Note: Please refer to the comments for on-going dialog regarding belt-drive. I’ve revised my original blog entry twice based on the on-going dialog with Dave Walker from Paketa that has been informative but also raised more questions in my mind than it has as of yet solved. However, I am starting to turn the corner on understanding why the single side drive drive may be a better adaptation of the Gates Carbon Drive vs. the more commonly seen crossover crankset design. So, somewhat with hat-in-hand, I’ve softened this entry and will be posting a subsequent one in the near future to relay what I learn.
I usually get pretty excited when a US-based tandem builder introduces something new and interesting. But nothing diminishes that experience to me more than aggressive marketing and hyperbole.
A certain tandem maker has used marketing spin for decades that never fails to raise my blood pressure; however, it seems to work well out in the general bicycle consumer market place and also resonates and reassures their past buyers they have selected a superior product from a superior company. On the flip-side of the coin, the tandem enthusiast community’s reaction to this marketing has been labeled ‘Bashing’. In fact, coming off the mid-term elections it dawned on me that this entire marketing approach and enthusiast backlash seems to mirror the two-party political election campaigns, where two polarized groups sling mud back and forth over the heads of the undecided “consumers” who are trying to make an informed decision based on dubious claims and slick packaging. Of course, if you eliminate the marketing from the product, the product really is excellent. But, so are the products offered by their competitors. It could be easily argued that the differences in some cases could be measured in millimeters not meters and are often times simply differences in highly subjective preference.
Anyway, this blog entry really isn’t about that other company and it’s marketing. Instead, what caught my attention today was the Paketa Bicycles web page content describing their new V2r (where the r = right side drive). Don’t get me wrong, I’m genuinely excited about the new variation Paketa has offered up on its legacy magnesium tandem frame, the V2. However, there are a few things in the copy that just don’t resonate with me and some that are challenging my understanding of the pros and cons of the Gates Carbon Drive sync belt for tandems. So, let me start with what I liked before getting into what has me scratching my head.
First off, you can find the photos and Paketa’s description of the new variation at their V2r web page by clicking HERE. In short, Paketa is now offering a single-side drive version of their V2 tandem where the sync drive that connects the tandem pilot’s cranks to the stoker’s cranks is located on the right (aka, drive) side of the tandem. This is a variation that has been in use on tandems going back to the late 1800′s, along with many other variations of tandem power transfer systems. Since then, right side drive tandems have always been around, but in recent years the push to find ways of removing weight from tandems as well as more practical reasons — such as taking advantage of the ‘free’ chain ring that came available when a Rohloff internally geared hub was installed — have made right side drive tandems more common. In fact, we’ve seen a few right-side drive off-road tandems being prepped for customer delivery by our good friend Alex Nutt at MTBTandems.com.
Paketa’s right side driver is a bit different from others in that they have revised the design of their rear bottom bracket’s chain stay yoke to allow the installation of a 69t Gates Carbon Drive sprocket on the inboard position typically occupied by the smallest chain ring (aka, alpine or granny ring) of a triple crankset, but in this case bolted to a double crankset with the same net effect. Of course, Paketa is not the first firm to play around with their chain stays (or rear bottom bracket / yoke) to accommodate things like the 69t Gates timing sprocket. In fact, one of the newer Calfees I’ve seen that was built for the Gates system appeared to have a a new kink in the left-hand chain stay that accomplished for a crossover crankset what Paketa is now offering in a same-side drive, a tighter fit to against the bottom bracket area. I’m not sure if there’s a patent pending on it or not, anymore than there were patents taken out for other chain stay shapes that provided more heel clearance, increased tire clearance, or wider bottom brackets to allow for larger, more robust stays.
Getting back to Paketa’s right side drive and that inboard Gates sprocket position, therein lies one of the cons for a right side drive: right side drives need to use one of the main drive crankset’s chainring positions. There are several other pro and con arguments typically associated with right side vs crossover cranks, some are more valid than others. Clearly, eliminating an extra crank spider and chain ring will reduce weight and opens up the ability to use a wider range of standard cranksets on a tandem… that is, so long as they’re rated for the combined weight / power of a tandem team. Again, there are some others that I’ll analyze in a moment as I go through Paketa’s Web material with you.
The potential gearing range limitation isn’t a big deal for a tandem that will be used for riding or racing on all but mountainous circuits where the really short climbing gears are never used. Instead, a team that doesn’t need serious climbing gears can mate what is essentially now a standard double chain ring crank configuration to a nice close-ratio cassette and enjoy single-bike like shifting or even use Shimano’s Di2 components. This could be a really slick set-up for a dedicated race bike or strong recreational teams who live, ride and race in places that don’t have significant climbs. Now, bear in mind that anyone with a tandem could easily replicate this right side drive configuration today using sync chains and timing rings on a triple rear and standard double front crankset with the new, wider-range 11X36t cassettes from Shimano and SRAM. So, the only real difference here is figuring out how to get that wider belt sprocket into the narrow space between the chain ring and cranks without using some bizarre, wide, off-set bottom bracket axle and moving the front derailleur outboard with a special clamp. Seems like an awful lot of work to save an extra pound or two on a racing tandem that isn’t ideally geared for steep terrain… where a rider would actually benefit from frame weight reductions.
So, here are the things in the on-line copy that didn’t resonate with me and challenged my understanding of the pros and cons of the Gates Carbon Drive sync belt for tandems, starting with the ‘better’ gearing system, which reads:
Better gearing system
As for gearing range and shifting, the V2r again excels. The combination of 2X10 road and MTB gearing provides the same wide range as a conventional triple-chain-ring road setup. With a 39/53 double sprocket in front and 11X36 cassette in back (as shown in the photos), the gear range is identical to a road 30/39/53 triple crank with an 11X28 cassette—certainly enough for most any tandem team interested in racing or fast sport riding, for sure. And, with a double sprocket in front, the shifting precision is as good as any single bike, and any road shifter compatible with a matching MTB rear derailleur and cassette will work (SRAM™ Red™ Double Tap™ shifters, Red™ front deraiiluer, SRAM™ XX™ cassette and XX™ rear derailleur shown). Say goodbye to triple front shifters and substandard front shifting!
As I mentioned earlier, for high-performance teams who ride tight ratio cassettes like an 11-23, the right side drive V2r makes sense and would be an attractive package. In fact, I just ran the numbers on the gear inches and was pretty surprised at how closely they did match up to the 11x28t triple… OK, I was REALLY surprised. So surprised that I’ve actually re-visited this blog entry and made some changes and I must thank Terry Malouf who is one of the owners of the first Paketa V2r for responding and making me do a re-read of what I wrote. However, that said, I still believe that for more average fast recreational / sport teams who must deal with any steep stuff, those folks will really need to be really honest with themselves regarding their current gearing: could they really live with just a 30x28t. If so, this might be a good option. However, if they ever needed something shorter than a 28″ gear… noting that a 30x32t granny yields a 24.9″ gear and a 30x34t granny yields a 23.3″ gear, they could find themselves walking a few hills.
Let’s take a closer look at the Paketa 2×10 scenario that saves 1lb: “With a 39/53 double sprocket in front and 11X36 cassette in back, the gear range is identical to a road 30/39/53 triple crank with an 11X28 cassette“. Here’s how those two different cassettes stack-up:
-This is what you give up…11-28: 11-12-13-14-15-17-19-21-24-28 And this is what you get…11-36: 11-13-15-17-19-21-24-28-32-36
Again, potential buyers really need to be sure they can deal with whatever length and grade climbs they expect to encounter with nothing larger than what they could have handled with a 53/39/30t triple and an 11x28t cassette. Most tandems these days tend to come with an 11x34t cassette, which is a very different animal than an 11x28t.
For reference, we’re hardly elite racers but we do tend to fall into the demographic that does the suggested fast sport riding and rides higher-end performance tandems. Here’s our “normal” gearing for hilly but not the really steep stuff… a very nice progression:
Pending release of the 11x32t Shimano CS-M771 cassette, the first cassette listed below (an 11x32t 9 speed) is our current ‘alpine’ gearing. It’s less than ideal with that awkward 18 to 21t jump that we have to deal with a lot on moderately long or steep climbs. Thankfully, the 11X32 CS-M771 will beak that up a bit. Again, here’s how all these different cassettes stack-up:11-32: 11-12-14-16-18- 21 – 24 – 28-32 12-27: 12-13-14-15-16-17-19-21-24-27 11-28: 11-12-13-14-15-17-19-21-24-28 11-32: 11-12-14-16-18-20-22-25-28-32 11-36: 11-13-15-17-19-21-24-28-32-36
Compact drives and doubles have not been the hot ticket for tandems, heretofore. Now, as is always the way with bicycles, with Shimano & SRAM’s introduction of 2×10 systems for off-road bikes they’ll likely become more common, just as compact drive did for the road and 29′er bikes for off-road. So, perhaps 2×10 drives on road tandems are inevitable. However, there are limits to just how flexible a 2×10 drive train can be, and therein lies the problem with the marketing spin: it’s trying to over-reach and make a credible product offering appealing to consumers under the allure of ‘lighter weight and better shifting‘ who may not be well-served by that product over the long-haul. Obviously, the V2r can always be fitted with a crossover crankset that would allow for the use of a triple, so it doesn’t lock in an owner to the right-side drive / double chain ring configuration.
What sticks in the back of my mind is, it’s been my observation that the stronger tandem teams of median income will have only one tandem they use for everything vs. a dedicated race machine, and they still keep that granny gear on the bike with their 11x23t or 11x25t cassettes for use as a ‘bail-out’ gear when they find themselves on those longish double-digit grades or run into a wall while touring or attending a rally away from their normal terrain. Yes, we’ve seen one or two teams with older Santana Team tandems from the 90′s that had DuraAce doubles or somewhat newer tandems with unused granny gears hammering up some 18-20% grades, but they’re the exception and not the rule. However, I’m not sure they’d have been willing to give up their closer ratio cassettes for what the 11×36 offers. But, to be fair, that’s just a guess since none of these teams were all that concerned about or giving up much in the way of their dominating performance as they rode their 40lb tandems up those walls vs. mere mortals with deeper pockets who struggled up using the granny rings and the largest sprocket they had on the newer 30 lb lightweights and exotics.
It’s also worth noting that another tandem builder has been dangling a compact 11x36t drive train set-up with a Di2 option out there for 2-years or so. It would be interesting to know how many of those have been sold and what folks think of them, as well as how they’re being used since that is fairly important too. For example, I ride a compact drive on my single (50/36) and it’s great, but… not sure I’d want to use it on the tandem where we live and ride. You give up a lot of useful gear range that, while you don’t use it a lot on the tandem, you appreciate that it’s there for those infrequent occasions when you want to spin-out that 53/11 gear (and it happens a lot sooner in a 50/11) or you hit a wall that you just rather not grind-out standing on the pedals at 50 rpm.
Finally, I still don’t get the spin on “Say goodbye to triple front shifters and substandard front shifting!”. It must be a Shimano STI thing, as I just don’t hear of folks who use bar-ends or Campy Ergo having front shifting problems, except where their technique is all screwed-up, i.e., trying to shift under load and way too late. Well, and then there’s always the problem where so few mechanics know how to work on tandems, which also leads to problems. But I digress.
Looking back at the rest of the copy on the V2r web page, there are now a few other things that caught my attention once the ‘Better gearing system‘ comments caused me to crank up the gain on my ‘does it pass the common sense test’. Here are the items that caught my attention:
How do you quantify this? “Why is the V2r the absolute best racing tandem on the market?”
Let’s take a look at those inherent Crossover drive disadvantages:
- Tandem-specific cranks are required with a spider or other mount for the transfer sprockets (Actually, that’s not quite true. A crossover crankset can be easily constructed using three right-side standard cranks and a single left-hand cranks. R&E cycles in Seattle has been outfitting their Rodriguez tandems with Campy cranks in this manner for years. Yes, it requires some minor re-work on the cranks, but it’s a tried-and-true practice.)
- Three spider-mount crank arms are required, which adds to the weight of the system (Unless you use daVinci or Middleburn cranks, which don’t use a spiders, noting that daVinci’s cranks have always been some of the lightest cranks on the market… lighter than many of the carbon offerings until perhaps recently. But, yes… in general a crossover crankset will be heavier than a right side drive)
- The rear bottom bracket experiences high loading due to the force of three riders’ legs (both of the captain’s plus the left stoker’s leg) being transmitted through the rear crank axle. (OK, I’ll give them that. However, before the bicycle industry started messing around with what were promised to be lighter, stronger bottom brackets and weren’t, just how many tandems running normal width square taper bottom brackets were experiencing abnormal failure rates? I’ve see Shimano UN72′s deliver over 20k miles of hard tandem use without any maintenance )
- Both torque and bending forces are significantly higher—as much as three times as high—as on a comparable single bike, resulting in either reduced component lifetime or higher weight, or both. (See prior comment )
- Modern belt transfer drives on a tendem’s left side, place much higher loads on the bearings due to the higher tension required compared to a traditional transfer chain. (This is where my understanding understanding of the pros and cons of the Gates Carbon Drive sync belt for tandems is seriously challenged. Before the ensuring dialog with Dave Walker was created by my original version of this blog entry I believed and wrote, “… this is probably true for when a tandem is sitting still and no loads are being applied to the pedals since a belt needs more static tension than a chain to ensure it does not slip once pedal loads are applied. However, those loads are miniscule compared to the loads applied by the pilot during use. Seriously, belts are hand tightened using a pin spanner. If you assume that similar size rings and sprockets are used for the chain or belt, there should be no significant difference in the loads being transferred to the bottom brackets by the tandem pilot’s power output. As of Nov 11th, I’m still trying to come up the learning curve on the belt technology vs. what I thought I’ve observed. The latter is call covered in the comments appended to this blog entry.)
Here’s another one of those great, subjective dubious marketing statements: “The Paketa V2r tandem (patent pending) eliminates all of these problems” What problems? If previous ‘innovations’ in bottom bracket designs weren’t so poorly thought out before being rolled-out to the general public, most tandem teams would still be using their original bottom brackets after 20k miles of use. Reducing weight is novel, but as over-rated as reducing rolling mass when it comes to generating performance improvements for all but the most elite athletes. Therefore, I’m hardly inclined to believe that shaving yet an additional pound off a tandem with 320 lbs of riders, never mind even 10 lbs of bike weight, is anything more than marketing hype feeding consumer vanity and hubris. Well, yeah, it’s also fun to see how light you can get a bike, but that’s simply a distraction from the reality that our physical performance is what truly limits the speed and power envelope of our tandems. We’ve already discussed that you can already use just about any cranks on a tandem, so long as the spider is rated for the total loads that a tandem with several hundred pounds of riders standing and pedaling up a 20% grade in a high-purchase gear like a 39×36. And, as far as boom tube deflection under loads, if a modern tandem’s frame isn’t robust enough to prevent unpredictable handling with a crossover crankset, why would it be immune to right-side wind-up that now runs from the rear axle to the front bottom bracket? This is actually a red herring for most tandem teams if they’re riding a tandem that was designed to deal with their weight and power. IMHO, the real place to focus attention with tandems — especially open frame / lateral-less tube models — is making sure the top tube and overall structure provides sufficient stiffness to resist torsion flex which truly can create a tandem that handles poorly under heavy efforts or rider / luggage loads.
Let’s see what else is on the 2nd page. Yes, Paketa does a fantastic job with its Magnesium frames, just based on feedback from most of the owners I’ve spoken with or who have documented their impressions. And, yes, I’m sure the new yoke is also exceptional. But, this is a stretch: The yoke design allows the transfer sprocket to fit in as close as possible to the center line of the frame, yet still provides enough clearance for up to a 28 mm tire—enough for even Clydesdale-class tandem teams to enjoy the benefits of a light weight Paketa tandem. If a single-bike rider is classified as a Clydesdale or an Athena when their weight exceeds 200lbs / 90kg, a Clydesdale-class tandem team would be one that weighs over 400lbs. A 28mm tire is marginal, at best, for a team that tips the scales at 400lbs. Yes, they can get away with it but the tires need to be pumped at or beyond max psi rating to preclude pinch flats which works against the team on anything but the most smoothly paved roads, both in terms of rolling resistance and transfer of road shock.
Thankfully, we’ve already addressed my perceived value or lack thereof of reducing tandem weight and the pitfalls associated with using wide-range cassettes so I think I’m done.
So, in closing let me be clear that I really wanted to be excited by the V2r… and I was until I read the print material which I’m still trying to understand. I’m sure the Paketa V2r is just as good of a frame as the Paketa V2, albeit somewhat limited in gear range / gearing efficiency. But, for certain teams with very specific needs and abilities, it will no doubt be a great choice.