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As you know, in some services, it is necessary to apply brakes to prevent rotation of wheels or crankshaft. It is common to have an assistant apply brakes firmly for you but I was thinking about other ways to do it alone. Some mechanics put a long screwdriver between disc rotors and calipers to produce the same effect but I don't like this idea because it may damage both of the parts. After thinking for a while, I came up with an idea. I can put a long iron bar with one end on the ground and the other end attached to one of lug nuts. This way, I can use the weight of the car to lock the disc rotors. I can use two bars to distribute the force between two lug nuts. If I put transmission in gear (in a manual car), I can also lock crankshaft through this method. In the following picture, iron bars are shown in red and lug nuts in blue. I got this idea from a similar tool which is used by Honda to lock crankshaft pulley. What do you think? enter image description here

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  • I can’t see how the top bar in your picture will do any good, there is nothing to lever against.
    – HandyHowie
    Sep 13 at 13:24
  • @HandyHowie - Both bars are levered against the ground. It is similar to the official method Honda uses for locking crank pulley. Sep 13 at 13:27
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    The bottom bar is levered against the floor, a stud and the hub centre. The top one is only on a stud and the floor, so it will rotate on the stud with just a little force. If you are relying on tightening the nut to stop it rotating, you may well snap or strip the stud.
    – HandyHowie
    Sep 13 at 14:26
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I wouldn't use the way you're talking about, because you are pushing against the ground with whatever bar/lever you're talking about. While it might not happen, there's a possibility this could force the car off of the jack stand if the right pressures were applied, which would lead to a big mess.

If the rotors are vaned, sticking a screwdriver down the vanes and allowing the rotor to rotate around to the caliper is by far the easiest and the safest way of doing what needs to be done. There should be no issue with either the caliper or the rotor, as remember, these parts are made to withstand thousands of pounds of stress on them (think about stopping the weight of the car). In doing so, there's almost no way this action in and of itself would cause a safety concern like your method would, because the parts are pressing against each other.

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  • @Paulster2 - The highest amount of torque I need to apply to the wheels or the crankshaft is no more than 115 lb-ft which I think is not high enough to lift the car off of the jack stand. I can test this before using this method. Is there any other problem with my method except lifting? I prefer not to use calipers as stoppers. Sep 13 at 13:03
  • You can do anything you want. I'm telling you your plan is a safety concern, but as always you are always free to do as you please and I take no responsibility. As for using the calipers as "stoppers", it's not like they don't get used every time you stop the car. What I've told you is a completely acceptable method for keeping the rotor from turning, which does not involve any special tools. Sep 13 at 13:09
  • @Paulster2 - I edited my question and added another picture. Is that what you suggest? Sep 13 at 13:20
  • @NarimanAsgharian I know somebody who managed to make his vintage sports car fall off improvised jack stands while just removing a rear wheel. The end result was that the exhaust system ended up inside the car, after cracking the fibre-glass floor pan from one end to the other. But do whatever you want, as Paulster said...
    – alephzero
    Sep 13 at 13:59
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    I don't have the means to post an image, however, what I'm suggesting is very easily visualized. Look at the rotor on edge. You have two friction surfaces (inside outside) which if you're looking at it correctly, you cannot see them. You see the vanes of the rotor. Shove a small screwdriver into the slot between the vanes. Rotate the rotor around until it is stopped by the caliper/brackets. To me that seems pretty straight forward. Obviously, if the rotor doesn't have any cooling vanes (solid rotor ... some rear ones are this way), you can't do this. Sep 13 at 15:32

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