Radius rod mount bolts

butch27 · May 10, 2013, 10:59:23 PM

I've been running grade 5 bolts on the front radius rods where they mount to the frame. It now looks like a little bend!! Should I go grade 8? Any opinions?

phat rat · May 10, 2013, 11:34:32 PM

When in doubt make it stout

unklian · May 10, 2013, 11:45:30 PM

What diameter did you use ?

wayne petty · May 11, 2013, 01:17:36 AM

hmm.. in many years of automotive work..

i have never seen a factory installed grade 5 bolts anywhere in a suspension component or attachment..

i have wondered about the bolts hanging out unsupported with a rod end ... wondered if a something like a wall sconce would work if if it was designed properly so the bolt would have support top and bottom.. add some decoration to the fender rail.. and support the rod end bolts top and bottom.

i will have to do some drawings perhaps to show what i am thinking about... and i am not thinking a decorative sheet metal device.. i am thinking something is either multiple layers of steel welded and ground, then properly prepared for chrome plating by baking the hydrogen out of the steel just prior to chrome plating.

Monte.b · May 11, 2013, 04:15:37 AM

I havnt been on here for a while so i hope you dont mind if i post a reply,dont mean to be rude ,As far as the bolts go id go grade 8 for sure ,i use all grade 8 bolts for everything on the rods ive built ,except the bolts on the seat belts ,our transport dept like us to use grade 5 there ,ive no idea why ,hope to post a bit more in the future ,regards ,Monte,b

butch27 · May 11, 2013, 10:17:53 AM

From everything I've heard - grade 8s are STRONG -But grade 5s are TOUGH? There is no chrome plating involved here. Just the bolt through the R/R and into the frame bracket. !/2" bolts.

enjenjo · May 11, 2013, 11:48:22 AM

Quote from: "butch27"From everything I've heard - grade 8s are STRONG -But grade 5s are TOUGH? There is no chrome plating involved here. Just the bolt through the R/R and into the frame bracket. !/2" bolts.

A common misconception. I did an engineering study on bolts one time, and found that a grade 5 bolt would bend, and break, before a grade 8 bolt would even bend, and still not be close to breaking. A grade 5 bolt will bend further than a grade 8 bolt before breaking, but the forces involved are much lower than the ones on a grade 8 bolt breaking.

The only place I see grade 5 bolts used in suspension parts is in some racing, where they want the pieces to come loose to lose energy in a wreck.

Another thing to consider, if the threaded part of the bolt is in shear, then effectively the bolt is the size of the root of the thread, rather than the bolt diameter. In other words a 1/2" bolt with the threads in shear is effectively a 3/8" bolt.

In your case I would use a grade 8 bolt, and make sure the threads of the bolt are not in shear.

oj · May 11, 2013, 04:20:27 PM

I'd be looking for why the bolt is bending...there shouldn't be any load on your front end that would bend a bolt, esp on a radius rod. I suspect you replace grade 5 with grade 8 and something else will break or bend.

butch27 · May 11, 2013, 11:43:20 PM

The threads of the bolt is not in shear. I'm looking closer and it looks like the bolt is only angled what the Hiem joint total movement is. Weird ??

oj · May 12, 2013, 12:08:38 PM

Interesting, can you post a picture?

butch27 · May 14, 2013, 10:45:38 PM

I'll try.

Glen · May 15, 2013, 12:13:59 AM

take a look at NAS bolts when they are critical....

here is a quick link with a chart

http://www.rjracecars.com/Nas-Bolts-131019-and-620720-Prodview.html

Monte.b · May 15, 2013, 05:09:59 AM

Quote from: "butch27"The threads of the bolt is not in shear. I'm looking closer and it looks like the bolt is only angled what the Hiem joint total movement is. Weird ??

In Australia they wont let us use Hiem joints ,never figured out why as they are used on lots of other applications even on heave machinery

PeterR · May 15, 2013, 05:57:28 AM

Quote from: "Monte.b"
In Australia they wont let us use Hiem joints ,never figured out why as they are used on lots of other applications even on heave machinery

Because their life is so short on a road going vehicle. They are only satisfactory when used in a very clean environment or replaced frequently.

Monte.b · May 15, 2013, 07:55:19 AM

Quote from: "PeterR"
Quote from: "Monte.b"
In Australia they wont let us use Hiem joints ,never figured out why as they are used on lots of other applications even on heave machinery

Because their life is so short on a road going vehicle. They are only satisfactory when used in a very clean environment or replaced frequently.

Thanks mate,nice to see a friendly face here ,i must say ive seen them used on farm machinery for years and not real clean farms too ,seem to last ok there ,I know you have the knowledge so could you explain to us common folk the problem with using these and why the bolts are bending on this blokes front end ,regards,Monte.b