I assume you're referring to this page? Seems like it's explained fairly well; better than I could do anyway. On a 14mm rim I don't think I'd go wider than 32; 28 would be better.

[h=2]Width Considerations[/h]Although you can use practically any tire/rim combination that shares the same bead seat diameter, it is unwise to use widely disparate sizes.If you use a very narrow tire on a wide rim, you risk pinch flats and rim damage from road hazards.If you use a very wide tire on a narrow rim, you risk sidewall or rim failure. This combination causes very sloppy handling at low speeds. Unfortunately, current mountain-bike fashion pushes the edge of this. In the interest of weight saving, most current mountain bikes have excessively narrow rims. Such narrow rims work very poorly with wide tires, unless the tires are overinflated...but that defeats the purpose of wide tires, and puts undue stress on the rim sidewalls.

Georg Boeger has kindly provided a chart showing recommended width combinations:

[TABLE="class: grid, width: 1"]

[TR]

[TH="colspan: 15"]Which tire fits safely on which rim?

[all dimensions in millimeters][/TH]

[/TR]

[TR]

[TH][/TH]

[TH="colspan: 14"]Tire width[/TH]

[/TR]

[TR]

[TH]Rim width

(interior)[/TH]

[TH]18[/TH]

[TH]20[/TH]

[TH]23[/TH]

[TH]25[/TH]

[TH]28[/TH]

[TH]32[/TH]

[TH]35[/TH]

[TH]37[/TH]

[TH]40[/TH]

[TH]44[/TH]

[TH]47[/TH]

[TH]50[/TH]

[TH]54[/TH]

[TH]57[/TH]

[/TR]

[TR]

[TH]13[/TH]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[/TR]

[TR]

[TH]15[/TH]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[/TR]

[TR]

[TH]17[/TH]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[/TR]

[TR]

[TH]19[/TH]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[/TR]

[TR]

[TH]21[/TH]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[/TR]

[TR]

[TH]23[/TH]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[/TR]

[TR]

[TH]25[/TH]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #FF1111, align: justify"] [/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[TD="bgcolor: #11FF11, align: justify"]X[/TD]

[/TR]

[/TABLE]

Note: This chart may err a bit on the side of caution. Many cyclists exceed the recommended widths with no problem.