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Discussion Starter #1
i want to lower the rear of my car- the guy i bought it from just put a new sping in the back, so it sits wayyyy to high. aside from buying a lowering sping, what would be the best way to lower the car? I read about a C5 guy who's bolts snapped because they were grade 8. should i go grade 5?
Here is a pic of how the car sits now, i would like the tire to be around as close to how the front one is to the fender

thanks-Chris
 

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Discussion Starter #3
I would rather go to my local hardware store and buy these bolts myself, especially concidering that these kits are 20$ plus shipping
 

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I would rather go to my local hardware store and buy these bolts myself, especially concidering that these kits are 20$ plus shipping
Understandable, that would also give you the opportunity to go with castle bolts and a cotter pin that the nylock nuts supplied.

I have these bolts on my car, so unless someone else responds before I get the chance, I will measure the length of mine so you will know what to buy.

Also, upgrading the grade of steel can only help, right?
 

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what was the spring replaced with? Or was the original just re-arched? I just put a fiberglass 330# spring in from VB&P. Came with new longer bolts. Pretty sure they were grade 8 zinc coated.

Man, that rear end is way up in the air. I'd consider switching to the fiberglass spring, but if the $250 isn't in the budget I'd stick with grade 8 and probably go to 10" or 12". Nylocs should do fine. Don't think castle nuts are necessary.
 

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Discussion Starter #6
i would have thought to go grade 8 also, but i read on some thread here that a guy with a C5 was driving around and one of his bolts snapped. he went somewhere and they said it was because grade 8 bolts are only made to hold tourque and are brittle when it comes to flexing. but i would assume this is a very rare occasion when it could have been a bad bolt, that just snapped.

http://www.digitalcorvettes.com/forums/showthread.php?t=72539&highlight=bolt+snapped
heres the link
 

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I measured my aftermarket bolts and they are 10".

Jason Lowe brought up a good point. What is the replacement spring? If you are not a fan of the fiberglass spring, another option is switching from a 9 leaf to a 7 leaf spring. I think that would offer less spring rate and sit a little lower.
 

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i would have thought to go grade 8 also, but i read on some thread here that a guy with a C5 was driving around and one of his bolts snapped. he went somewhere and they said it was because grade 8 bolts are only made to hold tourque and are brittle when it comes to flexing. but i would assume this is a very rare occasion when it could have been a bad bolt, that just snapped.

http://www.digitalcorvettes.com/forums/showthread.php?t=72539&highlight=bolt+snapped
heres the link
I had seen that thread before and stopped reading after the first page. Everyone saying to use grade 8 was correct. Not sure why the fastener store guys said grade 5 would be better. :huh:

That guy's bolt has an obvious flaw in it, as was pointed out by the people posting about the area of rust next to the area of the clean break.

Effectively all of the weight of the rear end is suspended by those two bolts, and they are only in tension. All that BS about flexing is irrelevant. The bushings ensure that even as you're going around a curve with lots of lateral acceleration the bolt is still only in tension. The strut rods and halfshafts will undergo more strain during lateral acceleration, but those bolts will only feel a slight fluctuation in stress.

Although I would expect that the 92,000 psi yield strength of a grade 5 would suffice, you might as well go with the 130,000 psi yield of grade 8 for a higher safety factor. Grade 8 will probably come with some sort of rust preventative coating (probably zinc) that will help prevent failure due to corrosion.

The lowering kits that VB&P sells have 8" bolts:
http://www.vbandp.com/SearchResult.aspx?CategoryID=275

I believe these are 1/2" diameter, but you should compare them to the bolts you pull out of your current spring. Fastenal has 8-1/2" long by 1/2" diameter zinc coated grade 8 fine thread bolts for $5:
http://www.fastenal.com/web/products/detail.ex?sku=18931

If you're looking to go as cheap as possible just pick those up, along with some nyloc nuts and you'll be a bit lower.
 

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Discussion Starter #9
thanks guys, i will probably go out today and get those bolts, and Jason, your write up helped me feel much more comfortable about using grade 8's.
if i get my camera back today i will post pics when its all done
 

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thanks guys, i will probably go out today and get those bolts, and Jason, your write up helped me feel much more comfortable about using grade 8's.
if i get my camera back today i will post pics when its all done
:thumbsup:
 

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You can measure the length you have and then figure how much you want to lower it to get the length you need. If you find that you can't find long enough bolt locally, you can use the ones off a C4, which are about a foot long. I've done it for years w/o problems.

Nice car.
 

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what was the spring replaced with? Or was the original just re-arched? I just put a fiberglass 330# spring in from VB&P. Came with new longer bolts. Pretty sure they were grade 8 zinc coated.

Man, that rear end is way up in the air. I'd consider switching to the fiberglass spring, but if the $250 isn't in the budget I'd stick with grade 8 and probably go to 10" or 12". Nylocs should do fine. Don't think castle nuts are necessary.
I put a 330# composite on my 77 and with the 8" bolts supplied I had 8" between the tire and the fender well. it looked like a jacked up car from the 60s. (I know cause I was driving then.) The only way I could get it down was with 10" bolts with the nuts all the way down. The end of the spring was about 3" away from the ground and almost touching the tire. Not good! I took it off and got a new 9 leaf steel. with the 8" bolts it sits level and looks good. It may even settle after driving, I don't know cause it hasn't even been started yet. Art
 

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I put a 330# composite on my 77 and with the 8" bolts supplied I had 8" between the tire and the fender well. it looked like a jacked up car from the 60s. (I know cause I was driving then.) The only way I could get it down was with 10" bolts with the nuts all the way down. The end of the spring was about 3" away from the ground and almost touching the tire. Not good! I took it off and got a new 9 leaf steel. with the 8" bolts it sits level and looks good. It may even settle after driving, I don't know cause it hasn't even been started yet. Art
wow, that's really surprising. I wouldn't have expected any composite spring to have that much initial arch to it. Who did you get the spring from?
 

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wow, that's really surprising. I wouldn't have expected any composite spring to have that much initial arch to it. Who did you get the spring from?
Corvette America. It was a TRW. I called TRW about it and the guy (Justin) that I spoke to was a major jerk! He told me there must be something wrong with the car or else I had done something to screw up the suspension. I don't believe I'll be buying any TRW products if I can help it! Art
 

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Corvette America. It was a TRW. I called TRW about it and the guy (Justin) that I spoke to was a major jerk! He told me there must be something wrong with the car or else I had done something to screw up the suspension. I don't believe I'll be buying any TRW products if I can help it! Art
huh. I hadn't heard of them until just now. I'm really happy with the VB&P spring. I uploaded some pics from my installation. They show what the suspension looks like unloaded with the 8" bolts.





 

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Everyone I ever heard of who had this problem with a fiberglas spring had used the TRW one.
And the only people I have heard of who had this problem used the TRW spring.
The VBP springs don't seem to have this "issue".
 

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Steel

Call National spring in San deigo or El Cajon they will build you a steel unit that will be varible ratio and ride like a Caddy, also Goldstrand sells a 2 or 3 inch narrow main spring for more clearance, its only money. You will need to scale the car for all four corners, most racers have access to the scales and will help you with that for a small donation to there racing habit. call your local dirt track for who can help. i have heard bad things about the compost springs. i will be having National build me a spring as soon as I get the 75 fully reloaded. for an accurite weight. They said 500 bucks just incase you were considering dropping the dime. i've had two back surgeries and need the wussy ride.
 

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Discussion Starter #20
the spring that i have in my car now is really stiff, so i figured i will try to take a spring or two out. which ones do i take out without turning it into a boat?
i was also given the option of going to a spring place ( a place that specailizes in springs i guess??) its called perth amboy spring, will they try to just heat up my spring, or do something legit to it? (like somehow lessen the arch without killing the ride quality)
which do i do?
 
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