Shimano press fit bottom brackets

[ElCani]

I need to replace the BB on my Genesis Day One. It currently has a SM BB71 41b, which has developed play surprisingly quickly. Are there different grades of Shimano road press fit BB? I see the same product variously described as both “Ultegra” and “105” level. What is the difference between an SM BB71 and an SM BB72?

Also, why on earth would Genesis make a steel frame that takes a bloody press fit bottom bracket?!

[Eyebrox]

It's the usual range of Shimano hierarchy options. The more you pay the better the quality. There are as many advantages as disadvantages in using press fit. It's cheaper, lighter and easier installed on a factory production line. I gave up trying to remove the noises from the BB30 on my alloy Boardman and complained to Halfords who paid, after much negotiation, for another bike shop to fit a Praxis bb sleeve and a basic external bearing unit. £70 all in. Never a cheep after that and no more sleepless nights. The replacement bb lasts 3/4k miles but costs only £12 and is a cinch to change over.

[thelawnet]

AFAICT, they started off by selling SM-BB71-41a (MTB width), and SM-BB71-41b (road width).

The b vs a distinction was presumably too subtle so they quickly renamed SM-BB71-41b to SM-BB72-41b, so that BB71 is for MTB, and BB72 is for road.

As they continue to sell BB71 for MTB, it doesn't seem likely there was any improvement or update between BB71 and BB72.

SM-BB71-41b/SM-BB72-41b is used by both Ultegra/105. SM-BB92-41b is Dura-Ace (it's lighter, not sure if there are other differences). Tiagra/Sora/Claris is BB-RS500-P

The BB71 and BB92 advertise 'small ball bearings'. The RS500 does not. It may be you are better off with that.

Alternatively there are various third party BB86 bottom brackets and fixes that promise to fix creaking issues.

[Brucey]

….Also, why on earth would Genesis make a steel frame that takes a bloody press fit bottom bracket?!

the genesis brand are owned by Madison, who are also shimano importers for the UK. I would imagine that someone in shimano has said 'this is the future' or something. Probably it saves about 50p in manufacturing costs too.

However if you have two brain cells to rub together, it of course deters you from buying the bike altogether.....

cheers

[ElCani]

….Also, why on earth would Genesis make a steel frame that takes a bloody press fit bottom bracket?!

the genesis brand are owned by Madison, who are also shimano importers for the UK. I would imagine that someone in shimano has said 'this is the future' or something. Probably it saves about 50p in manufacturing costs too.

However if you have two brain cells to rub together, it of course deters you from buying the bike altogether.....

cheers

It did actually give me pause for thought, but the discount on the bike (2014 Di2 model) was huge (over 50%) and I’m comfortable enough with most bike maintenance. It hasn’t creaked, but has developed play in fewer km than any other bottom bracket I’ve owned...

Thanks for the info, everyone.

[amediasatex]

….Also, why on earth would Genesis make a steel frame that takes a bloody press fit bottom bracket?!

the genesis brand are owned by Madison, who are also shimano importers for the UK. I would imagine that someone in shimano has said 'this is the future' or something. Probably it saves about 50p in manufacturing costs too.

If the importer->brand connection were that strong or forced then you'd expect Genesis to always be using all Shimano componenets. But for several years (not sure if they are still doing it) Genesis were punting out frames with press-fit BB's but with FSA cranksets plugged into them*, (likely also 50p cheaper OEM than using Shimano).

I imagine it's a lot more fluid and based on what OEM components can be sourced for that year at appropriate cost, which obviously might favour Shimano if there is a close link, but there's always a bit of 'which way the wind is blowing' in terms of fashion and also sometimes getting a good deal from another source. Quite a few brands, and models within brands have flip-flopped back and forth between threaded BSA shells and press-fit in recent years.

*My Equilibrium came equipped that way, and despite my misgivings about press-fit, this one has been trouble free for a long time, but I did fill it with a proper amount of decent grease from the get-go, which it was otherwise lacking.

[fastpedaller]

It's the usual range of Shimano hierarchy options. The more you pay the better the quality.

Maybe I'll be so bold as to say "The more you pay the lighter or more aesthetically pleasing the product - the quality may be better or no better, and the item may or may not be as durable?"

[ElCani]

It's the usual range of Shimano hierarchy options. The more you pay the better the quality.

Maybe I'll be so bold as to say "The more you pay the lighter or more aesthetically pleasing the product - the quality may be better or no better, and the item may or may not be as durable?"

Indeed, and weight is absolutely not a consideration on this bike, so I’d be interested if anyone knows a reason why the lowest model in the range might be more durable than the 105/Ultegra/Dura Ace versions. Does it definitely have bigger balls?

[Marcus Aurelius]

The reason the manufacturers usually give for using PF type BBs is that it enables them to have more flexibility ( as in choice ) in their moulded frame designs. Why a steel frame would qualify is anyone’s guess.

[thelawnet]

It's the usual range of Shimano hierarchy options. The more you pay the better the quality.

Maybe I'll be so bold as to say "The more you pay the lighter or more aesthetically pleasing the product - the quality may be better or no better, and the item may or may not be as durable?"

Indeed, and weight is absolutely not a consideration on this bike, so I’d be interested if anyone knows a reason why the lowest model in the range might be more durable than the 105/Ultegra/Dura Ace versions. Does it definitely have bigger balls?

From what I've seen with balls you have the issue of ball material Vs race material (probably best if they are both the same - stainless is probably not an advantage), then ball size, then lubrication, then sealing. It is possible there is a difference between the sealing on the different models however it doesn't seem to be something Shimano promote

As far as bigger balls goes, that seems to be the case as then 105/ultegra and dura-ace bb's are advertised as 'small ball bearings' which does rather suggest that the lower model which lacks this boast has bigger balls.

[ElCani]

Cheers. I’ll buy the cheapo one and see how it goes...

[scottg]

[snip
Also, why on earth would Genesis make a steel frame that takes a bloody press fit bottom bracket?!

PF = Perpetually Faffing , full employment for bike shops and Praxis is making good money with
screw together BB sleeve kits.

[softlips]

How long are press fit BB lasting?

[ElCani]

Roughly 5500km, for mine. With full mudguards and exposed to very little road salt.

It’s still quiet and feels smooth but there’s definitely some play.

[gregoryoftours]

Roughly 5500km, for mine. With full mudguards and exposed to very little road salt.

It’s still quiet and feels smooth but there’s definitely some play.

Would be worth checking when it's apart that your chain set axle doesn't have a nice groove worn in it where it contacts the bearing sleeves. If so you'll have what feels like play in the bearings even with a new BB.