#46
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I'm in the lower BB drop category.
Since you're running 165 mm cranks you can already go lower by 5 mm. Design for the road tire, and when you go to rough terrain the bigger tire will raise it. |
#47
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I dont see T47 going away and will future proof against just about any crankset that you'd ever want to use. If you want to run a rear brake cable internally you will need a T47 BB to get the clearance you need.
BSA may restrict your choices in the future. How? Who knows. I went T47 on a custom steel road frame, and I wish I'd done BSA - the internal routing has not proved really necessary and aesthetically the BSA would have looked better and I didnt consider that when making my choices. |
#48
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I personally like BSA, it's been around a long time and works well. Tons of crank options. |
#49
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If you dont mind doing cable shift, you can easily get a 10-46 with Sram 11 speed, too.
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#50
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#51
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But if you're looking at Sram transmission, this is a non issue. I would base designs around broader bike standards rather than what one brand might do far off in to the future - i.e. I wouldnt build a drop bar bike with post mount brakes in 2024. |
#52
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Answering an earlier question:
I'd keep your wheels and spend the limited $ on components. The thinking here is that wheels are such an easy swap to make and there are always PL deals to be had I think your rationale for the 46T ring choice to get the gears you know you ride in most makes sense. That's how I set up my gearing as well. It's more important to have close ratios in the middle of the range (for me) than at the high end of the range. I chose BSA on my Bingham but was clear on not wanting to run the rear brake hose or cable housing in the BB. It pops out at the bottom of the DT and runs under the BB back to the caliper. I like not having to mess with a BB if I want to change cabling etc., just as I wouldn't want routing through a headset. Yes, I wear my Retrogrouch medallion proudly. I would guess that T47 is more flexible in the future though - who knows what is next?
__________________
Bingham/B.Jackson/Unicoi/Habanero/Raleigh20/429C/BigDummy/S6 |
#53
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#54
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Your Bingham's routing scheme is similar to what I have in mind so it does make sense to go BSA. But I might the bullet and go T47 based on the comments here so far, might backfire (or not) in the future but who can really predict it I guess? |
#55
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#56
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__________________
Bingham/B.Jackson/Unicoi/Habanero/Raleigh20/429C/BigDummy/S6 |
#57
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Another thing that I have recently been thinking about is the "chainstay/max chainring constraint".
I see that modern gravel/all-road carbon bikes nowadays allow max chainring of 52T or even 54T (1x wide) while permitting 45mm tire clearance (the new Cervelo Aspero, for example). However, for this Ti frame I am waiting on, I originally thought 50T clearance should be feasible but it seems like with a 425mm chainstay/45mm tire clearance, the max is 46T and maybe 48T using 1x wide crankset and a chainstay yoke. My understanding is that I will have to compromise either chainstay length or max tire clearance in order to fit a >48T chainring. Now, I am not a pro racer or anything so 48T is plenty and I am not thinking about this question from a practicality perspective but more from a design perspective. What is the biggest factor that limits the max chainring size, especially on metal tubing bikes? Is it chainstay length? Bottom bracket shell width? Or chainstay shape/thickness? How is this constraint often dealt with? |
#58
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Keep in mind that these 'wide' 1x groups have chainlines spaced out further and wider q-factors, so there is a compromise there too. IMO, a 48T chainring would be pretty bonkers to have on a gravel bike, especially for a 1x. My Crux has a 42/11-40 and its fine for the local gravel (regular roads, rolling and no huge climbs) and my custom has a 36/10-42 and I'm about to switch it up to a 38/10-46. The gearing on either of those two bikes will get me almost 30mph @ 90rpm. I would not compromise tire clearance or CS length for a bigger chainring beyond a 42-44T. |
#59
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46x10 is a hair taller/faster than a 50x11. And 46x52 is lower/slower than a 34x36. But, as you say, for a 10-42 or 10-44 "wide road" cassette, a 40 or 42t ring makes sense and will be fast enough in the 10t cog for all but the fastest descents (at least for mortals/amateurs). |
#60
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Thanks guys for the insights!
Completely agree that 48T is bonker. My default setup will be 46T + 10-52T mullet, which is good for 99% of my riding. My wish for a 48T is more for the occasional pure flat road rides where I prefer some of the gear ratios that it offers. In other words, my thinking of chainring size is more to fine tune the gear ratios in the middle rather than to achieve a higher max/min gear ratio, if that makes sense. |
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