Bolt replacement a must?
Thread Starter
Burning Brakes
Joined: Sep 2017
Posts: 1,075
Likes: 65
From: Belgium
Bolt replacement a must?
Hey everyone
In a previous post I said I'll go with poly bushings for the suspension (except body and motor mounts).
A guy at the local 'American oldtimer garage' (Belgium) recommended to replace all the suspension bolts... Everything because the poly bushings are 'harsher' on fasteners.
I can't believe I have to replace all the fasteners on the suspension. Which fasteners are critical (safety precaution) in the front and rear?
In a previous post I said I'll go with poly bushings for the suspension (except body and motor mounts).
A guy at the local 'American oldtimer garage' (Belgium) recommended to replace all the suspension bolts... Everything because the poly bushings are 'harsher' on fasteners.
I can't believe I have to replace all the fasteners on the suspension. Which fasteners are critical (safety precaution) in the front and rear?
Thread Starter
Burning Brakes
Joined: Sep 2017
Posts: 1,075
Likes: 65
From: Belgium
Le Mans Master
Joined: Jun 2019
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From: Indiana
Burning Brakes
Joined: Aug 2007
Posts: 897
Likes: 246
From: Green Valley Ca
I would recommend checking the bolts you take off. Someone could have removed or changed the original bolts. Because the bolts are grade 8 and grade 5. I would agree if the bolts don’t have heavy rust that they should be fine. I would change all the lock washers. Paragon Corvettes is a good source for all fasteners.
Thread Starter
Burning Brakes
Joined: Sep 2017
Posts: 1,075
Likes: 65
From: Belgium
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Team Owner
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From: Redondo Beach, California
Comments...some a repeat of the above.
Original factory suspension bolts are certainly strong enough. Agree, they are grade 5's or grade 8's.
The suspension bolts Paragon sells are not only the correct grade, they are duplicates of the original bolts in terms of finish and head stampings...important for National Corvette Restoration Society members.
Hardware store stainless steel bolts are not replacements for Grade 8's. They are not as strong. For stronger than grade 8, aircraft quality stainless steel or steel bolts are required.
Don't use chrome plated bolts for suspensions. The plating process can cause hydrogen embrittlement which will cause the bolt to crack. For instance, I had the head of a chrome plated bolt just fall off.
Bolt strength is rated in terms of tensile strength. Elasticity can also be a consideration....a springy characteristic can be important for some applications I think.
Original factory suspension bolts are certainly strong enough. Agree, they are grade 5's or grade 8's.
The suspension bolts Paragon sells are not only the correct grade, they are duplicates of the original bolts in terms of finish and head stampings...important for National Corvette Restoration Society members.
Hardware store stainless steel bolts are not replacements for Grade 8's. They are not as strong. For stronger than grade 8, aircraft quality stainless steel or steel bolts are required.
Don't use chrome plated bolts for suspensions. The plating process can cause hydrogen embrittlement which will cause the bolt to crack. For instance, I had the head of a chrome plated bolt just fall off.
Bolt strength is rated in terms of tensile strength. Elasticity can also be a consideration....a springy characteristic can be important for some applications I think.
Thread Starter
Burning Brakes
Joined: Sep 2017
Posts: 1,075
Likes: 65
From: Belgium
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,391
From: At my Bar drinking and wrenching in Lafayette Colorado
Unless you intend to road race the car with some very sticky tires, skip the poly bushings and install the stock rubber. The stock rubber bushings, when new, are actually very good, and will perform beyond your driving ability.
(Most people who advise using poly are people who don't know how to correctly install the stock rubber bushings - the poly is easy to install, and the easy way to get out of a suspension assembly job...).
The stock hardware is more than adequate as long as it's in good condition (not badly corroded/eroded, bent, or damaged). Stock lock washers, in good condition, work just fine as long as all hardware is correctly torqued to spec.
Lars
Last edited by lars; Aug 30, 2021 at 07:25 PM.