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2015 Cannondale F-Si Carbon Race Hardtail Unveiled, Integrates Everything

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2015 Cannondale F-Si carbon fiber race hardtail mountain bike

When the Flash 29 debuted a couple years ago, it brought Cannondale’s System Integration (Si) to the frame with things like their OPI stem/steerer with Lefty fork and tuned SAVE seatstays. The all-new F-Si takes everything a step further by shifting the drivetrain off center, building a new Lefty, a new crank spider and adding a new SAVE seatpost to amplify the comfort of the micro suspension built into the frame.

The result, they say, is the fastest race bike because, rather than just thinking about the frame itself, it’s designed as a complete bike in mind. That’s also how Cannondale builds some of the lightest bikes out there, by creating some of their own components (Hollowgram cranks, Lefties, etc.) to ensure things work together smoothly and quickly.

So, what’s new?

2015 Cannondale F-Si carbon fiber race hardtail mountain bike

Starting with the whole frame, the geometry’s been changed to create a bike that’s simultaneously fast, stable and nimble. To get the “fast”, they shortened chainstays to a minuscule 429mm (16.88″), shorter by 15mm than before. To get the “stable and nimble”, they matched a slack 69.5º head angle with a 55mm offset Lefty fork. The head angle keeps things stable at speed while the short offset keeps handling snappy in the tight stuff.

These numbers work because a bigger offset decreases the fork’s trail, putting the tire/ground contact patch more in line with the steerer’s center line (click here for diagrams and better descriptions). The prior Lefty 29er was 45mm offset, and typical 29er forks are around 47mm.

2015 Cannondale F-Si carbon fiber race hardtail mountain bike

To get chainstays that short without compromising 2x compatibility and mud clearance, they had to shift the rear hub and drivetrain to the right by 6mm. That let them keep tire clearance on the inside of the chainstays and front derailleur clearance on the outside. If you notice, the front derailleur cage extends behind the front of the rear tire, so by keeping spaced off to the side, it let them bring the rear wheel up closer. This keeps rider weight over the rear tire for solid traction while climbing and super stiff power transfer.

cannondale-hollowgram-ai-sisl-crankset-2015

The new spider moves the chainrings out 6mm without affecting the spindle length or Q-factor. Out back, they had to move the hub 6mm right, also, which typically would shift the tire off the bike’s center line. To remedy this, Cannondale has the wheels built with zero dish, which brings the rim into center line without needing any proprietary parts. In the event you wanted to use your existing wheels, you’d probably need to have them redished or possibly rebuilt, but you could keep your existing hubs and rims.

All of this comes together in a complete bike package that they say is stiffer and lighter than bikes using a rear thru axle. Yep, that’s right, they’re sticking with quick release rear ends. It’s a race bike after all, so weight and quick wheel changes were of equal importance to stiffness and efficiency.

2015 Cannondale F-Si carbon fiber race hardtail mountain bike

The rest of the frame keeps their SAVE micro suspension seatstays and BallisTec carbon construction where it counts. Keeping with the race theme, they kept all cable routing external. This saves weight compared to an internal routing and makes team mechanics’ lives much easier. There is, however, internal wiring ports for electronic shifting systems.

Frame weight is claimed at 1,022 with all hardware (seat clamp, FD mount and cable guides). This is an externally validated, third party measurement. That said, they say they’ve weighed several models in house that have come in at 960g.

2015 Cannondale F-Si carbon fiber race hardtail mountain bike with new SAVE seatpost

Complementing the frame is an all-new SAVE seatpost. This version drops 47g while boosting compliance by 20%. The flex is also more linear, which they say helps keep it bending under lighter loads. In other words, it’s more sensitive and should be more comfortable.

2015 Cannondale F-Si carbon fiber race hardtail mountain bike with new Lefty Fork

For the Lefty’s, offset isn’t the only change. The uppers are 2mm larger, yielding a 44mm diameter top structure to make it stiffer. Inside, there’s an all new damper, similar to the SuperMax on the Jekyll. They say it needed an update to handle the more aggressive nature of World Cup XC courses. So, now it’s more supple and there’s more air volume.

More clamp widths are offered now (not just one), which means they fit each size frame specifically. For smaller bikes, that helps keep the front end low, and it all looks much better.

2015 CANNONDALE F-Si MODELS

2015_Cannondale-F-Si-CarbonBlack-hardtail-mountain-bike

At the top of the roost is the F-Si Carbon Black Inc., which gets Shimano’s new XTR Di2.

2015_Cannondale-F-Si-CarbonBlack-hardtail-mountain-bike with new XTR Di2 2015_Cannondale-F-Si-CarbonBlack-hardtail-mountain-bike with new XTR Di2

Full spec lists and sales sheets for all models are at bottom of post, just click to enlarge.

2015_Cannondale-F-Si-CarbonTeam-hardtail-mountain-bike

The F-Si Carbon Team model keeps the ENVE rims but moves to a SRAM 1×11 drivetrain.

2015_Cannondale-F-Si-Carbon1-hardtail-mountain-bike

The F-Si Carbon 1 gets custom drilled and laced Mavic Crossmax SL wheels…so this is your first look at the next generation Crossmax. Shhhhhhhh… Below this is the Carbon 2 model, shown on the sales sheets below.

SALES SHEETS

2015_Cannondale-F-Si-CarbonBlack-sales-sheet 2015_Cannondale-F-Si-CarbonTeam-sales-sheet

2015_Cannondale-F-Si-Carbon1-sales-sheet 2015_Cannondale-F-Si-Carbon2-sales-sheet

All models will be available in August, pricing TBA.

Cannondale.com

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65 Comments
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YoYoYo
YoYoYo
10 years ago

Slacker headtube on a 29er…the corners on our trails have become progressively wider way too much already since the 29er revolution…

django
django
10 years ago

– XTR di2 w/ FSA rings and a Cannondale crank.
– “Miniscule” chainstays that are almost 17″.
– 55mm offset proprietary fork.
– Wheel dishing nightmare of a back end.

god bless innovation.

dan
dan
10 years ago

Are the front wheels using the existing Lefty hub flange geometries, or are they using the new Lefty Supermax hub geometries?

jimmy
jimmy
10 years ago

they use the new SuperMax hub geos.

groghunter
groghunter
10 years ago

Not my cup o tea, but good on them for going with an asymetric rear triangle. I’ve appreciated that on every bike I’ve ever owned that had it. Blows my mind that it’s isn’t the standard. dishing sucks.

unsustainable
unsustainable
10 years ago

All of those proprietary parts- better buy replacement parts now and hope those parts will be available for 5years globally or is it a disposable race bike that you should never travel with? can you run a normal fork if you wanted too? what about replacement or upgrade wheels?

i
i
10 years ago

open QR… sure they can claim their frame is stiff, but it would be stiffer with a thru axle, and they repeat the easily disprovable idea that wheel changes are faster with a qr than something like a maxle.
look cannondale, the qr is 1940s road bike technology. It had a good run but there’s no place for them on a modern mtb.

AK
AK
10 years ago

I dig the new design/new features. The only thing that I am not stoked on is the new finish offerings. Why can’t they offer the public frames similar to what the pros are currently riding? Simple solid color with a contrasting single cannondale logo.

Either way I have my eye on that carbon 2

fleche1454
fleche1454
10 years ago

Is it me or am i missing the integrations part? I thought for years people had been tuning forks and components for racing mtb before Cannondale did this.

I have the same problem with these bikes that I had before they claim they made everything as one whole unit but all they really did is put all of the In house parts that they can onto their bike. Also Cannondale needs to get out of the stone age, we stopped living in caves and cooking everything with fire and we stopped using quick releases for disc brakes.

Sounds like moving the drive train to one side is a band-aid for not taking the time to make it the right way, which is simple to service.

JZ
JZ
10 years ago

So essentiallty Gary Fisher G2 geometry. Revolutionary. Sweet bike though.

Keyth
Keyth
10 years ago

For a bike that’s thesis seems to be total integration they seem to have sacrificed a lot to run a front derailiar that nobody wants (people buying this level of a bike are probable gonna run 1×11)
Offset wheels what a pain

Mark
Mark
10 years ago

Cannondale has been killing it this year. With their new 650b Jekyll/Trigger Bikes, Synapse and this bike. Now I just need 20k so I can buy one of each because I can’t want to go fast wether it’s Road, XC, or Enduro…

Jr
Jr
10 years ago

No thru axle out back? I’ll pass.

Peter Denk
Peter Denk
10 years ago

Hi everybody,
as me and my team did design the bike let me share some background infos.
Why a thruaxle is a bad idea for a XC hardtail ?
I love thruaxles on fullsuspension bikes. But unfortunatelly on diamondframe hardtails they are not adding stiffness to the rearend at all. This might be surprising but we tested that with multiple thruaxles and QR´s in our testlab very seriously.
That leads to following situation
A thruaxle adds weight
A thruaxle does NOT add any stiffness advantage on a hardtail (on a fully it can)
A thruaxle slows down wheelchanges
But we really hated the soft rearend feel of traditional 29er wheels.
So we came up with a solution to design the stiffest rearend AND the stiffest rearwheel c all 29er on the market.
So you, as the rider, get the best out of 2 worlds. The stiffness you need AND the simplicity and lightweight of a QR.
Happy trails
Peter

andy chatterton
8 years ago
Reply to  Peter Denk

perfect reply, I love my FSI and can’t wait to try my new Scalpel Si with through axel

wheel-addict
wheel-addict
10 years ago

Looks very nice except for the big fail of not using thru-axels on a mountain bike in 2014!

Big Cow
10 years ago

So they did all that engineering and build a f’d up offset drivetrain, all to get the stays to the same length that the Specialized Stumpjumper and Salsa El Mariachi have been for years.

Brilliant.

Andrew
Andrew
10 years ago

Looks like the masses have spoken, and not having a thru-axle is a deal breaker. Looks like someone in marketing should have put their foot down, and not caved in to the ‘logical reasoning’ of the engineering department.

Jr
Jr
10 years ago

Peter,

Thanks for the response. How exactly did you test or what method was used to determine it didn’t make a difference?

Also in regards to wheel changes a tubeless tire with sealant typically is more than enough to keep a racer going without the need to change a wheel unless they tear a tire to the point a new wheel or tire rather is needed. At this point they are likely walking their bike back to a neutral support zone completely taking them out of the race so how would 30 seconds maybe more make a difference here?

Thanks,

J

Slackboy
Slackboy
10 years ago

Jr, you’ll find that a lot of the racers are running the absolute minimum psi they can get away with in their race wheels, so any loss makes a difference. Also, 10-20 secs can mean a few placings, which means points, and points are what makes them tick

A thru axle rear vs QR doesn’t really make a difference for lil Xc boys/gals. I can notice a difference for myself, but I’m a big unit and a tad aggressive.

goridebikes
goridebikes
10 years ago

Beginning of post: we wanted to build a complete system.
Next 10 comments: WAH I CANT SWAP PARTS EASILY

Meanwhile, keyth delivers the best and only worthwhile comment…
In the age of XX1, WHY was the bike redesigned to accommodate a front derailleur that is OBSOLETE. The only reason for a front derailleur at this point is because you can’t bear to not use Shimano… and even then…

desertrat
desertrat
10 years ago

To those posting about why anyone would want to use a front derailleur anymore, perhaps you should all go read about Di2 XTR. Or the 11 spd XTR. Front derailleurs are going to be alive and kicking for quite some time.

greg
greg
10 years ago

not everyone lives where single ringing is viable. i, for one, dont agree w the single ring philosophy. neither does shimano, but theyll offer it for those who want it for now…

Zanetti
Zanetti
10 years ago

Hi Peter Denk , it was not possible to cdale innovate in a own system integration to rear wheel different of this trditional one ? its real bad to see a hi tech frame with that kind of prehistorical stuff , next one i was expecting a delta tube inspired on the synapse , i think the seat tube is the poor part on this frame less worked , and for last the save seatpost 2 is a copy of thomson elite seat tube , it seems you go on a choper ,ok i know that the bottom bracket is more in the back as a assimetric geometry …

MarkV
10 years ago

All of the design work to allow a front derailleur is answered on this very day, XTR Di2 just brought the FD straight out of the grave and back into allowing more useable gears for many of us. The design team had insight into the new release and acted accordingly. Di2 rocks for dirt!

Peter Denk’s response for the engineering of the 29″ rear wheel offset, offers up something to consider for the benefit of strength in an often fragile lightweight rear wheel. Good on you guys at Cannondale….now Mr. Denk, where’s the 27.5″ version with a tru-axle? Besides the dated QR (for disc) on your latest creation, I’m never running a Whagonwheel’er for someone my size, mid-size wheels for XC is the new lighter, faster shift in hardtailing fun and thinking.
Ok, let the wheel debate chaos begin!

Jr
Jr
10 years ago

Slack ok I kinda buy that…how ever if we flat or burp we are just going to hop off and put air in and finish the race…we won’t even need to take the wheel off the bike unless it’s a very serious issue in which case your points are down the tube any ways…I just don’t see it making an impact in a pro cat one race given the time already lost if it’s torn tire ect.

Pete
Pete
10 years ago

Interesting design and engineering philosophies involved with this frame. It was mentioned that chainstay length was shortened to 429mm and asymmetry to accommodate the front derailleur. Not sure if this was necessary as Specialized S-Works SJ runs 430mm chainstays in both 1x and 2x versions with no asymmetry.

willem430
willem430
10 years ago

I like the way cannondale takes the “sientific” approach and get they’re info from data they collect themselves. lets wait untill the test ride on the trail before jumping into conclusions…..

Ill definately make a test run on the black inc!

Gnate
Gnate
10 years ago

Peter Denk, please redesign the color scheme on the bikes. I do not want to look like more of a wanker than I already do while riding this. Curved green and white stripes? Looks terrible. Solid color of some sort with contrasting Cannondale logo much like the bikes Pete and Marc are riding in the promo vid.

Otherwise, I like what you’ve done with the place!

Matt
Matt
10 years ago

I think this bike looks awesome. Also, don’t see why everyone is in such a tizzy over the rear wheel – there is nothing bad about an offset DISHLESS rear wheel other than not being able to use it on another bike symmetric bike. One spoke length, even tension, and a stiffer wheel. If you watch the video of Peter Sagan killing it on this thing I doubt any of you could argue it’s not stiff enough. The geo makes it look like it’d be a decent trail bike, not just for XC racing. Also, there’s nothing on this bike that couldn’t be replaced with standard aftermarket parts, besides the front wheel with it’s lefty specific hub and the stem specific to leftys (even those parts have aftermarket options) – 1.5″ head tube, lots of headset options to run different forks and forks that run 1.5″ steerers; standard 135 rear hub, never ending options there, and lightweight; standard PF30 bottom bracket, again lots of options there to run whatever crank you want.

Liam
Liam
10 years ago

@gnate is right. As big fan of both Cannondale and Open Cycles, I’m thrilled with this. But while the engineering is classic Cannondale, the paint job looks like a Dorel Special. Too bad they didn’t stick with the prototype’s green.

Mike
Mike
10 years ago

I may buy one of these. I like it. Nice work Cannondale. Just please clean up the DI2 wiring.

Limba
Limba
10 years ago

Peter Denk is smarter than all of you combined. Cannondale has been kicking ass the last few years because of him. There, I feel better now.

I also prefer the simple all green color of the prototype bikes. Sagan had a wicked all green prototype Synapse last year that blew away the actual production bikes.

FrankR
FrankR
10 years ago

Why the people of Cdale cant say the truth: the reason why they make the bike whith cables still in the outside and quick release is not really performance is just for making cheaper and easier the large scale manufacturing process on Asia. The main upgrades on this bike you can really count on are allready out there years ago on bikes maked by brands that doesnt require factorys full of slave-work-force.

J Train
J Train
10 years ago

You guys are nuts. This bike is a breath of fresh air. Standards are shoved down our throats constantly by big manufacturers, yet a team of brilliant engineers is using hard data to design a bike without forcing us into anything. Dish-less wheels with wide bracing angles are bombproof. One spoke length, even tension all around? Sign me up. The new Lefty sounds awesome. And the built in compliance of this frame is going to make hardtails even harder to pass up for heavier, less efficient full sus’ers.

When’s the last time an engineer from a big manufacturer decided to go slumming on the BR comments section to answer questions for a bunch of anonymous chumps like us?

I would like to buy you a beer, Mr. Denk…in exchange for a carbon 2!

fleche1454
fleche1454
10 years ago

@limba
If they are so good why do I see more Cannondale warranties than anything else?

greg
greg
10 years ago

that seatpost and all like it: i really hate when the dowel that supports the bolt heads is allowed to slide fore/aft until one of the bolt heads is resting on the shaft. makes it very tough to access.

Joff
Joff
10 years ago

Cannondale dominates the industry with innovation that works. Put all marketing mumbo jumbo aside and just ride the bike. This bike is going to be a real game changer just like the 1st Flash 29 revolutionized the industry. Peter Denk and his team of engineers have and will continue to create the fastest bikes in the world. Who cares what your paint job looks like when your rockin’ the top step on the podium. It’s so funny to hear people tear something apart before they have even ridden it. Credibility comes from experience and all you haters out there need to ride this bike then you can give an honest assessment.

Ripnshread
Ripnshread
10 years ago

Nice bike but the new standard rear wheel is a bad idea. You will not be able to safely install a replacement wheel and just “redish” it 6mm to the non-drive side. Lightweight XC race wheels almost always use alloy nipples. These need to have the spoke threaded all the way through the nipple to hold up. If you want to install an older wheel or get a quick replacement you will be SOL. For the big pro teams with lots of wheels sitting in the box truck, no problem. For a privateer who just wanked his wheel on practice day…better hope that pro team is available and generous enough to let you borrow one, hope C-Dale has had the forethought to have replacements available to borrow at every race or….go home on Friday afternoon knowing your rare offset rear wheel just cost you your entrance fee and a fun weekend. Get ready to carry spares or ride like a crab with rubbing every time you switch to the granny or honk on those bars.

TLDR; New super rare standards are not a good idea for anyone who doesn’t have professional race support.

Doug
Doug
10 years ago

It is funny to read about the complaints for changing standards. When mountain bikes first arrived they were thirty pound steel bikes with horrible shifting and brakes that gave you little stopping and sore arms. If manufacturers didn’t innovate, that is where we would be today. People made fun of Cannondale for making aluminum frames, but look at the industry now. Same thing when Cannondale introduced disc brakes and the Lefty. I wouldn’t be surprised if more manufacturers adopt a symmetrical rear wheel. It’s stronger, stiffer, and just makes sense. Mavic has already come aboard.

Ripnshread
Ripnshread
10 years ago

Cannondale got made fun of for making aluminum bikes because they were crap aluminum bikes. They were all out of alignment and cracked all the time…thus the nickname “CreakandFail”. We still make fun of Lefty’s. Mavic made those wheels because they were paid to.

AK
AK
10 years ago

After reading more of their advertisements, the whole quick wheel change pitch seems more like a gimmick. While a catastrophic race ending flat is more likely to happen on the back, if you get a flat in the front with a lefty it is a serious pain to switch considering you need to unbolt the caliper. So if you flat in the back the qr lets you change it quick, but if you flat in the front you are in for a minute+ fix. Seems a bit unbalanced logistically.

Ilikeicedtea
Ilikeicedtea
10 years ago

@AK Why would one have to take the front wheel off to change a flat with a Lefty fork? Think about it.

AK
AK
10 years ago

@Ilikeicedtea I am assuming in a race you would go for a wheel change as opposed to trying to fix it.

chris
10 years ago

I’m with Doug/Joff/J Train on this, people are always so afraid of something new and invariably rip on something they didn’t come up with. A little scepticism about marketing speak etc. is fair enough but allot of the those posting here just come across as inverse snobs, i cant help but think that if Mr Denk was still at Scott and this was the new Scale (or whatever) the same posters would have very different, far more positive opinions. Still that’s just what they are I guess, opinions, we are all entitled to them etc. Personally I like the the look of this and am willing to believe the Peter Denk, a bike engineer of 20+ experience has some idea what he’s doing.

paul
paul
10 years ago

“We still make fun of Lefty’s”

Maybe you should ride one. Then swallow your pride and admit how good it is?

Joseph Clemenzi
10 years ago

comments suck. this designs looks pretty bitchin. +1 for a zero dish rear wheel!

can't have it both ways
can't have it both ways
10 years ago

“I want innovation for top performance, but I want all my parts to be swappable”
Wake up guys, this is cake and eat it too. How can a manufacturer outdo it’s competition in performance while endeavoring to maintain compatibility with off the shelf parts from a host of aftermarket vendors? At some point that breaks down. If you don’t like it, don’t buy it. Service universality and top performance for intended purpose are inherently at odds. Decide where you lie on that spectrum, and find the bike that works for you.

I applaud Cannondale for taking the risk in offset drivetrain — even if I work for a retailer and know that wheel swapping issues are sure to present problems with some sales. I’m shocked that so few in this forum have ignored how much wheel performance is degraded by vastly differing spoke tensions from drive to non-drive side inherent in modern 10 & 11 speed wheels — let alone what this does to spoke durability. Zero dish theoretically means a rear wheel that tracks with equal lateral rigidity when loaded left or right side. Maybe the reason so few are excited about this prospect is no one has ever experienced it!

Kudos also for the changes to Lefty — fit constraints in past Flashes with not being able to get bar low enough were fairly frequent, and differing clamp stance (and thus headtube heights) is a VERY welcome change!

Proprietary parts are nothing to fear as long as their merits are justified. I think Cannondale does a better job than some others at doing proprietary parts that achieve a significant advantage to the end user — not just a future of obligatory parts service business.

Rock on Peter & Co…

stefan
stefan
10 years ago

I think this bike is really a wrong concept For normal guys who will not run xc race in Always repeating laps but want to climb mountains and then live cool, real downhill. Not at least because of the very short chainstays of only 429 mm. On my (Cube) 29er I have got 440 mm, without any problems regarding reactivity and with real advantages in uphill and cool and stable, anyway reactive downhill.
But probably Cannondale thinks just for racers who change bike after 1race. This is also shown by the situation that a guy who went 420 km across the alps needed to carry his bike on the shoulders downhill on the last part, the most beautiful downhill of the whole adventure, because his Lefty had broken.
When I ran the same trip with my 1992 Stumpjumper I didn’t even have a Flat tire and now with my Rock Shox forks I never had any problem.
So I don’t think that Cannondale has a goog concept.

Timquila
Timquila
10 years ago

Peter Denk, thank you and your crew for your work at Cannondale. Great Bikes!

bielas
bielas
10 years ago

Great frame and ideas. So many of you have been brainwashed about the need of a thru-axle on a hardtail; a good QR and large interface between hub and dropouts is what’s needed.

However that seatpost is so 1994… the looks are terribly crude and the friendliness of use very bad for that front bolt. Cannondale needs better product designers

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