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Mini disc.. such thing?

Discussion in 'The Garage' started by apox, Jan 19, 2012.

  1. apox

    apox XS650 Addict

    So there is a mini drum... (which I believe is basically like not having a brake but you know) so is there such thing as just a smaller disc?... I mean, if people are slapping on mini drums, a disc 3/4 or 2/3s of stock size can't diminish braking that bad can it?.. What do you all think?


    I did a quick google search, brought up nothing.
  2. apox

    apox XS650 Addict

    the only thing I can seem to find is... it effects the heat created, which makes sense, but can that be over come? .... maybe i shouldn't be talking about this to the world? have I just invented the next best thing? .. hahaha
  3. angus67

    angus67 Welder's penetrate deeper!!

    those cheap ass oreilley's/shucks pit bikes have small rotors. they arent hydralic thogh. mechanical
  4. I have seen a lot of bicycles with mini brake discs lately, but they would never stand up to street MC use. Mini bikes, go karts and commercial lawn equipment all have disc brakes.
    The size of the disc directly effects braking performance. Bigger is better. Look at Buells. Late model XB's had a perimeter disc brake up front. One large disc like that is as effective as dual 320 mm discs and also lighter. Hmmmm, how can I mount that brake set up to my XS ?
  5. [​IMG]

    Something like what's on the front of this? From brat style. You could prob send them an email and ask what it is if this is indeed what you are looking for.
  6. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    look at dirt bike front ends, lots of small disks. A LOT better than no brake. Sure it won't hold up for road racing but should be capable of a hard stop when needed just not 2 or 3 in a row? look at kx250 on fleabay for examples.
  7. RCGRT

    RCGRT XS650 Addict

    Before I swapped to this CBR front end, my brake set up was from a '98 CR125, front and rear, calipers, masters and rotors. Just like you said, it'll stop the bike....but not quite enough for all that weight in the long run...
    This was my front...
    To the OP, I wouldn't really recommend anything much "lighter" than this, unless you really trusted your rear. (I like brakes myself) That thing would get smokin hot! Never did warp too bad however....

    Attached Files:

    Last edited: Jan 20, 2012
  8. retiredgentleman

    retiredgentleman XS650 Guru Top Contributor

    Mini disc or worse yet no front brake....................bad idea!:eek:

    Why would you want to be riding something weighing 600 lbs (bike plus rider), and not have the safety margin of good solid brakes?
  9. RG, most of us do it everyday with the stock brakes on these...hahaha.
  10. 1974jh5

    1974jh5 Curmudgeon.

    About those Buell big brakes: ever seen how hot they get? Every one I see has huge blue, black and brown spots because they have been so damn hot. Think about it: the rotor is going a LOT faster between the pads that far out on the wheel than they are closer in, thus the brakes generate a lot more heat.

    One small brake from a dirt bike won't have nearly enough stopping power for something the size of an XS. Now if you run two, you might be on to something... the stock brake rotors fall between these extremes.

    Something like 70% of your stopping power comes from the front brakes. It makes good sense to me to keep as much up there as you can.
  11. uhhhh....dont big things spin slower.... less rpm.
  12. osteoderm

    osteoderm out of the box

    Setting aside potential safety issues, effective braking, etc., and without getting mired in a thread full of pseudo-science and opinion, I'd guess that a "mini-disc" would be hard to fit simply because the spokes and/or hub flange would be so much closer to the caliper.
    Other than that, it couldn't be worse than the mini-drum front brakes, and certainly better than no front brake at all!.
  13. 1974jh5

    1974jh5 Curmudgeon.

    It's not the RPM, it's the distance traveled. If you have a 20" diameter wheel and you mark a point 1" from the center then another at the rim and give it one turn, both points will go 1 revolution. But the point on the outside will travel a much longer distance in the same time. That's the tradeoff; a larger diameter rotor gives the caliper a longer 'lever' to work with but the rotor moves much faster through the caliper. It's a balancing act.
  14. retiredgentleman

    retiredgentleman XS650 Guru Top Contributor

    I don't know about your TX650, but my 78 SE disk brakes, front and rear, have worked quite well the last 5 years. As a matter of fact, they saved me from T-boning a deer last summer. The deer cut right in front of me and by using emergency hard braking (using both brakes), I just hit the deer's back leg as it flew past.

    However, I'm still working on improving my brakes. I have just made up some adapter plates for Brembo 4 piston calipers, which will soon be installed on the bike.
  15. apox

    apox XS650 Addict

    all great input thanks guys, one thing I will say though is, these stock bikes and brakes are meant to hit safety regulations, you could have some 300lb dude riding a stock bike who knows right?... I'm 160lbs, and when the bike is done, it'll have probably shed 50-75lbs easy, that must amount to something. Especially since in my mind, I only need to be able to brake as good as a brand new small car, any faster and you will most definitely get raped in the behind by the car following you. I'm not trying to prioritize looks over safety, but if I can show a little more spoke up front and it's still absolutely safe then i'm all in!
  16. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    I thought that's where you are, but you are going to compromise, goin' down in size.
    As long as you understand what you are getting.... Lots of big cruisers have marginal front brakes for the size of the bike, like you say specially if Mr AND Mrs hogger are on board with two weeks worth of gear. On the other hand a lot of riders wouldn't know what to do with the stopping power of the typical crotch rocket and would probably go straight off the front of the bike. Kinda like this...

    Oh there is no such thing as absolute safety on a motorcycle!
  17. Hey now whenever I wrecked I knew the capability of my front brake... Just didn't have a choice! :thumbsup:

  18. arcticXS

    arcticXS XS650 Guru Top Contributor

    I am sure there are smaller brakes out there that are better than the OEM brakes.

    On my -77 European model, the twin discs with the single piston calipers were close to worthless.. The older models with the 2-piston calipers and 2-piece single disc may be better. My old RD has that type of brake setup, and stops twice as hard as my XS. Obviously, the RD is a lot lighter, but still...

    Also, I believe the stock XS discs are of a low friction stainless type of alloy, rather unsuitable for the purpose.
    A cast iron or carbon steeldisc, combined with EBC HH pads, you will givea lot better bite and feel in your brakes, especially combined with an optimal size master cylinder and braided hose(s)

    To me, it is also unclear what you want to achieve, is it a different look, or lighter weight, or both?

    There are almost endless options, from twin 320 mm discs with 4 or 6-piston calipers, this would still be vastly lighter thans stock twin discs, and maybe 300% more brake power. At the other end of the spectrum, some Swedish builders have made tiny discs concealed as a small (5-6" OD) drums, with the caliper sort of integrated in the "brake plate".

    Whatever you decide to go for, stay away from lazer cut stainless discs, instead go for cast iron Brembo, ISR, PVM, Beringer, BrakeTech, or other quality brands. I would stay away from a Chinese made brake as if it was Ebola!
  19. arcticXS

    arcticXS XS650 Guru Top Contributor

    I just looked up ISR's front hub with twin 260 mm discs. Total weight of complete assembly is 3.6 kg (8 lbs). Check it out here:

    I am 100% convince that these will outbrake stock twin disc setup by a huge margin!

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