I have a set of fenders on my bike and ordered a rear rack.
My rack arrived yesterday but where do I mount the lower rod?
My bike only has one boss on the lower part that the fenders are bolted to.
Only hardware with the rack is bolts for the upper and lower bosses.
go to Lowes and get some 5mm bolts in various sizes and some 5mm nuts. Some thread locking compound will help. I like to run the bolt from the inside out and hold the rack and fender with separate nuts.
If that is the case, I will have to get longer bolts for the bottom. The supplied hardware have only 1 inch bolts.
Make sure you add Loctite-Blue to the threads, too. Most modern bikes only have 1 threaded braze-on for both rack and fenders, so a longer screw is required. 1.5 inches should be enough. If you can fit a lockwasher put one on there, also. With Loctite-blue you'll get a solid grip for your fender/rack post combo. Better to go to an lbs for bike specific bolts than go to Lowes/HDP, HWSt because they, most likely wont have allen-key heads or will be soft metal. That's been my experience, anyway.
Sharing a bolt between rack and fender is quite OK but do put the rack stay closest to the bike frame, then the fender next, then a washer. Use bolts long enough to extend a couple of threads out the other side but not so far as to interfere with the chain.
If you want to use a nut the other side, nylock nuts are best, they stay but.
Lock-washers have a serated face and prevent turning. I used one on a bolt that self-extracted and it stays put now.