After watching footage from the first few UCI World Cup downhill races this year, we’re sitting around the office blown away by the speed at which the riders could seemingly fling their bikes over some seriously gnarly roots, rocks and drops. We also noticed that some of the rocks and root “cavities” (the gullies between big roots) seemed to occasionally be just a hair too much for the bikes, forcing the riders to navigate around some obstacles rather than bomb over them.
Not being big downhillers here, we got to wondering why no one was running a 29″ wheel on a downhill mountain bike…at least on the front. As we all know by now, a 29er’s larger wheel rolls over stuff easier, and some of the bits on the World Cup downhill courses were seemingly just beyond the capability of a 26″ wheel to get over (even with 8″ of travel!), but could have been tackled by a 29er.
So, in typical Bikerumor fashion, we called the experts. Lots of them. We wanted input from big brands and small, global companies and boutique DH specialists. We also wanted a dedicated 29er brand…so we went overkill and interviewed the folks from Specialized, Foes, Banshee, Norco, Santa Cruz and Niner and asked them the following three questions:
- Why don’t downhillers use 29″ wheels, at least on the front?
- Has your company or any of it’s factory riders ever tested or prototyped a 29er or 69er downhill bike?
- Anything else you could add on this topic?
Hit ‘more’ to see how they answered (hint: Niner’s just might be working on something)…
This video, from the U.S. Open Downhill was the inspiration for this post. Ã‚Â The replies below definitely have some overlap, but we copied their responses in their entirety so you can pick up on any subtleties from your favorite brand(s).
1. Why don’t downhillers use 29″ wheels, at least on the front?
Brent Foes: That’s a good question, and common logic would indicate that the 29er would, indeed, be well worth developing as a downhiller platform. Interestingly, every few years designers in both the dirt motorcycling and bicycling industries fire up those lingering ideas about the benefits of larger wheels on rough ground. The latest of these is the 29″ wheel for mountain bikes. As you have suggested, dowhhillers could sure use the theoretical benefits – smaller friction coefficient – of a larger circumference wheel. However, as in all things wheel-oriented, there are real world sacrifices that have to be made for this gain – namely, the increased leverages and energies that downhill obstacles would place on the longer spokes – as well as on the rims and hubs. To mitigate this, we would, of course, have to make thicker gauge spokes and/or even heavier, flanged hubs, thicker rims and larger, thicker downhill tires than already exist. But, here’s the rub: a 29er wheel already has a greater rotating mass over the 26″ wheels currently built for downhill – add the mass of stronger spokes, rims, hubs and tires (and bigger brakes to control this mass) and you have an even larger sprung and rolling mass to contend with. Even in just the front, this would be much more difficult to control (steer, accelerate and brake) than the current setup.
Joe from Santa Cruz: Since the best downhill forks on the market are 26″ wheel specific, there is no option for a 29″ wheel on a DH bike that has the best in front suspension. Additionally, the increased height of the front end of the bike would cause issues, albeit surmountable if it was merely hand position. To the best of my knowledge, there are no DH tires or tubes for the wheel size either. Not “big knobby tires” but true DH casing, with tread profiles for different terrain and weather conditions. Or, for that matter, rims. For rear wheel travel, its difficult now to package tires, clearance and the amount of travel necessary, along with geometry that is good for DH racing with a 26″ wheel. Simply getting 8-10 inches of travel without the tire hitting the seat and a larger tire would prove difficult, and may cause major comprimises to other, arguably more important attributes.
Dustan from Norco: There are really two issues in marketing a downhill bike with 29″wheels:
Nic from Specialized: A 29″ wheel does make it easier to roll over obstacles vs. a 26″ wheel. In my experience, the gap begins to narrow as you get into longer suspension travel and slacker head angles. On short travel bikes, the wheel size difference and increased roll-over is more noticeable than a downhill bike with 180-200mm of fork travel and a 66 degree head angle. Also, larger wheels are not as strong which is not ideal for a DH bike. The trend in downhill is to get the front end of the bike as low as possible, and a 29″ front wheel combined with long travel will make it very hard to get the bars to a reasonable height, especially on a size small. 29″ rear wheels will pose an even greater problem, as it is very challenging to package 29″ and long travel into a reasonable setup with short chain stays. Saddle-tire interference at bottom-out is also an issue with the long travel and low saddle height of a downhill bike.
Jay from Banshee: Downhillers don’t use 29″ wheels for a couple big reasons and some are particle problems while others are performance based. First DH’s need travel and have found that 8″ front and back tend to be pretty decent numbers for absorbing big hits and chundery sections of trail – here’s where the problem comes in when designing a 29r DH bike. You physically can not have an 8″ travel DH bike without having an enormous wheelbase. Even now many longer travel 29rs feel like your driving a boat through tight and twisty sections, and this is a non starter for DH racers. Even at this moment Banshee is designing a 17.3″ chainstay 5″ travel 29r and the challenges to maintain those numbers are tremendous. Also even if you were to limit only the front to a 29r there is no fork on the market that will accommodate a 29r tire and give you 8″ of travel in a dual crown. Granted you could run less travel and still get the “feel” of 8″, but…
The big wheels are harder to get up to speed then a smaller tire and with any DH course I’ve ever raced or have seen there are slow tight sections followed by flat out sections. These sections are mixed throughout the race course and demand quick acceleration out of corners and fast starts right out of the gate. No DH racer is going to want a second slower start to get his bike up to speed and then have to gain it all back later. Now, one could argue then why not run 24″ front and back? While we played with this idea a few years back when the 24″ wheel was popular there were a few things that left us wanting. One was they didn’t carry their speed very well and I can personally remember barely making transitions on a couple runs where switching to a 26 it was no problem at all. I truly believe the 26″ tire is kind of a sweet spot for anything that is gravity driven.
Chris from Niner: A lot of the reason 29ers haven’t made it into the DH scene is the lack of available product for this market segment. There are really no tires or rims available, and very little in the way of long travel forks that can take DH punishment. We feel like there is still some viability here and are constantly pushing from our end to see some development of DH worthy parts. We’ll have an exclusive on a big hit tire to premier with our WFO 9 caller the WTB Kodiak. It’s a 2.5″ wide, burly big hit tire with tacky rubber and DNA for anti-pinch flatting. It’s not a true DH tire since it’s rolling on an Aramid bead to save weight, but it’s a very good compliment to a big hit 29er and can handle some DH use. We’ve tested the tire and the WFO 9 on DH courses across the country and it’s been very fun.
2. Has your company or any of it’s factory riders ever tested or prototyped a 29er or 69er downhill bike?
Niner: We’ve played around with our WFO 9 on the DH courses. Earlier prototypes of the WFO 9 (which currently has 5.5″ of travel in the rear) featured as much as 6.5″ of travel and this is a LOT on a 29″ wheel. We feel strongly that 29ers simply don’t need as much suspension travel as their 26″ wheel counterparts, so a viable DH rig can be built with less travel and therefore lighter weight. Currently, even our production 5.5″ travel WFO 9 can handle DH (we offer a 150mm spacing on the rear and it has ISCG tabs for chain guides or a Hammerschmidt).
Specialized: We have never tested it, and Sam and Brendan have never requested or asked for any type of 29er or 69er Dh bike. We are always willing to work with our riders and test their requests and suggestions, they have just never asked for it.
Norco: We do not have a 29″ downhill bike and you won’t likely see one in the next few years. The larger wheels have some benefits but the detriments unfortunately outweigh them. The idea of a 69er bike helps to keep the center of gravity lower than a 29er but also increases the stack height of the bar. The industry as a whole has worked quite hard to keep the bars/center of gravity low and this is moving in the wrong direction. At Norco we are looking at the 29er as an area of growth in the XC/AM markets but do not see an immediate need for a 29er DH bike.
Santa Cruz: No.
Banshee: We’ve never tested a 29r or 69r DH bike because no one has ever made one. The closest we are probably going to get is (a) bike we’re working on now. (Not the bike hinted at here, but Banshee’s Legend DH bike shown below)
Anything else you could add on this topic?
Banshee: I’m not sure if there is much to add with regards to a full DH 29r bike. The thing with these type of bikes is they do feel like you have more travel when you take a similar travel bike, say a 4″ in a 26, and put it up against the same travel 29r; the 29r is going to feel more like a 6″ travel when comparing the two. So this begs the question do we need an 8″ travel 29er or would a 6″ work just as well? For me DH falls into 2 categories, Freeride and DH race. The later I feel will always stick to 26″ but if winning isn’t your motivation and just having some fun then I think the 5″ to 6″ 29r will be the ticket, provided you can keep the jibbing/flickabilty aspect of the bike.
Specialized: Darren Berecloth rode the new 29r Stumpjumper yesterday and came back say good it felt and that he would like to try one up in BC, so who know maybe he will lead the charge to freeride 29ers.
Foes: When all is said and done, the 29er just doesn’t lend itself naturally to the requisite qualities of a current downhiller. The 26″ wheel in its present configuration seems to be the best compromise at the moment (and, this is why you only see shorter-travel 29ers). That is not to say that it will not be tried at some point – but, especially in these days of R & D cutbacks, it’s difficult to make the case for a clean-sheet design to achieve a minimum (if any at all) gain in just one small part of the downhill equation.
Niner: We think 29ers can be competitive on the DH scene, and are pushing for manufactures to believe in longer travel components for 29ers. We think it’s only a matter of time before this can become a reality.
Santa Cruz: 29er advocates appear to have set the benchmark of 29er acceptance as the wheel size being applied to DH bikes. Unfortunately, I have met no advocates that understand well the rigors and abuse that World Cup racers put frames through, and demand from their machines. Many of these issues have yet to be resolved entirely for 26 inch wheels, and the DH market is very small. For example, there is only one rain race tire used by the entire pro field – because other companies refuse to tool parts for such a small market. Look at the cost of a Fox 40 or Boxxer World cup fork. Those are platforms that are specifically designed for the 26 inch wheel, and are very expensive to develop. Segmenting the DH market further is likely to be a major hurdle.
Editor’s note: Just for fun, here’s Specialized’s 2010 Demo 8 downhill bike…full post on the 2010 Specialized mountain bikes coming up this week…