I am looking to upgrade to disc brakes on my Trek 6500. The rear triangle and the front fork are disc ready but the wheel sets are not set up to receive rotors. The wheels are 26 inch. New wheel set or swap the hubs? Is there another way I am not familiar with? I am leaning towards a new wheel set. My bike is obviously older. It's a hardtail and I was considering commuting to work with it this Winter. I have not ridden it much because sadly to say I have become mostly a roadie.
That being said I would like to convert it to Hydro discs if it were not too expensive.

Much more viable to just get another wheelset. You can shop very carefully and hard for disc hubs on the cheap; but you aren't, in all likelihood, going to be able to re-use your spokes (which is not really advisable anyway) because of lengths. So by the time you've bought hubs and spokes, relaced everything and trued 'em up, you'd have been ahead buying the wheels. Decent disc wheelsets can be found very reasonably now - - especially 26".


And no, I'm not even going to tell you about these little doohickeys:
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I think I may just buy a new wheel set. Looks like the way to go.

Would check that you can get the correct adapter for the rear before starting, early Trek disc ready frames used a 22mm fitting which is not supported by any current brake manufactures. Would check to make-sure you can still get the appropriate adapter, here's a relevant thread to start you with Installing Disc Brakes onto a 2000 Trek Frame « Singletrack Forum

Thanks.

22mm to IS adapter is a pretty easy fab from some 6061 angle:

i definitely prefer hydro discs and run them on all of my bikes. The least expensive way to get them is to go to Nashbar.com and get the Clarks EXO set. they are MSRP of $150 (usually BS) Nashbar has the best price for them at $49.99 for front and rear and it includes rotors. Don't buy them at that price. Keep checking back daily and within a month they will go on sale for 20% off and you will get them for $40.00 for the whole set.

If you search Google, you will find a bunch of reviews; both good and bad. I have them on 2 bikes and they are fine. They stop on a dime but the only caveat I would add is that they took twice as long to bed in the pads and rotors.

As long as you don't expect $400 performance, you will be pleased and for $40.00 for a complete set, you can't beat it.

As far as the wheels go. Just get a new wheel set, I tried the new hubs route and after buying spokes and having the LBS true them etc. it cost more than if I just bought a new set.

Good luck

Oh, and I am not affiliated with NAshbar, I am just a satisfied customer.

Great if you have a workshop equipped to do that sort of thing, the main issue as the OP has a bike that may need an adapter, knowing that this may be an issue would be something to address before commencing with the conversion, then looking at how to resolve the issue, either by DIY or by using an aftermarket part.

It doesn't seem like it would take much in the way of equipment. A clamp, hack saw, drill and file should it.