cymtriks
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 posted on 6/6/03 at 01:48 PM |
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spring rates
I've done a calculation regarding spring rates based on the equations in Staniforths "Competition car suspension".
The results suggest that the book rear springs are too hard in comparison to the front.
Just right appears to be standard (book) front and 130lb rears with an anti roll bar of about 10 to 11mm at the front.
A stiffer choice would be 280 front, 180 rear and a 12 to 13mm roll bar at the front.
Can anyone confirm this from road or race experience?
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GO
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| posted on 6/6/03 at 02:03 PM |
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Not sure about the spring rates, but has anyone fitted an anti-roll bar at the front yet?
I know someone posted a question about this a short while ago, asking how to modify an existing one (Mondeo I think??)
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GO
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| posted on 6/6/03 at 02:06 PM |
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Cymtriks,
Quick (and stupid) question, did you include weight for your average driver in your calcs?
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dozracing
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| posted on 6/6/03 at 02:26 PM |
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I have made an anti roll bar kit for the front of my race car, which is a 1/2" x 16swg tube. Using solid bars adds loads of weight. Tubes are
much more effective.
My shock kit uses 275 and 175 springs and the on the road handling and ride seems to be universally approved. Although the shocks are valved to help
out in this resepct also.
Kind regards,
Darren
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kiwirex
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| posted on 7/6/03 at 09:04 AM |
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dozracing:
> I have made an anti roll bar kit for the front of my race car, which is a 1/2" x 16swg tube.
> Using solid bars adds loads of weight. Tubes are much more effective.
Is that standard mild steel tube or something springy?
ta,
Greg H
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cymtriks
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| posted on 7/6/03 at 08:37 PM |
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weights used in calcs
For the weight calcs I used 550Kg car plus 75Kg driver. I also looked at the effect of increasing the weight by a further 75Kg for a passenger.
I used Staniforths suggestion of assuming 25Kg per corner unsprung weight and assumed 50-50 weight distribution.
The theoretical best approach is, according to the text books, to aim for equal roll resistance front and rear which minimises the torsional loading
on the chassis to loads produced by bumps only and avoids any inherent bias to over or under steer. A 10 to 15% lower spring rate at the front is
desirable which usually means that a front antiroll bar is required to reach the equal roll stiffness goal.
All the remaining calcs are straight from Staniforth.
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Surrey Dave
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| posted on 14/6/03 at 08:43 AM |
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Spring Rates - WWW.KITCARMART.CO.UK is fab!!
I originally fitted 180 fr 140 r , but because of the way i did the rear axle brackets my rear shocks are 1" shorter than the front.
althought it rode OK the front felt too soft and the rears would bottom out .
so i changed them to 250fr and i put the 180's on the rear, this is better but still occasionally bottoms out.
i think the best solution would be to have longer shocks on the back(more travel) and go a bit softer on the springs probably around 140.
If you think about the front shocks have more travel anyway because of the angle they work at , where as the rears work straight up/down so to
compensate should have more travel, if i could be bothered thats what i would do , if i can find a 3.56 diff imight do the two jobs at
once.........
My car at: www.groovy42.freeserve.co.uk
[Edited on 14/6/03 by Surrey Dave]
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dozracing
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| posted on 17/6/03 at 07:03 PM |
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Sorry to confuse everyone, but i'm catching up with a post in the middle of all this.
My Anti-roll bar is made from SAE4130 chrome moly steel.
Kind regards,
Darren
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