'07 DK Bikes & General Frame Geometry Information
We have put together this page to indicate the specs on the 2007 DK range. We have also included a frame geometry diagram with labels to show the names of the different parts to a BMX frame. Some of the terminology used in the table below might be foreign to you. We have included a section beneath the table which explains BMX jargon in simple terms.

If, after you have read this, you still have any queries feel free to give us a call on 076 221 0606 or e-mail us. We hope this helps to enlighten you as to the finer details of a complete bike and a frame.

Key to abbreviations:
TT - Top tube length
CS - Chain stay length
HT - Head tube angle
ST - Angle
BB - Bottom bracket

Frame Geometry

A - Top tube length
B - Head tube angle
C - Chain stay length
D - Seat tube angle
E - Down tube

BMX Jargon Explained:

Top Tube Length
This is one of the most important factors to consider when purchasing a frame or complete bike. The longer the frame, the more difficult it is to spin around or to manual. However, longer frames allow for more room when doing tricks like no foot can can's and bar spins. They are also more stable when jumping big gaps. The most important factor is the rider's size. A rider of 5ft who rides mostly street will struggle to ride a frame with a top tube of 21". The converse applies too, a 6ft tall rider will feel really cramped on a bike with a 20" top tube. Most taller riders prefer frames with top tubes from 20.75" to 21.25", medium size riders 20.3" to 20.6" and shorter riders from 19.5" to 20.3". Note: These are general guidelines, the ultimate deciding point is rider preference.

Chain Stay Length
Longer chain stays make for a more stable bike, but one that is more difficult to manual. Therefore, shorter chain stays make a bike manual (wheelie without pedaling) more easily but also makes it a little less stable. You'll find that dirt/trails frames will have slightly longer chain stays than park/street frames. With trail riding you will be going quite fast and generally in a straight line (even if you do spin a 360 it will be a slower rotation than a 360 off a curb, hence the longer chain stay is acceptable), with street riding you are often spinning (doing 180's or 360's) or manualling and so the shorter chain stay length is more suited!

Head Tube Angle
Steeper head tubes cause a bike to do nose wheelie's more easily, but also make them more twitchy (not drastically). Less steep head tube angles cause bikes to handle better when jumping or going fast. Some trails frames have 74° head tubes, some street frames have 75° head tubes. Most bikes have a head tube angle of 74.5° , this is good angle for all round riding.

Seat tube angle
Steeper seat tube angles cause the BB to move further back, this will cause the front end of the bike to feel longer, but the back end shorter. Shorter back ends make for easier manualling.

Cro-mo vs Hi Tensile Steel
Most "cheap" bikes are made from hi-tensile steel. This material is strong enough for a bike that is ridden to school and back, but it will not hold up to the punishment of proper BMX riding. Cro-mo is better suited to BMX because it is significantly stronger. What you will find through any manufacturers range of bikes is that they will produce their lower end bikes using hi-tensile steel (it's cheaper than Cro-mo) and they will use Cro-mo on the "expert" level bikes. Also, as you move up in the range of bikes, more and more of the frame's tubing is made from Cro-mo For example: the DK Step Up has a Cro-mo down tube (the piece connecting the cranks to the fork/headset area) where the rest of the frame is made from hi-tensile steel. The General Lee's "main tubes" (down tube, seat tube and top tube) are made from Cro-mo, the rest from hi-tensile steel. The Cleveland, 6 Pack, 4 Pack and Dayton are 100% Cro-mo

Sealed vs Unsealed Bearings
Entry level bikes use unsealed/loose-ball bearings in the headset, bottom bracket and hubs. High end bikes use sealed cartridge bearings. Unsealed bearings require fine tuning to get them working correctly and need constant adjusting to keep them running well. If the the bike is ridden with these bearings too tight or too loose the balls of the bearings will damage the inside of the hub, headset or BB cones. If this happens, the part (hub, headset, BB) will most likely need to be replaced! Sealed bearings are pressed into position and require almost zero maintenance, its is advisable to remove the bearings once in a while in order to check up on them and to re-grease the outside of the bearing so that the will not creak when you ride.

This is the inside of an "unsealed" hub. The axle will have a cone shape nut which will be tightened until it comes into contact with the ball in the hub. This requires fine adjustment. If it's too tight the hub will not spin freely, if it's too loose the cone will shake and the vibrations will cause pitting in the hub itself as well as on the cone. This will lead to the hub seizing. Note: This type hub still has a seal protecting the balls and grease from dust and water, but it is still called an unsealed hub.

This is the inside of an Odyssey cassette hub. The bearing in this hub is a sealed cartridge bearing. It is pressed into place and no fine tuning is needed. This type of bearing is far more durable than the unsealed type shown above!

Different types of bottom bracket's (BB's)

USA BB's are the old type of BB's that BMX frames used to come with. Basically, it's an aluminium cup with a bearing pressed into it. The cup would be pressed into the frame and then the bearing pressed into the cup. In the early 90's the focus of the BMX industry was to build super strong/indestructible bikes. They did this by beefing up the frames by using bigger diameter and thicker walled tubing etc. The catch was that BMX bikes became very heavy. Probably around the late 90's, riders started trying out lighter parts (sometimes using BMX racing parts) to save a bit of weight. Riders started realising that lighter bikes were easier and more fun to ride. The focus of the BMX industry then became weight saving (but strength was still key).

One of the tricks that companies tried to use was that of Euro BB's (this system is basically the same as MTB and road bike BB's). Euro BB's consist of a bearing which is pressed into a cup, the cup has thread on it and it is screwed into the frame (Euro BB frame). From the pic above, one can clearly see the size difference between a Euro and USA BB. This did help to save a little weight, BUT, the Euro bearing is far smaller than the USA. The smaller the bearing, the faster it wears out. It didn't take long before people realised that Euro BB's are not durable enough.

Fly Bikes then designed the Spanish BB, the easiest system to use. It consists of two bearings (and a spacer that runs between them) which are simply pressed straight into the frame. The Spanish BB is the best of both worlds: the bottom bracket shell on the frame is not much bigger than than a Euro bottom bracket. But because there is no cup present, the bearing is bigger!

A Mid BB works exactly the same as a Spanish BB, the only difference is the bearings' outer diameter. When Fly designed the Spanish BB they started from scratch and came up with all new sizes, these bearings had to be specially made as they were not standard size. FBM Bike Co. were one of the first companies to use the "Mid" BB. They designed their frames to work with existing USA BB bearings. A 19mm (inner diameter) Mid BB is exactly the same as the 19mm USA BB bearing, this is a standard size and is readily available from most bearing shops. A mid BB will therefore be a little heavier than a Spanish BB, but it should last a little longer and is easier to get hold of. Just about all pro frames are now available in either Mid or Spanish BB. On pro level frames you will always find the latest in technology i.e Spanish/Mid BB's and internal headsets. It takes time for this technology to filter down to entry level bikes. This year DK have introduced Spanish BB's to their mid-range 6 Pack and Cleveland!

Note: If a frame is a Euro, Mid, Spanish, or USA BB then you have to run the corresponding bearings. The frame's bottom bracket shell cannot be changed.

A USA bearing and cup.

A Euro BB cup and bearing.

A Spanish BB fitted to a frame.

Regular head tubes vs Internal head tubes

Regular Head tube (left) Internal Head Tube (right)

Head tube - The front piece on a frame where your forks go through.
Headset - The bearings and cups (if regular) that fit into the head tube

A regular head tube is designed to have a cup pressed into it. The bearing (sealed or unsealed) is then fitted into the cup. Regular headset cups require a bit of force to press them into the frame. An internal head tube requires a headset that does not use cups (an internal headset). On a frame with an internal head tube, the bearings are fitted straight to the frame. On a frame with a regular head tube, the headset cups first need to be pressed into the frame and then the bearings are fitted to the cups. Basically, an internal headset is much simpler to install and adjust. By eliminating the need for cups, weight is saved. All pro level frames feature internal head tubes.