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Old 05-12-2010, 03:29 PM   #1
SlowRide13 OP
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Upside-down fork?

Edited because I answered my own question.
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Old 05-12-2010, 05:00 PM   #2
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The F800GS uses a Marzocchi Upside-Down (USD) telescopic fork, which some people also call inverted.

The F650GS2 uses a (not sure on brand) Right Side Up telescopic fork.

http://en.wikipedia.org/wiki/Motorcycle_fork#Telescopic

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Originally Posted by Wikipedia Link Above
Inverting (USD) is done for two reasons: to reduce unsprung weight by having the heavier components be suspended, and to improve the strength and rigidity of the assembly by having the bulkier and stronger component being directly supported by the pivot.[2] Such a system is referred to by many as upside-down forks or USD for short.
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Old 05-12-2010, 05:02 PM   #3
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Thanks. What are the advantages of inverted forks?
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Old 05-12-2010, 05:04 PM   #4
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Quote:
Originally Posted by SlowRide13
Thanks. What are the advantages of inverted forks?
To reduce unsprung weight by having the heavier components be suspended aka up top, and to improve the strength and rigidity of the assembly by having the bulkier and stronger component being directly supported by the pivot aka connected to the triple tree clamps.
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Old 05-12-2010, 05:17 PM   #5
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Quote:
Originally Posted by The Griz
To reduce unsprung weight by having the heavier components be suspended aka up top, and to improve the strength and rigidity of the assembly by having the bulkier and stronger component being directly supported by the pivot aka connected to the triple tree clamps.
And.....Always having the wiper seals lubed....ensuring buttery smooth action...

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Old 05-12-2010, 11:44 PM   #6
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Quote:
Originally Posted by ebrabaek
And.....Always having the wiper seals lubed....ensuring buttery smooth action...
USD forks also have a higher chance of fork tube and fork seal damage, and more fluid loss for equivalent seal damage...which leads to more probable disk/pad contamination. So its not all kittens and rainbows.

In a blind taste test, most general off road riders will actually choose conventional forks over equivalently set up USD forks--precisely because they're less stiff and overall more compliant. Not so much on road.

In the end though, USD look WAY cooler.
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Old 05-13-2010, 09:44 AM   #7
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Quote:
Originally Posted by bxr140
USD forks also have a higher chance of fork tube and fork seal damage, and more fluid loss for equivalent seal damage...which leads to more probable disk/pad contamination. So its not all kittens and rainbows.

In a blind taste test, most general off road riders will actually choose conventional forks over equivalently set up USD forks--precisely because they're less stiff and overall more compliant. Not so much on road.

In the end though, USD look WAY cooler.
+1 True true! Protect those fork seals!
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Old 05-13-2010, 11:58 PM   #8
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Originally Posted by The Griz
+1 True true! Protect those fork seals!
I have a pair of fork socks from touratech that I still haven't installed yet. They are basically just neoprene sleeves that cover the fork seals and bottom of the fork.

Is there any validity to using these? Thanks.

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Old 05-14-2010, 12:08 AM   #9
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General consensus is that fork socks do more harm than good. Whereas the wipers on the fork seals clear debris, the fork socks---which are not sealed from the elements--can trap debris. That can lead to scoring and, possibly, premature seal failure.
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Old 05-14-2010, 01:14 AM   #10
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I never used to think this but its true even if you clean them all the time, best bet is to clean your forks at the end of the day when your off road. i just use a light amount of kero on a rag and store it in a zip lock bag, all your doing is cleaning dried dirt off so it cant work its way under the dust seals.
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Old 05-14-2010, 01:27 AM   #11
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Quote:
Originally Posted by bxr140
General consensus is that fork socks do more harm than good. Whereas the wipers on the fork seals clear debris, the fork socks---which are not sealed from the elements--can trap debris. That can lead to scoring and, possibly, premature seal failure.
Interesting.

Anyone in the market for a new set of fork socks?

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Old 05-14-2010, 09:13 PM   #12
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Anyone ever put a rubber boot, like those found on conventional forks, on an inverted fork to protect the seals? Or would this work only marginally better than the neoprene sock AND look totally lame.
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Old 05-15-2010, 10:08 AM   #13
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Quote:
Originally Posted by Bartron
Anyone ever put a rubber boot, like those found on conventional forks, on an inverted fork to protect the seals? Or would this work only marginally better than the neoprene sock AND look totally lame.
I've never seen an accordion style boot on a USD fork. Impact protection is really the major thing you need with fork tubes, and the plastic guards found on USD fork setups satisfies that requirement.
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Old 05-17-2010, 07:20 AM   #14
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Quote:
Originally Posted by Bartron
Anyone ever put a rubber boot, like those found on conventional forks, on an inverted fork to protect the seals? Or would this work only marginally better than the neoprene sock AND look totally lame.
I am afraid that the last part of your post would be the case.... But you are more of a form follows function kind of guy anyway Bart!

I would just get a set of neoprene socks with a velcro closing mechanism (to easily remove them for cleaning). Then pack some grease between wiper and fork seal and you shouldn't have any problem with damage to the chrome legs or leaking fork seals.

This will increase stiction a tiny amount but since we are talking about a GS and not a lightweight enduro bike it will hardly be noticeable. Just make sure that the socks are not so long that they bunch up and prevent the forks from using the full stroke.
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Old 05-17-2010, 08:05 AM   #15
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Quote:
Originally Posted by LukasM
I would just get a set of neoprene socks with a velcro closing mechanism (to easily remove them for cleaning).
Have you ever tried to clean wetsuit? Not easy...
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