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V85TT bad rear brake

Printed From: guzziriders.org - moto guzzi forum
Category: Technical
Forum Name: Technical services
Forum Description: For members who are able to help out others with specialised equipment.
URL: http://www.guzziriders.org/forum_posts.asp?TID=14800
Printed Date: 06 Feb 2023 at 07:22
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Topic: V85TT bad rear brake
Posted By: Pernao
Subject: V85TT bad rear brake
Date Posted: 19 Sep 2022 at 12:24
Hi, 

New to the forum. I bought yesterday a new V85TT and I have made some hundred kms of mountain roads. Liked the bike with the exception of the rear brake that is incredibly bad.

Very, very weak, without sensibility and spongy, going deeper and deeper with prolonged use.

This is "normal", I mean do that V85TT has a bad rear brake or the motorcycle was delivered with a problem?

 I know that in the past the Guzzii rear brake also actuated the frontal brakes. It is still the case?



Replies:
Posted By: Mike H
Date Posted: 19 Sep 2022 at 18:18
Mine isn't the 85TT, but the V7 850 - however similarly the rear brake is next to useless. No it is not linked to the front. Guzzi stopped doing that a while back, can't remember when exactly. 

However rear brake has been improved somewhat by changing the pads to sintered, and adding a Harley type brake pedal extender to the pedal, this provides a large flat oval pedal that I can get a good stomp with. Sorry but I've concluded brake pedals that look like gear pedals are just daft. 

Don't know about the spongy thing  - you might want to take the caliper off and pads out for examination - two issues with the V7 850  - the caliper is single piston sliding type and could get hung up on the pins it's meant to slide on (but are seized)  - second issue, pads are retained by 2 pins that screw in with heads like grub screws with Allen key hex holes. - these must be removed and greased ASAP. They are held in with a locking compound (not Loctite) if not removed fairly soon will seize solid and Allen key will just round out the holes. Shocked


-------------
"Chicken nuggets don't dance on a Tuesday."


Posted By: Brian UK
Date Posted: 19 Sep 2022 at 21:28
Originally posted by Mike H Mike H wrote:

Don't know about the spongy thing  - you might want to take the caliper off and pads out for examination - two issues with the V7 850  - the caliper is single piston sliding type and could get hung up on the pins it's meant to slide on (but are seized)  - second issue, pads are retained by 2 pins that screw in with heads like grub screws with Allen key hex holes. - these must be removed and greased ASAP. They are held in with a locking compound (not Loctite) if not removed fairly soon will seize solid and Allen key will just round out the holes. Shocked

If spongy then get it back to the supplying dealer to sort out. Spongy brakes are not right. Possibly just needs bleeding, but it does need sorting out and if you start modifying things on a bike that is only a few days old you void the warranty.


-------------
Brian.

Better 5 minutes late in this world than years early in the next.


Posted By: Andy M
Date Posted: 20 Sep 2022 at 07:12
I can't remember the last modern bike I had with a back brake that did anything without putting your full weight on the pedal. Honda NC and CB's, V7-850, Weestrom, all rubbish. Enfield's are better . It's race fashion (along with pointless twin discs), the designers don't think we use them and no one ever walked out of the showroom over it.

I've fitted a pedal extension like Mike H.

Guzzi went down the right lines 50 years ago with linked brakes and plain cast iron discs, but faced with the extra costs and angry toddler journalists rejoined the fashion herd. I've been selling and designing brake systems for 30 years and what racing has made the motorcycle market thinks it wants is honestly disgusting, but as a fashion product there is nothing much to be done. You've only to read all the "wah wah the linked brakes make my tum tum feel squidgy I'm going back to 1915" stuff on every forum related to bikes that have them to see what you are up against. 

Andy 


Posted By: Brian UK
Date Posted: 20 Sep 2022 at 08:18
Did they have rear brakes in 1915? Wink


-------------
Brian.

Better 5 minutes late in this world than years early in the next.


Posted By: ranton_rambler
Date Posted: 20 Sep 2022 at 12:57
Originally posted by Brian UK Brian UK wrote:

Did they have rear brakes in 1915? Wink
I recently borrowed a 1923 Matchless - the rear brake was much more useful than the front.


Posted By: Speciality
Date Posted: 20 Sep 2022 at 15:32
That was true of most British bikes until the second half of the sixties….


Posted By: Speciality
Date Posted: 20 Sep 2022 at 15:44
The rear brake on my 850 Special is better than most of the bikes I’ve had in the last couple of decades, apart from the drum rear on my glad-I-got-shot-of-it RE C5. It’s not great but I can feel it working, which is something these days. The one on my NC750X is wooden and does very little. Neither brake is spongy. FWIW I wouldn’t expect the brakes on a brand new bike to work brilliantly until scrubbed in a bit. As advised I removed the retaining pins and Coppaslipped them. Mine came out easily enough; there was nothing on the threaded part of the pin by way of loctite or similar. Front brake is a bit spongy but works well.


Posted By: Dave P.
Date Posted: 20 Sep 2022 at 19:15
I'm just wondering why twin discs might be "pointless" Andy. I have no opinion on this as my bikes all have drum brakes. I'm just curious.

-------------
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.


Posted By: Simond
Date Posted: 20 Sep 2022 at 19:31
I suspect back in the 70’s Guzzi were far ahead of the crowd with linked brakes, my LeMans still has them, and they’re excellent.  I can’t think why anyone would change them, unless they’re racing.  I’m pretty sure that Guzzi's brake engineers know / knew more about it than hobby enthusiasts and journalists.

My 2020 BMW also has linked brakes, though all electronic & clever, with ABS etc., and controlled by my right hand rather than foot.  They seem pretty damn good too.

I too spent a few years of my professional life designing & developing disc brakes - big ones, for trains…


Posted By: Pernao
Date Posted: 21 Sep 2022 at 01:39
Thanks to all. Perhaps I should have explained that I have not a big experience with modern road bikes. However about 20 years ago I had a Triumph 900 and I didn't found the rear brake particularly bad, neither in other motorcycles that I have used, namely, more than 20 years ago a Africa Twin and more recently, 4 or 5 years ago, a Transalp 700.

But I have raced raid type motorcycles for 15 years, occasionally also in roads, and I do use the rear brake to control the bike, more than for braking and I am truly disappointed with the V85TT rear brake. On the 1000km revision I will try to see if there is something wrong, I will mount better pads and see if the braking gets better. Again, thanks to all. It was relevant information.


Posted By: Andy M
Date Posted: 21 Sep 2022 at 10:54
Originally posted by Dave P. Dave P. wrote:

I'm just wondering why twin discs might be "pointless" Andy. I have no opinion on this as my bikes all have drum brakes. I'm just curious.

Lets knock down the marketing guff one bit at a time 
 
The limit of deceleration is set by the tyre. A single disc will lock it on a dry surface, so the second disc is adding nothing. Any disc braked bike that wouldn't benefit from ABS is a missed opportunity and I doubt many exist. Cable operated drums were or course very different. 

The idea of twisting the forks of other means of brake steering is insane, every car, truck etc. has one disc on one side of a wheel. The structure is robust so this doesn't happen. 

A road bike and race bike have very different temperature profiles. The race bike does a warm up lap then multiple decels from high speed in a few miles . This keeps the brake warm. A road vehicle rarely suffers overheating, you ride miles with tiny decels then try an emergency stop, the twins are further below optimum temperature than the single. When I look at ECU data it's rare to see any road vehicle go over 0.4G, yet the occupants will tell you it was at the limit. Our monkey brains limit us except when we've done ten laps in practice. 

Wear can be caused by use or glazing. The latter is caused my making enough heat to soften the lining but not enough force to crumble off the resulting glass before it makes a thick layer that then either doesn't brake well or comes off in lumps. A single worked nearer capacity will glaze less, the underworked twin more. When the pads glaze replacing one pair costs less.

Feel is hard to specify. A twin disc will build deceleration faster so might feel better. You can get the same effect by changing pad materials or upping the size of the master cylinder, so why suffer wear etc. 

The only other vehicles that use multiple discs are off highway types and aircraft where the wheel has a much greater load and is limited diameter. It's still not a preferred solution because running costs are higher as is weight and cost. 

I'd be interested to talk to a race bike designer. The unsprung weight of twin discs is against their primary aim, so either they do still have an overheating problem from the multiple hard decels or the rules or sponsors force them to stick with them. The track isn't the road though. 

Left to my own devices I'd start with something like this



Disc as big as you like to set heat to the application and likewise choose a calliper for performance/feel. Split the calliper plumbing so the rear control gives 1/3 on the front. 

Andy 




Posted By: AdrianW
Date Posted: 21 Sep 2022 at 14:49
Andy,
Thought I recognised the wheel -  here's one I bought earlier (and still have!) ..




One disk is plenty on this... There is a small one at the back too, just in case!!

Cheers,
Adrian
Bristol UK


Posted By: Brian UK
Date Posted: 21 Sep 2022 at 15:12
I remember when I had my Spada III MOT test done, I heard the tester shout in surprise, the single front disc had acheived over 50% efficiency. It did work well.
Mind you he then went on to fail the "back" brake at 24%. Wouldn't be told to take the front left disc into account.


-------------
Brian.

Better 5 minutes late in this world than years early in the next.


Posted By: borderer
Date Posted: 21 Sep 2022 at 20:08
Its curious why most people will be happy with a single disc per wheel on their car but not on a bike, i remember getting into a bit of an argument regarding the CARC bikes someone insisted that you have to drill and lockwire the rear wheel bolts! he was quite happy with unlockwired bolts on his car. I think that some of the racing guzzies with dr John were running on a linked brake system for all 3 discs. 


Posted By: Brian UK
Date Posted: 21 Sep 2022 at 21:43
Originally posted by borderer borderer wrote:

i remember getting into a bit of an argument regarding the CARC bikes someone insisted that you have to drill and lockwire the rear wheel bolts! he was quite happy with unlockwired bolts on his car. 

And yet the stresses on the car wheel are far higher.


-------------
Brian.

Better 5 minutes late in this world than years early in the next.


Posted By: Simond
Date Posted: 21 Sep 2022 at 22:11
Originally posted by Andy M Andy M wrote:


The only other vehicles that use multiple discs are off highway types and aircraft where the wheel has a much greater load and is limited diameter. It's still not a preferred solution because running costs are higher as is weight and cost. 

Andy 



Trains have (well, had, I’ve been out of that business for many years) multiple discs per axle in some cases. 

Typically, medium speed & freight have one disc per wheel (which are fixed to the axle) but high speed trains may have three or four discs per axle.  Diameter isn’t the issue, it’s energy, and how hot the disc (and pads) would get under a full emergency deceleration from Vmax.

The limiting deceleration is, as with motorbikes and cars, determined by the grip between wheel and rail.

Atb
Simon 




Posted By: borderer
Date Posted: 22 Sep 2022 at 10:52
Some tractors have multi discs on the axle running in Oil? in a sealed unit.


Posted By: ranton_rambler
Date Posted: 22 Sep 2022 at 12:41
Yes, most off-highway equipment has multi-plate wet discs.


Posted By: borderer
Date Posted: 22 Sep 2022 at 16:58
I suppose this isn't much help regarding the original questionSmile. Yep the V85 brakes appear to be soft, I stripped the caliper and lubed everything than needed doing. Its a little better but improves with use. I think its a dealer job to bleed the brakes with the ABS system.


Posted By: Mike H
Date Posted: 29 Sep 2022 at 18:51
Again, re V7 850, not specifically V85TT, but service manual says brake bleeding can be done in the conventional manner.


Originally posted by Brian UK Brian UK wrote:

If spongy then get it back to the supplying dealer to sort out. Spongy brakes are not right. Possibly just needs bleeding, but it does need sorting out and if you start modifying things on a bike that is only a few days old you void the warranty.


Originally posted by Pernao Pernao wrote:

... have made some hundred kms of mountain roads.
... without sensibility and spongy, going deeper and deeper with prolonged use.


Does sound like should go back to dealer.

Mine did take nearly 100 miles to stiffen up and start workng properly, with new pads of course, but he says hundeds of km.






-------------
"Chicken nuggets don't dance on a Tuesday."


Posted By: Pernao
Date Posted: 14 Nov 2022 at 00:18
Some news about this problem: I changed the oil fluid, bleed the system and it become slightly better. Took the bike for the first revision, complained about the rear brake, they changed the fluid again, tried the motorcycle, comparing with other V85TT that were in the shop and said to me it was ok. 

Actually it is a bit worse than when I bleed the system (the pedal brakes further down).

So I am changing for EBC brake pads. I found some on Ebay but on the reference  they say that they are suitable for models between 2019 and 2020. They changed the rear brake in the 2021 and 2022 models or are the pads the same for a 2022 model?
https://www.ebay.fr/itm/373809859233?_trkparms=amclksrc%3DITM%26aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D243354%26meid%3D6c3a9155245748c19c03c6df7741ae44%26pid%3D101224%26rk%3D2%26rkt%3D5%26sd%3D284969432530%26itm%3D373809859233%26pmt%3D0%26noa%3D1%26pg%3D2047675%26algv%3DDefaultOrganicWeb&_trksid=p2047675.c101224.m-1" rel="nofollow - https://www.ebay.fr/itm/373809859233?_trkparms=amclksrc%3DITM%26aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D243354%26meid%3D6c3a9155245748c19c03c6df7741ae44%26pid%3D101224%26rk%3D2%26rkt%3D5%26sd%3D284969432530%26itm%3D373809859233%26pmt%3D0%26noa%3D1%26pg%3D2047675%26algv%3DDefaultOrganicWeb&_trksid=p2047675.c101224.m-1

"EBC FA256 737.09.50 For Moto Guzzi 850 V85 Tt 2019-2020 


Posted By: Pernao
Date Posted: 14 Nov 2022 at 01:55
Originally posted by Mike H Mike H wrote:

Mine isn't the 85TT, but the V7 850 - however similarly the rear brake is next to useless. No it is not linked to the front. Guzzi stopped doing that a while back, can't remember when exactly. 

However rear brake has been improved somewhat by changing the pads to sintered, and adding a Harley type brake pedal extender to the pedal, this provides a large flat oval pedal that I can get a good stomp with. Sorry but I've concluded brake pedals that look like gear pedals are just daft. 

Don't know about the spongy thing  - you might want to take the caliper off and pads out for examination - two issues with the V7 850  - the caliper is single piston sliding type and could get hung up on the pins it's meant to slide on (but are seized)  - second issue, pads are retained by 2 pins that screw in with heads like grub screws with Allen key hex holes. - these must be removed and greased ASAP. They are held in with a locking compound (not Loctite) if not removed fairly soon will seize solid and Allen key will just round out the holes. Shocked

Hi,

It seems you are right (see the previous post). It seems that the brake is OK, or at least it is what the Guzzi mechanic says. He compared the breaking of my bike with other V85tt he had in the shop and says it is about the same.

So, I am going to change for EBC HH, and about that extension, I cannot use anything that is not from moto guzzi without voiding the warranty, but they have this:

https://tlm.nl/moto-guzzi-triumph/2s001391-rempedaal-verbreder-v85-tt?sku=2S001391&gclid=Cj0KCQiAyMKbBhD1ARIsANs7rEHo8AsbgrWykUSJsmKfCz4W_I2fWmb5N9qk8bC2YbaftW886gjdB5gaAk3aEALw_wcB" rel="nofollow - https://tlm.nl/moto-guzzi-triumph/2s001391-rempedaal-verbreder-v85-tt?sku=2S001391&gclid=Cj0KCQiAyMKbBhD1ARIsANs7rEHo8AsbgrWykUSJsmKfCz4W_I2fWmb5N9qk8bC2YbaftW886gjdB5gaAk3aEALw_wcB

It only increases marginally the size of the lever, but will give the foot more support.

By the way, do you know if the EBC right pad for the rear brake is the EBC FA256?
They say they are for the 2019 and 2020 models. They have changed the rear brake or it is the same for the 2021 and 2022 models?

https://www.ebay.fr/itm/373809859233?_trkparms=amclksrc%3DITM%26aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D243354%26meid%3D6c3a9155245748c19c03c6df7741ae44%26pid%3D101224%26rk%3D2%26rkt%3D5%26sd%3D284969432530%26itm%3D373809859233%26pmt%3D0%26noa%3D1%26pg%3D2047675%26algv%3DDefaultOrganicWeb&_trksid=p2047675.c101224.m-1" rel="nofollow - https://www.ebay.fr/itm/373809859233?_trkparms=amclksrc%3DITM%26aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D243354%26meid%3D6c3a9155245748c19c03c6df7741ae44%26pid%3D101224%26rk%3D2%26rkt%3D5%26sd%3D284969432530%26itm%3D373809859233%26pmt%3D0%26noa%3D1%26pg%3D2047675%26algv%3DDefaultOrganicWeb&_trksid=p2047675.c101224.m-1


Posted By: Speciality
Date Posted: 14 Nov 2022 at 08:15
I doubt that anyone will have the definitive answer to that, but I have found that suppliers can be slow to update the years to which parts they sell apply and that unless the new year model is obviously a significant refresh the existing parts usually fit the previous model. Unless someone knows for certain I suggest you order them and compare to the originals and if they look like they won’t fit, return them. Best to confirm with the supplier beforehand. FWIW the rear brake on my V7 850 is not brilliant but it does work. 


Posted By: theone&onlymin
Date Posted: 14 Nov 2022 at 08:34
Has it been on an MOT brake tester ?

Cheers
Min


Posted By: Speciality
Date Posted: 14 Nov 2022 at 10:28
Not mine, no. The bike isn’t old enough to need an MOT yet. FWIW I find that most disc rear brakes on the bikes I’ve owned are not particularly powerful or progressive. The one on my V7 850 is a bit better than the one on my NC750X. The last really good rear brake on a bike I’ve had was on my 2015 RE UCE Classic. That had a drum rear brake that was great once I’d taken it to bits and reassembled it properly. That said it’s a long time since I’ve owned a cruiser type bike or an old British bike, which usually had far more effective rear brakes than front ones…


Posted By: Pernao
Date Posted: 14 Nov 2022 at 13:01
No, never been tested in a MOT brake tester.


Posted By: theone&onlymin
Date Posted: 14 Nov 2022 at 13:09
But you could go and discuss it with them so you could. 

Cheers
Min


Posted By: Brian UK
Date Posted: 14 Nov 2022 at 13:34
That's reletively easy to do in the UK Min, but I don't know what the system is in Portugal.
But certainly a check of the actual braking efficiency would be useful.



-------------
Brian.

Better 5 minutes late in this world than years early in the next.


Posted By: Andy M
Date Posted: 14 Nov 2022 at 14:11
It will almost certainly pass.

A roller is measuring both tyre and brake friction. Assuming the roller isn't shiny, wet and lubricated with years of debris, you'll achieve the 30/25 percent level with rashers of bacon fitted instead of pads. What you are mostly measuring is the balance of tyre to brake, the tester assuming a fixed relationship to determine the brake's influence. Get a heavy operator and low tyre pressure and it won't peak fast enough to interpolate 30/25. Too light and a good stomp on the pedal and lock is too fast. The MOT isn't a serious test (It's years out of date), it's there to trap the ones with the cardboard packaging fitted instead of the pads. If you want to see the real number you need to strap the bike down and measure the load as part of the calculation.

25% decel is typical at the bottom of a motorway slip road with an underpass that restricts vision and results in overconfidence then slight panic. It feels uncomfortable, but isn't teeth in the headstock stuff. If that's the  performance stood on the pedal you won't be happy.

What everyone wants is a change of feel which isn't measured. Less travel to the point decel is detectable is desired. Faster build up to temperature and thus less pedal variation to achieve a steady state. Most bikes would benefit from a bigger master cylinder (or smaller calliper) but would then need adjustable controls to stop them feeling too vicious to riders wearing size 12 diving boots and the service intervals might not be acceptable. Changing the pads for the temperature relationship can help, so can making the pedal adjust.

Personally I don't feel Piaggio accept any warranty, so have no problem using non-MG solutions, but you have to gauge that yourself.

Andy 




Posted By: theone&onlymin
Date Posted: 15 Nov 2022 at 11:30
Not getting into a fight about this so I'm not as I'm not qualified to do so. Showed the comments to my  MOT tester who would disagree. 

Cheers
Min


Posted By: Stevex
Date Posted: 15 Nov 2022 at 14:47
I de linked my LM2 brakes, all my other bikes have been / are conventional systems, so from this perspective alone it makes sense to me, but I've never been a fan of the linked system.
I run Goodridge hoses, stainless steel discs, carbon ceramic pads and have the very best tyres available for this bike's tyre sizes, Conti radials. Suspension also contributes to good braking and no one can say the poor dampers fitted to big Tontis are anything but barely adequate. I replaced mine with Showa cartridges from an RC36 and re oiled and resprung my Konis. I would class this set up as phenomenal, the braking is absolutely superb in performance. I would go so far as to say that seat of the pants they feel better than my Aprilia Tuono and my Honda CB1300, both of which have braided hose and SBS/Brembo pads.
It's a very individual choice to de link, I've noticed it's almost a mantra with some owners, 'linked is best', probably the same people who have yet to ride a de linked Guzzi. Interesting that Guzzi themselves gave up the linked set up a while back.
If you're happy that the brake has been properly bled then a change of pad material may help. Did you remove the caliper and position it above the rest of the system? Is it a dual piston caliper and did you push the pistons fully in with the bleed nipple cracked open to remove any trapped air?. It's amazing how even a small bubble or 2 will affect braking performance. Also bleeding an ABS equipped bike is no different to any other. I replaced my Honda 1300 rubber hoses for braided and it was one of the quickest and easiest bleeds I'd ever done.



-------------
Steve
https://imgbb.com/" rel="nofollow">


Posted By: Simond
Date Posted: 15 Nov 2022 at 15:05
I’ve had my LeMans for 34 years, and am entirely happy with the linked brakes, they’re certainly more capable than I am.

Why did Guzzi give up, was it pressure from self appointed ”experts” writing in the biking press, or was it simpler and cheaper to go with the flow and do what everyone else did?  I guess we’ll never know.

But I would note that BMWs (at least the current R1250GS) have linked brakes, although from the hand lever rather than pedal, and cars seem to manage entirely fine with linked brakes.

I think Guzzi were way ahead, it worked well, it was convenient & easy to use, and if you wanted more, you’d got a whole spare front brake…

Fully agree re the braided hoses & thorough bleeding though.




Posted By: Andy M
Date Posted: 15 Nov 2022 at 18:36
Originally posted by theone&onlymin theone&onlymin wrote:

Showed the comments to my  MOT tester who would disagree. 

Cheers
Min

You mean a tradesman who owns a roller tester thinks they are great? Ask him to calculate the MFDD from a test result then carry out a road test to the same level as proof his tester is accurate. Any bets he doesn't know how?

Moto-Guzzi got rid of linked brakes because of market pressure. When you investigate crashes the data will usually show levels of braking way below what the vehicle is capable of. It's why AEB functions are now having a real effect, you need to decouple control from a monkey brain with a design speed of 8 mph. If the actual performance is never used, journalists use it as a stick to beat you and you can save cost by getting rid of a few odd fittings, not many will be sorry to see it go. Motorcycles are endlessly held back by a massively conservative market. 

Andy


Posted By: theone&onlymin
Date Posted: 15 Nov 2022 at 19:52
I don't really understand the MFDD from a quick glance at it. But I will read up on it.
What I was hoping to do for Pernao was find some level of comparison, and hopefully  reassurance that his brake was as designed to operate, rather than a seat of the pants/sole of the boot comparison that was offered to him , so I was.

Cheers
Min



Posted By: Brian UK
Date Posted: 15 Nov 2022 at 22:51
This topic has digressed more than just a bit. Discussions about what sort of brake tester or delinking brakes don't answer the original question.


-------------
Brian.

Better 5 minutes late in this world than years early in the next.


Posted By: Simond
Date Posted: 16 Nov 2022 at 07:59
Well, to be fair, he did ask about whether the brakes were linked!

But the question was

“Liked the bike with the exception of the rear brake that is incredibly bad.

Very, very weak, without sensibility and spongy, going deeper and deeper with prolonged use.”

To which I would respond

1. You should be able to lock the rear wheel using the foot brake, unless the ABS prevents you doing so.  (Not sure I’d risk turning the bike off whilst riding to check). Worth checking if there is a mode to disable rear ABS for off-road use, then try it.

2. The brake should not be spongy, this suggests air in the fluid.  Bleed required.

3. “Going deeper and deeper with prolonged use” is more concerning.  Assuming the pad isn’t actually crumbling, this suggests a fluid leak.  If so, need to fix this first.  Note that the leak could be within the system, so fluid may not actually be lost.



Posted By: Andy M
Date Posted: 16 Nov 2022 at 10:08
MFDD is Mean Fully Developed Deceleration. It's the straight bit of the decel curve after all the mechanical lash and pressure build-up and before anything cooks off. It's the type approval standard. A roller test at variable weight fixes the time period to look at and interpolates, hence you can trick them or introduce errors. It's like taking the steering angle as you pull off your drive and using that to predict your journey will end in your neighbours living room.

If the ABS can be made to cycle the limit of adhesion rather than the brake is the limit, so yes, almost certainly as good as it needs to be.

The feeling part leaves engineering and enters ergonomics and psychology. If you can produce 25% decel with your heel on the pedal, 8 inches down the travel, it's a pass but isn't right. Most motorcycles seem to be designed with way more travel and control force required in the area of main use (1-5% decel) than riders desire. I can only assume this is though the use of standard parts, maybe to help untrained (US) riders who fear the front. This means it's really hard to tell if it's got problems.

If we think there is air, bleed it.

Andy 


Posted By: Speciality
Date Posted: 16 Nov 2022 at 10:59
Not qualified to comment on the first part but empirically as I said earlier most modern bikes seem to have relatively inefficient rear brakes, though changing the pads usually helps. Should not be spongy though.


Posted By: Tris
Date Posted: 17 Nov 2022 at 06:44
I found the rear brake on my V9 to be very poor when compared to the Breva 1100 I'd just come off.

Cleaning and lubing everything made little improvement 
Changing the pads did  but they're still not in the class of the V1100

That being said,  it dosn't stand out as a problem now so either it's not an issue or I've adjusted to it 




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2017 V9 Roamer
2005 Breva 1100 - sold
1994 California - sold


Posted By: Mike H
Date Posted: 17 Nov 2022 at 16:38
Originally posted by Pernao Pernao wrote:

Hi,

It seems you are right (see the previous post). It seems that the brake is OK, or at least it is what the Guzzi mechanic says. He compared the breaking of my bike with other V85tt he had in the shop and says it is about the same.

So, I am going to change for EBC HH,
I buy direct from EBC.

Rear, FA256HH - https://ebcbrakesdirect.com/motorcycle/partno/fa256hh" rel="nofollow - https://ebcbrakesdirect.com/motorcycle/partno/fa256hh
Front, FA244V - https://ebcbrakesdirect.com/motorcycle/partno/fa244v" rel="nofollow - https://ebcbrakesdirect.com/motorcycle/partno/fa244v

Quote and about that extension, I cannot use anything that is not from moto guzzi without voiding the warranty,

I can't entirely believe that. it's only literally a bolt-on thingy. I used this, just goes on top of the existing pedal, easily removeable...
https://www.ebay.co.uk/itm/284159172062" rel="nofollow - https://www.ebay.co.uk/itm/284159172062

But I had to make a curved plate to go underneath and be fixed by the screws.







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"Chicken nuggets don't dance on a Tuesday."



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