xlDooM

What rear sprockets do you use when you're on the big ring on the 700x50 equipped bike? And what cadence do you like to ride at? I made another of my spreadsheets that you all love so much.



I usually ride with a cadence below 80 on the way in and up to 90ish on the way home when it's not such a big deal to be sweaty upon arrival. I made the chart for 100rpm because that's about the highest I ever do for more than a mile (I used to be a masher). The chart confirms what I mentioned before, that this gets me over 40km/h on the middle ring.

As far as your 700x50 bike is concerned, you would have to be going faster than 48km/h before you'll exceed that 100rpm in the middle ring. If you draw the limit at 80rpm, you'll already "spin out" in the middle ring at 38.5km/h. So thanks to that 39T ring on your 29er, you only need the big and small rings if you want to commute slower than 13km/h or faster than 38km/h (assuming a leisurely 80rpm cadence). You wouldn't need it at all if you were willing to spin a bit faster. Sure you can ride in the big ring if you want, but the commute-friendly gears are duplicates of those on the middle ring.

On your 26" mtb the middle ring alone would fall a bit short for my commute, maxing out around 30km/h for 80rpm. It'd still cover 75% of my rides, but it'd annoy me at times for sure. Not a great reason to insult my physique though, considering I clearly stated I ride a 29er

Ldosorio

Instead of using excel you can use the webpage https://gear-calculator.com/
It is much better!!

xlDooM

Thanks for the tip, that's a very handy applet indeed

Burton

Think I'll pass on the conversation. Way too many of those little green squares in your initial post fall under 'worst possible chainline' senerios for me to believe we're going to have any meaningful exchange of information. In fact, the only scenerio that, IMHO, represented reasonable continuous use of a drivetrain with regards to chainline was the Zee with a 36T chainring and 9-speed HG-30 cassette.

DiscTruckerMF

I just shat myself laughing!

DiscTruckerMF

In all serious to the op, you really don't need a new crank and this really isn't a mountain biking question at all, it's a general riding or a commuting question. The fact that your talking about not riding hard so that you don't get sweaty is totally understandable......to commuters not to mountain bikers!

But I will give you my take. Keep your existing crank and put a larger ring on the middle. You can buy bash guards for the outer and granny positions which will make a chain ring sandwich out of your middle ring and prevent your chain from falling off. Then you can get rid of your front shifter. Convert to a 10 speed drive train in the back and you can get an 11 36. so buy going slightly bigger up chain ring up front you get a bit more top end and by adding a 10th gear in the rear you get some more low end climbing ability.

xlDooM

Thanks for the serious response. I'll look into that. I assumed it would look like total crap if I took off the big ring, but with the bash guard it may be ok.

You've never played badminton singles on any reasonable level then

So you agree then I left chainline out of it because it doesn't matter for the point I was making. At any of the extra gears that the big and granny ring offer over the middle ring, the chainline is ok. It's only on those that overlap with the middle ring that chainlines are bad. You're right though, the 36T is superior to my current setup because it moves the common gears to the middle of the cassette.

Burton

I agree with what?
That you need that Zee? Nope - you can stick a 36 on what you have now.
That chainline is irrelivent to the discussion? Nope - it affects drivetrain life expectancy.
That you should scrap your front derailleur? Nope - it'll be lighter and more effective at keeping your chain from dropping off the front chainring than a couple guideplates.
That since one scenerio out of everything you posted made some mechanical sense that the others did too? I really hope you don't actually use your existing drivetrain the way you indicated.

You weren't really looking for input, just agreement. I gave you my opinion and you didn't like it. So just do want you want to - ultimately its your bike and your commute.

tkehler

It's a good question, but it seems to pertain more to commuting than mountain biking.

I've given this a lot of thought myself. Though I'm a mountain biker, I also commute. If I didn't have a tough long climb in the middle of my commute, I'd definitely go SS or fixie.

xlDooM

Well, I've since decided. I'm going to get two aluminium chain plates cnc'ed at my work, and those will replace the granny and big ring. Off goes the derailer I can always put it back when I find some spare time to take the bike offroad, but for now that's just not happening. Thanks all for the opinions (and argument )!