Cassette Noob Queston

[m@Robertson]

More conventional rims, those used on production fatty bikes, are usually "just" 80mm or so, which is generally TWICE as wide as you might find in use on a production mountain bike. At least that's what I'm finding. Point being, 90 and 100mm rims are getting pretty extreme - and likely requiring an extreme setup just to get them functional.

I'm guessing the purpose of using something that wide is to spread out the tire tread for better grip?

No extremes necessary. The tires at lower psi levels have serious traction and can carry very heavy loads at higher pressures. I've had the bike to a total ride weight of well over 500 lbs. That framework you see in the back is functional. With some straps I'll also use the bike to haul wood to the campsite from deadfalls. And the panniers I'll be carrying on the fun rides have a capacity of 138L each.

I know you don't like fat bikes but they are much more functional than you think. But, all good. To each their own.

Interestingly because its a longtail it can go straight up a hill that any normal frame'd bike would flip in the attempt. This thing can ride up a hill my 29er enduro would have to be carried up (on the way back down the enduro wins).

 

[m@Robertson]

Just a question..

If 11T is too small because of gear ratio (this is not what you said, but if it is the case), couldn't that be solved by small chainring?

I'm just saying this because every 11T bike will be different.. some have small chainring, and some do not.

I'm not sure. Maybe not. Would the force put on that poor little cog be decreased? I think @AHicks spelled this out well as the problem is power concentrated on just a few teeth in back. I don't think reducing the teeth in front will help reduce power delivery?

I can tell you this: Standard advice in DIY groups is to run in the opposite direction from 11T cogs. On the 2wd bike I rode into work today, even with the helper motor in front reducing the strain put on the drivetrain by the 1750w, 30a BBSHD, a)my first 11T cog lasted an unheard of 1000 miles (which is great since the cog is only about $7 to replace) and b) at about 999 miles I cracked the cog... even though I'm giving it light duty vis-a-vis AWD. Usually they last in the 300-400 mile range. I had no really noticeable tooth wear, I just snapped the thing.

So with some extreme help like that, I still couldn't eliminate the issue. On my Bullitt cargo bike, which also is 2wd and also has an 11T, I essentially never use it although chain alignment is (barely) acceptable to use 11T. I designed the gearing so I don't need it, which took about four tries to get right.

BTW @SpartyOn11 back on topic for your build: You will want to do new gears pretty much for certain. Use this tool to key in your gears/wheel size etc. to see what works and what doesn't.

Bicycle Gear Speed Cadence Table | BikeCalc

Calculate cycling speeds at a specified cadence given chainring, sprocket, tire and wheel sizes.

www.bikecalc.com

 

[AHicks]

Just a question..

If 11T is too small because of gear ratio (this is not what you said, but if it is the case), couldn't that be solved by small chainring?

I'm just saying this because every 11T bike will be different.. some have small chainring, and some do not.

Regarding 11 tooth gears and big power, it's not so much about the gear ratio as it is about the surface area of an 11t gear. They're relatively small, so the load on both the gear and the chain starts getting exotic quick when a lot of power is placed on them.

You have the right picture from an effective gear ratio though. You can compensate for the 11t gear ratio by changing the chain ring.

Back in my snowmobile racing days a hundred years ago, we were working with super high power and rpms, even by today's standards. We didn't like the little gears then either - but it wasn't just about the load paced on them and the chain (which was a definite consideration), it was also about the centrifugal force generated by turning that chain around such a small gear. The force gets so high it was found to be absorbing power! So extreme, the load on the shaft supporting that gear was breaking the shafts! The cure of course, was to go to a larger gear and adjust the ratio as required elsewhere.

Not so big a deal on a geared hub bike as that 11t gear will never be placed under anywhere near the load as a bigger mid drive is going to be placing on it - with your contribution added on top of that that.....

 

[AHicks]

No extremes necessary. The tires at lower psi levels have serious traction and can carry very heavy loads at higher pressures. I've had the bike to a total ride weight of well over 500 lbs. That framework you see in the back is functional. With some straps I'll also use the bike to haul wood to the campsite from deadfalls. And the panniers I'll be carrying on the fun rides have a capacity of 138L each.

I know you don't like fat bikes but they are much more functional than you think. But, all good. To each their own.

Interestingly because its a longtail it can go straight up a hill that any normal frame'd bike would flip in the attempt. This thing can ride up a hill my 29er enduro would have to be carried up (on the way back down the enduro wins).

So you don't get the wrong picture. I have nothing against them at all. Have a totally open mind regarding them. I just know, after trying one myself, that they aren't the cat's meow they're often presented as. I can make a case for or against them. It really is about what you're trying to achieve/priorities in a compromise situation. You are NOT going to hear me endorsing 700c tires for riding on a beach for instance!

 

[Jon A]

Moral of this long story is to think about where your *usable* gearing will be. I'd dig a 50T inner cog because it means the one next to it is something like a 46T, and thats the one I'll be using. Speaking of which, chain deflection is a problem both ways. The cluster you see above is 11-46T and yes thats right I try and never use the 11. It works and I can if I want to, but still I try and avoid it. So an 11-speed system gives me 9 usable gears. If it was a 9-spd, I'd be down to 7.

Given this philosophy, a pretty strong case could be made for the Box Prime 9 being an ideal setup--with the smaller physical stackup of the cassette, you can have a better chainline on each end of it and still have use of the full range of gearing.