Worn rims replace BOTH rim and Hub?
 

If the rims need replacing from several years of riding, is necessary to replace the whole wheel? Or can the hub be reused on a new rim??

The rim/hub is a 9 speed Bontrager Race Lite.

There's no reason to replace the hubs if it's just the rim that's shot. Lace your hubs to new rims. While you're at it, you might as well disassemble the hub and clean/regrease the bearings.

If the hub is fine, then there is no need to replace the hub. However, you might want to compare the cost of a new wheel set versus the cost of a rebuilt wheel (cost of new rim + lacing/truing cost). There are some deals out there for wheel sets.

+1 for keeping the hub. I used to race my velodrome bike on 20 year old Campy hubs after I had repacked the bearings. The only reason to get a whole new set of wheels is if you really wanted to upgrade or if you found a set for less $$$ than the rims and spokes would have cost.

If the old spokes were well tensioned and trouble free you should reuse them too, as long as your new rim has the same ERD as the old one. But do not disassemble them from the hub. Tape the old rim to the new one and transfer the spokes one at a time.

See Reusing Spokes by Jobst Brandt.

Take the hubs apart and look at the bearing races and cones. A light reference mark where the bearings have been running if fine but pitts in the metal is bad. Cones are replaceable if they are pitted, but not cheap, but the races are not. Assuming everything is in good order there is no reason not to reuse the hubs.

After several years of riding, and having worn the rims to warrant new ones, I would highly encourage you to replace your spokes as well. Mr Brandt states that there is no reason to replace spokes on a "relatively new wheel". I doubt your case qualifies. Other than that, no reason to get rid of your old hubs if they're still good. Recycle is literal in the biking world.

This thread is making me want to lace my old hubs on a new set of rims.

How many miles is a "what is a relatiavely new wheel?" Do I need a special tool and alot to strength to lace the spokes and get the tension right?

If the hubs are good, recycling them is fine unless economics dictate otherwise. Often, a pre-built complete wheel is cheaper than a new rim, spokes and labor to assemble them to the old hub.

I have a couple of perfectly good used hubs in my parts box that would be more expensive to reuse than to buy an all-new wheel of comparable quality. It's a shame but that's reality.

Wheelbuilding is an art and a science that only comes with experience. I've built several wheelsets and it gets easier with every new wheel. Tools I use are a spoke wrench, a $40 truing stand and a $60 tension meter.

Unless you want to do it yourself (which is a very rewarding experience), you should have your LBS relace the old hubs to the new rims, then true and tension them.

Regarding spokes, if the new rims have the same ERD (effective rim diameter) as the old rims, you should be able to reuse the old spokes. Spocalc has the ERD of most rims in its database. Rim manufacturers will often have the ERD of their rims on their websites, or you can measre the ERD.

Some good advice in here. Thanks everyone!