Matrix rims. My brother had an '84 Trek 560 and I had an '84 500. We bought both bikes new around the same time. Both had Matrix rims with non-stainless spokes and Helicomatic hubs. The rims didn't fail but they were nothing special.
I did the maintainence on both bikes and we were riding about 100 to 150 miles a week. Within 6 months both hubs had badly pitted cones and the dealer tried but could not supply replacement cones (they are a unique to the helicomatic.
So I built new wheels using Specialized sealed bearing hubs and MA40 rims with stainless spokes. I didn't think the Matrix rims were worth reusing with the eyelets already rusting and they were a chore to keep true.
I still have the Specialized hubs having replaced the cartridge bearings a few times and have used them on several bikes.
I really like the Trek bikes but on some of the lower end models they cut some corners on components - in my opinion the wheels - mainly the Helicomatic hubs, were the least durable parts.
Just my opinion. If anyone likes them that's great.