Hi Matt!
This seems to have been a problem about 5 years ago, but not now that Hebie have redesigned their Chainglider to specifically address the problem. I recall reading at one time on the Rohloff site that Hebie would stand the costs of a replacement shell/repair if their revised Chainglider caused damage...am hunting for that link now.
Here are some relevant threads that should address your questions:
http://www.thorncycles.co.uk/forums/index.php?topic=364.45http://www.rohloff.de/index.php?id=185&tx_ttnews[tt_news]=1004&tx_ttnews[backPid]=346&cHash=c89dee50f2&L=1
http://yacf.co.uk/forum/index.php?topic=43859.0This, and subsequent replies on the same page:
http://www.thorncycles.co.uk/forums/index.php?topic=4412.msg20978#msg20978Photo of damage here:
http://www.thorncycles.co.uk/forums/index.php?topic=4412.msg20979#msg20979http://www.bicycles.net.au/2012/07/squeak-free-clean-bike-chain-hebie-chainglider/And...Andre's first use-report, with other musings linked from there:
http://www.thorncycles.co.uk/forums/index.php?topic=2467.0As a side note, Andre's thoughts are based on his own considerable experience and testing. He has written very well on his positive selection of the Hebie Chainglider following a less stellar experience with other types, described here:
http://www.thorncycles.co.uk/forums/index.php?topic=2233.0There is even more on the topic if you search the Forum archives, but the above links should answer most questions.
The only remaining problem following Hebie's redesign seems to relate to the Chainglider rubbing on the sides of thick alu chainrings (like Thorn supply); This last summer, Robin advised me the Chainglider should be used with a thinner Surly stainless chainring, like this:
http://www.sjscycles.co.uk/surly-110-pcd-5-arm-stainless-steel-chainring-38t-silver-prod20828/ He told me Thorn liked the concept of it but not the minus points: noise and extra difficulty to remove the rear wheel. A quick check of the Surly site (
http://surlybikes.com/parts/stainless_steel_chainrings ) shows they do not currently offer a 38T 'ring in the 104mm BCD I would need for my Deore HollowTech II crank. A full range is available in a 110BCD.
These are all things to weigh, and I'm getting much closer to buying a Chainglider myself, but getting the required thin chainring for my crankset presents an additional challenge.
Hope this helps,
Dan.