Should cranks spin freely in a new bottom bracket?

Discuss light weight issues concerning road bikes & parts.
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by Shrike

Installed a GXP bottom bracket in a frame few weeks ago and the cranks would spin beautifully. Few rotations with just a little push. Made me happy.

Removed that, and installed some Rotor 4130 bottom bracket and a Rotor BB30 crank this evening and it's like turning through sludge. Felt a bit sad.

Had a look around and see some people say that it's normal for them to not rotate easily as the bearing are loaded with grease. However, I spotted this:

They seem to make it look like freely spinning cranks are boss.

What's the score with this?

Also have a chain rubbing on outer ring (50T Q ring) in 50/11 position.

Just not the best evening really. :|

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by Nefarious86

Helps make cool videos if you remove the seals and grease ;)

Q ring rub isn't unusual at full cross chain due to the exaggerated shape

Have you set the bearings in the frame perfectly square and have the pre load correctly? If so try riding them to see if the seals free up.

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by Weenie

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Location: CO

by pdlpsher1

I have a feeling that most of the BB friction is actually due to the dust seals. Not the seals on the bearings but the seals that cover the bearings to protect the bearings from dust and moisture. Recently I found that my Praxis BB adaptor had a bad and dry bearing on the non-drive side. Upon disassembly I found water intrusion as the cause. The Praxis BB adaptor was free spinning when it was new. Now I suspect the free spinning was due to ineffective dust seals. I'm now trying a Wheels Mfg BB adaptor and I find this BB to have more friction than the Praxis BB. But I also feel that the new BB has superior dust seals.

You can test my theory by removing both dust seals and see if the crank spins more freely. Personally I would not trade less friction for poor reliability. I want a BB that I don't have to worry about for many years.

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by sancho3000

I just had the same experience with Rotor 4130 bottom bracket... I haven't ridden them properly yet, might get better. My other thought was that my mechanic damaged them during installation, because it took some muscle to push the spindle through. I plan on riding the 4130 for 100+ km and if it doesn't get any better, I have ordered HOPE bottom bracket just in case.

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