8" rotor in a Psylo sl (standard)

[IFO]

my info comes direct from the brake and fork manu's....

its not some weird tech thing i dreamed up...

feel free to contact any hydro brake maker and any fork maker...

pose teh question in well worded statements and see what they say...

i posed those same questions to several compaines over a year ago, and got back the info i included...

specifacally, i contacted FOX (forx), and Hayes (hydros), and Zokie (fork)....

and in June im guna be all over Whistler... page me, i'll be on A-line, ahahahahaahah

[joshua]

You will have no problem running a 8" rotor.  I havn't heard of any wheel coming off becuase they have a standard axle.  I think you will enjoy the bigger rotor anyways.  I have seen pictures in mt bike magazines showing guys from bike companies running 8 inch rotors on standard axles.  I don't think they would be showing pictures like that if they were unsafe.  

[GET]

I just want to be sure you understand my request.  I absolutely meant no contradiction to you.  I have high regard for your opinions in these matters.  As an engineer, I always want to get input from all sources.  That's just the way engineers are.  I did look into info at Magura, Avid, and RS.  I got no information against mixing 8" discs with "standard" hubs.  Thanks for your reply.  I'll look into the other sources.  I think I will try to get up to Whistler if at all possible.  It sounds phenomenal!

[slowride]

Hayes won't sell you an adaptor to run their 8 inch rotor on a standard QR dropout anymore, because of the possibility of ripping the wheel out of the dropout. This is not to say that you can't find the apator anywhere, but respectable bike shops (anyone dealing with QBP directly) won't sell you that part.

That says something to me...

[GET]

I gave this issue some thought from the point of view of a manufacturer and I can see why they might have a problem.



As a matter of fact:  there is at most 30 to 40% more braking torque for an 8" versus a 6" disc.  There are other factors that have at least this much variance between individual applications.  My XTR brake levers increase mechanical advantage by more than this, for example.



So the problem is probably not engineering.  The problem is demograghics.  What type of rider is likely to need to add 8" rotors to their bike?  Statistically, a high percentage of riders venturing into downhill or other extreme applications.  These riders should have heavy axles anyway, as I mentioned earlier.  From a liability/reputation point of view, I can see why the manufacturers might be concerned.



BTW, putting 8" adapters on the standard IS tabs of a front fork does significantly change and increase the loading of these tabs.  That is another issue.

[jimbo]

I emailed the various manufacturers and this is what they said:


Avid:

"That question should be directed to your fork manufacturer. I will warn you that many manufacturers draw the line at 185mm for a standard QR.

Thanks,
Dan"



Hayes:

"It is only recommended that you use the 6" disc with a fork with standard quick release.  The 8" disc has about 40% more power, and will add more stress to the fork legs.

Sincerely,

Scott


SRAM:

"An 8 inch rotor is fine for a Psylo.  It works better on a through axle (less lateral flex in the system but can be used on a standard dropout.

Chris McKenney,

SRAM Dealer Service Representative"


Manitou:  

"The only single crown fork that is compatible with an

8" rotor is the Sherman or Dorado SC.  

Thank you,  

Jon Agnew

Answer Products"  

I asked Jon if this also meant the standard dropout version of the Sherman and he said yes.   He also said the use of an 8 inch rotor on a fork other than what's approved will void the warranty.



Marzocchi have not answered yet.  I'll post them if they answer.  It might be like those Lawyer Lips things.  The real answer might come out in a lawsuit.  

[IFO]

either way, the makers of the product know alot more about their gear then i do...

so when they say dont do it, i'd listen...

thx for the update...

[joshua]

I was just at the vancouver outdoor adventure show this past weekend.  I really don't have an opinion on this subject, but I did see a few bikes with 8" rotors on standard forks and they were new bikes that were for show from bc companies.  And for the emails, they really don't say anything about ripping the wheel out of the drop out.  It just talks about the flex.