Press fit BB question
02-07-21, 01:32 PM
#1
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Press fit BB question
When installing bearings in a PF30 BB shell what should the tolerance be, ie, press fit that requires a bearing press tool, slip fit where the bearings simply slide into the shell, or something in between that requires a light tap with a hammer and dowel to install? Which is correct for the application? Assume an aluminum, steel, or titanium frame.
02-07-21, 02:13 PM
#2
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definitely press fit in this case. I don't think it's a good design, but I have never messed with one
02-07-21, 04:50 PM
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I know the carbon shells it is a slip fit with Locktite applied, however with metal shell it seems a press fit is the way to do it. I ask because a friend spent a wad of money on a custom ti frame made in North America and the bearings simply slipped into the shell. Just seems this will cause and issue down the road with nothing to hold the bearings securely in place.
02-07-21, 04:52 PM
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Pretty much all the non threaded/cupped cartridge bearings I have installed are a slight interference fit. By what number of thousandths on an inch an interference fit I can't say. I do know that this is discussed in bearing company websites. I also know that some bearings are speced for a certain amount of interference, as this can effect the installed preload. Andy
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02-26-21, 12:55 AM
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I am not a frame expert, but have recently been working on converting a PF30 BB to my Shimano 24mm crank, so this thread caught my eye.
I think there's a solution for what you're concerned about if I'm understanding it - that the cups don't have a solid interference fit when pressed into the PF30 shell.
Wheels Manufacturing, Enduro (Torqtite) and Praxis (and some others?) make threaded bottom brackets that fit into PF30 and other press fit shells, but the two cups are connected by a threaded sleeve inside the BB shell, making the fit solid. They make a bunch of conversions with in-board and outboard bearings (like I'm using) to convert PF30 shells to to other spindles. In some cases one side has to be pressed in and the other threads into it inside the shell. Some say neither side is pressed-in, some say it is OK either way.
But aside from these conversions, they also make threaded inboard PF30 bearings that connect this way. It seems both companies that I mentioned with this sort of threaded BB for press fit shells have pretty much nothing but good reviews that I've seen. Worth checking out on their websites and YouTube. Of course regular and expensive bearing versions of all of this stuff.
I think there's a solution for what you're concerned about if I'm understanding it - that the cups don't have a solid interference fit when pressed into the PF30 shell.
Wheels Manufacturing, Enduro (Torqtite) and Praxis (and some others?) make threaded bottom brackets that fit into PF30 and other press fit shells, but the two cups are connected by a threaded sleeve inside the BB shell, making the fit solid. They make a bunch of conversions with in-board and outboard bearings (like I'm using) to convert PF30 shells to to other spindles. In some cases one side has to be pressed in and the other threads into it inside the shell. Some say neither side is pressed-in, some say it is OK either way.
But aside from these conversions, they also make threaded inboard PF30 bearings that connect this way. It seems both companies that I mentioned with this sort of threaded BB for press fit shells have pretty much nothing but good reviews that I've seen. Worth checking out on their websites and YouTube. Of course regular and expensive bearing versions of all of this stuff.
Last edited by Camilo; 02-26-21 at 01:08 AM.
02-26-21, 02:32 AM
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I am not a frame expert, but have recently been working on converting a PF30 BB to my Shimano 24mm crank, so this thread caught my eye.
I think there's a solution for what you're concerned about if I'm understanding it - that the cups don't have a solid interference fit when pressed into the PF30 shell.
Wheels Manufacturing, Enduro (Torqtite) and Praxis (and some others?) make threaded bottom brackets that fit into PF30 and other press fit shells, but the two cups are connected by a threaded sleeve inside the BB shell, making the fit solid. They make a bunch of conversions with in-board and outboard bearings (like I'm using) to convert PF30 shells to to other spindles. In some cases one side has to be pressed in and the other threads into it inside the shell. Some say neither side is pressed-in, some say it is OK either way.
But aside from these conversions, they also make threaded inboard PF30 bearings that connect this way. It seems both companies that I mentioned with this sort of threaded BB for press fit shells have pretty much nothing but good reviews that I've seen. Worth checking out on their websites and YouTube. Of course regular and expensive bearing versions of all of this stuff.
I think there's a solution for what you're concerned about if I'm understanding it - that the cups don't have a solid interference fit when pressed into the PF30 shell.
Wheels Manufacturing, Enduro (Torqtite) and Praxis (and some others?) make threaded bottom brackets that fit into PF30 and other press fit shells, but the two cups are connected by a threaded sleeve inside the BB shell, making the fit solid. They make a bunch of conversions with in-board and outboard bearings (like I'm using) to convert PF30 shells to to other spindles. In some cases one side has to be pressed in and the other threads into it inside the shell. Some say neither side is pressed-in, some say it is OK either way.
But aside from these conversions, they also make threaded inboard PF30 bearings that connect this way. It seems both companies that I mentioned with this sort of threaded BB for press fit shells have pretty much nothing but good reviews that I've seen. Worth checking out on their websites and YouTube. Of course regular and expensive bearing versions of all of this stuff.
If they're a loose fit I would use a bit of loctite. I don't know how much of a pain that would make getting them out again though.
02-26-21, 03:20 AM
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If you use one of those it will stop them slopping in and out but are you sure they won't still move up and down, and around, and even spin the bearings? You're relying on friction on the inside face to hold them still against the force of pedalling.
If they're a loose fit I would use a bit of loctite. I don't know how much of a pain that would make getting them out again though.
If they're a loose fit I would use a bit of loctite. I don't know how much of a pain that would make getting them out again though.
The Praxis version has an a collett that expands inside the shell when the two sides are tightened together. - again from their descriptions and reviews- which makes the installation even tighter.
But the other versions have equally positive reviews so the design evidently works.
I plan to install a Praxis on my wife's bike this winter but won't know how it works til late spring.
Last edited by Camilo; 02-27-21 at 02:32 AM.
03-05-21, 11:28 PM
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I just finished installing the Praxis BB/PF 30 - Hollowtech II threaded conversion bottom bracket. It does not call for locktite anywhere, fwiw, just grease in some places and anti-seize in others.
The installation is very straight forward. After applying grease and anti-seize where the instructions say to, you press in the non drive side and thread in the drive side. The press fit part is actually pretty good for a DIY'er like myself who doesn't own a bottom bracket press, but is using a homemade version made from stout washers and threaded rod. That side can be manually pushed in quite a way, so only the last few (maybe 3-4) cm has to be pressed in. So it's very solidly aligned at that point, making the homemade press easy to use (my experience with homemade headset press was that I had to be very careful keeping the cups aligned while getting started). Then it's just a matter of threading in the other side. Instead of a torque spec, the threading gives you a hard stop (which requires some good force). Inside the BB, the collett is expanding making the whole thing very solid. The installation of the crank went normally and everything seems very solid and well functioning. I really don't expect any creaking or problems based on how it looks and feels to me at this point, and based on the reviews I've read of this product.
On the other hand, I greatly prefer simple threaded BB's. This frame isn't a big deal but I will try my hardest to buy threaded frames in the future.
The installation is very straight forward. After applying grease and anti-seize where the instructions say to, you press in the non drive side and thread in the drive side. The press fit part is actually pretty good for a DIY'er like myself who doesn't own a bottom bracket press, but is using a homemade version made from stout washers and threaded rod. That side can be manually pushed in quite a way, so only the last few (maybe 3-4) cm has to be pressed in. So it's very solidly aligned at that point, making the homemade press easy to use (my experience with homemade headset press was that I had to be very careful keeping the cups aligned while getting started). Then it's just a matter of threading in the other side. Instead of a torque spec, the threading gives you a hard stop (which requires some good force). Inside the BB, the collett is expanding making the whole thing very solid. The installation of the crank went normally and everything seems very solid and well functioning. I really don't expect any creaking or problems based on how it looks and feels to me at this point, and based on the reviews I've read of this product.
On the other hand, I greatly prefer simple threaded BB's. This frame isn't a big deal but I will try my hardest to buy threaded frames in the future.
Last edited by Camilo; 03-06-21 at 09:32 PM.
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