# Front and Rear Spring Rates? ... and teaser pics



## Peanut (Nov 8, 2001)

*Front and Rear Spring Rates ... and teaser pics*

Does anyone have any info on the factory spring rates? Wanting to change rates and looking to base my rates on increases of the OE rates. I have measured the OE springs to calculate rates, but I don't trust my numbers. 

I'm currently on stock springs but am looking to do sleeved coil-overs around Koni inserts in the front and something yet to be determined in the rear. 



















Thanks!
P


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## Zambee500 (Jun 23, 2011)

I don't know much about suspension, so I couldn't answer your questions anyway. But wouldn't it matter which vehicle you have? The SEL and SEL Premium versions of the Routan, I believe, all came standard with the Mopar tow-prep package that uses Sachs Nivomat load leveling shocks. The S and SE came with non-Nivomat rear-suspension unless the original purchaser optioned up to the Nivomats. The Nivomats are much firmer than the non-Nivo suspension.

To add to it, Mopar makes three different Nivomats for these vehicles. Regular Duty, Commercial Duty, and European suspension. I don't know for sure, but presumably the Routan got the "European suspension" - unless Chryco is referring to a different suspension for the European market (but they are available for purchase here in the U.S.).

Also, there were a lot of changes made beginning with the 2011 MY. So 2009-10 could be slightly different than 2011-2013.

Seems like all those variables would affect the answer to your questions about rates, no?


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## Peanut (Nov 8, 2001)

It would matter, but I was hoping with spring rates, the model/trim that the spring rate is from would be noted. My biggest interest was to understand the stock rates and more so, the stock ride frequencies front to rear as ride rate splits get a bit kooky for cargo vehicles. The end goal is for more of a sport suspension.

Since I found nothing in my searching, this is what I have. I don't completely trust it and it's continually being tweaked but I'll share what I have now anyway (and in full disclosure, i have a 2015 Dodge Caravan R/T):

Front Spring Rate (Caravan R/T); 226 lb/in
Front Ride Rate; 1.2 Hz

Rear Spring Rate (Caravan R/T): 320 lb/in
Rear Ride Rate; 1.6 Hz

Spring rates are based on wire diameter, coil diameter, and coil count. Rates are summed for series springs for the pigtail and the main coil windings. I am using average coil diameter for the pigtail.


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## Peanut (Nov 8, 2001)

*New Ride Rates & Spring Rates*

Based on what I have I'm currently planning on raising the ride rates to 1.9 Hz front and 2.1 Hz rear and lowering the ride height about 1.5". That would put me in a 550lb spring in the front, and coincidentally, a 550lb spring in the rear. 

Wondering how the wet noodle chassis will like that.

I'm planning on using a modified OE strut bearing and have new upper spring perches out for quoting to accept a 2.5" ID spring. It looks like an 8" spring will work, but it's close regarding the total spring travel available, and I have a lot of potential stacked errors from measuring. I will be machining off the perches on the OE strut housings and welding new stops for a coil over sleeves as low as I can get it by the sway bar brackets.

I need to take the rear apart again to see what will fit but I think I can squeeze a 5.5" OD x 9.5" Spring in the back and use an adjustable spring spacer below in the rear beam spring seat:


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