Suspension Bolts

[Dave Forster]

There are a number of bolts on my car that appear to be longer than optimal. For example, in the attached picture, I am thinking of replacing the two wishbone bolts with ones which are shorter and installed in the opposite direction - as it is, removing the bolts requires removing the shock bracket from the body. If they were reversed then the bolts could be removed without disturbing the shock bracket.

Am I missing anything here? Is there any reason I shouldn't use shorter bolts (as long as 1.5-3 threads are still showing past the nut) or installed in the other direction?

 

[Fran Hall RCR]

Dave ,
the bolts are the correct length to make sure that all the suspension loads are on the shank of the bolt and that no threaded area of the bolt is carrying any critical load.

Feel free to shorten the threaded area that seems longer than you would but DO NOT install a bolt that carries load on the thread.

You may also notice that with the orientation of the bolts, that should, by some miracle the nyloc nut fall off ,the bolts cannot actually fall out as they are somewhat captive by their orientation and the proximity of the other brackets and bolts.

 

[Dave Forster]

Makes perfect sense to me!

Assuming these are already the shortest bolt that keeps the shank under the loaded areas, the only option to go shorter would be to cut them down, which would mean the cut ends would be unplated and exposed to corrosion . . . think I'll just leave well enough alone.

 

[mark b.]

I am not suggesting it, but I have shortened bolts like above without any rusting problems. the Grade 8 stuff is pretty hard and doesn't easily rust. Fran makes a good point, watch the shank length. I've used longer bolts to make the shank exit the nut side then installed washers to cover the shank.

 

[Dave]

You could always use -an bolts to get the shorter length and keep the longer shank without having to cut them.

 

[Roger Reid]

You could always use -an bolts to get the shorter length and keep the longer shank without having to cut them.

Dave, could you give some references to a "-an bolt". I tried looking up this description without luck.

 

[Jack]

Army/Navy spec, found here:
Search Results from Aircraft Spruce

 

[Roger Reid]

Thanks Molleur

 

[mark b.]

Here's a surplus supply house if you'd like to compare pricing.

Homepage

 

[Garry 20 B]

I used stripper bolts, machined size for the hiem joints and only the thread sticks out the end of the U bracket.

 

[Dave]

Dave, could you give some references to a "-an bolt". I tried looking up this description without luck.

Jack beat me to it. They are superior to Grade 8 bolts and are available in more choices of grip length. They can also be had with safety wire holes pre-drilled in the head and/or the shank. Not cheap.

AN BOLT SELECTOR from Aircraft Spruce

 

[Frank Clark]

Another vote for -AN. The AN bolt selector above will help you order the desired lengths. I opted for drilled and used locking castle nuts with cotter pins.

 

[Cliff Beer]

Personally, I'd put a Grade 8 washer under both the head of the bolt and also the nut, then double nut with a non-locking nut and then the nylock nut. Not a lot of excess thread will be showing after doing all that.

Either that, or use a lock wire and shorten the bolts a bit yourself.

Grade 8 fasteners for all suspension pieces!

 

[Fran Hall RCR]

We use Grade 8 bolts on all of our products in any critically loaded area...in fact 95% of the fasteners on the cars are grade 8 period...better safe than sorry

 

[colin artus]

Can't you get 12.9 capscrews in the US?

 

[Jack]

Yes Colin. Multiple sources available.

 

[Fran Hall RCR]

12.9 is Metric format ...and the cars we build are all standard hardware and rod ends.

 

[Dr. David]

Most of you probably know this, but related to this thread, in my opinion, is the use of Torque Seal. You can buy it at Pegasus Auto Racing, eBay, and multiple other places.

It has relatively little to do with torque, and it doesn't seal anything, but what it does do is it allows you to easily check to make sure that your bolts and nuts are staying where you put them. You simply paint it on after your suspension (or other) hardware is tight, and it hardens to a brittle film. If there is any loosening of the hardware, you will easily be able to detect it. It also saves you from going around and over-tightening everything periodically, (something I have done.) If the fastener has become loose, you will know it at first glance. If it hasn't, leave it alone and let it do it's job. For new construction, you can do a "shake-down," re-torque, and then apply.
Just my opinion.....
It comes in multiple different colors, as if that's important.

Loctite Blue is important.

Safety wire is the best, but it is easy to run out of 1/16" drill bits to drill your Grade 8 and AN- hardware.

 

[John]

An old habit that was taught, no drummed into me when doing my apprenticeship was to put a dab of paint on torque specific bolts, 1/ so you know you've already tightened them, and 2/ it makes a seal, easily checked by a quick visual if anythings coming loose, now days I use a white paint pen. you don't need any fancy specific do dad.
and totally agree with Fran , never, ever have a treaded section of bolt under shear, that's what the shank is for.
cheers John

 

[Jack]

Ditto on the paint pen. Easy..