What size 29er tyre can I run on a 700c wheel with an inside rim width of 19mm? Would a 29" x 2.3 tyre be too wide or would it just about work ok?
29er and 700c are BOTH ETRTO 622. 622mm is the bead seat diameter, which is measured the same way as automotive and motorcycle wheels and tires - which use inches instead of millimeters.
19mm inside width 622 rim with a 58-622 tire should be okay at low to moderate tire pressures (less than 50 psi). I have seen 50mm tires on 15mm inside width rims for mountain bikes.
If you are riding predominantly on the street, you'd want a much wider rim for that tire width, more than 29mm inside width.
Thank you for your reply. Regarding your last sentence, 'If you are riding predominantly on the street, you'd want a much wider rim for that tire width, more than 29mm inside width', did you mean wider than 19mm or 29mm? What would be an appropriate inside rim width for a 2.3" tyre?
For the street; my experience is that you have much better control and ride with a rim that has an inside width of more than half the section width of the tire. For example, on my commuters, I have Velocity Dyad/Aeroheat (same extrusion) 18mm inside width, with 28-622 and 32-559 tires on the front of the two bikes. On the rear are 35-622 and 40-559. The 40mm is my limit for pure street on a 18mm inside width rim.
You can run wider tires, but you will start to get "floppy" handling. Off-road, things are different, there are wide low pressure knobbies that are designed to run on narrower rims.
Also, on the street, consider narrower front than rear tires; I find a 4:5 ratio works well for me.
Off road, especially sand, loose dirt and mud; a wider front than rear works better.
Where you intend to ride has a huge impact on the optimum choice of tire and rim. Can you ride off-road optimum on the street - Yes, will your handling and rolling resistance by good - No. The other direction is much worse - slicks are ideal for pavement, but are not rideable in mud or sand. They are fine on hard packed dry dirt.