Trim Clips 101 - What You Should Know About Them
Pound for pound, the automotive window trim clip can be one of the most troublesome parts used on your restoration. For cars manufactured during the mid 60’s through the early 70’s there seems to be hundreds of variations which adds confusion – why so many different clips and which are correct for your application?
During the heyday of the muscle car era there was little focus on parts commonality where the manufacturers and designers seemed to have the freedom to design for each application. This coupled with a supply chain that was monstrous led to things like trim clip geometry being a bit different for each application. But just how important is the actual geometry for the clip to its function? Well… keep reading.
As it turns out, there are a few “standards” when it come to trim clips. The first, and most obvious is the way it is attached to the window channel. Here there are two types – the screw on and the stud mount. As the names imply, the screw on clip is screwed on to the window channel wall by a sheet metal screw with a wide, low profile head. The clip itself has a hole (rather than a slot) for the screw to go through. The stud mounted clip is characterized by a slot that the stud (which OEM’s welded to the side of the channel wall) slides into. In both cases the clip becomes fixed in its location relative to the bottom of the window channel which is good because this determines the height of the final installation of the stainless (or aluminum in some cases) window trim relative to the glass surface.
Things like manufacturing tolerances in the location of the welded stud and the popularity of the vinyl roof quickly exposed the limitations of the conventional vertical slotted stud trim clip and engineers began using a horizontal “ramped” slot. This ingenious development allowed for the clip to vary its height relative to the channel bottom to account for any variance in the stud location, or the use of a thick vinyl covering on a roof. Some felt the “floating” of the clip a bit too great, so some designed “teeth” into the slot to have it grab the clip once loaded against the trim. Honestly a neat idea of dubious value.
A quick aside regarding the trim clip stud itself – the manufacturers did standardize on the geometry of the stud, but there is a good deal of variation car-to-car regarding the spacing. Generally they are 5” – 8” apart with no stud closer than about 1.5” from a trim joint. Trim clip stud diagrams for many GM A, F and X body cars are available for free download from our website (www.beldenspeed.com). The height off of the channel bottom was very accurate from the factory as this is a critical dimension and can vary from car model and year produced.
The welded stud is available today and we recommend that as the best replacement choice, but it does require access to a stud welder. Since most don’t have a stud welder, there are 2 other options which work well. The first is a shouldered, zinc plated steel screw and the second an aluminum pop rivet – both are fine alternatives to the OEM weld-on stud.
So just how does a trim clip work? Well it’s essentially a spring with a catch (we refer to the catch as a “Nib”) that grabs the inner edge of the trim profile and retains it against the vertical channel wall and down against the glass surface. To release the trim from the clip you simply locate the clip and slide a hook (or trim clip removal tool widely available) and pull the clip inward toward the center of the glass (away from the channel wall) to release the trim edge from the “Nib”.
If that is all they do, why do they look like they do? Well some of it has to do with the way in which they are manufactured – some have little tabs or wings off to the side – these a generally just artifacts from the metal stamping process used to hold or locate the clip during a progression of forming steps – each manufacturer attacks it differently. But there are some parts of the geometry of all clips which are important to their function.
The “Tab” is the area that is adjacent to the slot and it’s bent toward the glass facing side and its purpose (aside from forming the slot) is to spring load (gently) the clip to the channel side wall. The “Slot” is the guide for the trim clip stud and the top of the slot fixes the trim clip location up and down. The “Retainer” is an additional tab which loads against the stud face and edge to retain the clip once installed. Note – ramped clips do not have a retainer as the head of the stud is retained due to the narrow-ramped channel. Finally, the most important part of the clip is the “Nib” which is the edge that catches the trim itself.
After all is said and done, all that really matters is the distance between the center line of the stud slot top spot and the “Nib” (“Y” dimension). While there are a few cases where the shape of the top of the clip will affect the clip’s function from some trim geometries, these cases are rare.
Now it’s really important to be observant when removing clips, or when buying clips because most people do not understand this simple fact. Pay close attention to this “Y” dimension and not just the general shape of the clip. There are clips that at first glance look identical, but are not and there are clips that look very different, but they are not.
Keep in mind that as you restore your car it is not at all unusual for you to find a combination of trim clips as you pull your glass. In the vast majority of cases it is because the glass had been pulled at some point and different clips used either in places or in total. Also, if you are having trouble installing your trim after setting your glass, don’t assume the clips are the problem. Yes, any manufactured product can be defective, but it’s usually the case that the glass height is the problem, or you simply have a clip with the wrong “Y’ dimension.
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