Steering Axis Inclination & Included Angle

In this video, we cover Steering Axis Inclination, Scrub Radius, and Included Angle. These are the first angles and measurements we are covering in our series of Advanced Alignment Angles.
Basic Alignment Angles video
• Basic Alignment Angles

[@brianlapointe4000]

Very well said. I’ve been struggling to find an explanation that makes sense so thank you

[@almamdani6564]

1i have watched several steering axis videos thus far this one is best. thank you for posting

[@DIYAutoHomeschool]

+Al Mamdani Thank you for your comment sir, I'm glad you enjoyed the video.

[@ColdWarVet607]

Great Job , excellent drawing, Ive seen so many videos that just drew in a weird stick figure & had no idea what that was or the concept of pushing down/pull up on the tire, now I do AND now I know why the steering wheel returns to the center!.

[@Rodrigo-sq2bm]

Great information! Sounds like you are very knowledgeable with this! Thanks

[@soyyyo4443]

4:45 is when my mind was blown and understood everything lol

[@gurpreetsingh-zl5iz]

How SAI is more directly related to weight projection and stabilization of the vehicle's weight ?

[@sungbaechang9723]

Can you check it again? About the positive and negative scrub radius. I think it is opposite.

[@zacstern1513]

how do you measure Steering axis inclination in a car

[@DIYAutoHomeschool]

+Zac Stern Hey, I'm sorry for the delay in response. Most automotive alignment machines will measure SAI when the alignment angles are measured for a typical alignment. Most often, this measurement is not really given any attention by the technician aligning the vehicle due to the fact that without damage from a collision or suspension modification, SAI will nearly always be correct if Caster and Camber are set correctly. However, without making the investment of 40 to 60 thousand dollars for an alignment machine and a rack to use with it, you can often take rough measurements of this angle. Old alignment gauges which are mounted to the hub can still be used, however, using these old things is a bit of an art-form and take some work to really get good with. www.ebay.com/itm/Magnetic-Camber-Caster-King-Pin-Gauge-Automobile-Car-Truck-Wheel-Alignment-Tool-/231769275020?hash=item35f6867a8c:g:53sAAMXQpPhTka41&item=231769275020&vxp=mtr This is a link to an example of 1 I found listed for sale on ebay, there are plenty of places you can find these, this is just 1 example. If you do get one of these gauges, make sure it is labeled as being able to measure "Kingpin Angle". In the old days, many vehicles had kingpins in lieu of Upper and lower Ball Joints, so "Kingpin Angle" is the same as "Steering Axis Inclination" Thank you for your comment and I hope this helps you in what you are trying to do.

[@AT-wl9yq]

SAI is the same line as caster, so when you do a caster sweep, SAI is measured.

[@gurpreetsingh-zl5iz]

why caster and kingpin inclination angle is required

[@DIYAutoHomeschool]

Caster & Steering Axis Inclination both help with the return-ability of the steering system to the straight ahead, but SAI is more directly related to weight projection and stabilization of the vehicle's weight. With the upper steering pivot more inboard of the lower pivot, the weight of the vehicle is far more stable than if the the steering pivots were placed with one directly over top the other. Caster does the same thing essentially, but adds stability to the steering geometry more so than the weight projection through the front suspension like SAI does. Thank you for watching the video and for your comment.