1g motion ratio??

[rkuhlen]

Has anyone measured the motion ratio on a 1g front and rear suspension. The more people that have and can post up, the better. Just trying to get the best answer I can before running some calculations I need. I looked through the archieves, but didn't find much on it except an estimate for the 2g's. If not, I'll have to try to measure it with the old rod and dial indicator trick.

Thanks

Ryan

 

[jtmcinder]

Your front is about .90 and your rear is about .84.

- Jtoby

 

[DG-FNR]

This is one of those things where you REALLY REALLY REALLY want to measure it yourself, and not trust "internet sources" except as a possible sanity check.

It's not hard. It's a little bit time consuming, but not hard.

What you need is a couple of 2" dial indicators (easily and cheaply availible at places like McMaster-Carr, JL Industrial, or Enco - google is your friend) a floor jack, and some pushrods that you will fabricate.

What you want to do is remove a shock/spring from each end of the car, and then bolt a chunk of metal rod to where the shock bolts to the suspension. This rod passes through the hole that used to secure the top of the shock.

Stick one dial indicator on the end of the pushrod, stick the other on the wheel hub, and move the wheel in 0.10" steps (one sweep of the indicator) and write down the change at the "shock" pushrod.

Ideally, you'd do this through the whole range of motion. "Good Enough" is start at full droop, and come down 2"-3"

Be precise! You care about +/-0.002" And be aware that the motion ratio typically is NOT constant - it's a curve - so you want to capture the first inch or so in bump as closely as possible.

Good luck!

DG

 

[jtmcinder]

Dennis is correct that you learn something by doing the measurements, but sometimes people have better things to do with their time. Everyone needs to be able to trust some sources (even those with internet access) or else everyone will be stuck doing everything from scratch.

For example, even Dennis does not suggest that everyone buy their own shock dyno. Instead, he suggests that you send your shocks to some business and have them measure them for you. Note, however, that this requires that you trust the operator of the shock dyno to be competent.

In a similar vein, you can look up what some trustworthy experts have found the 1G motion ratios to be. I gave Eric Stemler's data (.90/.84) in my previous post. To this I can now add Nick Drake's: .92/.844

I have no numbers of my own since I have never worked on a 1G, but these two guys are both in the top five with regard to setting up 1Gs, so I think you can use the numbers.

- Jtoby

 

[rkuhlen]

Just looking for a sense check. I'll be measuring my project car, but for now the parts car is in the garage. If enough people had measured it independently and all came up with the same number, I would use it (no need to re-invent the wheel). I think I'll go ahead and measure it anyway since I have spare assemblies and the fabrication work needed to do so is not that difficult.


Thanks again

Ryan

 

[jtmcinder]

Sounds good. Please post what you find.

Note that motion ratio is not a single value; it's a curve giving the ratio at all points of suspension travel. However, since what most people care about (and what gets reported when a single number is asked for) is the ratio in the area of the static height, please report the ratio for travel between +/- 1/2" of this. Thanks.

- Jtoby