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Discussion Starter · #1 ·
I've just fitted a brand new radiator to my 2010 K1300S, the old one was knackered and clogged up beyond rinsing it through with water and cleaning it. New one is working superbly, although it was admittedly and expensive replacement part.

Going forward, to better protect the new radiator from road spray, I fitted a carbon 'fender extender' to the existing front fender, using Tiger Seal and plastic pop rivets. So its damn secure and fixed properly. It is not contacting the tyre but what it does appear to be doing is because the BMW fender is flexing so much at the rear, the extender rattles over bumps.

I did a bit of Googling and this appears to be common as the BMW front fender isn't braced and flexes considerably when something (even a light as a feather genuine carbon extender) is fitted to it. So I either put up with the annoying rattling noise or I try and do something about it.

My question is - has anyone managed to do anything to the front fender to minimise/reduce or eliminate the rattle? I was thinking perhaps some way of bracing the BMW fender might help, but I'm not sure how to approach that. So rather than reinvent the wheel, I thought I'd ask up here.

Cheers!!
 

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Take a plastic water or milk jug and cut a one inch to 1 and 1/2 inch wide by 6 -8 inche long strip and epoxy it into the inside of the fender and Fender extender in the center. Using the thin plastic from the jug will keep it from vibrate and you will not rub.
 

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2015 K1300S Motosport Edition
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No rattle before the extender then rattle after the extender pretty well identifies the problem. I would have to guess a lateral problem. If you are hearing a rattle, I would be concerned that something is making contact somewhere. Take a look around. I am on my third K1300S each with a not carbon fiber "Fenda Extenda" installed using only the supplied adhesive pads or 3M auto trim tape with no vibration or rattle problems. I have put a seal of black silicone along the top edge of the extender to keep dirt and sand from collecting between the extender and the fender. Yea, I know. Not helpful at all. Fender screws tight?
 

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Discussion Starter · #4 ·
Thanks for the replies, guys. Yes - the fender screws are tight but even though it is a genuine carbon fender extender and pretty lightweight, the rear portion of the BMW fender does seem rather weighed down with it which is where I believe the cause of the rattle is coming from. It just doesn't seem to take the extra, albeit very light - weight of the extender fitted to it.

I fitted it using Tiger Seal sealant and then drilled 6 x small holes through both the fender and the carbon extender which I then fitted plastic push rivets to. It's rock solid.

I have read that a way to solve it is buy a carbon front fender like an Ilmberger as it flexes much less than the OEM BMW one does. An expensive route to take but the noise is really annoying!!!
 

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You don't by any chance have any HID headlights with ballast? I had a rattle on bumps and it turned out to be a ballast loose inside the headlight housing.
 

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It will be from the tip of the extender touching the tyre. After a decent number of miles (5,000 or so) you'll see some wear on the extender where it flexes into the tyre (or rather, it's the standard fender allowing it to flex).

Mesh Art Pattern Tints and shades Grille


Window Gesture Grey Tree Pattern


Is it dangerous? Not really. If anything, it's a bonus since it will dislodge foreign bodies from your tyres.
Is it irritating? Yes. Very.
 

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Same problem here with a carbon fender extender on a '08 GT. It is annoying, and as per Richtea's pictures, there is wear on the end of the extender.
I might Try Duncans suggestion of strengthening the underside with something to see if it helps.
I thought it was the extender hitting the bottom of the front fairing, but it is more likely, as Richtea suggests, hitting the tyre.

I'll report back if I get around to doing it, and the results.
 

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I am more pesimistic. Since the back of the tire is rotating up into the trailing edge of the extender, I see the potential for the edge to hook the tire surface and damage the extender and possibly the fender. The "rattle" you hear could be the extender hooking to and releasing from the rotating tire. Good luck.
 

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The "rattle" you hear could be the extender hooking to and releasing from the rotating tire. Good luck.
It is exactly that, but not hooking/releasing, more like 'kissing' the tyre surface since the damage to the extender over many miles is minimal as you can see. It's only for a split second and at such an acute angle that I don't think it's dangerous, especially since the whole thing flexes anyway.

Having said that I did invest in a carbon fibre mudguard in the end, so I didn't have to listen to it ever again.
 

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Unfortunately, I don't have the option of a carbon fibre replacement, it being a GT. The wear/damage on mine is a bit more pronounced, and I might give it a blast of the belt sander when the mudguard is off for strengthening.

Sorry, I lied, it looks like Limberger now offer front mudguards for the K1200/1300GT/K1600GT. But at €300 a bit rich for my blood (or marriage equilibrium).

I'll try the strengthening route.
 

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Tango,

Congrats on replacing the Radiator! Always a challenge to bleed those damn systems.....

Fender Extenders may help or hinder your radiator...... Many actually reduced the needed airflow and will increase the water temp up one bar...... So, a ton of folks had to Cut the original length and find a compromise between higher engine temps or protecting the radiator.... let your conscious guide you!

We're running Solid Forks, (all the cushy dampening we had with Telelever's are gone and these forks and fender take a beating) which give us added rigidity in our forks that directly impact aux lights mounted to the forks, or in your case, vibrations in the fender and extender. Couple that with the higher speeds and Ground Aerodynamics...... you know the rest.

Douglas hit the Nail on the head with the old tried and tested Plastic Milk container strips. Epoxied or Fiber glassed into the inside of the fender and increasing the integrity of the extender.

Personally I used to Drill and Rivet the Original Fenda Extenda (whomever made that) on R bikes. No worries with airflow, and it was a solid bond.

Over the years at many BMW rallies, I've seen people use Aluminum Strips from lower screen doors (Glass them in) and Shape them as a "Spine" if you will
to keep the extension from rattling and or braking off completely,

A "kevlar" extender would not be my first choice..... as it's usually junk laminating and not aircraft quality. See the photos above.

I think you have an injection molding company in England called Pyramid Plastics...... That may reproduce the original Fenda Extenda.

and spare you the grief of poor materials, fit and fair, or rattling sounds. Drill and Rivet, or Epoxy and\or Fiber Glass.

Happy Hunting.

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