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Upside down forks


Slowlycatchymonkey
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I’ve always wondered why upside down forks. People look at my bike and one a a stand alone comment with no following comment is “upside down forks”

After having made up some of my own damn fine reasons up why the forks would be upside down I finally got round to looking it up. Seems it really won’t make much difference to the average rider because they’ll never test their forks to the limit anyway.

https://www.motorcyclenews.com/news/2002/february/the-reason-behind-upside-down-forks/

Any opinions......

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Doesn't mention lower unsprung mass which is another important benefit of USD forks.

 

Could you explain for a thicky?

 

Unsprung mass is made up of components connected to the suspension, rather than supported by it.


So unsprung mass are things like the wheel, brakes, fork lowers, etc. The more of this there is, the more work a spring has to do to keep the wheel in contact with the road.


On conventional forks, the fork lowers make up part of the weight of the wheel. On an upside down setup, what would normally be the fork lowers are attached to the bikes headstock so is part of the bikes sprung mass. The less weight that is unsprung, the more a spring can be tailored to just doing one job, and the better handling your bike will be.

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I understand that sometimes it also to do with how they’re homolugated for racing. Some classes are not allowed modification so they put it on all bikes and it’s then not an issue. Dunno if that’s true though.


I’m told upisde down forks are harder to work on because they have no drain screw so can cost more at a garage if there’s a problem, leak faster and in a less obvious way when they go and have the added risk of being next to your brakes if they leak :scratch: hmmm.

Look good though ay!

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I’ve always wondered why upside down forks. People look at my bike and one a a stand alone comment with no following comment is “upside down forks”

After having made up some of my own damn fine reasons up why the forks would be upside down I finally got round to looking it up. Seems it really won’t make much difference to the average rider because they’ll never test their forks to the limit anyway.

https://www.motorcyclenews.com/news/2002/february/the-reason-behind-upside-down-forks/

Any opinions......

...A bit like radially-mounted brake calipers (and dare I say it, master cylinders). As you say, riding 11/10ths on track......maybe, on the road......?


Personally speaking, I've ridden both and never really noticed a vast difference. I would have thought the main benefit would derive from the increased rigidity rather than the reduction in unsprung weight. Having said that, my old Guzzi had 35mm fork stanchions (yes, 35mm!!!) and it was still one of the best-handling bikes I've ever had.

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I’m told upisde down forks are harder to work on because they have no drain screw so can cost more at a garage if there’s a problem, leak faster and in a less obvious way when they go and have the added risk of being next to your brakes if they leak :scratch: hmmm.

Look good though ay!

 

Or maybe problems are rare and when they do occur, in this age of social media the people with problems scream the loudest and so people think a rare problem isn't so rare.

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Unsprung mass reduction can also make the ride smoother.

By reducing the ratio of unsprung to sprung mass the transfer of inertia from the unsprung mass (wheel, brakes etc)to the sprung mass (bike and rider) will also be reduced.

It's the reason why big heavy cars feel less bumps on the road but small lightweight cars fell all the bumps.

Same for bikes. As bikes get lighter, if the unsprung mass wasnt also reduced the ride would feel harsher.

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...A bit like radially-mounted brake calipers (and dare I say it, master cylinders). As you say, riding 11/10ths on track......maybe, on the road......?


Personally speaking, I've ridden both and never really noticed a vast difference. I would have thought the main benefit would derive from the increased rigidity rather than the reduction in unsprung weight. Having said that, my old Guzzi had 35mm fork stanchions (yes, 35mm!!!) and it was still one of the best-handling bikes I've ever had.

 

This brings me onto something else. I need a book. I get most of the basics but often suddenly I’m lost.

Just for an example I’ve underlined the bits above that made me go eh? Which happens a lot.

Radically mounted brake clippers what was the norm before, when did the change happen and am I even certain I know for sure what a radically mounted brake calliper consists of? Nope.

Master cylinders just eh?

35mm that sounds very short, is it short? I don’t know how long are they normally anyway. Im not expecting answers (unless someone’s free) as I said it’s just an example.


So you see I’m needing something to firm up some basic but essentially still wobbly knowledge. Something that starts of in the most basic way but then goes into more depth. Maybe this?

https://www.amazon.co.uk/How-your-motorcycle-works-motorcycles/dp/1845844947

Suggestions welcome.

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Unsprung mass reduction can also make the ride smoother.

By reducing the ratio of unsprung to sprung mass the transfer of inertia from the unsprung mass (wheel, brakes etc)to the sprung mass (bike and rider) will also be reduced.

It's the reason why big heavy cars feel less bumps on the road but small lightweight cars fell all the bumps.

Same for bikes. As bikes get lighter, if the unsprung mass wasnt also reduced the ride would feel harsher.


At last one of my madeyup reasons for why they’re upside down (that I didn’t have the language to explain) is true :D


Thanks for that.

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I’m told upisde down forks are harder to work on because they have no drain screw so can cost more at a garage if there’s a problem, leak faster and in a less obvious way when they go and have the added risk of being next to your brakes if they leak :scratch: hmmm.

Look good though ay!

 

Or maybe problems are rare and when they do occur, in this age of social media the people with problems scream the loudest and so people think a rare problem isn't so rare.

 

True. This came from a mechanics mouth though not the internet. However he could well just be a harbinger of doom.

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I’m told upisde down forks are harder to work on because they have no drain screw so can cost more at a garage if there’s a problem, leak faster and in a less obvious way when they go and have the added risk of being next to your brakes if they leak :scratch: hmmm.

Look good though ay!

 

Or maybe problems are rare and when they do occur, in this age of social media the people with problems scream the loudest and so people think a rare problem isn't so rare.

 

True. This came from a mechanics mouth though not the internet. However he could well just be a harbinger of doom.

Hah. Tell me about one who wasn't. 8-)

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Hi [mention]Slowlycatchymonkey[/mention] Most forks don't have drain screws nowadays, did away with them years ago, and as for Upside Down forks, not new at all, Think one of the First bike's I had with them was the 1989 Kawasaki ZXR250 and that was 30 years ago, and as for ease of working on, not really much difference time wise between them, they both have to come out to change oil etc. :thumb:


As for riding, most bikes are built using the Forks, Manufactures think best suited for that model. All my current bikes run conventional forks. Don't think it hinders them in performance stakes.

But must admit upside downs do look better :thumb:

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[mention]Slowlycatchymonkey[/mention] 35mm is the diameter of the fork sliders not the length. :wink:

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1989 Kawasaki ZXR250 and that was 30 years ago, and

 

I still think of 30 years ago being the 70's :crybaby:

 

I bloody wish it was, I wouldn't feel so knackered, and I would still be riding everyday :thumb:

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