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Discussion Starter #1
I already posted this in the general discussion forum, but I need to find out the rear spring rate on the 2000 Insight. I'm having custom struts and shocks made and the manufacture would like to know so that they can figure that into the new shock equation.
 

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Hi Mike,

Sorry as you probably already know that bit of technical information is not in the Service manual. Unless another member has done something similar to what your trying and calculated the rate I don't know where else you can find it except to do the measurement yourself.

HTH! :)
 

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Well, here's the formula. However, if you're paying somebody to make new springs then you're going to have to take the old ones off, so it would be much better to measure them. Your spring guy can do that if you hand him the spring. They're not hard to take out.

The dangerous thing about the formula is that very slight errors in measurement can make a big difference in the result. Note especially that the wire diameter is raised to the fourth power...

http://faq.f650.com/FAQs/SpringRateFAQ.html
 

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Discussion Starter #7
I'm not planning on replacing the springs as the class I run in for AutoX says that the car needs to stay at stock height. The rear springs are a little light and soft, but I'm hoping we can make the shocks compensate for that. Thanks again for the formula.
 

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Discussion Starter #8
Dougie said:
Well, here's the formula.
Are the figures that are now in the formula, at the link, the specifications of the Insight rear spring, or just random figures?
 

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They have to be random. There's no way the Insight has 1000+ lb. in. springs. I bet they're somewhere in the 120-150 range.
 

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Those numbers are not for the Insight. I would use the formula for curiosity only.

If you're spending money for springs, especially if you want to change the rate and keep the same ride height, you're going to need to take the car to the spring guy so he can measure the current height, then take out the spring and measure the rate, and then fabricate a new spring that has your desired rate and an appropriate length.

If you go through this, let us know!
 

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Spring rates

Back in 11/01, I had a new set of custom-made coil springs done by CSS. I sent them an OEM front and rear sample. Dave, the engineer there, told me that the OEM fronts were at 111, and the rears were 90. I told him I wanted a 37% increase in the spring rate with a .25" drop in ride height as well. He said he couldn't do a progressive rate in the front due to engineering reasons, but was able to do so for the new rears.

According to Dave, the front increased from 111 to 148, and my rears went from 90 to the progressive rate variation of 92-123. I had this done at 17,750 miles, and now have over 40K miles. I've got no problems.

-Mitch
 

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Mitch, great info. Some questions:

How was the ride quality affected by the springs you had made? Is it a lot rougher?

Did it help keep the rear from bottoming over bumps (common Insight problem)?

Any chance the shop you used still has the specs and would be willing to make up some more as a group buy for those of us here?

:D
 

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I wouldn't say the ride quality is alot rougher, given the aprox. 33% increase in spring rate up front. Since the rears are progressive rate, with the low-end rate almost the same as the OEM rate, this helps out with ride quality on the rear end.

I rarely have experienced bad bumps with my Insight, mostly because the road quality here in Palm Beach County, Florida is in great condition compared to most of the U.S. Thus bottoming out hasn't been an issue.

CSS likely still has all the specs from the Insight's springs, since several months after I got mine, another Insight owner had them make him springs (he chose a different spring rate increase and ride height decrease if I recall correctly)without him needing to send them a sample pair.

CSS allows you to choose the spring rate and ride height change that you want. You can choose powder-coat or paint. You can also have them cryogenically heat-tempered.
 

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Cool. Got contact info for this CSS outfit?
 
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