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.

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