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Discussion Starter · #1 ·
Hayes makes two adapters for 51 mm to mount 8" rotors. I am wanting to put this on a 2004 MX pro with QR. They have two adapters for 51, one labeled as a QR/20 mm and one as 20 mm. Will either work? I can't tell if there is any difference between the adapters with part number 74-30 or 74-25. If I was buying the new one I would get the QR designated but a buddy has a spare 74-25 (20 mm) that I would like to use.
 
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Discussion Starter · #3 ·
If I wanted to try this before upgrading would either adapter fit? Thanks for the reply.
 

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Registered
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192 Posts
Sorry..

Can't help.

Some of the things that could happen: fork lowers break, hub comes out of dropout. Either of these will get ugly fast.

An 8" rotor can generate 30% more power than a 6"

It might be easier to test ride your buddies bike or test ride one at a shop to get a feel for the difference.

Randy
Looking out for your health.
 

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Meh.
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17,508 Posts
As Randy mentioned, it is not recommended.

The 20mm thru-axle adapter is thicker than the QR adapter, since the hub spacing is different. To make it fit on a QR fork, you will have to modify it. A QR adapter can be used on a 20mm fork with a spacer between the adapter and the disc tabs.

That said, it is still not a great idea to put 203mm rotors on a fork that is not rated for them.
 
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Discussion Starter · #6 ·
Just the info I was looking for, thanks. I think I will hold off, you guys made me sufficiently nervous.
 
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