GTM Owners Club Forum

Measuring castor angle
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Author:  kano nordie [ Tue Oct 20, 2015 6:12 pm ]
Post subject:  Measuring castor angle

Anybody out there with and easy solution to measuring castor angles?
I have a Trakrite bubble gauge with a magnetic base, great for camber angles, but the only way I can think of to measure caster is to temporarily remove the steering arms and fit a bracket with a flat base machined at 90degree to stick the Trakrite onto.

Author:  Ken555 [ Tue Oct 20, 2015 7:24 pm ]
Post subject:  Re: Measuring castor angle

Make sure your on a level and even surface, and a couple of glossy magazines, (Not that type), and a protractor or someway to measure 20 degrees

You already know how to measure the camber angle so this is how to measure the caster.

With the wheels on the magazines and pointing straight ahead,
Turn steering wheel to the right 20 deg get someone to hold the wheel steady

Use the camber gauge as you normally would at 90deg to level surface, adjust the gauge to read ZERO.

Now turn the steering wheel left till you reach 20deg in the opposite direction (total of 40deg) and hold wheels

Without altering the camber gauge setting will be your caster angle

repeat on the left side wheel

Author:  Ken555 [ Tue Oct 20, 2015 7:26 pm ]
Post subject:  Re: Measuring castor angle

Forgot to say, if the gauge doesn't read far enough, set it to -4 degrees and then turn, then add 4 to final angle.
Keep you foot on the brakes when doing the turning.

Author:  kano nordie [ Tue Oct 20, 2015 9:03 pm ]
Post subject:  Re: Measuring castor angle

As Baldrick used to say I have a cunning plan, cheers Ken, I'll give it a try.

Author:  Ken555 [ Tue Oct 20, 2015 10:11 pm ]
Post subject:  Re: Measuring castor angle

The magazines are to allow the wheels to slide around, I've heard of people using greased plates, or proper (built) turntables

Author:  Yoda74 [ Tue Dec 15, 2015 2:41 pm ]
Post subject:  Re: Measuring castor angle

What do you put right first, Caster or Camber?
Or doesn't that make a difference?

Greets Harold

Author:  Ken555 [ Tue Dec 15, 2015 4:35 pm ]
Post subject:  Re: Measuring castor angle

Both is the correct answer :lol:

But I would do camber first, then castor, then camber, then castor, I think you get the drift.

Author:  gtmdriver [ Wed Dec 16, 2015 12:03 pm ]
Post subject:  Re: Measuring castor angle

Yes. As you adjust one it will alter the other so you just have to faff about with it till you get them both as you want them.

Author:  Yoda74 [ Thu Dec 17, 2015 9:42 am ]
Post subject:  Re: Measuring castor angle

Adjusting one influences the other, so keep on adjusting both untill you are satisfied.
The car has to be on all four wheels when measuring castor or camber I guess?
Is there an easy way to measure the 20° steering angle?
I will fit HiLo's in the front and adjust the ones in the back to get some more ground-clearance.
Is it best to get this sorted first before adjusting camber and castor?

Author:  the other Tim [ Thu Dec 17, 2015 10:12 am ]
Post subject:  Re: Measuring castor angle

Height first and corner weighting (quite easy with hi-los) then castor/camber. Mini but it gives you the idea ... eer_Basics

Author:  Yoda74 [ Sat Mar 12, 2016 5:12 pm ]
Post subject:  Re: Measuring castor angle

Hi guys,

I have fitted HiLo's, adjustable tie bars and adjustable bottom arm to the front of my Gtm.
I'm trying to get it alligned now.
Hight is ok now.
I'm struggling with camber, Caster and toe-in.
After hight I adjusted the toe in.
After that I adjusted camber.
Then I drove around to see how it handled.
Steering to the left was easier then steering to te right?!
Also it was a bit nervous.
Maybe the Caster is far of I thought.
Should I take the difference between the two measurements in degrees when I steer 20 degrees to the left and 20 degrees to the right?
For axemple: left wheel, -4,25 + 2,25 = 6,5 total?

Thanks guys

Author:  WEST [ Wed Mar 16, 2016 2:16 pm ]
Post subject:  Re: Measuring castor angle

It takes a bit of time and chasing to get a sensible setup when you are working from a blank sheet of paper with all the adjustable parts.

My method

Set all lower arms, tie bars to the same length if you already have negative camber arms to copy set your adjustable arms to that length.

Set steering arms and rear toe locks to the same length side to side and something sensible.

Lower car and set ride height I suggest 10-20mm lower on the front.

Now set toe to 0 front and back.

Now set camber and castor, they effect each other as you make adjustment, take notes of how many turns you add/remove and do the same to the other side to get the car very close to where you want it. Your method of adding the values sounds sensible.

Once you are close to your setting for camber and castor check the other side is close too.

Now set the toe to the desired setting.

Keep an eye on ride height as you jack up and down and bounce the car to settle between changes. Take regular measurements.

Then go back and check camber and castor and now start to find the exact settings you want camber, castor then toe.

Then do the rear of the car. What I did, after finding the tie bar length needed for the front I set the rear to the same length. Then repeat the above.

Once the car is set, go for a steady short drive to settle the car, then adjust the ride height back to where it should be, I always find my car needs to settle in ride height after being jacked up and down changing settings.

If you have not corner weighted the car keep the Hilos the same height length side to side.


Author:  Yoda74 [ Wed Mar 16, 2016 8:58 pm ]
Post subject:  Re: Measuring castor angle

Hi Neil and others.
I put the same question in the cox/coupe section.
I suggest we'll take the reactions to my troubles over there, central in one topic.


@Neill: I Will copy your reaction to that topic if you Dont mind.

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