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Old 8th April 2011, 07:43   #106
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Default Re: Coil Spring Adjusters : VFM Fix for the Honda Civic's (lousy) soft rear suspensio

@ananthkamath
Thanks for sharing this info.
Could you please show me some links/pointer for more information (authentic) on spring stiffness calculations.

Cheers
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Old 8th April 2011, 08:33   #107
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Default Re: Coil Spring Adjusters : VFM Fix for the Honda Civic's (lousy) soft rear suspensio

Quote:
Originally Posted by ananthkamath View Post
From looking at GTO's pics, the fact that the number of active coils on the spring has reduced from 5 to 3 means that the spring stiffness has gone up by about 66% worst case [spring stiffness is inversely proportional to number of active coils, so the percentage change is 100* ( (1/3) - (1/5) ) / (1/5).]
Is this actually true that the active coils are reduced from 5 to 3? I don't think this material renders the 2 coils totally inactive, since the material claims of being compressible from say 1 inch to as low as 5mm. At 5mm, yes, it might make the 2 coils totally inactive and rigid. I'm not too good in suspension dynamics, just my observation. But a very interesting point, thanks for sharing.
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Old 8th April 2011, 10:12   #108
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Hey ananth,

Good to see a post from you after quite a while!

Quote:
Originally Posted by ananthkamath
From looking at GTO's pics, the fact that the number of active coils on the spring has reduced from 5 to 3 means that the spring stiffness has gone up by about 66% worst case
Wouldn't it be a reduction of 1 (worst case), since the autorunner goes around for just one revolution?

Cya
R

@dinu - though what you said is correct, ananth said "worst case". (A very theoretical worst case).
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Old 8th April 2011, 11:03   #109
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Default Re: Coil Spring Adjusters : VFM Fix for the Honda Civic's (lousy) soft rear suspensio

Quote:
Originally Posted by dinu2506 View Post
Is this actually true that the active coils are reduced from 5 to 3? I don't think this material renders the 2 coils totally inactive, since the material claims of being compressible from say 1 inch to as low as 5mm. At 5mm, yes, it might make the 2 coils totally inactive and rigid. I'm not too good in suspension dynamics, just my observation.
Actually its the opposite of what you're saying. 2 coils are rendered fully inactive at low loads because the donut has a very high stiffness and wont compress much at those loads. At higher loads it starts compressing and the overall stiffness of the "spring-donut system" reduces, but not by much because the donut itself has a pretty significant rising rate (or stiffness).

My best guess is, a 1" high polyurethane donut like that will probably be 20 to 50 times stiffer than the coil spring itself, depending on durometer (a measure of hardness, to which the stiffness is proportional). Only way to tell is by actually putting it on a spring tester or a universal testing machine which can be found in almost every mechanical engg lab.

Quote:
Originally Posted by rehaan2 View Post
Hey ananth,

Good to see a post from you after quite a while!



Wouldn't it be a reduction of 1 (worst case), since the autorunner goes around for just one revolution?

Cya
R

@dinu - though what you said is correct, ananth said "worst case". (A very theoretical worst case).
Hey rehaan, whats up man - nice to meet again!!

Actually it is close to 2 coils because the donut is wedged between two of them (one on top, and the other on its bottom), so it takes them both out. Counting coils is anyway pretty subjective, I never did like the formula for calculating compression spring rate :-).

The worst case estimate is also probably pretty close to reality for on-center rate of the spring, but I was trying to simplify things for everybody's benefit.

Last edited by ananthkamath : 8th April 2011 at 11:07.
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Old 8th April 2011, 11:12   #110
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Default Re: Coil Spring Adjusters : VFM Fix for the Honda Civic's (lousy) soft rear suspensio

Quote:
Originally Posted by ananthkamath View Post
Actually its the opposite of what you're saying. 2 coils are rendered fully inactive at low loads because the donut has a very high stiffness and wont compress much at those loads. At higher loads it starts compressing and the overall stiffness of the "spring-donut system" reduces, but not by much because the donut itself has a pretty significant rising rate (or stiffness).

My best guess is, a 1" high polyurethane donut like that will probably be 20 to 50 times stiffer than the coil spring itself, depending on durometer (a measure of hardness, to which the stiffness is proportional). Only way to tell is by actually putting it on a spring tester or a universal testing machine which can be found in almost every mechanical engg lab.
The figures are frightening - 50 times stiffer.
@GTO, I think we badly wait for your real world experience, especially with a very light load on how the car behaves.
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Old 8th April 2011, 11:32   #111
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Default Re: Coil Spring Adjusters : VFM Fix for the Honda Civic's (lousy) soft rear suspensio

Mods, hope this is right place to post the same.

Hi, I had the same 'bottoming out' problem with my zen a few years ago when i upsized my rear tyres to 195's (pre used from JC road). The day after i installed the tyres, i set off for a drive to Ooty (five of us in the car). The rear started bottoming out/scraping the mudguard like crazy after mysore, the road being full of up's and downs. Just as i started to curse myself for the stupid idea of upsizing, my friend came up with a solution. We stopped at a small 'amby' workshop near nanjungud and picked up some old suspension rubber bushes. We then simply forced the springs apart with a log and placed the bushes flush between the springs before releasing the springs back to tension. The car drove like a dream after that and not once did it bottom out on the way to ooty. It was supposed to be a make-shift solution, but lasted me two years more till i sold the car. 0.00 Rs spent for a stiffer suspension. I wonder if the same could done for mordern cars like the civic Here's a pic of the springs being lifted.
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Old 8th April 2011, 12:21   #112
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Default Re: Coil Spring Adjusters : VFM Fix for the Honda Civic's (lousy) soft rear suspensio

Quote:
Originally Posted by ananthkamath View Post
I would like to caution everyone who is using this piece of kit to drive conservatively at first and get used to the handling of the car, because that WILL change, probably pretty dramatically when the car is not fully loaded. The reasons are outlined below in simple terms.

The rubber donut that GTO has installed is basically an elastomer (probably polyurethane). Installing this basically makes the rear act as two springs in series, which in theory should actually reduce the total stiffness at the rear. However, in practice, since the method of installation involves reducing the number of active coils on the coil spring, the stiffness increases quite a bit, which is why the rear sags less when there is heavy load in the car.

From looking at GTO's pics, the fact that the number of active coils on the spring has reduced from 5 to 3 means that the spring stiffness has gone up by about 66% worst case [spring stiffness is inversely proportional to number of active coils, so the percentage change is 100* ( (1/3) - (1/5) ) / (1/5).]

This, guys, is a HUGE change. When a car is tuned before it is released for sale to the public, the front to rear stiffness distribution is very carefully determined because that has a massive impact on the balance of the car. In general, the more the rear stiffness, the less the understeer.

In all probability, this mod reduces the understeer quite heavily when the car is lightly loaded, so you guys who install this need to be VERY careful when driving spiritedly or in slippery conditions cause the rear end can break away in such a manner that a normal (non-expert) driver cannot catch it soon enough. The consequences are left for your imagination.

The correct way to achieve the same effect is to make the springs in parallel, and have one of the springs contact only when the suspension starts compressing heavily under load. This is known as a bumpstop in common parlance, but technically it is called a jounce bumper, the black rubber part shown inside the coil spring below:

Attachment 528449

This part accomplishes two things:

1) Does not affect the stiffness when the car is unloaded, thereby not having any effect on handling.

2) Increases the stiffness when the car is heavily loaded so that the suspension does not bottom out and cause snap oversteer due to the stiffness increasing to almost infinity (in theory).

Most of the time this part is installed on the shock shaft, so the Honda probably has it inside the shock, but unfortunately it is not sufficient when the car is heavily loaded, so the customer has to resort to poorly designed but partially effective measures such as GTO has done.

So, in parting, please use caution!!

Hey. Thanks for this. You explained everything in technical terms. I was speaking more like a driver. On doing similar mods to the front end as well, I am not in favor of that as well as the front starts bouncing like crazy and the whole driving experience goes for a toss.

@GTO, stiffening suspension also means you will have to play around with lower tire pressures. This means lower FEs.
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Old 8th April 2011, 13:57   #113
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Default Re: Coil Spring Adjusters : VFM Fix for the Honda Civic's (lousy) soft rear suspensio

Quote:
Originally Posted by ananthkamath View Post
Actually its the opposite of what you're saying. 2 coils are rendered fully inactive at low loads because the donut has a very high stiffness and wont compress much at those loads. At higher loads it starts compressing and the overall stiffness of the "spring-donut system" reduces, but not by much because the donut itself has a pretty significant rising rate (or stiffness).

Actually it is close to 2 coils because the donut is wedged between two of them (one on top, and the other on its bottom), so it takes them both out.
Hi,
Don't get it, the two coils part. Could you please elaborate on it.
What would be the load - compression graph with the polymer wedge?

Regards
Sutripta
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Old 8th April 2011, 15:41   #114
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Default Re: Coil Spring Adjusters : VFM Fix for the Honda Civic's (lousy) soft rear suspensio

Quote:
Originally Posted by rjstyles69 View Post
Rush a really innovative and cost effective way to increase the GC using the coil spring adjuster. What is the guarantee that this wouldn't pop out from the spring ?
I know you already mentioned that in the 1st post, but then on our Indian roads would this thing really stay put ? I guess only time will tell if this would actually prove to be a cost effective mod.
I checked it out at one place and AFAIK two things prevent it from jumping out:

1. The donut is placed in when there is no load on the springs and when the spring is loaded the springs fit right into the concave part.
2. The donut is made of 5 different layers of rubber and the outer layers are far more rigid than the inner layers. So under load it won't jump out because the outer layers retain their shape and hold it in place.

Hope that helps.

Last edited by di1in : 8th April 2011 at 15:42.
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Old 8th April 2011, 16:19   #115
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Default Re: Coil Spring Adjusters : VFM Fix for the Honda Civic's (lousy) soft rear suspensio

@ Ananth : Awesome post, thanks for sharing. Will reply once I'm back from my road trip.

Report after 180 kms on the highway with 5 onboard + a trunk full of luggage

- With full occupancy onboard (5 + fully loaded trunk), the Civic did not scrape over speed breakers; this was a revelation. Even the poorly designed toll naka speed-breakers were dismissed off without complaint.

- The car is bottoming out a LOT less. Before, the suspension used to easily bottom out on road dips & ups at any speed over 50 kph. I would say the bottoming out is 60 - 70% less than before. Even the rear end bounciness is far better controlled.

- Unfortunately, it's NOT improved the full-load handling at all. Feels about the same (no advantage), and there is no perceptible difference in grip, nor any perceptible decrease in body roll (still rolls the same as it did before with 5 onboard).

I'll know if it handles better with a lesser load only on Sunday, when I'm driving the 180 kms back with 2 passengers (instead of 4).
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Old 8th April 2011, 16:26   #116
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Default Re: Coil Spring Adjusters : VFM Fix for the Honda Civic's (lousy) soft rear suspensio

Thanks GTO, that's reassuring.

Quote:
Originally Posted by GTO View Post
I'll know if it handles better with a lesser load only on Sunday, when I'm driving the 180 kms back with 2 passengers (instead of 4).
Eagerly waiting for this report with less load. I'm perfectly fine if it handles the same as stock (good enough for me). Only hope the outcome described by Ananth does not occur (that of reduced understeer), which can compromise safety.

By the way, my courier should be reaching today or tomorrow, however installation will only be next weekend, as I'm tied up this weekend.

Last edited by dinu2506 : 8th April 2011 at 16:29.
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Old 8th April 2011, 16:44   #117
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Default Re: Coil Spring Adjusters : VFM Fix for the Honda Civic's (lousy) soft rear suspensio

Quote:
Originally Posted by GTO View Post
@ Ananth : Awesome post, thanks for sharing. Will reply once I'm back from my road trip.

Report after 180 kms on the highway with 5 onboard + a trunk full of luggage

- With full occupancy onboard (5 + fully loaded trunk), the Civic did not scrape over speed breakers; this was a revelation. Even the poorly designed toll naka speed-breakers were dismissed off without complaint.

- The car is bottoming out a LOT less. Before, the suspension used to easily bottom out on road dips & ups at any speed over 50 kph. I would say the bottoming out is 60 - 70% less than before. Even the rear end bounciness is far better controlled.

- Unfortunately, it's NOT improved the full-load handling at all. Feels about the same (no advantage), and there is no perceptible difference in grip, nor any perceptible decrease in body roll (still rolls the same as it did before with 5 onboard).

I'll know if it handles better with a lesser load only on Sunday, when I'm driving the 180 kms back with 2 passengers (instead of 4).
Woah GTO thats brilliant.Seems like I'll be getting the Coil Udjusters for the ANHC rear suspension as well.
Now where is this Auto Runner available?
Where to get it installed?

Thanx for you replies in advance.
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Old 8th April 2011, 19:15   #118
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Default Re: Coil Spring Adjusters : VFM Fix for the Honda Civic's (lousy) soft rear suspensio

Quote:
Originally Posted by Sutripta View Post
Hi,
Don't get it, the two coils part. Could you please elaborate on it.
What would be the load - compression graph with the polymer wedge?

Regards
Sutripta
OK. Got what you are saying. Though instead of thinking of 1 turn = 2 blocked, I suppose it would be N turns = (N + 2x) blocked, the value of x to be worked out.

Regards
Sutripta

Last edited by Sutripta : 8th April 2011 at 19:22.
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Old 8th April 2011, 20:47   #119
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Default Re: Coil Spring Adjusters : VFM Fix for the Honda Civic's (lousy) soft rear suspensio

ah.. just came across this thread. Pretty interesting idea.

Quote:
Originally Posted by GTO View Post
- With full occupancy onboard (5 + fully loaded trunk), the Civic did not scrape over speed breakers...

- The car is bottoming out a LOT less....

- Unfortunately, it's NOT improved the full-load handling at all....
This means the Coil spring adjusters have only decreased the travel and not had any real effect on the stiffness.

In that case, I suspect, it will have no effect on no-load handling as well.
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Old 8th April 2011, 20:55   #120
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Default Re: Coil Spring Adjusters : VFM Fix for the Honda Civic's (lousy) soft rear suspensio

Quote:
Originally Posted by GTO View Post

You can install coil-spring adjusters at the top of the spring (working at all times), in the middle (effective under mild to full load) or at the bottom (comes into play only under full load). I chose to install it at the top, as per Psycho's advice.
GTO, was just going through the thread again before I head out tomorrow morning and this para caught my eye.
You mentioned that you have installed it at the top of the springs but the pics say its in the middle.

Whats gives?
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