School me on LHRB (left hand rear brake) for V4

T

TomFoolery

Joined Aug 2021
648 Posts | 567+
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I searched and found two threads both documenting issues with the IMA system.

Thumb rear brake for a v4 | Ducati Forum
SOLD! - IMA thumb brake - pro setup both masters and both bar and fork mounts | Ducati Forum

Has the thinking evolved recently and does anyone have a WORKING LHRB system installed on a V4??

Here are my needs:
  1. Track-only bike, I am happy to eliminate foot brake altogether, and also happy to go with handlebar mount instead of fork mount.
  2. I do want a master cylinder that has enough power to slow the bike noticeably. I have an LHRB on one of my other bikes (with a 16mm master cylinder I am told, made by 'discaciatti') and it barely works. As in, it doesn't even slow the bike down, its almost like I don't have a rear brake at all.
Can anyone share recent experiences with LHRBs?
 
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My understanding, is, on a trackbike, they're meant to be weak. As it's tricky to finesse, so, full force gives reasonable braking force. I guess enough to skid in pit lane, and look cool 😎
 
RickD996 said:
My understanding, is, on a trackbike, they're meant to be weak. As it's tricky to finesse, so, full force gives reasonable braking force. I guess enough to skid in pit lane, and look cool 😎
Click to expand...

I hear ya. Two thoughts -

  1. Even a foot operated rear brake is unlikely to offer enough force to lockup the rear at any decent pace?
  2. In a bike where stock ABS system is not deleted, if you leave it in Level 2, I believe ABS also applies to rear brake. Which makes #1 even less likely, regardless of foot lever operated or left hand operated? Correct, or no?
 
TomFoolery said:
I hear ya. Two thoughts -

  1. Even a foot operated rear brake is unlikely to offer enough force to lockup the rear at any decent pace?
  2. In a bike where stock ABS system is not deleted, if you leave it in Level 2, I believe ABS also applies to rear brake. Which makes #1 even less likely, regardless of foot lever operated or left hand operated? Correct, or no?
Click to expand...

Sounds reasonable 🤔

I think small rear braking can counter wheelie, and help with cornering though?
 
I have the IMA Thumbrake, I also have the foot brake. Rick is right, there is some finessing of the amount of brake pressure you set it up to have, if it’s too strong you lock the rear wheel up VERY easily, and it start slithering side to side in the braking zone…but it has to be just strong enough transfer some weight forward on the bike.

I don’t use it for cornering, though it can be used effectively that way if you are skilled enough, I’m not.

I use it on specific places on a course where I KNOW ahead of time I’m likely to wheelie, but that’s only occasionally…but I use it a lot in heavy braking zones.

As I’m entering a heavy braking zone I lightly touch the thumbrake/rear brake just before I squeeze on the front brake hard and kinda of transfer from light rear/thumb brake to strong front brake with the thumbrake releasing as I’m adding front brake.

It’s only useful in very hard braking zones where you are braking so late and hard that it’s unsettling the bike a bit…using the thumbrake as described keeps the bike feeling nice and settled in hard braking zones, so usually only in a few places on any given track.

The thumbrake should only be used in a pre-planned calculated way, in a measured controlled way. Otherwise if you are using it reactively it’s very easy to over do it and lock the rear up and unsettle the bike.

So I only use it on known hard braking zones and known wheelie spots on the tracks I go to.

The more care I take in ‘settling’ everything before tip in the faster I go at my skill level, the thumbrake is a useful tool in SOME instances for settling the bike, or keeping it from becoming unsettled…it’s not there for stopping power, it’s there for SMOOTH weight transfer from back to front on the bike, whether that be to resist wheelies or under hard braking.
 
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TomFoolery said:
I hear ya. Two thoughts -

  1. Even a foot operated rear brake is unlikely to offer enough force to lockup the rear at any decent pace?
  2. In a bike where stock ABS system is not deleted, if you leave it in Level 2, I believe ABS also applies to rear brake. Which makes #1 even less likely, regardless of foot lever operated or left hand operated? Correct, or no?
Click to expand...

No

The rear locks up VERY easily because you are shifting the weight off the rear wheel in braking, the rear wheel gets very light and locks up with any substantial brake force at all, then the rear starts to ‘slither’ side to side (ask me how I know haha) the slithering is manageable but unsettling and can take you off the line.

ABS 2 on track is a bad idea, the bike does some weird stufff that’s not always predictable on track and that’s also unsettling and can take you offline,

I only use ABS 1 on the track even as a Novice, it’s more predictable, although I would do no ABS if it wasn’t also tied into skid control, which works very well on the bike in a very predictable way that you can play with.
 
Steven31371 said:
I have the IMA Thumbrake, I also have the foot brake. Rick is right, there is some finessing of the amount of brake pressure you set it up to have, if it’s too strong you lock the rear wheel up VERY easily, and it start slithering side to side in the braking zone…but it has to be just strong enough transfer some weight forward on the bike.

I don’t use it for cornering, though it can be used effectively that way if you are skilled enough, I’m not.

I use it on specific places on a course where I KNOW ahead of time I’m likely to wheelie, but that’s only occasionally…but I use it a lot in heavy braking zones.

As I’m entering a heavy braking zone I lightly touch the thumbrake/rear brake just before I squeeze on the front brake hard and kinda of transfer from light rear/thumb brake to strong front brake with the thumbrake releasing as I’m adding front brake.

It’s only useful in very hard braking zones where you are braking so late and hard that it’s unsettling the bike a bit…using the thumbrake as described keeps the bike feeling nice and settled in hard braking zones, so usually only in a few places on any given track.

The thumbrake should only be used in a pre-planned calculated way, in a measured controlled way. Otherwise if you are using it reactively it’s very easy to over do it and lock the rear up and unsettle the bike.

So I only use it on known hard braking zones and known wheelie spots on the tracks I go to.

The more care I take in ‘settling’ everything before tip in the faster I go at my skill level, the thumbrake is a useful tool in SOME instances for settling the bike, or keeping it from becoming unsettled…it’s not there for stopping power, it’s there for SMOOTH weight transfer from back to front on the bike, whether that be to resist wheelies or under hard braking.
Click to expand...

I appreciate your thoughts, and Ricks.

I should clarify - zero intention of using thumb brake in hard braking zone. Front works great. The use case I want to explore is to use it as a line tightening tool in long maintenance throttle corners to allow gas to be more pinned while still tightening/holding line. Secondary use case is back straight of COTA where the bike will freaking wheelie at 140. Wheelie control will keep me out of trouble however it is mentally lower stress to safely pin the throttle without front coming up even slightly.

Can you tell me about the hardware itself? How did you get IMA setup to work, those threads I linked in OP seem to indicate IMA clamp doesn't play nice with the V4 forks? Also, did you remove the rear MC and move it to the IMA setup, or did you buy a version of their kit that allows you to retain both thumb and foot? What brake line did you order, can you share the length and banjo angles?
 
IMG_1971.jpegIMG_1970.jpegIMG_1969.jpegIMG_1968.jpegIMG_1967.jpeg


Banjo Angles in the pics.

I used the clipon bar clamp not the fork clamp…and two IMA MC’s to retain the foot brake, though the only reason I kept the foot brake was at the time I was still occasionally riding the bike on the street and when stopped at traffic lights I prefer to rest my toe on the foot brake instead of squeezing and holding the front brakes, really don’t need the foot brake at all now.

If I remember right the brake line was about 48 or 50 inches
 
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Steven31371 said:
View attachment 50282View attachment 50283View attachment 50284View attachment 50285View attachment 50286


Banjo Angles in the pics.

I used the clipon bar clamp not the fork clamp…and two IMA MC’s to retain the foot brake, though the only reason I kept the foot brake was at the time I was still occasionally riding the bike on the street and when stopped at traffic lights I prefer to rest my toe on the foot brake instead of squeezing and holding the front brakes, really don’t need the foot brake at all now.

If I remember right the brake line was about 48 or 50 inches
Click to expand...

Thank you, I appreciate it.
 
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@Steven31371 one more question for you - do you know the exact specification (piston size etc) of the IMA master cylinder? SBK unlimited says that IMA's master is more powerful than the OEM foot master. I am curious if that's the case.

I plan to eliminate the foot control altogether, I am trying to decide if I should just move the OEM master over to the handlebar (much cheaper this way) or pay for the IMA master and throw the OEM master away.
 
TomFoolery said:
@Steven31371 one more question for you - do you know the exact specification (piston size etc) of the IMA master cylinder? SBK unlimited says that IMA's master is more powerful than the OEM foot master. I am curious if that's the case.

I plan to eliminate the foot control altogether, I am trying to decide if I should just move the OEM master over to the handlebar (much cheaper this way) or pay for the IMA master and throw the OEM master away.
Click to expand...
Not that it would take a lot to offer more braking force than the OEM rear, but I'd think a thumb mounted would have to be as you can exert more force with your foot than thumb.

I'd probably try it with the OEM before throwing more money at it.
 
bp_SFV4 said:
Not that it would take a lot to offer more braking force than the OEM rear, but I'd think a thumb mounted would have to be as you can exert more force with your foot than thumb.

I'd probably try it with the OEM before throwing more money at it.
Click to expand...

I agree with you - hand operated controls have way less leverage than feet. The LHRB I have on my Kramer with a 16mm piston master (claimed) is handlebar mounted, but with a traditional shorty brake lever (instead of thumb). And even then, its extremely weak/ineffective. I am not sure if its because of significantly increasing the length of brake line (from handlebar all the way to the rear caliper) and significantly increasing the amount of fluid relative to piston size..... or some other reason, but its very disappointing.

On the v4, I plan to leave the ABS intact so the brake line from handlebar will only go as far as ABS unit.
 
TomFoolery said:
@Steven31371 one more question for you - do you know the exact specification (piston size etc) of the IMA master cylinder? SBK unlimited says that IMA's master is more powerful than the OEM foot master. I am curious if that's the case.

I plan to eliminate the foot control altogether, I am trying to decide if I should just move the OEM master over to the handlebar (much cheaper this way) or pay for the IMA master and throw the OEM master away.
Click to expand...

Unfortunately no

But anocdotally, I have a $1500 Brembro rear MC that’s WSBK Spec that we wanted to use, but it wouldn’t work with the IMA MC up by the clipons because the pressures values were too far apart.

I’d use the IMA MC, the whole system is engineered to work well together.

Also, even for how you want to use the rear brake you want to avoid having a lot of stopping power in the system, using the rear brake requires a lot of finesse, and under braking with the rear brake causes very few problems, while over braking can lead to immediate catastrophe lol
 
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I wouldn't be worried about having too much braking force while using a thumb brake for two reasons...

1. Caliper is small and yes sure it can lock the rear wheel but that requires a decent amount of pressure from the MC.

2. There's multiple times more finesse available at the thumb than the foot, unless you're a ballet dancer.
 
I have the IMA on my 1299 and RACETORX on my V4 . Racetorx wayyy better than IMA , much more compact and better feel. The IMA adjustment set up is to clumsy . When inatalling buy a banjo bolt with a built in bleed screw and use it at the MC.
racetorx.co.uk

Racetorx Performance Thumb Brake

Racetorx Thumb brake kit for Racebikes, stunt bikes, road-riding, motocross and adventure bikes. left thumb-operated rear brake for more control of rear wheel
racetorx.co.uk
 
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I find dragging the rear brake through chicanes and hair pin corners while on throttle keeps the bike stable and youre already into the meaty bit of the throttle at exit.

Straight line hard braking get on the rear to pull the swingarm down then transfer onto the front , kind of stops the rear from lifting as much
 
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Hello peeps,

Hope everyone had a great summer. Due to various other competing projects, I never got this LHRB project done and just now revisiting it.

Since our discussion a few months ago, I have learned of people using a clutch master cylinder as a left hand lever brake connected directly to the rear caliper. Intrigued by this idea, I spoke with Kramer USA (was on the phone with him ordering parts for other bikes and this topic came up by chance) and he said he had used a Brembo RCS16 clutch master in similar fashion on a test bike and it worked reasonably well.

Curious if anyone has tried this (using a clutch master as a brake lever) or at least heard of this approach? Seems a lot simpler than the thumb brake and master cylinder relocation business.
 
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TomFoolery said:
Hello peeps,

Hope everyone had a great summer. Due to various other competing projects, I never got this LHRB project done and just now revisiting it.

Since our discussion a few months ago, I have learned of people using a clutch master cylinder as a left hand lever brake connected directly to the rear caliper. Intrigued by this idea, I spoke with Kramer USA (was on the phone with him ordering parts for other bikes and this topic came up by chance) and he said he had used a Brembo RCS16 clutch master in similar fashion on a test bike and it worked reasonably well.

Curious if anyone has tried this (using a clutch master as a brake lever) or at least heard of this approach? Seems a lot simpler than the thumb brake and master cylinder relocation business.
Click to expand...

That’s an awesome idea… I’ll add that a RCS brake MC can be used as a thumb brake if spun the other and a suitable lever was attached.
 

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