Coil Spring Boosters???? - Pontiac GTO Forum
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post #1 of 6 (permalink) Old 07-04-2014, 11:08 AM Thread Starter
 
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Coil Spring Boosters????

Hi Everyone! I have a question about coil spring boosters for the front end of my 67 GTO.
I run over-sized tires, BF Goodrich TA radial p235/60 SR15 tires on 15Ē wheels. I have an issue with the front tires rubbing whenever I hit a speed bump or pulling into my drive way which is on a slight incline. I tried a couple of twist in coil spring boosters up front which seemed to help although Iíve heard horror stories about them falling out. Plus they can be a pain to install.

Iím looking for a better alternative and Iím also wondering if these things will throw off my alignment.
My car is in need of an alignment anyway as I just replaced all my tie rod ends.
I would like to come up with a safe and secure permanent solution before getting the alignment done.
All suggestions welcome.
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post #2 of 6 (permalink) Old 07-04-2014, 10:55 PM
 
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New springs are the correct way to go. There are different spring rates depending on application. I put brand new springs in my '68 Lemans and experienced the same thing. I believe I got the "softer" ride springs. The factory shocks are typically 50-50, or equal dampening force going up and down. Then you have 70-30 which means it has less dampening force going up (extending) and requires more force going down (retracting). I believe I installed a set of 70-30 drag shocks on my car as the car bottomed out on my exhaust pipes on bumps and ruts. Then there is the 90-10 drag shock which is designed to be loose when you accelerate so the car nose goes up and puts the weight on the rear. It then settles down slowly as it is designed to require more force going into the down position. These are not recommended for street use, so I am thinking I used the 70-30 shock. No more bottoming out, but this is not a cure-all, and may not even work in your situation due to your oversized tires.

The front spring rate for a car having air conditioning is higher and would be stiffer -less bounce, and rides rougher. You also need to know what the factory spring ride height is when its compressed. For example, you could have a 17" spring height uncompressed and install it to become 12" once you have the weight of the car on it so it meets the factory ride height/ground clearance specifications. You could also have a larger diameter spring wire at 15" and compress to 12". A heavier diameter spring wire will need more weight to compress it to 12", so this is factored in and the spring is set at 15" uncompressed. If it was set at 17", it would cause your factory ride height to increase and so would your ground clearance.

My guess would be that you want a set of coil springs for a GTO with A/C or possible a Lemans wagon with A/C to get a higher spring rate and keep the stock ride height. If you want a little more lift, then the Chevelle's and El Camino's had some taller springs -Moog #5400 & 5450, but they are also stiffer. I am using #5400 on my '68 Lemans build for hopefully a higher stance. Many choices, just have to do some research and maybe make a few phone calls or send a few emails. It can get confusing.
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post #3 of 6 (permalink) Old 07-05-2014, 08:07 AM Thread Starter
 
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Thanks for the reply. I wonder if there is anyone else out there running BF Goodrich TA radial p235/60 SR15 tires on 15” wheels. I also wonder how I can test my springs both front and rear to see if they are weak and in need of replacement.
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post #4 of 6 (permalink) Old 07-05-2014, 10:39 AM
 
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i am running the wagon springs and have no problem with 245 60R 15. you may not have enough backspace on the rims causing it to stick out more and rub the inner wheelhouse edge. Check the factory manual for ride height sepcs and how to measure them that will tell you if your springs are sagging.

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post #5 of 6 (permalink) Old 07-05-2014, 11:10 AM
 
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I am running that size tire without issue but cannot guarantee that the front wheel wells are the same. I did replace the springs last summer but I didn't have any issues with clearance before the swap.
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post #6 of 6 (permalink) Old 07-09-2014, 01:56 PM
 
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I'm running those tires with 15" rally 2 wheels. I also have a 1 inch drop spring in front and I only have a slight rubbing issue on the right side when I make a left turn. Only if there is a dip though. Not a big issue.

I'm inclined to agree that worn springs and shocks could be coming into play with your issue.
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