Subcompact cranks and BB maintenance

29 replies · 948 views

zen_
110 posts
#1May 1, 2020, 10:44 AM
I really like the gearing on the 48/32 Praxis Alba crank that came on my gravel bike, but I don't think it's a very good crank. After just ~1K miles of gravel riding, the big ring is noticeably worn, I've had two bent teeth, and the (BSA threaded..) M30 BB is making an annoying click / creak on each pedal stroke with any decent amount of torque going through the crank. I took apart the crank last night and found that one of the cartridge bearings in the BB is already really gritty.

Anyway, not going to be getting another Praxis crank, but I do want to get another 48/32 crank.

Easton EA90 (47/32)
FSA Gossamer Pro BB386
FSA Omega
GRX 800 (48/31)
Miche Graff
Other ???

Due to budget reasons I'm sorta leaning towards the FSA Gosshammer or Miche Graff (that uses a Hollowtech II BB), but am interested in opinions.

Also wondering if maybe I did some bad maintenance with the BB on this bike going to crap so fast. Would keeping the gap between the BB cups and crank filled with grease help keep junk out of there, or just attract more to be ground in if it does get through the dust covers?
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Heffe
13 posts
#2May 1, 2020, 11:29 AM
zen_ wrote:
Anyway, not going to be getting another Praxis crank, but I do want to get another 48/32 crank.

For pure reliability/performance, the Easton and Shimano cranks would be best from that list. I'm looking hard at a Chorus crankset myself. Budgetary restraints can, unfortunately, top all other considerations so the other options may have more merit in that regard. I haven't found FSA chainrings to last all that long: YMMV.
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Jeb
113 posts
#3May 2, 2020, 3:48 PM
I have a couple of FSA cranks and they have worked well for me.
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bnystrom
459 posts
#4May 3, 2020, 9:59 AM
Replacing the gritty bearing would be an awful lot cheaper than replacing the crank. You can put a different brand of chainring on the Praxis crank, too. I generally use Enduro bearings, as they're very well made, well sealed and the grease is highly water resistant. If you're mechanically-inclined at all, replacing BB bearings in external threaded cups is pretty easy.
1
GSPChilliwack
91 posts
#5May 4, 2020, 10:44 AM
I’ve got a RaceFace Cinch on my Mtb. It’ll be similar/same to the Easton. BB’s don’t last at all. When you have a threaded bb, there isn’t room for a decent sized bearing with those bigger crank spindles. I’d suggest a really good BB (ie. King)—but that blows your budget. I would absolutely stretch your budget now to go with the Shimano option. If you’re keeping the bike for any length of time or mileage, I’m sure it’s the most cost-effective option in the long-term.
1
epzamora
114 posts
#6May 4, 2020, 4:34 PM
I had a Praxis Alba 46/32 with Praxis BB on my gravel bike and it too developed some kind of creak after maybe 1,000 miles of use. My LBS said they've experienced the same on another similar bike, and so we took it apart and if i remember correctly, just cleaned the bearing(s), added new lube, and reassembled. It was fine after that.
I had zero issues with abnormally worn chainrings on the Alba.

eric/fresno, ca.
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thekenoshakid
6 posts
#7May 4, 2020, 6:27 PM
Not an objective voice here, but I've got a new Rotor 48/32 crank that needs a home if interested.
1
Rogerlc
2 posts
#8May 4, 2020, 7:22 PM
Sram makes a 46/33 combination that works well. Their Dub bottom brackets are very good and inexpensive.
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Bike John
34 posts
#9May 5, 2020, 11:32 PMedited
Rogerlc wrote:Sram makes a 46/33 combination that works well. Their Dub bottom brackets are very good and inexpensive.

The SRAM 46/33 crankset isn't cheap, and it takes a proprietary (and eye-wateringly expensive) cassette and chain. Worse still, at 1:1, 33/33 isn't a subcompact.
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bnystrom
459 posts
#10May 6, 2020, 6:55 AM
SRAM cranksets are no more expensive than comparable 12-speed products from other brands ($420 for Force). They have 12-speed cassettes available starting at $100. "Subcompact" simply refers to the fact that the chainrings are smaller than the "compact" standard of 50/34. It has nothing to do with the gear ratio on the finished bike.
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zen_
110 posts
#11May 6, 2020, 10:19 AMedited
epzamora wrote:
I had a Praxis Alba 46/32 with Praxis BB on my gravel bike and it too developed some kind of creak after maybe 1,000 miles of use. My LBS said they've experienced the same on another similar bike, and so we took it apart and if i remember correctly, just cleaned the bearing(s), added new lube, and reassembled. It was fine after that.
I had zero issues with abnormally worn chainrings on the Alba.

eric/fresno, ca.

To my surprise, the creak was gone after re-greasing everything and tightening the cups better (non-drive was a bit loose). Guess I'll just be adding another thing to the maintenance checklist to keep this spinning for awhile.

Appreciate all the input. I'll probably just go with the GRX or Miche crank with a Shimano BB for next time. Only thing I don't like about the GRX is the increased Q factor; just have to go ride one first to see if it changes the fit noticeably I guess.
1
bnystrom
459 posts
#12May 6, 2020, 11:48 AMedited
You can use Loctite #222 or #242 on the cup threads, if necessary, but if they're good and tight now, they probably won't loosen.

Is the bearing still gritty? If so, you should replace it before it fails. It's generally pretty easy to remove it from the cup, but if it starts breaking down inside, it can come apart when you try to remove it, leaving the outer race in the cup, which can be a real pain to extract.

Regarding the Q-factor, if you're riding predominantly on dirt/gravel roads or trails, you probably won't notice any difference, because you're bouncing around. I only notice Q-factor differences between my road, gravel and mountain bikes when riding on smooth surfaces, where it becomes pretty apparent.
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epzamora
114 posts
#13May 6, 2020, 12:48 PMedited
zen_ wrote:
.... Only thing I don't like about the GRX is the increased Q factor; just have to go ride one first to see if it changes the fit noticeably I guess.

Good to hear about your fix. I like the look of the Praxis crank, better than the FSAs. Not sure about your bent and worn teeth. I haven't experienced anything like that on mine.

I upgraded to the GRX 600 series crank (and Wheels Manufacturing BB) since i've been struggling with the hills on some of my bigger rides and wanted the 46/30, with an 11-34 (originally 11-32). What's the added Q-factor, 2 or 2.5mm? As @bnystrom suggested, I've not noticed any problem or issue between cranks due to the Q-factor. Maybe i'm just not sensitive enough.

eric/fresno, ca.
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zen_
110 posts
#14May 6, 2020, 10:34 PMedited
This is more just a theoretical random discussion point on the Q factor, but doesn't it also affect the chainline? 2.5mm is about 1/2 the width of an 11 speed chain.

I actually switched to an 11-34 105 cassette with the 11-13-15-17-19-21-23-25-27-30-34 cogs because while it weighs more, and I don't really need the 34t (32t was fine), these cogs were more realistic for my typical speeds at a cadence of 90-92 to minimize cross-chaining in either front ring. It actually works really well the way it is setup now, and I don't want to mess it up.
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Bike John
34 posts
#15May 13, 2020, 10:38 PMedited
bnystrom wrote:SRAM cranksets are no more expensive than comparable 12-speed products from other brands ($420 for Force). They have 12-speed cassettes available starting at $100. "Subcompact" simply refers to the fact that the chainrings are smaller than the "compact" standard of 50/34. It has nothing to do with the gear ratio on the finished bike.

1:1 was good enough, right up until it wasn't. 🤣

GRX must've been quite a wakeup call at SRAM world HQ last year! Well, message received.

However, this stuff is still crazy expensive because (1) it's wireless-only and (2) is built around that weird/proprietary Flattop chain, so in order to run the $420 crankset you also have to have the $490 rear derailleur and $350 front derailleur and a $185 cassette (I've not found these anywhere at $99) plus the shifter/calipers at $495 each. So no, nobody is getting into this on the cheap:

SRAM Force Wider Gearing

Which isn't to say they didn't get a lot right putting this together. Wider range than the mullet AXS with closer jumps between cogs, on par with Shimano's GRX ranges, and especially moving that damned front derailleur battery outboard for better tire/mud clearance was a must (GRX did something similar with their chainline BTW.)

SRAM did throw a bone to us plebs today though, with the Apex/Rival/Force dropper/hydro shifters for 1x, so people don't have to MacGyver their shifter levers anymore.

Edit: BikeRumor says the smaller BCD for the 43/30 chainset is too small to fit a Quarq spider powermeter, if that's important to anyone. I wonder whatever happened to the PowerTap G4 hub powermeter, Quarq must've shelved it after buying out PowerTap from Saris.
bnystrom
459 posts
#16May 14, 2020, 7:03 AM
Now that they've come to their senses at the crank, if they'd offer cassettes that start with an 11-tooth cog instead of a 10, I'd actually be interested.
1
zen_
110 posts
#17May 14, 2020, 10:45 AM
Bike wrote:
1:1 was good enough, right up until it wasn't.

GRX must've been quite a wakeup call at SRAM world HQ last year! Well, message received.

The gearing on this new SRAM setup looks worse than a GRX 48/31 + 11-34. The GRX has fairly even gaps in the cogs that the vast majority of gravel, and mere mortal road riding occurs in, while the SRAM is still weighted towards small gaps at the bottom, with bigger gaps at the top.
0
Koyote
288 posts
#18May 14, 2020, 1:20 PM
GRX crankset might require a new GRX front derailleur, so that becomes a more expensive proposition. But it would likely be quite reliable.
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JWB475
154 posts
#19May 14, 2020, 9:22 PM
If you are considering Easton, don't let the bottom bracket scare you off. I have 2 bikes with Easton 1x cranksets (1 carbon, 1 aluminum). I have had really good luck with Wheels Mfg. bottom brackets, they are superior to those provided by Easton (better seals, better bearings).
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Bike John
34 posts
#20May 15, 2020, 9:13 PMedited
zen_ wrote:

The gearing on this new SRAM setup looks worse than a GRX 48/31 + 11-34. The GRX has fairly even gaps in the cogs that the vast majority of gravel, and mere mortal road riding occurs in, while the SRAM is still weighted towards small gaps at the bottom, with bigger gaps at the top.

I completely agree. One advantage of that 11-34T cassette is that Shimano designed the gears steps between 13% and 8% until you get to those two smallest cogs. Even the 11-speed SRAM 11-36T cassette I ran with a 50/34 compact mostly avoided huge jumps. Where on the AXS 10-36T, that 17% jump from 24T to 28T is jarring and, as you say, right in the sweet spot.

We all understand tradeoffs have to be made designing cassettes, but this is a compromise SRAM didn't even make with their 11-36T cassette, with one fewer cog to work with.

And it blows my mind that instead, they continue to advertise the number of 1T jumps at the dusty cogs as some sort of racer badge of honor, even when marketing gravel/adventure group sets.

Koyote wrote:GRX crankset might require a new GRX front derailleur, so that becomes a more expensive proposition. But it would likely be quite reliable.

👍🏻 The GRX 810 mechanical front derailleur is only ~$50, and the 815 Di2 version is ~$200.
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