Commencal's Prototype DH Bike - Lourdes World Cup
 |
Commencal's current production bike hasn't been on the market for that long, and Rémi Thirion has had some good success aboard a race-tuned version of that very machine. Regardless, the Andorran company has seen fit to develop an entirely new chassis that's nothing like the bike Rémi has been racing on for the past few seasons. That said, the basic suspension layout does harken back to one of the most successful downhill race bikes in the history of the sport, albeit with some more contemporary design cues.
An extremely high main pivot location provides quite a bit of rearward wheel travel.
The linkage is located low on the frame.
The new 650B wheeled bike, which Commencal is calling the Supreme DH V4, sports 220mm of rear wheel travel via a design that's very different to what the company employed on their last downhill bike, although it is still classified as a single pivot system. An extremely high main pivot is combined with a linkage that's located low on the frame, and there's also an idler pulley mounted inline with the pivot in order to prevent massive amounts of chain growth that would occur otherwise. Commencal is calling the layout 'High Pivot Point', which is pretty self explanatory, and it was first tested on a 160mm travel all-mountain bike to see if they liked how it performed and to fine tune pivot locations.
The V4's high main pivot gives them the rearward axle path that they were looking for: ''Why a high pivot point? To obtain the correct rear wheel path, which avoids stumbling over obstacles and carries a greater speed through rough sections. It goes back to a fundamental concept for downhill - speed.'' As mentioned above, Commencal knew that they needed to employ an idler pulley to route the chain over the main pivot, and they spent some time tinkering with different pulley placements to find the sort of pedalling performance that they wanted, saying ''specifically, by setting the idler on the swing arm in a precise place, we wanted to create an anti-squat value high enough to be lively when needed, out of a corner, for example.''
The 267mm eye-to-eye shock is mounted nearly as low as possible on the frame, and it's compressed via a tidy linkage that is said to provide a very similar feel to Commencal's previous downhill bike, at least in the first 200mm of travel, before supplying a hefty amount of ramp-up in the last 20mm to keep the rider off the bottom of the stroke.
The 267mm eye-to-eye shock is mounted nearly as low as possible on the frame, and it's compressed via a tidy linkage that is said to provide a very similar feel to Commencal's previous downhill bike, at least in the first 200mm of travel, before supplying a hefty amount of ramp-up in the last 20mm to keep the rider off the bottom of the stroke.
The chain is routed up and over an idler pulley that's inline with the main pivot.
Commencal tested the high pivot layout on a 160mm travel all-mountain bike before starting in on a DH version.
Axle path comparisons, with the new V4 being very different from the older bikes.
The new V4's geometry is all about adjustability, although Commencal have gone about it in a much cleaner looking way that the usual array of different mounting options and bolts everywhere. They're calling it 'Modular Geometry', and while the bike's head angle is fixed at a slack 62.5 degrees, its reach is adjustable by way of four different offset headset cups that allow for eight possible configurations: -10, -8, -5, 0, +5, +8 and +10mm. The bike's rear center length is also very different from the old bike, with Commencal shortening it up from 447mm on the V3 to 425mm on the V4, and it's also adjustable by using different bolt-on dropouts. However, keep in mind that the 425mm number will grow as the bike goes through its travel, which is something that some racers have found can alter the bike's handling in corners too much for their liking. To this end, Commencal have actually lowered the height of the main pivot compared to what was used on some earlier prototypes, although it's obviously still quite high. It will be interesting to see how their racers, as well as the average rider, get on with Commencal's decision to go with such a high main pivot.
 |
Author Info:
Member since Oct 18, 2005
Must Read This Week
Sign Up for the Pinkbike Newsletter - All the Biggest, Most Interesting Stories in your Inbox
PB Newsletter Signup
Commencal v4 XL stack 617mm raech 425mm (435 with adjustment)
Giant glory 2015 XL stack 604mm reach 480mm
Guess stack height is quite important
i still miss the filling ...
Edit: I take back what I said about Canfield bros executing the chain growth roller best, I totally changed my mind. Seeing how it's hidden behind the arm on the Commencal is actually really really cool. I do not take back what I said about the V3 being the best looking Commencal though, that statement remains true.
Just look at footage of Reece Potter riding. Granted, he is obscenely skilled, but what he does wouldn't be remotely possible on a bike with "bad cornering"
But dont take my word for it: www.balfa.wooyek.pl/Historic/Balfa-NR-Nouveau-Riche-review.jpg
www.pinkbike.com/u/drsanchez/blog/balfabuild2010.html
want it !!
www.americandirtbike.com/Perf406-24a.gif
www.amp-research.com/company/history
on other matters, am i gonna be the only one to call out the fact that high single-pivot with idler's being slammed by practically every single camp-jumping trendy grom rider in existence the second that dave weagle entered the scene? oh the irony...bike fashions go round in circles much faster than clothes it would seem. they all work good, it really just does come down to how nice they look really in the end, doesn't it?
What the f*ck does that chain up there ?
Guess I gotta read then
As for the wheelbase thing, its not so much the change in length that matters, its the change in relationship between front center and rear center. On a "normal" dh bike, they both get shorter at similar rates, so the bike doesnt change much in feel. On a bike like this, the fron gets shorter and the rear gets longer. This means your center of gravity gets much closer to the front wheel unexpectedly. A mate of mine used to ride a Corsair with a similar axle path. He said the rear wheel was very unpredictable in corners. As it got further away, it would also unweight itself, causing some pretty major and unexpected oversteer. Until he got used to it at least.
Your weight shifting comment is great for haters to talk about, but as you mentioned "Until he got used to it at least", the human brain is more than capable of catering to it after experiencing it a handful of times. Not something you need to consciously worry about, and very negligible IMO anyway, especially with this bikes pivot height. Having rear suspension that actually sucks up bumps rather than just bouncing off everything, wheelbase lengthening when you need it most(off jumps and drops and G outs) is a good balance of compromise. Do a days timed runs on their old and new bikes and see what you come up with. Most people will be faster and more confident on the new bike, I'm sure. The times will tell, so will the smiles.
As for the weight transfer thing. He did get used to it to the point that he could keep the rear wheel behind him in 99% of corners....
He still sold the bike 6 months after getting it. Years later he still talks about how he loved his orange (relatively high pivot, but nowhere near as high as the corsair), how much he loved his super 8 (ditto) how much he loved his big hit, how much he loves his Tues, and how much he hated that bloody Corsair.
There is definately some truth in that quote.
As I say I am not totally against high pivots or idler pulleys, but I have serious reservations about both, and no real problems with more standard designs. Watching Steve Smith on his Wilson (relatively high pivot) vs Gwin on his Demo (relatively low pivot) I don't see enough of a difference in performance between the two to make either frame stand out as radically better. The added weight and complication of this commencals high idler design is enough to put me off however, whatever the slight benefits it may offer are.