pivot vs. dual pivot. QFT^^^
we already went over this. a horst link isnt single pivot. the only bighit that is single pivot it the bighit grom or whatever its called.
flag wowxl00k1tsgr33n
Posted: Jul 17, 2008 at 13:01 Quote
stinkyde wrote:
wowxl00k1tsgr33n wrote:
Hummeroid wrote:


first off, NO, did you read the thread? Big hits are a horst link, not a single pivot.

Second, WHY did you bring this back up?!?!

Ok buddy a horste link is a single pivot how many pivot pionts do you think a big hit has? And wtf f*ck are you talking about the question of this thread is single
pivot vs. dual pivot. QFT^^^
we already went over this. a horst link isnt
single pivot. the only bighit that is single pivot it the bighit grom or whatever its called.

Ok you tell me how many pivot points the rear end of a bighit not grom rotate around it may not be called a "single pivot" but it is.
flag Hummeroid
Posted: Jul 17, 2008 at 13:07 Quote
pooforbrains wrote:

Ok you tell me how many pivot points the rear end of a bighit not grom rotate around it may not be called a "single pivot" but it is.

You my friend have totally missed the last 4 pages of stuff. It DOES have a secondary pivot point, and guess what it allows? Braking forces to be driven into the frame instead of the suspension. Just because your chainstay pivot is covered in grease and mud doesnt mean its not there.

Do I need to get out the e-chalkboard and school you a bit, or are you going to believe the rest of the world?
flag xltrider
Posted: Jul 17, 2008 at 20:22 Quote
wowxl00k1tsgr33n wrote:
Ok you tell me how many pivot points the rear end of a bighit not grom rotate around it may not be called a "single pivot" but it is.

the big hit doesn't really rotate [u]around[/u]any one pivot. because it's a horst link. it has a different axle path than a single pivot would. the rear wheel of a Big Hit with a horst link does not rotate around one fixed pivot. therefore, it is [u]not[/u] a single pivot bike
flag nathan-babichuk
O+
Posted: Jul 18, 2008 at 9:08 Quote
I love my 2008 bullit. I have my shock set up perfect for my weight so the pedal bob is'nt terrible and Im ordering a floating brake to eliminate brake jack.
flag guerilladownhilla
O+
Posted: Jul 18, 2008 at 9:29 Quote
heres a fun little test: take the shock out of your big hit and measure how much the chain stay length grows as you cycle the suspension through its travel. now try it with a kona....

some of you kids reeeaaly need to pay more attention in geometry...
flag orange5
Posted: Jul 22, 2008 at 12:39 Quote
Yep, single pivot's will mean more chain growth - can't say I've ever noticed any brake jack with a single pivot though - I know it's there in theory, but in actual riding I don't notice any.

Just looked at a pic of a Bighit grom & as the above post correctly implies it is not a single pivot - it has one to join the chainstay to the seat tube area and another infront of the axle, not above it. This is what makes a bike a horst link, for the person who doesn't believe...

Also just looked at the pics of wowxl00k1tsgr33n's Bighit and it is definitely a horst link, not a single pivot. Does he mean it's not a vitual pivot? Which it isn't...

chasing trails...
flag xltrider
Posted: Jul 22, 2008 at 12:44 Quote
if anything you learn better braking skills
flag orange5
Posted: Jul 22, 2008 at 12:49 Quote
Yeh I agree about the braking skills - I reckon if you brake correctly it removes the need for systems that 'correct' brake jack. However, as has been said, Horst links have other effects as well.

It can't be too much of a problem when Orange, a small UK company & makers of single pivot bikes have been one of the most succesfull DH teams around
flag dg85
Posted: Jul 22, 2008 at 22:45 Quote
my session 77 is single pivot isnt it? im not 100% so if not please correct me.
but i do notice brake jack when braking in dry hard pack conditions (domnt get much of that in uk) but pedal bob is no worse than any other dh/fr ive tried. its a much better pedal platform than a v10.

also what about the session 88. is that single pivot still because it has the floating suspension im not sure if it is?
flag xltrider
Posted: Jul 22, 2008 at 23:41 Quote
yeah i'm pretty sure it is. me, i've only ridden hardtails and single pivots so i have no idea what no brakejack feels like. i don't really care, really. i'm more worried about how the shock performs, especially it's mid-stroke support (after having a float r on my last bike. it sucked)
flag leon-forfar
FL
Posted: Jul 22, 2008 at 23:55 Quote
badluckbiker wrote:
dg85 wrote:
god i love hardtails lol

Haha! Y'know, I'm beginning to think the same thing.
In the old forum there was a guide to all (and I mean ALL) the suspension designs out there, I'm looking for it now, I thought it was a sticky.
I'll post it here when I find it.


to me if it has a backshok that goes down and comes up, its good enough. i love stinky's, cuz of the feel not the linkage. i dont care about linkage as long as it has cushion. its all too complicated:P

 


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