Rat Bike Zone BBS RSS

latest posts | picture of the day
 Back to all Messages  

Which wheel size is best between 16" and 18"?

March 25 2012 at 8:35 PM

Ray DeAtorose  (Login thestinkiestbob)

I have both 16" and 18" wheels for my bike. I am wanting to get rid of a bunch of shit, so I'm only keeping one set of wheels. Which ones would be best?

This is a thornier conundrum to fathom than you might think, for reasons some of which I will attempt to present here.

Firstly, the things that don't matter are tyre choices and cost. I have no trouble finding cheap-ass tyres and tubes for my bike in any size I want, and the only tyre "choice" I pay any attention to is how cheap they are. I've found both 16's and 18's to cost the same, so that aspect of this question doesn't matter.

I don't NEED a massive choice of tyres anyway for my bike- it's not a sports bike operating on the knife edge of performance. The only thing is that in my experience both front and rear wheels need to be the same inch size for the bike to handle properly.

Also I don't care what it LOOKS like. Fashion is not a deciding factor here, only cold hard facts.

Obviously 18" wheels and tyres would be heavier than 16" ones. The added weight of the extra spoke length and the extra rubber and rim materials would seem to be a detriment to fuel economy, not to mention using more of the Earth's resources in their manufacture.

But consider this: whereas the larger wheels might be heavier, they rotate slower to cover the same distance. This complicates matters somewhat.

Larger tyres , although heavier so more fuel hungry to move, would last longer due to rotating less to cover the same distance and therefore constitute a potential long term cost savings by having longer life.

Then there's the wheel bearing friction to consider. The faster rotating 16" wheels would be affected by proportionally more friction leading to a possible degredation in fuel economy.

But then there's the greater surface area of the larger wheels to be considered as a wind resistance factor, which would rob fuel economy through drag, thus negating any potential savings gained through longer tyre life.

Consider the gyroscopic effects of larger vs smaller wheels (as well as the weight differences between them). Is this in any way a factor in wheel size choice?

Larger wheels would mean that most of the bike was just a tad further away from the gravitational pull of the Earth than smaller wheels. How does this affect things over time? Would the slightly lesser actual weight of the bike be offset by the increased wind resistance of the larger windward surface area of the bigger wheels?

And all this is only considering foreward motion. What happens when we throw cornering into the equasion. Are there any advantages one size has over the other? Possibly so, when you consider the laws of physics (remember the gyroscopic forces mentioned earlier) and taking the above mentioned bearing friction, wheel mass, gravity, and wind resistance, and then consider the fact that at for instance a 45 degree angle (chosen as a random generality and not because I corner at 45 degrees) both wheel sizes would give identical lean angles, but the smaller wheels would mean that you (the rider) and the general mass of the bike were in fact lower to the ground. Does this matter? Or is a 45 degree angle pretty much identical in handling characteristics regardless of distance from the ground? Would the increased weight of bigger wheels help or hinder in such a situation?

What about stopping? Would larger wheels rotating slower (but with greater mass) make for better or worse overall brake performance and brake shoe life? Do the smaller, faster rotating wheels (with lesser wind resistance) stop better due to their lighter weight, or does the increased rotation speed negate any gains afforded by lesser weight and profile? Which wheel size is hardest on brake shoes and thus costlier in overall running expense?

What about rain? A larger tyre (potentially more "stable" in the wet due to more unsprung weight and slower rotation) may suffer somehow due to the fact that MORE rainwater will be clinging to the rotating mass. Perhaps the heavier wheels with greater surface area are actually LESS stable in the wet? Discuss.





 
 Respond to this message   
Responses