How much fender do you need?

[73Eldo]

Shopping for fenders for my 29er. Not a lot of choices seems that most people buying fenders are running fairly narrow 700c's. How much cover do I need to keep most of the muck off me and my bike? Plans for this bike is winter paved trails and streets so likely a mix of salt, slush, puddles, and some snow.

I notice even 'full' fenders come in different lengths. How much below 9 o'clock do you want the front to come down? Very few seem to come below 9. Also see that about half the rear fenders end around the seat stay? How much difference does it make going all the way down to the bb? I don't have much clearance there now without the fenders so maybe its fine if they end at the seat stay? I have a rack and trunk bag do I need more than that? Or won't I gain much?

[oledave]

I prefer fenders to be 1" wider than the tire, which gives an 1/2" over hang on each side of tire. The front tire sprays water from the back at about a 45 degree angle, so you want it to be as low as possible without it hanging on stuff, and it is a good idea to have a mudflap as well. The front of the front tire sprays water up and then you ride into it, so you need the fender to come down far enough to stop that. The back fender coming all the way down to bb will keep the chain a lot cleaner, but if you don't have room you don't have room.

[73Eldo]

Those 75's will get me pretty close, that's almost 3". Current tires are 2.6 but my studded ones and other summer tires are 2.35 so that will get me that 1/2" plus on each side.

How much clearance do you want between the tire and inside of the fender?

[Retrorockit]

I like to run the fenders almost right down on the tire for rainy conditions, but with snow that may not work. If the fender wraps down around the side of the tire it doesn't need to be much wider than the tire. For group riding the rear fender should be very long to protect people following you. If it's much shorter than the rearmost part of the tire it starts to throw water forward onto your back. Mudflaps really do help but your feet on the pedals will still get soaked by the side splash coming up from ground level.