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Old 2019-07-25, 02:46 PM   #1
SanJoseUnicyclist
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Bearing Housing Screw Tightness Question

My apologies for starting a new thread on this. I tried searching for an answer, but could not find it in the time that I had...

I ride a KH29 and have been riding more aggressively 3 times a week on trails with >20% grades, single tracks with switchback, severely rocky trails, etc.

I started to notice a lot of creaking in my uni, and found most of my seat screws loose. Easy fix. However, I was surprised to find that two of the bearing housing screws (one on each side) were lose. They were loose enough that I wonder if the only reason they did not back out the entire way was because the blue Loctite kept enough friction in the threads so they did not rotate freely after becoming loose...

Anyway, I put on a lot more blue Loctite and tightened all four screws again. This time, I tightened them more than I ever have before. I tightened them so that the tire would only rotate 1/2 a rotation when spun softly by hand. In the past, when I'd perform the "spin test" to make sure the bearing housing screws were not too tight, the wheel would spin freely and come to a gentle/slow stop. This time, the wheel still turns freely, but after only 1/2 a rotation comes to a fairly sudden stop. It's obvious that there is more friction in the bearings.

Can anyone speak from experience with this much compression on the bearings? First, I'm wondering if I actually need to tighten the bearing housing screws to be this tight because of the more aggressive riding. Second, I'm wondering if my bearings will be OK with this much compression, if I ride 3 times a week (10+ miles each ride).

Thanks very much in advance!
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Old 2019-07-25, 03:30 PM   #2
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You have them too tight. You should back them off until the wheel just spins slowly to a stop as before. As tight as you have them now, the bearings will wear out quickly.
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Old 2019-07-25, 03:37 PM   #3
JimT
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Tighter bolts and restricted bearings are not a good fix. For a reliable fix use longer bolts and lock nuts or carefully selected shim washers. Either of these fixes will solve the problem and allow bearing to spin free.

Lock nut fix: http://www.unicyclist.com/forums/sho...d.php?t=101676

Shim washer fix: http://www.unicyclist.com/forums/showthread.php?t=121500
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Old 2019-07-25, 03:49 PM   #4
song
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Somewhere on this forum, I read that if you give your wheel a good hard spin, it should make about 15 rotations before coming to a stop. Only half a rotation? Sounds like you will damage your bearings, if you haven't already.

To tighten the screws, I use a small hex wrench (3 or 4 inches long) and turn it as far as I can using only finger strength (no biceps, no shoulder or chest muscles), and if I spin the wheel after that, it will usually go about 15 rotations. I do not own a torque wrench, and this system is not very precise, but for me it has always worked.
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Old 2019-07-25, 10:55 PM   #5
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I only ever tighten using the long shaft of the hex key, with fingers only on the short shaft for the leverage. That way I can't over tighten the bolts. A quick nip every couple of rides and there is never a problem.
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Old 2019-07-26, 05:33 PM   #6
SanJoseUnicyclist
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Thanks, everyone. I really appreciate it. I'll loosen things up today. I've only ridden about 20 miles. Hopefully the bearings are OK.
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Old 2019-07-27, 09:02 AM   #7
Aali
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Quote:
Originally Posted by song View Post
Somewhere on this forum, I read that if you give your wheel a good hard spin, it should make about 15 rotations before coming to a stop. Only half a rotation? Sounds like you will damage your bearings, if you haven't already.

To tighten the screws, I use a small hex wrench (3 or 4 inches long) and turn it as far as I can using only finger strength (no biceps, no shoulder or chest muscles), and if I spin the wheel after that, it will usually go about 15 rotations. I do not own a torque wrench, and this system is not very precise, but for me it has always worked.
I have a torque wrench and have used 4 nm as a base level that I torque them to.
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Old 2019-07-28, 08:49 PM   #8
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Quote:
Originally Posted by song View Post
Somewhere on this forum, I read that if you give your wheel a good hard spin, it should make about 15 rotations before coming to a stop.
I just checked my 26" Nimbus. One good, hard spin and it does anything from 50 to 55 rotations. Now it could be that I am doing it harder than average (though I doubt that) or perhaps that my bearings are nicely worn in, or the weight of my (heavy) tyre. Whatever, It is a good deal more than 15 and the OP's half a turn sounds like the bearings must be crazy tight (or the brake is rubbing).
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Old 2019-07-31, 03:59 PM   #9
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Quote:
Originally Posted by Aali View Post
I have a torque wrench and have used 4 nm as a base level that I torque them to.
Between 4 and 5nm is the recommended torque for the Schlumpf hub. You can buy a bike wrench set to this value, it's not very expensive and quite useful.
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Old 2019-07-31, 04:04 PM   #10
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Between 4 and 5nm is the recommended torque for the Schlumpf hub. You can buy a bike wrench set to this value, it's not very expensive and quite useful.
Pierrox, you are french. France is in the origin of the metric system and later SI. If you write nm, it means nanometers. For Newton-meters it is N m or N⋅m! Capital letter and a space are essential
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Old 2019-08-03, 10:59 AM   #11
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Pierrox, you are french. France is in the origin of the metric system and later SI. If you write nm, it means nanometers. For Newton-meters it is N m or N⋅m! Capital letter and a space are essential
No no I was actually talking about an extremely small wrench.
My bad, you're right.
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Old 2019-08-03, 11:22 PM   #12
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Quote:
Originally Posted by pierrox View Post
No no I was actually talking about an extremely small wrench.
I've got one of them in my Quantum Mechanics tool box.
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Old 2019-08-05, 06:40 AM   #13
Aali
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Originally Posted by pierrox View Post
No no I was actually talking about an extremely small wrench.
My bad, you're right.
I am sorry, I started that nanometer nonsense to begin with. It has been bothering me ever since I wrote the post. Of course it should have been Nm
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Old 2019-08-10, 11:52 AM   #14
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Quote:
Originally Posted by song View Post
Somewhere on this forum, I read that if you give your wheel a good hard spin, it should make about 15 rotations before coming to a stop. Only half a rotation? Sounds like you will damage your bearings, if you haven't already.

To tighten the screws, I use a small hex wrench (3 or 4 inches long) and turn it as far as I can using only finger strength (no biceps, no shoulder or chest muscles), and if I spin the wheel after that, it will usually go about 15 rotations. I do not own a torque wrench, and this system is not very precise, but for me it has always worked.
This is perfectly good engineering. If you look at a set of spanners or hex wrenches (Allen keys) you will see that those for thinner bolts are shorter, hence less leverage. This is a clue to how much force the manufacturers expect you to apply.

I own a bike specific torque wrench for small Allen bolts, but your method is perfectly fine as long as done sensibly.
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