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9 votes

Searching for a Pressfit BB replacement for my road bike

You've got a BB386 shell and Shimano road cranks, which are all 24mm. There are a lot of individual replacement bottom bracket models that could do what you need here. The expensive ones are often ...
Nathan Knutson's user avatar
9 votes

Why were press fit bottom brackets invented?

Carbon is the dominant frame material in performance bicycles. You can't thread carbon. There are two ways to get bottom bracket cups into a carbon frame: bond (industrial-strength glue) an alloy ...
Weiwen Ng's user avatar
  • 32.8k
9 votes
Accepted

Loose bottom bracket on MTB

It looks like your BB cartridge is no longer pressed into the frame shell. When you removed the cranks did it just sort of fall apart? That is a signal that for whatever reason the BB is worn so that ...
Warren Burton's user avatar
8 votes
Accepted

How to install press fit bottom bracket into new frame

Ideally you do it with a press type tool, one cup at a time, with stepped bushings that mate snugly with the cups and the BB shell. For the first cup, one of the bushings is interfaced with the frame ...
Nathan Knutson's user avatar
7 votes
Accepted

Is there empirical evidence that SRAM DUB bottom brackets have longevity issues in the BB86/92 format?

You're looking for empirical data and you probably will never get any unless you do the testing yourself. The problem is that the alignment and tolerances of the frame bores and to a lesser extent the ...
Nathan Knutson's user avatar
5 votes
Accepted

PF30 cup came out of frame, can it be pressed back in or should it be replaced?

Once you get the bearing and cup off the spindle, you can assess the state of the bearings a little. Turn them with your fingers while pushing hard in both the radial and lateral directions. This kind ...
Nathan Knutson's user avatar
5 votes

30mm bottom bracket and 30mm spindle axle compatibility, should it go in by force?

There is no difference in the fit expected based on road vs mountain. I thought I would be able to provide tolerance numbers from the original BB30 technical documents put out by Cannondale. They used ...
Nathan Knutson's user avatar
5 votes

Why is my XTR M9100 crank fouling the chainstay?

By comparing the two images from your google photos album where you measure the outside chainstay width, it seems very likely (to me) that the bottom bracket has a different offset in the white frame ...
Saaru Lindestøkke's user avatar
5 votes

What was the engineering motivation behind each press-fit bottom bracket standard?

All else equal and up to a point, larger ball bearings and more widely spaced bearings will be more durable. Juhist alludes to this in his answer. Keep in mind that diminishing returns-type ...
Weiwen Ng's user avatar
  • 32.8k
4 votes

Why were press fit bottom brackets invented?

The reason I have always heard justifying PF bearings vs outboard bearings is that PF bearings allow the frame to be wider and stiffer in the BB area without increasing the Q-factor of the bicycle. PF ...
Fred the Magic Wonder Dog's user avatar
4 votes

Why were press fit bottom brackets invented?

Money. Threading holes is a process that has to happen during manufacturing. Both sides have to be concentric and parallel, and the taps used to make the threads have to be pretty good, so they wear ...
Criggie's user avatar
  • 127k
4 votes
Accepted

Is it possible to convert a press fit bottom bracket to threaded?

BB30 and PF30 have press-in adapters available that have ISO aka BSA aka English threads. They do work but they mostly exist for the purpose of being able to run a certain crank that you wouldn't ...
Nathan Knutson's user avatar
4 votes
Accepted

Creaking pressfit bottom bracket

Many manufacturers tend to use them secondarily for stiffness and performance reasons and primarily because if you don't have it, it's probably harder to sell that bike these days. It's not a ...
Batman's user avatar
  • 46.3k
4 votes

Why is my XTR M9100 crank fouling the chainstay?

Given all the details and measurments, I think the only way to explain this is a small angle in the bb housing (either the shell, or the bb itself), but if you follow the calculations you will see I ...
EarlGrey's user avatar
  • 3,712
3 votes

Is this a pressfit bottom bracket?

They seem to be the same, or at least equivalent – note the RRP is the same for both. They will both work in a BB386 press-fit bottom bracket shell, but they are installed by threading (rather than ...
Will Vousden's user avatar
  • 4,001
3 votes

Searching for a Pressfit BB replacement for my road bike

I’m not able to locate a set of original specs that say what you reported. BSA means an English threaded bottom bracket. BB386 should mean a press fit BB, with diameter 46mm, and width 86.5mm, I.e. ...
Weiwen Ng's user avatar
  • 32.8k
3 votes

Converting Threaded BB Shell To Press Fit Shell

It is impossible to convert a threaded BB shell to one of the common press fit standards, e.g. PF30, BB86. I assume you have an English (aka BSA) threaded BB with a 33.6-33.9mm diameter. All the press ...
Weiwen Ng's user avatar
  • 32.8k
3 votes

Why is my XTR M9100 crank fouling the chainstay?

Without knowing anything about this specific company, it's plausible that what they supply their frame producer with is either a drawing that describes minimum clearances at various points relative to ...
Nathan Knutson's user avatar
3 votes

What was the engineering motivation behind each press-fit bottom bracket standard?

I think the idea is as follows. Long time ago, bottom bracket spindles were not hollow inside. This created a heavy design and the spindles were too weak anyway. Then, Shimano tried Octalink bottom ...
juhist's user avatar
  • 19.8k
2 votes

What is the difference between Shimano BB71 and BB72 bottom brackets?

From the very amazon.co.uk page you quoted: Hi, what is the difference between these 2 bottom brackets.i have a sm-bb7141 bottom bracket on my giant tcr composite 1 2013,not which 1 to buy ...
Grigory Rechistov's user avatar
2 votes

30mm bottom bracket and 30mm spindle axle compatibility, should it go in by force?

The fit off the axle in the bearings needs to have no play between the race and axle. The axles are designed to be tighter than a 'slip' fit, but not a full 'interference' fit. This means the axle ...
Argenti Apparatus's user avatar
2 votes
Accepted

Adapter for a Shimano 7000 Crankset to BB30 Pressfit

Whoever wrote their product specs was probably confused, because "BB86.5" isn't really a thing. You have an FSA 386EVO crank. All the bikes in this series seem to have come with them. You ...
Nathan Knutson's user avatar
2 votes

PF30 cup came out of frame, can it be pressed back in or should it be replaced?

Elaborating a bit on Nathan's answer, I believe that while the nominal specification for PF30 bottom bracket shells is a 46mm internal diameter, the actual engineering specification is likely to fall ...
Weiwen Ng's user avatar
  • 32.8k
2 votes

Converting Threaded BB Shell To Press Fit Shell

There have been various pressfit shell standards (Singer, Klein, Fisher, others) that are dimensioned similiar to an ISO shell and where convesion might be possible in some sense, but they all involve ...
Nathan Knutson's user avatar
2 votes

TorqTite BB for press fit creak?

While product recommendations are off-topic here, there's a case to be made for sticking with the same manufacturer in a case like this where you can just also get the Rotor screw-together PF30 BB ...
Nathan Knutson's user avatar
2 votes

Is this a pressfit bottom bracket?

You would read a BB spec by looking for a shell type, e.g. BB 386, and then a spindle type, e.g. Shimano. Spindles differ in diameter, so the BBs have to be different or to use a reducer kit (e.g. I ...
Weiwen Ng's user avatar
  • 32.8k
2 votes

Is this a pressfit bottom bracket?

Bear in mind that the web listings may have incorrect photos and incorrect details. Don't trust the photos implicitly, you should contact the seller before purchase if you have any doubts. They will ...
Swifty's user avatar
  • 12.8k
2 votes

Is there empirical evidence that SRAM DUB bottom brackets have longevity issues in the BB86/92 format?

Empirical typically means derived from experiment or other structured data collection, as contrasted to theoretical or to anecdotal. SRAM themselves might have warranty data that apply - however, that ...
Weiwen Ng's user avatar
  • 32.8k
1 vote

BB86 Bottom Bracket too long?

I am not able to find a formal technical diagram of the BB86 shell. Thus, what follows is speculation. It does seem like the official specs from Shimano call for a lip/step. This page by Lightning ...
Weiwen Ng's user avatar
  • 32.8k
1 vote

Which Bottom Bracket do i need? 107mm 41

One first piece of advice to cyclists would be to Google your bike's model name and the phrase "bottom bracket". This will often show results containing the specification. However, in this ...
Weiwen Ng's user avatar
  • 32.8k

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