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trail braking; front rear or both?

Discussion in 'Racing, Motorsports, and Track Days' at netrider.net.au started by abvc, Sep 4, 2007.

  1. i think trail braking is always an interesting topic. it requires guts, judgement, reflex, which falls into 'skill' category and essential skill for a racer or serious rider.
    tips & tricks ??


     
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  2. I'll use both, but with an opposite bias to usual - very light with the front, more with the rear.
     
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  3. hm, light as in the amount you press or the grip-amount of either brake apply..?
     
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  4. I almost never touch the rear unless it's needed to settle the power delivery from the motor when cracking the throttle mid-corner. Other than that, I barely touch it.

    I believe in trail braking into a corner because it settles the suspension better.

    - When you brake with the front there's a forwards weight bias, and compresses the front, and unloads the rear
    - When you release the brake, the weight of the bike wants to center again and will unload the front and compress the rear
    - When you throw the bike onto its side, weight wants to come off the springs as its transitions (unloads front & rear), and then settles back onto the springs as the bike starts to track around the corner (loads front and rear)
    - When you crack the throttle, weight moves to the rear (unloads front and loads rear)

    If you come up to a corner in the classic brake, release, turn-in, throttle the bike will do the following:

    Front: load (braking), unload to static (brake release), unload (transition), load (settle), unload (throttle)
    Rear: unload (braking), load to static (brake release), unload (transition), load (settle), load more (throttle)

    As you can see, there's a lot of rocking and pogo-ing going on.

    By carefully trail braking that can be managed more smoothly:

    Front: loaded (braking), stays loaded (braking while turning in), stays loaded (slowly releasing braking pressure as it settles), slowly transitions to static load (continue releasing braking pressure after settling), unloads (throttle on)
    Rear: unloaded (braking), stays unloaded (braking while turning in), slowly loads up to static (settling phase but controlled with the slow front brake release), loads up (rate of load can be controlled by tweaking rear brake as throttle is cracked)

    As you can see, if you manage it right, it all becomes one smooth transition from a front-bias loading to a rear bias loading, but the rate at which this occurs is managed by the act of trail braking the front, and a gentle application of the rear brake if needed. The rear brake is not really needed if the engine progresses to a power-on in a smooth enough fashion, but some fuel-injected bikes are a little "snappy" once the throttle is cracked and the rear brake can be used to tame this.

    Just my 2c.
     
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  5. You speaka de english?

    Gentle with the front when the bike's leaned over. You can use more rear as long as you've got the throttle on a touch.
     
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  6. Stew, using the rear brake can stop all the weight going forward as you brake going in. I can also help tighten a line without getting off the gas. Then again, you're shiteloads faster than I am, maybe I'll yank me pedal!
     
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  7. I use a shit load of front coming into sharp point and shoot style turns where corner speed doesnt matter so much as how quickly you can get to the apex. I still use a reasonable amount on sweepers, but not nearly as much. Most of my un-saveable front end washouts have been from the first kind of corner for me, so it's certainly something to be careful with.

    The rear, while I know I SHOULD be using it to tighten my turns, I dont use. I'll get there though.
     
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  8. Meh, I just turn the bike in harder or drop my weight off to the inside a little further. That tightens the line just fine without messing about with the rear brake. :twisted:
     
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  9. Couple of points - and these points are from the point of view of how you're riding and what you're trying to achieve:

    * If you set your speed well before the corner, you don't need to trail brake.

    * If you're setting up for the corner and weight shifting a lot, how the hell to you trail brake with the rear??

    * Trail braking can ensure smooth transfer of forces through a corner, but consider that you now enter a new world of finesse when asking available tyre traction to turn you AND slow you down at the same time. It's not newb technique. You could easily ask for more traction than is available.


    Background:
    In the first point, you've finished your braking well before the corner and can now focus on the line and throttle. Trail braking blurs that clear distinction between braking and cornering by continuing your braking into the corner, getting the speed down to the "right" speed but tapering off the braking pressure the more you're in the corner. It means you can carry your straight speed for longer because now you're using some of the corner for braking. Great track technique. I personally try not to play with it too much on the open road.


    Ok, naturally all this is bike dependent - I used to use rear brake on my GPX250 to get the thing to squat a bit - but then I wasn't shifting weight off the bike. I now know that throttle control would have been a better way to go.

    The regulars will know that talking about using rear brake in cornering - just gets my goose bumps running because it's so easy to mess up.

    I'm not going to bite much more than this though since I think I've already spent column miles on the topic/pitfalls/possible negatives of rear brake use in corners already!!! Anyone who's interested can search on my user knick and "rear brake".




    Did someone say rear brake for tightening lines... no, I'm not going to bite... nuh uh... :-# [+10000000 Flux on that point]



    There is one truth though about rear brake - there IS less attitude change in the bike when rear is used compared to front for the same decelleration. Mind you, you'll never get the decelleration out of the rear that you can get out of the front.

    Ok, shutting up now :-#
     
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  10. Rob, I took the meaning of this thread, being posted in "Racing & Track Days", as opposed to "New Riders", to mean that abvc was after the more advanced techniques for trail braking into corners at speed at the track. Definitely not something for the newbs to be trying, but I didn't think that abvc was asking to be treated like a newb.
     
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  11. Any serious trail braking is track (or nutter road riding) territory and consequently I don't think braking early and setting up early is really an option. We're talking about not only getting from point A to point B quickly, but doing it in a manner where no bugger can get past you. You can have a perfect setup and great corner speed, but not much good after someone has stuffed it up the inside of you hard on the brakes and ruined your line and speed.

    I realise I didnt give any tips which was the OP goal....

    This coming from a complete amateur remember so take from it what you will....
    *Be comfortable (as possible) with having a loose front end through normal cornering. Easier to save than the sudden washouts I have experienced with too much trail braking, and I believe that familiarity with losing front end grip helps.
    *Your corner speed and general riding is ruined if you're trying to do too much at once. Unless you're very familiar with the track or road, just concentrate on nothing but corner speed and then introduce braking hard into the corner later on. Maybe even do a session every time you go for a ride with no hard acceleration and no hard braking just to get into your groove again.
    *Take it easy, but don't pussy foot around too long or you get stuck in a rut and find it more difficult to go out of your comfort zone.
    *Practice on a bike that is inexpensive to crash, as I've certainly had a few.

    What do books like Twist of the Wrist etc have to say on the matter??? I've gotta admit I haven't read any riding manuals... :oops:
     
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  12. Is this a touchpoint of yours Rob? :grin:

    For me it's all about feeling comfortable, which has a lot to do with getting weight off the front end. If things are getting hairy, a bit of rear brake seems to help re-balance the bike and make me more comfortable.

    Perhaps it's a habit I've picked up from slow speed circles etc, but throttle against rear brake can help drop a bit of corner speed and radius without loading the front or risking a slide. Keep the throttle open and it's not going to lock up, not even close.

    I've done a few emergency braking while cornering exercises that have taught me there's usually a fair bit of braking still available to you from both ends even at a 6- or 7-tenths cornering speed, but you definately want to manage your weight transfer as much as possible so you don't overload the forks... And that's back brake territory right there!
     
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  13. Everytime I think of where serious trail-braking is applied, the rear wheel isn't really on the deck to provide any real braking assistance. Touching the rear brake here just makes the rear end hop and skip around more, and offers the potential danger of stalling the engine, which will unsettle the bike more when the engine fires back into life when the rear touches down again.

    Best practiced at the track of course. My favorite corner for doing it is going into Turn 4 (Honda) at PI, where if you get it right the rear will be skipping along 'cos it has so little weight on it, effectively being a rolling 0-2cm high rear wheel stoppie, as you brake down from ~220kph to ~100kph or so (I'm guessing here) before tipping it in and continuing braking (while slowly releasing the lever) right up to around one third of the way through the corner (travelling at around 65-70kph by now at a guess) and we're at full lean, and then slowly standing the bike up and winding throttle on, well before clipping the inside ripple strip apex.

    Going into MG (Turn 10) is a similar deal.

    In short, the rear brake doesn't do too much if the rear wheel isn't on the deck.

    Twist of the Wrist never talks about trail braking. In fact, Keith Code generally advises against it, but Code isn't really running a racing school.
     
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  14. Just being cautious is all. :)


    Still I'd love to know, if advanced cornering involves hanging off/shifting weight off seat, locking on, leaning upper body, head position etc etc, how can you trail brake with the rear? :-k Isn't your foot poorly positioned to do that?

    If going down hill through twisties, mostly coasting, then there's probably a good case for rear brake...
     
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  15. The majority of my riding is on regular roads, and prior to having a bike with "linked" brakes, If I did use trail braking, I was on the fronts alot more than the rear. (although I did use the rears just a little at the same time)

    For regular road riding, trail braking could perhaps require even more finesse and skill, since the weight/balance of the bike, that you just got sorted for the corner can be upset by mid-corner bumps etc...and since this is a skill that CAN put you on the limits of traction, that mid corner bump can bring you undone.
    On the track, I found that I could trail brake if necessary, with complete confidence almost to the limits of traction...and I enjoyed that freedom.

    Trail braking was never something I decided to do...it just seemed to be a part of my own general style, so I became fairly comfortable with it over the years.

    Until recently and due to recently poor riding technique I found I HAD to trail brake because I was rushing into corners too hard...Now I am trying to moderate my entry speeds by braking earlier and then stabilizing with the throttle...only using the brakes a little to stabilize things if I still get it a bit wrong.

    I see trail braking as a very advanced skill, to be used as a tool for cornering, not as the "way to corner" all the time, necessarily.

    That's just my own impressions from my own experience to date.
     
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  16. Rearsets Rob.
     
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  17. Really???? You joshin me? Weight support or peg loading to help lock in against the tank AND enough dexterity to apply fine rear brake???? :-k
     
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  18. You're thinking about your road bike and how the pedals and pegs are positioned. With rearsets you can move them around for exactly that reason. But I know Stew has huge feet, that's how he does it!
     
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  19. No, I'm thinking about rear sets and trailing rear brake going into a corner while hanging off. I still can't see it. :? Maybe possibly in a left hander, but on a right hander????? Maybe it doesn't matter.


    :LOL: Is it true what they say about big feet??? :LOL:

    Um anyway, Stew clearly said he doesnt trail brake with the rear. He uses it on the way out - sometimes. From the logistics point of view, that makes sense coz on the way out you change your body position.

    Meh.
     
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  20. I dunno mate, I'm so focused on not crashing, all these advanced techniques I'll leave till a track day and some quality time on the circuit. Hang on, that's this Friday. Yay!
     
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