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Linkage Design

linkagedesign.blogspot.com

 

My interpretation of the Linkage Design graphs is that the Salsa split-pivots have an anti-squat right around 100% at sag, so that's good.

I think the performance of split pivot bikes is probably comparable to a modern Horst Link. Like HL bikes, they have more active suspension when braking (less anti-rise) because the brake is attached to the seatstay rather than the chainstay.

 

I look at lot more around 50% travel and for something around 90-100 as far as AS %

Why?

Because bikes are only at the sag point during a static situation. If you are climbing, encounter a bump, the suspension moves to a point where the curve may have much less anti-squat, then you pedal hard to keep going, but because there's less anti-squat, your pedaling causes the suspension to further compress, kind of getting into a feed-back cycle during rough terrain, most notably uphill, since that's really where you can apply the force like this. It also un-weights the front end when this happens and is generally bad IME. The only positive is the once-touted "massive traction" feel, where it feels like the bike is using more travel uphill on the bump than it would if it was just coasting on the flat, while that can help you dig in, the resulting front-end "lift-off" effect really negates any benefit here IMO.

The problem with the graphs is they don't really show you the slope of the AS plot very well. One may look "flat", the next may look steep, but you have to look at the actual % numbers to figure it out, hence, looking at mid-travel, where you will be often on any kind of non-uniform surface IMO. The static "sag point anti-squat" is not realistic, except for a perfectly smooth road and weight transfer/load (how heavy your pack is, etc.). The steeply falling slopes pedal like crap IME, regardless of the sag AS number. This is also a big reason why a lot of the parallel link makers like the DW, SC, Intense, Yeti (effectively the same) run around 100% out to at least half travel, sometimes 2/3, before dropping off. At those later points it doesn't matter, but I would argue at 1/2 the travel, it does bigly.

Designers have flattened the profile of many bikes these days. Horst link bikes have been significantly flattened out, many single pivots replicate most of the parallel link bike curves, and so on. This should lead to much more consistent pedaling in more situations.

The more neutral braking of a horst-link is not necessarily the best thing. With braking weight transfer, that means the bike will pitch forward more during braking/cornering situations. Some brake squat is often seen as beneficial.

 

I have the 2014 spearfish, 1st year they changed the geo. The split pivot pedals nicely without pro pedal. Honestly, I still have the bike because every time I take it out, I seem faster and prefer it to the brand new machines.

 

Don't go overboard with a bazillion poe hub and you won't ever notice kickback.

 

I have a 2017 Salsa Pony Rustler with the split pivot and have always appreciated the solid rear suspension on climbs. Have never needed to lock it out as compared to the Pike front fork which I regularly lock out on climbs. Haven’t ridden other high end bikes so don’t have anything to compare to (not sure if the PR is considered high end).

 

The other thing is I have found little correlation between the suspension moving and how much of your pedal stroke is converted into forward motion. With all suspension systems, you are going to have some bob/movement due to weight shifts, the mass of your feet moving back and forth, etc. There are rare exceptions, but most are going to move and the more travel you have, the more they are going to do this. I find this to be a big contrast though to a low-AS bike that compresses the suspension due to your pedal stroke/force. In those cases, it's like the harder you try, the less you get out of it. They tried to address this on 3-ring bikes like horst-links by having the granny gear be below/inside of the main pivot, for better anti-squat, but on a lot of stuff you'd want to be in the middle ring, especially if you were a decently fit racer or there were technical obstacles where you just needed to be in a higher gear, but these bikes punished you for pedaling harder, by having so little anti-squat in that other chainring. The idea of "well just always use the granny gear" gets annoying with the way they sometimes drop chains, hesitate when shifting down under power, having to make rear cassette shifts at the same time to account for the giant range difference, etc.-in some situations, it just wasn't practical to be in the granny gear or use it. So anyways, on many of these bikes that had low AS, you had a significant amount of power being robbed by the pedaling forces compressing the suspension. Putting the power down on a steep climb didn't seem to make the bike move forward by an expected amount. When riding the higher AS bikes, this was a bit of a revelation, pedaling harder would make you go measurably faster, instead of bogging down. So my point is there's a lot more to it than the "visual bob". If one can get past that, it leads to a lot more bike-enjoyment IME too.

 

I could probably live with the AS of the Cassidy if some other quality of the bike made the bike attractive, [though the AS curve of the 2021 Primer is the best I've found for tech climbing, and that's a flat AS curve that stays above 100% to about 80% of the travel. I go up limestone stair step ledges pedaling away without fear of pedal strikes.] The LR goes from sag, 2.75 to 2.4. I prefer a more progressive linkage.

All in all, the suspension design seems mediocre.

So anyways, on many of these bikes that had low AS, you had a significant amount of power being robbed by the pedaling forces compressing the suspension. Putting the power down on a steep climb didn't seem to make the bike move forward by an expected amount. When riding the higher AS bikes, this was a bit of a revelation, pedaling harder would make you go measurably faster, instead of bogging down. So my point is there's a lot more to it than the "visual bob". If one can get past that, it leads to a lot more bike-enjoyment IME too.

For the pedaling to compress the suspension, the AS would need to be below 0. So if you're AS is 60%, the bob is still from weight shift. Right? My complaint just has to do with pedal strikes. I can't enjoy myself with a 60% AS bike going up a rocky hill having to be so careful about ramming a pedal into a rock. ugh.

 

One thing that isn't mentioned is cog, which on a bike it's never the same even with the same rider and there's no reference from most manufacturers, (I doubt if anyone actually publish this detail) of cog that corresponds to the given AS values, so this renders any as table utterly useless.

 

Huh? Most tables will show the AS values through a range of cassette gears and you can get a pretty good idea from the pivot location and AS values what will happen by going up or down 2 teeth on the chainring. Yes, not perfect, but not useless by any means.

 

at least frame designers should agree on a common Cog point, but then again it needs to be done on each individuals proporsions to be acurate.

 

He means Center of Gravity I think... I had the same confusion.

 

Without a fixed Centre of gravity, the results can't be compared and are useless, a variable cog will give different as values for the same configuration, so we are basically left with what you percieve while you peddal

 

Is it going to change that much? The more optimal the AS curve is, the more that CoG won't matter, since if you lean back more or have a heavier pack, the suspension that has "squatted" to a new position will still have a healthy amount of AS, as long as it's not one of those steeply falling curves or way less than the numbers I was mentioning mid-travel.

 

Open up linkage design and move Cog around and see how much difference it makes, add inclines, body proportions, bike sizes, sag, rider weight and most of all no one agrees where that Cog is, so any given value is irrelevant for comparative use between models, sizes and brands.

 

To calculate optimal as you need optimal cog, it varies, that's the issue

 

I thought 100% was that the extending force was at balance with the estimated weight shift. Below 0% is actual compressive force from the chain.

Enginerding: What Is Anti-Squat & How Does It Actually Affect Mountain Bike Performance? - Pinkbike

Put on those thinking caps and get ready for a deep dive, complete with illustrations, into the definition of anti-squat.

www.pinkbike.com

Seeing as the load transfer is trying to rotate the sprung mass of the bike and rider, if your anti-squat percentage is 100% then the anti-squat forces exactly balance out the tendency of the suspension to squat under the load transfer from acceleration and the net result is that there is no suspension compression or extension.

If the anti-squat force line crosses the front axle line at the ground, we can call this 0%, as none of the tendency to squat is counteracted and the suspension compresses solely due to the load transfer.

Crossing the front contact patch line half way between 100% and 0% results in 50% anti-squat and half of the force needed to combat the squat tendencies is combatted. The net result being some suspension compression, but not as much as if we had 0%.

Going under 0% the anti-squat forces actually work with the suspension compression caused by load transfer and put us in a pro-squat zone. In this region the suspension will compress further than at 0% with the help of the pro-squat forces.

 

I thought 100% was that the extending force was at balance with the estimated weight shift. Below 0% is actual compressive force from the chain.

Enginerding: What Is Anti-Squat & How Does It Actually Affect Mountain Bike Performance? - Pinkbike

Put on those thinking caps and get ready for a deep dive, complete with illustrations, into the definition of anti-squat.

www.pinkbike.com

Read the end of the paragraph and you'll understand.

"Above our 100% mark, where we’ve effectively separated the drive forces from the suspension response, the anti-squat forces will actually be more than enough to combat the squat tendencies, and the rear suspension will extend with that excess force."

100% is balanced out, lower some peddaling force will not counter act the tendency of the system to squat above it extends.
But in that illustration you can clearly see the reason why I said earlier that without edefining where the CoG is every calculation is useless and irrelevant your CoG is constanly moving around the bike while climbing add all other variables and you get the idea, rider proportions - height, inseam, weight etc, body position etc. The only way this can somehow works is to assume CoG is fixed at point a and ride in straight without budging from your asumed position, which is impossible and well kinda stupid on a mtb.

 

You guys wanna see something bonkers? This eBike has almost 200% anti squat (though more like 150% at sag) with a high pivot design without an idler. To cap it off, It also has an exceptionally high torque custom motor just for this model. Laying hard on the pedals must want to launch you off the seat with every pump!

Haibike XDURO Nduro 2020

En esta entrada voy a analizar a las dos versiones de la Haibike Flyon, el modelo XDURO Nduro con 180mm de recorrido y el XDURO AllMtn con ...

linkagedesign.blogspot.com

 

I have been interested in the Salsa Split Pivot for a while now as well, but their full suspension bikes aren't very popular compared to something like a Santa Cruz, Trek, SpecialEd. But everything I have read says they are good pedaling and climbing bikes, but the spearfish and horsethief might not be getting much attention because they aren't crazy slack, long, low bikes. They are made more for Midwest riding which involves a lot of pedaling, some climbing, and typically not a lot of crazy descending.

 

SpecialEd: lol.

I love my enduro 27.5s, but they gotta be able to climb.