Originally Posted by
Doug5150
Yea, but....
if you switched to downhill-width rims on that same bike, and used those same tires--you could run them at a much lower pressure than you are now, and get better traction and better riding comfort.
Yea, but...
If I switched to downhill-width rims on that bike, it would make riding
uphill much more difficult because I would have to lift that weight up a hill. The air in the tire also serves another purpose: to protect the much more expensive wheels from damage during impacts.
I've never found traction to be much of and issue either. I'm not talking about pumping mountain bike tires up to 80psi and going off-road but at 40 to 45 psi on the rear, the bike climbs just fine and with lighter wheels, it climbs better than heavy wheels.
Originally Posted by
Doug5150
1) The only reason to use fat tires at all is to inflate them to lower pressures to absorb road shock,
No that is not the only reason to use wide tires. They are there to protect the rims from impact as well. Modern mountain bikes have suspension systems to handle absorption of road shock. Even without suspension, the rider absorbs more of the road shock through their legs and arms than the tires will.
Originally Posted by
Doug5150
2) fat tires on narrow rims must be inflated fairly high to avoid flexing laterally on the rim, so-
Running super low pressure, in my experience, result in poor handling because the tires wallow through corners and feel slower on straights. Running low pressure also risks "burping" or blowoff in addition to rim damage. Both have a huge impact on your overall speed.
Originally Posted by
Doug5150
3) if you use fat tires on narrow rims, all you end up with is a very heavy, very hard tire. You might as well just put a narrower tire on and get the same hard ride, with less weight.
Personally, I don't consider a 2" mountain bike tire at 40 to 45psi to be "hard". The tire is heavier than a narrow tire but a narrower tire in a mountain bike application has to be run at a higher pressure to avoid wheel damage.
Additionally, wider rims result in more rotating weight which is the bane of a cyclists existence. Fat tires on a wider rim aren't any lighter than fat tires on a narrow rim...just the opposite, in fact. You may gain traction...a claim I doubt based on decades of experience...but you have to expend more energy to get the heavier wheels up a hill.
Originally Posted by
Doug5150
People prefer to be told that "you can use any width of tire you want on any rim" and it will function, but it's poor advice.
Wider tires work best with lower inflation pressures, and you can't do that with narrow rims.
Define "best". I've been using narrow rims with wide tires in mountain bike applications for 30 years. The bike goes up and down hills without any more difficulty than others using wider rims.
And people don't "prefer" to be told much of anything. I tell people that you can use just about any width of tire on just about any rim you want because,
in my experience, you can.