[Closed] Cannondale Lefty - advantages

We don't buy em for that, it just to wind the c'dale haters up, and get them frothing at the mouth, and to have kids tell us were missing a fork (my std reply "couldn't afford the other leg")

There are some maintenance things that are a bit more tricky than other forks, removing a wheel means unbolting the brake, and the proprietary hub design makes replacing wheels a little trickier, but there's plenty on the plus side to counter that.

Seems a perfectly legit demo - TBH I'm not all that surprised by what he's showing, though I'd have some suspicions that he picked a fork which was particularly flexy to compare with. The Lefty is actually a very good technical solution - something I've seriously considered getting to fit on a non-Cannondale bike.

In case it isn't clear I don't own one, so no bias from that perspective.

More wobblage for wonky wheels.

I've got a USE SUB fork on my bike - it completely messes with people's heads.

"How can it be strong enough only supporting the wheel on one side like that?"

"Go outside and look at your car wheels"

😀

[quote=bencooper ]"Go outside and look at your car wheels"

OMG, how do they not fall off 😯

I'm a qualified Mech Eng (CEng) and to me it makes perfect sense. It's a great design and the same basic principle is used on almost all modern cars i.e. McPherson Strut. I once designed a Rally Car suspension strut with linear roller bearings (like the latest Lefty uses) to reduce friction over standard bushings. Again it's a great idea. I can't fault it if I'm honest and I do believe it's inherently a better design than a conventional fork.

So why only Cannondale? No idea, but imagine it's the consumer marmite effect. Or do they have a patent?

[quote=moshimonster ]I'm a qualified Mech Eng (CEng)

Really? I don't think you've mentioned that before.

They've definitely got a patent on the Headshok system - a company I know was paying around £200 per frame to license it.

Really? I don't think you've mentioned that before.

**** off. It's definitely relevant. A bit like responding to a medical question if you are a doctor.

A quick google suggests it's just the needle bearing bit which is patented (well apparently also a cartridge damper, but the quote I found suggests they're not enforcing that). However that is kind of fundamental to the torsional stiffness and lack of stiction - hard to imagine how you'd make a single sided front suspension which works so well without using that.

@moshi - it's argument from authority. If you know what you're talking about (which clearly you do) then it should be possible to make your case without having to resort to that.

@moshi - it's argument from authority. If you know what you're talking about (which clearly you do) then it should be possible to make your case without having to resort to that.

Bullshit. What's wrong with just stating your profession if it's relevant to the discussion? I'm sure the OP would like to know the opinion of someone qualified as a mechanical engineer. If this is not mechanical engineering, I don't know what is?

However that is kind of fundamental to the torsional stiffness and lack of stiction - hard to imagine how you'd make a single sided front suspension which works so well without using that.

It's a good feature, but not really fundamental to the strut design. How many cars have needle roller bearing struts? Virtually none, in fact the only one I know is the Rally Car version I designed. I think it's only been used on the Lefty quite recently.

I have a degree in Astrophysics. This is happening in the universe. Therefore I'm qualified to comment 😉

hard to imagine how you'd make a single sided front suspension which works so well without using that.

USE did it with an angled linkage - has the additional benefit that it produces anti-dive geometry.

I do believe it's inherently a better design than a conventional fork.

Until you have to strip it down post a normal UK winter. That was the major disadvantage I remember, it needed TLC from a shop. That and a restricted choice of front hub. I think the USE Sub was home serviceable though, surprised that didn't catch on more - think it would take RockShox or Fox to make one for it to gain acceptance.

That was the major disadvantage I remember, it needed TLC from a shop.

Maybe true I don't know, but it's not an inherent disadvantage of the actual design concept. That would be more down to the detail design i.e. sealing etc.

I think the USE Sub was home serviceable though, surprised that didn't catch on more

Very easy to strip and service. There were two problems - it was expensive (around £750 I think), and USE didn't make the air cartridge themselves so they were in trouble when they couldn't get the cartridges any more.

"That was the major disadvantage I remember, it needed TLC from a shop. "

Unlike say ermmmm i'm trying to think of a large fork manufacturer thats had say .....24hr strip and service intervals...... what's their name....stout....badger......weasal! thats it weasal, isn't it?

I've got a O level in Art say i can say they look nice.

A lefty is a brilliant way of eliminating claggy mud clinging to your fork arch.

Other than that, I'm stumped...half the leg count of a normal fork, but for double the cost.

half the leg count of a normal fork, but for double the cost.

It's not just half a conventional fork leg though. It's very well engineered actually, especially the latest Supermax version. I would have bought a Cannondale Jekyll just for this fork except they are sold out in the UK.

I loved my Lefty when I had one but the maintenance was a bit much.

Unlike say ermmmm i'm trying to think of a large fork manufacturer thats had say .....24hr strip and service intervals...... what's their name....stout....badger......weasal! thats it weasal, isn't it?

That's the same weasel words on every manufacturers instructions - essentially you can't ride any fork more than once without a rebuild if you follow the letter of the law.. at least with say Rebas I can take them apart and have fighting chance of getting them back together in a better state, I couldn't have done that with a Lefty. I also remember riding with a guy on an event who was bitching about the ELO, when this was a new thing.. kept switching on and off without consulting him.
I'd have had one, but my nearest dealer was too far away for the servicing.

[quote=moshimonster ]It's a good feature, but not really fundamental to the strut design. How many cars have needle roller bearing struts? Virtually none, in fact the only one I know is the Rally Car version I designed.

Cars tend to have other linkages controlling wheel movement, which is usually fairly straightforward to do given location of wheels relative to the chassis, and also necessary for stuff like steering - [b]Mac[/b]Pherson struts are after all most commonly used on front suspension.

More tricky to have other controlling linkages on the front suspension of a bike - clearly USE found a way to do it, but I'm not convinced it's as good as having a single strut which inherently resists torsion.

I give you that without stating any qualifications whatsoever.

The [url= http://www.pinkbike.com/news/cannondale-jekyll-275-carbon-team-review-2014.html ]Jekyll review[/url] on PinkBike gives an interesting review, I'd love to try one but the cost to me is crazy.

One thing I'm not sure of is how Cannondale make a single sided inverted 'fork' which is reportedly as stiff as a very stiff thing but dual sided UD forks are constantly criticised for lack of stiffness. Is it the needle roller bearings that make the difference? Could Dale make a dual sided Lefty for DH?

MacPherson struts

Been googling again?

I give you that without stating any qualifications whatsoever.

You have one large chip off your shoulder.

Oh you guys

That was the major disadvantage I remember, it needed TLC from a shop

Odd, I've found over the years they require a lot less attention, I've still got a 2000 DLR in regular use and it's only had 3 damper services in that time and a bit of lube, still runs perfectly.

The only un-reliable one I've had was a Max with a manitou damper, and all the hassle was from the damper rather than the chassis.

As long as the boot is intact (older models) then they are remarkably well sealed, and dirt doesn't migrate upwards very easily so if there is any corrosion on the races its normally right at the bottom of the leg, which never actually contacts any of the rollers, even at full compression.

Tony @Thumbrrint has been running a boot-less (as an experiment) lefty on his CX bike for several years, and although the bottom of the races look awful now functionally it's still perfect.

The dampers are no more or less complex than in normal forks so there's no additional maintenance there and the days of needing a special tool to do bearing resets disappeared a decade ago.

I've not used any of the newer models where they replaced the boot with a seal and made the lower-most section round to do so, but have seen isolated reports of these suffering form a bit more wear and tear.

[quote=chillidave ]One thing I'm not sure of is how Cannondale make a single sided inverted 'fork' which is reportedly as stiff as a very stiff thing but dual sided UD forks are constantly criticised for lack of stiffness. Is it the needle roller bearings that make the difference? Could Dale make a dual sided Lefty for DH?

It's one of the things - they're what allow the Lefty to resist torsion. As stated in that video fork legs tend to be round and have no resistance to torsion, so torsional stiffness relies upon bracing between the legs and with an UD fork you only have one point of bracing. You also have fore-aft and sideways stiffness - UD forks should be relatively good at the former as the bushings are low down away from the highest torque loading, the latter has the same issue as torsion in that they have one brace less to resist independent leg motion. A Lefty also has relatively large diameter tubing which results in better stiffness than two smaller diameter tubes - the one potential point of weakness is the axle cantilevering, but clearly they've beefed this up sufficiently.

They did once make a dual sided fork using the same technology as their headshocks before Leftys existed - though I'm not sure if those had needle bearings.

I was impressed by that video when I first saw it.

It makes me wonder why making an acceptably stiff single crown upside-down fork can be so difficult if Cannondale managed to make this spectacular thing over 10 years ago.

(edit: someone managed to answer my question in the post above before I'd even asked it... amazing!)

One thing I'm not sure of is how Cannondale make a single sided inverted 'fork' which is reportedly as stiff as a very stiff thing but dual sided UD forks are constantly criticised for lack of stiffness. Is it the needle roller bearings that make the difference? Could Dale make a dual sided Lefty for DH?

Very good questions. Yes I think the bearings help, but more importantly the square section resists torsion.
They could make it dual sided, but then it would be heavy. Dale obviously decided long ago that the stiffness/weight ratio was optimal with a single leg.

[quote=smatkins1 ]It makes me wonder why making an acceptably stiff single crown upside-down fork can be so difficult if Cannondale managed to make this spectacular thing over 10 years ago.

As pointed out in the video, and I just mentioned, the issue is that an UD fork has round tubes which don't resist torsion, so you're relying on the bolted axle to do that. That and for the same weight a single tube can be made stiffer than two by increasing the diameter.

Of course you could put needle bearings in a UD fork, but you'd need two sets, increasing weight, and Cannondale's lawyers would get you.

I quite like the Lefty and would love an updated version of the USE Sub.

What always amused me was the launch blurb for the "new" Lefty a couple of years ago. Basically:- "look at our great new fork, with these solutions to the problems we always kept quiet about for the last 12 years of production (complete like lack of sealing, needle bearings migrating out of synch etc)"

http://singletrackworld.com/wp-content/uploads/2012/06/cannondale-2013-new-lefty-fork/

[quote=moshimonster ]Yes I think the bearings help, but more importantly the square section resists torsion.

It's a combination of the two - you can't really have one without the other.

I also want to click "like" on mick's post above.

the one potential point of weakness is the axle cantilevering, but clearly they've beefed this up sufficiently.

Agree with your post, but I don't think the single shear axle is an inherent weakness. It might look like one, but it isn't. No different from any car stub axle.

I've never seen a one legged rigid "fork" I wonder why?

Weakness was the wrong word - it's a point where you could potentially get flex, as it's tricky to make the diameters large given the requirement to fit bearings for a hub.

[quote=cheese@4p ]I've never seen a one legged rigid "fork" I wonder why?

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It's a combination of the two - you can't really have one without the other.

Of course you can. Nothing to stop you using plain linear bearings instead of needle rollers or linear recirculating ball bearings. Not saying it would be better mind, but they are separate design features.

(complete like lack of sealing, needle bearings migrating out of synch etc)"

A big rubber belows dosent count as a seal? the bearing migration was so well hiden by cannondale it has a page in the owners manual on how to reset the bearings.

needle bearings migrating out of synch

This was one of the major problems with our Rally Car struts as it happens.

They could make it dual sided, but then it would be heavy. Dale obviously decided long ago that the stiffness/weight ratio was optimal with a single leg.

The original Cannondale Moto's were just that.

The lefty came after as a development of that because they realised they could build it single sided with sufficient strength and stiffness and save a massive chunk of weight. it also had the added benefit of allowing them to side-step the packaging constraints of building HeadShok's with any more than 80mm of travel.

cheese@4p » I've never seen a one legged rigid "fork" I wonder why?

There's also rigid lefty single crown available on some Cannondales, and a Spanish (?) company making a CF dual crown rigid lefty compatible with Cannondale hubs, Black Cat I think...

needle bearings migrating out of synch etc

Not only is it a 5 min procedure that is documented and easy to do, but the more recent Lefty's auto-reset on bottom out so it's pretty much a non-issue now.

[img] [/img]

[img] [/img]

[img] [/img]

Weakness was the wrong word - it's a point where you could potentially get flex, as it's tricky to make the diameters large given the requirement to fit bearings for a hub.

It's okay though, the bending load is very small. It's almost pure shear load so very easy to design strong enough to resist. Ever heard of one flexing or snapping off? I'll let you Google it for me 😉