notyal Posted October 1, 2020 Share Posted October 1, 2020 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). 1 Quote Link to comment Share on other sites More sharing options...
ATXZJ Posted October 1, 2020 Share Posted October 1, 2020 (edited) Oval is great. I like the 32t oval with 10-44 or 11-46 on my 29s. Doing a 34t round with11-50 on my 27.5 now. Calcs have their place. Like this one because I can create multiple combinations that also factor tire height, and compare. http://gears.mtbcrosscountry.com/#26I1I1 Edited October 1, 2020 by ATXZJ 2 Quote Link to comment Share on other sites More sharing options...
Ericbike6 Posted October 1, 2020 Share Posted October 1, 2020 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. 1 Quote Link to comment Share on other sites More sharing options...
Barry Posted October 1, 2020 Share Posted October 1, 2020 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. 2 Quote Link to comment Share on other sites More sharing options...
AustinBike Posted October 2, 2020 Share Posted October 2, 2020 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. Quote Link to comment Share on other sites More sharing options...
DBehrens Posted October 2, 2020 Share Posted October 2, 2020 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. 1 Quote Link to comment Share on other sites More sharing options...
ATXZJ Posted October 2, 2020 Share Posted October 2, 2020 21 minutes ago, DBehrens said: 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. Quote Link to comment Share on other sites More sharing options...
TheX Posted October 2, 2020 Share Posted October 2, 2020 I'm putting the 38T oval back on the Jake today, and back to Walnut tomorrow. The issue I had with it has to be in my head. 1 Quote Link to comment Share on other sites More sharing options...
ATXZJ Posted October 2, 2020 Share Posted October 2, 2020 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. Quote Link to comment Share on other sites More sharing options...
Barry Posted October 2, 2020 Share Posted October 2, 2020 Spending a lot of time in the middle of your cassette certainly lets you know you have the right chainring size. Given that I love all the data from rides, I've been tempted to get an AXS. Looks at the numbers. We wants it! Quote Link to comment Share on other sites More sharing options...
Barry Posted October 2, 2020 Share Posted October 2, 2020 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. Quote Link to comment Share on other sites More sharing options...
notyal Posted October 2, 2020 Author Share Posted October 2, 2020 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? Quote Link to comment Share on other sites More sharing options...
schoolie Posted October 2, 2020 Share Posted October 2, 2020 1 hour ago, DBehrens said: Dingle 32x20 and 34x18 Pics or it didn't happen 🙂 1 Quote Link to comment Share on other sites More sharing options...
Barry Posted October 2, 2020 Share Posted October 2, 2020 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. 2 Quote Link to comment Share on other sites More sharing options...
ATXZJ Posted October 2, 2020 Share Posted October 2, 2020 (edited) Running 165s and really cant tell any difference over the 175. Then again, I'm no nino. I think the grim donut had 155s (?) Edited October 2, 2020 by ATXZJ Quote Link to comment Share on other sites More sharing options...
mack_turtle Posted October 2, 2020 Share Posted October 2, 2020 (edited) https://pubmed.ncbi.nlm.nih.gov/11417428/ too nerdy for me. also this https://forums.mtbr.com/26-27-5-29-plus-bikes/paradigm-drift-omg-i-built-myself-bike-1078271.html Edited October 2, 2020 by mack_turtle 1 Quote Link to comment Share on other sites More sharing options...
TheX Posted October 2, 2020 Share Posted October 2, 2020 I'm having a hell of a time with pedal strikes on the Bronson. I've verified just under 30% sag, thinking shorter crank arms might not be a bad idea. Quote Link to comment Share on other sites More sharing options...
Ay Chihuahua Posted October 2, 2020 Share Posted October 2, 2020 If for some reason you end up with a 104 bcd crankset, I have a Wolf Tooth 32t oval you can have. 1 Quote Link to comment Share on other sites More sharing options...
AntonioGG Posted October 2, 2020 Share Posted October 2, 2020 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. Quote Link to comment Share on other sites More sharing options...
notyal Posted October 2, 2020 Author Share Posted October 2, 2020 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? Quote Link to comment Share on other sites More sharing options...
AntonioGG Posted October 2, 2020 Share Posted October 2, 2020 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. 1 Quote Link to comment Share on other sites More sharing options...
Chief Posted October 2, 2020 Share Posted October 2, 2020 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 1 Quote Link to comment Share on other sites More sharing options...
notyal Posted October 2, 2020 Author Share Posted October 2, 2020 51 minutes ago, AntonioGG said: I'm sure @mack_turtle's NIH link above probably gives out more details on the overall effect. For sure, but if mack_turtle says that a bike related article is too nerdy for him, I don't even have to click on it to know how far I'm going to get in that article. 2 Quote Link to comment Share on other sites More sharing options...
ATXZJ Posted October 2, 2020 Share Posted October 2, 2020 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. 1 Quote Link to comment Share on other sites More sharing options...
GFisher Posted October 2, 2020 Share Posted October 2, 2020 No more rock strikes! Quote Link to comment Share on other sites More sharing options...
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