I am sure this is a stupid question but...
 

I am going to put a rack on my MTN bike for a trek. I was looking at the threaded holes where you are to mount and they seem to be different sizes? Are they supposed to be?


Picture "1" is the seat stay where you can mount panniers or a fender and they are the standard size.
Picture "2" and "3" are the threaded spots on the axle area where you would attach the bottom portion but they are not the same size. I assumed they would all be the same size. OR because there is paint in the threads when the bike was painted this is causing the issue? I don't want to get my rack and have issues with hardware.


Are they different sizes?


Sorry if this is dumb, I feel kind of dumb inquiring about it.
thanks,

it's probably paint, those are almost always 5mm bolts

I thought so....now do I just thread the bolt or go to my LBS and have him use his reaming tool and get the paint out that way? Don't want to mess up the threads!!

you can get a cheap tap and die set to clean up the threads if you want to do it yourself.

Since you bought i t a bike shop, cleaning out the threads is something they should do for free, since paint in the threads might be considered a defect covered by warranty.

Or you can buy a cheap tap, and use it carefully, but keep in mind that if you break the tap in the hole or otherwise mess this up, THAT is on you and won't be fixed for free.

One safe, cheap way to clean the threads is to grind a notch up the first few threads on a quality 5mm bolt that you pick up at the hardware store. Thread it in by degrees, backing off and cleaning the debris and repeating until you're through.

First pic looks like it already has a bolt in the hole, why not just try to get it started in the dropout holes? It'll probably thread right in.

This was my doing messing around, but when it got really tight I stopped fearing the damage I might create.




MY LBS will do it no problem. They are super good, treat me well. I will just have them do it.


thanks all!!

thanks but I am to chicken to try it. I am sure its not a big deal but I don't wan to mess it up....they will do it for nothing so I will let them mess it up! :roflmao2:

The most common sizes for these attachment points are 5.0mm x 0.8mm and 6.0mm x 1.0mm. I'd be surprised if yours are anything different.

for those who wish to take the advice and use a tap, be sure it is one for a blind hole!