What is the geometry of a bobber frame? In other words, what are the design elements that gives a frame that bobber look or style?
I hear that question a lot, and I also hear this one as well: How is a bobber chassis different compared to regular chopper frames, and the Sportster frame?
Here’s my understanding of it but this definition is slightly different from person to person.
The Bobber is the original chopper. People would take a stock bikes and take off the front fender and cut up the back fender. They would just lighten up the bike and make it look meaner and more aggressive.
It is similar to today’s street fighter style of bike. The frame is usually left the same as the donor bike and modifications are made to keep costs at a minimum. Usually the rake is kept the same as the stock angle that the donor bike had.
Choppers on the other hand are the more expensive route in bike building. Even though some frames are called bobber frames, they truly are choppers since they are custom made from scratch.
A custom made bobber frame follows the bobber style with the stock rake angle and look. Usually, Choppers will have a rake angle that really puts that front wheel out there and also has a lot of custom looks.
The frame is significantly different from a stock frame so it is very obvious that it is not a stock frame.
A sportster is often chopped and bobbed. So a Sportster frame or frame design is the ‘sporty’ version of a chopper or bobber. The angle of the rake is kept pretty close to the original and the modifications made are an attempt to make the bike look very sporty and sleek.
A Sportster motorcycle resembles a bobber more than a chopper because it is not raked.
Like I said, the definition of what a bobber frame is varies quite a bit. Back in the day, any bike that had it’s front fender removed and rear fender bobbed, and many of the unnecessary parts and accessories stripped was considered a bobber.
Today, the bobber look has evolved to all kinds bobber styles.
You have the traditional bobber look as described. But then there is the chopper bobber look which would have a stretched and raked look, and then you have the more futuristic styles that embrace themes such as ‘steamp punk’ or whatever pleases the builders eye.
Some have ape hangers (handle bars). Some bobber enthusiasts believe it’s not a bobber unless it has ape hangers. But it’s all in the eye of the beholder.
My personal preference is the older school bobber look, that has a more sporty look to it yet retains the old school look. I am not a big ape hanger fan because they can give you less control of the bike, even though they look cool.
Lastly, the big argument is whether a rigid frame or a softail frame is truly a bobber.
There is quite a divide because when you discuss bobbers with bikers, they often get thrown in to the chopper category. And many bikers will ride to their grave on a rigid, giving the finger to softail owners.
The fact is, softails make it easier on the back for long trips. Hard tails make for a good ride around town. You really ‘feel’ the road. These types of bikes are often referred to as ‘bar hoppers’.
The good news is that softails are more popular than ever because of their comfort, and safety. And you can get or build a softail bobber frame with the shocks hidden.
Take for example this softail bobber frame:
It’s a unique design that nobody else is making, and it’s offered by custom choppers guide. Pretty awesome!
Conversely, here is the rigid bobber design, also by custom choppers guide:
Here is a rigid sportster chopper frame (250 series):
Both the rigid sportster frame and the softail sportster frame are both very well designed, as you can see. You can also make a bobber motorcycle from the design. Just build it without the front fender, and bob the rear fender, and now you have a sportster bobber built from the ground up.