Sam's Modified Norco DH Bike - New Zealand Nationals

Jan 11, 2016 at 17:51
by Mike Levy  
Sam Blenkinsop s modified Aurum.


Blenkinsop's Modified Norco Aurum

We usually see the most interesting bikes, components, and modifications during the World Cup season, but that doesn't mean that teams have taken the winter off from tinkering with anything that might allow riders to go down the hill quicker. Photographer Cameron Mackenzie spotted Norco's Sam Blenkinsop running this interesting looking idler pulley and chain guide setup on his Norco Aurum, presumably to change the amount of anti-squat that's built into the Aurum's 200mm of A.R.T. suspension design.

In the Aurum's stock form (shown in the photo of Sam's 2015 race bike to the right), the bike's main pivot looks to be just slightly above the top of the chain ring, depending on the size of the ring. But the custom idler pulley on Sam's bike routes the chain well above the main pivot, a modification that would make the bike have less anti-squat and, therefore, allow the suspension to be more active while Sam is pedalling hard.

The tradeoff is possibly less pedalling efficiency, but they may not matter to Sam if the bike pedals well regardless of the change, or if the track puts much more of an emphasis on bump absorption than all-out sprinting speed.
no idler to reduce drag and for better small bump performance. With it installed the clutch of the read derailleur had too much effect on the suspension for Blenki
Sam was using a much more conventional setup during the 2015 World Cup season.

The setup on Sam's bike is clearly a homemade device, with the upper unit being from MRP's AMg chain guide and a pulley wheel that's held in place with a large bolt and some washers. Note that not only is the upper guide adjustable height-wise, but there appears to be another mounting hole for the pulley wheel that's considerably lower than where it's located in this photo. All of this looks like it's attached to a fin of aluminium that's been welded onto the chain stay. Owen Pemberton, Norco's Senior Design Engineer, had this to say when questioned about Sam's bike: ''What you are looking at is just a part of our ongoing Norco Race Development program. That setup on Sam’s bike is purely an information gathering exercise at this time.''

Title photo Cameron Mackenzie
Inset photo Dave Trumpore


149 Comments

  • + 166
 Maybe after seeing so many idler pulleys lately people will stop judging the Canfield Jedi so hard.
  • + 59
 Riding a Jedi defiantly alleviates any doubt.....Amazing.
  • + 3
 right?
  • + 25
 Simple physics justifies the use of an idler pulley on any bike with a lot of chaingrowth. Without it the chain is fighting against your suspension. I'm working on a similar setup for my Banshee Legend Wink
  • + 8
 Also, I know from experience that with this sort of setup, the tab that that pulley is mounted on experiences a TON of stress under hard bottom-outs and hard pedaling. Looks like they have a pretty solid setup, but I can still see Sam managing to bend it.
  • + 5
 pretty sure they do get a ton of force...my K9 had an idler and lots of engineering nerds were always checking out how solid the idler was. I thought the Aurum was pretty active anyway, would be super active like that sheesh!
  • + 11
 @EarthEater same thought I had, Canfield has been doing it for so many years now, and it REALLY REALLY works, especially in the Jedi's case with the super radical rearward axle path, insane geometry!
  • + 8
 GT's Idrive and new aos system have always had close to zero chain growth= chain never fights suspension = smooth rideSmile
  • + 3
 I had a setup like this rigged up off of the back plate of an Ethirteen chainguide, and it took very little weight on the pedal to start to bend the crap out of the backplate. Needless to say, I ditched that setup for the sake of my brand new chainguide haha
  • + 47
 all this talk of riding jedi's make me think of Rey lol
  • + 13
 The anti-squat is strong with this one
  • + 10
 Balfa BB7 was the first my friends.
  • + 0
 K9 wasn't too far behind the BB7 either.
  • - 2
 I wish K9 would make a 27.5 version, nothing comes close to the DH001s on proper terrain but I refuse to invest in a wheel size that is dying out.
  • + 4
 Jedi is a fantastic bike.
  • + 4
 The Jedi is one of my dream bikes....couldn't find one used in europe though Frown but that rearward suspension curve....bikeporn
  • + 1
 " that looks like a commencal V4 ! "
  • + 2
 @Bruccio, I tried to sell two of them last year. There is sometime some Jedis to sell in France. But I think when you ride one you don't want to sell it if you are still able to ride.
  • + 1
 yeah i found one on jan 2014 here in germany where i live...450 km away. the Intense M9 i bought instead was 30 km away and in better conditions imho. still, i would love to tryout a canfield bike
  • + 2
 interesting that the idler moves during suspension travel. That makes working out exactly what effect it has on the drivetrain waaaay more complicated. Wonder if they put it there for a reason, or if attaching it to the swingarm was simply easier than attaching it to a fixed point on the front triangle.
  • + 1
 @Bruccio they are often sold at Bikemarket.
  • + 1
 @bonkywonky bikemarkt? on mtb-news.de? that's where i found both the far away jedi and the much closer M9 bro Wink
  • + 1
 To me it looks like this constructions purpose is mainly to free the suspension as far as possible from the chain. Last summer sam was riding a derailleur without clutch to avoid influences on the ssuspension. In my opinion this this pulley not only decreases the antisquat effect, which isnt needed on dh at all, but also decreases the pedal kick back, because when the rear wheel lifts up, the chainstays lift up, and the pulley goes down through its radius around the main bearing. Therefor it lengthens the chain a bit. With this configuration he should be able to ride a clutch derailleur
  • + 2
 If the topside of the chain does get shorter throughout the travel, this will add pedal squat. How much tho is hard to say.
  • + 1
 He should follow Aaron gwin and skip the chain altogether
  • + 2
 Canfield Jedi's Are The Bomb!
  • - 3
 Jedi's haven't won any races have they? As far as I can tell they only win chainless races at bootleg, lost in the pro, moved down to cat 1 and lost, then moved to cat 2 and won at silver mt........ hummmmm maybe they should just run chainless....
  • + 2
 Do the bikes race themselves? Must be their fault.
  • - 3
 No... but those results are lance canfields.......says a lot of say....
  • + 1
 Would you expect the engineer/designer/owner of Specialized to be race winners?
  • + 1
 @idafreerida all that says to me is Lance must be so dedicated and serious about his work that he spends much time working to ensure We the consumers get his best works.
  • + 2
 For one canfield isn't a massive company, and having lance test the bikes, does say a lot as @EastCoastDHer has stated.
Also I don't see the owners of any of the big companies actually racing the bike's. as far as I know anyone who has ridden one has loved it and if they sold it they regretted it. lots of companies are following canfields footsteps with the idler pulley, so it obviously means something
  • + 1
 Finally have my idler pulley setup on my banshee legend up and running. There's some pics and a video of it on my page if anyone is interested
  • + 28
 He mentioned wanting to do this last summer. Rad to see Norco giving his feedback a real world test.
  • + 4
 yeah for sure, testing to see what works is interesting
  • - 2
 I can see this being a new trend if it's able to fit on most frames. Great for single pivot bikes.
  • + 4
 I don't think you'd use it for single pivot. The martin benefit is where you have rearward travel isn't it?
  • + 11
 You'd use it on a high single pivot.
  • + 1
 Can use it anywhere there's a large amount of chain growth. looks like they've welded the top guide onto the swing arm which is a commitment at any stretch, might be a good way to go considering you could tune some squat out with compression damping.
  • + 2
 @src248 exactly, much like the original Trek Diesel which ran a similar system.
  • + 21
 I call out BS, the reason for that extra pulley, has nothing to do with pedaling. The only reason for it to be there is to reduce pedal kickback. I.e., someone mentioned a jedi, if the jedi had no pulley and u were riding with a 32T chainring, if you were to go fast through a rock garden or landed off a big drop at speed, your feet would get catapulted off the pedals, if you are on flats, or would get extreme feet turbulence if clipped in.

The only way to aleaveate pedal kick back, is by adding an extra pulley, like Sam did, because he rides at WC speeds, and most of the time on flats. And ride with a larger chainring. Considering every bike design is different, each bike has different amount of pedal feedback. Adding a pulley is usually for bikes that have the most pedal kick back in the market. If yours has only a little bit of pedal kick back, you can take care of it with a 36+ chainring.

For the banshee legend guy, all u need to so is use a 36 or 38t chainring and the pedal feedback would completely dissapear. I can almost bet u are using a 34t arent you?

So what this article tells us is that at WC speeds, the Aurum has too much pedal kickback to be a competitive bike for the podium. Hence the moddification.
  • + 8
 You're right that it has nothing to do with pedaling. My Jedi climbs just fine but the idler has nothing to do with it. The idler is simply to compensate for the drivetrain growth which would happen during travel stroke. If the idler was not there, you would not feel any "kickback" on the pedals but the drivetrain would explode because of the growth in distance between the bottom bracket and the rear axle.
  • + 3
 You're both wrong. It as a lot to do with pedaling and less to do with kickback.
It has to to with pedaling because placing the point of tension force higher on the frame means there is a greater "up" horizontal force acting on the rear casset, rather than it pulling it down when its trying to work up. Very similar if you have ever ridden a two chainring setup. Having the chain in the smaller ring makes the world of a difference and you can feel it keeping the rear end in place, but having it in the bigger ring (greater horizontal force up) and the bike bobs up and down more since the suspension is more active.

Give it a try then argue
  • + 3
 Nobody's arguing. I ride Jedi's and I used to ride Balfa. It's genius.
  • - 3
 @n4st - Completely and utterly the wrong way round, you are wrong, they are right.

Don't argue, listen and learn.
  • - 1
 Its been done to make the bike pedal better over rough terrain. Which we all know Sam loves to do.
  • + 2
 Every Norco I have ridden has terrible kickback, so I hope that whatever it does it eliminates kickback as well.
  • + 4
 The idler is absolutely mandatory on bikes with that much chain growth through suspension travel. There is no derailer on the planet with a long enough arm to allow for that much chain growth. Thus the idler is mandatory on a Jedi purely for chain growth reasons. There are also design goals and tradeoffs involving pedal feedback and pedal bob. Those concepts were considered along with chain growth and idler concerns during the design process. From the outside it is impossible to say which factors drove the design and which were requirements of that chosen design. In my opinion, they wanted a rearward axle path. That resulted in chain growth and thus an idler pulley was mandatory.
  • + 4
 What dfiler said.

Also, Levy, can we stop talking about the location of the main pivot in relation to the chainring for multi-link setups? sure on an FSR it may have slightly more relevancy than on a short link set up but still, the virtual pivot/IC is the real issue and the main pivot location is only one small part of that.
  • + 2
 "Anti-squat" leads to pedal feedback. They're both related to chain growth, which stems from axle path and suspension design. Adding an idler pulley allows them to alter the amount of chain growth (and thereby pedal feedback and anti-squat characteristics) without changing the linkage design.

You're arguing for the point here, not against it.
  • + 1
 When you have more chain-induced anti-squat, you get more chain growth as suspension compresses. This means that when you're applying power, you're increasing the spring rate, since your legs are applying an extending force on the rear suspension. Under power, a bike with lots of chain induced anti-squat will both stiffen and give more annoying pedal kick-back. That said, with too little anti-squat, the bike will sag under power and feel heavy and slow.
  • + 19
 The Canfield JEDI is hands down the safest DH bike on the planet! I call it my, "rolling insurance policy"! It just screams confidence. This frame designs allows you to push thru rough terrain like its the groomers. The wheel loves to stick and "read" the terrain. The rear-ward axle path combined with the killer geo (sub 17'' chainstays) lets it rip tight corners and actually ACCELERATE out of them. The JEDI also allows for shorting or over-shooting jumps without penalty. If jumping scares you, the JEDI will help pick up A LOT of slack. I can't count the number of times this bike saves me yearly.......And I am on my 6th JEDI this year!!! 2 thousand and sick-teen is here!

The BIGGEST negative of the JEDI.......It shrinks your local mountains and constantly requires you to be on the move for bigger hills!
  • + 6
 Viva La Jedi!
  • + 7
 Why have you gone through 6 jedi frames in a year? That doesn't sound like a positive
  • + 11
 hahah, good point....... 6th consecutive year on the JEDI frame is what I meant to say. Its evolved quite a bit over the years.
  • + 3
 BRAPPPPPPPPPPPPPPPPPPPPP
  • + 2
 Bring back The One!
  • + 3
 Love my Jedi! It's 6 years old but still seems modern. Most other 6 year old bikes look primitive.
  • + 1
 Sold my Jedi after just a few months. I do not agree with the above mentioned comments/opinions. The chain would constantly get thrown or tangled in the pulley system. I contacted Canfield Bros, who does have phenomenal customer service by the way, but they were never able to provide a resolution. I thought that maybe the pulley wasn't centered with my chainring and BB, but all the washers (spacers) were installed as directed by Canfield. I have owned a Trek Session, Knolly Podium and Transition TR450... all of which have been more enjoyable than the Jedi.
  • + 2
 Idk i have once thrown my chain once at all so i cant agree with you. i know many other people that own jedis and they havent had that issue either.
  • + 3
 Plus the Jedi comes with MES technology!! Matte Energy System
  • + 1
 I rode with a group and there were at least SEVEN Jedi's in the lineup. I never heard of any single one of us ever throwing a chain.
  • + 1
 Been riding my 2011 Jedi since it was new... zero trouble with the chain.
  • + 16
 I love my Canfield it's one of the best bikes I've ever ridden and I love the rearward travel!!!!
  • + 14
 I second that emotion. Never ridden a bike that accelerates on landings and in the rough like the Jedi
  • + 21
 Yup. The Jedi, slows not over bumps.
  • + 16
 Makers of the best bikes they are. To lead instead of follow, Canfield does.
  • - 6
flag DirtyHal (Jan 11, 2016 at 20:55) (Below Threshold)
 That's cool, this article is about a Norco R&D Bike.
  • + 3
 @dylandoe Because it is using the force!
  • + 4
 @CanfieldBrothers the jedi getting some love on a norco article lol
  • + 12
 Based on this, we should bring back the BB7
  • + 5
 And the Redalp?
  • + 3
 #Itneverleft
  • + 1
 psh all the cool kids are running paul klampers or trp spykes nowadays.

what were we talkin about?
  • + 4
 I still have mine. The BB7 stomps the trails. It's not a light race steed, but it SHREDS and it's a blast.
  • + 11
 CARBON JEDI please
  • + 2
 I don't know. I like the stability of having some weight below me, and my 39 pound aluminum Jedi shreds just fine.
  • + 2
 Please no. This was the one year I swore I wasn't going to buy a bike and spend that money on a kitchen renovation instead. A carbon Jedi means no new kitchen.
  • + 3
 Dont think it has anything to do with pedaling. It decrease the chain growth so the drivetrain affect suspension less. He has not run full chainguide last year and he said it is because there is less influence from drivetrain into suspension. This is just another step in that direction.
  • + 4
 I would like to see a bike that has a rear pivot about chest height. The frame would kind of look like it had a built in sissy bar. I'll get working on it,
  • + 6
 That pulley makes me want a jedi
  • + 3
 So in other words every bike that has it's chain below main pivot is has unbelieveably anti-squat. And to reduce that, he modified his bike so the bike chain is on top of the main pivot. CMIIW. Challenge accepted.
  • + 1
 Pretty much.
  • + 1
 In the 90s Horst Leitner produced the AMP Link for motorcycles that was exactly that. It really just isolated the rear suspension from engine torque. More popular with quads than with motos but it worked. Look at an ATK motorcycle (Horst designed) from those days and you'll see that the chain is parallel top and bottom.
  • + 1
 Good ole 406 with the rear brake on the countershaft sprocket! Idea was OK but not a game changer and there was always something broke on it.
  • + 2
 yep as others have said been done on other bikes with lots of chain growth...my empire ap1 has one and yep the commencal v4 and the older bikes mentioned above. Works really well on single pivot setups.
  • + 1
 i don't see a point if there is no high pivot going on. there must be quite a bit of stress on the pully tho, maybe it makes the harder gears more easy to crank but more rotations to crank it.
  • + 1
 The idler pulley gave me nothing but problems on my Corsair Marquee and I'm not pro enough to notice the difference. This looks like a better adaptation of the idea than my bike though!
  • + 3
 And so gizmo will be reborn soon with the "Mr Dirt"...
  • + 4
 What is old is new again
  • + 1
 I'm pretty sure I saw Kyle Strait running something similar on a picture he posted on Instagram a couple days ago. Interesting.
  • + 7
 The supreme v4 does do something similar, the chain runs above the swingarm
  • + 8
 It a concept as old as the hills: Balfa BB7 or Trek Diesel for starters..
  • + 6
 My BB7 and my Jedi are both rearward travel paths. They don't slow down over bumps.
  • + 11
 @dylandoe it would have been better if it was BB8 and the Jedi. I'll see myself out, now...
  • + 0
 The "7" in "BB7" refers to the distance between the bottom bracket and the pivot. The travel is 9" if that's what you were hoping for.
  • + 6
 Clearly, you missed the reference
  • + 1
 @dylandoe force awakens anyone? Wink
  • + 1
 Haha I haven't seen it yet.
  • + 1
 The whole time I was wondering what is so special and then I noticed it is not a Comma, rather a Norco. Interesting idea. If it works, it works Smile
  • + 3
 How will this effect Blenki's pedalling efficiency while in the air?
  • - 1
 All this does is make the rear suspension stay more active when you use the rear brake. A true Horst link does the same job. As in the rear chain stay pivot needs to be well below the chain line. Im guessing the chain stays stretch a bit during compression. just like a vpp of maestro suspension.
  • + 3
 seems something like the Commencal V4 frame..
  • + 7
 and Commencal have just reverted to what Nico was doing 16 years ago on his VProcess NV00 www.pinkbike.com/photo/8550408
  • + 4
 The chainslap is real...
  • + 2
 I was wondering when someone was gonna say something about fuckin noisy chains, if you think about the caliber of rider Sam is the imagine all the pro level maintained bikes he has ridden that don't make a peep of noise and make him happy to shred in peace and quiet. I go nuts when I hear any noise on my bikes especially chain slap.
  • + 2
 I like loud hubs, but otherwise GTFO! Right now I'm dealing with a mech cable banging against the spokes. Totally blows it...
  • + 1
 Cool idea. Keep it floaty while pedalling for a more planted back end or is this an advantage even when not pedalling?
  • + 2
 it's probably to reduce pedal kickback
  • + 1
 Slightly unrelated.. But all of this Jedi talk reminds me how much I LOVE my Riot.. DH bike in an all day anywhere package..
  • + 1
 Need More Pulleys why buying one chain when you can buy 2 for the Canfield Jedi Ohhh I'm judging .
  • + 1
 A Jedi only needs one chain, it usually uses a 111 to 112 link, chains come with 114.
  • + 3
 buy jedi!
  • + 1
 Damn I wanted to do that on my bike. So sick. I always thought the aurum had really high anti squat and pedal kickback.
  • + 1
 Looks like the Commencal Supreme thing with the chain going upwards.
  • + 1
 Or just be Gwin and ride chainless
  • + 1
 that extra wheel is just another expendable part, am I right?
  • + 0
 Wouldn't this do the opposite of what the article claims and decrease squat/increase pedaling efficiency?
  • + 1
 squat is pedaling efficiency. at the expense of suspension suppleness.
It all depends on where the virtual pivot is. If idler is higher it will cause squat as the chain can pull the rear wheel up, if idler(or chain line) is lower, it'll increase pedaling induced anti squat.by pulling the wheel down.
It's also probably travel dependent as the VPP will move through the travel.
and not sure if idler is mounted to swing arm, this also would have some effect, but probably very little due to it's location to pivot.
  • + 0
 I love articles like this. It's similar to car magazines showing spy photos of unreleased of updated vehicles.
  • + 7
 it's way cooler than that!
  • + 1
 why is he not using a direct mount chainring?
  • + 0
 why should he?
  • + 0
 I am wondering this as well. DM ring is lighter than spider+bolts+ring, and you don't have to deal with/worry about chainring bolts. Why would a pro racer run old tech?
  • + 1
 Haha! Old tech....

Ever tried doing a "quick chainring swap" with a dm ring?
Some of those dm rings don't look the stiffest either...
  • + 1
 Maybe he changes often his chainring so being able to change chainring without removing the crank is important for him?
  • + 2
 I am thinking that he's on a 38T ring and DM only come in sizes: 26, 28, 30, 32, 34, 36
  • + 1
 38t, that makes sense.
@gabriel, no I have never needed to do a quick chainring swap, but I can't imagine it being more simple than unbolt 8mm to remove crank, then use a bb tool to remove chainring. Two bolts. Less than the 4 needed for standard chainring. You ever try to do quick ring swap with seized chainring bolts?
  • + 1
 yeah that ring looks more like a cx narrow wide, its making my bike really insecure about its 28t
  • + 2
 Because I have grease at my disposal, my chainring bolts dont sieze. Removing a crankarm will never be as quick/simple as undoing for properly cared for chainring bolts. Also repeatedly removing an arm doesnt do your axle interface any good. DM chainrings are little more than pointless bling.
  • + 1
 Your telling me that you remove your chainring without removing your crank?
  • + 1
 Yeah.... are you telling me you think I shouldn't?
  • + 1
 I would bet it takes the same time if not quicker to change a DM ring. DM is lighter than the setup pictured above, and in the event the ring takes an impact, the carbon tabs will not be affected (how I broke my last carbon cranks). I always had to use loctite on chainring bolts or else they would wander out, which sometimes made for difficult removal. Race Face axle interface is fine, not going to wear it out. Removing drive side arm provides a good opportunity to inspect the inside of carbon crank arm for damage, as well as the hidden BB area of the frame.
  • + 1
 I am a bike mechanic. It is quicker to undo 4 chainring bolts and pop a new ring on than it is removing the whole arm. I know this from experience.

Yes RaceFace's arm/axle interface is subject to wear. Infact as a pressfit item, it is extremely susceptible to wear through excessive fitting/removal. I have had many Raceface cranksts. They get noticably easier to fit and remove each time. After maybe 20 times, they are no longer "tight" and I would say essentially worn out...
  • + 2
 Neat, but we are all bike mechanics. How's your BB holding up? Better not take your cranks off when you replace the bearings.
  • + 1
 Blenky FTW
  • + 1
 A nakarade krute....
  • - 1
 This is what you have to do when you race a poorly designed bike.......
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