I'm lost.
Suspension Question?
Thread Starter
Drifting
Joined: Apr 2002
Posts: 1,743
Likes: 37
From: Stockton Ca
Suspension Question?
For the sake of discussion, let's say we have 2 equal cars.
3500 lbs, 50/50 weight dist,350 hp.
I believe 8 in of wheel travel in front.
Rear spring and suspension is comparable to the front.
Vehicle A
100 lbs off front end, #460 springs, full travel
alm brakes, hats ect. 17 lbs reduction per wheel
Less spring rate
less weight sprung/unsprung.
Vehicle B
#550 springs, 7 in of travel
all else stk
How will the ride compare?
At what speed will the heavier springs be required?
Can anyone speak from experience?
What is the best bang for the buck?
R
3500 lbs, 50/50 weight dist,350 hp.
I believe 8 in of wheel travel in front.
Rear spring and suspension is comparable to the front.
Vehicle A
100 lbs off front end, #460 springs, full travel
alm brakes, hats ect. 17 lbs reduction per wheel
Less spring rate
less weight sprung/unsprung.
Vehicle B
#550 springs, 7 in of travel
all else stk
How will the ride compare?
At what speed will the heavier springs be required?
Can anyone speak from experience?
What is the best bang for the buck?
R
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Spring compression is a simple math problem. To compress two 550# springs 3 inches would take 3300 pounds.
It would take really good tires and brakes to x-fer 3300 pounds onto the front tires.
it is the same math for side to side transfer.
So it is the amount of tire hold that determines your spring rate required
It would take really good tires and brakes to x-fer 3300 pounds onto the front tires.
it is the same math for side to side transfer.
So it is the amount of tire hold that determines your spring rate required
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
C3 front wheel rates (the effective spring rate at wheel CL's) are only about 1/2 of the spring rates, so 3" of travel at the front wheels with 550# coils only represents ~1,650# of weight transfer onto or off of the front axle. That same 1,650# transfer would equate to ~3.6" suspension travel at the front wheels with 460# coils.
What you're really asking about has to do with spring frequency, which is relative to sprung weight of a given corner and its wheel rate. Regardless of the vehicle or speeds in question, the higher is the spring frequency the more harshly a vehicle will tend to react to wheel upsets.
Assuming stock C3 geomtery and track width, and that I understand your weight distribution examples correctly, Vehicle B should tend to have a modestly higher spring frequency than Vehicle A; ~0.1 to 0.2 higher by rough math. IMCO such a small increase shouldn't yield a significanlty more harsh ride for anyone except those with overly soft backsides. Besides, one sits much nearer the rear axle.
Yes, tires do play a role in the big picture, but are difficult to quantify thru the maths without relative data.
TSW
correction - that should have been sprung, not unsprung weight
What you're really asking about has to do with spring frequency, which is relative to sprung weight of a given corner and its wheel rate. Regardless of the vehicle or speeds in question, the higher is the spring frequency the more harshly a vehicle will tend to react to wheel upsets.
Assuming stock C3 geomtery and track width, and that I understand your weight distribution examples correctly, Vehicle B should tend to have a modestly higher spring frequency than Vehicle A; ~0.1 to 0.2 higher by rough math. IMCO such a small increase shouldn't yield a significanlty more harsh ride for anyone except those with overly soft backsides. Besides, one sits much nearer the rear axle.
Yes, tires do play a role in the big picture, but are difficult to quantify thru the maths without relative data.
TSW
correction - that should have been sprung, not unsprung weight
Last edited by TheSkunkWorks; Aug 6, 2013 at 08:18 PM.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Sorry, didn't mean to loose anyone.
The wheel rate is really just the spring rate times the motion ratio, which in the case of the C3 front suspension is just under 50%. So, our front wheel rate (per corner) with 550#/inch coils is roughly 275#/inch at the wheel.
Spring frequency is a bit more complicated, but is basically an expression (typically given in Hz) of the natural rhythm at which a corner of a vehicle will tend to oscilate. Vastly oversimplified, the lower is sprung weight (my apologies for misstating that earlier) and/or higher is the wheel rate, the higher will be that frequency. The smoother the surface on which a vehicle is operating, the higher frequencies can be run without adverse effect. And, yes, higher spring frequencies require firmer dampening.
Hope that helps.
edit - As has been pointed out by an astute viewer with a firm grasp on this stuff (69427), the motion ratio I cited above as 50% would more accurately be expressed as 2:1 (wheel:spring).
The wheel rate is really just the spring rate times the motion ratio, which in the case of the C3 front suspension is just under 50%. So, our front wheel rate (per corner) with 550#/inch coils is roughly 275#/inch at the wheel.
Spring frequency is a bit more complicated, but is basically an expression (typically given in Hz) of the natural rhythm at which a corner of a vehicle will tend to oscilate. Vastly oversimplified, the lower is sprung weight (my apologies for misstating that earlier) and/or higher is the wheel rate, the higher will be that frequency. The smoother the surface on which a vehicle is operating, the higher frequencies can be run without adverse effect. And, yes, higher spring frequencies require firmer dampening.
Hope that helps.
edit - As has been pointed out by an astute viewer with a firm grasp on this stuff (69427), the motion ratio I cited above as 50% would more accurately be expressed as 2:1 (wheel:spring).
Last edited by TheSkunkWorks; Aug 9, 2013 at 10:10 PM.
Drifting
Joined: Apr 2007
Posts: 1,970
Likes: 45
From: Cameron Park CA
I hope I'm not high jacking this thread, but my question seems related. Given that removing coils from a spring raises the rate, what would the spring rate be if one coil is removed from a 460# rate spring?
Thanks,
Pete
Thanks,
Pete
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Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Depends on who made them. Give me the wire (not coil) diameter and I'll be happy to figure the theoretical increase, or you should find a number of coil spring rate calculators online.
Drifting
Joined: Apr 2007
Posts: 1,970
Likes: 45
From: Cameron Park CA
Didn't know about spring calculators online. I'll check them and see if I can come up with you do. To test ME, not you.
Many thanks TSW,
Pete
Last edited by PeteZO6; Aug 6, 2013 at 09:39 PM. Reason: iPad spell checker messed me up
Le Mans Master
Joined: Jan 2000
Posts: 8,721
Likes: 108
From: Canada
I've driven my vette with both spring rates, I much prefer the 550's, the ride is a bit stiffer and handled better through curves, fast lane changes. I later added Bilsteins which further improved the ride. The physics speaks for itself so I thought that I would just add my driving experience with the same vette, tires and shocks - much prefer the 550's.
Drifting
Joined: Apr 2007
Posts: 1,970
Likes: 45
From: Cameron Park CA
I've driven my vette with both spring rates, I much prefer the 550's, the ride is a bit stiffer and handled better through curves, fast lane changes. I later added Bilsteins which further improved the ride. The physics speaks for itself so I thought that I would just add my driving experience with the same vette, tires and shocks - much prefer the 550's.
.Pete
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Oh the heavy roll cage really stiffened the frame. I went out for the big cruise night tonight and a friend that never road in my Vette was impressed
Le Mans Master
Joined: Jan 2000
Posts: 8,721
Likes: 108
From: Canada
, I also added a Sharkbar later as well which once again stiffened the ride but still a comfortable one. My wife had 2 spinal fusions and finds the ride fine.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Drifting
Joined: Apr 2007
Posts: 1,970
Likes: 45
From: Cameron Park CA
Sorry I didn't get back to you sooner. In theory, to yield an operating spring rate of 460#/in., a coil with the above wire diameter and typical C3 mean diameter of 4.5" would have 6.29 active coils (those free to move during suspension travel). The same spring with only 5.29 active coils would have a spring rate at 547#/in., or pretty much a 550. Bear in mind that in addition to sprung weight a coil's free length will also affect just how much cutting off a coil will lower ride height. So, unless you really trust your math, or aren't concerned with precision, take smaller bites than you think you'll need, 'cause it's really hard to uncut...
springs. Top edge of front 255/60-15 tires rubbed when cornering. Solution was aluminum spacers under the springs on each side which brought the car up to spec. as measured per the Service Manual. The spacers are very light, but can't recall their dimension - away from home.
Perhaps 550# springs would have accomplished the same result with less hassle, but it is what it is. The car rides fine and corners hard enough to make me back off before it slides off the road.
Speed Direct spreader bar seems to firm up the front end. Being a convertible, the overall car is lousy-goosey. Bolting the hardtop makes a significant difference, but I like it opened up.
Again, thanks!
Pete