“Vanity, thy name is gumwall.” With apologies to Ecclesiastes and Shakespeare for this corruption of a misquote, no one, not even the tire experts at “Bicycle Quarterly” suggests that there is any performance benefit to gum wall or tan wall tires. The more accurate and true quote fits here: “vanity of vanities, all is vanity” (Ecclesiastes 1). Why else would one seek out an attractive tire in favor of those that are known to perform superbly?
THE REALITY – Tan Wall, Gum Wall – there’s little evidence that under either term this tire feature adds anything to performance. The esteemed journal “Bicycle Quarterly” (https://albanybicyclecoalition.com/2013/10/14/in-living-color-bicycle-quarterly/ ) has tested every aspect of tire performance EXCEPT this one, so arguing that the color of the sidewall makes a difference is coffee time chit chat. Then again, appearance is important to performance so who’s to argue? See – https://albanybicyclecoalition.com/2013/06/05/eat-your-heats-out-black-tyre-people/
THE NEED – My Brompton came fitted with Schwalbe Kojaks (size: ETRTO 32-349, 16″ X 1-1/4) as ordered. Since these tires are basically slicks with no tread, they don’t look much different than an inner tube on the rim. With no tread wear to measure, it is hard to test the Kojak’s degree of wear until some cord starts showing – which it had not. But having discovered the Schwalbe Marathon Racer (size: ETRTO 35-349, 16 X 1-1/3) while preparing for the Kojaks’ inevitable end of life, I put it in the back of my mind this was the tire for me. I had experience with Schwalbe as a brand in addition to several credible YouTube analyses supporting the contention that the Marathon Racers were a good choice for the Brompton. (for a somewhat explanation of tire sizing, go here – https://www.getmefixed.co.uk/wheel-sizes-explained-etrto-imperial-radius/). In this case, the ETRTO (European Tire and Rim Technical Organization) inner diameter spec (349 mm in both cases) is of no value because the issue, as we will see, is with outer diameter, nominally both 16”).
THE BEST – The YouTube channel 2Bikes4Adventure (the “2Bikes” are Bromptons and the “adventure” is touring on them) has a video titled “The BEST TIRE for your Brompton” The hosts do a commendable job of analyzing competing 16” tires based on considerations of weight, puncture resistance, rolling resistance, and cost. This is not just another “everything is lovely” semi-promo review. This YouTube channel, 2bikes4adventure, suffers a little bit from the pressure by YouTube to have very short videos. Nonetheless, the program covers six different tires in the 16-in category as follows: Schwalbe’s Marathon and Marathon Plus, Continental’s Urban Contact and then the Racer, Kojak, Marathon One all by Schwalbe. They describe how each part of the evaluation was conducted and then graphically compare the different tires on their performance against each functional test – rolling resistance, puncture resistance, weight, cost, etc.
They note that the Racer is 35 gr heavier than the Kojak, for example. For puncture protection, they cite tests using a graduated plunger to pierce the inner tube and anti-puncture layer while measuring both the amount of penetration and the force needed to reach that depth. They allude to a pinch flat test wherein a tire is dropped on two sharp edges (as in a pothole). With the exception of falling into the ”more-psi-means-more-speed” trap, they do a nice review on the Tan Wall.
BROMPTON SCHWALBE MARATHON RACER TAN WALL – (Brompton Schwalbe Marathon Racer Tan Wall – YouTube ) The Tan Wall was originally unique to Brompton when introduced in 2020 and was fitted to the light-weight special edition Chapter 3 bicycle (https://us.brompton.com/bikes/special-editions/chpt3 ). With a black titanium rear frame and fork, this model has a stripped back look with (significantly as will be seen) no mudguards (fenders) or front luggage carrier. It has premium grips, saddle, hinge clamps, and rear frame lever. The Tan Wall was otherwise not available to the public. \
As a safety aside, the Tan Walls do not have a reflective sidewall element as is common with many contemporary tires – including the Kojaks.
THE FIRM – Schwalbe (in English, “Swallow”) has been around since 1922 under the name Ralf BOHLE GMBH (Gesellschaft mit beschränkter Haftung literally, a “company with limited liability”). In recent years, the company has dedicated itself to bicycle and wheelchair tires and tubes. It is headquartered near Köln, but its manufacturing is through collaboration with firms in Korea and Indonesia producing 14,000,000 tires per year. Schwalbe introduced the “Marathon” in 1983, the “Racer” in 2018, and the Tan Wall in 2019/2020. All three models rate high for puncture and pinch flat protection. The latter being of interest to riders in our local third-world-style roadways.
INSTANT APPEAL – When the Tan Wall option came along, my decision making was all over. A couple days after ordering them from my local bike shop, I got an email saying the tires are ready. So with the two new Marathon Racers and two new tubes I headed home to do the installation. That was to be postponed until the following day having done nothing more than open and unfold the tires and look at them. Unmounted, they impressed me as being quite large, and in the middle of the night I started to wonder if I was going to have a fender interference problem as is sometimes the case with even slightly larger tires.
INSTALLATION – The installation of the new tires went fairly smoothly until I remounted the rear wheel and heard the ominous rub, rub, rub.
The Brompton has a stubby mudguard extending horizontally from the rear fender and held by a 4 mm bolt, nut, and two flat washers. (Brompton likes washers – there are 13 on each of the rear EZ wheels.) Some investigation showed that there was very little adjustment possible with the fender relative to wheel and tire. Any effort to raise the fender runs into the unmovable luggage rack. Afterall, these are not SKS fenders (the best on the Planet for any Bike), but a proprietary Brompton design.*
The bracket that holds the fender closest to its rear extremity is attached to the luggage rack and the holes in the luggage rack and the fender brace are pretty much aligned with little play (aka “room for adjustment”). Aesthetically, the curve of the wheel and tire and that of the fender should have the same center point (the axle) and a constant fender-tire gap. Nonetheless, with the mudguard moved and the very slight play in the fender support taken up, the rubbing disappeared. But wait; what about the horizontal mud flap and the hole in the fender? Should I be forced to ride my Brompton without its mudguard on the rear fender? Am I to sacrifice a dry back to the Vanity of the Tan Wall Schwalbes? The answer clearly is “no” – I have a Brompton with fenders, and I want to continue to have a Brompton with fenders.
RESOLUTION – Frame manufacturers who provide for fender mounting (with braze ons, etc.) forget that there has to be room between the frame and attached component (like wheels) for the fenders and their mounting hardware. Having struggled in the past with clearance between such mounting hardware and the frame bridge, I was somewhat equipped to address the Tan Wall-Brompton issue. The original stubby mudguard mounting hardware consisted of a round-head, hex drive bolt from the outside passing through a flat washer, the fender, the mudguard, another washer, and a 4 mil nut. Using the past solution, grinding off most of the bolt head and switching it around so the head was on the fender’s inside gave enough clearance for the tire to rotate freely. It is necessary to leave enough of the head to use a hex wrench for tightening or loosening in the future. Of course, a plain exposed nut would not do, so a substituted cap or acorn nut returned the mounting to functional acceptability. /
THE FUTURE – The tan is not worth the squeeze. At this point in the saga, the Brompton is rideable. But given the very tight non-rub clearance obtained and with fluctuations in weight, tire pressure, tire and wear, and the security of the fender mount nut-and-bolt arrangement, there’s a risk of the problem returning. For other Bromtoneers, variation in manufacturing of tires and bicycles or other irregularities may preclude the simple “solution” reported here. Bicycle shops and owners would be well advised to remember this lesson if they are fitting Brompton Schwalbe Marathon Racer Tan Walls or Brompton Schwalbe Marathon Racers. Sadly, were I to have the opportunity to reconsider this (rather expensive) acquisition, I would have stayed with the Kojaks – don’t mess with success.
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* Because all components and aftermarket customizations have to pass the “folded/unfolded” test, much of the Brompton is unique to it. Consequently, one cannot just throw on, say, a mirror and expect no issues. To allow a complete fold, one must test for add-ons like a bottle cage or lights.
Albany Bicycle Coalition 