26" vs. 29"... some valid points

[gregk]

I am currently an exclusive roadie. However, I am starting to look around for what I want in a mountain bike for next season. I plan on doing a few races over the summer, and competing in collegiate season next fall. I have been doing a good amount of reading on 29" bikes, but I'm still up in the air. Both 26ers and 29ers have their strong points and weak points.

Let me start off by saying that I think that wheel size can largely be a function of rider size. In terms of road bikes, I think it looks silly to have a very small (~48cm) bike with 700c wheels. Smaller people need smaller wheels. Likewise with mountain bikes. It seems like riders at 6 feet tall or above might benefit from 29 inch wheels. There is no definite cutoff point of your height to decide which is right for you, but 6 feet seems to be a good place to start.

From what I understand, here are the basic advantages of both 26 and 29 inch wheels:

26:
-lighter weight (wheels, tires, forks)
-smaller wheels are stronger in general
-quicker acceleration/handling
-much more parts availability (wheels/rims, tubes, tires, forks)

29:
-rolls over small obstacles better
-holds momentum better


It seems like a trade off. 29ers hold their momentum better and roll over things easier, but in technical XC courses, there will be a good amount of accelerations and climbing, which would favor 26 inches. It seems to me that, body size aside, the wheel size is more dependent upon what kind of course you are riding. More open or flat, 29er all the way. Climbing/accelerating, 26 has it. Some of the 29er advocates say that the easier rolling is worth the weight penalty and all other disadvantages. I suppose that my biggest concerns are wheel strength and weight, since I will be racing.

Any input is greatly appreciated... help a clueless roadie out!

 

[tyler_derden]

You're forgetting about gear ratios. If you put identical gearing on a bike with 26" wheels and 29" wheels, the 29" wheel will be in a "higher gear". If you want the two to have the same gear ratios, the smaller bike will have to have bigger chainrings (or the 29" bike will need smaller chainrings). That affects which drailleurs you can use. Standardization is intended to allow the stuff to be made in large quantites, cheaply. Changing the "standard" from 26" to 29" will take time and the early adopters will, as usual, have to pay for it.

Is 29" an improvement over 26"? That depends on who you ask. The bike companies might think so because it lets them sell a whole bunch of new stuff to people at higher margins than they are getting for the 26" stuff.

TD

 

[gregk]

You're forgetting about gear ratios. If you put identical gearing on a bike with 26" wheels and 29" wheels, the 29" wheel will be in a "higher gear". If you want the two to have the same gear ratios, the smaller bike will have to have bigger chainrings (or the 29" bike will need smaller chainrings). That affects which drailleurs you can use. Standardization is intended to allow the stuff to be made in large quantites, cheaply. Changing the "standard" from 26" to 29" will take time and the early adopters will, as usual, have to pay for it.

Is 29" an improvement over 26"? That depends on who you ask. The bike companies might think so because it lets them sell a whole bunch of new stuff to people at higher margins than they are getting for the 26" stuff.

TD

Good point. I guess I didn't consider needing a new front derailleur. I know that the compact road cranks (i.e. a 50-34) require a special derailleur. Whenever I see 29ers, they always run the same gearing as 26 inch wheel bikes. I suppose that the people using these bikes typically run 1-2 cogs bigger in the rear to compensate for the difference. But even then, lets say you normally run an 11-34 on your 26 inch bike... If you were on an identically geared 29er and on a very steep climb, your 22-34 would be more like a 22-32 on the 26 inch. The best way to acheive the gearing you need on a 29er is with a smaller crankset. Does anybody know of a manufacturer that makes a front derailleur for a 42-30-20 crankset? Just curious. Running a 29er with a 44-32-22 is like running a road bike with 700c wheels and big chainrings, i.e. 55-44. It is okay for very strong time trialists, but that's about it. I have a friend who is a huge supporter of 29 inch wheels, but he commutes on his 29er, so the bigger gearing is actually more appropriate for the street.

Ok.... so gearing aside, what about the points I made in the first post?

 

[tyler_derden]

Small chainrings are generally a problem. They have a tendency to wear faster than large rings, which is why many triples have the smallest ring made of steel instead of aluminum alloy. When people have problems with "chain-suck" it is usually on the smallest chain ring because of the wear.

You'll also have problems finding a chainring smaller than 22 teeth. The chainring has to be larger than the bolt circle.

Recumbent bikes have the opposite problem- they often try to use small wheels to keep the overall bike length/weight reasonable but then they have to resort to huge chainrings because the resulting gear ratios with 16" or 20" wheels are so low. Also, on a recumbent you can push much higher gear ratios than on an upright bike, so you have to increase the chainrings size even more to compensate (or use gear ratio changing idlers or multi-speed hubs with derailleurs and cogs).

TD