Heat Forming SKS Fenders

[BobbyJones]

Trying to mount a too big fender in a too small space- well, I really need to do some minor bending around the front fork legs.

Before I start tearing in with a hacksaw to trim the excess, has anyone heated and reformed the plastic? I seem to remember somebody mentioning something about a hair dryer...

Anyone?

Thanks!

[BobbyJones]

Hope this helps someone else: SKS fenders ARE heat moldable with a standard hair dryer. I did some forming using the following steps:

Step 1: Mount Fenders in place, but keep adjustment hardware loose.

Step 2: Deflate tires

Step 3: Jam a folded dishtowel / rag between your deflated tire and fender in the areas you need to form

Step 4: Heat target areas with hair dryer

Step 5: Slightly over-inflate tires. The jammed up towel will get pushed from the pressure, molding the target areas.

Step 6: Let cool.

Worked like a charm except where I had the rear slightly twisted, resulting in more of alteration than ideal.

[Peter P.]

Thanks for the follow up. I didn't think that would work, but you proved me wrong.

Tell me; does the heat actually mold the fender around the fork legs? Did you need to exercise care to keep from bubbling the paint (I have a real heat gun, so maybe hair dryers are not as lethal). I was thinking a WET towel stuffed under there would be a little added safety.

You were smart not to cut the material. The three-sided fender shape actually lends stiffness to it. If you were to cut away the sides to squeeze it under the crown, it'd likely be too flexy, at least the portion from the fork crown forward.

I wonder if this method could be used to straighten slightly wavy fenders?

[BobbyJones]

Well, I didn't think it would work either with all the talk about a core of aluminum- but it must be a very thin core!

Not only did I form the around the fork legs, but also formed around the calipers both front and rear. I did forget a step above and tightened my brakes against the rim before I applied heat. I was surprised it worked as well as it did. I'll post some pics later.

The heat just softens the plastic. The pressure is definitely needed to do the forming to push the softened plastic up and around the target areas.

I was a little concerned about the paint from the heat, so I concentrated on applying heat slowly from "out-to-in". The paint was fine, but the calipers sure got hot! Next time, I'll do most of the heating off the bike then mount quickly and finish up. I think a wet towel would interfere with the moulding process.

Not sure what you mean by wavy fenders? Can you explain a bit more?

[keevon]

Very cool. I'm eager to see pictures of the result.

[Peter P.]

A wavy fender is one that sits crooked despite my best efforts keeping it straight by adjusting the fender stays, or is slightly twisted along it's axis.

[vqdriver]

i'd be interested to see pics of how this turned out.

[BobbyJones]

Ok- here are pics.

The most apparent view of them being altered (Pic 1) is from the inside with the wheels off. You can see where they were formed around the forks / stays and the calipers.

Pic 2 is the front where you can see clearance around the fork and the tight fit against the caliper. With the original setup and forming, after I released the calipers I had 1-2mm of clearance on the sides of the caliper arms, but that gets lost at the slightest adjustment (minor twisting). At least the fender isn't acting as a spring / resistance for the most part.

Pic 3 shows how they sit on the bike. I'm still playing with the fender line a bit, but i'm trying to run them as far out as I can to minimize chances of rattles, etc when on dirt and gravel. It's definitely not going to look as clean as I'd like due to the flat spots / deformation where everything is squeezed in. I've got at least 8-10mm clearance in the tight spots

Question for you guys: Anyone ever NOT want to take out their new winter bike cause they don't want it to get dirty? :)

[vqdriver]

the forming actually looks kinda nice and organic
but yeah, that's some tight clearance and i can imagine lotsa rattles and rubbing on the rough. but that's easily addressed with some cut inner tube in strategic spots where it's not visible.