Fastners

[SepticSkeptic]

I keep having issues with bolts breaking or backing out. Admittedly I should be more diligent in going over everything but I do use Locktite.

My latest casualty has been a snapped bolt under the rear rack, by the time I noticed, it the vibes and stress had caused my tail light assembly to crack and broke one of my Dirtbagz brackets.

I'm beginning to think a fastener upgrade and liberal use of safety wire might be in order.

Anyone know a source for high grade metric bolts with predrilled heads?

Most of the racing oriented stuff I've found is Ti or Al without the safety wire holes. I'm more concerned with strength than weight. I'd prefer not to have to find a metric jig and do my own drilling. I've heard that the aerospace industry might be a good source, but I haven't had any luck finding anything through them.

These look good, but they are in Europe, and they are expensive.

http://www.tastynuts.com/Products/stainless_steel_Flanged_Hex_Head_Bolts_Race_Spec

I figured one of you racer types can point me in the right direction.

 

[Slowpoke]

A properly loctited & torqued bolt should never come loose.

How are you preping the bolt before loctite? How are you applying the loctite? Which type of loctite? Proper torque?

The only bolts that have ever given me any trouble are the kickstand pivot mount bolts on my 07 TE 250. The factory never put enough meat for the stock bolts to grab, so they'll keep coming loose and eventually strip, until modified.

PS. I exclusively use the blue stuff on almost everything and high strength red on just a couple bolts.

BJ

 

[Creeper]

I keep having issues with bolts breaking or backing out. Admittedly I should be more diligent in going over everything but I do use Locktite.

My latest casualty has been a snapped bolt under the rear rack, by the time I noticed, it the vibes and stress had caused my tail light assembly to crack and broke one of my Dirtbagz brackets.

I figured one of you racer types can point me in the right direction.

I'm not a fastener or metallurgy expert by any stretch of the imagination, but...

Broken bolts can be due to any number of issues. Safety wiring a bolt does not eliminate failure but only serves to retain the bolt in place should it loosen or fail.
In some instances, a safety wired bolt can exacerbate a failure issue by preventing the bolt from "exiting" it's hole... and you don't know it's broken.

Safety wire is, in my experience, overkill on a motorcycle. Since the invention of Loc-tite, safety wire has very little reason to exist... but continues on because of it's use on aircraft (perfectly logical... particularly on helicopters) and it's use by pro racer mechanics as a "high bling value" feature.
Loc-tite, locking nuts, modern metallurgy and proper practices have pretty much all but eliminated the need for safety wire in most conventional applications.

A broken bolt can be caused by (to name a few off the top of my head):

1. Vibration frequency and amplitude. (Your rack, hanging out in space as a cantilevered element, probably has a high frequency-low amplitude vibration. Excess weight loading can also be a contributor to failure)
2. Component lateral sheer forces. (Forced fitment of parts for example)
3. Unanticipated component axial sheer forces.
4. A bolt of too low or to high a grade for the application. (Yes, too high a grade)
5. A poor quality or incorrect fastener for the application.
6. Excessive torque for the grade and size of fastener. (Quite possibly the most common reason for failure)
7. Re-use of a fastener combined with item #6 above.

There are more, but these are the ones that most relate to a motorcycle.

Best fastener practices are:

As stated by Slowpoke... "How are you prepping the bolt before loctite? How are you applying the loctite? Which type of loctite? Proper torque?"

• If you can't answer these questions correctly, then that in itself can be a contributor to failure.

1. Clean (dirt, grease and oil free) fasteners in good condition.
2. On a nut/bolt fitment, Loc-tite application in "length" equal to the bolt diameter and/or where it will contact the full length of thread engagement.
3. The correct Loc-tite for the application and torque value. Blue and Red Loc-tite are the most common. There are Loc-tite products for every conceivable application. For example... 222 Purple is a low torque, small fastener, harsh environment Loc-tite.
4. Proper torque is self-explainitory... if anything, most fasteners are over-torqued, which will contribute to failure.
5. If you don't own and use at least 2 torque wrenches, (small fastener, low value - usually 1/4 drive rated in in. lbs. and then the more typical ft lbs. 3/8" drive... usually peaking at around 80-100 ft lbs) then you will continue to have fastener failures.

• Use new and proper grade fasteners for an application where "the condition of the fastener may be suspect".
  
• Locking nuts wear out. Replace them after the 3rd use as a matter of course.
  
• When in doubt, always use a minimum of grade 5 fastener unless otherwise specified.
• In some applications, grade 8 may be overkill. Grade 8 fasteners have a higher axial failure strength, but may fail easier than a "softer" grade 5 fastener in certain lateral loadings.

(In the late 90s, Harley-Davidson had a front caliper bolt recall... the bolt was too hard and was snapping in extreme cases under a lateral loading... which is common for a brake caliper. The fix was a lower grade bolt)

Lastly but not leastly... have a read of this thread when you get a chance.

Oh yeah... I'm not saying that any of this applies to you... more of a general information post.

Ciao,
C

 

[SepticSkeptic]

How are you preping the bolt before loctite?

They are generally clean, else I just wipe them down, I don't go nuts with solvent or anything.

How are you applying the loctite?

I just dab the threads. Only place I don't use it is in places like the brass fuel tank inserts and stuff. Those are the ones I usually lose.

Which type of loctite?

Probably because I'm cheap and lazy, but I use only Red. I just use less of it if I think I might have an issue getting the bolt out later. Probably should get Blue, but thus far, I haven't had an issue.

Proper torque?

As far as torque specs, I just wing it. What ever feels right.

Gonna spend a few months on the bike toward the end of the year, beginning of next. Not gonna carry a torque wrench and a shop manual. I've got enough crap to pack on. I'm rolling solo for much of it so I guess I'm just being anal about trying to avoiding hassles.

The bolt that broke last weekend, broke about 2mm down from the head, not sure if it was sheared or not, probably was given the location. I figure is cost me about $150 in damage, unless the Dirtbagz guys gimme a break. I guess that's why I'm so irked about it this time. The one before that was my fault, due to a fall, I had to pay George to do his little weld it out trick. I'd just as soon spend a few dollars and putting quality stuff in failure prone areas. Places like pegs, rear rack, and what not, that I don't have to frequently remove, I'll just throw some wire on it too so it one less thing to worry about. Fire and forget, so to speak. Maybe just piece of mind.

I don't nurse it down the trail when I'm loaded up for long solo trips, nor do I intend to. The camping gear is all light weight backpacker stuff, heaviest being a 3.4lbs tent, but the weight comes from my tool kit, water, and extra fuel. I used to pack my tools kit in my back pack but it wears me down on long rides. I can shave some ounces of the tool kit with alloys but that about it. I'd been hoping that we'd have a larger tank by now, but I'm coming to the realization that it's not gonna happen any time soon.

I thought wiring up bolts was rather common, some racing organizations recommend it, didn't think it would be a big ordeal to find the pre-drilled hardware. Guess I was wrong.