JC
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| posted on 9/1/06 at 08:18 PM |
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Midi front spring rates
My Midi uses standard(ish) Locost front suspension. I am about to splash out on Protech shocks for the front and need a ball park figure for front
spring rates. Using some of the maths from a Staniforth book suggests a rate below 100lbs/inch, however Protech said 160ish was a more normal rate.
Whats a good ballpark? (The back struts are standard Fiesta and my maths says that they are 175lbs/inch).
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Mansfield
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| posted on 9/1/06 at 09:14 PM |
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Cant help with your spring rates, but when can we see more pictures of your build?
I am sure I am not alone in looking forward to viewing them.
David.
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v8kid
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| posted on 10/1/06 at 08:33 AM |
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Usually the roll stiffness is higher at the undriven end. That means more of the cornering force is taken by the front in your case leaving more grip
for the rear tyres to accellerate out of the bend.
It also gives nice and safe understeer characteristics - handy on the public highway.
The spring rates depend on the geometry of your suspension and you would haver to do some sums but the figures you are talking about sound low to
me.
An alternative method is to try some springs and check out the handling - they are only about a tenner each after all.
If you want to be motr scientific but can't be arsed doing the calculations you can measure the spring rate using corner weight scales.
I made my own corner weight scales and they are the dest thing I have ever done for the handling - there is no doubt from my experience a well set up
car is a transformation to drive.
Happy tweeking!!
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JC
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| posted on 10/1/06 at 09:39 AM |
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Guess I'll buy springs and tinker then!
David- Build progress has been limited recently -l been gathering all the parts for the next stage - getting it on wheels, whilst also contemplating
the gear change. Not helped by John, who is helping me, moving house! Pre-Christmas photos on website, will be working on gearchange tonight!!!
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nre
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| posted on 12/1/06 at 11:28 AM |
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JC,
Came across your project last week, looks very interesting. On spring rates, yes it will depend on the exact geometry, but as a rough reference my
mojo is running 400lb/in front springs. This is great for the track but a little stiff for the road, but I would agree that your initial stab at
100lb/in sounds too low. Most locost style cars run in the 200-300lb/in range on the front, so I'd be tempted to start at the bottom end given
your car will be lighter up front, so another vote for 200lb/in as a starting point, with the intention of some 'development work' once
you're on the road!
Cheers,
Neil
Sylva Mojo Zetec on GSXR750 throttle bodies...
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Including the Star, Leader, Striker, Phoenix, Fury, Jester, Stylus, Mojo, Riot, J15 & Vectis
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Fred W B
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| posted on 12/1/06 at 11:44 AM |
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I am starting with 175 lf front, 200 lb rear. also using Protech's
I did a spreadsheet for calculation of suspension travel and spring rate, from first principles, as described by Allan Staniforth.
If you email me I can send it to you, if you like.
Cheers
Fred WB
 
rates
[Edited on 12/1/06 by Fred W B]
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