what grade bolts for upper control arms?

[yody]

I got my speedtech control arms and wanted to use stainless bolts, i picked up some from the local hardware store but i know those arn't very strong, they are 1/2" bolts. Wondering if their is any stress on those bolts are what the minimum requirement is? thanks

[ProdigyCustoms]

Factory bolts are some 200,000 psi strength. Must be a reason for it. Stainless is very brittle, I would not even consider it. I have some brand new GM one nice and pretty (black), you can have 4 if you want them. I think they are discontinued.
PM me your address if you want them.

[JayBird]

Go with a grade 8 bolt. Alot of hardware stores will carry grade 8. Your standard bolt is usually grade 5 or lower.

[ProdigyCustoms]

The correct bolts are nurled and won't spin.

[homerneedspeed]

I would use AN grade bolts for any suspension, as Caroll Smith said the FAA dosen't accept SAE grades for a reason. you can get them in 1/8" increments from Pegasus Racing and they are only threaded long enough to get a washer and nut on because excess threads on the inside of the part can wear down parts and are stress risers.

[Q ship]

homerneedspeed, nice resource! Thanks for mentioning them, have you ordered from them? How are they to deal with?

Pegasus racing

[CoryM]

Grade 5 is considered the minimum requirement for automotive. I would not put anything less than grade 8 on a suspension piece that is doing more than everyday driving. Also there are things like thread tolerance to take into account. Using a very tight thread tolerance will result in the bolt packing up when you try to remove it and there is a little junk on the threads. SS is too brittle for a suspension part. If you want it to look pretty, get it coated. Even then you lose some strength, but not as much.

[CarlC]

200 KSI? Grade 8 is 150 KSI, and Metric 12.9 is 177 KSI.

Bolt specifications can get really involved. For A-arm's the bolt is used in double shear. However, in stock form one of the shear paths is through the thread. Not only does this reduce the shear area, but it also has stress risers associated with the thread form

If a Grade 5 aircraft bolt, such as those available through Aircraft Spruce, is used the shear area can be increased since the unthreaded portion of the bolt can be used in full double shear. The full double shear area strength of a G5 aircraft bolt vs. the strength of a G8 stock bolt is very close to the same. However, I'll trust an aircraft bolt from a reputable supplier any day vs. a hardware store item. For a 1/2 G5 bolt in double shear it will take over 25,000 lbs. to fail one. There's two of them on each arm. If we break one, there's something seriously wrong. If we break two......

Stainless should never be used in a suspension componenet. There are only two companies that can offer a product that is in the ballpark with stainless, and that ARP and SPS. ARP does not offer bolts big enough for our A-arm needs.

[a67]

Just to be sure I'm on the same page, the upper control arms bolts mentioned would be the ones that retain the cross shaft to the frame and allow for camber/caster shims?

If so I prefer to use ARP wheel studs. These can be had in 7/16", 1/2", and I do believe 5/8" now. A larger then stock stud can be used to beef things up. IIRC I used the 7/16" size (slightly larger then the stock ones) on the '67. Needed to drill out the cross shaft a little to fit them, but well worth it.

Bob.