FlyRider

Newbie to cycling, so forgive me in advance for not knowing all the terms...

I am trying to attach a back rack (Ibera Bike Touring Back Rack) in order to carry luggage and also attach two metal legs to the front in order to support the weight on the underside of a milk crate. I noticed the back rack did not come with nuts for the bolts where the rack goes into the dropout eyelets...why is this? Wouldn't this make it more secure? I ask because my back rack will be supporting a lot of weight and I want to make sure it is as secure as possible. Also I was going to attach nuts to the bolts on the underside of the dropout eyelets on the front wheel where I am attaching the legs for the milk crate and I thought I don't want to do this if there's some safety reason that you shouldn't use nuts on the underside of the eyelets.

Thank you in advance for any help!

Andrew R Stewart 

Many rear dropouts have too little room to fit a lock nut behind the eye. The chain will often contact a lock nut (on the drive side) and cause a chain jamming. It all depends on the dropout shape, the cog size and the clearances your bike have. There's no way the rack company can predict what your bike's specific needs are so the hardware package with racks tend to be somewhat a experienced guess at what many (note- not all) bikes can/will use. But I'd say that about every other rack I've mounted needed some different hardware then what was supplied. Dropout eye thickness, eye threading (if any), other stuff like fenders rear brake design also impact what any one rack mounted on one bike ends up needing. Good shops have a ready supply of misc. hardware and often exchange bolts, add washers/spacers and do other fabbing to make racks fit best.

As to the need for locknuts on rack mounting points- a good idea if they fit without issues. But a well mounted, tightened and periodically checked rack mounting generally don't need (and don't get) locknuts. Andy

HillRider

You can buy the nuts (most likely M5x0.8mm) at any hardware of auto parts store. Most rack rely on the threads in the dropout holes and don't use auxiliary nuts but you can. Just be careful on the drive side that a bolt long enough to take a nut doesn't stick out of the inside far enough to hit one of the cassette cogs or catch the chain on the smallest cog. To avoid this interference you can thread the bolts into the dropout from the inside and let them stick out to the outside. Then slip the rack legs over them and add nuts on the outside.

andrewclaus

Ditto the above comments. I mount lots of accessories on touring and commuting bikes and I keep a small can of nuts, washers, and different lengths of screws. The only time I've used nuts on rack mounts is if someone stripped the braze-on.

I don't worry about the strength of the threads in a typical rack braze-on joint. All the load is in shear and the steel screw is plenty strong enough for that. I've never seen one fail in use, even in aluminum threads.

Andrew R Stewart 

Having worked in urban located shops for decades I've seen many broken and missing rack mounting hardware/bolts. VERY few frame problems like stripped eye threads but they can happen too. Most riders are a buy it and forget it when it comes to maintenance. And it's that periodic checking that is the trick to a long lasting and well working bike that is also reliable. If one lets the mounting bolts get loose the sway of the rack will at some point exceed the bolts' fatigue limits.

Not mentioned yet is the use of a thread locking compound (like LockTight) . It's been my feeling that this is the last resort and can sometimes cause future issues that are not realized until long after the deed was done. The usual reason for me to go to this step is because of frame threading issues. Rare for dropout eyes but unfortunately happens with the stay mounts, the current popular use of RivNut like fittings instead of a brazed or welded one results in the threaded insert being made of a softer (remember these inserts need to be compressed like a rivet to stay put) material and with a less long length of the threads too. The two common reasons for insert thread damage are over tightening (often with a too short bolt) and cross threading the bolt as it is installed. Andy

rumrunn6

I like to use a tiny bit of anti seize, just a trace. they still tighten just fine. don't want to struggle w/ a tiny rusted/frozen bolt & strip the head trying to remove it, or worse, breaking it off & having to drill it out! eek!

if the bolt doesn't seem to thread into the hole, there is probably a layer of paint preventing that. just use a skinny pocket knife or the tip of a steak knife to scrape out what you can, to get it started

cyccommute 

Or you can get a tap to chase the threads

The frame is the nut. If the hole in the frame isn’t threaded (common on many very old frames), then you need a nut to hold the bolt in place. But is very common to have bolts thread into a solid part like a frame without a backing bolt. Use a bit of thread compound if you feel like it but, honestly, I haven’t had too many bolts work loose on racks…and I often carry more than you can in your milk crate.

FlyRider

Can't thank yas enough...Sounds like as long as the dropout has a decent thread, not using a nut is fine. I may put one on the back rack that's carrying all the weight just in case, making sure the bolt isn't so long that it interferes with the chain.

Appreciate all of your help with this...

Crankycrank

There is also a low profile nut called a "jam nut" if you really need one and have limited space to fit. Stainless Jam Nuts : Bel-Metric, Metric Hardware, Metric Fasteners, Metric Bolts, Metric Nuts & Time-Sert Thread Repair (belmetric.com)

rumrunn6

familiar with those, due to having to deal with a broken bolt in my bathtub drain cover ... ;-(

thank you for the link, that would be handy to have in the bike shop