Originally Posted by
blueoceanbill
I'm bringing the road bike out of retirement, for out of town rides; since I've been exclusively riding my mtn bike over the past twenty years and want to get back into the road saddle. I'm looking for a scientific techical article or review paper comparing the various tire sizes. I've got 700x23 on her now and need new tires; so I am looking for a technical study to help make a better decision. Thank you very much and 'bike on'.
Silca's Journal page offers a great series of posts about tires:
https://silca.cc/blogs/journal/11839...-we-got-to-now
https://silca.cc/blogs/journal/11861...tiffer-harsher
https://silca.cc/blogs/journal/part-...re-and-comfort
https://silca.cc/blogs/journal/part-...ogether-so-far
https://silca.cc/blogs/journal/part-...previous-works
https://silca.cc/blogs/journal/part-...-and-impedance
https://silca.cc/blogs/journal/part-...d-aerodynamics
Jan Heine has done some fairly extensive tire testing, although only his summarizing blog posts are available for free.
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In a nutshell.
There are two major factors on tire rolling performance: Energy loss from hysteresis as the tire deforms as it rolls, and losses from the tire failing to act as suspension for the bicycle.
Hysteresis losses go down as PSI goes up, since the tire deforms less. Tires that are stiffer (i.e. due to thicker tread, beefier casing, or puncture protection layers) tend to lose more energy from deformation, and thus need to be run at higher PSIs. Hysteresis losses also
appear to go down as tire width increases, although since wider tires are typically run at lower PSIs, the real impact of tire width is pretty small.
When a tire is transmitting surface irregularities to bike and rider, energy is being wasted. This can be fought by running the tire softer. Wide tires are better at being run soft, so if the pavement you're riding on sucks, I'd definitely err wide.
These two effects create a balance. You want to run your tires stiff so that they don't deform much, but you want to run them soft so that they don't transmit irregularities. Nice non-stiff supple tires have a significant advantage here; they can be used at low PSI to offer good suspension without suffering much from hysteresis losses.
Wider tires have a degree of natural puncture protection in that the lower pressures aren't as aggressive in forcing things through the tread, although if your roads are covered in particularly sharp stabby things, you might require thick tires anyway.
There are a couple other factors. Wider tires will slightly worsen the aerodynamic profile of a bicycle, and they'll add a bit of weight out at the rims. Also, obviously you can't choose tires wider than what your frame and brakes (and fenders or rack or whatever is on your bike) have clearance for.
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Originally Posted by
blueoceanbill
I tried small performance tires on mtn bk thinking it would be faster, but was really negligible overall difference. I'm thinking I should get the largest tire that will fit rd bk which might duplicate that scenario; but is contrary to trend beliefs.
Tire width has very little overall speed performance impact on smooth roads, which is why tires are trending wider. I have
53mm (!!!) high-performance road tires on a drop-bar conversion of an old Stumpjumper, and, although it's a very heavy bike on the whole, it performs basically identically to my skinny-tired road bikes on level pavement.