[5mm bolts]

[farmer6re9]

Greetings,

I am develoing a bike accessory and have a technical question regarding the 5mm threaded holes and bolts located throughout the frame.

The frame I am working with is 7005 aluminum. I do not know if this is the same material used for the reinforced areas around the threaded holes. The factory 5mm bolts are virtually weightless and I believe they will fail under load or if too much torque is applied tightening.

Questions:

1) What is the best GRADE of bolt I can use without stripping the threaded holes?

2) What is the maximum inch-pound torque for these bolts and holes on a 7005 aluminum frame?

Thanks

 

[davidbod]

Originally posted by farmer6re9
Greetings,

I am develoing a bike accessory and have a technical question regarding the 5mm threaded holes and bolts located throughout the frame.

The frame I am working with is 7005 aluminum. I do not know if this is the same material used for the reinforced areas around the threaded holes. The factory 5mm bolts are virtually weightless and I believe they will fail under load or if too much torque is applied tightening.

Questions:

1) What is the best GRADE of bolt I can use without stripping the threaded holes?

2) What is the maximum inch-pound torque for these bolts and holes on a 7005 aluminum frame?

Thanks

Check out this info from Park Tool. Should give you an idea of what you need. Looks like somewhere between 45-70 in lbs.

http://www.parktool.com/repair_help/torque.shtml

Cheers,
David

 

[farmer6re9]

...Great link, very informative. Those charts will come in handy.

I did not see any references to frame threads. The stock bike has nothing mounted with a bolt 'threaded' directly into the frame. The rear disc rotor is mounted to the frame, but with a 'pass-through' style bolt...essentially a 'clamp'.

I am referring to the holes in the standard locations for racks, pumps and liquid containers. I saw one reference to M5 bolts for the disc rotor to hub at 18-35 in-lbs. The unit I'm affixing to the frame will require (in my non-engineering opinion) at least 50 in-lbs in each of four locations; the rack bolts below the seat and above the rear wheel mounts. This device will also incorporate a fifth 'stabilizer' mount at the seat post.

I have no experience with aluminum frames at all. I guess what I'd like to know is how hard can I crank on the stock aluminum bolts before they snap?

How tight can I crank a stainless, brass or steel bolt before it strips the threads.

At this point I'm leaning towards brass bolts with a bit-o locktite and 50 in-lbs, unless someone with intimate knowledge of 7005 aluminum frames advises against it.

Thanks,

farmer6re9