29er Build Questions Answered: Stem, Bars, Seat posts, and Grips for a trail 29er
Steve from Winston Salem wrote a build request under the "Bob Builds Bikes" tab on 29eronline.Â Here is his question. We have hidden the personal details for his privacy.
Steve bought a Turner Sultan Frame, and a Fox fork with a 15mm QR axle.Â He rides road bikes but wants to ride mountain bikes. He is interested in aggressive trail riding.Â The area where he lives has a good technical trail and the North Carolina mountains are close by.Â He comes from an athletic back ground and also rides motorcycles.Â At 52 years old he doesn't feel that he will be jumping anything too large.Â At 6' 4" and 220 pounds and how and where he rides we will have to pay attention to the parts we pick.Â Lets start with the easy stuff. The stem, handle bar, seat post and grips.
Stem: At Steve's height I would recommend a 90-100 mm stem. If Steve purchased the correct size frame, on a 29er thisÂ should work well for him. The Shorter stems make for more precise handling and smooths out the front end as far as side to sideÂ movement. A long stem has kind of a break away point. This is hard to explain but I refer to it as wheel flop. When you turn a really long stemÂ to the right or left it flops instead of smoothly transitioning. This is exaggerated with 29er wheels.
In addition to the "Flop factor" The shorter stemsÂ bias your weight toward the back of the bike. This is a much more confident descending position.
Three things happen here that are debatable negatives.
First is fit. Older 29er geometry was still leaning to the short side as far as top tube length. For instance we felt that the Ventana El Rey was not suited to a short stem.Â Also Lenz bikes are still short compared to the seat tube height. For some this works really well so there is obviously exceptions to the short stem rule.
For instance the Turner Sultan in the size Large frame has a 24.25 inch effective top tube. The Large measures a 19" frame at the seat tube center to top measure.Â The Ventana El Rey size Large measures to a 19.5 seat tube.It has a 24.00 top tube. Obviously the same rider is going to need to run a slightly longer stem on the VentanaÂ to get a similar fit. Of course this is not as simple as it sounds as other factors come into play. Like seat post set back, Seat tube angle(higher the post andÂ slacker the angle, the longer the theoretical top tube is).Â In our case the Sultans geometry really rides well with a shorter stem. In my opinion even the 100mm is not my favorite. I personally ride a 80mm on most bikes even if that meansÂ I am a little cramped. The handling is so much better I would rather make the sacrifice in a little comfort, which is also a general and subjective statement, for the quick, precise handlingÂ the shorter stem gives.
Second potential negative, Weighting the front wheel: Â On steep climbs with a tall front end and your weight shifted back, the front end of the bike can become light. Worst case the front end gets so lightÂ the front wheel lifts off the ground and you loose control and fall. In the last 5 years that I have been riding and introducing others to 29ers I have only seen this happen to one personÂ and it was his first time ever riding a mountain bike. In addition to that he was using flat pedals. It happened to him on the down stroke.
Modern 29er geometry and a little technique eliminates the problem. I can ride the steepest section of local trail and never have a problem with this. 29er wheels are much more sure footed then a 26er.Â Learn to slide your weight forward in your saddle. Use the nose of the saddle, lower your chest to your bars and pedal away.
Third is leverage.: Just like any lever the longer the lever, in this case your stem, the easier it is to lift an object. In this case your front end. You see this in trials riding.Â I am still bias to a shorter stem even for this. It comes down to technique. Does the ability to shift your weight back easier with a short stem make up for less leverage? In my opinion I wouldÂ say yes.
Next topic is handle bars. For aggressive trail riding and 29ers think wide. Think about 27(still not my preference) to about 30 inches. I ride about 27.5" bars. I have been riding wide bars(and short stems) for aboutÂ 15 years now. Wide bars smooth out a 29ers steering. They increase leverage and add stability.
Down sides to wide bars: Fitting between trees. There are a couple of places were I have to lean my bike over stick my bars behind a sapling and lean the bike the opposite way to clear a skinny gap between trees. If you live in an areaÂ where clearance becomes a problem you can always cut your bars. I would say that trails this skinny are not very common especially with the new methods of trail building.
Seat post: Should you buy a set back or a straight? This is really based on fit. There are not a whole lot of people that anatomically need a set back seat post. I have lately started to prefer the set back posts. It seems that whenÂ I line my self up in the traditional fit method, that I develop pains in my hips. It is really too hard to tell you if you should be on a set back or straight post.Â If I had to pick I would say start with a straight post. By the law of averages most people will fit this just fine.
The real advice is 1) get professionally fit. 2) listen to your body!
The brand I think is the best is Thomson. They are pretty bomber and spare small parts are readily available. I am running the Easton EA-70 and it seems the bolt on the front of the post is a little awkward and seems a little soft as I have somehow bent both the front and rear bolts.
Also the finish does not seem to hold up. I am really wanting to try the new 2011 Haven parts that were previewed at Sea Otter.I will report on them when they become available. For now the Thomson is the gold standard.
If you need a less expensive seat post the Sette apx at Price Point actually is very nice for the money. The Truvative seat posts are decent as well.
To add to seat posts you can run a dropping seat post. As far as fit you can get set backs or straight dropping style seat posts. The brand I ride is a Crank Brothers Joplin R. I would try others but for now I own this one and am not inclined to spend another $300 on a different one
especially since it is not a 29er specific part. It only comes in a 30.9 or 31.8 so if your seat tube diameter is smaller you will need to look at the Gravity dropper brand.
For aggressive trail riding I think they are great. Not completely necessary as I have ridden the same terrain with out one. However it is really nice to have the option to lower your seat post on the fly without getting off the bike.Â The lower saddle allows you to lower your center of gravity for cornering. It allows you to get lower and back further on really steep terrain. If you like to bunny hop or scale tall logs, the ability to keep the seat out of the way makes these moves easier.Â I switch back and Â forth between a dropping seat post and a standard one.
Grips: Really there is only one option that I feel I can recommend with no hesitation for trail riding. Lock on Grips. ODI, Lizard Skins, Specialized, and others make a large variety to choose from. Our test bikes all run Oury Lock on grips. when they get wet they don't slip. No hair spray or wiring required to keep them from slipping. i would get a spare set of clamp bolts as they strip out fairly easy.
Other then that I could suggest looking at ESI silicone grips. The only real advantage of these is weight. They are super light. They also don't slip when wet but don't last near as long.Â Also when you are swapping shifters, brakes, dropping post remotes, or handlebars they are harder to remove.
Next post we will continue through the rest of our parts.Tweet