Is your Shock Length (47.8mm) the free length measurement of the shock when it's fully extended? Or is that what you measure the shock length when it's on the car?

Fully extended, ready to run. Not on the car.

Forgive if this is an obvious question, but your shock length is measured eye-to-eye, correct?

yes, centre to centre.

Just bought the program. I intend to use it to better understand the settings/effects on my old school TC4 Club Kit. I'm a newbie running in VTA.

I have downloaded the TC4 kit setup. Based on the chassis measurements, this appears to be for the carbon fiber chassis kit. I have the old composite tub chassis. Granted, the suspension is essentially the same.

Won't having the composite chassis vs the carbon chassis make a considerable difference in setup results?

Thanks for your assistance and patience, I'm not an engineer.

The software assumes a completely rigid chassis and is really only designed to adjust the variable suspension components themselves. I had the same question about the thickness of my X-ray chassis a while back and this is basically what Bob told me. It's a cool program and I have used it successfully to setup 2 of my cars.

So basically you want the chassis as rigid as possible for the program to be the most accurate, of course the chassis flex is variable so it's best to start with what the program recommends and then you can fine tune at the track.

Good luck.

Cheers

Thank you very much for the quick reply!

What kilohertz said.

To include chassis flex would mean doing bending and torsion testing of every chassis produced. Not something that will ever happen.

I used the spring calculator for my Yeah Racing aftermarket shock springs. Plugging those values into RC3 yielded essentially the same setup as the comparable Associated springs.

I just picked this up a couple of days ago, will be a useful tool to help me wring out the last little bits of performance in my FTTC4.

It has been interesting comparing my FTTC4 setup to a couple other current chassis that I race against also

I'm just in the process of building up a file for the Sakura Advance 2k18 Evo. Nearly done!!

Just got a question about springs. According to RC3's built in calculator the springs should be c=2.1
But if I measure the force required to compress the spring a given distance, it works out at c=2.7

Which method is going to be more accurate?

(Fyi spring specs are 1.4mm wire, 14 mm ID, 5.25 turns, 20.5mm long)

Normally the spring rate calculator is within 10% of the actual rate. The easiest thing to get wrong is the number of "Active" coils. I just measured up a AE yellow spring with total of 5.25 coils. To get the number of "active" coils you need to look at the first and last coils and see if the start of the coil touches the next coil if it does then that coil is considered inactive so you subtract 1 from the coil count. Normally the first and last coils are considered inactive so in my case the number of coils is 3.25. Using ID 14.1mm wire dia 1.39mm gives a calculated rate of 3.06. The rate claimed by AE for this spring is 2.94 N/mm so it is close. If I have a rate from the manufacturer I will always use that value. If you have an accurate spring rate tester then that would be an even better value to use.

Cheers for the explanation Bob, I re-ran the calculator with 3.25 turns and it came to 3.38N/mm which feels about right, if a little on the high side. I guess there's going to be a bit of variation depending on the type of steel used in the spring?
I should really build a proper spring measurement jig as all of the springs I've measured so far have been off from the manufacturer's claimed figure and accurately known spring rates are crucial for RC3 to do it's job properly!

If you can accurately measure the rate that would definitely be the value to use.

Most springs are made from high carbon steel or music/piano wire. There are lots of other materials that can be used but those are the most common. That is what RC3 assumes.

There will certainly be some variation spring to spring just due to manufacturing tolerances. Differences should be small though.

I feel silly asking but...…. what am I looking at in the pic? I have an Xray T4. Is it the front/rear arm inserts? (toe etc.)

For example - My FF insert is 1 up/out. My FR insert is 0.5 out. My RF insert is center. My RR insert is 1 in.