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Offline Rick

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Went for MOT test yesterday and the examiner failed it as the rear wheel did not lock up. Explained combined ABS system would prevent wheel locking roller but he was having none of it. I see that in Haynes mentions 'A sensor on each wheel is linked to a modulator unit that determines if a wheel is about to lock up, and if so releases and pulses brake pressure via the modulator until there is no danger of wheel lock'.  Your experiences would be appreciated ?
« Last Edit: 26 June, 2020, 09:13:20 PM by Rick »

Offline maxstu

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Re: 2009 Mk 1 abs, Should the rear wheel lock up whilst on MOT Roller
« Reply #1 on: 26 June, 2020, 09:29:33 PM »
Not sure about this one. MOT tester trying to lock up rear brake? Never seen any tester do that in 42 years of motorcycle ownership.
How does that show effectiveness of brake? Surely its only got to meet a set resistance show on the large LED readout screen?to pass without locking up?
« Last Edit: 26 June, 2020, 09:30:40 PM by maxstu »

Offline Rick

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Re: 2009 Mk 1 abs, Should the rear wheel lock up whilst on MOT Roller
« Reply #2 on: 26 June, 2020, 09:40:06 PM »
Thanks Maxstu, I've owned this bike for seven years and never had a problem before and passed without any issues, unfortunately used this new garage to me, as usual chap off work due to Covid. I explained that I had never seen the wheel lock roller on previous tests, just went by reading as you say. 

Offline jm2

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Re: 2009 Mk 1 abs, Should the rear wheel lock up whilst on MOT Roller
« Reply #3 on: 26 June, 2020, 09:50:22 PM »
Yes. The test (now, for a while) is to lock it.

The trick is to put the final bit on slowly so it registers the most (before locking) - whilst squirming on thr roller !
Gone are the big round dials.


Only do it right - no bodging please.   Keeper of the failed stator list.   John.

Offline maxstu

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Re: 2009 Mk 1 abs, Should the rear wheel lock up whilst on MOT Roller
« Reply #4 on: 26 June, 2020, 09:53:33 PM »
Tough call, Rick. I would phone the test station and discuss your concerns. And ask how one remedies such an issue to get a pass? Or ask the views of another MOT station? BTW all tests guidelines are online for public to read too...
 

Offline maxstu

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Re: 2009 Mk 1 abs, Should the rear wheel lock up whilst on MOT Roller
« Reply #5 on: 26 June, 2020, 09:58:44 PM »



Well l stand corrected  :003:

Sit on the motorcycle and locate the front wheel in the rollers of the brake tester, ensuring that the motorcycle is lined up in the straight ahead position and settled in the rollers.

Make sure that the roller brake tester is set to rotate in the correct direction so that the motorcycle wheel will rotate forward.

Start the rollers and allow the front wheel to stabilise. With the rear wheel brake fully applied (unless it’s a linked system), gradually apply the front brake until maximum effort is achieved or the wheel locks and slips on the rollers.

Record the reading at which the maximum braking effort is achieved and release the brake.

Restart the rollers if necessary and gradually increase the front brake effort to about half the maximum reading and observe the way it builds up. Hold steady and check for fluctuations. Release the brake and observe the way in which the braking effort reduces.

In the case of linked systems, repeat the steps 1 to 5 for each control operating the front wheel brake. However, some linked systems are designed to only work above 10km/h and will not work in a roller brake tester.

Repeat the procedure for the rear wheel brake and any sidecar brake fitted.


Offline Rick

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Re: 2009 Mk 1 abs, Should the rear wheel lock up whilst on MOT Roller
« Reply #6 on: 26 June, 2020, 10:07:39 PM »
Thanks JM2, but surely the abs system is trying to prevent a lockup, maximum braking takes place just before a wheel locks, that's where abs braking comes in, by applying cadence type braking many times faster than could ever be achieved manually.

Offline Rick

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Re: 2009 Mk 1 abs, Should the rear wheel lock up whilst on MOT Roller
« Reply #7 on: 26 June, 2020, 10:29:13 PM »
Thx Maxstu, the very much more powerful front brakes did jump out of the rollers, however the rear wheel didn't. The rear brakes seems to stop the bike within a reasonable distance, obviously with the linked system some front braking is applied at the same time.
 The whole point is to get good braking not just the rear wheel locked and skidding in sliding friction.

If I had applied the front brake as well as the rear pedal, whilst the rear wheel only was in the rollers the centre piston would have come in and given the full rear brake reading. But I didn't do this and just used the pedal, the combined system seemed to cause an unwelcome complication for the tester 
« Last Edit: 26 June, 2020, 10:47:32 PM by Rick »

Offline TerryR

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Re: 2009 Mk 1 abs, Should the rear wheel lock up whilst on MOT Roller
« Reply #8 on: 27 June, 2020, 06:59:16 AM »
There is no centre piston on the rear brake and the front brake lever has no effect whatsoever on the rear brake.
There is a centre piston on the front brakes and it is operated by the rear brake pedal.

Offline Rick

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Re: 2009 Mk 1 abs, Should the rear wheel lock up whilst on MOT Roller
« Reply #9 on: 27 June, 2020, 08:57:11 AM »
Thanks TerryR, Although my bike has got 3 pistons on the triple rear brake caliper, same as the front,  I was wrong in  my understanding that the front is linked to the rear in the same way that the rear is linked to the front. How could it be! there is only one brake fluid supply line to the rear caliper. Just shows benefit of discussion.
I would appreciate more feedback on original post about experience of others at MOT test and if rear wheel locks when carrying out roller test on abs models.
« Last Edit: 27 June, 2020, 09:04:02 AM by Rick »

 


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