My journey to the darkside, episode 2

…is ongoing but has it’s share of pitfalls. The Kumho 205-60VR16 was the proper diameter to correct the speedometer, but was just a little too big in diameter when 2-up with an insufficient preload setting. The tire rubbed on the amplifier box (which is molded into the inner rear fender on the ’06 and up wings) and rubbed a hole it it. Not OK. Even though the speedometer was correct, which is a nice bonus, the potential damage to expensive electronics from water incursion is not worth the risk.

Plan B – I ordered and installed a ContiProContact SSR 195/55VR16 tire. This tire, for all intents and purposes, matches a factory MC tire for diameter and width. Installing it was simple and even without weights I have been unable to detect an out-of-balance condition. Knowing that an even-slightly-out-of-balance rear tire can cause the infamous “wobble”, I ran up to 60mph and took my hands off the handlebars and let the bike coast down. Not a hint of a wobble at any speed. To the collective dismay of the naysayers, there was no fiery crash caused by running a car tire on a motorcycle. This tire will be on the bike for a long time – probably twice as long as a new MC tire, if other’s experience is any indication.

UPDATE – September 30 – I got back from my trip to ride the mountains in north Georgia, east Tennessee, west North and South Carolina and the Conti was flawless. Not a slip during the trip, and I did remove some metal from the footpegs. On the Cherahola Skyway, we were in the clouds at about 2000 feet on up to 5300 feet, with the resulting poor visibility and wet pavement. Not a slip from the Conti – it just held the road like a good tire should. When we stopped for gas, the rider behind me told me that the tire tread was almost flat on the road the entire time. When I tell you that we were wasting no time, believe it. Our group rode almost 500 miles through the mountains in about 12 hours of riding. If you’ve ridden in those mountains you know that is not a slow pace.

My journey to the darkside…

…is not yet complete – on the Goldwing, of course. For those of you not familiar with the meaning of the phrase, in the Goldwing community it refers to riders that are using a car tire on the rear wheel rather than the more conventional motorcycle tire. The Goldwing rear wheel is a 6″ wide, 16″ diameter tubeless wheel that is just begging for a car tire to be mounted.

Why, you ask? Well, there are many reasons. Here’s just a few

  1. Available in Run Flat
  2. Longer lasting
  3. Doesn’t delaminate
  4. Doesn’t explode
  5. Quieter
  6. Better traction in dry conditions
  7. Better traction in wet conditions
  8. Better traction in snow/slush
  9. Better performance on dirt/gravel
  10. Smoother ride
  11. Higher load capacity
  12. Capable of performing with lower PSI
  13. Runs at lower tire temperature
  14. Costs less
  15. Better balanced (fewer weights required, if any at all

That’s quite a list, isn’t it? Pay special attention to the advantages I highlighted. If the motorcycle tire manufacturers decided to build a tire that addressed these issues they would sell as many as they could make. But, economics enters into the picture. The market for motorcycle tires is a small fraction of the market for automotive tires. Given today’s litigious society, I suspect that a revolution in motorcycle tires for touring bikes is not going to happen anytime soon.

I purchased a spare rear wheel for my Goldwing and mounted a Kumho 205-60HR16 non-run-flat tire on it. I swapped it for the wheel with the Bridgestone cycle tire on it. The first difference I noted is that the bike is slightly taller, as the Kumho tire is a larger diamater tire. I expected this and the choice of a larger tire was intentional. The Goldwing (all motorcycles, as a practical matter) have a built-in speedometer error of 6-10%. When the speedometer says 60mph, a gps will show your true speed at 54mph. Of course, the odometer is off as well, so mpg calculations are based on “shorter” miles. The larger diamater tire corrects the speedometer to within a tenth of a mile per hour. Now, when the speedometer says 60, your speed is 60 mph – just as it should be.

While I’m on the topic, virtually all speedometers are incorrect. It’s just that most drivers aren’t aware of how far off they actually are. With the increased use of portable gps devices that display groundspeed to within a tenth of a mile per hour, more drivers are starting to realize the problem. Why do you think that built-in gps devices don’t display groundspeed? One reason is that drivers would demand that the manufacturers fix the broken speedometers. Consider what this does to warranty work. If the speedometer/odometer is off by 10%, your brand-new 50,000 mile warranty expires in 45,000 actual miles.

Consider what this error does to mpg calculations too. More people are paying attention to mpg these days and if the auto/truck/cycle manufacturers can have you calculate a higher mpg than you’re actually getting, they win. I’m not trying to say that correcting the speedometer/odometer error is a magic pill that will fix all mpg-related problems, but at least you’ll know what mpg you are really getting, not some number that’s based on a “short” mile and really doesn’t mean anything.