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Locking front wheel under moderate braking.

Discussion in 'New Riders and Riding Tips' started by PranK, Sep 10, 2008.

  1. Hi Guys,

    Today I got stuck in pretty bad traffic and was following a massive double tipper truck (that had a whole bunch of anzacs airbrushed on it, it was very cool). I find it hard behind trucks to judge the speed of their slow downs and so I usually leave more of a gap between us. Anyway, as we start merging into the next lane, he slows down fairly swiftly and I do the same, but my front wheel locks and I slide forward, I managed to let the brakes off and re-apply them and regain control of the bike (very nearly dropped it) and the old family jewels were a little tender. But I dont think I applied the brakes any more than I have before... It was a very slight descent. About 15m further down the road was a whole bunch of plaster / gyprock on the road, all smashed up and I thought maybe I had hit a little bit of that.

    Anyway, it scared the bejesus out of me and I dont know if I did something wrong that I could work on not doing again or whether this is a somewhat common occurance and I should leave more of a gap and assume its always going to happen (and therefor keeping it in my mind all the time).


  2. :wink:
  3. Yeah also if you were merging at the time, some of your grip was "spent" turning the corner, leaving less grip available to brake. (apologies to Mr Code). So you may have used the brakes the same amount as you would have when going straight, but in this case they locked up.

    You also may have jerked on the brakes a bit in panic, rather than used the setup and squeeze technique - which will lock up the front wheel MUCH easier.

    Plus it sounds like you were also a bit close to the truck and there may have been schmut on the road to reduce the friction, making the lockup more likely.

    I'd say easy up a bit, leave yourself more room (and a bit more room for ERROR while you are learning), practice setup and squeeze and be aware that grip surfaces vary and so does your braking ability when cornering...
  4. Not that I have masses of riding experience behind me but even in the car I'd leave more room behind a truck simply for the fact that you can see past it so you can't anticipate what the traffic ahead is doing. The first you know about a rapid deceleration is when the back of the truck is suddenly closer... :shock:
  5. Thanks guys.

    I thought I was leaving ample room between us (I am a stickler for the 3 second rule) but it was obviously not enough. It shook me up a little bit, how easy it was to do.

    Morbo28, good call about the merging thing, I was probably definitely using grip to turn and also the tyre would not have been completely facing the direction I was traveling.
  6. It still should not be that easy to "lock-up" the front. This should take a decent fist full of brake - or a reasonable large lean angle if it happens while cornering.

    I'd be checking there is nothing wrong with your front brake to make it catch. Check you're not too low on brake pads and that the calipers are not loose! If your not mechanically minded - its worth getting it checked properly. If it does lock-up on a twisty road, would not be pretty!
  7. Thanks tamarasue, I am mechanically minded, but brakes make me nervous. I'll get my local bike shop to have a look and see if anything is wrong. I check the tyre pressure regularly (and did it last on Monday arvo) so its not likely to have anything to do with that.

  8. i agree with other sentiment that you probably hit some loose surface on the road.

    the only time ive slid the front was on round gravel that was sitting on-top of a bitumen surface. it was like i was on marbles.

    that said, ABS is freakin awesome, but i get it working harder on the back than the front, particularly when combined with downshifting when comming up to lights/roundabouts in the wet.

    as for trucks, i can't stand sitting next to them or behind them and will to just about anything to get past safely (within reason). if i can't get past i leave a massive gap and don't mind if i put a few cars between myself and the truck.

    i've had a hazard sign fly off a semi at speed and lodge itself 1cm into the steel behind of my front bumper in my car (sliced right through the plastic bumper itself, sliced off a 5mm thick aluminium driving light mount). it was basically an airbourne circular saw that could decapitate a rider with ease.

    other than that, gravel/dirt trucks usually drop a regular spray of material out the back which can put some nice cracks in a visor and a good sandblast for the rider/bike. i'd rather not wait for a bump where a large stone gets dislodged from the load and pings me or the bike.
  9. Great post junglist, thanks.

    I was braking no harder than I had done so many times before. The plaster / gyprock on the road further down made me think that maybe there'd been some of that.

    I am super keen on the new Honda CB400 because it has an ABS option. I am all for safety and practicality at this point in my life.

    Oh, and yeah, I have noticed loose things in utes / trucks before and over taken them quicksmart. That sign sounds stupidly deadly. Did the driver know?
  10. Not to be a party-pooper but (and this is coming from someone with an ABS-equipped bike), if you're triggering the ABS in day to day ordinary driving/riding then you're doing something wrong.

    It should be the $1000 accessory you never end up using (except in practice emergency stops), not an excuse not to learn proper braking technique and forget about riding/driving to the conditions.

  11. Oh, I absolutely agree. If for no other reason, it'd be for peace of mind. I'm all for learning the proper way of doing things. I have spent my fair share of time in cars on the track and got my braking sorted out there but bikes are different and I still have a lot of learning to do.

  12. the physics goes to the size of the contact patch. this expands as the weight transfers forward. if you hit the brakes too hard to early you can skid as its still too small. this is why they teach us progressive application of the brakes, ie. start gentle then progessively brake harder.

  13. I know exactly what your sayin, but....

    regarding the back brake ABS comming on, its not due to complete loss of traction, infact the wheel is still on the ground and gripping. the ABS is cycling because of the sensed minute amount of slip/deflection which occurs on any wheel under any high level of braking/cornering/accelerating force. Regardless, the braking in this case isnt being done by the brakes! its the hard intentional downshifting with a foot just resting gently on the rear brake. The ABS sends a light pulse through the foot lever letting you know its there if required in an emergency.

    covering the brakes approaching an intersection - check.
    learning the limitations of my bike (re. limitations of traction through downshifting) in relatively controlled situations so i know what not to do when something unexpected happens - check.

    Yes it has been triggered, but am I doing something wrong? Nope.

    There is a fair bit of emphasis placed on knowing your bike and how it reacts to e-braking and cornering. Whats wrong with learning how each and every system on the bike works? Particularly those that you'll rely on in an emergency.

    Through my practicing I now am confident that if my back wheel hit an unexpected patch of oil I'd be able to recover traction through clutch control, balance and light but effective braking.

    No disrespect intended Spots. I've read many of your posts and respect what you have to say. I think you've either misunderstood me, or have been brainwashed by the 'anti-ABS line' which is parroted so much by riders who just don't quite understand how ABS works. (i'm not saying you dont know how it works, just saying that everyones point of view is susceptible to alteration through constant pressure of oppinion.)

    I've written this response because I don't want people to feel ABS is a waste of $1000 and I do want people to understand how their bikes and safety systems work through safe and controlled practice at low and manageable speeds.

    edit: sorry about being so OT, but i think theres always room for talk about safety.
  14. No, hardly brainwashed at all. I don't have time for the anti-ABS riders who don't understand how ABS works either. :) The misinformation goes both ways, though - ABS must abide by the laws of physics and, of course, can't stop a vehicle any faster than the conditions allow. (Despite all the car advertising which suggests as much)

    Nah, it's cool - and I'm sorry if I came on a bit 'strong' - the post of yours I was responding to seemed to imply that you were tripping ABS in day-to-day riding, rather than as part of braking practice.

    FWIW, I still do my emergency braking drills despite having an ABS bike. Partly to gain (and maintain) faith in the system and get used to the sensation, but mostly to make sure my own braking technique doesn't deteriorate and that I maintain correct posture, etc during the braking maneuver.

    There is experimental evidence to show that in good dry conditions, a well-practiced human braking as if they bike did not have ABS, can out-brake a bike performing a full-ABS stop. With that in mind, I think it's very prudent to continue practicing correct braking technique and ride to the conditions.

    Once again, driver aids are not an excuse to become complacent (or worse - reliant).

    I think we're both on the same page; I just arced up at at an ambiguity. :)
  15. I had a read of every ABS related article I could get my hands/mouse on before making the decision to go ahead with the option.

    Do you have links to any of the articles/reviews that show a significant braking advantage in 'good dry conditions'?

    The ones i read showed a minimal advantage for only the very best and most experienced of riders (something i'm sure very few of us are, no matter how good we think we are) on dry, clean tarmac with a non-ABS bike. As soon as any variables were introduced (manhole cover, grass, sand, water, oil) the ABS outperformed everyone by a very significant amount.

    heres a few links for those interested:



    note that the bmw test was done in 1991 and ABS has improved somewhat since then.
  16. The latter of your two links, junglist. :)

    The wet-conditions-with-manhole-cover tests, incidentally, were what sold me on ABS and why I decided to equip my bike with it. For all the frequent emergency-stop practice I did in the wet, I often found my wet-weather emergency braking effort "lacking confidence", which is ABS's real party piece - ABS gives riders the confidence to brake as hard as they need to in an emergency rather than timidly pussy-footing around at (say) half the possible braking effort for fear of a skid.

    We discussed ABS more in-depth alongside finer emergency braking technique in an older thread, a few months ago. Might dig it up later tonight.
  17. so the BMW test is relatively old (1992). There wernt even many cars about with ABS at that stage.

    since the performance is related to the cycle-rate and ECUs have advanced significantly since then i'd expect current systems to far superior to their 90's cousins.

    i'm just looking for any recent info that shows that ABS is a hindrance in the dry.
  18. That Internet BMW Riders article is a 17 year old articleand as he said - ABS has come a long way since then.

    Here's a more recent study from the US Dept of Transport that compares several bikes with ABS and with the ABS switched off...

    A far more favourable result for the ABS systems which often resulted in better stopping distances in the dry than non-ABS.

    ...Despite being compared to the best
    stopping distances without ABS, the average
    results with ABS provided an overall reduction
    in stopping distance of 5%
    . The stopping
    distance reduction was more significant when
    the motorcycle was loaded (averaging 7%)....

    and in the wet

    ...On the wet surface, the overall average
    stopping performance with ABS improved on
    the best non-ABS stopping distance by 5.0%.

    The stopping distance reduction with ABS was
    more significant when both brakes were
    applied, with an overall improvement averaging
    10.8% over the best stops without ABS. The
    greatest stopping distance reduction with the
    use of ABS was observed when the motorcycle
    was loaded and both brakes were applied,
    averaging a 15.5% improvement over the best
    stops without ABS
  19. Thanks TonyE.

    Of course it all comes down to choice in the end. (while it still exists... )

    complacency with ABS is one of its biggest downfalls, ie: people maintaining smaller gaps than usual because of a heightened belief in braking power. That comes down to perception and shouldnt detract from the benefits of the machinery.

    I tried loading that pdf earlier but it disagreed with my browser. Thanks for the excerpts
  20. Naturally, yes, ABS systems have improved over the years. (And yes, I'd read that MSF paper a year or so ago too. :) )

    I suppose I 'prefer' to use the older BMW article as a pro-ABS reference for the following reasons:
    * The MSF article makes no mention of rider skill/background (a common anti-ABS argument is that the arguer feels they could out-brake the system because they believe they have godlike braking skills).
    * The old BMW article introduces the road irregularity (in the form of a manhole cover) which shows that even their best riders couldn't get remotely near the braking capabilities of the ABS-assisted stops when aa surface irregularity comes into play - the MSF article would appear to have been executed on a skidpan or other high-quality surface.
    * As you say, technology should have greatly improved from the first-gen systems. In that sense, it's conservative.

    I'd love to see a repeat of the old BMW test format (dry/wet/poor-surface, a cross-section of rider backgrounds) using modern bikes, frankly.

    Maybe I'm seeing this wrong, but I feel like I'm being bunched in with the anti-ABS crowd. :? My personal beliefs with ABS should be quite self evident, having bought a motorcycle equipped with the system and continuing to practice emergency maneuvers despite the system.

    I'm definitely "for" the option of ABS. My #1 concern with driver aids is, fundamentally, the risk of improper rider/driver attitude causing risky behaviour, under the assumption that driver aids mean they don't have to drive to the conditions anymore.