Rear Coilover Angle?

I am setting up the rear coil over mounts on my 28 Tudor. In order to get the lower shock mount close to axle ends and not interfere with the frame, the shocks have to lean over 30-35 degrees. I found the calculations needed to figure out how much of a heavier spring rate I will need but how will this effect ride quality. Is a 30-35 degrees shock angle too much?

 

I've read somewhere that 30 degree inward lean is okay, and there was a calculator for figuring the spring weight.
I'll try to find it.

Flatman

 

I have that... Here is the correction factors for shock angles.

<TABLE cellSpacing=2 cellPadding=0 width=293 border=1><TBODY><TR><TD align=middle width="12%" bgColor=#f0ffff>Angle</TD><TD align=middle width="12%" bgColor=#f0ffff>10</TD><TD align=middle width="12%" bgColor=#f0ffff>15</TD><TD align=middle width="12%" bgColor=#f0ffff>20</TD><TD align=middle width="12%" bgColor=#f0ffff>25</TD><TD align=middle width="13%" bgColor=#f0ffff>30</TD><TD align=middle width="13%" bgColor=#f0ffff>35</TD><TD align=middle width="13%" bgColor=#f0ffff>40</TD><TD align=middle width="13%" bgColor=#f0ffff>45</TD></TR><TR><TD align=middle width="12%" bgColor=#f0ffff># to use below</TD><TD align=middle width="12%" bgColor=#f0ffff>.96</TD><TD align=middle width="12%" bgColor=#f0ffff>.93</TD><TD align=middle width="12%" bgColor=#f0ffff>.88</TD><TD align=middle width="12%" bgColor=#f0ffff>.82</TD><TD align=middle width="13%" bgColor=#f0ffff>.75</TD><TD align=middle width="13%" bgColor=#f0ffff>.66</TD><TD align=middle width="13%" bgColor=#f0ffff>.59</TD><TD align=middle width="13%" bgColor=#f0ffff>.50</TD></TR></TBODY></TABLE>

I guess people lean shocks over to 45 degrees by looking at the chart?!?

 

Check the mfgs. web sites, but I think most recommend a 30 deg. max. lean. I could see a possible bending sitiuation if too much more than that.

 

Am i reading that wrong? Seems it should want a stiffer spring with the steeper angle.

 

that chart is reading incorrectly.

the number BELOW the angle degree is the effective amount of ORIGINAL spring rate you have left.

at 10*, you have 96&#37; of the springs weight, or if you prefer, you have lost 4%

at 45* you have effectivly lost 1/2 of your springs rate, so at 45* a 200# coil spring is only 100#

 

Yes you are correct...

Here is the formula that you use for this chart: Desired Spring Rate / Angle Correction Factor = Required Spring Rate

Example: If you needed a 200lbs spring and was mounting it at 20 degrees, you would need a 227lbs spring rate for that setup (200/.88=227).

 

All the charts in the world never really helped me.....I must be lame, when we set up my sedan coil overs and the suspension for the roadster we ended up with a big box of extra springs before it got done. Even with the info direct from the manufacturer of several makes of components it's all in the last road test to determine if you get it "right". I am considering AIR next project, infinitely adjustable.

 

HMMM. Now i know where to get some "test" springs

 

When you lean the shock excessively not only do you lose spring rate but also shock rate. The big problem is that the further the shock compresses the worse the problem gets.
Put it this way, if you hit a small bump the shock moves a little and everything is OK. Hit a big bump and with the shock and spring rate both falling the tendency to bottom out accelerates, just the opposite of what you need.
Most well designed road race cars have rising rate suspension where the shock starts out at an angle to the load but ends up directly in line with it. That way the initial displacement is easier and it gets harder the further the suspension travels. A little hard to do on a rod so the best solution is to keep the shock as upright as possible.

Roo

 

Damm Travis, Where did that come from?? Where there pictures that came with the article you got that from? LOL

 

LOL

sometimes i even suprise myself

 

Can someone please tell me if it is ok to lean the springs outward instead of inward? Is there a reason I never see them leaned outward? Any replies are appreciated. Thanks!

 

Zoomy, mine are at 35 degrees, rides great, handles great. I have 10" 300lb springs, rear of car weighs 1697 lbs. no worries. enjoy the ride.

 

coil springs dont care which way they are leaning. compression is compression. once you account for the rate loss:mount angle, leaned over is leaned over. i have seen them tipped back, forwards and inward, but never out. you want the base of the coilover as close to the outside of the axle as possible. moving the bases of the ***emblies too far inboard on the axle will cause instability

 

Go to Proshocks.com this help me. It will calculate the spring you need.

 

Something to consider,when you go to an extreme angle on your shocks,the upper spring hat can come in contact with your mounting bar.QA1 offers an option for their upper spring hat, it has a steep angle to it (like a cone),so when the shocks lay over during compression there is clearance with the mounting bar.

 

Their math is wrong.
The angled mount leverage is the inverse of the cosine of the shock angle.
Cosine of 45° angle is .707 of vertical, they have .50; 30° angle is .866, they have .75; 10° angle is .985, they have .96 etc. Results should be 1 ÷ cosine for rate increase, or 1.414, 1.155, 1.015, etc. instead of 2, 1.333, 1.04166 times desired spring rate.