As mentioned in my blog entry last Monday entitled Give ‘em an inch… BQ & Tires, there are all kinds of different ‘tandem tire camps’ when it comes tire size and pressure. The only hard and fast rules I know are that tire decisions should (a) never be made based on fashion, or (b) recommendations by folks who aren’t similar to your team in terms of size, riding style and local road conditions. In this regard, and without getting buried too deep in the debate, there are a number of things that dictate what tire size teams should consider:
- Their total team weight. Just because some really fast team rides 23mm or 25mm tires doesn’t mean 25mm tires are necessarily a good choice for all teams. Narrow tires don’t typically yield lower rolling resistance unless they are pumped up to their optimum recommended psi ratings by riders of average weight and used on very smooth roads. For a tandem team, this usually means running tires at or even slightly above their recommended maximum psi ratings to off-set the extra weight of a loaded tandem. As noted in #2, below, the latter can yield a pretty harsh ride on anything other than very good roads and suck the life out of a team on chip-seal or other less than ideal road surfaces. Therefore, a 28mm or even a 32mm tire may actually roll more efficiently at a lower psi rating vs. a 23mm or 25mm tire if you’re not willing to deal with the downside of very high-pressure tires. In this regard, BQ is spot-on with their general thesis that a larger diameter / volume tire would be better for cyclists who ride on very demanding road surfaces. But, even for tandem teams that never venture off very smooth roads, if a team’s weight is over 300lbs they should consider nothing smaller than a 25mm tire for general use. Over 350lbs, a 28mm tire and so on up the size range: it’s just a physics thing… don’t fight it. Yes, this could create some equipment issues, as noted below at bullet #4 and all tires are not created equal as discussed at bullet #3.
- The condition of the roads they will be using. Here in the Atlanta, Georgia area we are blessed with very smooth asphalt roads. We don’t suffer from frost heaving, and here-to-fore and except in certain places closer to Atlanta (i.e., Fulton County), our roads are kept in very good shape with very few pot holes or other defects that would take away from a comfortable ride on narrow, high-pressure tires. In our case and as a 270lb team, this has allowed us to use 23mm and 25mm tires for many years. However, in places that have chip-seal, concrete with expansion joints, winter-damaged roads, or perhaps even sections of unpaved roads, a much wider tire with lower psi would be essential for optimum performance. I can vividly recall our encounter with some Texas-size chip seal in Texas while running the same 23mm tires @ 145 psi we use here at home and it was pure torture. Lowering the tire pressure helped, but we would have been better off with 28mm tires running something closer to 100 psi. The same was true when we encountered bike paths with expansion joints in Dayton, Ohio and some pea-gravel chip seal near Williamsburg, Virginia where a 25mm or 28mm would have been more appropriate. Therefore, before assuming that the tires we use here in Atlanta might be a good choice for your team, ask yourself: how do our roads compare? Moreover, if you plan to travel, make sure you do your homework on road conditions so that you can make the right choice. Again, this is why it’s important to think about tire size when shopping or spec’ing a new tandem, ref. bullet #4, below.
- Expectations for durability, longevity, comfort and rolling resistance. The most popular narrow tires (23mm – 25mm) are often times ‘racing’ tires, which means they tend to be lighter, supple, and have softer more ‘sticky’ tread than less expensive training or general purpose tires. They are also more expensive, have very short tread life and are far more susceptible to damage from road hazards. And, the heavier the riders, the shorter the tread life: sometimes a lot shorter. Comfort is also not typically something associated with very high pressure tires, and rolling resistance is only lower than larger ties if, as noted earlier, they are used on very smooth roads. Wider, general purpose ‘sport’ tires are a better choice for most mid-weight tandem teams (25mm – 28mm) looking for a tire with lively feel, a bit more give but less ‘float’ than a larger volume tire. But once again, good grip means a softer tread compound, and softer tread compounds don’t last long or resist road hazards as well as a touring tire. With a few exceptions, the larger 28mm – 32mm tires are typically made using heavier, harder, longer-wearing compounds that are far more resistant to road hazards. The larger tire volume typically off-sets the loss of suppleness that comes with the harder, long-wearing tread compounds so the only big loss in performance comes in aggressive cornering where the larger footprint of the wider tire doesn’t always off-set the loss in tire grip from the harder tire compound and typically don’t track as well as more narrow, higher-pressure tires. As for tire weight and any potential acceleration penalty due to increased mass and rotational inertia, it suffices to say that the differences associated with a heavier tire are truly negligible and typically over-hyped. That’s not to say the average cyclist won’t be able to detect a difference in lighter tires, but what they’re experiencing doesn’t really relate to an increase in acceleration. You can find an excellent series of tests performed by French language site Roues Artisanales back in 1998 on wheel inertia, as well as aerodynamics at this English language version of their test that quantifies the differences. Also, for anyone who is interested in some really detailed analysis of rolling resistance, and trade-offs against puncture resistance, durability, weight and grip, you’ll also want to visit Roues Artisanales and their January 2006 article on tires; Linky to English translation. The following is an snapshot of a polar plot from the article, just to whet your appetite.
- Frame, fork, brake and rim width constraints.While many production tandem frames will accommodate rather large diameter tires, frames that are fitted with short-reach (aka., compact) caliper brakes are typically limited to a maximum tire size of 28mm. Frames with cantilever, linear-pull / V-brakes, or disc brakes shift the tire-size limitation to the rear chain / seat stay and brake bridge clearance. Again, most stock production tandems will have fairly generous tire clearance, but racing or performance tandems like a Co-Motion Macchiato, stock Calfees and some others are typically limited to 25mm tires, unless a buyer specifies the need to accommodate a larger tire. There are also certain forks that have tire size limitations, the most notable being the True Temper Alpha Q forks that for many years would fit nothing larger than a 25mm tire. More recent models were able to accommodate a 28mm tire, but it was a tight fit. Co-Motion’s new house-branded carbon fork will accommodate up to a 28mm tire. Again, just something to think about beforespec’ing a tandem that could find its way onto a crushed gravel bike path like the Katy-Trail, on a European Tandem Rally that ventures onto unpaved roads, or perhaps a family relocation to some place where chip-seal roads are the norm and a 25mm maximum tire size would just be a non-starter.
- Rider preferences & expectations for handling & feel. Even though a tandem pilot may intuitively know they should be using a larger volume tire given the aforementioned qualifiers, they may simply prefer a tire that is either more or less compliant for any one of a number of reasons. To this day I remain baffled when I hear someone complain that their Cannondale road tandem is too harsh, when any perceived harshness could be addressed by using a larger tire with lower pressure. Likewise, when someone complains of truck-like handling on a tandem, a more narrow tire with higher pressure can be used to ‘tighten-up’ the bike by increasing road feel and giving the steering a lighter touch. These same preferences can come in to play with regard to how different size tires feel during aggressive cornering or during high-speed descents. While I know that we should have always been riding 25mm tires on our tandems, I’ve stuck with 23mm tires for over a decade simply because I had such a bad first experience with the 700x26mm Specialized Transition Armadillo’s on our ’95 Santana Arriva: it felt like I was riding on marshmellows. Upon returning home after that first ride with Debbie I immediately stole the 23mm Vredestein Fortezza Tri-Comps off my single bike and put them on the Santana. The handling and feel of our Santana was transformed by the 145 psi Vredestein tires that I was accustomed to using on my single bikes. It was only when we took delivery of our Erickson S&S equipped travel tandem that I purchased the 25mm version of the Vredestein Fortezza tires after having a bad experience during a trip to Texas, mentioned above. Over the past 8 years I’ve slowly weaned myself off the 23mm tires to where we only have a few left on hand and typically have he 25mm Vredestein tires on our Calfee and Erickson road tandems. While I’ve experimented with some other 25mm and 28mm tires and lower psi than our 135 psi 25mm Vredesteins, none of them have been able to deliver that precise handling through fast cornering maneuvers that I’ve come to expect from the Vredestein tires. Yes, this has come at the expense of some comfort (not fully realized until just a couple years ago), many pre-mature tire replacements due to terminal road hazard damage, and very short tread life. Hard to know if we’ll ever switch over to 28m tires, although we will experiment over the winter. However, the point I was trying to make is, despite having all the facts in hand on tires personal preference can often times override a logical choice IF you’re willing to deal with the consequences bounded by ensuring the safety of your stoker.
My apologies for being so long-winded again. Not sure what has possessed me to return to more wordy writings… perhaps it’s the sub-freezing cold snap that has hit us here in Atlanta, or some personal unrest related to leadership changes at work.
Regardless, hopefully this article has made you think about your tire selection in a way that you hadn’t before. That’s not to say that you need to do anything different, but perhaps it may reveal why you like or don’t like the way your tires have been performing and cause you to investigate some alternatives. And, to be honest, this article has merely scratched the surface on tire discussions and topics. However, these really are the basics that any enthusiast will want to consider. Differences in tire casing construction, tire compounds, inner tubes and their influence on tire performance are subjects for another day, or not.