340lb or 355lb
Thread Starter
Pro
Joined: Jan 2004
Posts: 535
Likes: 1
From: Darwin, Australia NT
340lb or 355lb
Im putting in a composite rear spring but unsure which one to select.
I presently have a 9 leaf which I understand is soft. I have had the exhaust hit the ground in the past so I want something stiffer and I understand that a stiffer spring reduces the likeihood of half shaft unis breaking.
I will only run my 1970 coupe on the street so dont want anything too hard. I'll have a 540 with 650hp and a TKO trans.
I presently have a 9 leaf which I understand is soft. I have had the exhaust hit the ground in the past so I want something stiffer and I understand that a stiffer spring reduces the likeihood of half shaft unis breaking.
I will only run my 1970 coupe on the street so dont want anything too hard. I'll have a 540 with 650hp and a TKO trans.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Years ago i was into drag racing my Vette. In an attempt to perfect the launch with wrinkle wall slicks I had a friend with a video camera take movies from the side and rear from very close up.
I also had the rear 9 leaf. I was having major squat problems even with my VB&P Smart Struts, 3/4 rear sway, and Koni shocks. So I bought the 340 or 360 fiber mono from VB&P. I went back out and it was better, but not right. I was also getting into the high speed open road racing and I needed a firmer feeling when exceeding 150 mph.
I played with the ends and differntial spacers to set the rear height, but was never totally happy. I still had way too much squat on the launch
I went to a local leaf spring shop and told them what i was trying to do. Body rake, ride height, spring rates......................
They took my car which had the 550 front springs with the 1 1/8th poly mounts and adjustable spring end sways and added a leaf to my 9 leaf and rearched the rear spring to get the correct height.
What i ended up with is more like a 420+ pound rate without the draw backs of an off the shelf mono spring
I also had the rear 9 leaf. I was having major squat problems even with my VB&P Smart Struts, 3/4 rear sway, and Koni shocks. So I bought the 340 or 360 fiber mono from VB&P. I went back out and it was better, but not right. I was also getting into the high speed open road racing and I needed a firmer feeling when exceeding 150 mph.
I played with the ends and differntial spacers to set the rear height, but was never totally happy. I still had way too much squat on the launch
I went to a local leaf spring shop and told them what i was trying to do. Body rake, ride height, spring rates......................
They took my car which had the 550 front springs with the 1 1/8th poly mounts and adjustable spring end sways and added a leaf to my 9 leaf and rearched the rear spring to get the correct height.
What i ended up with is more like a 420+ pound rate without the draw backs of an off the shelf mono spring
Le Mans Master
Joined: Jul 1999
Posts: 9,206
Likes: 17
From: Sewell NJ
I have a 340 lb. TRW type spring on my 74. For the longest time I thought I would need to go with a stronger spring because of the bounciness and sometimes bottoming of the exhaust. At the time I was running KYB shocks. This winter I installed a set of Bilstein Sport shocks and the difference was night and day. No more bounce and no more bottoming. The ride is very controlled now and the spring is a good compromise between comfort and all out performance. 
Safety Car
Joined: Oct 2004
Posts: 3,923
Likes: 733
From: Youngstown Ohio
I have a 380 lb. composite spring on my '69, and since it is a street/strip car I wish it was stiffer at the track. It actually seemed soft on the street until I changed to QA-1 adjustable shocks. The shocks you use really make the difference.
Composite springs don't react quite the same as steel springs, as they are both "softer" and "harder"......sounds confusing, but they are softer over bumps than a similar stiff steel spring, but they rebound quicker and snappier. If you are trying to compare poundages between the two, I'd go for a slighter stiffer than recommended comp. spring to get a similar overall road feel.
Composite springs don't react quite the same as steel springs, as they are both "softer" and "harder"......sounds confusing, but they are softer over bumps than a similar stiff steel spring, but they rebound quicker and snappier. If you are trying to compare poundages between the two, I'd go for a slighter stiffer than recommended comp. spring to get a similar overall road feel.
Burning Brakes
Joined: Mar 2005
Posts: 1,139
Likes: 0
From: Salina Kansas
I drove mine a lot as a daily driver with a 340 TRW rear spring. Road great, handled pretty well too and was actually softer than the stock leaf springs that I took out of it. Recently put a 390 composite in it, preparing for a little strip action, but don't have an opinion on it yet. Need to get some better rear shocks, have the KYB as well.
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Le Mans Master
Joined: Jan 2000
Posts: 8,721
Likes: 108
From: Canada
I am going to have my steel spring re-arched. I have both a 7 leaf and 9 leaf. Presently I have the 9 leaf on as with my wife's spinal fusion she likes the softer ride quality and with the Bilstein's there is no bounce. I have the stock 550 lb springs up front. Knowing that Dick Guldstrand only ships with the metal springs made me stick with mine.
Burning Brakes
Joined: Sep 2005
Posts: 895
Likes: 4
From: whitman massachusetts
Talk to VBP
If you call a Tech at VBP, they will listen to what you are trying to accomplish, and set you up accordingly. You are not limited to a set sporing rate with their prodoct. They will custom fab a spring rate to your described needs. Plus they are GREAT to deal with, I have been very happy with how they have treated me, and I am a PIA!
Racer
Joined: Nov 2006
Posts: 438
Likes: 1
From: Hunington Beach California
I have a 340 lb. TRW type spring on my 74. For the longest time I thought I would need to go with a stronger spring because of the bounciness and sometimes bottoming of the exhaust. At the time I was running KYB shocks. This winter I installed a set of Bilstein Sport shocks and the difference was night and day. No more bounce and no more bottoming. The ride is very controlled now and the spring is a good compromise between comfort and all out performance.
Safety Car
Joined: Jun 2002
Posts: 3,689
Likes: 1
From: St Petersburg FL
St. Jude Donor '07,'13
Shocks
We offer both the KYB and the Bilstein shocks. Both are good quality shocks, but they need to be in the correct application to get the best results.
Typically the KYB's are good for a smooth, soft, touring ride with lower rated, stock arch style springs. When you get into lower arch styles and higher rated springs with more performance, it is better to step up to the Bilstein Sports. These are specially valved to work best with our design spring and the higher, stiffer rates. They have more the dampening rebound side so they will let you down nice and slow and smooth and not bounce you around.
We have a Special Thank You for 30 Years Anniversary Sale going on right now where we have 30% off on our springs.
If you would like to discuss our springs further, please do not hesitate to contact me toll free at 1-800-237-9991 or email me directly at Pattie@VBandP.com. We can set you up in just the right arch style and spring rate so you can accomplish the driving style and performance you want.
Best Regards,
Pattie Cooke, Sales Mgr.
VBP (Vette Brakes and Products)
Typically the KYB's are good for a smooth, soft, touring ride with lower rated, stock arch style springs. When you get into lower arch styles and higher rated springs with more performance, it is better to step up to the Bilstein Sports. These are specially valved to work best with our design spring and the higher, stiffer rates. They have more the dampening rebound side so they will let you down nice and slow and smooth and not bounce you around.
We have a Special Thank You for 30 Years Anniversary Sale going on right now where we have 30% off on our springs.
If you would like to discuss our springs further, please do not hesitate to contact me toll free at 1-800-237-9991 or email me directly at Pattie@VBandP.com. We can set you up in just the right arch style and spring rate so you can accomplish the driving style and performance you want.
Best Regards,
Pattie Cooke, Sales Mgr.
VBP (Vette Brakes and Products)
