9 types of motorcycle frames you want to know today

I am sure you definitely love motorcycles, who wouldn’t? They are fast, fun to ride, easy to maneuver, comfortable while touring, lets you explore difficult off road terrains and what not. But have you ever wondered what makes the skeleton, the back-bone of any motorcycle which handles those tortures for you. Yes, we are talking about a frame, specifically a motorcycle frame which is the skeleton or you can say the back-bone of a motorcycle.

A motorcycle frame takes most of all the structural loads of the motorcycle when you encounter any bumps, cornering loads, load during any sudden braking, off road jumps etc. But I am sure if you have given a close look, you would have found that every motorcycle has different type of frame based on the segment type of the vehicle it is meant and targeted for. Before going to the details about how many types of motorcycle frames are there, first, lets dive down into the various functions of a motorcycle frame which will make you understand better why different types of frames exists at the first place.

Various functions of a motorcycle frame

A motorcycle frame must performs certain functions for which it is designed. These are stated below,

1. It is the primary structural member of a motorcycle which mounts different components in one rigid structure
2. The engine of the motorcycle sits inside the frame
3. The swing-arm of the motorcycle is also attached to the frame
4. The front forks are attached to the head pipe of the frame
5. Critical parts such as fuel tank are also mounted in it & it is protected by the frame
6. These are usually made from welded Aluminium, steel or similar metal alloys in the form of sheets and/or tubes
7. High performance motorcycle are also made of casted Aluminium or steel with little to no welding in it
8. Should be lightweight yet strong enough to support other components of the motorcycle, rider & pillion weights, other payloads & also external loads
9. Must provide structural rigidity & flexibility when required

Types of Motorcycle frames

Backbone frame

The simplest type of motorcycle frame but these are rarely used now a days for any mass produced or road legal motorcycles. Some features of such frame are listed below,

1. Has a single main beam and the engine hangs suspended from it
2. Consists of a strong tubular backbone (and hence the name) that connects the front & rear suspension attachment areas
3. Very simple and inexpensive frame with a distinctive look
4. Lacks rigidity & strength as compared to other frame types

The examples of such frame used in a motorcycle are Kawasaki KLX 110 and Honda CX500.

Single cradle frame

Another simpler type of motorcycle frame which was used in older days. Some features of this frame are listed below

1. This frame is characterized by steel tubes that surround the engine with a main tube above & the other smaller diameter tube beneath
2. Engine is not a stressed member of the frame
3. Finds limited use at present

The examples of such frame used in a motorcycle is Honda CG125.

Split single cradle frame

A split single cradle frame is an improvement over the single cradle frame. When a single cradle frame becomes double at the exhaust/rear, it is referred to as a split single cradle frame.

The example of such frame used in a motorcycle is Honda Africa Twin.

Double cradle frame

A double cradle frame is based on single cradle frame but has additional benefits over it and that is the reason why this frame is used in wide range of modern motorcycles. Some features of this frame are listed below,

1. Uses a pair of down tubes to form two cradle (one on either side) providing additional support to the engine
2. Commonly used in simpler road motorcycles & many custom motorcycles as well
3. It has a good balance among strength, rigidity and lightness

The example of such frame used in a motorcycle are Hero Splendor Plus and Royal Enfield Continental GT 535.

Perimeter Frame or Twin-spar Frame

This frame is very widely used in modern day sports & racing motorcycles due to below listed features,

1. Originated on racing Motorcycles and currently the favorite among the prominent Moto GP teams such as Yamaha, Ducati & Suzuki
2. This frame connects the head pipe to the swing arm pivot in the shortest distance possible, reducing flexure and torsion substantially
3. Engine is mounted to the frame and it acts as a central stressed member
4. This frame is comparatively costly to manufacture

The example of such frame used in a motorcycle are Yamaha YZF R1 and BMW S1000RR.

Monocoque Frame

A monocoque frame many features but some demerits which are listed below,

1. This frame has a single piece unit that functions as seat mounting, tank and tail section supporting structural load using the external skin
2. There are no external body parts, i.e., body parts are implicit design elements of the frame itself
3. This frame has a great advantage on rigidity and are used exclusively on competition motorcycles
4. Manufacturing involves expensive machinery and as a result, they rarely make it to a normal road motorcycles
5. However, this frame finds great fit to the race track as racing teams opt for high rigidity, low weight and simple structure

The example of such frame used in a motorcycle are Ducati 1199 Panigale and Honda NR 500 GP Racer.

Trellis Frame

Trellis frames are principally and functionally are similar to perimeter frames but are constitutionally very different. Features of a trellis frame are listed below,

1. Uses the same construction principles as the perimeter frame & matches it in rigidity and weight
2. Engine is held by the frame which kind of encircles the engine while connecting the head pipe to the swing arm in the shortest way
3. Handling is much sportier
4. Being lightweight and very rigid, offers greater strength than a twin-spar
5. Formed by welding pipes into a cage like arrangement. Favorite among European bike makers like KTM and Ducati
6. Construction is a bit complex & also cost intensive

The example of such frame used in a motorcycle are Ducati Monster 695 and KTM 1290 Super Duke R.

Diamond Frame

This frame is the most common type of frame used in commonly affordable mass produced motorcycles. This frame gets its name form the frame of a bicycle (see below) where the shape of the frame resembles to that of a diamond.

The example of such frame used in a motorcycle are Suzuki Hayate & Honda CB Shine

Diamond Frame with truss structure

There is an extension of diamond frame in which the diamond structure is combined with truss like structure some extent. This type of frame are used in some of the vehicles.

The example of such frame used in a motorcycle are Honda CBR 250R and Yamaha MT-03

Conclusion

In conclusion, we have seen that that there are very different type of frame used in a motorcycle frame. Each OEM choose a particular type of frame based on the motorcycle segment & usage. I have jotted down a quick summary of each below,

• Back bone – Construction is simplest. For the customer, such frames don’t add much to the cost of the bike. For its flexibility, it finds its uses in off-road & dirt bikes.
• Diamond – Construction is not very complex, cost savings, such frames are adequately stiff & mostly light in weight
• Cradle Frames – Construction is still simple. Frames may take abuse much better. For off road/dirt bikes (mostly split single cradle)
• Trellis – Light in weight & sporty handling. Frame can stand apart as a part of the bike’s styling and provide the bike with a distinctive look.
• Perimeter – Best in class, sportiest & advanced frame for a bike. Race track bike like sharp and stable handling and braking. Mostly for sport bikes.
• Monocoque – Provides greater rigidity, delivering a superior ride and long-term durability.