Is it mainly a full-suspension thing where the rear mechs can’t keep up with suspension travel and subsequent chain growth/contraction?

Possibly, I certainly never very very rarely used to get any issues with chain drop on 2x or 3x on hardtails, I did have one full suss though which used to throw it regularly, but it was losing it off the bottom of the front ring in very rough/fast stuff so would normally pedal back on, and I think a clutch would have sorted it, but other full suss frames before and after that one were as reliable as HTs.

I still don’t get all the hate, 1x works for some people brilliantly, it even works for me brilliantly on some of my bikes, but 2x and 3x also work brilliantly and gives some options that 1x doesn’t.

I’m pro-1x, but anti-1x-compulsion 😉

scotroutes – Member
I’ve already said that I think 1x is ideal for those that can’t coordinate the use of two thumbs.

….and already said that you’ve already said that….. several times. It’s almost as if it were some kind of trolling… 😉

Mike, I’d vote keep the tab, or perhaps include a bolt on version? (If such a thing exists)

Something that hasn’t been mentioned is the effect of chain line (the important bit of chain line, in the vertical/longitudinal plane, rather than the lateral/longitudinal place) on full suspension bikes. With most designs the anti-squat and pedal kickback is vastly higher in the granny ring than the big ring – if it has a nice balance of bob resistance without losing too much traction through stiffening in the middle ring then it’ll bob too much in the big ring and stiffen too much in the granny.

Something that hasn’t been mentioned is the effect of chain line (the important bit of chain line, in the vertical/longitudinal plane, rather than the lateral/longitudinal place) on full suspension bikes. With most designs the anti-squat and pedal kickback is vastly higher in the granny ring than the big ring – if it has a nice balance of bob resistance without losing too much traction through stiffening in the middle ring then it’ll bob too much in the big ring and stiffen too much in the granny.

Do you have the maths for that chief? I have had a quick go at it and the size of the front chainring seems to cancel out (in rough approximation territory). The reason the anti-squat is high in the granny is because the gear is lower. If you ditch the granny but put on a dinner-plate size first cog for your middle ring to achieve the same gear ratio, then the effect appears to be broadly the same for the same amount of pedal push.

No, the reason for the change in anti-squat is due to the change in the chain line force vector and its interaction with the line between axle and instant centre and how that moment balances the moments generated by the force vectors from the contact patch (driving force) and rider mass centre (inertial force).

You can simulate it in various packages or have a look at this blog;

http://linkagedesign.blogspot.co.uk

anti-squat is due to the change in the chain line force vector and its interaction with the line between axle and instant centre and how that moment balances the moments generated by the force vectors from the contact patch (driving force) and rider mass centre (inertial force).

No, the reason for the change in anti-squat is due to the change in the chain line force vector and its interaction with the line between axle and instant centre and how that moment balances the moments generated by the force vectors from the contact patch (driving force) and rider mass centre (inertial force).

You can simulate it in various packages or have a look at this blog;

http://linkagedesign.blogspot.co.uk
Yes I know that, it is what I am trying to do the maths of, but I can’t get to the same conclusion. Except when you say “instant centre” you are probably talking about what I would call “momentary virtual pivot point” (which is different).

[“Instant Center” (sic) is part of Tony Ellsworth’s theory about why his four-bar designs worked, and is basically wrong (though it didn’t stop him patenting it). Instant Centre is relevant to car suspension designs because in those, the wheel plane is at right angles to the suspension bars and you need to keep track of how the wheel angle to the vertical changes through the suspension travel because of the tyre contact patch etc.]

You don’t have to do the maths – ride a full-sus with a double or triple and pedal up some hills with the shock open in similar gears in all the rings (ie big to big, middle to middle, small to small) and the difference is obvious.

I would call it effective pivot point but instant centre seemed more popular…

Coming in to this thread a bit late in the day, but its timely as I am just about to change bikes. Of the two options I am considering one has no option for a front mech, the other does. Thought process so far:

Trying to take a balanced view as part of the new bike choosing. On my main bike I am currently running 2×10 with 26/36 and 11-36, but would like a slightly lower bottom gear because where I live has a lot of long steep climbs. I have pretty much never had an issue with dropped chains, front mech issues etc, so it works OK, but having a shifter and dropper remote on the same bar is bit of a PITA

I am definitely going to try 1×11 on the new bike as I can see the benefits. Going 30T chainring with 11-45 would give me my slightly lower bottom gear, including allowing for me going to shorter cranks which make a difference to the gearing (or required torque to be more correct). At the top end I would only lose just over 1 cog, so not really an issue

A couple of things I shall be avoiding at least for now:
1) SRAM Eagle because I am not prepared to spend £250 if I trash my mech
2) Di2 for the same reason and not convinced it is yet proven reliable if given a bit of a knock and then submerged
3) The Shimano 11-46 cassette which must be the most bodged bit of kit in Shimano’s range. They have taken an 11-42 and just changed the largest sprocket rather than any intermediate ones, so the jump between the two largest sprockets is 24% which is ridiculous

So for me, I reckon 1×11, 30T oval front with a One Up kit for the Shimano 11-40 which will give 11-45 in decent steps. Will probably also choose the bike that will allow me to go back to 2x in future if needed

You don’t have to do the maths…

Oh but I do, I do. Also, it is possible the effect is different (ie the difference you notice between bigger or smaller front chainrings) when running easy or hard gears at the back. I will have to resort to a computer for this I think.

Is it only me that never drops chains on 2x?

Me neither. Or on my old 3×9 Yeti.

CaptainMainwaring – Member

So for me, I reckon 1×11, 30T oval front with a One Up kit for the Shimano 11-40 which will give 11-45 in decent steps. Will probably also choose the bike that will allow me to go back to 2x in future if needed

IF you’re going to the expense of a Oneup kit for the 11-40, I would seriously consider a SRAM GX 10-42 from bike-components.de – comes with an X1 chain, and make the switch to the XD freehub

https://www.bike-components.de/en/SRAM/GX-11-speed-XG-1150-Cassette-PC-1130-Chain-Set-p50103/

honourablegeorge – Member

CaptainMainwaring – Member

So for me, I reckon 1×11, 30T oval front with a One Up kit for the Shimano 11-40 which will give 11-45 in decent steps. Will probably also choose the bike that will allow me to go back to 2x in future if needed

IF you’re going to the expense of a Oneup kit for the 11-40, I would seriously consider a SRAM GX 10-42 from bike-components.de – comes with an X1 chain, and make the switch to the XD freehub

https://www.bike-components.de/en/SRAM/GX-11-speed-XG-1150-Cassette-PC-1130-Chain-Set-p50103/
Or I could just use a Shimano 11-42. 30/42 would only give me exactly the same as my current 26/36 taking the shorter cranks into account. I want slightly lower gearing, hence 30/45 using the OneUp kit which works best with the 11-40 cassette

ride a full-sus with a double or triple and pedal up some hills with the shock open in similar gears in all the rings (ie big to big, middle to middle, small to small) and the difference is obvious.

Which full sus?

Which full sus?

All of them!

Well I’ve done a bit more maths and in fact if you can lay your hands on a full suss with the pivot point (real or virtual) at the BB axle (Cove G-spot, anything else?), you will not notice any difference. The effect then varies with how high the pivot point is, so it would be big on Oranges etc.

Well I’ve done a bit more maths and in fact if you can lay your hands on a full suss with the pivot point (real or virtual) at the BB axle (Cove G-spot, anything else?), you will not notice any difference. The effect then varies with how high the pivot point is, so it would be big on Oranges etc.

Yes, with a concentric BB single pivot the force vector from the chain can’t generate a moment to counter pedal squat – and has zero chain growth for the same reason, so there’s no kickback. But that’s the only exception. The latest Demo is a concentric BB pivot Horst Link and the Pole hikes are concentric BB pivot short-link 4-bars and they don’t escape the importance of chain ring size.

The effective pivot point is high on lots of modern bikes, partly due to the popularity of 1x – many older designs relied on the extra anti-squat from a granny ring to control bob. Just draw lines through the main links to project the pivot point and even Horst Link designs like the Capra and Patrol have high pivot points.

Umm, according to my model chain tension does generate squat or jack even on something like a G-spot (in any gear other than 1:1). Or to put it more generally, when the chainline is parallel to the (real or virtual) swingarm, chain tension has very little effect on the suspension, the more it deviates the more chain tension will move the suspension.

Also, I think drawing lines through the main links will get you to the height of the instant centre, it won’t necessarily tell you about the height of the pivot point of the virtual swingarm, which is what we are interested in.

Anyhow, if I got time I will try to represent my maths mark II on a pretty graph to show you.