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  Stainless steel or grade 5/8 bolts on trailer?

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Author Topic:   Stainless steel or grade 5/8 bolts on trailer?
ShrimpBurrito posted 06-08-2002 12:31 AM ET (US)   Profile for ShrimpBurrito   Send Email to ShrimpBurrito  
Most of the bolts on my 1986 Cox trailer under my 15' Super Sport are rusted and need replacing. The U-bolts, the ones attaching the springs to the trailer, the ones attaching the rollers to the trailer, etc. It looks like the old ones are Grade 5, but they are so rusted that they could me Grade 2. I was thinking about replacing them with stainless bolts, but I understand that the tensile and yield strength of stainless is less than that of Grades 5 and 8. However, maybe the little weight of the Super Sport bouncing down the highway wouldn't be a factor. Any suggestions?
Jerry Townsend posted 06-08-2002 01:09 AM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
Shrimp* - the difference in the ultimate and yield between stainless and carbon bolts will not affect you - as your application is not loading those bolts very much. I would use the stainless bolts to eliminate the corrosion problem - particularily around a salt water environment.

Be aware, however that some stainless alloys will tend to rust but not to the extent of carbon alloys. Also, the grade 5 or 8 only indicates the strength of the bolt and does not say anything about the corrosion protection. ------ Jerry/Idaho

Tom W Clark posted 06-08-2002 01:50 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
ShrimpBurrito,

Hardware store variety stainless steel bolts (316) are comparable in strength to grade 5 bolts which is universally used on trailers for loaded conections (pivoting brackets and such). The U-bolts are not typically grade 5.

Stainless fasteners can be safely substituted for the fasteners you have now. In fact, some trailer manufacturers offer stainless steel fateners as an extra cost upgrade.

Apart from cost, there is no reason not to use stainless steel.

After 15 years of saltwater use I replaced ALL the bolts on the Calkins trailer under my Outrage. I choose to use grade 5 fatseners because it cost about half what stainless steel would have. All in all I felt the grade 5 fasteners held up rather well.

ShrimpBurrito posted 06-08-2002 01:52 AM ET (US)     Profile for ShrimpBurrito  Send Email to ShrimpBurrito     
Thanks, Jerry. I forgot to add in my post that the bolts in question are 3/8" and 1/2". The latter bolts hold in the springs and the tongue. On the original setup, the 1/2" bolts had nuts with a nylon insert. However, I can't find any stainless 1/2" nuts with an insert. Think a lock washer would protect from all the vibrations just as well?
ShrimpBurrito posted 06-08-2002 02:06 AM ET (US)     Profile for ShrimpBurrito  Send Email to ShrimpBurrito     
Cost is definitely a factor. I am replacing all the bolts after 15 yrs of service as well, and the existing bolts did hold up well, considering all the saltwater use. However, I was a bit surprised that my total was about $50, not including U-bolts.

From what I've found online, stainless 316 has a yield strength (the point at which it permanently deforms) of 65,000 psi. Grade 5 steel is 92,000 psi, and grade 8 is 130,000 psi. As far as boat trailers go, do you think there would be any point where stainless wouldn't be strong enough? I understand how these numbers are measured, but I don't have a sense of the order of magnitude of how much pressure is applied on these bolts......

Ed Z posted 06-08-2002 03:27 AM ET (US)     Profile for Ed Z  Send Email to Ed Z     
ShrimpBurrito, If you can't locate 1/2" lock nuts then I can think of two acceptable solutions... Use Loctite thread locker or use the old fashion method of double nut the bolts (may require a slightly [1/4" or 3/8"] longer bolt)...If you choose to use carbon bolts then try coating them with Never-seize... I find that this keeps rust at bay pretty well...
Ed Z posted 06-08-2002 03:27 AM ET (US)     Profile for Ed Z  Send Email to Ed Z     
ShrimpBurrito, If you can't locate 1/2" lock nuts then I can think of two acceptable solutions... Use Loctite thread locker or use the old fashion method of double nut the bolts (may require a slightly [1/4" or 3/8"] longer bolt)...If you choose to use carbon bolts then try coating them with Never-seize... I find that this keeps rust at bay pretty well...
Boston Marine posted 06-08-2002 07:28 AM ET (US)     Profile for Boston Marine    
If you use Loctite make sure you use 242 Blue
Tom W Clark posted 06-08-2002 12:52 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
ShrimpBurrito,

The nylock locknuts you describe are readily available. If you haven't already checked things out here: mcmaster.com , you might give them a look. They will have everything you want and sell it to you in any quantity.

An alternative to the nylock would be another locknut type called a Uni-Torque lock nut. These seem to be on all the trailers manufactured here in the PNW. They are essentially a slightly deformed nut which grips the bolt VERY securely.

Remember, you do not need grade 5 nuts on the grade 5 bolts if thatís the way you go. The really loaded bolts are loaded in shear.

When I did my trailer four years ago, I spent about $50 total including all the grade 5 bolts, standard grade U-bolts and Uni-Torque lock nuts. Going stainless would have cost me about $100.

Jerry Townsend posted 06-08-2002 02:32 PM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
ShrimpBurrito - lockwashers will work fine or double-nutting will work as well - if you choose not to use the nylon locks. However, in a salt water environment, the lock washers should be stainless, if available. Your loading application does not require high strength bolts - therefore grade 5,8 or stainless will work just fine. As Tom and others have pointed out - stainless will cost a bit more - but they will work. As I mentioned earlier, in a salt water environment, the stainless will hold up somewhat better. ---- Jerry/Idaho

DJS posted 06-12-2002 04:17 PM ET (US)     Profile for DJS  Send Email to DJS     
Shrimp Burrito:

Look at these two places for Stainless U-bolts and stainless locknuts

[url]http://www.performancetrailers.com/trailer parts.htm[/url]

http://championtrailers.com/SS_BOLTS_UBOLTS.HTM

DJS posted 06-12-2002 04:21 PM ET (US)     Profile for DJS  Send Email to DJS     
Sorry about the mix-up on the first url.

http://www.performancetrailers.com/trailerparts.htm

ShrimpBurrito posted 06-19-2002 04:22 PM ET (US)     Profile for ShrimpBurrito  Send Email to ShrimpBurrito     
Thanks everyone for the info! I'm fairly new to the area here, so I haven't been acquainted with the good local hardware vendors. Home Depot and Lowe's typically aren't good enough. Those websites are great! Finished the project last week. To prevent seizing on the stainless bolts, I applied a few drops of good 'ol motor oil. Worked like a charm.
lhg posted 06-19-2002 05:13 PM ET (US)     Profile for lhg    
I learned an important lesson on boat trailer bolts a few years ago, when I had to replace a broken spring.

Almost all boat trailers use 1/2" bolts for connecting the springs to the trailer, even though all springs and plastic bushings are designed for 9/16" grade 8 shackle bolts, fine thread. When I replaced all of these 1/2" bolts on my tandem trailer, I was shocked to see the wear on the loose fitting 1/2" bolts. Some were almost completely sheared though from abrasion. I replaced all with the 9/16" shackle bolts, and all my suspension squeaks went away, and there is a lot less play in the suspension.

ShrimpBurrito posted 06-19-2002 11:46 PM ET (US)     Profile for ShrimpBurrito  Send Email to ShrimpBurrito     
I had the same experience as lhg. Although it was over the course of 15 years, the bolts holding my trailer springs in place were sheared quite a bit too. This would be a good place to use grade 8 instead of stainless. In my case, however, I have a Cox trailer, to which they no longer make the springs. I had the choice of either having them made, or adapt a presently-made spring for half the price. I chose the latter.

Failing to replace old springs could not only have disasterous consequences for you and your boat, but old rusted springs no longer have their resilience. Thus, your boat gets beat up that much more while on the road.

Jerry Townsend posted 06-20-2002 01:04 AM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
Shrimpburrito & LHG - your experiences with 1/2 inch bolt replacements for 9/16 inch bolts is largely caused by the 'slop'. That is, a bolt that is loose will cause the effective load to be about twice the actual load. It is called impact loading.

Many may recall that on cars and trucks in the 40's and 50's, bushings were installed in the leaf springs - to eliminate any slop. Now days, we don't have the bushings - must have cost too much.

But that is also the reason that on every trailer that I have made, all shackle bolts are drilled (axially and at the midpoint) and with a grease zerk installed. Eliminates a lot of problems. ---- Jerry/Idaho

ShrimpBurrito posted 06-20-2002 01:11 AM ET (US)     Profile for ShrimpBurrito  Send Email to ShrimpBurrito     
Jerry - my springs did have nylon bushings which the bolts went through, but the impact loading wore completely through them. I'm not complaining at all; I'm completely happy with the setup faithfully performing for 15 years and 50,000 miles. My springs will rust to the point of needing replacement before those bolts will come anywhere near failure. However, your suggestion sounds like it would provide a much extended life for those launching in fresh water.

And...uhhh....I don't remember those bushings on cars and trucks made in the 40's and 50's. :)

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