And why doesn't porsche do it at the factory...

 

They actually do it halfway on the front fenders of the 996TT and ALL fenders all the way on the GT2 and GT3
Usually done on lowered cars with wider wheels where clearance is an issue...
If you feel under your rear fender for example, there is sort of a step or lip...rolling basically bends this inward and upward so it does not touch your tires
Do a search on the 996TT forum as this was disucssed at length last week

 

I TOO OWNDER WHY THEY DONT DO IT FROM THE FACTORY, I DONT THINK IT WILL costs that much extra from a building/manufacturing stand point

 

I don't think it's a matter of cost when it comes to their non lowered/sport suspension type of cars. The wheels and tires fit fine without any threat of the wheel well hitting the tires (four inches gives plenty of clearance I'm afraid!). No need to roll fenders if it won't be a concern. And I very much doubt that Porsche considers that we will actually change the wheels out for aftermarket ones. If so, that's on our dime and should be.

 

my guess is that it the .5" lip actually grabs the fender liner so it tucks over the fender lip. makes a clean enclosure. it probably also adds an additonal step to pressing out these fenders, more tooling to have the fenders rolled up as they can not be stamped that way. who knows.

 

Robyn answered this very well but I would add 2 points........a fender that is not bent all the way is a tad stronger, more rigid.....so the manufacturer will probably not fold that back completely unless they have to.

Fender prep requires some talent.........a poor job can (possibly) cause the paint to crack along that edge (not a good thing ).

 

So what't the downsides to having it professionally done.

Are the fenders weaker?
Does Water get trapped and rust out the wheel wells.

Inquiring minds want to know?

 

IMHO..........'professionally done'......no downside (cept the 'risk' of the paint I mentioned).

(even unprofessionally......no downside.....if all goes well )

 

How is is actually done? IOW, what is the process? I would think that ANY further bending would crack the paint?????

 

Any "further" bending?..........well this paint has never been 'bent' before.
As mentioned, 'cracking paint' is a possible risk.........lots a variables, kind of paint, age of paint, how far you bend under, etc.
Someone else step in here & explain a good 'professional technique.........the other end of the spectrum is a broom handle between the fender & tire .

 

u need to heat up the fender/paint a bit so it doesn't crack. proper tool is required for a perfect job. i know people use baseball bat but that's something scary.

 

I'll roll it for ya mister.