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Making sense of bump/rebound settings
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gimmesomeshelter
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Joined: May 08, 2004
Posts: 1327
Location: San Carlos, CA
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PostPosted: Wed Feb 18, 2009 10:13 pm    Post subject: Making sense of bump/rebound settings Reply with quote

Hello-

Iíve stumbled across come bump/rebound data for various Koni shocks, but I'm having trouble understanding what it means.

First, I've posted a link to a chart displaying rebound/bump data for Koni shocks meant for a 356. In general the trend was to have a softer shock. The final ones left the factory with rebound/bump settings of 140/20 (front) & 80/20 (rear).

http://www.porsche356klubb.se/Stotdampare_356_eng.pdf

Here is a link to a page on RatWell's site:

http://www.ratwell.com/technical/Koni.html

If you look at the settings for the 80-1349 and 80-1350's you will notice two things. First, the ratio of rebound/bump is much lower. Second, the rear shocks are, unlike the shocks for a 356, stiffer than the front.

I contacted Koni and asked them for the valve settings of these four shocks. While they were very helpful, they weren't quite ready to hand over all their valving data to just anyone with an email account. Wink They confirmed that the 356 front shocks have softer bump settings than a comparable front VW shock. They also confirmed that the rear shocks for a 356 are softer than the rear shocks for a VW.

So what does this all mean? I suspect that a shock with a softer bump setting will provide a softer ride...but why would Koni have such stiff settings on a 'people mover' type car like a VW? Did Porsche get all the R&D time and VW get a quick once over? If I want my VW to drive like a 356, should I try to mimic the Koni shock settings used on a 356?

Thanks,

Paul
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henry roberts
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Joined: February 24, 2003
Posts: 1157
Location: australia
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PostPosted: Thu Feb 19, 2009 3:19 am    Post subject: Reply with quote

i'm only taking a stab in the dark but...


wouldn't both the sprung to unsprung weight ratio and the front to rear weight bias be different between a beetle and a 356 hence different settings, plus the intended speed range of each vehicle.

from memory i've read that you can run a softer shock on a car with a higher ratio of sprung to unsprung weight while retaining the same road surface tracking. (no idea if a 356's has a higher ratio than a beetle though)
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