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Rear Coil-Over spring rate

19K views 12 replies 7 participants last post by  Irelands child 
#1 ·
I've been finishing up the last details on my TCI coil over chassis before final assembly of the body on it and a light went on :embarrass - the rear spring rate is too low for the mods that I've made. My recollection is that they are something like 200#. I've added a '32 style 15 gas tank hanging off the rear of the chassis along with 20-30 pounds of mounting steel plus a heavy Optima battery. With this arrangement, I've probably made it similar to a '32 as far as weight. This brings me to my questions - (1) what spring rate would a '32 normally use? 250? 300? (2) What is an optional and reliable brand spring other then the TCI All Americans - one of the Speedway supplied(TCI is NOT a quick shipper) ? TCI says that they are 14" free/10" compressed tho I just measured them in place and they are ~10" installed so it appears as if a bit of disassembly is in my days agenda.

Dave W
 
#2 ·
Hi Dave....I've got a TCI '32 chassis for my Victoria, they usually do good work but I have to say they are one of the worst in customer relation. Send you the wrong parts to start with then you have to pay shipping to send them back......or you just don't get the right parts. Anyway I think you should be able to use the 250# springs. Or you can call a buddy of mine who has been a TCI dealer for a long time, he can tell you ...and get you the springs if needed, Greg Bowden, (928) 855-7005, good luck.......Dave
 
#3 ·
327NUT said:
Hi Dave....I've got a TCI '32 chassis for my Victoria, they usually do good work but I have to say they are one of the worst in customer relation. Send you the wrong parts to start with then you have to pay shipping to send them back......or you just don't get the right parts. Anyway I think you should be able to use the 250# springs. Or you can call a buddy of mine who has been a TCI dealer for a long time, he can tell you ...and get you the springs if needed, Greg Bowden, (928) 855-7005, good luck.......Dave
Thanks for the information, 327. I'll hang onto it for reference.

After I posted this, I talked to Carlos at TCI. First of all, he did say that the 200 pound springs that they originally supplied when I bought the chassis were for a fact, too light and that now 250 or 300 pounders would be supplied. Another item that he 'admitted' to was that the on-line catalog had a lot of errors, including the spring length. They are NOT 14" long but maybe only 12" - and the way he said it didn't give me warm and fuzzies. So with that said, I will take one of them apart :pain: and measure myself - and then order, and possibly from Speedway or another supplier..

I, for sure, have had my problems with TCI quality. While nothing insurmountable, more of a nuisance. The first was most of my $$$$ chrome and stainless suspension items were gouged and scratched - and it was not due to shipping - and had to be replaced. The second was the fact that the motor mounts were installed 1", exactly, too far back.

Dave
 
#4 ·
Just for sake of throwing in 2 cents is that if the springs you fellows have will support the car during the build then when you have all the major weights in the car including the body then you can weigh it at each end and be a lot closer to what you need..Even at that there may be some tuning required to get the ride and handling to where you want it to be..

I would try and save my money till I have a better idea of what I need..

Just my take

Sam
 
#5 ·
I second what Sam said...I would not do anything until you are able to take it out.
Drive the car, then tune the spring rate. If it bottoms out too easily, you need stiffer springs. too harsh, and it needs less.

I've seen TCI setups need to go in either direction from what they originally supplied. A friend of mine wound up with 160# on the back of his '34 coupe..from 250# .so there is no teling what you may need. It takes only an hour or so to change springs.


IIRC Carlos used to be the shipping guy at TCI.

Later, mikey
 
#6 ·
powerrodsmike said:
I second what Sam said...I would not do anything until you are able to take it out.
Drive the car, then tune the spring rate. If it bottoms out too easily, you need stiffer springs. too harsh, and it needs less.

I've seen TCI setups need to go in either direction from what they originally supplied. A friend of mine wound up with 160# on the back of his '34 coupe..from 250# .so there is no teling what you may need. It takes only an hour or so to change springs.


IIRC Carlos used to be the shipping guy at TCI.

Later, mikey

Mikey & Sam
For sure I'll need something better and really not in a hurry to order tho - but just to make my life better, want to at least have an idea of free length and a place to start. Remember my opening statement - I am working with a lever here and adding a 45 pound tank and assembly, 15 gallons of gas, the support steel assembly and an Optima battery that weighs a lot - beyond the original TCI frame.

Thats 15 x 6.25 = 94# plus 30# of support steel and other claptrap for the 45# tank, then the 40-50 pound Optima battery and case. My guess for added weight on the rear springs is about 215 - 225 pounds.

Dave
 
#7 ·
Dave, I would not do a thing until you have the car finished and fueled. Remember, 200#s will depress your springs 1/2 inch. Your total weight on the rear axle could come in at 1200 pounds and you would get 3 inches depression and that may be close to what you want. When I am building a car/truck, the springs are about the last thing I tweak before going to the alignment shop.

You may want to put the Optima battery on a bath room scale if you can't find the weight written some where. I am running a yellow top Optima and I don't think it will go above 35#s

Trees
 
#8 ·
trees said:
Dave, I would not do a thing until you have the car finished and fueled. Remember, 200#s will depress your springs 1/2 inch. Your total weight on the rear axle could come in at 1200 pounds and you would get 3 inches depression and that may be close to what you want. When I am building a car/truck, the springs are about the last thing I tweak before going to the alignment shop.

You may want to put the Optima battery on a bath room scale if you can't find the weight written some where. I am running a yellow top Optima and I don't think it will go above 35#s

Trees
Trees,
I do need to know what these spring really are - and TCI couldn't tell me. With the body still in the paint booth and the chassis sitting there nekkid, it's a good time to find out, regardless. Are they really 200#? Are they really 12" or something else? TCI couldn't tell me.

The red top Optima battery, according to their website, weighs 38#. Add a Summit completely surrounding case, a Speedway hold down and the weight of some cable, and now the weight is 58# according to my bathroom scale. The photo has the top and cables omitted

Dave W

 
#9 · (Edited)
Check out this tool that speedway sells
http://www.speedwaymotors.com/p/231,154_Hydraulic-Coil-Spring-Rater.html

(testing that link tells me that the speedway server is messed up right now. wait a bit)

Here is a pic of the Rebco version of that speedway spring tester.


A thrifty and resourceful fellow such as yourself could build a similar spring tester with stuff you may already have laying around the house, shop or friends house , and you could test/rate them yourself.
With my deviant perception, I see a shop press with a bathroom scale in that picture...Grease up the shop press frame to remove some of the stiction. You are measuring springs within a 300# range anyway.


Or find the some circle track guys...they always seem to know who has a spring tester you can visit.



Spring rate is not magic, spring rate is how much force a spring will resist when compressed a certain distance.

So you compress the spring 1" and read how much force it exerts on a scale. The rate is supposed to be somewhat linear.

Here is a spring testing article from Longacre racing that might help.

http://www.longacreracing.com/articles/art.asp?artid=7

I know that even with all that sophisticated stuff, the advertised spring rate ain't always what you get..My buddy Ed took 4 sets of springs from eaton detroit down the the local high stepper chassis shop. (not me...I am bathroom scale guy), and every one of those springs tested different than what was advertised.... :rolleyes:

Just something to think about.


Later, mikey


No TCI can't tell you what you have ..they only designed, built, sold, packaged and shipped it to you. :confused:


They do make some very nice parts though. I understand that Ed Moss is a very knowledgeable guy and a good fabricator as well.. Too bad you never get to talk to him.


Later, mikey
 
#10 ·
powerrodsmike said:
Check out this tool that speedway .........Later, mikey
Mikey,
What I was going to do is take a spring to our local NASCAR race car builder, Jake Spraker, and have him give it a test. At least my 'line in the....' (oh phooey, that's a trite phrase) will be drawn. I had considered making my own, as you have suggested, but since there is a good coffee shop with a nice lookin' waitress near Jake's shop......

The Longacre site makes for some very good reading - lots of interesting reading, even if I will never ever get into a race car again. Race cars sure aren't cheap to build anymore.

The Speedway site is indeed down now. I'll take a look at my paper version.

TCI parts are very nice though I do have some predjudices against some of their items.

Later,
Dave
 
#12 ·
Some springs have the rate engraved on the top/bottom of the coil so look there first. You can also calculate the spring rate after taking a few measurements. If you get me the wire diameter (use a micrometer), the length (tape measure is fine), the diameter (tape measure is fine) and a picture I could plug in the numbers for you.
http://www.efunda.com/DesignStandards/springs/calc_comp_designer.cfm
 
#13 ·
Triaged said:
Some springs have the rate engraved on the top/bottom of the coil so look there first. You can also calculate the spring rate after taking a few measurements. If you get me the wire diameter (use a micrometer), the length (tape measure is fine), the diameter (tape measure is fine) and a picture I could plug in the numbers for you.
http://www.efunda.com/DesignStandards/springs/calc_comp_designer.cfm
Thanks - it will be a few days (or more), depending on what other projects I get involved doing.

Interesting web site -

Dave W
 
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