Angles and Sizes, and How They Affect Your Bike

Geometry
Bike geometry is a big term and comprises of many complex angles and lengths. Most of these remain standard for the most part and do not greatly affect the ride characteristics of a bike. However there are a few measurements that can help you select the perfect frame or bike.

1. Head Angle is the angle of the head tube and fork with the ground. Cross-country bikes have tight head angles of 70-71 degrees. All mountain and downhill bikes will have a slack head angle from 66-69 degrees. A slack head angle will allow the bike to fly through technical sections easier; the downside is slacker head angles mean slower handling and climbing. The fork length directly affects this angle. Putting a 160mm fork on a XC bike designed for 100 will give the bike a slack head angle.
2. Seat Angle refers to the angle of the seat to the angle of the chainstay. Steep angles will put you almost directly over the cranks for optimum pedal efficiency whereas slack angles will sit you back, to more easily take on the technical stuff. Bikes with slack seat angles are paired with slack head angles and vice versa.
3. Bottom Bracket Height is the clearance your bike has. Your bottom bracket is the lowest point on your bicycle and when you’re getting into technical terrain and hoppin’ rocks, clearance can become a concern. All-mountain and downhill style bikes will have higher bottom bracket heights than cross-country bikes. Nevertheless the higher the bottom bracket height the higher your center of gravity. High bottom brackets mean slow cornering but can save your chain rings from bashing into rocks.

Fit
Fit is very important when it comes to bikes. Improper fit can lead to poor control, loss of power, and even pain and joint/muscle problems. This is just a quick guide to show you what different angles and sizes do to change the performance of a bike. For info on the actual fitting process do some searching or visit your local bike shop.

1. Frame Fit is based on a couple of factors: Your height will of course be the main factor, but another thing to keep in mind is your riding style. For example a 6’2” person will be a perfect fit on a 21” cross-country hardtail, however they could also fit on a 20” or even a 19”. For long rides with less technical terrain, a larger bike will be better, in our example the 21”. Say our rider wants a hardtail but will be riding on more technical terrain with quick turns. In this case a 20” or 19.5” would be a better choice. A smaller frame will give you more control over the bike in tight and technical sections. Longer bikes will be more stable and comfortable for longer rides. I have a 20” single speed and a 19” geared hardtail. My single speed is great for cruising through national forests, while my geared hardtail is my first choice for anything really technical or fast.
2. Stem length and Angle will change your riding position on the bike. For more climbing run a longer stem (90mm –120mm), with 0-10 degrees or rise. This will keep more weight forward and put you in a more efficient pedaling position. For downhill and technical terrain run shorter stems (40 – 70mm) with 10-15 degrees of rise. For a combination run a stem in between these measurements.
3. Seat Height is a pretty easy adjustment. Sit on your seat and stabilize the bike. Put the heel of one foot on the pedal and bring the pedal down so the crank arm is parallel with the seat tube. At this point your leg should be able to straighten out completely. If you cannot straighten your leg out fully raise your seat, and if it feels like a stretch lower your seat. For more technical riding run your seat lower. This will sacrifice pedaling power but give you more room to move around as you conquer the rough stuff.
4. Seat Angle: For climbing point the nose of your saddle slightly up, for downhill and jumping put it slightly down. If you do both, keep it level.
5. Seat Position (forward and backward position) will change your riding posture. This will mainly affect your lower back. The easiest way to adjust this is just try to feel it out (concentrate on how your lower back feels, tight or stretched) or have an experienced rider watch your position.
6. Lever Position should be set up so when you brake, your arms and wrists will be in a straight line. For braking on flats your levers will be tilted downward more than for downhill. Choose a setup that will be comfortable for the majority of terrain you are riding.

Mountain Cycle Rumble Limited Edition Frame Review

Awhile back we published an interview with Chris Bourke a tattoo artist located in the UK who was contracted in order to create the custom graphics featured on the Mountain Cycle Rumble Limited Edition frame.  Mountain Cycle only produced a total of 50 limited edition frames; 25 for distribution in the United States and 25 distributed in the United Kingdom.

The Rumble hardtail frame is specifically engineered for urban assault, dirt-jumping, trail and XC riding.  Mountain Cycle is known for using the best materials and fabrication techniques in the business and this frame carries the image with its stylish and functional beautiful monocoque gussets, aggressive geometry and high-quality aluminum 6061 construction.  The frame weighs in at around 5 pounds with all hardware installed.

It’s super short and thick square chain stays make the Rumble a great jumper and fast on the berms. A slightly steeper head tube angle allows for fast handling making the Rumble a top competitor for 4-Cross. Large gussets and interchangeable dropouts designed by Mountain Cycle make it obvious that this frame is designed to be used and abused.

If you are looking for a XC specific bike, this bike is probably overbuilt and a bit overweight for your needs.  However, we really like this frame because as a hardtail this can be your only hardtail that you own, say goodbye to having a different bike for every type of riding, this frame does it all!

Making this frame truely unique and absolutely brilliant is the artwork by Chris Bourke.  I sometimes catch myself gazing at the bike’s rad graphics.  In fact, when I first received the frame my thought was that it was too nice to ride and so I have decided to mount the limited edition frame on the wall above my monitor in my office and order a new non limited edition frame to build up and ride hard.  I can’t think of another bike on the market that features such amazing graphics and great functionality in one!

Stay tuned as we will be following up to this post with several others about the build up of this frame.

Check out the pics of the Rumble Limited Edition frame below:

Rumble Specifications

Rumble US Pricing:

Standard:  $522.00
Limited Edition:  $577.00

The guys over at Mountain Cycle are doing some great things…the company is under new ownership and the new staff are working hard at producing some of the best frames on the market.  At Interbike this year, MC plans to finally unveil its slopestyle creation, the long awaited Battery.  Mountain Cycle will have 1 raw and 1 Prismatic Orange at the show (we’ll have pics up soon!).  The Battery will be available in Oct./Nov. of this year.

Mountain Bike Frame Materials

Steel is Real, But Titanium is Shiny: Ti, Carbon Fiber, Steel, Aluminum… What’s the Deal?

I’m sure you seen them; the highly polished Titanium Frames gleaming in the sun, or the retro small-tube steel frames. Maybe you’ve had the pleasure of riding on the plush where-you-want-it yet firm where-you-need-it carbon fiber, or have simply settled for aluminum. Each has a purpose and an advantage.

Steel – The Old Standard
Steel, also called cromoly, is what started it all. Back in the beginnings of mountain biking, and biking in general, steel was real and the only option when it came to frame materials. Today steel is a retro material in the biking community, but it is still often utilized in everything from Wal-Mart specials to thousand dollar and up frames. The reason why steel holds popularity is its’ flex: Steel can provide solid traction and tight handling, yet take the edge off of rock gardens and other nasty stuff. It is especially popular with hardtail mountain bikes as an alternative to aluminum, because aluminum is pretty stiff. Steel also means heavier frames and susceptibility to rust. If you get a scratch or chip through the paint it is a good idea to cover it up with some touch-up paint or even nail polish. If you are looking for a relatively inexpensive and tough alternative to aluminum, that’ll give you a little bit more relief, steel is the way to go!

Aluminum – The Newish Standard
Aluminum is today’s standard frame material, although carbon fiber is quickly changing that. Aluminum is stiff; much more so than any other frame material actively in use. Because it is stiff it is great for ultimate power transfer. On the flipside sometimes the ride can be a bit harsh. Aluminum is also pretty cheap, durable and light. It has a high strength to weight ratio and can handle scratches and dents without immediate failure or rust. It is an exceptional all-around performer, but the lack of flex is leading people to pursue the next generation of frame materials…  Read more