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  1. #1
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    Cartridge BB not as "free" spinning as cup BB?

    I've replaced and worn out cup bearing bb on a 25yr old steel bike refurb project with a cartridge IRD Quad QB-55, 68-118 -matched spec to old BB. Not installed it spins pretty smoothly, installed at 25ft/lbs torque it still spins smoothly but with more resistance than I expected and generally not a "freely" as a cup BB would, even before install. Is this typical? I lack the experience to really judge and I'm a big boy 225lbs, so don't want to hurt my baby.

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    Senior Member MudPie's Avatar
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    Yup, been my experience too with an ISIS cartridge BB. Spins smooth (little "grease" resistance) out of the box, but when installed, it was noticeably stiffer (although smooth). Drove me crazy. I recall trying different tightening schemes, like tighten the drive side a little, then non-drive -side and alternating. I don't recall exactly what I did, but do remember it wasn't as bad as it was, but definitely not a free spinning system. I somehow concluded the the bottom bracket threading might've been a little off and that caused tweaking of the bottom bracket (poor frame prep. This is a just a guess and it also could've been a stackup of tolerances with the bottom bracket and frame prep. I also used different brands (Truvativ and Suntour) and found one better than the other. Basically, I did my best and hadn't thought about it in three years, until I read your post.

    I am refurbing a 1987 Schwinn Super Sport steely and want to keep the BB as cup & cone - there's a certain art to getting the bearing adjustment just right and a great feeling when you get it right.

    BTW, I have external bearing bottom bracket on another bike and it is a smooth spinning system.

  3. #3
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    I believe that is consistent with what others have found. Now, extrapolating from free spin to resistance under load/weight involves an assumption; so how significant that is in real world cycling would need more/better measurement.

    KeS

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    Senior Member Cassave's Avatar
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    Here's my experience;

    Installed a Campy Chorus cartridge BB in a properly prepped frame.
    Installing only the fixed cup/bearing and spindle (torqued to Campy spec) caused the spindle to become very tight, as in many many inch pounds of torque required to turn it.
    The cups on that BB are aluminum. Torquing the cup applied enough radial compression on the bearings to remove all internal radial clearance, causing the bind.
    Remember, this was with no axial load since the adjustable cup was still sitting on the bench.
    I removed everything, reinstalled the fixed cup only (no bearings or spindle) and used a bore mike to measure the cup ID. It had compressed over .0023" from it's free condition. The cup ID was over .0015" LESS than the bearing OD.

    Ended up honing the cup bores out to provide .0002" interference at spec'd torque (50 nm I seem to recall) which results in a very free spinning system although seal drag on the bearings is still there so
    with no crankset installed it still doesn't feel like a good cup and cone design.

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    It's typical for a sealed cartridge BB to spin with more resistance than a properly adjusted cup and cone BB. Before installation, it feels to me as though the spindle is spinning through chocolate pudding as opposed to, let's say, skim milk. But the difference once installed and under load is so small that I can't feel it. I doubt it makes any difference in performance unless you're racing, and even then it might not. As long as your BB is spinning smoothly and without a lot of resistance, you'll be fine. If it's binding, as Cassave's Campy BB was, that would be a different matter, of course. You should be able to tell the difference. If in doubt, check with a knowledgeable friend or your LBS.
    Last edited by strock; 09-19-11 at 05:53 PM.
    Steve

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    chocolate pudding v. skim milk is a perfect analogy strock. The difference is pretty subtle, and I'm testing with my fingers, with no crank set. The frame threads looked pretty good after wire brushing and a dry fit to clear old paint. Sounds like a fairly typical observation based on the replies here, so I think I'm good.

  7. #7
    Old fart JohnDThompson's Avatar
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    The seals on cartridge bearings add some drag that is apparent when the bearing is unloaded. Under load, you would be hard pressed to measure, let alone detect any difference.

  8. #8
    Senior Member gyozadude's Avatar
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    I haven't replaced BB cartridge bearings in a while, but I put in an order for some more expensive replacement bearings recently since I'm down to my last set, and while the ID and OD match the same specs, the inner seal width was smaller. And what I found was the newer bearings appear to fit a couple more smaller, but higher quality balls into the same bearing and this increases the contact and keeps the bear aligned in the machined groove of the outer race a little better. Under side load, the newer bearing seems lighter and spins much more easily than under side load of the NOS one with fewer, but bigger balls. So while I think in general, cartridge bearings always have a bit more low-end drag, even amongst cartridges, there are better choices that are more durable and higher performance where side load might apply.
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  9. #9
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    Quote Originally Posted by Cassave View Post
    Here's my experience;

    Installed a Campy Chorus cartridge BB in a properly prepped frame.
    Installing only the fixed cup/bearing and spindle (torqued to Campy spec) caused the spindle to become very tight, as in many many inch pounds of torque required to turn it.
    The cups on that BB are aluminum. Torquing the cup applied enough radial compression on the bearings to remove all internal radial clearance, causing the bind.
    Remember, this was with no axial load since the adjustable cup was still sitting on the bench.
    I removed everything, reinstalled the fixed cup only (no bearings or spindle) and used a bore mike to measure the cup ID. It had compressed over .0023" from it's free condition. The cup ID was over .0015" LESS than the bearing OD.

    Ended up honing the cup bores out to provide .0002" interference at spec'd torque (50 nm I seem to recall) which results in a very free spinning system although seal drag on the bearings is still there so
    with no crankset installed it still doesn't feel like a good cup and cone design.
    interesting. so, was the problem the chorus bb...or your bb shell? if the shell, wouldnt just facing/chasing solve this problem?

  10. #10
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    Quote Originally Posted by bionnaki View Post
    interesting. so, was the problem the chorus bb...or your bb shell? if the shell, wouldnt just facing/chasing solve this problem?
    The poster said the frame was "properly prepped" so it is likely the frame was faced and the threads chased prior to the bb installation. Also the cup's ID was measured with it out of the frame so the bb shell's dimensions weren't a factor.

    To the OP: Old, good quality properly adjusted cup-and-cone bb's can be very smooth as whatever seals they came with are now quite worn. Barring misalignment, cartridge bb's normally have a bit of drag due to new seals and more grease resistance. They will loosen up a bit with mileage and, as noted, the drag is insignificant in the real world.

  11. #11
    Senior Member Cassave's Avatar
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    The problem is with the very thin walled aluminum BB cup. The crankshell was tapped and faced perfectly.
    Tightening any threaded fastener induces radial loads (hoop stress). In this case I think the design didn't allow enough clearance in the free state to prevent overloading the bearing outer races at the installation torque.

  12. #12
    Senior Member BCRider's Avatar
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    WIth the cartridge BB you'll find that after a few hundred miles that the excess grease seems to migrate out of the way and the BB spins a lot more easily. Or it may also be due to the bearings pushing more finely into alignment. All I know is that after some amount of use my cartridge BB's all seem to spin more freely when I kick the cranks back to position them for mounting up. So at some point the "choclate pudding" feel will change to more like a "light cream" feel. But due to the seals running and thickness of the grease if you get to where it's truly got a "skim milk" feel like you can get on a finely tuned C&C BB then it's likely on the brink of disaster.
    Model airplanes are cool too!.....

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