Confused About The Term 'Slacker' Regarding Bike Geometry

[reed scott]

I've searched here and on you tube. I'm still confused. Can somebody explain it to me like I'm 5 years old please?

 

[onlineaddy]

Slack is the opposite of steep when describing tube angles. Here is a discussion that may help with understanding its advantages and disadvantages.

 

[antboy]

Essentially lower angles on the neck and seat tube, which puts the rider further back on the bike.

 

[goldconch]

 

[ruffruff]

Another way of saying it is how far out in front of you it puts the front wheel.
Think where the wheel would be at 90 degrees.

The angle will also affect the ride and handling. Think of this bike with a 90degree headtube. It would be VERY easy to go over the bars(OTB)
since the rider would be positioned more forward over the front wheel.
And with the wheel further out it steers different.

So bikes have different geometry based on the type of terrain they are intended to be ridden in. And of course some bikes try to strike a balance for all types of riding.

 

[reed scott]

Another way of saying it is how far out in front of you it puts the front wheel.
Think where the wheel would be at 90 degrees.

The angle will also affect the ride and handling. Think of this bike with a 90degree headtube. It would be VERY easy to go over the bars(OTB)
since the rider would be positioned more forward over the front wheel.
And with the wheel further out it steers different.

So bikes have different geometry based on the type of terrain they are intended to be ridden in. And of course some bikes try to strike a balance for all types of riding.



View attachment 66587

What confused me for a while was just where is that angle we are measuring? It is from the ground. Not the top tube. You can see this if you search bike geometry on the web and look at the pictures and their labels.

 

[PDoz]

Slack, or lazy riders like bikes that steer themselves. Think freight train rather than sports car.

So it's not surprising the average baggy short clad tattoo billboard with a death wish prefers to ride something with geometry closer to a stretched out Harley Davidson instead of a Ducati.

Compare and contrast, my slack daughters Scott on the left to my Sharp daughters old fashioned giant on the right.

Now removing my smart arse hat for a moment, the modern raked out Scott with low bottom bracket and short chain stays is amazing to ride - stable over rocks yet accurate steering, it gets power to the ground heaps better than that old giant and is fantastic fun in the air. Oh, and the seat to bar distance on those bikes is almost identical, both fit a 5'11" rider ( me) , and both are fun in their own way. The old giant is incredibly nimble and great fun to zip between trees on....but just a little scary if you try and keep up with the slack daughter downhill......

 

[ruffruff]

try this

 

[Stefan Mikes]

Finally, someone asked the question I was afraid to ask myself

Thank you all for good explanation!

 

[PDoz]

try this

I never thought of using a phone app - thanks!

Is it normal that all our families bikes measure 1 degree slacker with rider aboard ( up on the pegs , the difference is up to 2 degrees seated )? Irrespective of a stock 69 or 64 degree manufacturer head angle we all went an extra degree slacker when riding. And I thought we had even sag front to rear!

 

[reed scott]

try this

That was the clearest explanation. You can buy a small (4") magnetic angle finder where carpentry tools are sold. Of course the bike must be on flat level ground to use it effectively.