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Home < News < News item |
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| WIDE OPEN TECH TIPS - BB INSTALLATION |
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| A complete Gravity Light crankset ready for installation |
Bottom brackets cop a fair amount of abuse so we have some tips to fit your new BB or freshen up your current one, that will help it survive the winter and extend its lifespan!
This article covers mostly FSA megaexo alloy cranksets but many of the tips will cross over to other models and brands, the only thing that generally changes is the way the LH arm fits to the spindle.
Important things to consider-
**The threads of a bottom bracket have a large surface area so any friction caused by bad threads will mean the cups won"t torque up properly. This will lead to creaking, cups that unwind, increased bearing wear and possibly loose crank arms. Damage to the frame and cup threads, as well as the indentations for the tool are almost certain to occur as well. To prevent this make sure the frame is properly chased & faced. Take note of the exact width of the frame BB shell also, it should be within 0.5mm of the nominal width. If not, you will need to add or replace a 1mm spacer instead of the usual 2.5mm to make up the difference.
**Water is the main culprit of bearing failure, if water is allowed to enter a regular chrome steel bearing, it will corrode rapidly and the bearing will be ruined. Stainless steel and ceramic bearings are much more resistant to corrosion but if left long enough without proper attention, they will eventually corrode as well. Therefore a good quality waterproof grease is essential, we use Mobil XHP 222 here for high water resistance but Juice Lubes Bearing Juice, Phil Wood and Exus "Yellow" grease are other good options. FSA has revised all of their BB cups to be easily serviceable.
**Torque settings are noted on all the bolts and BB cups, although these figures only apply if you take the time to properly prep and lubricate all threads. In any case, use your own judgement as to how tight the bolt needs to be, no bolt should need to be swung on! |
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| Chase the threads and face the bottom bracket shell, this will ensure the cups can tighten down smoothly and then snug up square against the frame. Then measure the width – 68, 70(Italian), 73 or 83mm wide. |
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| It is a good idea to prep the cups before installation, not because the factory grease isn’t good, but it is bad practise to mix greases so rebuilding the bearings with your grease now will make servicing easier later on. Pry off the bearing cover |
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| Wipe off the grease then carefully remove the dust seals from the bearings |
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| Flush the old grease out with WD40 or similar then leave to dry. |
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| Once they are dry, pack grease over through bearings and rotate to distribute the grease. Spread some more around the bearing so when the seal is replaced it will push grease through. The more grease that is in there, the less space for water to sit. |
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| Replace the seal and smear a thin layer of grease over the bearing as an added barrier against water, then clip the bearing cover back on |
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| See that gap behind the bearing? The blue seal minimises water incursion but once water reaches that point, it will sit there and has no way out. Pack it with grease again so water has nowhere to go. |
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| Packing more grease behind the bearing |
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| Scrape off the green threadlocker from the threads and grease both the cups and frame thoroughly. For 68mm MTB, you need 2 driveside spacers and 1 non-drive. 73mm is 1 on driveside only, 83mm shells take one on each side and road 68mm none. |
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| The cups should thread all the way home easily by hand, noting that the drive side cup is a LH hand thread (tightens anti-clockwise). If the cups are tight to turn, START AGAIN and clean up the threads or you will wreck your expensive frame and/or BB. |
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| Tighten them down with the appropriate tool. |
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| Lightly grease the crank spindle or inner bearing surface and carefully slide it through from the drive side. |
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| Grease the splines of the spindle and inside the LH crankarm then slide the crank on. |
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| Grease the crank preload bolt, and then tighten it down just enough to nip up the crank and remove any play. |
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| Grease the pinch bolts then tighten them down ¼ turn at a time, starting with the inside bolt as in the picture. |
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| The cranks should now spin freely with no side-to-side play, then with the rest of the drivetrain bolted on, the crankset should run trouble-free from now on! |
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