can Gd 8 bolt replace crossmember rivet? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

cib101abn · 11-22-2004, 10:17 AM

I have a 79 Chevy P/U that previous owner had collision in, the front cross member is slightly twisted and popped a rivet on the cab side letting it lift up about 1 inch in the twist...thought about bending it back down and replacing rivet with a grade 8 bolt, will this work or does it have to be welded? thanks, bob

Prerunner1982 · 11-22-2004, 11:07 AM

i know quiet a few people who use grade 8 bolts on suspension mounts. Dont see why you couldnt use them on the crossmember as well. just double check the torque on it occasionally and might be beneficial to use a thread lock compound.

BigChevMan · 11-22-2004, 09:55 PM

use grade 5 bolts..that would be equal to the rivet. Grade 8 bolts would be too brittle for that application. A grade 8 bolt would just shear off whereas a grade 5 bolt would bend before it popped...like the factory rivet.

crazy longhorn · 11-23-2004, 01:29 AM

I dont know where the thread is , but there was an article showing fatigue strenghts in both compression & tension......the grade 8 , while a bit overkill for the app, is stronger than a grade 5. The article went on to say that the rockwell hardness of the grade 8 was not high enough to make it brittle. when a grade 8 fails, it fails catostrophiclly......but it is still far beyond the point where the same sized grade 5 bolt would fail (that is in tension, or compression) ! I have used many grade 8 fasteners on the chassis & suspension on my longhorn, & not had a bit of problem

A grade 5 would be plenty strong for that app.....but IMO, an 8 would be better(even tho a bit overkill)..... crazyL

Tx Firefighter · 11-23-2004, 07:48 AM

There have been several colorful discussions here about the grade 5 versus grade 8 bolts. Like Longhorn said, the grade 5 will be long gone before the grade 8 will break. Besides, there are plenty of grade 8 bolts in suspensions, stock from the factory. That tells me something.

Also, back in the day when I was in A&P (airplane mechanic) school, they taught us that the FAA requires using at least a grade 8 bolt, when replacing a rivet with a bolt. The FAA is the authority on every craft that leaves the ground in the US.

64fleetside · 11-23-2004, 09:59 AM

Back in the day when I worked at the dealership, the factory recommended replacing bad or removed rivits with grade 8 hardware. If its good enough for the manufacturer, it's good enough for me! Brian

1-PU70 · 11-23-2004, 10:30 AM

Not to make things more confusing there is the issue of fine thread and corse thread. Fine thread is stronger then corse thread.

68LSS1 · 11-25-2004, 04:00 AM

Ya, someone make those last two threads a sticky please?

Or we'll just have to make it a semi annual arguement.

68LSS1 · 11-25-2004, 06:07 AM

Here's the last thread and here's a link to the grade 5/8 write up.

Truckhead · 11-29-2004, 01:25 PM

How about using Titainium bolts?

Tx Firefighter · 11-29-2004, 02:55 PM

Quote:

Originally Posted by Truckhead

How about using Titainium bolts?

Why? Regular grade 8 steel bolts are more than enough.

11-22-2004, 10:17 AM	#1
cib101abn Screaming Eagle Join Date: Oct 2004 Location: SW of Houston Posts: 288	can Gd 8 bolt replace crossmember rivet? I have a 79 Chevy P/U that previous owner had collision in, the front cross member is slightly twisted and popped a rivet on the cab side letting it lift up about 1 inch in the twist...thought about bending it back down and replacing rivet with a grade 8 bolt, will this work or does it have to be welded? thanks, bob __________________ "Basic Research is what I am doing when I don't know what I am doing." Dr. Werner VonBraun (Rocket Scientist) Contributing Member 79 GMC SWB w/402 79 Chev SWB w400 sm blk being built remnants of 72 Cheyenne (selling)

11-23-2004, 01:29 AM	#4
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,403	I dont know where the thread is , but there was an article showing fatigue strenghts in both compression & tension......the grade 8 , while a bit overkill for the app, is stronger than a grade 5. The article went on to say that the rockwell hardness of the grade 8 was not high enough to make it brittle. when a grade 8 fails, it fails catostrophiclly......but it is still far beyond the point where the same sized grade 5 bolt would fail (that is in tension, or compression) ! I have used many grade 8 fasteners on the chassis & suspension on my longhorn, & not had a bit of problem A grade 5 would be plenty strong for that app.....but IMO, an 8 would be better(even tho a bit overkill)..... crazyL __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

11-23-2004, 07:48 AM	#5
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	There have been several colorful discussions here about the grade 5 versus grade 8 bolts. Like Longhorn said, the grade 5 will be long gone before the grade 8 will break. Besides, there are plenty of grade 8 bolts in suspensions, stock from the factory. That tells me something. Also, back in the day when I was in A&P (airplane mechanic) school, they taught us that the FAA requires using at least a grade 8 bolt, when replacing a rivet with a bolt. The FAA is the authority on every craft that leaves the ground in the US. __________________ I'm on the Instagram- @Gearhead_Kevin

11-23-2004, 10:30 AM	#7
1-PU70 Registered User Join Date: Apr 2000 Location: Bradenton, FL Posts: 1,036	Not to make things more confusing there is the issue of fine thread and corse thread. Fine thread is stronger then corse thread. __________________ 1970 CST/10 402,700R4,3:73 posi,AC,PS,PB,TLT,PW,Buckets with heaters

11-25-2004, 04:00 AM	#8
68LSS1 Registered User Join Date: Dec 2002 Location: Tampa Posts: 1,191	Ya, someone make those last two threads a sticky please? Or we'll just have to make it a semi annual arguement. __________________ '68 Short Step LS1/T56, Hydratech, Fatman Fabrications Stage III, Baer, Hot Rods to Hell, US Body, S&W, etc

11-22-2004, 11:07 AM	#2
Prerunner1982 Registered User Join Date: Oct 2002 Location: Edmond, OK Posts: 5,906	i know quiet a few people who use grade 8 bolts on suspension mounts. Dont see why you couldnt use them on the crossmember as well. just double check the torque on it occasionally and might be beneficial to use a thread lock compound.

11-22-2004, 09:55 PM	#3
BigChevMan My Thoughts Exactly! Join Date: Jan 2003 Location: Ohio Posts: 140	use grade 5 bolts..that would be equal to the rivet. Grade 8 bolts would be too brittle for that application. A grade 8 bolt would just shear off whereas a grade 5 bolt would bend before it popped...like the factory rivet.

11-23-2004, 09:59 AM	#6
64fleetside Registered User Join Date: Apr 2004 Location: arkieland Posts: 1,070	Back in the day when I worked at the dealership, the factory recommended replacing bad or removed rivits with grade 8 hardware. If its good enough for the manufacturer, it's good enough for me! Brian

11-25-2004, 06:07 AM	#9
68LSS1 Registered User Join Date: Dec 2002 Location: Tampa Posts: 1,191	Here's the last thread and here's a link to the grade 5/8 write up. __________________ '68 Short Step LS1/T56, Hydratech, Fatman Fabrications Stage III, Baer, Hot Rods to Hell, US Body, S&W, etc

11-29-2004, 01:25 PM	#10
Truckhead 18436572 Join Date: Aug 2003 Location: Waynesboro, Va. Posts: 488	How about using Titainium bolts?

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