TheSamba.com :: View topic - Thru-rod diameter

Fri Nov 20, 2009 10:55 am

Thru rods for a 10" over beam are $84 at Moore Parts. I was thinking about getting some threaded rod from McMaster and making my own, but don't know the rod diameter that is typically used. I found one post that said 1/2", but wanted to confirm.

Fri Nov 20, 2009 2:08 pm

I used 1/2" from Tractor Supply.

http://www.tractorsupply.com/home-improvement/hard...ed-3504231

Fri Nov 20, 2009 4:52 pm

zmotojason wrote: Thru rods for a 10" over beam are $84 at Moore Parts. I was thinking about getting some threaded rod from McMaster and making my own, but don't know the rod diameter that is typically used. I found one post that said 1/2", but wanted to confirm.

pacific customs has them for $55

Fri Nov 20, 2009 10:09 pm

Get these too :wink:

http://www.mcmaster.com/#6438k22/=4le8w4

Sat Nov 21, 2009 7:45 am

takotruckin wrote: Get these too :wink:

http://www.mcmaster.com/#6438k22/=4le8w4

Those came with my through rods from Moore.

Sun Nov 22, 2009 12:07 pm

takotruckin wrote: Get these too :wink:

http://www.mcmaster.com/#6438k22/=4le8w4

if you do buy the nut and rod separately, do be sure the threads match. the above posted rod is 1/2"-13, this nut is 1/2"-20

Sun Nov 22, 2009 3:13 pm

Since these thru rods are the only thing holding your trailing arms in the beam, I decided to go the chromoly route from Kartek. I would never run all-thread for thru rods... I wouldn't trust it. Again, this is a strength point that you do not want to fail. Stretching is an issue as well. That's why I opted for the stronger material. They are .500" thick with only an inch or so with threads on the end. These require the opposite end to be welded on (end bushing provided).

Sun Nov 22, 2009 6:09 pm

i have used all thread on the race car for 4 years now. i change it once a year, and have no problem yet :roll:

Sun Nov 22, 2009 8:06 pm

I'm running 1/2 inch grade 8 all thread from mcmaster. Seems to be working good.

Sun Nov 22, 2009 8:15 pm

I'm not very easy on my ride. I run fox 2.0 air shocks on the front with 1/2" all thread and rolled it bad 3 times this year. I actually bent 2 thing trailing arms and the all thread held up.

If you haven’t seen this video here is one that they held up on.

Mon Nov 23, 2009 9:42 am

lol, i laugh my ass off everytime i see that vid, lol. its amazing that it held up so well.

Mon Nov 23, 2009 5:01 pm

I remember Scott the Viking saying with the loads on the trailing arms, he would use rope with knots as through rods. Personally I used all thread on a previous car without issue and again on my current car (untested on current)

Mon Nov 23, 2009 7:33 pm

DONT wrote: I remember Scott the Viking saying with the loads on the trailing arms, he would use rope with knots as through rods. Personally I used all thread on a previous car without issue and again on my current car (untested on current)

The load is on the trailing arms as long as you're going in a straight line. Once you turn, the inside set of trailing arms is going to want to come out the end.

Mon Nov 23, 2009 9:49 pm

So it seems the general consensus is that all thread will work just fine. i mean if rolling a car over hard enough to bend the trailing arms, won't break them, they they must be fine, lol.

Mon Nov 23, 2009 9:52 pm

all-thread is fine and has been used for years... the torsion arms transmit their loads to the beam through the bushings and bearings, there is very little straight "out" force on the arms... think about how they were held on from the factory, with a grubscrew. :wink:

Tue Nov 24, 2009 2:01 pm

Thanks to all for the input. I am going with 1/2-20 plain steel threaded rod (58 ksi tensile strength) from McMaster. Total cost for the 2 rods and 4 collars is $32.62. If my caclulations are correct, the thread pullout should be

58,000 lb/in^2 * 0.1599 in^2 = 9274 lb

I would think that this is definitely higher than a grub screw.