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Discussion Starter #1
I'm no mechanic and need some help. I have a '15 bike that I'd like to upgrade the crankset. Both are Shimano with external bearing brackets.

My question: are BB's a standard size/length etc? Just wondering if I need to order a new BB with a crankset.

If this is a stupid question, I won't be offended at such a response.
 

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Any Shimano crankset that uses external cup bearings should work. If you're going to get a different brand crankset you'll likely need a different bb too, shimano uses a 24mm spindle. Spindle length isn't usually a factor for bb's anymore since most cranksets are a 2-piece design where the spindle is part of the crankset.

Every crankset will list the compatible bb(s) and you can see if yours will work, if not a new one isn't that expensive.
 

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I'm no mechanic and need some help. I have a '15 bike that I'd like to upgrade the crankset. Both are Shimano with external bearing brackets.

My question: are BB's a standard size/length etc? Just wondering if I need to order a new BB with a crankset.

If this is a stupid question, I won't be offended at such a response.
Here's a vid on how to look at your frame and decide on the BB you need:
 

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Discussion Starter #4
Thank you both for the information. Looking to replace my 50/34 105 with a 46/30 GRX 600 or 800.
 

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Discussion Starter #6
The GRX crankset should bolt right on to your existing bb.
Thanks. Now I see that I'll need a GRX front der, as well, to accommodate the wider chainline (running a 105 on the current).
 

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Thank you both for the information. Looking to replace my 50/34 105 with a 46/30 GRX 600 or 800.
I'm doing this exact change (well, my starting crankset is Tiagra). I'm on 10spd bits right now, so I ordered a GRX 600 10spd 46/30 awhile ago. I should call my shop to check on the status of that order, btw. Will be using my old Shimano BB, since it's fine.

Thanks. Now I see that I'll need a GRX front der, as well, to accommodate the wider chainline (running a 105 on the current).
That may or may not be an absolute requirement. I did a LOT of reading on this, and it seems that at least some people are managing to get older front derailleurs to work. Part of it depends on clearance between the tire and the front derailleur pinch bolt as it moves through its travel. It seems there's just enough extra adjustment capacity that it should work with a slightly wider chainline, but it also means that the pinch bolt on the FD will be deeper into its travel and may interfere with the rear tire if the clearance is tight back there. I've got miles of space on my bike, so I've decided to try to get the older derailleur to work. I'd rather not buy a new GRX FD if I don't have to, as my bike requires a clamp band FD. Well, since the GRX doesn't come in that type, I'd have to buy a direct mount adapter bit AND the GRX FD, and given the install procedure of the GRX FD, I can see the install being a right PITA that I don't want to mess with if I don't absolutely have to.
 

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Discussion Starter #8
I'm doing this exact change (well, my starting crankset is Tiagra). I'm on 10spd bits right now, so I ordered a GRX 600 10spd 46/30 awhile ago. I should call my shop to check on the status of that order, btw. Will be using my old Shimano BB, since it's fine.



That may or may not be an absolute requirement. I did a LOT of reading on this, and it seems that at least some people are managing to get older front derailleurs to work. Part of it depends on clearance between the tire and the front derailleur pinch bolt as it moves through its travel. It seems there's just enough extra adjustment capacity that it should work with a slightly wider chainline, but it also means that the pinch bolt on the FD will be deeper into its travel and may interfere with the rear tire if the clearance is tight back there. I've got miles of space on my bike, so I've decided to try to get the older derailleur to work. I'd rather not buy a new GRX FD if I don't have to, as my bike requires a clamp band FD. Well, since the GRX doesn't come in that type, I'd have to buy a direct mount adapter bit AND the GRX FD, and given the install procedure of the GRX FD, I can see the install being a right PITA that I don't want to mess with if I don't absolutely have to.
Thanks Harold. I think I follow? The issue is the possibility of the rear tire hitting the pinch bolt? I thought it had to do with the frame geometry or something else along those lines.

Stupid question...doesn't chainline refer to the ability for smooth shifting across wide-ranged gears? If so, how does that impact the tire clearance? Just learning as I go, here.
 

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Thanks Harold. I think I follow? The issue is the possibility of the rear tire hitting the pinch bolt? I thought it had to do with the frame geometry or something else along those lines.

Stupid question...doesn't chainline refer to the ability for smooth shifting across wide-ranged gears? If so, how does that impact the tire clearance? Just learning as I go, here.
I mean, the issue is a combination of things. Some frame geometries won't allow the FD's pinch bolt to swing through it's entire range of motion without hitting the tire if the rear wheel is really tucked up to the seat tube. My frame allows plenty of room, even with tires near the maximum size that'll fit in the frame.

Chainline does a few things. And what you mention is ONE of those things, especially when dealing with a 1x drivetrain. There's a narrow range of optimal positions for a 1x drivetrain to be able to effectively reach the low and high range of a modern cassette without problems.

It impacts tire clearance on the narrow end of chainlines, and when you're pushing tire size as large as you can. This is why fatbikes have such enormous chainlines. It's primarily a tire capacity reason, so the chain can clear the tire. With gravel bikes, there's an interesting bit of history involved.

Road bike hub spacing was settled at 130mm for a long time. When road bikes started getting disc brakes, they started to move to 135/142mm mtb hub spacing. When that happened at the hub side of things, crankset chainline didn't change. On the whole, it wasn't a problem because it was only a couple mm, and that's generally within the narrow window for smooth shifting across a wide range 1x cassette.

With gravel bikes pushing the tire capacity side of things, now there are starting to be issues. Not on all gravel bikes. But some. Shimano figured it made sense to shift the chainline out 2.5mm to line it back up with where the chainline was on 130mm spaced road bikes. This helps the chain to avoid rubbing on the side of the tire when in the lowest gear. They also changed the pivots on the GRX FD to avoid interference problems with bikes that had rear tires tucked up to the seat tube. That became an issue for the older type front derailleurs because to reach the wider chainline, you have to pull that arm the pinch bolt is on lower than you do with a narrower chainline, which brings it closer to the tire. The arm on this FD is a pretty clear example of something with the potential to interfere with the tire.



This video shows that using a road FD is possible, but his example road FD is a newer one with a similar function as the GRX FD, so it doesn't have the same tire clearance concerns that the one in the pic above would have.



This is the FD I'm going to be using. It's an older 105 FD. The arm the pinch bolt is on isn't as long as the Ultegra I posted above, but I have clearance for days between the frame and the tire. I think the cage can handle a chainline a couple mm wider than what I have now.


0125211425
by Nate, on Flickr
 

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Discussion Starter #10
Thanks, Harold. I need to go take a look at my FD and figure it out. It's a '15 105, but not sure of the model.

If I can get the cage to move out 2.5 mm I think it may work, but lots of farting around to get into alignment. It may be easier to get the GRX FD too...
 

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Thanks, Harold. I need to go take a look at my FD and figure it out. It's a '15 105, but not sure of the model.

If I can get the cage to move out 2.5 mm I think it may work, but lots of farting around to get into alignment. It may be easier to get the GRX FD too...
I'll let you know how mine goes whenever I get the crank. Called the shop and it looks like Shimano's ship date got pushed back to a week and a half or so from now.

In my case, moving the derailleur down and then adjusting the limit screws should probably do the job. I've got new cables ready to install on this bike when I get to that point. One of the reason I'd rather not buy a GRX derailleur unless I have to is because there are a bunch of extra steps to that process, it appears, as compared to my "old" FD.
 

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Discussion Starter #12
I'll let you know how mine goes whenever I get the crank. Called the shop and it looks like Shimano's ship date got pushed back to a week and a half or so from now.

In my case, moving the derailleur down and then adjusting the limit screws should probably do the job. I've got new cables ready to install on this bike when I get to that point. One of the reason I'd rather not buy a GRX derailleur unless I have to is because there are a bunch of extra steps to that process, it appears, as compared to my "old" FD.
I've considered an 11-42 vs new crankset but that would require a new rear der since mine is a roadie mid-cage (Ultegra). And, I'm not even sure my 105 would accommodate it either....
 

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I've considered an 11-42 vs new crankset but that would require a new rear der since mine is a roadie mid-cage (Ultegra). And, I'm not even sure my 105 would accommodate it either....
I considered a more wholesale drivetrain change, too. As I said, I'm on 10spd right now, and I'm using a long cage SLX derailleur.

2x10 just works for this bike. I think if I went with a wider range cassette, I'd have to go 1x. I could make it work, but on my gravel bike, I don't really have any desire to make it 1x. The thing I'd rather do before a wholesale drivetrain change would be to install better brakes. I've got BB7's right now and have been waffling between Tektro Spyke/Spyre/HyRd, or doing a full hydro conversion. I've got Gevenalle levers, and they offer a cable-to-hydraulic trade-in program that's a pretty reasonable cost.

I'd probably even change the whole bike out before doing a major drivetrain change. Change over to one of the various drop bar adventure 29ers on the market.
 

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Discussion Starter #14
I considered a more wholesale drivetrain change, too. As I said, I'm on 10spd right now, and I'm using a long cage SLX derailleur.

2x10 just works for this bike. I think if I went with a wider range cassette, I'd have to go 1x. I could make it work, but on my gravel bike, I don't really have any desire to make it 1x. The thing I'd rather do before a wholesale drivetrain change would be to install better brakes. I've got BB7's right now and have been waffling between Tektro Spyke/Spyre/HyRd, or doing a full hydro conversion. I've got Gevenalle levers, and they offer a cable-to-hydraulic trade-in program that's a pretty reasonable cost.

I'd probably even change the whole bike out before doing a major drivetrain change. Change over to one of the various drop bar adventure 29ers on the market.
Nice. We're in similar situations in terms of gravel bike upgrading vs a wholesale purchase of a new one.

I too prefer a 2x for gravel because the gearing options are better than a 1x, and offer a smoother transition between gears.

I'm not planning on yet another new rear der, so it looks like I'll upgrade the crankset and possibly FD if the limit screw won't open up my 105 wide enough. I could go 34T but I don't think it'd be enough to make a difference from my 32.

What bikes are you considering? Seems more are on the market now.
 

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Nice. We're in similar situations in terms of gravel bike upgrading vs a wholesale purchase of a new one.

I too prefer a 2x for gravel because the gearing options are better than a 1x, and offer a smoother transition between gears.

I'm not planning on yet another new rear der, so it looks like I'll upgrade the crankset and possibly FD if the limit screw won't open up my 105 wide enough. I could go 34T but I don't think it'd be enough to make a difference from my 32.

What bikes are you considering? Seems more are on the market now.
Salsa Fargo, for one. When I was originally shopping 6yrs or so ago, my decision matrix was between the Fargo and the Vaya. I chose the Vaya because (at the time), I wanted the bike for 99.9% pavement riding, commuting in particular. I live somewhere else now, with a totally different riding environment (probably 75% gravel and 25% pavement), so a bike like the Vaya is less versatile to me since I'm not bike commuting anymore.

I honestly haven't been looking at new bikes in particular right now. I've just kinda noticed peripherally that there are more bikes like the Fargo on the market now, so I'd be looking at those a lot, too. I don't have access to the same shop deal I had 6yrs ago, so I have no real incentive to stay on a Salsa above anything else.

I've also considered just throwing more money at what I have. For now, I decided I'd tweak the gearing a bit and see how far that takes me.

If I went to a 27.5" wheel, I could bump up the tire size to mtb tire size range, which would be great on softer gravel like we get this time of year. A bunch of the local gravel roads close to vehicles this time of year because they get squishy and the FS wants to use the road graders less often. In doing a wheel change, I think I'd want to change the fork, too, for a thru axle, so I could have firmer, more predictable steering. If I do a fork swap, then I get to ask myself if I want a gravel suspension fork, or just stay with a rigid one. And of course the hydro brake swap.
 

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Discussion Starter #16
Salsa Fargo, for one. When I was originally shopping 6yrs or so ago, my decision matrix was between the Fargo and the Vaya. I chose the Vaya because (at the time), I wanted the bike for 99.9% pavement riding, commuting in particular. I live somewhere else now, with a totally different riding environment (probably 75% gravel and 25% pavement), so a bike like the Vaya is less versatile to me since I'm not bike commuting anymore.

I honestly haven't been looking at new bikes in particular right now. I've just kinda noticed peripherally that there are more bikes like the Fargo on the market now, so I'd be looking at those a lot, too. I don't have access to the same shop deal I had 6yrs ago, so I have no real incentive to stay on a Salsa above anything else.

I've also considered just throwing more money at what I have. For now, I decided I'd tweak the gearing a bit and see how far that takes me.

If I went to a 27.5" wheel, I could bump up the tire size to mtb tire size range, which would be great on softer gravel like we get this time of year. A bunch of the local gravel roads close to vehicles this time of year because they get squishy and the FS wants to use the road graders less often. In doing a wheel change, I think I'd want to change the fork, too, for a thru axle, so I could have firmer, more predictable steering. If I do a fork swap, then I get to ask myself if I want a gravel suspension fork, or just stay with a rigid one. And of course the hydro brake swap.
Did you consider the Cutthroat at all? Too aggressive for adventure stuff?
 

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Did you consider the Cutthroat at all? Too aggressive for adventure stuff?
It wasn't available at the time. I think it came out a little after I bought my bike.

Still, I lean more towards steel for hardtail/rigid bikes, anyway. Nothing against carbon per se, but there's usually a price premium for it and I'd rather have nicer bits and pieces. Also, I bought my Vaya as a frameset to replace the On-One Pompetamine frameset I was running previously. The Cutthroat wouldn't have worked with my wheels (QR) at the time.
 

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fwiw, picked up the GRX 10spd crank from the shop today.

I'll get working on it in a bit. my mtb is in the stand right now, as I just dropped the fork off for service today, also.
 

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Discussion Starter #19
fwiw, picked up the GRX 10spd crank from the shop today.

I'll get working on it in a bit. my mtb is in the stand right now, as I just dropped the fork off for service today, also.
How'd it go? I've decided on an 11-36 cassette instead of a crankset replacement and all the adjustments that need to go along with that. My Ultegra RD8000 mid can handle it.
 

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How'd it go? I've decided on an 11-36 cassette instead of a crankset replacement and all the adjustments that need to go along with that. My Ultegra RD8000 mid can handle it.
I haven't gotten to it yet. Got my mtb done, but we've had a stretch of nice days the past few that have given me the opportunity to get things done outside that have been needing it all winter.
 
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