Ripley: Why BB92 instead of BB30?
I'm getting my build together and I'm looking at crank weights.... almost all the cranks are between 75 and 100 grams heavier in the BB92.
Question: When typical is to go larger diameter, thinner, lighter, why BB92 (25mm?) on the Ripley?
I'm going to dislike adding 100 grams to an expensive crankset...
I believe, and may be wrong, but the choice of BB is much more about the frame than the Crankset.
With the BB92 they end up with a wider carbon shell to attach a wider Downtube and seattube junction. Especially with what's going on in the seat tube on the ripley, every mm would count. "The bigger and larger" here on the frame and possibly enabling less weight in the frame, could be saving you those 80gms for the extra on the crankset
That's my thoughts anyhow.
I'm not sure why bb92 would force you into a heavier crankset. I've used standard gxp cranksets for my bb92 hardtail with great success. I haven't checked the weight of the bottom bracket against standard threaded, but if anything I'd imagine the bb92 is lighter.
with BB30 you are going to almost always be lighter on the total weight (cranks and BB) because with BB30 the bearings are pressed directly into the frame instead of pressing cups and bearings in with BB92.
Ah, I get it. I thought the OP was comparing weight of bb92 to threaded external. I'm still a little perplexed why this is a problem, since this is no different than the vast majority of the cranksets out there, but then again I'm not a die-hard weight weenie.
BB30 is usually found more in the road bike world, I do like the wider bottom bracket with bb92 for MTB due to the increased width for seat tube and downtube attachment as stated above.
Ripley: Why BB92 instead of BB30?
Maybe because most bb30 setups are poop, don't have great durability, and aren't well sealed? I know that's a sweeping generalization, but I just hated the one on my cannondale. Never again! Give me bb92 or good old fashioned thread-in cups.
I asked the same question to the head of Shimano R&D several years back and he told me that in their testing they found that the greater width between the bearings of bb92 provided more benefit than the larger spindle and bearings of BB30. The wider stance more than makes up for the larger diameter of bb30.
They were looking for maximum durability to weight ratio. They said they could not get any of the BB30 parts on the market to pass the fatigue tests they require. Shimano is very professional and conservative about the long term durability of their cranks. They don't know who will end up with them so they plan for the worst. Imagine a really big and strong guy who rides a lot. He's still not likely to break his Shimano BB spindle or cranks, even after years of riding. Shimano seems to have crank and bb design pretty figured out.
The frame construction also benefits from the greater width, especially on the non drive side. Those two considerations are why we use BB92.
Hans, sent ask chuck an email, looking for rear shock air pressure info on the Ripley. Please get back to me, thanks.
Originally Posted by hanssc
11 mm sag will get you in a good range.
Here's the set up guide on the Ibis web site under support.
From page 26:
We recommend the following shock
pressures as starting points for the
< 170 lbs: riding weight less 10psi
> 170 lbs: riding weight plus 10psi
=170 start with riding weight
Shoot for 11mm (.45") sag.
Less pressure gives a slacker seat
angle and overall smoother ride.
More pressure gives a firmer suspension feel and steeper seat angle and
more over the pedals riding position.
Generally about body weight in psi or a little lower (10%) is a good place to start in my experience.
Got A Lust for Life...
Re: Ripley: Why BB92 instead of BB30?
This times a million
Originally Posted by D_Man
I am immune to your disdain.
Threaded cups and iscg tabs are nice.
Originally Posted by indyfab25
This is correct I have bikes wit PF bb30 & PF bb92....
PF bb 92 durability 4 to 5 times more thane bb 30 ( in creaks & bearing fails...)
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