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Offline Greenfingers

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Weak rear brake
« on: 20 February, 2020, 06:18:00 PM »
Bought my CBF1000 A6 a couple of weeks ago. Really pleased to have found one with a well documented history that I think looks as mint as could be expected for a 31k miler.

I've only ridden it a few miles on one outing so far and the mechanicals seemed good, plus all electrics working. I was being cautious, having not ridden for about 10 years, but it did feel slightly odd trying to hold a line on sweeping bends as it felt like the bike wanted sit up rather than follow through the bend. Also, I thought the rear brake was hopeless.

When I got home I checked the tyre pressures and lo and behold, the rear tyre only had 17psi it, which I hope explained the strange handling!

I've read up a bit on here about the braking system to try and understand how the linked brakes work and came across a few comments about the rear brake being less than sharp. My pedal isn't soft or anything, but there just doesn't seem to be much bite when applying normal force. I have cleaned the disc with brake cleaner and the caliper seems to function as it should if I spin the wheel and push the pedal by hand with the bike on it's centre stand. The pads measure 5mm thick and the previous owner did say something about changing pads, so is it possible that the pads are not bedded in properly yet? The disc doesn't look too worn with hardly a lip near the outer edge, but it isn't perfectly flat and you can feel a couple of waves over the surface.

It's booked in for an MOT tomorrow and I suppose I'm looking for some reassurance or advice from anyone with experience of this.

Offline Crispy

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Re: Weak rear brake
« Reply #1 on: 20 February, 2020, 08:05:17 PM »
Back brakes aren’t very good on all bikes, I think they’re only meant to be used for slow speed manoeuvring, and certainly never on corners. Does it feel spongy, maybe the brakes need bleeding?
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Offline Shed

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Re: Weak rear brake
« Reply #2 on: 20 February, 2020, 08:38:30 PM »
As Crispy says, the back brake isn't exactly awesome and never will be. Try some EBC pads for a little extra bite.

If you want to bleed the brakes, you can get a litre of DOT4 brake fluid from Euro Car Parts for around £6.00 - this is enough fluid to replace the entire brake system, and also bleed the clutch too.

https://www.eurocarparts.com/p/pagid-dot4-brake-fluid-500ml-524770271

https://www.ebay.co.uk/itm/EBC-FA388HH-Sintered-Front-Rear-Brake-Pads-Honda-CBF1000-A-S-T-FA-ABS-06-16/223179323025?epid=4034589070&hash=item33f6863691%3Ag%3Al44AAOSwHctbufqr&LH_BIN=1


Offline Art

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Re: Weak rear brake
« Reply #3 on: 21 February, 2020, 12:38:24 PM »
I'm using Brenta Standard GG Type pads at £11.56 a pair from Wemoto, they give me 20,000 miles and stop me fine. As above do not expect too much from the rear brake on any motorcycle but you should get something from it especially with Honda's Combined Braking System.

Today's MOT will reveal all when the brakes are tested on the rollers. Tell the tester you think the rear brake is under performing and he'll explain the results of the test to you. Although it should be noted that brakes have to be proper poorly to fail the requirements of an MOT test.

https://www.wemoto.com/bikes/honda/cbf_1000_a6_sc58b_abs_model/06/picture/brake_pads_front_brenta_standard_gg_type

Offline Greenfingers

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Re: Weak rear brake
« Reply #4 on: 21 February, 2020, 01:57:04 PM »
Thanks for the replies.

The good news is it passed the MOT test, albeit with 3 advisories:-
Front tyre worn close to legal limit
Rear brake grabbing slightly
Nail in rear tyre

Front tyre - no worries, I'll get a new one.

Rear brake - the tester pointed out that the rearmost piston didn't look completely square to the brake disc, so I guess a strip down of the caliper and perhaps a new seal kit is in order. Should be a rewarding task to do on a rainy weekend.

I hadn't noticed the (tiny) nail in the back tyre, so when I got home, I held my breath and pulled it out - SSSSSSsssssss. At least that explains why the tyre pressure was low when I checked it the other day, but it is a nice Pilot 4 tyre and I don't really want to fork out another £100 unless necessary. The hole is almost in the middle of the tyre, so would it be okay to get it repaired? I see there are kits available cheaply online for plugging the hole without even removing the wheel or tyre.

Offline jm2

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Re: Weak rear brake
« Reply #5 on: 21 February, 2020, 05:03:26 PM »
*Originally Posted by Greenfingers [+]
… Rear brake - the tester pointed out that the rearmost piston didn't look completely square to the brake disc, so I guess a strip down of the caliper and perhaps a new seal kit is in order. Should be a rewarding task to do on a rainy weekend.
...
^^^ This.   The caliper (at 31k) is well overdue some tlc.  Do as you suggest and it'll restore its performance without doubt.  Add to your shopping list brake/clutch cleaner in abundance and a small amount of red rubber grease, oh and enough dotty4 to flush through (get rid of what you can).
Only do it right - no bodging please.   Keeper of the failed stator list.   John.

Offline Art

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Re: Weak rear brake
« Reply #6 on: 22 February, 2020, 11:45:00 AM »
It's all good news then. Before completely stripping down the caliper I'd give the caliper pistons an in situ clean up and inspection first, it could just be the ring of crap that builds on the piston putting it out of square but be aware it could also be a failed or failing seal too. While you're there have a look at the front calipers too. Good advice above to flush through the brake fluid especially if you've any doubts on the service history. I'd emphasise here that flushing the system where you use the new fluid to push the old fluid through and out of the system is the preferred and easier method for the home DIY mechanic. Draining the system and re-filling the system as the workshop manuals suggest can have its problems particularly with the ABS models.

1L of DOT4 brake fluid is enough to flush through the entire ABS braking system. When I do mine I flush through more than is possible necessary by way of around 200 - 250 ml for each caliper, the bleed sequence to follow is

Front brake reservoir - front right upper, front left upper
Rear brake reservoir - front right centre, rear lower, rear upper

While your there you'll have sufficient surplus fluid from 1L to flush the clutch system too.

For punctures if you repair it and it fails we don't want it ending in tears therefore if you have any doubts many garages will repair a motorcycle puncture for you by way of a mushroom insert for £20-30 the only consideration here is how much tread is left on the tyre. Don't bother with the mobile repairers they typically charge a minimum of £60 for a puncture repair which in most cases is not worth the remaining tread.

I've been successfully using the sticky strings or worms as some call them for the past 25 years and they form part of my under seat carry kit. I've also successfully used the split mushroom rubber type of plug but only the once and it was much trickier to insert than the string type. Critical to a good lasting repair with both types is to use sufficient rubber cement solution, leave time for the solution to set and leave no protrusions. If you do your own repair check the repair after 10 miles or so and every day or two until you're satisfied the repair is good, if the plug starts to protrude cut back the surplus.


Offline Greenfingers

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Re: Weak rear brake
« Reply #7 on: 22 February, 2020, 03:54:33 PM »
That all sounds like good advice. Thank you for taking the time.

Actually, after removing the outer pad and looking at the rear caliper in situ, I found that with a narrow filler knife I can push the 3 pistons back easily and they all move forward smoothly again when the pedal is pushed. The remaining drag, which isn't too bad, is from the pad on the back side of the disc. Pretty sure it's not air in the system (I spent many years working with hydraulics as a mechanical engineer), because I can push the whole caliper towards the disc and it doesn't spring back. I imagine the sliders need a good clean and lube, so will look up the procedure, but perhaps it is easier to do this with the caliper disconnected and removed anyway.

I've ordered a sticky string puncture repair kit, so at least I'll be able to inflate the tyre again. Being a tight arse and not wanting to waste the decent amount of existing rubber above the wear indicators will probably result in the worm living in the tyre for it's life!

Offline KiwiBob

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Re: Weak rear brake
« Reply #8 on: 23 February, 2020, 04:01:09 AM »
Hi Greenfingers, just to add to your rear brake overhaul, I’d recommend stripping the rear brake pedal  at the same time. I have found on a few bikes that the shaft the pedal pivots on often get stiff and the grease is all dried up. A good clean of the shaft and bore then regrease it can give the pedal much better feel and the action is much smoother.

Offline Art

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Re: Weak rear brake
« Reply #9 on: 23 February, 2020, 09:58:00 AM »
Nothing 'tight arse' in repairing your own punctures and achieving fair wear and tear from your rubber Greenfingers, I admire all that. If its broke fix it, if its got life in use it, if you can do it yourself why pay others to do it for you?

Happy Days

 


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