You open the pano roof half way. This puts the pin that rides in the shoe-hole about 100mm back from the full closed position. That's maybe what, 30% open?Hi Wayne,
To be honest, I've never replaced them myself. The official way is to disassemble the entire sunroof in order to replace it. But I have had also customers who pushed the entire carriage forward in the rail and then pushed the slides in with a little force.
You'll notice the pin is almost exactly as wide as the track it rides in, which means it is not captured at all. If all 4 shoes are broken, the whole roof can double in height as the front assembly "unfolds". Which is how most of us discovered it broke to begin with (at 110+ kph )
Anyways, the first one goes in easy because there is enough side play to put the shoe in the track, move the pin out of the way, slide the shoe to float over the pin, then push the pin into the hole.
The diabolical part is getting that second shoe in. Now that the first pin is in, there is ZERO clearance between the remaining exposed pin and the track. It makes it impossible to install the second pin. There is roughly 1mm of play in the track at best if you try to flex it open to slide the second shoe in. It's a total no go.
That's why 'they say' you have to disassemble the whole assembly. So you can slide the roof off the end of the track, put the shoes on, then slide it back on. That's a nightmare of a procedure for all of us.
The solution, is to file a groove in the replacement shoe using a round file, maybe 1mm deep. Once you are looking at all the parts, with one shoe installed, and the second one ready to go, you'll know exactly where the groove needs to go.
Then you hammer it into place using a brass punch (or steel if you are careful) while prying gently on the track. The combo of the smallest bit of flex in the track combined with the groove in the shoe plus the force of pounding (using a non-marring punch) is enough to make the shoe slide past the pin. Only just. Seriously, only just.
Now you have the whole thing done for 12 bucks. But one shoe is weakened.
How long with such an install last? no idea. My shoes broke because I opened the roof at 70 MPH on the freeway. That is a LOT of force on a big sail. Now that I have replaced them, I refrain from opening the roof on the freeway. I crack it open just fine because that's the backside, not the front. NBD.
I may have tried it once or twice just as a 'to heck with it' test, hasn't broken "yet". But yeah, it is what it is. But still, fully functional.
I did all that for 12 bucks, and no breaks in 2+ years. Your product has to do that, with a better lifetime, without making users file their own groove in the part, and still convince your customers your part is better despite being thinner in one small section. And that that is worth > 100euro.