I pulled my chain off my cannondale road bike for cleaning today, and i noticed there was quite a bit of resistance on my Truvativ Crank And GXP BB, if i spun the cranks they'd only spin about 2 or 3 revolutions before stopping.

Since the bike didn't have wheels or chain i just popped into my LBS and the mechanic there said this was completely normal. Many of today's External BB's are packed and sealed pretty well, with pretty thick grease so that they last a long time. This seems to make perfect sense.

He also explained that once you get a chain on there and actually start biking, that you probably won't really notice the difference between it and, a really oiled up BB, only difference is the one with thick grease will last longer.

I haven't taken the chain off my other cannnodale which has the hollowgram BB to compare, but i'm kind of tempted to do a side by side comparison. I can remember last year cleaning the chain on my Trek 5000, and i would spin the cranks with no chain on the bike and they would spin for a good minute or two and slowly come to a hault.

Is this really normal these days to have really thickly greased BB bearings? Would one of those new ceramic bearing BB's be better? Is it conceivable to use a thinner grease/oil and just plan on servicing your BB bearings once a month instead of once or twice a year?

I doubt it's a problem, so long as the BB axle turns smoothly without "bumpy" resistance. Often, these things get smoother over time anyway.

Yes.
Yes, with an if.
No, with a but.

Enjoy

It is pretty smooth, continuous resistance, pretty free of bump's as i can tell. I kinda figured the same, it would jsut kind of losen up over time thru the season.



if..... what? i had the money?
but... what? i'd need the time to do it every month?

This is my third thread on this topic. It is getting to the point where I think I'm going to start sourcing replacement bearings for these guys that give everyone the feel that they are looking for.

Your wrench was correct. The bearings that the manufacturers are putting in these are ones that are readily available in these sizes. The bearings have not been designed around this particular application, instead they are designed (for the most part) with motor, pump service in mnd. The contact seals, and higher viscosity grease increase the drag/friction felt at the lower end.

Phil Wood has been marketing a replacement bearing for these cup which is actually a NTN manufactured 6805LLU (25mmx37mmx7mm w/contact seals). That bearing has a limiting speed of 18,000 rpm in appliction with grease. Assuming a design factor you'd still be a shade over 4,000 rpm for continuous use. Most (if not all) cyclists would never get close to 200 rpm let alone 4,000.

Needless to say the grease in these is designed around that approximate operating speed to ensure longevity and reduce thermal breakdown. This translates into higher frictional forces (drag) at low speed applications (cycling).

I also noticed that while NTN makes a low-torque-sealed version in this series of bearings, it is not available in this size, which is why we're probably stuck with what they've been putting in.

FSA has come out with a version of cups that have ceramic hybrid bearings in them for this year to address this drag issue. They are selling them for a lot of money.

I am sure someone on here can find a good source for ceramic hybrid deep-groove bearings designed for low torque/low friction application with adequate sealing...if someone can get a good price, I'll fire up the arbor press and we'll all go into business

My shimano bearings are "cycling specific" and have the same drag. Big fatty bearings have more contact area with more grease to stick to the races. It's less about the viscosity and more about the enormous size of the bearings (relative to normal BB bearings).

Phil bearings feel the same in there, as do ceramics, and you'll never tell a difference when actually pedaling which has been verified through wattage meters.

If you want a "cheap" source of odd ceramic bearings, check out VBX on Ebay.

There's so much bull**** about bearings floating around, how your bearings act under no load and how they act under load are two very different things. And that's why my BMX with its half ton bearing hubs can drop roadies down hills.

Yeah since the dropping has almost nothing to do with bearings.

Hey Derek, do you use Cyclesmith on Woodlawn? I've had very mixed reviews there, I do my own work so I'm not familiar with the mechanics. The counter staff hasn't really impressed me much, although there are a few good ones in my opinion. Most of the bits I get from MEC, good stuff and a lot cheaper.

Chilly

Will anyone really notice a "difference" under normal operating conditions. No.

Is what you were experiencing normal WRT other BBs of the same type. Yes.

Can a mechanical system be operated using less energy if friction is removed from the system. Yes.

Is the fact that many garage mechanics have noticed the increased drag present in these bearings going to end up with many companies offering "Low-Friction", "Less-Drag", "Free-Rotation", "Ceramic-Speed" branded versions of the same BB? You bet.

The fact that companies like Phil Wood and FSA are currently offering options tells you that it's more than just bs...at least as far as the marketing power of this issue goes.

You can take that one to the bank.

So what is it then?

It is more the friction associated in sealing these bearings as oposed to open repackable style bearings of the past. With the advent of off road use the idea of a sealed bearing that you dident need to do semianual maintanance on has become the norm, and it is these rubber seals that have upped the stickshun levels.

Very astute observation. Perception is reality.

I'd like to see the data verifying thru wattage meters with different BB bearings. Please don't show me powertap data though. Give me a data set that only test's the rolling resistance of the bearings in the BB.

I'll admit that it's not under load, but, i could disernably tell that it took more force to move the pedals one revolution then it did on my last bike that used internal shimano bearings that were very "spinny". Perhaps it's the different bearing size, perhaps it's the bearing construction, perhaps it's the grease, or perhaps it's just the age of the bearings on my old bike compared to the bearings on my new bike.

I used to play around with bearings quite a bit in my skateboarding day, playing around with different oils, and grease's to find just the right combination that would make my board roll a long as possible but also a smooth and quiet as possible, i often found that working in some general green bearing grease followed by just the right touch of vaseline oil worked just right, but it was a drop by drop process to get the right mix in the bearing.

I guess i just wished my cranks spun as nicely as my wheels do


Yup. The floor guys are a little goofy, but it helps if you know them lol. Their head mechanic scotty know's his stuff though. Their the shop i took my bike to after a car accident and the owner helped me thru the whole insurance claim process so that's where i tend to go now, and i also baught the r1000 with the BB in question from there too. I used to shop at MEC a bit, i still do for simple things like water bottles or glove's sometimes their just so much cheaper, i still get frown's though from the guys at the shop But most of the time Cyclesmith is just more convienent for me then driving all the way over the halifax to save 5$ on a part.
ps, ride roadie much? there's a 'swift' wedn night ride that meet's at 6pm at Tim's bottom of montobello dr in drtm.

your BB sounds like crap. no mattah what, it is sucking watts from you
that could be used for forward motion. load or no load, those buggers should
spin way fast by hand and take over 10 seconds to stop. any less, then find
a new BB.

unless you don't care.

I've used high end and low end and hand packed and factory sealed bearing BB's
and -all of them- feel so loose and fast you have to stop and yank on them to
prove they have no side-side play. they are just so smooth and spin freely with
zero play. all forward motion, and impervious to rain and mud. for years.

so...again...your BB sounds like junk to me IMHO

I was hoping someone would catch that.

+1 - Exactly. Almost makes me want to pop mine open and remove the contact seals...almost.

You can talk about sticktion all you want, it means **** in the real world. I've ridden bikes where the bearing size was correctly calculate for dynamic load, life etc, and I've ridden bikes where the bearing size is calculated by "that looks like it'll fit". And the one that was correctly calculated rolled noticably further than the other, and it was also a lot more difficult to turn by hand. Presumably due to the amount of grease, increase in seal contact area etc.
An incorrectly specified bearing will either be too big for the job, thus having too much friction, or too small causing greatly increaed wear and reduced life, also increasing friction.

I'm not convinced any of this really matters that much for BB bearings.

It probably doesn't. Still, I miss the days of narrower spindles, where you could spin a crank (with the chain removed, and bike upside-down or in a stand) and the crank would spin for a minute. Actually, I'm still in those days. Someday I'll probably get an integrated BB crank. But that's awhile off...

The loose ball BB in my Raleigh spins like that.

The sealed Campy BB's in my other road bikes will actually rock back and forth like a pendulum when you give them a nudge while one pedal is off. I was nearly hypnotized by this the last time I did some pedal maintenance.

There's a couple of bearing companies in the buisness park, maybe i'll head over there and just ask a couple of questions, though i'm sure they won't have the slightest clue what to recommend for BB bearings.

We've had better luck with Kinecor than Canadian Bearings, at least lately, if you're going to Burnside. If you knew which manufacturer made the bearing you want, they should be able to get it for you, and probably a good deal cheaper. In fact, if you have the inner and outer dimensions and width, they can match up pretty much whatever you want. One point of caution, beware of any unusual suffixes attached to the bearing numbers, they usually mean the bearing is rated for some particular use. I found that with chainsaw crank bearings, for example. SKF has a great customer service/tech support service hotline, I've used them in the past with good success.

I don't think I'm up to the stresses and strains of roadie life just yet.. the ol' beast is still hanging in the basement, in fact. I'm thinking of digging it out tonight for the first flight of 06.

Those of you that have a tendency to call something **** instead of learning what it really is and how it affects you in the real world are excused.

For the rest, it is seal friction plus ball bearings or roller bearings in grease friction that keeps your new high end BB from allowing your crank arms to rotate endlessly like some wana-be perpetual motion machine. Stickshun or sticktion is a threshold force, which once overcome by rotation, is only even relevant in the rubber seals ongoing attempts to regain adhesion. This ever so small resistance is only noticeable at very low rpm and NO load. Once you turn the bike over and put the wheels on the ground there are dozens of significantly greater forces that so overwhelm the tiny force that it becomes insignificant.

There are many things that are there and measurable but unless you know about scale of relevance you can be deceived into wrong thinking. For example led is bad if ingested. That is a true statement. There are trace amounts of led in the water you drink, is also a true statement. But it is unreasonable to automatically jump to the conclusion that the water you drink is bad for you, unless you know two things. How much led is in the water and at what level does led in water begin to affect us.

*claps*

I'm sorry, but I don't want lead in my water.