single pivot or Horst link

[ASB77]

I'm trying to decide on a 130mmish trailbike frame.  I currently ride an old Jamis with a single pivot and no lockout that will bob and bounce if I don't pedal smoothly, so one of my desires on my next bike is for it to pedal well.  Currently I'm thinking FM 1001, LCFS958, or maybe a P1. The numbers keep pulling me back to the 958 but the single pivot pushes me away.   Are there advantages to the single pivot besides simplicity, and am I wrong in thinking that a horst link or similar will pedal better while remaining plusher on the way back down, or am I asking too much and should rely on lockout to take care of my issue?

[mbarronj]

In general, Horst link will have a better anti-squat and anti-rise than a single pivot. It's possible to design Horst links badly, and to design single pivots well. But I would say the available crop of Horst Link or even VPP carbon frames from china are probably better than the single-pivots. The consensus seems to be the Horst link Chinese suspension designs are pretty consistently good. I like how LightCarbon gives suspension curves for their latest frames, even though they are barely readable. You can at least get an idea of how it will ride, and it at least looks like they gave the design some thought.

[Julian]

As mbarronj said, it depends on the design. Anti squat however isn't necessarily a factor. Both designs can have very similar anti squat curves, starting high and going low throughout the travel. VPP on the other hand will usually look a bit different, with anti squat values staying on one level or even increasing throughout the travel. Whether or not that's a good thing, probably can't be universally answered. It always depends. And that's also true for all the other numbers, curves and values. Generally, a single pivot flex-stay design will allow less fine tuning of the suspension characteristics, but be lighter and simpler. Horst link or twin link (like VPP) designs both use a virtual, moving pivot point and offer plenty of tunability. The question is, if you need that on a short travel bike. That's why you'll often find single pivot designs on bikes with 100-130mm of travel.

Back to the anti squat: I've attached the anti squat curves of the LCFS958 and the FM1001 as well as the famed FM936 for reference, all with 30t and 32t chain ring options and the same center of gravity at 1050mm. You can see that the horst link design doesn't have any advantage there. It does offer a more linear anti rise at around 50% though, whereas the other two have higher anti rise at about 100%, falling thoughout the travel.

[ASB77]

I appreciate the replies.  Forgive me for being simple but I don't quite understand the charts and would love a bit of explanation on what is going on at a given point.

[Julian]

I appreciate the replies.  Forgive me for being simple but I don't quite understand the charts and would love a bit of explanation on what is going on at a given point.

No problem, that's what a community is for

If you have general questions about what anti squat is, read this:
https://www.pinkbike.com/news/definitions-what-is-anti-squat.html

In short: When you accelerate by pushing into the pedals, your body's inertia will make the rear suspension squat. But at the same time, the chain pulls on the rear wheel, usually having the opposite effect of extending the rear suspension. That is called "anti squat". The percentage says how much of the inertia-squat is countered by the chain pull. 100% (in theory) means no movement in the rear suspension at all.

Yet, there are many things that play a role here. Two are probably the most important: Center of gravity and chain ring size. Generally, longer legs = higher COG = more squatting (leverage) = lower anti squat percentage. So "your" anti squat can be a bit higher or lower than the one in the graphs, but the curve will look the same. With chain rings, smaller ones have higher anti squat.

The rear cogs also play a role. Depending on the size of the chain ring, anti squat can vary greatly throughout the gears. The graphs show blue areas where all the gear's anti squat curves go through, from 10t to 50t.

Now, it's considered optimal to have around 100% anti squat at SAG point, since that's the travel you're in when pedaling. I've marked that point in all the graphs below. All the bikes here have falling anti squat curves, meaning that anti squat is lower when the bike is deeper in it's travel. Some bikes like the Propain Tyee (VPP) actually have a slightly rising anti squat curve. That can have the advantage that on steep climbs, when your weight is all the way back and the rear suspension is more compressed, you still have lots of anti squat. With bikes that have a falling curve, you may need to lean forward more, decompressing the rear end.

Looking at the graphs, the FM936 with 32t and the FM1001 with 30t should have the best pedaling characteristics. They both have about 95 percent anti squat at SAG in any gear. With the LCFS958, the anti squat with 32t is a bit low, and with a 30t it changes quite a lot with every gear.

But that's just what the graphs suggest. In the end, there are many other factors apart from those numbers. Where your COG is, how "clean" your pedaling technique is, how you weight your bike etc. ... So I'd take this with a pinch of salt. They're all not bad. I'd probably go with the Carbonda FM1001 though, but mostly because everyone seems to love the brand

[ASB77]

Thanks, I couldn't figure out why the chart had a wide range at various points, I understood the 30t vs32t but I forgot about the other end.  I understand now.  I think you are correct that the Carbonda might be the better choice. I'm a bit afraid of the unknown as the only really slack bike I have ridden was an older free ride/all mountain/enduro bike that I didn't care for, plus I'm pretty tall, and there is some mention of the 1001 feeling small so the extra 5mm of reach looks good on the screen at least, of course filling the shock through a window on the fs958 looks like an annoyance. Then there is the p1...

[Julian]

The P1's geometry looks a bit old school to me. Steep head angle and slack seat angle make for a comfortable touring bike, but it'll be less suited for steep climbs and fast descends. And I wouldn't call the FM1001 "really slack". It's bang on with other contemporary short travel trail bikes. However, you could also run a 130mm fork instead of the recommended 140mm and get a 66 degree HA and 500mm reach.

The FM1001 will feel shorter though, at least when sitting in the saddle. The steep seat tube angle means a short effective top tube length and therefore a more upright pedaling position. I consider that a good thing, as long as it's not too short and your knees start hitting the handlebars. I'd say the XL should be perfect for anyone up to 190cm (6' 3") and an inseam of 90cm (35.5").