Perimeter front brakes 3

[12rich57]

Hello out there,
I have a question about the unsprung weight advantages versus the higher gyroscopic forces generated from a wheel with a rim fitted disc brake.Among some low speed rarely ridden custom Harleys,Buell is the only manufacturer embracing the perimeter braking concept.It's seen nowhere on F1 or mototgp,indeed many Buells that are raced are fitted with conventional dual discs due to warpage,so I'm told.Buell have a reputation for producing a great handling sportsbike,but its hardly a fast one.There is an Italian company producing an ultra trick looking dual perimeter 17"wheel set up but seems yet to be tried and tested anywhere I can find.Is conventional motorcycle braking as good as it needs to be?Are perimeter brakes a mild fad or is it the old cautious manufacturer reacting on a cautious buying public that keep the big four from trying it on their megafast superbikes?Very interested to hear your views 12rich57

 

[MikeHalloran]

I've seen them on small airplanes, where the duty cycle is minimal.

I think perimeter brakes been tried in racing vehicles from time to time, and the result was always the same; melted tire beads. Independent inventors will not be swayed by history.





Mike Halloran
Pembroke Pines, FL, USA

 

[tripleZ]

Without getting into the pros and cons of perimeter brakes, Buell has patents on both the ZTL and the ZTL^2 brake systems, the latter running on the 1125R. That could be a detractor, at least as far as the U.S. market is concerned.

Are conventional brakes as good as they need to be? That's a loaded question. Some folks like ABS on bikes; I prefer conventional systems. With braided SS pads and lines, you have to be careful how much brake you grab at once to keep from pulling a stoppie/endo or tucking the front end or high siding if on the track...same goes for the ZTL systems on Buells. How much you trail brake going into a corner at high speeds depends on speed, position, suspension setup...add the cruiser market into the mix and the dynamic changes. You'd be surprised how many HD/Triumph cruiser riders I know who are deathly afraid of of the front brake.

If you're trying to compare Buells to MotoGP bikes...you really can't in my mind. A 1125R is not going to hold up with a Ducati 1098S on the track (given equal riders). The bikes were designed with different purposes in mind. The braking systems, suspension setup, engine, etc., were then defined to satisfy that design.

 

[12rich57]

Hello again,
Yes I suppose it was a loaded question and in a nutshell it was the pro's and cons of perimeter braking I was after.I certainly wasn't comparing the Buell to any motoGP bike,just why they hadn't made it past Buell.Melted tyre beads being one,thanks Mike.
Cheers guys Richard Roberts,Melbourne Australia

 

[oab]

Giday Richard, I think the main reason that it is not used in sports bikes, is the added gyroscopic effect that the perimeter disc has on the steering response, it inhibits a fast change of direction. It’s the same reason that we don’t use 21” front wheels on sports bikes anymore.
Harvey.

 

[tripleZ]

OK, interesting link if you want to follow the forum's discussion on gyroscopic effect. The synopsis: it's nil with the weight reduction in the disc & caliper combo, and the steep rake angle helps to counteract any lag in steering that might make the bike less than flickable.

http://www.bike-pix.com/forum/viewtopic.php?p=108693&sid=1ea60936697cd1c748217609f357824d

Plus it wasn't written by one of us Buell crazy yanks...=)

 

[12rich57]

Hey guys,
And thanks again for your responses,I just read the article in the link Triple Z,interesting stuff.This is essentially the core of my issue in question.Answer being seems that the added gyroscopic forces aren't felt so much on the road but less unsprung weight is due to the more unpredictable surfaces.Race applications require more agility and heat dispersion,road not so much.Am I close?
Cheers Richard

 

[tripleZ]

Race applications usually have you cycling faster and harder. Some guys will have rainbow colored plates by the end of an endurance race (for WERA fans out there) if they're braking hard enough and long enough. That being said, I don't know that a 20-lap race is going to be enough to fully warp them. It would really depend on your skill level.

When you say they put double discs on, I'm assuming you mean that they're changing from perimeter rotors to conventional rotors? Having used the ZTL system, I know that you'll lift the back-end pretty quickly. Two perimeter rotors would likely have you just "tapping" the brakes to get a decent amount of force.

If you want fads in braking, look at wave rotors.

 

[12rich57]

Triple z,
It certainly isn't modern faddery that interests me,just beneficial technology.Sometimes one gets mistaken for the other.As you may well know in 2000 KTM introduced wave brake rotors on their enduro and mx bikes for scraping and slinging off mud.Not heaps of call for this on a sportsbike if you ask me.They do look groovy though,so to speak.I did actually say 'conventional dual discs'in my original post so yes,this is what I meant.
The reason I'm persisting in all of this is that I'm seriously considering building a trellis framed sportsbike with a Hossack style front end.A supple and responsive front suspension is what I'm trying to achieve and the braking system is obviously a large part of it all.It won't be a track only machine but a street registered naked so pulling up from ultra high speed consistently isn't really its purpose.At the moment it's just a case of gathering as much objective info as I can to work out the best set up for its application.
Thanks again everyone for your thoughts and input. Richard

 

[tripleZ]

If you do ever build this, please be sure to post pics. I don't get to see much in the custom sportbike genre other than POS lowered & chromed Busas which have no appeal to me. Racebike technology is fun for me, but I like looking at custom naked bikes. We have a few guys around here (Wisconsin) that put time into some custom "hooligan" cafe style racers, but they are few and far between.

 

[12rich57]

Triple Z,
Yes indeed few and far between here also.I started the ball rolling in meeting up with various engineers and the like to get ideas on the exact materials to use etc.One particular guy is building a street registered replica of an '83 CB1100 race bike using 954 running gear.Handbuilt frame,tank and swingarm using a japanese reynolds type high tensile steel for the frame,1.6mm wall 30mm O.D.Very sexy piece of engineering,billet triples,rear sets and CNC everything,all done himself.Being stiff and therefore light(thinner wall)this tube was what I also was going to use.Do you have any suggestions?If I could also pick your brain along the way mate it'd be of great help.Will certainly post progress pics. cheers Rich

 

[tripleZ]

Feel free, although I'll warn you that I'm pretty green to the customizing game. I'm more of a jack of all trades...little engine work, little painting, etc. Sounds like a fun project though. Hopefully I'll get to the point where I have the time to start tinkering again.