MisterRisky

I am in the process of replacing my control arm bushings. I was thumbing through the workshop manual last night and I was surprised to read that the manual recommends replacing bolts 21, 22 and their associated nuts and washers if the bolts are removed. I understand why head bolts have to be replaced if removed, but I don't understand why these bolts need replacement. Anyone have some wisdom they can whip on me?

Thanks!

Texas993

When RUF Dallas replaced my control arm bushings a couple of weeks ago, they did not replace the bolts. If that helps...

You will enjoy the difference these bushings make.

I drove my 993 on a trip this week and it has bad bushings. It was very irritating, especially since my 964's bushings create crisp steering with no wobble. The 993 will get repaired soon.

MisterRisky

I'm doing a full suspension refresh: Control arm bushings, Bilstein HD's, H&R springs. I fully expect to wet myself with joy at the results.

darth

It's likely recommended to replace them as they "wear out of round" just as the bushings have worn although not as much since they are a harder material. If you replace the perfectly round bushings and use the worn bolts there will be some slop which may or may not be tolerable. It's also a critical component that you don't really want to fail when you're driving considering what they're worth.

Hope this helps
Bill
90C2

elbeee964

JD-

Your suspicions are correct: two totally different things. Head bolts are an entirely tension-loaded fastener. These plain-shank bushing bolts are (almost) entirely shear.

Offhand, absent any obvious, spooky wear/cracks/corrosion/gouges/or bird droppings along those shanks, I couldn't see why (in my own garage) I'd replace except the usual CYA of "Porsches are exceptionally hard-worked, and therefore have exceptional R&R lists."

Do a search under "bushing" + "bolt" + "failure", and absent any precident, I'd posit, -- live life large & on-the-edge, man -- reuse those bolts if you wish.

Why? Because. You. Are. Mr. Risky.

Oh, and give ear to any race/wrenchers who pipe in -- guaranteed you'll hear from them if this bolt is an abnormally sensitive link. ciao.

-Lonnie

ABQ Slim

MisterRisky

Good point Lonnie... I AM Mr. Risky!

Actually in my professional life I am a risk economist, believe it or not. I think I will inspect the bolts, ensure round, and probably reuse them... unless I have to go to the auto parts anyhow in which case I may just pick some up.

springer3

If you replace them, be sure to get a recognized head mark from a reputable supplier. There are bad bolts out there, and it is more "risky" if you replace a strong bolt with a weaker one or a defective one...

Most German bolts have "KX" (Karl Marx), or "RIBE" (Richard Bergner) on the head. Both are safe. US made: Lake Erie (LE) are great. Infasco (triangle head mark). and Bowman (difficult to describe headmark) are known for sourcing bolts from around the world. Both had problems, both claim to have fixed them. I stay away simply because there could be older bad bolts at the bottom of the bin somewhere in the supply chain.

darth

I don't know what these bushings look like having never replaced mine but the fact that they're bushings which is a close tolerance bearing in effect, I would think you would want the bolt (i.e axle) which has been desgined for it in both dimension and strength.

Hope this helps
Bill 90 C2

elbeee964

{ springer's bolt mfr knowledge } ----> me:

wow! springer, where'd you happen upon this info?
I'm stone-cold impressed!

Strength questions could be allayed by the head stamp/bolt markings:
http://en.wikipedia.org/wiki/Bolted_...Property_class
http://www.americanfastener.com/tech...ings_steel.asp

-Lonnie

Humorous image: Risky rolling into the local auto parts place, being shown a bolt, and Risky waving it off w/, "No, thanks. That's one of those Infasco's. Got any other headstamp markings back there?"

MisterRisky

Good points Springer. Thanks for the recommendations on brands.

MisterRisky

I was thinking the same thing Lonnie. Actually I was picturing me dumping a bin full of bolts out on the floor at Northern Tool and yelling, "Crap! It's all Crap I tell you! For the love of Carl Marx where are the good bolts?!?!?"

springer3

It is "insider information", but I have no problem sharing it because it helps the good guys and hopefully punishes the bad ones.

Part of what I do for a living is investigate accidents and equipment failures. There have been fatalities caused by inferior or counterfeit bolts. I have personally witnessed hundreds of lab breaks, and am most impressed by the brands named (usual disclaimers). I was testing bolts when the Fastener Quality Act was passed in 1992 by the US Congress in response to sub-standard and counterfeit bolts found in airplanes, nuclear power stations, and military equiment. Needless to say, that legislation was good for business, but with globalization, bad bolts are difficult to police and many are still around.

If you visit www.USPTO.gov, you can download a document that has all the registered headmarks used to identify the factory that manufactured the bolt. Last I counted there were over 700 headmarks registered. If the bolt has a grade mark but no manufacturer's mark, or if the manufacturer's mark is not registered, stay away for sure.

Grade marks designate minimum compliance to the standard. Better bolts exhibit better strength (tension at break) and better toughness (energy absorbed at break). They are well worth the extra money in "Jesus bolt" applications such as suspenson attachements.

MisterRisky

You know, this is beyond just good info. This is the kind of stuff that I am constantly amazed that this board brings forward. Thanks Springer, I really do appreciate the info and the education.

I've been looking online some since Springer prompted the discussion and I have found some good resources:

Suspect bolt markings list with examples. It's a PDF.

Here is another PDF that is from a DOE training session on counterfeit fasteners and industrial valves, etc.

elbeee964

Springer, speaking of such, what must you think of the factory's dead-soft, cad-plated, socket head, seat hold down bolts?
(did I say, 'dead'-soft? )