Two questions
 

The back wheel of my semi-daily rider bound up on Tuesday morning. Taking it apart today, I found the freehub to be very loose. Is this a somewhat common occurrence? I didn't check to see if it might be stripped, but simply tightened it back up and moved on. 92 Schwinn Paramount
My other morning rider is suffering from very poor braking (practically non-existent). I recently built this one up and am wondering if the problem might be mis-matched levers and calipers. It's a 73 World Voyageur, with centerpull brakes and Shimano 600 EX levers.
As always, thanks in advance

seedsbelize, The freewheel will tighten when you're pedaling. The only way it can loosen is when you're coasting and either it wasn't installed properly or it somehow lost it's ability to freewheel, at least for a few moments. That event would be very noticeable. As hard as a freewheel is to remove, it maybe a case of both.(?)

Brad

^ But he said freehub, not freewheel. My experience with freehubs is pretty limited, so I won't venture to answer that question.

As to question #2, re brakes, it could be any number of reasons from old brake pads, to set up of the centerpulls, bad cables, dirty/greasy rims, etc. I haven't used those levers in combination with centerpulls. Assuming that's not the issue, my first instinct with poor braking is to check brake pads and rim surface. Are the pads new? If they are old, sometimes you can file the surface to expose softer rubber, but I find that once a pad gets too hard it's better to simply replace with new pads. Have you tried cleaning the rim surface? Do your centerpulls have the ability to adjust the straddle cable length or is it a fixed length straddle? If the former, I'd play around with straddle cable length and adjustments of the rim-to-pad distance to see if that makes any difference. I had some Weinmann centerpulls that gave poor performance when adjusted very close to the rims. How new/used are the cables? The rim width can play a factor too. Maybe a photo of your setup as is?

Thanks gaucho,
The pads are new Avid mtb pads cause that's what I could get. The cables and housings are new. The rim I've been using steadily, on a different bike, etc.,etc.. That's why I questioned the lever/caliper combination. I don't have a clue as to how to search something like that out. Hopefully someone will come along......And yes, it was the freehub that was loose.

If all the brake parts are new and working smoothly (including no binding of the cables or caliper arms), I wonder if your rim width is much different from the original that the brakes were set up for. That could possibly change the caliper geometry and mechanical advantage.

just sounds like the brakes are adjusted poorly or possibly binding. try lubricating the pivot points with some spray lube and make sure the pads are aligned properly and cable tension is correct. rim brakes are very simple brute force levers, and there's not that much that can be wrong with them.

...whenever I swap a wheel to a different bike and put on new pads, I always clean it and lightly sand the brake track with 220 abrasive paper. It probably won't help you, but it's a magical ritual for me. That's all I got from here. :o

I've swapped out freehubs for various reasons, but never had one loosen up in use. Could happen, I guess.

Freehub
 

The freehub cannot be tightened unless you remove the axle. So maybe it was the cassette.
A discription of the braking feel may help diagnose the problem ie the brake lever feels very solid but doesn't stop the bike, would indicate a setup problem.

In my experience, center pull brakes require a longer pull due to the bridge cable stretch. You might adjust the brake cables to minimize the clearance from brake pad to rim.

cassettes have really high torque requirements that most people ignore.

http://img.photobucket.com/albums/v7...aaP7030002.jpg

If it's the freehub coming loose, not the cassette, that's unusual. I'd check for serious wear inside.
If it's the cassette being loose, that's not uncommon, and I yield to bulldog1935's answer above. Been there.

As far as the braking, any time you mix braking, you can have good or bad results, never seems to be in between:

My key to overcoming this starts at the wheel: true true true.

A trued wheel allows you to move to the next part: clearance clearance clearance. Even if the levers won't pull the distance you need, a trued wheel can let you move those pads right up to the rim, 2-3 mm away, and have adequate braking even with cat/dog matchups on the braking system.

The third part, of course, is the condition of the cabling/housing/clamping.
You are an experienced wrench so this you already know.

Go forth and stop in peace, not pieces.

As for the first problem a slightly loose freehub this happen's but not often usually the result of it not being fully tightened and is usually fine if you make sure the bud is correctly seated and just retighten.

As for the brakes I can say from experience you should be able to get acceptable to very good braking out of that setup. Another thing to check since your running MTB pads make sure the washer stack is correct which alloys you to align the pads with the rim with slight tow in the brake goes between the 2 dish washers.
http://www.huskybicycles.com/Merchan...02/306-408.jpg
I have a very similar brake setup on my current daily rider and the brakes are very good better than most of the calber brakes I have used.
http://i1211.photobucket.com/albums/...psa3uzls2m.jpg