| Re: DRM Trailing arm bracket install Banski Trailing arm install |
Subject: Re: DRM Trailing arm bracket install Banski Trailing arm install by astock165 on 2009/9/23 17:37:30 Quote:
That 0.4mm (.0157 in) extra clearance would account for much more slop than the 0.125 mm (.005 in) difference between a 16 mm and 5/8 in bolt. I'm unclear as to why the original design being a bushing would matter? Bushings and rod ends both use the bolt as an anchor point. If the hole is 16.4mm diameter, any bolt that is 16 mm or 5/8 in is going to rattle around in that hole causing slop. Quote:
The only way they'll act like a saw is if the nut is not properly torqued and the bolt is allowed to move back and forth axially.[/quote] Quote: BrianCunningham wrote: That's not entirely true. Let's take the example of the camber rod bolts in the knuckle. I supply a bolt that is 5/8 in diameter x 4" long. If you look up a McMaster Carr Grade 8 bolt that is zinc plated in that size (pretty typical application) you'll find p/n 91257A810, the drawing of which is shown here: [IMG]http://i11.photobucket.com/albums/a196/turban65/91257A810L.gif[/IMG] As you'll see the thread length can vary up to a 1/2" in length. If the flange thickness of the knuckle is 0.5" per side and the width of the spacers and rod end is 1.7 in (the approximate length of the liners used in stock bushings and most urethane replacement bushings) that requires a minimum unthreaded length of 2.7". Now add in the thickness of two 5/8 wahsers. If we use McMaster 90126A035 (a 5/8" washer whose thickness can range from 0.074" to 0.121", [B]and that's a thin washer[/B]) the required unthreaded length is approximately 2.942 in. To satisfy that condition you would have to use a 5/8 bolt that is 5" in length (we'll use McMaster 91257A814 as an example), which is shown below. [IMG]http://i11.photobucket.com/albums/a196/turban65/91257A814L.gif[/IMG] You can see that you'd have to use a bolt that is at least 1" longer than the 4" bolt I supply. Now let's take another look at the 4" bolt condition. From what I've seen on the components I supply the threaded length is typically 1" to 1-1/4" long. Some are 1-3/8" but I haven't seen one yet that was the full 1-1/2" thread length. If we use use an average threaded length of 1-1/4", that makes the unthreaded shoulder 2-3/4" long. Subtract from that the 1.7" width of the spacers and rod ends, the two 1/2" flange thicknesses and one of the 5/8" washer thicknesses and you are left with 0.071". This should mean that at an 11 pitch thread, there is less than one thread pitch in shear. [IMG]http://i11.photobucket.com/albums/a196/turban65/untitled.jpg[/IMG] Now admittedly I'm making an assumption that the flange thicknesses on the knuckle are 1/2" at the camber rod. Since my car is currently in storage I don't have access to it to measure it. However, if the flange thicknesses are greater than 1/2" you could end up with no threads in shear. I'd be interested to hear from the C4 guys what their knuckle flange thicknesses measure at the camber rod? If you wish to measure that and post them back here we could figure out if there are any threads in shear, even @ worst case. |
