Bottom bracket bearings

Discuss light weight issues concerning road bikes & parts.
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SuperSix2018
Posts: 26
Joined: Mon May 06, 2019 8:00 am

by SuperSix2018

How freely should new bottom bracket bearings spin? I purchased some new SRAM Road BB30 and they barley spin in my fingers. Once pressed in and with the cranks etc installed but with no chain it doesn't seem to spin many times freely.

Is this normal??

Cheers

ChiZ01
Posts: 345
Joined: Wed Jan 01, 2014 6:20 pm

by ChiZ01

depends where bearing will be used

SuperSix2018
Posts: 26
Joined: Mon May 06, 2019 8:00 am

by SuperSix2018

Depends on where it is used? It's a bottom bracket bearing so that is where I will be using it.

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Lewn777
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Joined: Thu Mar 09, 2017 5:35 am

by Lewn777

Generally not being free spinning is a sign that the bearing will last a long time as there is plenty of grease in the bearing and sometimes a tighter ball to race tolerance as long as nothing feels grindy or notchy or draggy. Chinese bearing makers often make amazingly free spinning to impress dumb customers that somehow equate a free spinning bearing with quality. The truth is you can make any bearing free spinning by removing the grease and putting in dry lube or lighter or less grease and making a bearing looser against the race. It just depends how much you value constant maintenace and performance vs durability. If I was to make a crit racing bike or hill climber that sees only a few hours of riding a year I might try low friction high quality steel or ceramic bearings with very little or light lube. For my main 20,000kms a year bike I want the most durable bearings possible.

Cleaner
Posts: 114
Joined: Wed Oct 28, 2009 7:13 pm

by Cleaner

My experience with the SRAM BB30 bearings is that they are not free spinning when throwing the crank by hand. When new they typically will be well packed with grease to keep out contaminants as mentioned previously. The grease and seals are the largest contributions to drag in these bearings and is to be expected. Any quality bearing will exhibit the same behavoir when double sealed and fully packed with grease. When pedaling you should not notice anything about the bearings spinning.

MaxPower
Posts: 114
Joined: Fri Sep 20, 2019 9:30 pm

by MaxPower

Free spind of a crank depends on many factors. frame tolerance at the BB shell, tolerances of the bearing outer race, inner race, seals, balls, cage, ball and race material, what type of grease or oil used, how much of it (filling grade), crank axle tolerances, preload on the bearings, bearing type (angular contact or radial bearing)... And probably more.

you say SRAM crank, i can't remember if the BB30 stuff is GPX as well or not.

But, a spind test is kind of pointless. A crank should always spind freely without any click og clank noise and with minimal/lateral playbas recommended by the manufacturer.

I run angular contact bearings as i am a idiot concerning using very low preload torque (BB86 shimano) and angular contact bearing seem to give my are click free BB in contrast to radial bearings.

There id a reason why ceramic bearing companies (like ceramic speed) don't offer angular contact bearings for BB. They are higly durable with the correct preload, but the design has always higher friction compared to the radial design.

alcatraz
Posts: 2572
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

Yeah those bearings have thick grease in them. Go for a longer ride and then spin. Modern grease should become thinner when it heats up.

Also check that the preload isn't too high. Have just enough so there isn't any play sideways.

Also you could have bottom bracket shell issues but that's a frame problem with few solutions.

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Alexbn921
Posts: 332
Joined: Wed Apr 10, 2019 6:39 pm

by Alexbn921

Bearing drag comes seals and grease. Sram BB bearings are just okay when it comes to spin. 4-6 would be normal with a well aligned BB shell and correct preload.

If you hear grinding or the crank only spins 1-2 times then most likely your bb shell is out of round, out of diameter spec or out of alignment. In this case it will destroy the bearings and cause creaking.

This is the main reason aftermarket 1 piece BB's exist.

Steel is better than ceramic. Ceramic is never the answer to the problem.

bm0p700f
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by bm0p700f

Also how a bearing spins with no load tells you nothing about how they spin with load.

If the bearings are turning smoothly then dont worry.

Seals loose contact with load so non contracting seals loose more contact and let more grime in.

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ms6073
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Location: Houston, Texas

by ms6073

SuperSix2018 wrote:
Tue Oct 15, 2019 12:29 am
Once pressed in and with the cranks etc installed but with no chain it doesn't seem to spin many times freely.
I am going to take this back to basics and ask which crank and when inserting into BB, did it slide in by hand or did it require external force with mallet to get it all the way inserted? If it took external force with a hammer/mallet, then I suspect this is causing the bearings inner races to get distored/displaced and may possibly be the reason the crank does not spin very freely/ I observed this with a Hollowgram SRM and after carefully pressing in new Enduro BB30 bearings, I had to use a dead-blow hammer to get the spindle to seat all the way through the bottom bracket, afterwhich the crank with Shimano XTR pedals barely made 2-revolutions. Even with the crank removed from the frame and a well greased spindle, I could not slide a bearing much more than the first 10 mm of the spindle. For that reason, I opted to remove/reinstall the bearings, then wet polished the spindle with two different grits of emery cloth until the spindle could be inserted by hand with moderate force, after which the crank with pedals spun more freely.
Michael - The Anaerobic Threshold is neither...

rayooo
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Joined: Mon Oct 14, 2019 11:57 am

by rayooo

My experience with bearings, BB and Wheel... as mentioned the grease and seals on new bearings provide the vast majority of the drag. I've gone so far as to compare several bearings by removing the seals and or removing grease (when new) and they all spin real easy. Re-installing the seals / grease and some are freeer spining than others due to the tighter fitting seals on some. (my assumption)
I don't feel the free-spin on newly installed bearings (assuming the install is correct, no miss-alignment etc) is a true indication of a quality bearing.

gtinut
Posts: 132
Joined: Wed Dec 30, 2015 4:04 pm

by gtinut

correct, new sealed bearing are little harder to spin .

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