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blackout

A Single Front Brake Setup?....

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blackout

Do we need dual front discs on our lighter, less powerful bikes?   A single disc setup could be lighter with less unsprung weight and rotating mass and just more simple to maintain.  And done right, brake feel should be spot on.

 

Could the following be the hot setup?

 

A single Brembo M4 monoblock caliper, a 320mm T-drive Brembo rotor (stock are 282mm), and a Brembo radial RSC master cylinder to match.

 

Personally, I could machine a caliper bracket easy from 7075 billet.

 

All thoughts are welcome.  Sound good or do I have heat stroke from too much hot July 4th sun?  lol

 

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mossrider

Medic! 

 

Settle down EBR, just kidding. It's entirely possible i spose, if you need more stuff to do.

 

😎 

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botticelli

Seems like lot and lots of effort for equivalent-ish performance.

 

If your really set on feel adjustment, then an adjustable MC like a brembo RCS19 could be a good starting point, with the stock everything else.

 

This just seems like a lets do-it to do-it project, definitely possible though.

 

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gregjet

Just a note. The stock forks are a bit flexy and the torque reaction from a single side disc will have a twisty effect to some extent. I suspect you are right about the unnecessary nature of 2 discs on the street for a bike of the lightness and lower power.

On the track with heavy braking forces , I suspect you will notice the fork torsion and snap during cornering , of a single disc.

Edited by gregjet
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blackout
3 hours ago, gregjet said:

Just a note. The stock forks are a bit flexy and the torque reaction from a single side disc will have a twisty effect to some extent. I suspect you are right about the unnecessary nature of 2 discs on the street for a bike of the lightness and lower power.

On the track with heavy braking forces , I suspect you will notice the fork torsion and snap during cornering , of a single disc.

With further research, I did come across this issue on some factory single caliper bikes.  The supertwin with the single brake setup, that I saw on lwtracer.com, used Ohlin's universal USD 43mm forks.

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firstyammerha

This set up crossed my mind recently too. Being a solo street rider and past his peg scraping days, I wondered if a larger diameter single disc would work-say 325mm. I didn't research it in depth but thought I could use a couple of spacers to move the remaining one stock caliper out the additional 25mm or so and go to a master cylinder from a bike with one wheel brake. My only bike with this set up was a 2014 Honda CB500F and with my riding style, I never noticed any fork flex from its 41mm front end. Maybe some of the resident racers here have spare discs in these diameters along with calipers laying around who can help us gather any weight saving data.  

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gregjet

Firsty,

You wouldn't notice the torsional flex unless you were looking for it except under extreme braking ( includes avoiding accidents) then either the deflection or the snap back can unseat the wheel from traction.

A single disc should be as close to the centreline of the wheel as possible.

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firstyammerha

I'd still like to see what the parts weigh out of curiosity. 

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gregjet

Actually on this note I just remembered something from my race days.

I raced two bikes that have EXACTLY the same forks and triple clamps ( except the twin had a set of extra brake bosses) , one with a single disc and one with twin discs. Same very tight track and not gigantic speeds ( short).

I raced a VTR250 one year and a cbr250rr the next. VTR has a single and weighed ( track weight) 120kg and the CBR had twins and weighed 155kg. Despite the lower weight and slower top speed. Even with the requirement to brake less to carry the speed more through the corner, you could feel the extra turn in on right hand corners and turn out on left corners on the VTR, so the torsion effect is real.

41mm fork legs so not spider web forks.

Edited by gregjet
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firstyammerha

flex may be a problem at race speeds when you're hammering down a long straight coming into a tight hairpin but in the 40-50 mph everyday city street action that I see, it wouldn't be a problem. Surely someone on the forum has these rotors and calipers lying around .Please enlighten the membership! BTW, my U.S. VTR250 had 35mm fork stanchions so I would expect them to flex at race speeds under hard braking.  

Edited by firstyammerha

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