Rust and repair forced me into rivet removal and am wondering has anyone had any probs with using grade 8's or did you aim higher?

 

I have used grade 8 on any spring hanger or crossmember in my 80 pulling truck and have yet to have any issues

 

Yeah grade 8 is pretty much where you need to be. Also on everything i pull that has rivits (other than cab mounts) i drill out to 1/2". Just a little more piece of mind.

 

There is nothing stronger than Grade 8 for SAE unless you find an equivelent size in Metric 12.9.

Josh

 

x2 on drilling the rivet holes out to 1/2".

 

Huh??? Sorry, but that is just WRONG!

Grade 8's will be fine for the question that started this post, but spreading mis-truths is no good.

Grade 9's are out there and easy to get. We use them a lot in the desert race stuff. Grade 10's are harder to come by but used in aviation...

Google is your friend
grade 9 bolts - Google Search

 

There is no such thing as SAE Grade 9 or 10 or 12 etc. Manufacturers create there own grade system for there own bolts. So one manufactuer like Lawson or Bowman could have a "Grade 10" when Deere or Caterpillar would call there's "Grade 12"

It's all marketing as well. I like the Bullet Proof website that claims their Grade-9 (what the heck is that now?) 3/4" bolt is good for 190,000 PSI.

Guess what so is a 3/4" Grade 8. Most people forget the nominal strength of Grade 8 BEGINS at 150,000 PSI.

Josh

 

How is a Grade 8 that is good for 150k psi the same as one that is good for 190k psi? It's not...

Unless you get into the finite specifications of EACH bolt you purchase I would dare to be most of them people are buying are right at the minimum allowed strength requirements.

If you actually use these things under heavy loaded/stress applications you can see the difference between a hardware store grade 8 and then a "grade 9." Heck - you can see differences between foreign made brade 8's and US made grade 8's. The problem is most people don't know there is a difference and go to the HomoDepot or whatever and grab a "grade 8 bolt. For most people this is just fine. For some of us it is not. Heck, I bet 99.9% of the people here don't even "shank" their bolts, or even know what that means.

Now for the original topic in this thread - yes the "basic" grade 8 will suffice. The only problem that has been seen with replacing with the shorter grade 8's is there is not enough elongation or distortion in such a short bolt and in the racers I have heard of people having issues with them keeping proper torque because of this.

 

If you really cared about your bolts you would use aircraft fasteners in the AN sizes like racecars do.

But in response to the question, grade 8 should be adequate.

 

Funny you say "racecars". The race vehicles I've worked on use "grade 9" stuff. Bowman and F-911 typically.

Here is a truck we were helping out with at the Baja 500 a couple weeks ago. I didn't have anything to do with building this one - but it shows the type of "racecars" I am talking about. They aren't cars, but they still cost more than most people's houses

 

So what position did the boat place?

 

1st... or last - depending on how you look at it - seeing as it never moved. Hasn't for years based on the looks of in and the trailer...

 

when I talk about race cars I'm taking about grand am, lemans, rolex, indy, F1, etc. It may not seem like it to you guys, but the stresses those cars put on fasteners is incredible. 3g's of acceleration, braking, and peak cornering, continuous cycling. Some of these cars compete in races 12 or even 24 hours in duration. I'm not saying desert racing isn't tough.. but don't underestimate the abuse those cars are capable of handling.

And they are treated basically like an aircraft. regular inspections, teardowns, etc. And all AN fasteners.

you might have heard of a guy named carroll smith. In his book "prepare to win" he says "don't be deceived- use no sae grade bolts, of whatever specification, in a stressed application. The FAA doesn't allow the use of SAE graded bolts on aircraft and that should be some sort of clue."

AN bolts have just enough thread length to install a nut and one or two flat washers. Keeping the threaded portion out of shear keeps the weaker threaded portion out of the bolted joined, and prevents the threads from acting as a low speed mill if the bolt is subjected to vibration.

I'm not gonna be running out and replacing all my fasteners with AN bolts or anything, but if I have any critical bolts that I replace I will probably be using AN fasteners.

For bolting in crossmembers, grade 8 will be adequate.

 

Thanks guys, we discussed the aviation bolts and I was hoping to get by with the 8's seein's how I own a hardware store.
Thanks for the tip on drilling to 1/2.

 

I get the stresses the cars see. I still will say that something doing 80-100 mph over 3-4' deep "bumps" and running races that go anywhere from 5 hours (San Felipe) to 24 hours (Baja 1k) the trucks see more abuse than the cars. Sure the cars are faster (some of them), but the cars would break in half on the 1st 3 miles of a desert course.

As far as being treated like aircraft and torn down every race - same with the desert. The trucks get taken down to bare frame every race. As far as "just enough threads for the nut" - that's what my comment above about "shanking" your bolts refers to. And yes, we do that too. Desert racing isn't some hillbilly driving around on a logging trail or in a mud pit. Well - at least not the high end trucks