The front portion of front fender CAN make your motorbike , or your bicycle , more aerodynamic .
On a bicycle , the average front fender does not work that way .
All other aspects of fenders are neutral at best , and usually worsen the vehicle's aerodynamics .
The easiest proof is to simply look at a photo of a world-class road racing motorcycle . There are limits ( in the rule-books ) to how large a front fender can be . Road racing motorbikes generally use the largest most coverage that they can get away with . They won't let them enclose the wheel too much , for fear of what would happen in a strong gusty cross-wind . But look closely . It's all out in FRONT of the front fork !! Think about the aerodynamic load of a spinning front tire . The top of that tire is going , MUCH faster than the whole rest of the vehicle is traveling !! And the top of the front tire is always going "against the wind" !! So , if you can protect the front of the front tire , from the wind , or actually looking at it the other way , protect the wind from the spinning front tire , you CAN make your vehicle more aerodynamic .
If Formula One racing cars were allowed to use fenders , they would , instantly . Having the wheels sticking out in the breeze is bad . The tops of the front tires are far and away the worst offenders !!
On a bicycle , the seat tube protects the front of the rear tire . Think about aerodynamic bicycle frames with curved "cut-outs" in the seat tube for the rear tire .
So , what about smoothing the airflow , or trying to smooth the airflow , behind the tires ?
Again , take a look at road racing motorbikes .
The efforts are very minimal . The rewards are just not enough to justify much effort .
The BIGGEST and most IMPORTANT aspect of an aerodynamic front fender ??
Tight & close & form-fitting !!!!
It would need to wrap around the sides of the front of the front tire . It would need to travel forward , around the front of the front tire , MUCH farther than the average bicycle fenders do today .
Bicycle fenders today , look like motorbike fenders from the 1920's .
And , I use them and love them !! But then , I'm the kind of nut who reads something called , "The Classic Rendezvous Mailing List" .
I just read on a Sheldon Brown web page , only two days ago , about painting SKS / Esge fenders successfully . I was inspired ! I've been thinkin' about it for two days . Now , today , both Dennis & Sheldon write in about it !! Cool !!
I'm gonna try it .
> guys and dolls,
> I'm no expert, but I would have thought that fenders increase the "frontal
> area" of a bicycle,
> thus making it less aerodynamic, in the same way that fatter tires cut a
> bigger hole in the
> air than narrow ones.
> Grant McLean
> - Why I like them: aerodynamic advantage, look nice, 10 minutes of
> rain can spoil your ride without fenders
> - Which ones: Honjo. Lighter than plastic, don't rattle, look nicer,
> more coverage. Second choice: stainless from France (always shiny,
> indestructible). Third choice, if you live in a dry place with only
> occasional rain: Berthoud carbon. Not much lighter, but they fit
> close-coupled racing bikes.
> - How to mount: Vintage Bicycle Quarterly No. 2 had an article with
> photos. It's important to do it right, otherwise, they won't last.
> A future article in VBQ will compare different fenders...
> Jan Heine
> Vintage Bicycle Quarterly