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Old 09-09-2020, 11:12 AM   #22
IansPlatinum
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Join Date: Jul 2018
Location: Texas
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Rear is very touchy in my experience

I had rear bilstein tourings + ipd overloads and it was terrible

With stock rate rears and some different shocks, its perfect for my uses.

Check out mikeP's thread on spring rates. I think volvo purposefully engineered the rear to have a harmonic frequency double that of the front...

~100lb front X 0.95 motion ratio ~= 95# equivalent
~126 lb rear X 1.5 motion ratio ~= 190# equivalent

notice that they're harmonically related (hint: one natural fequency is about half the other, and stock front & rear weights pretty even)... in other words, I think one should try to maintain that fundamental relationship between front & back rates, provided you keep your corner front & rear weight distribution about stock

or put simply,

front rate divided by rear rate should be about 0.7-0.8 for stock comfort

that's my personal conclusion but YMMV

edit: just realized you'd get ridiculous rear rates with that formula if you upped the front springs to 200s.
In that case I'd aim for harmonically similar spring rates, with front/rear rate = 1.4-1.6

so that'd leave you with rears right about stock levels, maybe a hair stiffer with fronts at 200
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Last edited by IansPlatinum; 09-11-2020 at 04:04 PM..
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