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brakes

926 views 11 replies 6 participants last post by  princeallure 
#1 ·
Can somoene enlighten me bout brakes? some bike companies brag about radial mounted front brakes.. whats the diff they look like thier all in the same places
 
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#2 ·
For racing purposes, when you're talking about super rigid frames, aftermarket triple trees and exceedingly heavy duty Ohlins forks, the radial (ie,in the same plane as the wheel spokes) brake bolts and massive fork bottom mountings allow for higher mechanical advantage and less flex. As well, the pads are kept truer to the rotor than with conventional perpendicular brake mountings.

That said, you'll notice quite a difference between the mass produced radial brakes and the ones found on the GP and WSB circuits. For one thing, to save weight, the rotors have shrunk in diameter and the mounting bosses are very slim compared to the latest racing favourite. There would be no point in mimicking the size etc of the racing ones, since a stock bikes triple clamps, forks and frame aren't really up to the increase in torque that would occur.

My _opinion_ is that radial calipers will bring street bikes onto a level playing field versus Yamaha's R1 type monobloc calipers. Essentially stopping the 'clamshelling' effect that occurs with eg 6 piston Tokicos. All that said, most street riders don't get full use out of their front brakes anyway, without lots of specific practice.

While no doubt an improvement in some cases, in the main, its marketing. For example, the hottest stock brake setup on the street right now is probably the CBR954, but that is mainly due to the increased lever effect of the larger than 'normal' 330mm rotors, rather than the rather ubiquitous 4 piston, bolted together Nissin calipers.

I'd guess that radial mounts will 'trickle' throughout that model lines of all the manufacturers if their marketing departments sense either a sales advantage or just to keep up with the competition. Like EFI, they'll no doubt improve with the years.

The only impressive radial mount system that I've seen for the street (so far) is on the 2003 Aprilia Mille R. But that's so out of the realm of reality $$$-wise that it might as well be aftermarket.

:rider
 
#3 ·
I've been curious to know if it is actually the case that the 2-piece calipers do actually flex when in use or is this purely a theoretical concern? I've heard of people trying to measure flex on their calipers (2-piece) and finding none... backyard style. Maybe yamaha's one-piece is also marketing to look cool with the anodized plugs (one of my reasons for the "upgrade")?

Seperate from that though, i agree on the issue of lever feel being equated to ideas of having "better" or "worse" brakes.... I switched to a 14mm as oposed to the larger, stock 5/8inch diameter master cylinder on my bike, and damn what a difference for the better. In reality the brakes aren't doing anything differently, but damn do i love the increased travel. Previously my brakes were like an on-off switch, but now it's gradual, and for me, much easier to control depending on riding.
 
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#4 ·
Lugan said:
I've been curious to know if it is actually the case that the 2-piece calipers do actually flex when in use or is this purely a theoretical concern? I've heard of people trying to measure flex on their calipers (2-piece) and finding none... backyard style. Maybe yamaha's one-piece is also marketing to look cool with the anodized plugs (one of my reasons for the "upgrade")?

Seperate from that though, i agree on the issue of lever feel being equated to ideas of having "better" or "worse" brakes.... I switched to a 14mm as oposed to the larger, stock 5/8inch diameter master cylinder on my bike, and damn what a difference for the better. In reality the brakes aren't doing anything differently, but damn do i love the increased travel. Previously my brakes were like an on-off switch, but now it's gradual, and for me, much easier to control depending on riding.
Yeah, its really impossible to test for in a static situation, since the rotor isn't moving, you cannot generate the same torque. Kinda like leaning the bike over when at a standstill to see what angle the footpegs would touch down at when you aren't replicating the suspension being compressed.

I agree that feedback is number one. If you don't have a good feel for what is going on, how can you brake with confidence? Hell, even if a bike has fabulous brakes, if you don't change the fluid regularly, you're just putting the water on for tea :D !!

I only mention the Yamaha ones based on the brake tests where the journos are doing multiple bikes at the same time. Yamaha generates superior braking with less rotor diameter and somewhat smaller calipers, leaving me with the idea that, like true racing calipers, monobloc makes a diff under extreme conditions.

The old story applies though, a better rider with poor brakes....

:rider
 
#5 ·
The calipers are all designed to have a U shape to fit around the rotors. So it's inevitable that they DO flex. How MUCH they flex is the issue.

It's like the display that was at some past World Exposition. It was a length of 24 x 12 x approx. 8 feet long I beam set on two end supports. A sensitive dial guage was set up in the center to measure the give when delicate 90 lb women would push on the center of the beam. They push and the dial moved. Then they all turned to their SO's and smiled at how they were able to bend such a large steel beam. Of course the dial guage was a special lab unit that was measuring fractions of a thousandth of an inch. The point is that metal DOES flex when force is applied. Even large 30 foot bed metal lathes need to be supported at numerous points along the bed or the massive cast iron bedways will sag under their own weight and ruin the accuracy of the machine.

So if Yamaha's monobloc is better it may or may not be because of the caliper design. So many things enter into how the brakes feel and perform I don't think it's fair to chalk it up to one design element.
 
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#6 ·
TeeTee said:
The calipers are all designed to have a U shape to fit around the rotors. So it's inevitable that they DO flex. How MUCH they flex is the issue.

It's like the display that was at some past World Exposition. It was a length of 24 x 12 x approx. 8 feet long I beam set on two end supports. A sensitive dial guage was set up in the center to measure the give when delicate 90 lb women would push on the center of the beam. They push and the dial moved. Then they all turned to their SO's and smiled at how they were able to bend such a large steel beam. Of course the dial guage was a special lab unit that was measuring fractions of a thousandth of an inch. The point is that metal DOES flex when force is applied. Even large 30 foot bed metal lathes need to be supported at numerous points along the bed or the massive cast iron bedways will sag under their own weight and ruin the accuracy of the machine.

So if Yamaha's monobloc is better it may or may not be because of the caliper design. So many things enter into how the brakes feel and perform I don't think it's fair to chalk it up to one design element.
Yes, I agree with you there. It just _seems_ by a process of elimination that the monobloc in mass production may see the same benefits as in racing, ie Brembo's monoblocs. However, by surfing through various racing forums I hear high praise on one of Bremboes bolted calipers that has a separate pad for each piston, supposedly to allow greater feedback and braking power.

I'm again guessing, but I imagine that the racing engineers will reach a limit where the relative rigidity of the braking system runs quickly into diminishing returns, in the same manner as frame stiffness and compression ratio.

For street purposes, I doubt that there is a sportbike out there with what could be construed as a poor system. As well, I'd imagine one person's optimum would be another's nightmare.

For example, I've always been a four finger braker and like instant on breaks, hard pull from the get-go, letting my hands/fingers do the modulation. I know a lot of folks like the two fingered approach and seem to handle their machines admirably.
So like most things on two wheels, tuning for the individual is as much an art form as a science :).

:rider :thumbup
 
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#8 ·
VTwinVince said:
Having ridden a Yamaha with the Sumitomo monoblocs with braided lines, I can tell you that Nissins with the same lines absolutely do not compare on the VTR.
Yeah, which I think lends credence to the 929/954 having such powerful braking, the only major diff from the VTR being 330mm rotors.

:rider
 
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