Lspade

I am purchasing a 29er but my two local bike shops are telling me two different stories. I am 6'3" with a 35" inseam and Store #1 is telling me to get a 23" while Store #2 is telling me to buy a 21". I will be using this bike for fast/crazy single track in the summer and will use it as my commuter in the winter. Store #1's argument is that if I am commuting on it I want a 23" frame because it will fit perfect and Store #2's argument is that a 23" frame will be too big and sloppy. The problem is that neither have a 23" 29er in stock . The 21" at both stores feels great but for a long commute I have no idea how much I will love or hate the smaller bike.

Suggestions? Ideas? Opinions?

roastbeef

for quick, technical stuff i like a smaller frame, but that's just preference. test ride both of them.

3speed

I'm new to MTBing, but I say go with the smaller frame. You can always throw a higher rise stem on it and a seat post that will put you high and a little further from the bars. To me, a better ride in a higher risk situation is more important, and more fun while MTBing is more important. This is assuming that you aren't going to be tackling the single-track during the winter while you have the commuter stem and post on it. And those quick small things won't be a big deal to swap once in six months when the season changes and the use of the bike changes.

Lspade

^ Didnt think of this one. I also thank you for pointing out that i can switch stems each season! I am ok with riding an ackward handling bike while commuting .

FrenchFit 

I bought and built a couple of 29ers. My personal preference is smaller for a 29er, a least one size down. Sloppy is exactly right, a big 29er frame is like navigating a boat.

YamiRider1316

21" definitely. At 6'4" I have a hardtail with 22" and a fs thats a 21". The 21" feels perfect. I have really long arms and i still feel a little stretched on the 22" frame. 23" I think would just be way to big IMO.

Lspade

Hey thanks for the opinions guys. Exactly what I was looking for.

electrik

For commuting a 21" will be nicer, you don't want to be stretched out and aggressive. If you can keep your spine straight, neck not too craned and don't feel like you're digging for clams with your hands when you're on the 21" then it's probably an ok fit.

M_S

Are we talking about the same model of bike here, or just the nominal 21/23" measurements? It's the specific measurements that matter, not the listed "frame size."

Lspade

Ya. Same bike. Thanks for clearing that up.

contango 

I'm about 6'4 and my LBS said I really needed to be on a 23" frame (my bike is a 2009 Specialized Rockhopper). I went for the 21" simply because when I stood over the 23" frame I didn't feel happy with the clearance between the top tube and some sensitive anatomical parts. I figured if I did need to jump off the saddle in a hurry I'd spell doom for my unborn children.

The 21" is a little small for me in a few ways but I'm glad I don't have the worry of how high my voice will go if I do jump off the bike.

Lspade

WONDERFUL. Thanks for all of the opinions guys. I really wanted to go with the 21" and your answers sealed the deal for me.

LesterOfPuppets

Small frames are great for commuting, as long as the top tube's long enough you're not kneeing the stem all day.

Rob P.

You CANNOT fit a bike by seat tube length. A bike is fitted to you by TOP tube length.

For your size I'd say that you need to start with a top tube of around 22 1/2" long and a 110mm stem. You can add or subtract stem length to finalize the fit.

Given that length, I'd say you need either an 18 or 19 in frame depending on the mfg and their geometry specs.

As for the LBS, [b]I believe{/b] that they are using pre-jurrasic fitting charts. Before modern geometries were standardized, bikes had longer seat tubes and shorter top tubes (per size). Seats were set close to the top tube with a short seatpost and stems were around 110mm. Look at pictures to see how bikes were set up.

Today we use much longer seat posts so seat tubes are shorter. Top tubes are the longer in relation to the seat tube length than older frames. So, fitting requires that the TOP TUBE be the length which determines the frame size.

Of course it's in the LBS's interest to sell you a bike that is too big. You'll soon have to buy a new bike to replace the poorly fitted one. Which means the LBS gets to sell you TWO bikes instead of just one.

Lspade

^ wow, thank you for that info. I am going to look up the geometry for the bike im looking at (trek mamba). Thanks so much for the post.

electrik

Aka the measurement on a site called the EFF - Effective top-tube length. Although i am leaning towards reach and stack now, due to the varieties in head tube and seat-tube angles.

LesterOfPuppets

It's usually ETT, actually.
Kona likes to call it TTH for some reason. No idea what "H" stands for.

dminor 

Every maker should do reach and stack.

H for horizontal - - measured horizontally to an extrapolated intersection with the seat tube centerline.