Ask the Expert: James Huang on Bottom Brackets

BR_Gregor

Hi guys, as mentioned last week, in this thread James Huang/Angry Asian (@angryasian) will be answering your questions. Please ask him anything you like about – his chosen topic – bottom brackets.

You may have read his Angry Asian column previously on the main site, or some of his reviews on gear or bikes, or seen his galleries of pictures from the best bike shows around the world, and he'll now endeavour to answer your questions.

Should just mention that James is based in the US so he may take a little while to reply, but don't worry: he will.

Cheers.

DKay

I'm currently using a plastic SRAM PF30 adapter on my Cayo Evo in order to run Shimano HT2 BBs and cranks. Are there any long-term issues using such plastic adapters or would I be better off switching to a solution such as the Praxis Works PF30 BB?

On a related note, I went to replace the HT2 BB a few weeks ago, but the plastic adapter just spun in the shell of the frame when I applied torque to the body of the BB. Any ideas on the best way to go about removing it?

jimwalsh

Should I always get a frame faced and chased before fitting a bottom bracket?

angryasian

That's funny; I just worked on a friend's Cayo with exactly that setup just a few days ago.

I'm generally not a fan of just tacking on extra pieces to make odd combinations of cranks and bottom brackets fit with each other. There's an inevitable stacking-up of tolerances, and more interfaces that can possibly creak. If you're already planning on replacing the bottom bracket anyway, I would absolutely go with the Praxis conversion BB. It's the only one that uses an expanding collet design that braces itself against the inside the shell, and the bearings and seals are very good quality. I've never had one creak on me, and have yet to hear a complaint from anyone else who has used one.

Removing the original one is pretty easy to do but there are a few extra steps involved.

Focus assembles those bottom brackets by first threading the Shimano cups into the plastic adapters (which have wrench flats so that the two parts can be screwed together tightly), and then pressing those sub-assemblies into the frame. To remove them, you first need to knock the plastic adapters (with cups still attached) out with something like this: http://www.parktool.com/product/head-cup-remover-rt-1. Once those subassemblies are out, you can then separate the individual parts.

angryasian

jimwalsh:

Sounds like you're talking about a threaded shell? It depends on the frame, to be honest. If the cups thread in smoothly and you generally haven't had any issues with premature bearing durability, you're probably ok.

That said, if it's a frame that you intend to have for a long time and that process has never been done, it's certainly not a bad idea as it guarantees a proper interface (and therefore, proper bearing alignment) for the bottom bracket cups. Some of this depends on what type of bottom bracket you're putting in there, too. If it's an external-type system where the cups both locate against the face of the BB shell, or an old-school adjustable cup-and-cone setup, it's very important that those faces be parallel.

But if you're using an older-style Shimano cartridge-type unit (like a square taper or original Hollowtech splined system), it's not quite as critical.

ugo.santalucia

If HT2 is stiffer than a square taper and press fit are stiffer than HT2, why many track cyclists in Keirin use square taper?

BR_Gregor

I bow to James' knowledge here: I recently got a new bike and the crank takes a real good push to get it to rotate. Once pushed, shouldn't the cranks rotate pretty freely for a bit? Mine rotates once maximum. 360 degrees. Nothing more, just slows down real quick. Is this down to poor bearings? Poor bottom bracket? Will it free up?

DKay

angryasian wrote:

That's funny; I just worked on a friend's Cayo with exactly that setup just a few days ago.....

Cheers for the comprehensive reply James. Looks like a Praxis works BB will be on order soon.

ugo.santalucia

BR_Gregor wrote:

I bow to James' knowledge here: I recently got a new bike and the crank takes a real good push to get it to rotate. Once pushed, shouldn't the cranks rotate pretty freely for a bit? Mine rotates once maximum. 360 degrees. Nothing more, just slows down real quick. Is this down to poor bearings? Poor bottom bracket? Will it free up?

probably good bearings with tight seals

BR_Gregor

Cheers Ugo!

ror3h

I have a Scott with a shimano press fit (BB86) bottom bracket, and I've had a recurring clicking or creaking coming from the BB. What's the best way to silence this? I know there are plenty of solutions for PF30 frames (such as praxis works etc), but are there any for BB86? I've also read that applying some loctite 641 during installation may cure it, but is that a good idea with a carbon BB shell?

ExpatBiker

I'm running a first generation Saint hollow tech crankset and bottom bracket on a Santa Cruz VP free (2005 model)

Recently, it's developed a bit of click on every rotation? Any ideas?

brettjmcc

Can you advise the best way to install a Rotor 4130 (BB86 but for UBB30 axle) into a carbon shell frame such as a BMC GF01? I am thinking of just pressing in and using carbon paste, as the BB shells are metal

bishauckbiking

I ride a Scott SUB 35 as my commuting bike. It has an eccentric bottom bracket used to tension the chain as it has internal hub gears.

I find that over time the chain loses tension, no matter how tight I try to get the bottom bracket clamp bolts.

I looked at removing the BB and seeing if it was over-greased, but couldn't see how to remove it.

Any advice would be appreciated!

antfly

HI James, slightly tedious question but I have the park tool BBT 30.3 which I used sucessfully for removal and installation on a BB30 frame but I now have a PF30 frame. I see Park Tools say the 30.3 tool is for BB30 and PF30 but they now have a different tool just for PF30, the catchily titled BBT-90.3, with different size bushings for installation. So is it ok to use the old BB30 bushings for a PF30 BB installation,and which tool would you recommend for removal of a PF30 ?

Voenie2

ExpatBiker wrote:

I'm running a first generation Saint hollow tech crankset and bottom bracket on a Santa Cruz VP free (2005 model)

Recently, it's developed a bit of click on every rotation? Any ideas?

I had exactly the same problem with my first generation Hollowtech bottombracket/crankset!

Just yesterday I decided to solve the problem. I removed my pedals, removed my chainrings and removed the cranks. Cleaned everything very well, greased every thread and put it all back together. No more click now!

It often sounds like clicks and creaks are comming from the bottombracket, but mostly the source of the noise is a loose chainring bolt, the pedal or an untightend crank. A bit of grease on the splines can help too sometimes.

angryasian

ugo.santalucia wrote:

If HT2 is stiffer than a square taper and press fit are stiffer than HT2, why many track cyclists in Keirin use square taper?

I have little firsthand experience with track gear but I consulted with a few team mechanic buddies who do. Here's what came back:

"I posted your question to a mechanics forum online and the conversation has been very interesting. The general consensus is that reasoning lies in these two aspects:
1) The large number of 144 bolt pattern 1/8” chainrings the athletes already own and availability of the same in 130, 135 or 110 bolt patterns.

2) Simplicity of packing a bike using the older system. The new two-piece systems take up a lot more space. You can’t just throw a crank arm into a chainring bag if it has a spindle sticking out of it.


There are lots of speculation on what type of bearing system rolls better but no one has any data to prove otherwise…well, other than their personal spin the crank on the bike tests. Some prefer the feel of older greased bearings while others feel the new ceramic bearings offer something spectacular. However, no one has any real data in track use under track loads."

angryasian

BR_Gregor wrote:

I bow to James' knowledge here: I recently got a new bike and the crank takes a real good push to get it to rotate. Once pushed, shouldn't the cranks rotate pretty freely for a bit? Mine rotates once maximum. 360 degrees. Nothing more, just slows down real quick. Is this down to poor bearings? Poor bottom bracket? Will it free up?

First, let me provide some additional information here. Gregor is talking about a brand-new bike here (a Giant Defy with a Shimano crank and press-fit BB) and the cranks didn't yet have pedals installed when he did that spin test.

That said, my guess is that this will all break in over time. Giant frames generally have excellent dimensional tolerances at the bottom bracket. Shimano bottom brackets use rather heavy grease, however, and the seals are more weather resistant than most so especially when new, they usually don't spin very freely. But on the plus side, they last longer than most so it's a worthy tradeoff in my opinion.

angryasian

ror3h wrote:

I have a Scott with a shimano press fit (BB86) bottom bracket, and I've had a recurring clicking or creaking coming from the BB. What's the best way to silence this? I know there are plenty of solutions for PF30 frames (such as praxis works etc), but are there any for BB86? I've also read that applying some loctite 641 during installation may cure it, but is that a good idea with a carbon BB shell?

Using some sort of retaining compound usually does help, especially with carbon shells and plastic cups. You'll need to be sure to prep the surfaces very well, though, as otherwise you won't get a reliable bond.

That said, I'm not a huge fan of gluing bottom bracket cups into the shell. You're correct that Praxis doesn't current offer a thread-together bottom bracket for a PF86 shell but Enduro just released one: http://www.bikeradar.com/us/road/news/article/enduro-launches-torqtite-press-fit-bottom-brackets-43740/. I just installed a PF86 version into a frame the other day and was pretty impressed with the quality of fit. Time will tell if it develops any creaks later but I'm encouraged right now.

angryasian

ExpatBiker wrote:

I'm running a first generation Saint hollow tech crankset and bottom bracket on a Santa Cruz VP free (2005 model)

Recently, it's developed a bit of click on every rotation? Any ideas?

As a general rule, creaking is a telltale sign that something is moving very slightly under load. Even though your frame has a threaded shell, there's still some room for the cups to wiggle around. I'd pull those cups out, wrap the threads in two rounds of PTFE plumbing tape, grease everything up, and reinstall to the recommended torque. The PTFE tape helps to fill in the space so it doesn't creak, and the grease prevents water from getting in. Be mindful of the direction in which you wrap that PTFE tape, too. You don't want it to unravel and bind up when you thread the cups in so you'll want to wind it in the opposite direction from how you thread them into the frame (which also means that each side will be different).

angryasian

brettjmcc wrote:

Can you advise the best way to install a Rotor 4130 (BB86 but for UBB30 axle) into a carbon shell frame such as a BMC GF01? I am thinking of just pressing in and using carbon paste, as the BB shells are metal

For metal-on-metal interfaces like that, I like to use a mild sleeve retaining compound such as Loctite 609. It cures quickly, lasts seemingly forever, prevents corrosion, and is still easy to remove if/when needed. You could certainly use friction paste (or grease) but it's unlikely to be a good long-term solution.

angryasian

bishauckbiking wrote:

I ride a Scott SUB 35 as my commuting bike. It has an eccentric bottom bracket used to tension the chain as it has internal hub gears.

I find that over time the chain loses tension, no matter how tight I try to get the bottom bracket clamp bolts.

I looked at removing the BB and seeing if it was over-greased, but couldn't see how to remove it.

Any advice would be appreciated!

I have a hard time thinking that your eccentric is moving but there are a few things you can do just in case. First, remove the eccentric from the shell, clean everything up, and apply some friction paste to both the inside of the shell and the outside of the eccentric. Second, remove the BB clamp bolts, clean the threads (on the bolts and frame) out as best as possible, and reinstall with blue Loctite. After you've got everything reinstalled, draw a small line across both the eccentric and BB shell with a permanent marker. If it's actually moving, you'll be able to see it.

I suspect, however, that it's not an issue of the eccentric rotating but rather the drivetrain just wearing. As the rollers and teeth wear, it'll give the appearance of the chain 'stretching'. You don't notice this on a bike with conventional derailleurs since any additional slack is just taken up by the spring-loaded pulley cage.

angryasian

antfly wrote:

HI James, slightly tedious question but I have the park tool BBT 30.3 which I used sucessfully for removal and installation on a BB30 frame but I now have a PF30 frame. I see Park Tools say the 30.3 tool is for BB30 and PF30 but they now have a different tool just for PF30, the catchily titled BBT-90.3, with different size bushings for installation. So is it ok to use the old BB30 bushings for a PF30 BB installation,and which tool would you recommend for removal of a PF30 ?

According to the Park web site, that BBT-90.3 tool you've referenced is "designed to remove and install the bearings and bearing units used in BB86, BB91, BB92, Shimano Press Fit, SRAM Press Fit GXP, Race Face Press Fit and other press fit bottom bracket systems using the nominal 24mm spindle", not 30mm ones.

You should be able to use the same guides for installation provided the bearing cartridge dimensions are identical (which they usually are). Just make sure that you're still pressing only on the outer bearing race and not on the seal.

As for removal, you *might* be able to use that same tool if it'll fit. Press-fit cups have more 'stuff' in the way so there might not be enough room. In those cases, I usually just end up using a Park headset cup remover (but I prefer to use something like this: http://www.enduroforkseals.com/id195.html).

antfly

Thanks James, I didn't notice it was for 24 mm, good thing I asked..

gaffer_slow

looking at replacing BB86 shimano BB.

Wondered what differences are between the Ultegra Level and the Dura Ace.

Priced about the same online, Dura Ace 21 grams lighter but frankly i don't care too much about that.

Which will be better from a durability / bearing quality angle / no creak etc?


SM-BB72-41B - €19
SM-BB91-41B - €25

which would you recommend - or doesn't it rly matter

thx

angryasian

gaffer_slow wrote:

looking at replacing BB86 shimano BB.

Wondered what differences are between the Ultegra Level and the Dura Ace.

Priced about the same online, Dura Ace 21 grams lighter but frankly i don't care too much about that.

Which will be better from a durability / bearing quality angle / no creak etc?


SM-BB72-41B - €19
SM-BB91-41B - €25

which would you recommend - or doesn't it rly matter

thx

If there's a significant functional difference, I've never noticed one. I would just go with the Ultegra one myself.

ska1903

Hi,

I currently have a 2014 Giant TCX SLR2 with FSA Omega 46/36 crankset and an FSA PressFit BB86 Bottom bracket and would like to upgrade the crankset to Shimano 105 to match the rest of the bike.

Can i use the current BB and just change the crankset or will i need to change the BB as well?

Thanks

brettjmcc

James, the thing is it is not metal to metal. The Rotor BB is metal, but the bottom bracket area is just a carbon shell.

Rotor suggest using 641 in their installation, but I thought this was for metal to metal installation, or would it work on metal/carbon fits too without potentially damaging resins in the frame? Thanks once again

angryasian wrote:

brettjmcc wrote:

Can you advise the best way to install a Rotor 4130 (BB86 but for UBB30 axle) into a carbon shell frame such as a BMC GF01? I am thinking of just pressing in and using carbon paste, as the BB shells are metal

For metal-on-metal interfaces like that, I like to use a mild sleeve retaining compound such as Loctite 609. It cures quickly, lasts seemingly forever, prevents corrosion, and is still easy to remove if/when needed. You could certainly use friction paste (or grease) but it's unlikely to be a good long-term solution.

gaffer_slow

ska1903 wrote:

Hi,

I currently have a 2014 Giant TCX SLR2 with FSA Omega 46/36 crankset and an FSA PressFit BB86 Bottom bracket and would like to upgrade the crankset to Shimano 105 to match the rest of the bike.

Can i use the current BB and just change the crankset or will i need to change the BB as well?

Thanks

You need a 24mm BB like

BR_Gregor

One question that was emailed to us from a BR reader with limited internet access this week (Eric Foster – this is for you):

"What kind of FSA cranks and bottom bracket do I need for a Kestrel Talon 105 Road Bike? I'm lost, please help me."

BR_Gregor

Also two questions from the promo posts that were asked on those threads and haven't been rolled over into this one:

1) 'Why the hell do manufacturers continue to fit press fit bottom brackets to mountain bikes? It's a stupid idea and no one wants them.'

2) 'Why do they continue to fit press fit bottom brackets to non-carbon bikes?'