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| Caster adjustment https://www.ausmini.com/forums/viewtopic.php?f=2&t=56748 |
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| Author: | mini-dunger [ Sat Sep 05, 2009 3:53 pm ] |
| Post subject: | Caster adjustment |
Hi all I have just picked up a full adjustable kit for my clubman. I want to have a crack at getting it set up properly before I take it to a shop. Anyone know how to set the caster? cheers the rest I can figure out I reakon. |
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| Author: | sgc [ Sat Sep 05, 2009 5:40 pm ] |
| Post subject: | Re: Caster adjustment |
mini-dunger wrote: Anyone know how to set the caster?
Yep, I made up a gauge to measure the caster.. I'll go take a photo and describe it. You can get by without though.. with caster I find if the car tracks in a straight line with hands off the wheel under power, coasting and braking then your cross-caster (the difference between sides) is zero, which is what you're aiming for. If the two sides are different at all, then the car will want to pull one way or the other. As for absolute caster each side, the standard setting is +3º if I remember correctly. This gives the steering its self-centering tendency, but if you're running large diameter or wide wheels you'll have problems clearing the front guards with steering lock wound on. I just had my car's alignment set on a magic laser-alignment rig, and they set mine close to 0º. This gives fairly light steering, but still maintains (for some reason) self centering and clears the guards fine. |
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| Author: | mini-dunger [ Sat Sep 05, 2009 5:51 pm ] |
| Post subject: | |
thanks for that mate, I just have to get it as close as I can so I can get it out to places to get it registered. I will get it done by a pro once its on the road (legally) |
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| Author: | sgc [ Sat Sep 05, 2009 6:04 pm ] |
| Post subject: | |
mini-dunger wrote: I just have to get it as close as I can so I can get it out to places to get it registered. I will get it done by a pro once its on the road (legally)
If 'close' is all you want in order to drive it safely, you can do it without needing to know the absolute settings. Measure the standard caster bars' length from the flange on which the bush sits to the bolt holes which attach it to the lower arm, then set your adjustable arm to exactly that length. Fit both new arms this way, then test drive it. If it tracks in a straight line with your hands off the wheel, it's fine. If it pulls one way, try either increasing or decreasing (I forget which now) the caster on that side and test it again. When I did mine, I put one full turn on the bar each time, then test drove until it went straight. Mine took lots of adjustment, because my subframe isn't square and it pulled badly with the standard arms. |
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| Author: | sgc [ Sat Sep 05, 2009 6:17 pm ] |
| Post subject: | |
This is my caster gauge: 
This is bolted to the drive flange, and rotated so the pointer points exactly at the middle of the top ball joint. Then, the angle is read from the calibrations on the plumb bob: 
I also have a similar one for measuring the camber. |
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| Author: | blue_deluxe [ Sat Sep 05, 2009 7:34 pm ] |
| Post subject: | |
sgc wrote: This is my caster gauge:
This is bolted to the drive flange, and rotated so the pointer points exactly at the middle of the top ball joint. Then, the angle is read from the calibrations on the plumb bob: I also have a similar one for measuring the camber. Looks awesome, and not too hard to make with a bit of fine measuring. How did you find the locations for the degree? Just with a protractor from the centre point of the plumb bob? Cheers, Joe |
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| Author: | sgc [ Sat Sep 05, 2009 7:52 pm ] |
| Post subject: | |
blue_deluxe wrote: How did you find the locations for the degree? Just with a protractor from the centre point of the plumb bob?
Simple trigonometry. I measured a convenient length from the point at which the fishing line is tied, then scribed an arc at that length. Then using trig I determined the length along the arc for 10 degrees, then divided that up to get half-degree increments. Easy 
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| Author: | blue_deluxe [ Sat Sep 05, 2009 9:08 pm ] |
| Post subject: | |
sgc wrote: blue_deluxe wrote: How did you find the locations for the degree? Just with a protractor from the centre point of the plumb bob? Simple trigonometry. I measured a convenient length from the point at which the fishing line is tied, then scribed an arc at that length. Then using trig I determined the length along the arc for 10 degrees, then divided that up to get half-degree increments. Easy I get that, sounds pretty simple. And for the camber gauge you got a piece of sheet metal with a flat edge, and used the same method? Something to do for tomoro. |
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| Author: | sgc [ Sat Sep 05, 2009 9:17 pm ] |
| Post subject: | |
blue_deluxe wrote: for the camber gauge you got a piece of sheet metal with a flat edge, and used the same method?
Not exactly, that one is a piece of MDF but rather than place the gauge against the wheel or tyre, I have two philips-head screws in the side which are set to match the diameter of my wheels (or rather, a convenient flat on the wheels): 
This post describes how it's made
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| Author: | blue_deluxe [ Sat Sep 05, 2009 9:29 pm ] |
| Post subject: | |
Woops, i wrote too quickly and didnt think about it. I was thinking have the wheel off and up in the air, giving my accurately measured suspension perfect at full droop, but a tad excessive at normal ride height lol. Thanks for the guide. |
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| Author: | mini-dunger [ Sat Sep 05, 2009 10:30 pm ] |
| Post subject: | |
you guys are bloody guns I tell ya !!!!! Thats all I need to set it up. Would caster be affected by not having any weight on the suspension components? either way as long as I can make them the same I will sort it. cheers guys! |
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| Author: | sgc [ Sat Sep 05, 2009 11:01 pm ] |
| Post subject: | |
mini-dunger wrote: Would caster be affected by not having any weight on the suspension components?
Yes, because the point at which the caster arm attaches to the lower arm swings through an arc of radius equal to the length of the caster arm, the caster angle will differ slightly between full compression and full droop. What I do when I'm measuring mine is, with the car on axle stands lift the front suspension to normal compression with the trolley jack and then measure the caster in that position. But I really only do that to get the settings there or thereabouts; most of the adjustment to get it tracking straight is done as a result of road testing with the car on the ground. In your case, I'd just set your new arms to the same length as the old and tweak it from there. [edit] Oh, one thing to consider when setting caster -- when you tighten the nuts on the bush end of the arm, you're compressing the bushes and increasing the caster angle as a result. On the laser rig which measured the changes dynamically this amounted to over half a degree change. It's therefore important that you torque the nuts on both arms equally so you change the caster on each side the same amount, otherwise all your measurement is for nothing 
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| Author: | mini-dunger [ Sun Sep 06, 2009 12:55 am ] |
| Post subject: | |
I have to set my adjustable arms up from scratch because I have metro hubs and the caster is all wrong with standard length arms. |
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