[Closed] Single pivot vs the rest

I can tell the difference under braking, the single pivots I've ridden do skip their back wheels around more than the multi-links (Spesh FSR, Giant NRS and Anthem). Not enough to worry too much about riding a single pivot, but you can notice it.

Pretty much every bike at the WC XC this weekend is a (linkage shock) single pivot

Nope, some of them had a linkage with a concentric rear axle, and some of them were short link four bar - counter rotating.

I think as long as the geometry and the shock and the suspension layout are properly designed to work together, then all bike suss designs can be pretty good.

I've had (simple) single pivot, horst link, VPP and linkage activated single pivot.

They all did different things well and different things not so well. I'd be more concerned by geometry than suspension type if I was buying blind without test riding.

I think these days most manufacturers have also got their heads round custom speccing shock tunes to make the best of their chosen suspension designs for the average rider - I remember when Orange 5's were the thing, there were a lot of threads about how much better, and how much less trap-doory they were after sending the shock off for a tune, which doesn't seem to be a "by default" anymore. Single ring also means that designers are also only trying to work with one set of chain tension induced parameters, not 2 or 3.

Is a concentric rear axle not just another type of single pivot? if not, what is the definition?

My issue isn't with single pivots (I have an evil), it's with orange full suspension bikes (and, in general, the quasi xenophobic 'it was built in Britain therefore it's better') - where they spend their money, I do not know. Having to put £800 of ohlins or cane creek on a bike for it to perform tolerably is not a credit to it.

It's all in the patent these days, Orange are pretty much a true Single Pivot (SP), it has benefits, it has negatives, concentric rear axles are pretty much that, a pivot concentrically at the rear axle to assist in improving braking performance on a SP.

I've said it a few times, but rear shocks and the way they are tuneable and can be dialled in for the frame has meant designs that weren't quite good enough a decade or more ago are now kind of working, multi link SP's are coming in a lot more now, as they can dial in the progressiveness of the frame and put a shock on to suit, it's all pretty good to be fair and the old snobbery of SP vs 4-bar vs VPP vs DW vs etc isn't really that viable any more.

I prefer single pivot (linkage driven or otherwise). Just seems more predictable feeling.

Which Orange thread? I can't find it.

Is a concentric rear axle not just another type of single pivot?

Yes but the brake is mounted on the linkage, not the chainstay, like a classic single pivot (eg Orange). Whether that makes any difference, I don't know, but it is in the subset of linkage driven single pivots

If the rear axle rotates around only one pivot on the frame the axle path is that of a single pivot Shirley?
Seat stays on a concentric rear axle pivot are just a very long shock linkage with a brake bolted to it to revolutionise the braking experience.

@Rickos - https://singletrackworld.com/forum/topic/the-future-was-bright/

Is a concentric rear axle not just another type of single pivot?

Yeah, pretty much, just being nerdish

Thanks

can someone draw pretty pictures, i have no idea what the differences are.

i'd say concentric rear axle IS a single pivot..

If you removed everything but the chain stay, it would still 'swing'.

Same with a linkage driven single pivot (like the OLD commencal metas).

My stumpjumper ISN'T single pivot cos if you just had the chain stay, there'd be no wheel attached to it (FSR/horst whatever...)...

I GUESS the NEW stumpjumper IS a single pivot, as long as the flex in the stay is in the seat stay, and nil in the chain stay?

DrP

weeksy
Full Member
can someone draw pretty pictures, i have no idea what the differences are.

How about pictures with added bonus cat pictures?

https://www.pinkbike.com/news/introducing-behind-the-numbers-a-new-suspension-analysis-series.html

https://www.pinkbike.com/news/tags/behind-the-numbers/

can someone draw pretty pictures, i have no idea what the differences are.

The internet is full of articles explaining the theories behind different designs.

https://www.bikebros.ca/blogs/spoke-words/suspension-designs-explained/

I've never had a bike with a concentric rear axle. Is it the seatstay or the chainstay that holds the hub, or both? I'm just wondering if you lock the rear brake does it stop the rear wheel rotating on the axle during compression like an Orange style solid swingarm?

Or does the chainstay swing like an arm while the seatstay/brake caliper counter rotates?

I think I've owned all the main designs at some point:

Single Pivot (SC Superlight and Heckler)
VPP (Blur LT)
DW Link (Five Spot)
Faux Bar / Linkage Single pivot (On One Codeine)
Horst Link (Stumpy FSR and Whyte S150)

Conclusions? I probably spend too much money on bikes. Also comparing bikes from different eras is probably pretty pointless.

I think the best suspension design out of them all was the DW Link, it just had no vices. Brake performance like a Horst Link, pedalled like a VPP.

But the best performing bike is unsurprisingly the newest, the Whyte. Good suspension plus modern geometry.

Which of the chainstay and seatstay have the axle fixed to them is not relevant to how the suspension behaves. How the seatstay rotates depends on how its top link is arranged. If it is attached to a horizontal (ish) rocker it won't rotate much until you get deep into the travel. If it is attached to a drop link type of thing it will be the opposite of that.

A Horst pivot close to the axle will behave in the same way. ETA this has been the recent trend with Horst links.

All I know is that when I bought my first non single pivot bike (anthem) I was worried that the lock out was not in easy reach.
Never needed to use it.
My Marin's were always getting locked out.

Does anyone else other than Orange currently make a simple (non-linkage) single pivot frame?

Some of the steel ones - Starling are single pivot, aren't they?

Ive never heard of these:
https://www.pinkbike.com/news/the-tor-zenith-is-a-fuss-free-australian-made-steel-trail-bike.html

PP Shan no5

This potential deathtrap (remember when it all kicked off on Vital)

A Horst pivot close to the axle will behave in the same way.

I thought the Specialized patent was about the placement of the pivot, so putting it close to the axle won't technically be a Horst pivot, surely?

You're right thols2! So what does one call a design with the pivot anywhere?

Mind you, the patent only requires the pivot to be "below" the axle, so it could still be very close.

Demoed several oranges over the years and i've never got on with the suspension, the feedback through the pedals and tendency to lock up over braking is noticeable. My old linkage driven single pivot nukeproof mega also had the same tendencies but not quite as bad.

My favourite linkage of any bike i've owned was my banshee spitfire - that pedalled well and stayed constantly composed. I think it's very similar to a DW link in design.

My current bike, a Whyte S-150, is okay. It uses a horst link that is really plush but bobs a lot and lacked support before a megneg upgrade. After that it runs much better.

What's interesting is how some suspension designs, even though they are touted as the best thing eva, have just dissapeared..

This Marin, with the R3act suspension seemed to tick ALL the boxes...

But...my theory is that it's died a death, and Marin now uses a traditional faux bar design, purely cos it's PIG UGLY......
Regardless of how it rides, how it sells is also an important feature..

It's quite interesting - i spent my lunch looking up this frame/system.
Matt Jones had a video from 2019 spouting it's wonders... and tehn ALL subsequent Marins scrapped it!

DrP

the quasi xenophobic ‘it was built in Britain therefore it’s better’

I don't think many people really believe that - for me, it would be about supporting what is in bike terms a local business.

I've literally just bought my first proper single pivot bike with a Cane Creek DBcoil IL, tuned by J-Tech. I really, really like it in the 100k I've ridden it so far, climbs well, descends well and with it being the first ever coil shock I've owned, it's lovely and plush but seems to have no less 'pop' than the bike it replaced. This could all be new bike rose tinted glasses though 🙂

The other 3 bikes I've owned had VPP, Horst Link and linkage driven single pivot and I don't think I've noticed any brake jack or whatever it's called.

Hopefully a picture:
[img] [/img]

it would be about supporting what is in bike terms a local business.

The basic problem with this is that you are saying that there are better products available for the same money, so you will reward a local company that makes an inferior product. Wouldn't it make more sense to buy the best bike and donate some money to charity if you want to help locals? You are basically treating local companies as charity cases that can't get by unless you just donate money to them.

Ah yes that Marin, I was intrigued by that. Going back a bit to their Jon Whyte designed days. It makes sense, one system for getting the axle path where you want it and a separate shock driver linkage to get the spring rate curve right. As the DW6 system on the Atherton bikes has.

“ This Marin, with the R3act suspension seemed to tick ALL the boxes…”

According to the marketing it did. According to analysis in linkage software it really didn’t:

https://linkagedesign.blogspot.com/2018/04/marin-wolf-ridge-29-2018.html?m=1

(Translation for non-geeks - pedals very efficiently at the expense of decent suspension action deeper into the travel).

There’s nothing wrong with a well executed single pivot design. Incidentally, the recent high pivot bikes like the Commencal WC DH bike, or the Forbidden or Deviate trail bikes, have massive brake squat, far “worse” than any Orange.

I had two giants before mine. The suspension on the reign was sublime once i had had the shock PUSHed, supportive, bottomless, free of bob and brake squat and jack. I didnt see how it could have been improved.

I also had to change 10 bearings every year or so, and a bush every 6 months.

Got an Orange now which rides great, squats a bit, bobs a bit, but rarely need maintaining.

My sweet Lord that’s a pretty bike. Love the colour.

I’ve only ever owned two full suspension bikes. A Trek Fuel Ex9 from 2014 and a second gen Cotic Flare. The Flare was a lot more fun to ride for me. The Trek was like an old persons comfy chair.

@funkmasterp thanks, considering the painting was a bit of a rush job, it worked out amazingly!

There’s nothing wrong with a well executed single pivot design. Incidentally, the recent high pivot bikes like the Commencal WC DH bike, or the Forbidden or Deviate trail bikes, have massive brake squat, far “worse” than any Orange.

Whether that is a bad thing or not depends on whether you think brake-induced squat is the cause of the phenomenon commonly known as "brake jack".

My DH bike got nicked in the Alps one year so I had a succession of hire bikes over the rest of the week.

The think I noticed more than the suspension design was a) did it fit b) had the fork been serviced recently.

I went through:
my Horst link canyon. Ace. It fitted!

DW pivot. Fork was the same as mine, but it felt like it hadn't been service in ages.

Morwood single pivot linkage, shock was too soft

Polygon. Dual floating link. The bike was too small.

Santa cruz V10. In xxl it felt amazing. Mostly because it fitted better than the rest.

The suspension design really didn't make much difference to me.

I had an orange segment, I never noticed any brake jack, significant bobbing or getting less plush under braking. It only had 110mm of travel so maybe that's why I never noticed any of those things.

“ Whether that is a bad thing or not depends on whether you think brake-induced squat is the cause of the phenomenon commonly known as “brake jack”.”

I think “brake jack” refers to the stiffening of rear suspension under braking, which is caused by the braking torque acting on the suspension and is almost always a squatting not jacking (rising) force. The front suspension dives under braking (telescopic forks have no anti-dive) so riders may assume that there is brake jack when actually they’re feeling brake squat and stiffening at the rear but brake dive at the front.

From the limited number of full-sus bikes I’ve ridden, I feel that very low brake squat as on typical four bar bikes (Horst link style) isn’t ideal - I’d rather the bike maintain its angles better rather than stay supple but steepen up under braking.

Counter-rotating four bar bikes (like Birds) have more brake squat, as do most short link designs. Single pivots have more all the way through the travel but how many of us are hauling on our brakes when bottoming out?

A great example of where a linkage-driven single pivot has been designed incredibly well is Evil's DELTA. Also Dave Weagle.

It has so much progression built in, it works best with a coil shock. And for me, with as little rebound and compression framing as possible.

Its almost like the shock doesn't really matter, because the engineering is so good.

The basic problem with this is that you are saying that there are better products available for the same money, so you will reward a local company that makes an inferior product.

I don't believe they do make an inferior product. I wouldn't buy one if I did. Not that I am buying one anyway as they are too expensive (see above).

From the limited number of full-sus bikes I’ve ridden, I feel that very low brake squat as on typical four bar bikes (Horst link style) isn’t ideal – I’d rather the bike maintain its angles better rather than stay supple but steepen up under braking.

@chief what you are describing there is a little different from the classic description of "brake jack" which involves the suspension "stiffening", which I assume means not responding to bumps (eg braking bumps). Do you notice a difference in bump response?

All I know is that when I bought my first non single pivot bike (anthem) I was worried that the lock out was not in easy reach.
Never needed to use it.

Pretty much my experience with my 2017 Anthem. I ride it in the middle trail setting 90% of the time, including on tarmac and smooth stuff, but could easily ride it fully open and not notice any pop when pedalling.

“@chief what you are describing there is a little different from the classic description of “brake jack” which involves the suspension “stiffening”, which I assume means not responding to bumps (eg braking bumps). Do you notice a difference in bump response?”

It’s hard to tell because from years of riding hardtails a lot I’m programmmed into not braking on the rough stuff, especially with the rear brake. But I am very sensitive to geometry changes, I’ll spend quite a while fiddling with suspension to get it feeling right whilst also having the sag at both ends to settle the bike at the right BB height and slackness.

Is a concentric rear axle not just another type of single pivot?

Split Pivot or Trek's Active Braking Pivot is basically a single pivot for pedalling performance but not for braking performance. Does what it says on the tin in my experience. Noticed quite a difference in how active the suspension was under braking going from a Split Pivot to normal single pivot, but got used to it after a while.

The proliferation of single pivot flexing stay designs cropping up at the XC end of things is mostly down to weight. For shorter travel applications the braking performance of the suspension isn't such a big deal. Flexing stays create additional rebound force. Not a huge fan of pogo sticks or unpredictable rebound. Some are worse than others and it's not always something that just slowing the shock down can cover up. To get similar single pivot anti squat or pedalling response to VPP, DW, Yeti it results worse pedal kickback and constricts the suspension movement under power. Probably fine for short track races and punching up climbs but constant tugging back on the cranks gets annoying and tiring on longer rides IMO. Pretty sure Santa Cruz said last time they updated the Blur they didn't want to compromise suspension performance just to save weight? And yet here we are.

I generally think DW Link is one of the best. But not all DW Links are the same and other designs have been catching up in recent years.

I don’t believe they do make an inferior product. I wouldn’t buy one if I did. Not that I am buying one anyway as they are too expensive

If they're too expensive, that's exactly the same as saying there are better products available for the same money. That means you are accepting an inferior product based on it being locally made.

Probably fine for short track races and punching up climbs but constant tugging back on the cranks gets annoying and tiring on longer rides IMO.

Current Scott Spark owner here, and I’ve never noticed any tugging back through the pedals. It does stiffen up when braking heavily downhill on multiple “stutter” bumps though, and is sensitive to rebound - better running a slower rebound on root littered trail to balance the flex stays*.

*I think, im not a mechanical genius but it feels better to me.

If they’re too expensive, that’s exactly the same as saying there are better products available for the same money

No, that assumes that spending more elsewhere would get you something better. But in this case "better" is so subjective that these discussions make little sense. We buy the bikes we like, whatever the criteria, and we enjoy them. We pay the money we want to pay.

Just for balance I only ride hardtails (now) so my knees are my suspension. They’re single pivot.

I have a Starling Murmur (non-linkage single pivot) and came from a V4 Nomad (VPP). I definitely feel like the Nomad was a bit more active under braking than the Murmur. The Murmur feels better pretty much everywhere else though. Hard to compare directly though, as there are a lot of other differences between the bikes.

Current Scott Spark owner here, and I’ve never noticed any tugging back through the pedals.

Not ridden a Spark TBH. Some are better than others. But put your back wheel up against a wall and compress the suspension, the cranks will rotate back slightly.

Just for balance I only ride hardtails (now) so my knees are my suspension. They’re single pivot.

You will also be using your angles and hips so not single pivot at all.

Another linkage/flex stay single pivot:

New MMR race bike

Photo near the bottom

The brake mounts have been decoupled from the swingarm to isolate braking forces and reduce weight.

(my bold)

Any of you guys able to explain how this works?

Just looks like it has been decoupled from the seatstay - so is unaffected by the flex in the seatstays.

Who loves them

Me.

My Orange is a brilliant mix of fun and capable.

I've owned many, many MTBs and some other suspension layouts undoubtedly handle some types of terrain better - but the only place I actually struggle a bit on the Orange is proper steep & rough, where my fingers involuntarily grab the brake levers. More skilled riders may not have this issue.

A few broad thoughts on different suspension layouts I've owned...

Four bar - Generally good, but pedal bob can become an issue on some bikes (old Mega 290). Others were very sprightly (Zesty).
DW - Very good, responsive under power but more neutral/less engaging feel than a single-pivot. Might be my ideal choice for a big bike.
Maestro - As above.
Faux-bar / linkage SP - Predicatable, involving, more feedback than the above. Like a "slightly less SP" feel. Konas didn't pedal well.
ABP - A good compromise, basically felt like a lively four-bar.
Mondraker Cero - Very supple & composed, pedals great, felt like a hot knife through butter on rocks. Actually this would be my choice for a long travel bike.

I didn't think locking out under braking was actually too bad as it felt quicker than with the brake isolated via floating arm as you would just skim over the bumps. Certainly the best results were with no floating arm. This was going back to the 222 though.

I honestly think it's a bit over thought for most people including myself. as long as the angles are good, the rebound is controlled and the sag is set and it doesnt blow through the travel they all do the same thing.

I wouldn't have an Orange again though. No bottle cage mount. Which is the actual issue.

Shock tune makes a big difference, a mate was horrified that my 20 yr old Marin East Peak with the original non-adjustable Fox shock was plusher than his shiny new Orange Five with its fancy tuneable shock, admittedly his bike didn't bounce like a pogo stick going uphill.

Just looks like it has been decoupled from the seatstay – so is unaffected by the flex in the seatstays.

Other way round maybe? If the brake was on the chainstay it would cause the chainstay to flex (given it’s designed to flex). That might cause both odd (lopsided even?) suspension action and the possibility of the calliper moving relative to the disc (bad for the pistons).

Possibly a flexing chainstay that carried the calliper would cause brake rub too.

But from the pics it is clearly attached to the chainstay, not the seatstay. The interesting bit is that the forward end of the post-mount structure appears to be built in to the chainstay, the back end appears to pivot separately on the axle rather than being built in. I guess that helps keep the structure smooth and symmetrical side-to-side so it can flex evenly. It will cause the chainstay to flex, but the chainstays are no doubt build strong to reduce that to acceptable levels. With this type of design, you can choose where you build in the flex, and you want to attach the brake caliper to a non-flexy part.

Edit got seatstay and chainstay mixed up myself doh

Yeah I don't think it does anything clever to the suspension kinematics, it just attaches the brake only to the chainstay, allowing the seat stays to flex as designed.

Scott Sparks are similar:

Have had two oranges and a couple of Kona single pivot faux bar bikes. Both konas bobbed a lot under pedalling. I "fixed" it on the last stinky with a better shock which meant I could just turn the back end off while climbing.

The oranges are absolute hooligan machines. The first, an alpine 160, climbed ok, but it would be comprehensively pounded into the ground by the later alpine 6. I don't know how, but it's a proper mountain goat and will spring up things to my astonishment (I'm not a climber, at all). I've never really noticed either misbehaving under braking. It might squat, it certainly doesn't jack (the eldest kona probably did this as its main pivot was behind the BB). The 6 is like driving a bulldozer downhill, you sort of aim it and hang on, the bike will get you there no matter what's in the way.

I've a whyte e180 which is a proper 4 bar bike. It generally rides just like the 6, but there's something wrong with their kinematics - without very precise shock pressure control it has a tendency to collapse somewhere between mid-stroke and full travel.

I'd quite fancy a modern linkage driven single pivot like a Yeti ASX;

https://www.thebikelist.co.uk/yeti/asx-2007-frame

This seemed to have the benefits of an Orange style system - mud clearance, big main pivot bearing out of the way of filth - with some additional stiffness and adjustment of the shock curve.

Whyte / Marins Quadlink 2 system was a 4 bar with some of the same benefits.

As has already been said, the variation within systems is larger than the variation between them.

It's all trade-offs. I prefer a fairly linear, high anti-squat bike - one of the reasons I bought my Bird.

I loved the old Coiler too!

I'm going to own up to not really being that sensitive to the differences in suspension systems.

I've owned a couple of linkage driven single pivot Konas, a couple of Horst pivot Specializeds and one Lawill Yeti (many, many bearings) as well as having the odd borrow of an Orange.
They all squished and bounced and massaged my abilities as far as they could. The suspension layout was never the limiting factor.

Brake Jack/Squat only matters when you use the brake, there's a simple fix for that 😉

The one thing I would like to play with is a (cheap) longish travel, concentric BB pivot type bike.
More for it's zero chain growth, single speeding possibilities, as I understand it would make for a "terrible" pedalling bike, but if it were exclusively for uplifting (DH use), I could see such a machine being great fun...

I do think MTB suspension suffers a bit from over analysis, some things can actually benefit from a more 'agricultural' approach being taken...

Ah thanks for that Scott Spark PIC @Superficial.

“
I do think MTB suspension suffers a bit from over analysis, some things can actually benefit from a more ‘agricultural’ approach being taken…”

I’d argue that the reason most bikes have decent suspension now is that things have been analysed properly. If you look through the Linkage Design blog you’ll see that most bikes of a given intent have converged on similar kinematics, whilst 10+ years ago they were all over the place. And those similar kinematics are despite the designs being different types.

Edit got seatstay and chainstay mixed up myself doh

Not as badly as me when re-read what I wrote. Ouch.

I’d argue that the reason most bikes have decent suspension now is that things have been analysed properly. If you look through the Linkage Design blog you’ll see that most bikes of a given intent have converged on similar kinematics, whilst 10+ years ago they were all over the place. And those similar kinematics are despite the designs being different types.

I'm sure there have been improvements, how much is due to kinematics, how much to shock development?

But also how many riders really find the benefits and how many are being a bit "princess and the pea" about stuff they read in MBR?
A bike that fits well is probably more beneficial for most riders...

“I’m sure there have been improvements, how much is due to kinematics, how much to shock development?”

It’s both but if you look at the kinematics for bikes that were great ten years ago, in comparison there were lots of bikes that were hopeless (eg regressive leverage curves so they’re bad at small bumps but bottom out easily, v low anti-squat so they bob horribly, v high and rising anti-squat so the kickback is really bad, etc).

Nowadays the majority of frames have pretty decent kinematics.

“A bike that fits well is probably more beneficial for most riders…”

A bike with good geometry for how you’re using it is more beneficial. A bike that merely fits well isn’t good enough. A bike that fits well with great geometry and great suspension kinematics and a great fork and shock is best.

“But also how many riders really find the benefits”

I doubt most can isolate or explain the differences - but that doesn’t mean they don’t enjoy a bike that rides better.

Anyone remember Monolink suspension? Guess Maverick took it to the grave? Probably quite difficult to package with long dropper posts, big wheels and steeper seat tube angles these days. But a clever way of getting a rearward axle path without too much chain growth. Think I demo'd a Klein Palomino with it once.

“ Anyone remember Monolink suspension?”

It’s part of that family of suspension which is designed to work well when you’re sitting but stiffen when you stand because the BB is on the suspension linkage not the frame. Not great for anyone who stands up to descend (which I’d hope is pretty much everyone now that dropper posts are the norm). Good if you stand to pedal but sit to descend but that seems the wrong way around.

So it is. That's suboptimal. Explains why no one uses it now. Couldn't remember if it was any good or not. I do remember trying a Trek Liquid at the same time and preferring that.

I had an Orange 5 and loved it for trail centre and natural trails but I felt I had to set up the suspension differently for each trail type. I found this quite annoying as I didn't like the feel of the set up in an in-between type set up. But then that's pretty much the same for all suspension just that I noticed it more on the 5.

Out of interest, is there shocks that change their rebound as well as their sag and compression on the fly? I'm still always fiddling with rebound on my full sus when out riding.

My have already been said above but the split pivot idea is a great system for a single pivot bike, assuming you're going beyond the simplest, direct swing arm to shock Marin/Orange layout. It can give all the things I like about how a single pivot feels under pedalling (if done well) with almost no braking influence on the suspension.
Having said that if you have as many pivots as a split pivot design you could just use a 4 bar and project the VPP into the right area to get a very similar feel through most of the pedalling part of the travel. 4 bars had a past rep for being very neutral and I wasn't a fan of that feel but it's designed in, not inherent to the design.

Brake squat and jack aside, the simple effect of braking on a single pivot is that the calliper clamping the rotor prevents wheel rotation (er, as it should) but as it's preventing rotation relative to the swing arm the suspension becomes less sensitive and the wheel is more likely to skip. Whether it's a real problem when riding is subjective but it happens, it's a similar effect to Chris Porter's points on clutch mechs but often more pronounced.
Braking can effect suspension on linkage bikes also - generally squat or softening I'd expect if there is any effect from brake link rotation but it's a long time since I looked at any of those linkage graph programmes.

I prefer simple, durable and effective-enough over greater performance via complexity so a SP Starling with a good shock and no more than 120mm travel would keep me happy.

Doesn’t it all depend on what you’re after from your bike. My reason for getting suspension in the first place was to take the sting out of riding after a back injury. I wasn’t ever bothered about axle paths or anything else. For that a single pivot works perfectly. It makes my bike more comfortable to ride. I also like the idea of fewer parts that you get with the design. Of course, I tend to ride on my own so I have little to compare it against but don’t care too much whether a ‘better’ design would make me more efficient or faster.

I do wish some more companies would bring out single pivot designs at a decent price. There is still a market for them and much as I would love something like a Starling it’s well out of my budget. Come on Alpkit!

Jerm - Have a look at Dartmoor bikes.

Though I just went with secondhand Orange frames.

Doesn’t it all depend on what you’re after from your bike. My reason for getting suspension in the first place was to take the sting out of riding after a back injury. I wasn’t ever bothered about axle paths or anything else.

If I can shave 5 seconds off my descent time, I can get back into the Strava top 100. Considering I've been spending 10 hours a week for the last year sneaking in at night with a shovel to realign the trail, spending 2K on the latest suspension design seems cheap.

I think the potentially fastest downhill suspension design would be a high pivot split pivot with idler. You’ve got a linkage to drive the shock to get a good leverage curve. You can have loads of anti-squat without kickback due to the idler. You’ve got a rearward axle path from the high pivot. And you’ve also got good brake-squat (60-80% appears to be a good compromise between maintaining geometry and keeping sensitivity under braking) unlike a high single pivot where brake-squat is really high.

And now Trek have done this on their new Session.

@jameso

but as it’s preventing rotation relative to the swing arm the suspension becomes less sensitive and the wheel is more likely to skip.

This is the bit I am unable to rationalise in terms of the mechanics. The braking force is a constant, so the torque it exerts on the swingarm is a constant. The braking force will therefore bias the suspension to a more compressed state when braking, but the spring rate will remain the same, so the rear suspension will continue to exhibit the same movement in response to a given force (at that point in its travel) as it would when not braking. It is not as if the effect compresses the suspension so far that you hit the bump stops, nowhere near that, it is a relatively small effect relative to the total travel.

It needs to be approached scientifically, that is measuring/observing what is actually going on, rather than starting from theory. High speed camera looking at the rear wheel sort of thing (though I am not excluding the social sciences from "science").

But as I don't have that data, my own ha'pennyworth of theory is that rear wheel locking (or at least slowing down) as you go over bumps may be an important factor. Wheel locking will impart a large slug of angular momentum to the bike. On a rigid bike, or a bike with no brake squat, that will be transferred to the whole frame, causing the front to dive and the rear to rise up*. In a "caliper attached to the swingarm" design, that will partly go to compressing the rear suspension. Then when the rear wheel makes contact with the ground again it might grip and spin up.

This is a recipe for all kinds of weird resonances taking place, which might well give the impression of the suspension not absorbing bumps correctly, but would be quite complex to model. Hence the need for data. But given all this, I am loathe to say "'brake jack' is a figment of peeps' imaginations", whilst also being sceptical as to their explanations of what it is and why they feel it more with single pivots.

*ETA which would explain why wheel locking is difficult to control and sometimes happens in an on-off-on kind of way. Once it starts, the rear wheel is unweighted so it locks even faster, then the wheel slams back down and grips again and so on.

^^ I have just remembered an example of this from my student days. I was cycling along on my Claud Butler 10 speed (2x5 not 1x!, this was 1978 or so) when an Ever Ready metal rear light fell out of my coat pocked and got jammed in the rear wheel (at least I think that was what happened). I almost went over the bars (not quite a full endo) and crashed into a tree. It was violent.

Just bought a 2020 orange stage 5 frame direct from Orange (one way to make it cheaper it seem). Can't wait to see what all the fuss is about!