26-36-46 is better

[ulrikmm]

Today, I took a trip 17 years back in time on a MTB!

In 1994, when I started riding in the woods surrounding Aarhus, Denmark, my friend and I both rode bikes with 26-36-46 chain wheels, and 13 - 28 rear cassettes. I have allways remembered the front end shifting as perfect, both of us using DX thumbshifters. This is the typical chainset (non-biopace, thanx):

A year ago, a colleague generously gave me his old Schwinn Series 70 PDG mountain bike, very similar to the fantastic bike, my friend rode back then (a Series 50 PDG). This picture shows a Schwinn from the same family

It has taken some months to restore the bike (rims worn thru, BB har to be cut out (!) and replaced, and find a vintage fork (Marzocchi DH3 w coil springs) and better brakes (XT V-brakes).

Today I took it for the first real deep woods spin. The ground frozen, a thin layer of snow, and hardly anybody in the forest due to the wind from the sea, and the cold.

And what a joy. This bike is short, with point-and-shoot handling, and really nice in tight singletrack sections.

But the best actually is the shifting. The shifts between all three rings are effortless, even with load on the pedals uphill, perfect shifts from 36 to 26 is a given.

Furthermore, the gearing intervals are nice, too. Closely spaced on the 7-speed cassette, the small 26 front ring is actually fine for steeper uphills, using most of the casettes sprockets. The middle 36 ring is good for flat terrain, and the big 46 ring is for fast downhill. Uphill in the 26 ring feels more smooth than any 22 ring I have been used to. And for mixed terrain, you can even stay in the 26 ring during shorter flat sections.

In theory, the friction using larger sprockets and chain wheels is also reduced. In practice, chain suck is very uncommon.

All in all, this was mountainbiking just like I experienced it years ago, only with better forks and brakes.

And it definitely makes me wonder: should the circle be completed, should shimano return to the extremely well functioning 26-36-46 chain wheel sets?

Let me hear your opinions!

 

[bodinp]

Shimano's new Dyna-Sys 10-speed groups have already moved away from 22-tooth inner rings and are now using 24 teeth. My experience with this is that it is an improvement.

I don't understand the physics behind it, but from what I can feel, there is support for what you refer to as "less friction". I seem to be able to spin 24/36 easier than I could spin 22/34, even though it's a fractionally harder gear.

Even though I have very fond memories of my 952-series XTR cranks (24/34/46), I don't see much need for a 46-tooth big ring. You won't even find rings this size on most DH bikes these days, where speeds of over 60kph (35mph) are common, so I think Shimano has the new 24/32/42 ratios fairly right. Added to that, the shifting is extremely quiet, fast and accurate.

Glad you're enjoying your retro gear. I love the fact that quality never goes out of fashion.

 

[ulrikmm]

The friction physics are simple: When the chain is driven around a cog or chainwheel, the links move with an angle to each other. The smaller the cog or chainwheel, the greater the angle. This movement causes friction, especially when you push hard on the pedals. The angle of movement is considerably smaller, when you use large chainwheels and cogs. The only downside I can think of is that larger chainwheels are heavier.

The 46 tooth chainwheel is mated to a 13 - 28 (almost like an old road cassette) cassette. Thus it is still quite usefull. However, with a modern 11 - 28 cassette, it is gearing overkill.

Chainsuck became a very common problem, when "compact" cranksets were introduced. As I have never really understood exactly what happens in the chain chainwheel interface, I have no explanation for this. Except perhaps that the chain torque is larger, the smaller the chainwheel is. Actually, this must contribute a lot to the tendency of chain suck to happen especially in the granny and middle ring.

It was in many ways a rewarding ride today. One of the rides, where you forget the machine completely, and just ride, ride, ride. A bit like runners high, today. It was also interesting that my body kind of recognised and remembered the handling traits and feel of an age-old bicycle.

 

[ulrikmm]

More about the friction issue: I guess this is why the Schrek brothers use extra large pulley wheels on their racers.

 

[Vegan Dave]

Huh...this is interesting..

I find i use the 24t very infrequently in these parts (Victoria, BC), and 99% of my trail riding is my RIP9 29er in the 34t (cassette is 11t-34t). I've also been riding my CX bike on the same trails, and i've surprised myself, being able to get up the steeper hills with a 34t compact and 12-25t cassette. The steepest bits are a real grunt, but manageable. The CX bike is also a full 10lbs lighter tho.

I've been wondering which direction i'd go if i were to change.. I kinda like having the 24t for days when i want to 'take it easy' and chill a bit more...

I often ride out to the trails, and will spin out my 44t with some frequency, so sometimes slightly bigger would be nice, but then there's an issue with clearance in some spots. I hit the 44t on occasion.

I think for fit riders, the 24t is prolly overkill, and can get by on a 26t or 28t. The double cranks have a lot of appeal to me, i'd consider 30t & 46t, that might be the best of all worlds for me personally, and lose a bit of clearance.

But i'd imagine it'd vary a lot for riders depending on fitness and terrain. Which is why the smaller tooth triples have been the standard - they cover most scenarios...

I think the 26-36-46 range might lose appeal with riders who aren't as strong, esp. as more people get on 29ers. And even for those who are, the 46t might get in the way a bit too much for most riders too.

Neat idea, but i'm fairly confident the current ratio is a well-thought compromise.

 

[mad black]

Interesting discussion! My very first MTB had 26-36-46 with a 13-30 (7-speed) all DX. While I can't remeber any complaints about the quality of shifting I do remember having trouble with the ratios. I'm a guy who likes to spin a lot and the ratio jumps between gears were simply too big. I also found myself shifting at the front way too frequently to get the gear ratio right. Also I'd hardly ever use anything from 46-23 up.

Fast forward almost 20 years and I'm riding a slightly modified XX 2x10 set-up which to me is the smartest gearing since the invention of the wheel. I run a 26-42 set-up (as compared to the recommended 28-42 or 26-39) which works perfectly fine. I don't experience any chain suck and the tightly spaced 12-36 Cassette allows for absolute minimal shifting at the front. The smallest gear of 26-36 is absolutely perfect for the super steep climbs in North Queensland.

I guess I'd agree that 26 as the smallest front ring is perfectly fine but no way that I'd go back to 7-speed or a 46 ring.