New Cervelo Aspero

[EB]

Originally Posted by prototoast

Yeah, it's an outboard t47 on one side and an inboard t47 on the other side.

What a "bright" idea!

But why?!

[Mark McM]

Originally Posted by EB

What a "bright" idea!

But why?!

When this was first developed, the reason behind it was a bit questionable, but it might actually make a difference on a gravel bike.

The lateral stiffness of the rear triangle can be increased if the chainstays are laterally wider at the bottom bracket. This is why systems like BB86 (86.5mm wide BB shell) and BB90 (90mm wide BB shell) were developed. But even with wider BB shells, chainring clearance still limits the width of the right (drive side) chainstays. So often the end of a BB68 or BB90 BB shell sticks outward from the chainstay width on the right side.

So, the makers of BBright figured, "why not make the BB shell and chainstays wider on the left, but leave it the standard width on the right where the chainrings limit clearance?" Thus was born BBright, whose 79mm wide BB shell extends 45mm on the left (like BB90), but only 34mm on the right (like BSA). To maximize BB bearing stance width but still work with standard crank spindles, the left BB cup is internal to the shell, and the right BB cup extends outward from the BB shell.

So, BBright has always been a bit of a mish-mash for road bikes. But on gravel bikes, it might actually make sense. To accomodate wide tires but a relatively narrow chainline and Q-factor of gravel drivetrains, the chainstay on the right has to be quite narrow. In order to give good lateral stiffness, this means the left chainstay has to be much wider. The BBright BB shell accomodates large chainstay width differentials, so it is uniquely suited to gravel bikes.

[prototoast]

Originally Posted by EB

What a "bright" idea!

But why?!

I believe when they first launched "bbright" it in 2010 (?), they made claims about how there were asymmetric forces on the drive side and the non-drive side, and so adopting an asymmetrical bottom bracket area would allow them to better match the frame stiffness to the desired ride quality.

This newer version uses threaded t47 cups instead of the original press fit cups, but the same basic concept applies.

No idea if it has any meaningful impact on performance, but they're in too deep now to just do something normal.

[Wunder]

That makes some sense, but what does an INBOARD T47 on the NDS even mean? My understanding of T47 is that it's a threaded system and if the bearing is inboard of the frame how would you manage to engage the wrench flats? BBRight uses either press in bearings (like PF30) or thread together inside the frame (my R3 uses this).

[prototoast]

Originally Posted by Wunder

That makes some sense, but what does an INBOARD T47 on the NDS even mean? My understanding of T47 is that it's a threaded system and if the bearing is inboard of the frame how would you manage to engage the wrench flats? BBRight uses either press in bearings (like PF30) or thread together inside the frame (my R3 uses this).

https://www.kogel.cc/products/t47-as...bottom-bracket

There's a small flange. Brands like Trek have gone all in on just straight inboard t47. Reports are that it's kind of annoying to work with and you have to be careful with your tools, but cervelo isn't making this up themselves.

[Wunder]

Originally Posted by prototoast

https://www.kogel.cc/products/t47-as...bottom-bracket

There's a small flange. Brands like Trek have gone all in on just straight inboard t47. Reports are that it's kind of annoying to work with and you have to be careful with your tools, but cervelo isn't making this up themselves.

Interesting, I guess that isn't that different than what is in my R3 (small flange NDS, presumably to hold it steady) and big flange on drive side (to torque it down). Except that on my BBRight R3 the threads are in the middle of the BB sleeve rather than the frame. Honestly, don't know how hard that is to work with as it came pre-installed and I've had no cause to remove it in five years and 12,000+ miles.

I think Cervelo basically used an OEM version of this on my R3:

https://wheelsmfg.com/bbright-out-an...nks-black.html

[benb]

Now I want to see what these Internal T47 Treks look like IIRC once the cranks are on you can't see any difference between the old BB90 ones. I don't recall being able to see the flange in the bike shop, but I wasn't looking.

You guys are making me wonder if my BB90 Trek is now creaking from the BB. I just got finished replacing the chainring bolts to get rid of that noise. Just checked the chain and it is definitely not the chain or cassette. It's not horrendous but it is making noise, and the frame design seems to amplify noises. It's also not exactly the same noise I've seen with older BBs getting loose so I'm wondering how much of it is in my head.

But I rode my Space Horse on Sunday and that thing is just dead quiet compared to the Trek that costs 4x as much.

I would be pretty interested to see a breakdown of all these and what the Q-factor works out as. The BB90 Trek seems like it has narrower Q-factor than a lot of bikes I've had, which has not been good for me, it took me quite a while of owning it to realize the Q-factor being too narrow was messing up my pedal stroke and balance. It's a ridiculously faster bike than the Space Horse but I could never figure out why intervals felt so comfortable on the Space Horse till I realized it might be the Q-factor.

[yinzerniner]

Originally Posted by Wunder

That makes some sense, but what does an INBOARD T47 on the NDS even mean? My understanding of T47 is that it's a threaded system and if the bearing is inboard of the frame how would you manage to engage the wrench flats? BBRight uses either press in bearings (like PF30) or thread together inside the frame (my R3 uses this).

Inboard T47i Cups (usually used on 86mm wide BB shells): You have roughly 1.5-2.5mm of tool purchase on the external flange/splines, and bearings are between the cups and the shell:


Outboard T47 Cups (usually on 68mm wide BB shells): You have the bearings fully outside the shell but still within the cups. The splines are also fully outside the shell, with toll purchase on the exterior cups or on flanges/splines depending on BB model


The T47a have one internal (NDS) and one internal (DS). They elected to go with the spline on the DS external cup instead of using the cup for installation, probably so you only need one tool for install:


Ceramic Speed shows the different models pretty clearly
https://ceramicspeed.com/collections...p.bb_type=T47a

[Wunder]

Originally Posted by benb

I would be pretty interested to see a breakdown of all these and what the Q-factor works out as. The BB90 Trek seems like it has narrower Q-factor than a lot of bikes I've had, which has not been good for me, it took me quite a while of owning it to realize the Q-factor being too narrow was messing up my pedal stroke and balance. It's a ridiculously faster bike than the Space Horse but I could never figure out why intervals felt so comfortable on the Space Horse till I realized it might be the Q-factor.

A BB90 trek and a Space Horse (presume 68mm BSA with external bearings) should have identical Q-Factor assuming both are using the same Shimano crank. BB90 is basically 68mm shell plus putting the 11mm bearings inside the frame (68+11+11=90). BBRight is same Q as well (79+11=90) but allows for oversized bearings due to the wider shell.

FWIW when I pulled the cranks from my wife's BB90 Domane a year or two back one of the bearings fell out of the frame. Trek replaced the BB90 cups as a warranty job.

This overview is a decade old but still applies for BSA/BB30/BBRight/BB90. Q-factor addressed in last paragraph:

https://www.slowtwitch.com/Tech/Bott...ards_2573.html

[EB]

I can hear future me cursing at a slipped BB tool and a stripped cup interface from all the way over here.

[Mark McM]

Originally Posted by Wunder

FWIW when I pulled the cranks from my wife's BB90 Domane a year or two back one of the bearings fell out of the frame. Trek replaced the BB90 cups as a warranty job.

One of the issues with BB90 is that the bearings aren't fitted into cups, they are pressed directly into the shell. Sometimes the bore in the shell is out of tolerance, and sometimes the bore in the shell gets enlarged with use, if the bearing fit is so loose that they can move around a bit. Trek's solution was to create special bearings with an oversized OD, so that they fit tightly in a shell who's bore has become oversized.

It is often advised that the bearings in BB90 frames be installed with bearing retaining compound, so that the bearings don't move even if the bore is out of tolerances.

[benb]

Maybe I'm going to be taking it in. Certainly not worth buying any tools if there's basically zero chance I end up with another BB90 bike.

TBH even if the frame was toast somehow (surely it isn't if they could just put the oversized ones in) the bike has had a pretty good life so far with possibly the least cost/hassle/breakage of any road bike I've had.

And it could just be I'm hearing something else.

[StressStrain]

I really like the Wheels Mfg T47 external bottom bracket on my Hakka, but all these continued changes to bb 'standards' makes me think BSA worked just fine. And you know, was an actual enduring standard.

[prototoast]

Originally Posted by StressStrain

I really like the Wheels Mfg T47 external bottom bracket on my Hakka, but all these continued changes to bb 'standards' makes me think BSA worked just fine. And you know, was an actual enduring standard.

T47 is really useful for metal frames, because it allows for more clearance for wider spindles and cables to run through the bottom bracket. For carbon frames where the area between the cups isn't just a cylinder, the only real advantage of t47 over BSA it allows for the use of short spindle 30 mm cranksets, but that's a pretty minor benefit, especially since those don't seem to be in production anymore.

[EB]

Originally Posted by prototoast

T47 is really useful for metal frames, because it allows for more clearance for wider spindles and cables to run through the bottom bracket. For carbon frames where the area between the cups isn't just a cylinder, the only real advantage of t47 over BSA it allows for the use of short spindle 30 mm cranksets, but that's a pretty minor benefit, especially since those don't seem to be in production anymore.

One *apparent* advantage of T47 is that it allows for 30mm spindles with larger OD bearings, which seems to have some "bearing" (pun intended) on bearing life. Anecdotally I have observed that T47 BB bearings seem to last longer with 30mm spindles than BSA30 BB bearings.