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Old 06-15-2012, 12:17 PM   #1
clemsontiger
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Lowering the rear - What bolts to use

Guys, am I correct in saying the simplest way to lower the rear of our C3's is to replace the outward bolts that hold the rear spring in place with longer ones? I'm not so much interested in gaining a handling advantage as I am getting the car's stance looking better. Any idea what size/length bolts to buy? My thought is to pick these up at the local bolt store in grade 8. Any help would be appreciated.
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Old 06-15-2012, 01:28 PM   #2
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I haven't seen bolts like that at the HW store? VB&P sells longer bolts. I believe you'd want 10" bolts.
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Old 06-15-2012, 02:54 PM   #3
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The 8" grade 8, 9/16-18 bolts are usually what is required with an aftermarket spring. They are used with nyloc nuts in place of the stock slotted nuts, although you can figure the set point and drill them for slotted nuts and pins.

Marcus, VB&P stopped selling those??
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Old 06-15-2012, 05:31 PM   #4
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Gary: You're right. Stock is 6.5" and VB&P makes 8" bolts to lower the rear. Don't see any 10" bolts anymore:

http://www.vbandp.com/C2-C3-Corvette...-Hardware.html
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Old 06-15-2012, 05:35 PM   #5
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Yes those are the ones. I had to use them with every aftermarket spring I installed over the past 10-12 years. Even the USA made steel springs required them. I never had a spring settle as some state.
You have to watch with the longer bolts they don't extend down past the point of the wheel in case you get a flat tire the bolt will grind on the pavement or catch something. Also watch with oversize tires that the bolts don't rub on the inside side walls- could lead to tire blow out.
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Old 06-15-2012, 07:49 PM   #6
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I have 2 pairs of 10" bolts that I cut down to 9"(front and rear composite springs) , 10" bolts were too long. Turns out I don't need them, I can get a good height with the 8" bolts. Let them go for $15 a pair plus shipping.
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Old 06-15-2012, 09:13 PM   #7
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I went to the local Caterpillar dealer and got a pair of 10" bolts. Ended up not needing them (of course). CAT bolts are not cheap, but I figure thay are tougher than grade 8's. so what the heck. I think Fastenal might be another place to look.
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Old 06-16-2012, 12:38 PM   #8
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Quote:
Originally Posted by MIKE80 View Post
I have 2 pairs of 10" bolts that I cut down to 9"(front and rear composite springs) , 10" bolts were too long. Turns out I don't need them, I can get a good height with the 8" bolts. Let them go for $15 a pair plus shipping.
Mike, can you email a pic to [email protected] ? Are they grade 8 type hardened bolts?
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Old 06-27-2012, 12:36 PM   #9
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If you replaced your rear spring with a 9 leaf after market spring and now your vett is high in the back the reason is due to the top 3 short leafs of the new spring are curved. If you still have your old spring exchange the top 3 flat leafs from the old spring to the new spring and your vett will settle to the orig. stock ride height without jury rigging with different length bolts.
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Old 06-27-2012, 01:18 PM   #10
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I've still got the original spring, but after driving it a little I still want to go down. Here are pics of the car before and after the restoration. Before it looked as though it still sat up a little hight that I want, so I think even if it settles more that I'll have to use the bolts to get the stance I want.


Untitled by clemson_tiger29679, on Flickr


Untitled by clemson_tiger29679, on Flickr
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Old 06-27-2012, 01:20 PM   #11
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If you don't have the original spring like me there's a place in St. Louis, MO that can re-arch the spring to original GM specs. I looked at some of their info while they were at a local car show, and they had original spec manuals going back to the early 1900's.
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As FPSRussia says "As always.... Have nice day"
Old 06-28-2012, 07:44 AM   #12
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Quote:
Originally Posted by clemsontiger View Post
Mike, can you email a pic to [email protected] ? Are they grade 8 type hardened bolts?
Missed your reply, just came across it. They are grade 8 10" spring bolts that I cut down to 9". I have 2 pairs since my 8" bolts are good enough all around.

Rear


Front bolts can be flipped threads up for more clearance.
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Old 06-28-2012, 09:13 AM   #13
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Mike, did you replace the front suspension with a mono-leaf...or maybe your car is newer than mine. lol My '72 has coil springs on the front. I'll let you know about the rear bolts asap.
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Old 06-28-2012, 09:33 AM   #14
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Quote:
Originally Posted by clemsontiger View Post
Mike, did you replace the front suspension with a mono-leaf...or maybe your car is newer than mine. lol My '72 has coil springs on the front. I'll let you know about the rear bolts asap.
I upgraded the suspension.

http://www.vbandp.com/C2-C3-Corvette...t-1980-82.html
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Old 06-29-2012, 10:06 AM   #15
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Hey guys, do any of you know if what Mike has will work on my factory steel '72 spring? He doesn't know the specs of the bolts, other than lenght, and I'm curious...do the steel springs have the same size bolts as the composite monoleaf springs?
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