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Trying to decide what to do (if anything) with brakes

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by RGVroomDaddy, Jan 7, 2006.

  1. Hi All,

    I have a couple of technical question relating to brakes … here is a bit of a scenario so hoping I can get some opinions.

    I have a zxr250a which has twin front discs, this is my first bike so I have no point of comparison so am only able to compare the braking effectiveness with that of my car (a 16+ PSI Mazda 323 turbo with custom discs off a VR4 gallant turbo and bendix ultimate pads). So, in comparison to my car the brakes on the zxr suck … especially in terms of needing a lot of braking force on the lever to get a comparable braking effort.

    Question 1:
    Should I expect non power assisted brakes on this bike to have comparable feel to high performance power assisted brakes on a turbo car?

    Question 2:
    If I machine the discs and replaced with better pads** (presumably it just has some stock bargain basement pads from the previous owner) would I expect a significant improvement in braking (at least 20-30% would be nice). ** probably bendix sintered since I can get them for the bike but EBC only make a kevlar organic

    Question 3:
    If I decide to get some sintered pads knowing they will scrub the discs faster, but don’t bother to machine the discs and don’t care if they get scrubbed since they are already grooved, am I likely to get reasonable improvement in braking performance and still get a couple of sets of pads out of them before they hit 3.5mm? (I suspect that the old pads will have worn to match the grooves whereas the new pads might take a while to wear in and could theoretically be worse but I suspect the better frictional material will take care of this with things getting better as they bed in.)

    Question 4:
    On a slightly unrelated note, does anyone know what causes discs to wear unevenly? (Mine are noticeably grooved) I figured it was due to structural irregularity in either the pad or the disc but most likely the disc I guess? Current thickness measures about 3.8mm, minimum is 3.5mm so they are probably ok for a light machine.



    Final Question: :roll:
    I read an older thread https://netrider.net.au/forums/viewtopic.php?t=3798&highlight=ebc+pads
    about braided lines which generally get glowing feedback … what sort of difference do lines make compared with better pads, i.e. stock lines/sintered pads versus braided lines/normal pads and I guess for completeness braided lines/sintered pads. Must admit I am reluctant to spend money on non-consumables for a bike I will probably only keep a bit over a year but don’t mind splashing a bit for good brakes/tyres etc.

    Anyway, lots of questions I know but basically just trying to refine what I have learned from some web and forum crawling!

    Thanks in advance :) ,

    NinjaBaby
     
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  2. I am actually putting the 12 in for braided lines this week coming. I am having some similar probs with stopping. i know its a heavier bike but i am not overly happy with my brakes at the moment either. If you want i will let you know what i think of them. Brake pads will probably make a diference if you go for a softer pad.
     
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  3. My 2c...

    Machine or replace the discs; remove & inspect the callipers; replace the pads; drain, flush, replace and bleed the brake fluid. Use only quality *name brand* consumables.

    Once you have done this see what they are like.

    If they feel "spongey" think about the braided lines (*real* quality ones); these have less flex, so more of the energy you supply goes directly to the pistons/pads.


    If you get this far and you're still not happy you'll need to be a bit more specific, ie. you apply full force to the lever without adequate stopping force being applied, you are finding the wheel locks, the bike is unstable while braking hard, the bike will not repeatedly brake from speed, etc.

    Matt
     
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  4. Thanks for the feedback Matt,

    I have already flushed and bled the brakes but I take it you suggest that you would only replace pads on good discs (i.e. if they were grooved at pad change time you would always machine or replace discs?)

    If this is the case it still begs the question what sort of pads to get. It would kind of suck to get organics and still not like the braking pefromance so I am leaning towards sintered.

    To answer your other questions, it is not a question of fade after repeated application, more a question of feel ... as you suggest I have to really SQUEEZE the lever to get a lock up which is a different experience from good brakes on a car ... but maybe this just goes with the turf on bikes like the zxr250?

    I have also noticed that bike stability is noticably better on rear brakes than front brake application (discovered this in my first Black Spur run today) ... does this offer any further clues?

    Anyway, thanks for advice,

    NinjaBaby
     
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  5. Hey blue12, what sort of pads are you currently running in the 12R?
     
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  6. Sounds like typical Kow-arse-suckshit brakes to me.

    My ZX6R had horrible brakes. The CBR250RR's brakes were far better.
    When I test rode it, I nearly put it into the back of the car in front of me.
    When I applied the brakes I'm thinking to myself, stop stop stop STOP you bastard.......
     
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  7. Mate still has the factory pads. But if this braided line fittment dont make much difference, then i will looking at different pads..
     
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  8. Makes sense. Mine only have a couple of mm left so I will be looking at a pad change soon anyway.
     
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  9. i'd get some better brake pads and see how that goes first

    my front brakes are strong enough to lock up the front, but they do require a lot of force on the lever
     
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  10. i would put that down to weight distribution. i noticed the stiffer i set my suspension, the less i felt it.
     
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  11. I have only had a bit of a play on the front and have it on 65 turns out of 127 maximum stiffness for spring preload (was 75 when i got it but thought it was just too stiff with not much bump damping) and 10 out of 7 maximum hardness for rebound since I like a bit of extra rebound control to stop it bouncing. Haven't adjusted the rear but it is a bit softer than the front.

    Anybody got any other suggestions for suspension settings and especially what effect it has on control under brakes?

    NinjaBaby
     
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  12. you might consider replacing your fork oil just to make sure everything it tip top
     
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  13. Just remeber that if you can lock the front wheel too easily you WILL be on the ground mirco seconds latter especially tipping or just exciting a corner i would call the two points feel and bite the best example off this is if you are riding along at say 100 ks and slam the brakes on as fast as possible the brakes will bite (no feel) and lock the wheel at say 15 psi you then have to release brake and reapply if you kept it upright ? the second example is where still riding along doing the 100 ks and squeeze the brake smoothly and increase the pressure on the lever quickly to a point where the brakes are just off bite you will get say 25-30 psi on the pads.

    reading your earlier post there is no comparison at all between car and bike braking systems . you always must remember that a locked wheel on a bike is deadly even with abs for australia car wheels will lock up to get over the gravel roads issue we do not have to deal with snow and ice on the roads as in europe etc.

    With regard to your question on the rear brake adding to bike stability yes it does help in all regards to strability it will keep the back end in line with the centre line of the stearing head. it will load up the rear suspension stoping the the weight transfer to the front end , changeing the rake and trail on the front end (it gets steeper and reduces trail) allowing better control in all cases

    Braided brake lines will stop the swelling of the original rubber lines and are worth every cent. they add less feel to the feel of the brakes though.
     
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  14. Hey vic brakes on kawasakis apear to be worse than hondas because kwakas go faster :grin: :LOL: :LOL:
     
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  15. If the following are in good condition you should be getting really good braking

    1. Hoses, if you are pulling the level and it is getting really close to the handle bar before you cant pull it any further, your hoses are probably expanding too much and you should consider braided lines.

    If they feel spongy.... You may have some air in the lines, drain them, replace the oil and make sure you dont get air in there.... (Do a search on the net for "bleeding the lines"... it applies to cars aswell so you probably already know).

    Replace the oil anyway, old oil gets saturated with O2.... and you can lose some responsiveness..

    2. Pads, there is a huge difference between cheap pads and decent pads. Get decent ones.

    3. Disks, if your discs do have grooves in them, you may want to machine them, since if you just put new pads on it will simply ruin the new pads straight away.


    4. Check for caliper movement... I have seen cases where the entire front brake units are moving because they are not bolted tight enough to the front forks... Check to make sure your units are not moving because this would cause loss of braking also..





    Just my 2 cents worth....
     
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