rear pivot location, how much does it matter?
So you have the FSR/Horst/4-bar sort of schemes where the rear pivot is at the end of the chain stay and just below the axle. You have the Low single pivot/Foux-bar whatever you want to call it that has the pivot in the seat stay just above the axle. Then there is Trek's ABP where the pivot is actually around the axle. Does any of this really matter or is it all a legal thing about who patents what and they are all really trying to accomplish the same thing? All three of these suspension types have the pivot within a couple inches of the same location!
Anyone ridden these different systems and notice any difference? Is there any way to even know if its the suspension type or the shock/geometry/tires ect that is making the difference?
It does matter.
On faux bar systems, the rear end acts essentially as a single pivot. The downside to this is that the system is prone to brake jack. The torque acting on the brake caliper causes the suspension to compress, which means that on downhills when you're using your rear brake your suspension isn't performing well becausee it's compresses farther than it should be.
Horst link and split pivot/abp designs seek to eliminate brake jack. Because the brake is on the second link, braking forces are not transmitted through the first link causing the suspension to compress.
See this article for a good explanation of rear suspension types:
Buyer's Guide To Mountain Bike Suspension, Part 1 - BikeRadar
Buyer's Guide To Mountain Bike Suspension, Part 2 - BikeRadar
And my favorite tagline: Trust me, I'm an engineer
axle/wheel path changes with Horst link position
Pivot position determines the axle path, which determines how the bike reacts to pedalling, acceleration and braking loads.
Pivot position is the most important part of the suspension design.
Have a read through the website in my signature. The website is dated (a lot of it was written 1998-2000), but the content is still 100% relevant.
Just go ride a Kona then a Specialized you will feel a noticable difference in pedaling efficiency.
I beleive Norco and Rocky Mountain pay to use the Horst link on their frames?
I actually plan on doing just that, I have been researching Specialized, Kona, Santa Cruz and Giant looking at a new bike potentially some time next year, but I still need to get out and ride them.
Originally Posted by canuck_tacoma
Giants are nice...Maestro pedals great and still descends well.
Isolating the brake from the chain stay makes it possible to reduce brake jack IF the new brake location doesn't also rotate with the wheel as the suspension compresses. Just putting a bearing there assures nothing. What happens upstream at the other end of the seat stay is what determines the success of the system.
Good Horst systems have an upper link that rotates upward such that both ends of the stay move upward rather than rotate. Plus the brake's torque on the stay pushes the suspension link opposite to the jack and it's possible to come close enough to zero feedback.
After years of scratching down hills on a single pivot I sure find it nice to hit the back brake on an FSR and nothing 'puckers up'. This makes modulation easier and the suspension doesn't bounce up and down as the wheel finds and loses traction.
Maestro style suspension has the rear triangle moving up and down rather than rotating so jack is covered. It does rotate slightly but the leverage ratio is so high that nobody ever noticed it. While it looks really different from a Horst it is just another way of doing it with the 'rear' pivot at the front and the the stays braced together.
ABP probably cuts jack in half; I've never done any ratios so it's just a guess. I never quite got what the excitement was about a concentric pivot, although there are those who extol its magic properties. It depends upon what you rode before. And certainly a big move forward for Trek. But Cannondale still uses a single pivot with the brake on the chain stay so go figger.
The general answer to the OP's question is yes it matters. How much it matters depends more on a rider's sense of balance with the bike.
Riding many bikes even with the same basic suspension design, and trying various suspension designs is the only way to find what works better for each rider.
For academic details of suspension dynamics, use your favorite search tool to research "anti-squat" as it relates to acceleration, and "anti-dive" as it relates to braking. The placement of suspension pivots are only completely explained in context with these terms. Both front and rear suspension are affected by rates of anti-squat and anti-dive.
Read what the Spanish author Tony Foale diagrams and analyzes about anti-squat and anti-dive. He explains most completely for bikes (motorcycles) the geometry dynamics of suspension leverage pivots including chainline. The same dynamic balances of squat and anti-squat, and dive and anti-dive effects of motorcycles apply to bicycles. Bicycles have a much higher center of gravity and shorter wheelbase, and much slower and pulsing "twin engine" compared to motorcycles, so the balancing of inertia and power input forces of a bicycle is more difficult than a motorcycle.
Multi-link suspension designs have more dynamic geometry possibilities as the wheel path travels to counter the instability and inefficiencies of squat and dive without sacrificing good bump compliance and traction compared to telescopic or monopivot suspensions. However, notice that all modern off road motorcycles use monopivot and telescopic suspension after race testing many variations of multi-link designs in prior decades. It is rare to significantly improve upon the ability to well balance telescopic and monopivot bike suspension when adding into dynamics the rates of springs and damping.
Very high rate anti-squat and anti-dive is more stable, reducing and nearly eliminating energy sapping acceleration squat and pedaling bob, or the over-the-bars feeling of massive braking dive. But the suspension firming reaction to high rates reduces the modulation feel of traction limits and reduces bump compliance.
Low rates of anti-squat and anti-dive are slower reacting to pedal or brake forces, and less stable and softer in maintaining rider balance and angle over the wheels and pedals, but bump compliance is greater and traction is easier to modulate when applying pedal or brake power.
The trick suspension designers work towards is having firm and energy efficient pedaling reaction near weighted suspension sag, and softer compliant suspension when hitting bumps and high traction without very much dive when applying the brakes.
I searched for literature on suspension sytems and found a good article that a couple of engineers researched. Can't remember the title or the authors off the top of my head. They had some very good diagrams and explanations. There bottom line recommendation was to try different systems out and see what feels good for you. There is a lot of hype and marketing out there , before you know it you are just repeating things you've read. I've owned the early GT idrive, intense VPP and now have the trek ABP with DRCV shock and can feel noticeable differences. So demo different systems, and see what feels good for you. Reminds of stereo speakers, the best speakers are what sound good to you, without reading the spec sheet.
I don't know much about suspension linkages, but I can say that I've ridden FSR's, whatever Kona and Transition uses, and have to say that Knolly's 4x4 feel's the best going down, and near perfect going up. I'd put Treks ABP in second.
+1 on Giants Mastro being good AM setup. Very impressed with my Trance X. I had a high single pivot like a Heckler and it would actually jack a bit with small ring. There are a lot of linkage bikes out there, you should be able to find one you like.
Originally Posted by derby
Thoughts on the following...
Let me preface this by saying I've never had a longer travel (5 or more inches) quad link (VPP, CVA, DW...) bike.
Is it all in my head or do non-quad link bikes seem more "maneuverable"? By this I mean, do the "pro-squat-like" properties of faux and 4 bar (keep high SP designs out of this whole discussion) designs alow one to sink the back end of the bike more easily with a touch of power to the pedal. This in turn allow one to un-weight the front end more easily, and thus negotiate drops, sharp front hits, ledges, etc.. better? Or, is this feeling more dependent on longer travel, rather than suspension design?
While the issue I mention above might seem like minutia, in reality it is something I've always found very important where I've traditionally ridden - rocky, tight, slower speed NE type trails.
I also find that less damped, non-quad link designs seem a bit more plush in general, especially on the downhill and when pedaling through the rough.
I'm finding I like a faux or 4-bar for most trail riding. Seems pretty nice to have a super supple suspension when needed, then throw on the PP for the climbs - this not only gives some pedaling platform but also keep the suspension higher in its travel and makes for better climbing geo.
Admittedly, for xc type riding where l'm hammering out of the saddle the quad link designs are very nice.
Part of the reason I'm toiling over this is I've been interested in a Ventana with some custom geo for many years, but with all the fan fare over newer suspension designs I've been kept in a state of second guessing. Since the bike I'd be getting is more trail-AM, seems like the faux might still be good to go.
Yes. The pedal squat of lower monopivot, and low anti-squat HL's like FSR and ITC, do shift weight easily back to manual easier (lift the front wheel). These designs usually have a steep 74 to 75 degree seat tube angle to be able to climb well.
Originally Posted by Miker J
A high anti-squat design doesn't squat from pedaling or while climbing, some lift the rear slightly while climbing in the granny, so the seat tube can be 2 or 3 degrees slacker, at about 71 to 72 degrees, than a low to moderate anti-squat rate monopivot/FSR/ITC type design, without loss of climbing weight center balance. The more rearward seat position, further back over the rear wheel, of a high anti-squat rate design lowers the rider weight, and allows easy manualing with or without the aid of a pedal stroke, and enables more nimble seated turning.
And yes, I do sense that the DWL in particular does get hung up a little when coasting downhill on rocks, and when pedaling up very rough compared to low anti-squat designs.
The coasting hangup I think is the wheel path transitions more forward during compression than a monopivot/FSR, so the rear wheel must accelerate more in comparison during compression and the coasting rear wheel's inertia has a mild braking effect when hitting rocks. Unlike a high anti-squat monopivot high pivot design (sorry, wasn't supposed to mention in this discussion!) there's no DWL kickback feel at all of the backpedal resistance when pedaling in the rough and rocky.
I've adapted to this sharp bump hang up feeling with my DWL bikes by going to a softer rear spring than I would use with a monopivot or FSR, easing rock hit compliance with no loss in pedaling efficiency, and add a click of compression damping for rides on all firm smooth hard pack (very rare occurrences!). I never feel a desire for propedal with DWL, except for standing slow pedaling.
Miker j, you really need to go out and demo some bikes on real trails and feel the best one to you like.
I thought that the HL was not supposed to do anything for pedaling efficiency. It is only for braking forces. No? With that said, overall pivot placement can effect pedaling efficiency through chain growth (aka, Norco and Lapiere).
Originally Posted by canuck_tacoma
Last edited by Vespasianus; 12-17-2012 at 07:49 AM.
Giant's Maestro is the second-best pedaling platform I've ridden. The best? BMC, which is *nearly* identical but has just a slight edge that I could feel when pedaling hard out of a corner or climbing. I've unfortunately not had both brands next to each other so that I can look closely and see the differences in the linkage and other aspects of the frames.
VPP2 bikes pedal very well, also. My old Blur classic is VPP1 and it intentionally had a falling and then rising leverage ratio in order to use a lot of the shock early in the stroke for bump compliance and then to use less to give bottoming resistance. Only problem is that made it susceptible to pedal bob, which was really noticeable on shocks without platform, but now that I have a CTD TA shock there's no issue at all.
I agree that you can feel this stuff... when you're on a real trail. You really need a demo ride or to borro a friend's bike to get the necessary seat time and terrain to assess a bike. And remember, you are assessing the whole bike-- a great shock can make a so-so suspension linkage work pretty well, and a cheap shock on a Giant will be noticeable.
The most important thing is to learn the strengths and weaknesses of the design you buy and learn how to ride it to the best of your abilities.
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I've owned high/low single pivots and four bar HL. The dual four bar by Knolly is definitely my fave. Two independent floating pivots. One for the wheel pivot, and one for the shock pivot. Great pedaling, supple top end and bottomless feel deep into the travel. Bottom line, test everything you can and see what works for you.
I saw your response quite some time ago and have been giving it some thought.
Originally Posted by derby
Interesting point on how higher anti-squat designs often run ('cause they are able to) slacker STAs. This is something I've come to prefer - a slacker STA. I find it much more comfortable. It also works well on bikes that need longer chainstays as it keeps your weight centered.
Anyway, a dedicated 275 is under consideration for 2013 and it will likely be carbon which takes Ventana out.
How is the Mojo HD working out with 275s?
Thoughts on Intense's incarnation of VPP? (Carbine 275 specifically?)
After reading yourcomment on dwl kickback when climbing in the rough,my comment earlier about test riding different systems is important. I met a guy out on a ride who loved his dwl suspension because it didn't do what you stated!?!? Maybe hehad a different brand bike,( I think he had a turner)etc. There are so many variables to consider
It's relative. And with a DWL it is very subtle. The very high rate of anti-squat of any DWL while climbing gives it a firmer pedaling platform, and steps up large sharp rocks with a little less compression compliance compared to low anti-squat monopivot or platform shock supported FSR. The advantage is the DWL accelerates forward rather than squatting and delaying acceleration from pedaling effort, so chances of making the step-ups are improved with the instant acceleration.
Originally Posted by frana
A DWL hides the feeling of kickback better than any other high anti-squat suspension I've ridden, and I've ridden dozens of suspension designs to find the best climbing and all around handling bike I can buy for my hard earned cash.
Sometimes people like to claim the fsr/horst link bikes are the "plushest" of all, even if they bob a little, but bear in mind that those usually have a very low pivot, which doesn't react well to sharp/bunt rocks. Some claim that the horst link bikes travel in a vertical path, but this is complete BS and they travel in an arc with the rear pivot anywhere close to the dropout. To try and make it better, I ran a custom-valved shock, and that helped, but nowhere near as good as the DW suspension due to it's less forward-arcing path and much less compression damping.
Originally Posted by frana
So, that may be where this guy was feeling it, traditionally the FSR bikes don't do well with the square edged hits and accelerate poor uphill, despite lots of traction, "bucking" and bouncing quite a bit in my experience. The mid to high pivot single-pivot bikes will do better here, but when you try to pedal you get more feedback and bucking again, so the DW gives a nice tradeoff with both.
"It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth
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