Hi,
Need to help to measure/calculate Kingpin Angle?
Which and How to use the Laser tools available in the market to measure/calculate?
Laser will measure toe and camber directly. For caster you can look at the sweep, get a camber caster tool or try one of these.
Caster will involve a little trickery to measure. KPI, I’m not sure on.
Here’s a guide from Longacre on measuring caster. The process applies to karts as well as cars.
Caster / Camber Gauge
- Read to the center of the bubble.
- Camber uses outside vials and reads in 1/4º.
- Turn wheels 20º to R & L of center when setting caster w. vial type gauges.
- Find a level place to set up your front end.
- Attach the gauge to the spindle. If you have a magnetic adaptor be sure that the surface you attach to is machined square to the spindle and doesn’t have any nicks or burrs.
BE SURE WHEELS ARE POINTED STRAIGHT AHEAD WHEN SETTING CAMBER.
With the thread-on type adaptor be certain the spindle threads are free of burrs. Usually there are a few extra threads on the spindle. If not you will need to remove the spindle nut and install the adaptor in its place. - Rotate the gauge until the small vial at the end of the gauge shows level.
- Read the CAMBER directly on one of the two vials on either side of the gauge. Note that they are marked + and -. Read the line nearest to the center of the bubble. Each line is 1/4º.
- To read CASTER first turn the wheels 20º to the right when setting the RF and to the left when setting LF. If you don’t have a set of turn plates you can use the angles machined on the corners of the gauge as a reference. Turn the wheels until the angle is parallel to the side of the car. Rotate the gauge until it is level.
- Turn the knurled nob in the center until the center caster vial reads 0º. Now turn the wheels back past center to 20º the opposite way - for a total of 40º. Rotate the gauge again to level (DON’T turn knurled knob). Read the caster directly on the center vial. Read to the center of the bubble. Each line is 1/2º.
NOTE: If you need to measure more than 12º caster - racing karts for example - turn the wheel 20º and set the enter vial at negative 4º instead of 0º. Proceed as above and add 4º to the reading. This will give you a total range of 16º. - Adjust the caster and camber as needed. Each time you make a change bounce on the front end to settle the suspension. Remove the gauge and reinstall the spindle nut if needed.
NOTE: Adjusting the caster may have an effect on the camber and vice versa. Double check all your settings before finishing. Be sure to tighten all suspension bolts when done.
WARNING:
Do Not leave the gauge in the hot sunlight or store in a place over 120O F. Breakage of the vials could occur due to heat expansion. Replacements can be ordered from any authorized dealer or the factory. Replacement is simple with no loss of accuracy.
Can I ask why the need to measure castor? I know why we have castor and I know why you would want full, half or no castor. Other than making sure both sides are equal, which can be done with your pills, why the need to measure the angle?
Full, half or none are super subjective terms though.
Also, for karts that don’t have independent adjustment of caster and camber I’ve found it useful to plot out the respective camber/caster angles for each position. Especially if you have an OTK with 20holes in the adjustment pill.
If you want to add some (static) camber, without adding too much caster you can look at your chart and see what pill position will work best.
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Ok. I do have an otk with all the holes. But they are marked with arrows and use those as the reference in comparison to the screw hole holding in the pill. I also never mess with anything other than arrows straight forward or straight back for Neutral, full or half castor.
I can see how it could be subjective, but that should only be Kart manufacture to kart manufacturer. Castor for otk should measure the same across all similar model chassis and changes should result in same affect. Discounting and chassis damage or twist. I would think it would be the same for other chassis also.
Hi Bryan,
Thank you for engaging in this discussion.
The reason for the caster data and the Kingpin data is to understand the correlation and to understand and fine tune chassis setup for my son.
I agree with you Bryan, it’s all relative to each chassis anyway, so knowing the actual caster values isn’t really important. You can’t really compare degrees of caster from kart brand A and kart brand B.
You can get a digital inclinometer, zero it on the chassis rail alongside the fuel tank and then put it on top of the kingpin. This will give you an reasonable idea.
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