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I know there are online gear ratio calculators, but...


notyal
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It's more fun to speculate about it with my internet friends. 

I'm going to replace most or all of my drivetrain. I'm actually really happy with my current setup (which I've been running for several years), but it's worn out. So on the list of replacement parts are all the things that touch each other: cassette, chainring, chain, and derailleur. It's a 4 year old bike that I'm hoping to get another year or two out of, so I'm not looking to break the bank on upgrades. Currently running a GX 11 speed group, 28T chainring, 11-42 cassette, 175mm crankset, 27.5+ wheels/tires. 

As I said, I'm pretty happy with the current gear range. I rarely spin out at the high end, and when I do, I'm more than happy to coast and enjoy not pedalling. On the low end, I clean more features in the 36T cog, but I'm thankful to have one lower bailout gear when the days get long. So, just about perfect for me. Now, the things I don't know about. I want to try an oval ring. I'm also thinking about going to a 170mm crank for better clearance. I'm most concerned about how those 2 changes will feel in the lowest 2 gears rock crawling tech features (the kind of riding I most enjoy).

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I'll second the oval is great statement.  Love mine!!  With that running a 32 oval and 46 x 9, 11 speed cassette.  The 46 gives me the confidence to slowly crawl over or up anything.  It's not as big as some pie plates out there, but works well.  And I don't think I have spun out in the tallest gear yet.  This is on my 29er.

 

 

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32 minutes ago, notyal said:

Now, the things I don't know about. I want to try an oval ring. I'm also thinking about going to a 170mm crank for better clearance. I'm most concerned about how those 2 changes will feel in the lowest 2 gears rock crawling tech features (the kind of riding I most enjoy).

Regarding the oval...do not size up, and you may even consider sizing down by 2 teeth to keep the power spot the same as your current ring. Where the oval gets biggest is where you put down power for rock features. If you're running a 28T now, and you go to put power down on an 28T oval ring, you effectively have a 30T ring in that area of your stroke. That takes some getting used to. 

@Jessica and I really enjoy AbsBlack oval rings though. For me it feels like free power when you're spinning on flats and easy uphills. I used to always run 34t rings, but I eventually decided to go with 32t for last year's endurance events. But then a few months ago when got an oval, I went back to 34t not realizing I now had an effective 36t ring for power moves. That's been a bit rough. 

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I ran a 36T 1x9 for years and never had an issue where in Texas. I put a 30T up front and that was just enough.

Right my my big bike has a 50T in the back (SRAM) and I find that I cannot get into the 50T because even in a case where having the extra leverage helps, once you get to the top of the feature, you immediately spin out and lose momentum. I am considering getting a bigger front ring in the future once I wear this one down (if I ever wear it down.) I find that the 42T is the preferred climbing gear.

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On my geared bike, this is where I tend to ride on trails.  Right in the middle of the Cassette.  X01 Eagle 1295 with 32 front chainwheel.  With where I ride, I do not find the need to drop to shorter gears than the 42.  Other 2 bikes are Single 28x17 and Dingle 32x20 and 34x18.

x01 eagle1295.jpg

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21 minutes ago, DBehrens said:

 

x01 eagle1295.jpg

Pretty much the same here. Seems like I spend most of my time in a 1 to 1 ratio for the switchback / ledge obstacle courses here. Rarely, if ever do I get into the 44 because like Austinbike said, I run out of gear once I'm up on top of the feature. 

Leave the state and I use the bailout gears quite a bit. Like having the options.

 

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If thats the same one I had on there, its indexable so you should be able to tweak it some. I first installed it 180* out by mistake and it was fukt.

 

 

*on a separate but similar note*

High pivots with idlers do not play well with ovals. Had to take mine off and go back to round.

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Another thing about ovals, I've noticed that an old Shimano clutch derailer makes a small bit of a creak when the cage is tugged forward. Normally this isn't an issue...but if you have an oval you end up with that creak occurring with each rotation! Maybe I just need to disassemble and grease it up. 

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12 minutes ago, notyal said:

Any feedback on the shorter cranks? Is it going to feel weird? Less torque? Is 5mm of extra clearance going to make a difference for rock strikes? Or maybe I should go shorter to a 165mm?

I actually don't think anyone knows anything about crank arm lengths. Indeed I saw a really good article lately arguing that no one know anything about crank lengths! It then argued that it has to do with your inseam and most of us should run much shorter cranks--like kid bike short in the 140ish range. I was going to post it to my original reply, but I can't find the damn article! 

Anyway, I used to run 175, but as I got more infatuated with lower bottom bracket bikes, I settled on 170. It works for me, but I didn't actually notice a change going from 175 to 170 other than fewer ground strikes. 

 

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2 hours ago, Barry said:

I actually don't think anyone knows anything about crank arm lengths. Indeed I saw a really good article lately arguing that no one know anything about crank lengths! It then argued that it has to do with your inseam and most of us should run much shorter cranks--like kid bike short in the 140ish range. I was going to post it to my original reply, but I can't find the damn article! 

Anyway, I used to run 175, but as I got more infatuated with lower bottom bracket bikes, I settled on 170. It works for me, but I didn't actually notice a change going from 175 to 170 other than fewer ground strikes. 

 

For me shorter cranks is all about keeping hip and knee angles are big as possible due to arthritis.   I'm on 175 on everything but 172.5 on the road.  I really should go down to 165 on everything.  But I have ridden a 2020 Tallboy on familiar trails and I did get some surprising strikes.  If I ever decide to replace my Czar with something with a lower bottom bracket, I'll for sure have to go to smaller cranks.

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15 minutes ago, notyal said:

It seems like the shorter cranks would have some sort of effect on gear ratios, but from what I'm hearing, I guess it's pretty negligible? 

It's going to reduce peak torque applied directly proportional to the reduction in crank length (lever arm.)  But that's just peak torque, probably when the crank is level and you're stomping on it.  I'm sure @mack_turtle's NIH link above probably gives out more details on the overall effect.

If I was on a single-speed and I reduced crank length, I may look into going up 1 tooth on the rear cog.  But on a bike with gears, I don't think the effect is that great.

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3 hours ago, Barry said:

Another thing about ovals, I've noticed that an old Shimano clutch derailer makes a small bit of a creak when the cage is tugged forward. Normally this isn't an issue...but if you have an oval you end up with that creak occurring with each rotation! Maybe I just need to disassemble and grease it up. 

I had that on my Evil. If you grease it use white lithium. I greased mine two years ago and no noise since

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i think of it all in terms of leverage

If you're trying to move a large rock, you get the longest breaker bar for the most force multiplication. That multiplication will also move the rock the shortest distance. At some point between the gear ratios and crank length, it all becomes relative.

Also can't see 5mm making much difference with pedal clearance. I got a lot less strikes when i learned better timing and to ratchet backwards instead of continuing to pedal the crank. Trailbike has 175mm with DMR vaults.

 

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