[HardtailHack]

Sorry guys I know you will hate this because it will end up as an E fight but.....

Why is a bike that has a forward axle path after its sag point considered to be a beter design than one that has an axle path that will move away from oncoming obstacles?
I know people consider pedalling efficiency as a major positive of VPP and similar style frames but surely a bike that keeps its wheelbase variation to a minimum throughout the full range of travel is going to be more stable on heavy landings and should also keep speed through rockgardens because of the rearward axle path. Surely this would be enough to make any high pivot frame seem like a logical design for a DH frame but they seem to be only made by the smaller brands.

I'm no expert on suspension design but surely a wheel that moves away from an oncoming object will help you carry speed compared with a design that sends your wheel against said object with a slightly forward axle path. I realise brake jack is a problem but top level racers seem to hit corners fater than ever so surely brake jack would be a minimal problem to them.

For what it's worth I like hardtails but when I started to consider DS frames, a rearward axle path seemed like the only logical choice to me.
Please tell me why I'm wrong.

 

[P.T.W]

 

[no skid marks]

IMO
High pivots will have brake squat, not jack, that's without a floater or a virtual high pivot point suspension design to elimimate squat, or a split pivot.
High pivot bikes don't feel as fast cornering as if they squat, the front geo won't steepen as the back will squat when the forks are diving under brakes, aslo the wheelbase of a high pivot won't shorten when slamming corners, so this won't make the bike more manouverable either.
A high pivot will tend to pop you out of corners better as the suspension unloads.
Also with a high pivot the bike and riders center of gravity will move forward as both wheels go backwards,this will quicken steering somewhat, but lighten the rear wheel, hence why a short rear is more desirable.
I guess most people believe there to be a lot of friction from an idler, I've never noticed it.
But for DH I myself feel a high pivots benefits of absorbing square edge impacts and having a consistent/stable wheelbase makes them a winner, and I can't determin if they corner any slower, I think it may be a placebo.
I think a lot of designers may be worried of gambling with anti squat, pivot height etc over a tried and true low pivot or vertical axle path VPP.
A lot of big brands have experimented with high pivots, trek, GT, Mongoose, to name a few.
Some people like suspension not to really work(skip over stuff)accept for on big hits, so they'd favour low single pivots or similer wheel path VPPs.
I think wheelpaths are slowly getting more rearward on average.
Or simply because it looks cooler and is more marketable this season
I'm tired, and will ad more or edit this in the morning(Ozy).

 

[eatmyshorts]

well if you read Santa Cruz speal in what was Joes corner.. VPP was originally used to create a rearward wheel path. Later it was thought it made minimal difference and the VPP is now only used to manipulate the shock rate and not wheel path..

Do any other forms of wheeled motor sport use suspension designs that have a backwards wheel path?

My thoughts are that it would no doubt change the over all feel of the bike – but would it make it faster??? Who knows…

Wouldn’t it be nice to be able to independently and objectively test the overall efficiency of all the suspension designs..

 

[Sandwich]

I'll weigh in on this with my opinion and what I know...

Higher pivots absorb bumps better, as (exactly as you said) the wheel moves up and out of the way. Lower pivots corner better as the wheel tucks up and into the frame, shortening the wheelbase. Playing with axle path was a big deal a few years ago with VPP and a few others.

I think people stay away from high pivots because of pedal feedback. Many designs need idlers or jackshafts and those are apparently difficult to design properly and lightly enough. Pedal feedback can apparently be a good thing, taking a look at the new lapierre design...

Anyways, it comes down to opinion, mostly, and I think it's easier to build and sell a bike with a lower pivot than a higher one.

As for motorsports, many sports cars use a parallelogram linkage setup, just like a lawwill bike or motorcycle. Actually, mert makes a linkage motorcycle, but from what I understand, the change is so significant in MX that to switch to a non-single pivot design would take years to become competitive.

 

[slowitdown]

Higher pivots absorb bumps better, as (exactly as you said) the wheel moves up and out of the way. Lower pivots corner better as the wheel tucks up and into the frame, shortening the wheelbase. Playing with axle path was a big deal a few years ago with VPP and a few others.

Doesn't the ability of the wheel to tuck up into the frame, and the amount of that tuck, depend more on the travel and not the pivot location?

Why would two bikes with identical 7" rear travel, but different pivot locations, show more "tucking into the frame" with a low pivot than a high pivot? Can you explain that?

 

[P.T.W]

Simple!
7inch frame #1 has a pivot placed 7inches vertically above the bb
7inch frame #2 has a pivot placed directly behind the bb at the same height form the ground.

The rear wheel on frame #1 is constantly moving rearwards under the compression stroke, therefore away from the frame/front triangle.

The rear wheel on frame #2 is constantly moving forwards under the same compression stroke, therefore towards the fame/front triangle or "tucking in"

I know this is a gross oversimplification but simple questions get simple answers.
I'm also a bit disappointed in you slowitdown someone so opinionated and apparently knowledgeable asking such a simple question

 

[Sandwich]

Doesn't the ability of the wheel to tuck up into the frame, and the amount of that tuck, depend more on the travel and not the pivot location?

Why would two bikes with identical 7" rear travel, but different pivot locations, show more "tucking into the frame" with a low pivot than a high pivot? Can you explain that?

The basic concept is that with a higher pivot, the wheel moves back and up through it's curve. The lower pivot moves forward and up. The degree depends on both the length of the arm and the pivot height. A 4ft swingarm will show little curvature, while a tiny one will have a much larger effect.

Basically, the wheelbase shortens with a lower pivot, and increases with a higher one. Thus the "tucking" of the rear wheel up and in. The point of travel just controls "how much" extension or contraction. How much of this is placebo and how much matters is open to debate. Cornering can depend on a host of factors like HA, overall wheelbase, trail, etc...not just suspension design.

 

[time-bomb]

HardtailHack - good question. Hopefully some of the resident RM engineers will chime in as I am always interested in learning new things. My take on this kind of thing is that one isn't better than the other. The manufacture of each type will have you believe theirs is the best but the reality is that there are pros and cons to each design and the rider/consumer will have to decide what suits their riding style and/or terrain they ride on the best.

For example, compare Xprezzo and Appalache to one another. Both are SP but very different. These two companies came about when Balfa was sold off. So the designers/engineers/owners all came from the same place but when they went off to do their own thing they made drastically different designs. Why is this? Simple, because they all ride and they have preferences, it really isn't because one is better than the other. I was talking to one of the engineers/owners of Xprezzo and he simply did not like the way the high pivot bike turned in tight corners due to the wheelbase spreading out as it cycled through its travel. He did like its ability to plow however. They went w/a lower pivot because they felt it was more versatile and better suited for a variety of different trails and because that is what they like.

Anyway, the above is a very high level oversimplification but it kind of illustrates that point that both have their merits and their place in the world of full-suspension bikes but it really comes down to what is best for you.

 

[Slater]

I'm not going to bother with this one, but it'll be fun to read!

 

[William42]

The only bike I've ever noticed a particularly rearward axle path while riding is the canfield jedi, which has over 2 inches of rearward (very extreme). My feeling is, unless its very very extreme, axle path only matters in relationship to what its doing to braking squat, leverage curves and anti squat.

 

[demo 9]

Canfield jedi FTW, no bike motors over bumps like it does, that being said, that is about all its good for, but you have to ride 1 at some point in your life to realize how "extreme" 2.5 rearwards really is

 

[Sandwich]

oh yeah, it isn't necessarily that one is better than the other, just different routes of attack.

maybe a completely vertical path would combine the best of both worlds? VST? 2 Stage? Weird stuff...

 

[time-bomb]

What ever happened to the Sinister Passion and Poison? Those looked like they had the best of both worlds. A true variable wheel path.

 

[HardtailHack]

IMO
High pivots will have brake squat, not jack, that's without a floater or a virtual high pivot point suspension design to elimimate squat, or a split pivot.
QUOTE]

Oops sorry, squat is what I meant.

The reason I asked the question is I am possibly looking at a new frame and I don't know if it's worth worrying about axle paths or just go on angles/dimensions. I previously picked the Maelstrom because of the short rear swingarm and fairly high pivot giving a fairly rearward initial axle path and the fact that the frame had kinda similar dimensions to the only dually I had ridden which was a BB7.
I have been told my Corsair is still a month away and I'm not sure if I will be getting the angled headset when the frame turns up as info on anything Corsair is very hard to get at the moment. If I had of ordered a large and if HA could be run at 64deg it would be fine but I didn't and it can't so I might have to grab a new frame. My other problem is because I'm such a fatty(225lb) I can't ride friends bikes to compare them to mine which is a massive pain.

Thanks for the help so far, not one negative post, must be a record for RM.

 

[buildyourown]

I like low pivot bikes vs high (I've owned several of both) because the chainstays shorten as you go thru the travel. This makes the bike corner effortlessly and pop right out of turns.
Thes super high pivot (Balfa) does do a bit better on square whoops, but it's not worth the trade off.

 

[Sandwich]

I wouldn't be scared of going to a low pivot bike. I went from a Brooklyn Racelink to a Sunday and the bike feels just as natural as I would want it. I definitely noticed the change in braking and it's not as supple over big hits as the link, but it's just different, not bad. The cornering on the Sunday is superb, it is EXTREMELY noticeable at someplace like highland, where there are linked berms which are super tight. On flat or high speed turns, it's not so bad, but the light weight and "flick-ability" of the Sunday really shine in the tight stuff. Pedaling is different...on the brooklyn there was no effect and it all came down to monkey motion...I have noticed weirdness with the Sunday but only in weird circumstances when I'm purposefully paying attention.

tl;dr, if a new frame gets you back on the trail, get one, whatever it is. Try it out. You might like it better, or hate it.

edit: I know I should mention that the Sunday is not a low-pivot bike, but it has many characteristics with a mid-forward pivot, if you look at the axle path on the dw-link website. Not apples-apples but close.

 

[slowitdown]

I'm also a bit disappointed in you slowitdown someone so opinionated and apparently knowledgeable asking such a simple question

Someone has to ask the obvious questions when they're being overlooked.

Obvious COMPOUND question No. 2:

Part (a) Distance of swingarm pivot to axle = Radius, right?

Okay, let's keep the Radius equal, and vary only the swingarm pivot point. Remember, it's a 7" travel design on this pair of bikes.

Bike ABC has the pivot point 1.5" above the BB.

Bike XYZ has the pivot point 0.5" above the BB.

NOTE: the pivots are the same distance in front of the BB.

Part (b) If the Radius is the same on both, how can the wheel move more on one than on the other? It's the same circle, isn't it?

 

[William42]

do the bikes have the exact same BB height? because if they do, the radius will be pointing a different direction because of that 1 inch.

 

[Sandwich]

do the bikes have the exact same BB height? because if they do, the radius will be pointing a different direction because of that 1 inch.

basically. Draw two circles, one .5cm higher than the other. That's the same idea. Angles and scale will vary, but the concept is there. The change is much more drastic when you're talking concentric to the BB and 12" higher....

 

[banj]

If the bikes have the same geometry save for the pivot point the radius will not be the same. The higher pivot point bike will have a larger radius with a "starting" point at a steeper angle.

 

[slowitdown]

do the bikes have the exact same BB height? because if they do, the radius will be pointing a different direction because of that 1 inch.

Yeah, but that looks a little irrelevant. Here's why: the radius remains the same so how can the piece-of-circle at the end of the radius (the axle path) be any different?

A given radius can make only one size circle. Doesn't matter where you put the center of that circle, the circle size is the same.

 

[rosenamedpoop]

Canfield jedi FTW, no bike motors over bumps like it does, that being said, that is about all its good for, but you have to ride 1 at some point in your life to realize how "extreme" 2.5 rearwards really is

I've wondered about this with the Jedi... By "that is about all it's good for" do you mean it's more challenging to turn? Super short initial chainstay length should mean about average CS length while compressed in a turn right...?

 

[time-bomb]

For the purpose of this discussion the radius can be the same but the effect will be different. If the minute hand on a clock swings from 9:00 to 12:00 (this represents the pivot being closer to the BB) it is going the same distance as the minute hand going from 6:00 to 9:00 (this represents the pivot being higher above the BB) but they will have very different characteristics when hitting a bump. Same radius, same travel, different trajectories.

This is a more extreme example than 1.5" vs 0.5" above a BB but it illustrates the same point.

For a real world scenario, see banj's post. You have to increase the radius for a higher pivot to keep other measurements the same: wheelbase, chain stay, etc.

 

[jutny]

I've wondered about this with the Jedi... By "that is about all it's good for" do you mean it's more challenging to turn? Super short initial chainstay length should mean about average CS length while compressed in a turn right...?

jedi turns very well, yes you're right with the short chainstays to begin with, they end up at full compression only mildly longer than some of the long-stay bikes out there. However those long-stay bikes may/maynot be of low pivot design and then have artificially shorter chainstays once compressed. whoa.

either way I love the jedi, and it rides exactly how a rearward path would suggest. (mind you its only VERY rearward on the inital travel. from inches 3-7.75 the bitch is going almost vertical) Very noob (me) friendly for sure through rock gardens and stuff. My next DH bike will be something more conventional (or a silencer)

 

[Steve M]

Yeah, but that looks a little irrelevant. Here's why: the radius remains the same so how can the piece-of-circle at the end of the radius (the axle path) be any different?

A given radius can make only one size circle. Doesn't matter where you put the center of that circle, the circle size is the same.

Who ever said the radius of the circle was what was making the difference? What you're saying is like comparing the top half of the circle to the bottom half - pretty pointless. It's the tangent vector at a given point in the travel that is making the difference here.

Personally, having ridden numerous high-pivot bikes including the Lahar, Superco, BB7 etc and having ridden + owned numerous low to mid pivot (effective) bikes, I think there are two major benefits to low/mid pivot bikes:
1. No need to reroute the chainline to avoid having ridiculous pedal kickback
2. Less CS extension and an easier feel for the rear wheel in corners. All high pivot bikes I've ridden have felt a bit weird in tight corners due to the wheelbase either lengthening or not shortening as much as a conventional bike. DW claims there is a difference in predictability when the bike is sliding when the centre of traction varies more, (higher pivots tend to vary more because the CoM more or less moves forward relative to the centre of traction if either or both ends of the suspension compress). Personally I'm not sold on the predictability difference in terms of actual grip but I have noticed that when you hit corners hard on a high pivot bike, the rear end feels like it's opposing the yaw motion of the bike because the moment arm between rear axle and centre of mass is increasing and the moment arm between front axle and CoM is decreasing (centre of traction moving rearwards relative to centre of mass basically). This makes it feel like it's a bit harder to get the rear end to snap around sometimes, but I haven't spent enough time aboard one of those bikes to tell whether you could really get used to it and compensate 100% for it - IMO chances are you could but I'm not in a position to say.

However, the bump absorption benefits of high pivots are absolutely undeniable. It's crazy what you can ride over/through on some of those bikes without hanging up, the rear end is absolutely able to outperform the front end due to its inherently higher pitching stability (ie hanging up the front wheel is easier to do and can put you over the bars a lot easier than hanging up the rear).

 

[xy9ine]

This makes it feel like it's a bit harder to get the rear end to snap around sometimes, but I haven't spent enough time aboard one of those bikes to tell whether you could really get used to it and compensate 100% for it - IMO chances are you could but I'm not in a position to say.

However, the bump absorption benefits of high pivots are absolutely undeniable. It's crazy what you can ride over/through on some of those bikes without hanging up, the rear end is absolutely able to outperform the front end due to its inherently higher pitching stability (ie hanging up the front wheel is easier to do and can put you over the bars a lot easier than hanging up the rear).

re: first point - yes, the high pivot cornering characteristics felt odd at first. now feels completely normal (though i can't really describe the biomechanical changes), and i can't really discern any negative virtues. not as 'snappy' feeling at exits, but i don't think actual cornering speed is affected detrimentally.

re: last point - no doubt. i'm continuously amazed how well the bike levels out the chunder. it's like cheating.

that said, i do like the more 'playful' feel of low pivots, though shortening the chainstay length on a high pivot makes a substantial difference in fun factor (re: the superco vs the superlong lahar).

 

[eatmyshorts]

I'll weigh in on this with my opinion and what I know...


As for motorsports, many sports cars use a parallelogram linkage setup, just like a lawwill bike or motorcycle. Actually, mert makes a linkage motorcycle, but from what I understand, the change is so significant in MX that to switch to a non-single pivot design would take years to become competitive.

May be missed my point or I wasn't clear...

With all the development that is pumped into motor sport - what wheel paths are used - eg by rally car etc... Just thought I would be an interesting place to start. Motor sport testing is data based and less subjective?

 

[demo 9]

I've wondered about this with the Jedi... By "that is about all it's good for" do you mean it's more challenging to turn? Super short initial chainstay length should mean about average CS length while compressed in a turn right...?

well here is what i notice with mine (and im super happy with it btw)

the more bumps u hit the faster u go, i dont mean u slow down less, it actually goes faster (or at least feels like it) *point into rock garden, just motor over it accelerating, its unbelieveable

it corners nice i think (it is short) and i did a whole season with it for slalom (which it won every race)

it jumps LOW. (auto scrub?) see since it rebounds INTO the frame, the rear "falls away" when you jump, as opposed to a fowards wheelpath that rebounds OUT that "pops"

pedaling is pretty good, louder with the idler but i woudlnt say any worse

I am sure somebody with crazy science will key in here and say this is all wrong, but with riding it there is nothing like it, it is so fast its like cheating


*the only downside, it doesnt "cut" like most bikes

 

[rosenamedpoop]

well here is what i notice with mine (and im super happy with it btw)

the more bumps u hit the faster u go, i dont mean u slow down less, it actually goes faster (or at least feels like it) *point into rock garden, just motor over it accelerating, its unbelieveable

it corners nice i think (it is short) and i did a whole season with it for slalom (which it won every race)

it jumps LOW. (auto scrub?) see since it rebounds INTO the frame, the rear "falls away" when you jump, as opposed to a fowards wheelpath that rebounds OUT that "pops"

pedaling is pretty good, louder with the idler but i woudlnt say any worse

I am sure somebody with crazy science will key in here and say this is all wrong, but with riding it there is nothing like it, it is so fast its like cheating


*the only downside, it doesnt "cut" like most bikes

Cool... I actually feel pretty comfortable with my theoretical understanding of the Jedi, but I'm definitely interested in intelligent real world perception. So, thanks

 

[demo 9]

Cool... I actually feel pretty comfortable with my theoretical understanding of the Jedi, but I'm definitely interested in intelligent real world perception. So, thanks

it is 1 bike that after you buy it, you will never leave it. im on my second, and feel that its entirely worth the money

 

[P.T.W]

Does anyone think that slowitdown would argue about whether the world was flat or a globe just for the sake of it?
Does this place have a iggy function?

 

[slowitdown]

Who ever said the radius of the circle was what was making the difference? What you're saying is like comparing the top half of the circle to the bottom half - pretty pointless. It's the tangent vector at a given point in the travel that is making the difference here.

Someone early in the thread suggested as much. So the "pointless" accusation needs to be levelled at him, not me.

Don't mistake my questions for my actual beliefs or knowledge. I'm prodding the self-appointed "experts" who are pretending they know something about suspension design.

Does anyone think that slowitdown would argue about whether the world was flat or a globe just for the sake of it?
Does this place have a iggy function?

Aren't you a funny little boy? Notice that Socket has demonstrated the error of one of RideMonkey's self-appointed "experts", thanks to my questioning of the "wisdom" of that self-appointed expert.

You can thank me for the question, and Socket for the excellent answer. And if you're gonna ignore someone, I suggest ignoring the resident RideMonkey poseurs, who think that building a reputation as an expert on the internet is the same as actually possessing expertise.

If my exposing fakers and poseurs irritates you, then by all means please feel free to ignore me when I do that.

 

[Sandwich]

Does anyone think that slowitdown would argue about whether the world was flat or a globe just for the sake of it?
Does this place have a iggy function?

seriously...tards be trollin

 

[Sandwich]

Someone early in the thread suggested as much. So the "pointless" accusation needs to be levelled at him, not me.

Don't mistake my questions for my actual beliefs or knowledge. I'm prodding the self-appointed "experts" who are pretending they know something about suspension design.

if you're pointing at me, I said radius controls the RATE of change, while the center of curvature controls DIRECTION of change. IE a lower pivot will never move back, a high pivot will not move forward. The fore/aft location, or radius, will control a sharp curve, or a very broad curve in the axle path. That's what I said before, and I'll say it again.

 

[P.T.W]

Aren't you a funny little boy? QUOTE]

Actually I'm serious...if there was a ignore function on RM i would be using it

 

[Sandwich]

ignore

sure there is...just click on his name, then user lists, then "ignore lists". The link above MAY work.

 

[P.T.W]

Yay it worked...thanks Sandwich....must spread rep 1st tho
The smelly troll boy (see i can call people silly names too ) should feel proud, hes the first person I've EVER blocked here or anywhere.

Now back to your scheduled programming

 

[HardtailHack]

After retiring the Corsair I bought a second hand Nicolai which is pretty much a vertical axle pathed bike and it is definitely different.
First thing that happened was my times got worse as I found I could brake in the rough/off camber sections and I started riding like a sissy, if I tapped the brakes on an off camber section on the Corsair would get a bit sketchy so that was a no no but on the Nicolai it was easy.

I also had a lot more trouble setting up the suspension but I think this was more to do with swapping from an Elka to a BOS, I've ended up running a firm spring and little compression damping and the bike feels almost as poppy as the Corsair but slacker and longer.

I still slightly prefer the rearward axle path overall but the Nicolai frame rides the same every time I get on it and I don't have to worry about snapping bolts etc.

 

[Sandwich]

Hahaha...Interesting commentary, too bad those corsairs ended up being so ****ty...