Riders on disc brakes. How often do you lock up your rear wheel?

Discuss light weight issues concerning road bikes & parts.
TobinHatesYou
Posts: 2069
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

Jugi wrote: ↑
Mon Sep 10, 2018 6:02 pm
TobinHatesYou wrote: ↑
Mon Sep 10, 2018 5:27 am
Going to a smaller rotor will just keep on masking the real problem in your braking technique.
I wouldn’t call that a flaw in technique. At least for me, the easiest braking system to use is the one which will provide optimal stopping power when a similar amount of pressure is applied to both levers. Intuitive braking in a straight line comes first, finesse in trail braking etc. is achieved when the system works logically.

For me it’s about being able to feel and hear the tire being on the edge of losing its grip. With most hydraulic brakes you can adjust the contact point to your liking, so I find this all very irrelevant. The only thing going to a smaller rotor does is decrease you max potential brake power and increase temps.

jfranci3
Posts: 373
Joined: Tue Jul 26, 2016 5:21 pm

by jfranci3

TobinHatesYou wrote: ↑
Mon Sep 10, 2018 5:27 am
Going to a smaller rotor will just keep on masking the real problem in your braking technique. Your rear brake is for slowing down, trail braking after entering a corner slightly too hot for example. It Is something you always apply in a controlled progressive manner. If your body can’t feel the additional braking power working and where the limit of traction is, that’s on you. How did you survive with rim brakes, which have worse modulation?
My breaking technique is fine. I can summon many levels of slip between grip and locked on any decent system. If I have to employ any more technique than a measured initial grip and knowing how to read the feedback loop, the brakes need to be improved. Brakes need to be instinctive.

This is an instant lock. It may be that the Sram stock pads need some heat to make friction and the friction levers change quickly. Larger rotors would give leverage to this.

by Weenie


MichaelB
Posts: 491
Joined: Tue Apr 22, 2008 4:31 am

by MichaelB

Hardly ever.

TobinHatesYou
Posts: 2069
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

jfranci3 wrote: ↑
Tue Sep 11, 2018 12:04 am

This is an instant lock. It may be that the Sram stock pads need some heat to make friction and the friction levers change quickly. Larger rotors would give leverage to this.
I can’t reconcile this. An instant lock...when? I have not experienced anything remotely resembling an instant lock on SRAM HRD with stock pads. If you don’t like SRAM lever feel, you must hate the How Shimano levers have no feel at all until full pad contact, and then they go *clunk*

And to repeat an earlier question, how did you survive with rim-brakes?

jfranci3
Posts: 373
Joined: Tue Jul 26, 2016 5:21 pm

by jfranci3

TobinHatesYou wrote: ↑
Tue Sep 11, 2018 12:20 am
jfranci3 wrote: ↑
Tue Sep 11, 2018 12:04 am

This is an instant lock. It may be that the Sram stock pads need some heat to make friction and the friction levers change quickly. Larger rotors would give leverage to this.
I can’t reconcile this. An instant lock...when? I have not experienced anything remotely resembling an instant lock on SRAM HRD with stock pads. If you don’t like SRAM lever feel, you must hate the How Shimano levers have no feel at all until full pad contact, and then they go *clunk*
IIRC, the Shimanos seemed to have a lot of travel then engaged quite aggressively. SRAM seemed to have faster contact and had more engaged lever travel.

Conditions: dry, clean, level asphalt. 87kg guy with 780mm saddle height and hood contact point at 650mm (total stack). 25c tires at 5.75bar. Fresh brakes fully bed. Rear was locking up on units bite on anything more than light braking.

jlok
Posts: 730
Joined: Tue Jun 30, 2015 3:30 am

by jlok

Maybe you could "calibrate" your hand instead. I used both systems and both 140 and 160 rear rotor. I tend to agree with Tobin. Just learn the point of locking up with each brake system and practise.
Giant Propel Advanced SL Disc 1 / BMC TM02 < Propel Adv < TCR Adv SL Disc < KTM Revelator Sky < CAAD 12 Disc < Domane S Disc < Alize < CAAD 10

TobinHatesYou
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Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

The only other thing I can think of is an overfilled system, but that should feel obviously wrong.

jfranci3
Posts: 373
Joined: Tue Jul 26, 2016 5:21 pm

by jfranci3

jlok wrote: ↑
Tue Sep 11, 2018 12:55 am
Maybe you could "calibrate" your hand instead. I used both systems and both 140 and 160 rear rotor. I tend to agree with Tobin. Just learn the point of locking up with each brake system and practise.
Yeah, no. Calibrated hands don’t work in a calibrated fashion when you’re startled and they should be that easy to lock on flat, dry pavement with lower pressure, good tires. A simple $40 fix should make things much forgiving and safer. I clearly have a lot more power than I need and I live in a flat area, so I don’t need any the heat capacity. The F & R brake efforts should be somewhat consistent on a hydro system.
I haven’t had issues on any other bike, this combo seems to be an issue. Grab a touch too much rear brake while turning and you’re cleaning wounds. You’d be foolish to live with this. Engineers made a dozen calibration decisions to ensure the brakes don’t bite this aggressively.

question: are lever piston sizes different L & R? I just recalled that I bought UK shifters and switched hoses.

jlok
Posts: 730
Joined: Tue Jun 30, 2015 3:30 am

by jlok

Ok, you are right. Maybe change to 140 rear then.

I don't feel any difference between left and right brake lever/piston size, both sram and shimano.
Giant Propel Advanced SL Disc 1 / BMC TM02 < Propel Adv < TCR Adv SL Disc < KTM Revelator Sky < CAAD 12 Disc < Domane S Disc < Alize < CAAD 10

jfranci3
Posts: 373
Joined: Tue Jul 26, 2016 5:21 pm

by jfranci3

Looks like I answered my own question. Looked at SRAMs website. Calipers are the same, levers have different raitios. I’ll switch them over the winter.

Edit: it's either a piston or "bias spring"

jlok
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Joined: Tue Jun 30, 2015 3:30 am

by jlok

care to share the link pointing at "levers have diff ratios"? it's interesting and it means the levers are not meant to be LR swappable.
Giant Propel Advanced SL Disc 1 / BMC TM02 < Propel Adv < TCR Adv SL Disc < KTM Revelator Sky < CAAD 12 Disc < Domane S Disc < Alize < CAAD 10

TobinHatesYou
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Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

jfranci3 wrote: ↑
Tue Sep 11, 2018 1:44 am

Yeah, no. Calibrated hands don’t work in a calibrated fashion when you’re startled and they should be that easy to lock on flat, dry pavement with lower pressure, good tires. A simple $40 fix should make things much forgiving and safer. I clearly have a lot more power than I need and I live in a flat area, so I don’t need any the heat capacity. The F & R brake efforts should be somewhat consistent on a hydro system.
I haven’t had issues on any other bike, this combo seems to be an issue. Grab a touch too much rear brake while turning and you’re cleaning wounds. You’d be foolish to live with this. Engineers made a dozen calibration decisions to ensure the brakes don’t bite this aggressively.

question: are lever piston sizes different L & R? I just recalled that I bought UK shifters and switched hoses.

A correctly bled and dialed in SRAM HRD brake system simply does not behave as you say. I still don’t know why you wouldn’t just dial out the contact point adjuster on the lever.

Also no, the levers are 100% interchangeable.

jfranci3
Posts: 373
Joined: Tue Jul 26, 2016 5:21 pm

by jfranci3

TobinHatesYou wrote: ↑
Tue Sep 11, 2018 2:30 am




A correctly bled and dialed in SRAM HRD brake system simply does not behave as you say. I still don’t know why you wouldn’t just dial out the contact point adjuster on the lever.

Also no, the levers are 100% interchangeable.
Looked at parts diagram again, you're right there's no biasing. Didn't see the contact point adjuster. Will have a look.

Edit: This is only on Red-eTap.

sennder
Posts: 66
Joined: Mon Aug 08, 2016 12:13 pm

by sennder

I almost never locked my rear wheel with the cheap no-brand dual caliper brakes on my aluminium road bike. When I first started riding my Trek Domane with direct mount Ultegra brakes, I was locking the rear wheel all the time simply because of the increased leverage. Now, I only ever lock the rear wheel on really dusty roads. On the flip side, on my commuter with disk brakes and reasonably knobby Schwalbe Marathon 28c tires, I've only locked my wheel deliberately.

I think locking the rear wheel depends much more on the tires and the rider+bike weight than it does on the type of brakes, at least once the rider is used to the brakes and levers.

--Sennder

cyclenutnz
Posts: 777
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Location: Cambridge, New Zealand
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by cyclenutnz

Tried today. Grabbed a handful of rear brake - got a lot of noise but no lockup.
Chorus H11, 28mm tyres (measuring at 32) and quite a lot of weight on the wheel (unfortunately).
Simply doesn't have the stopping power to cause a lockup.
http://www.speedtheory.co.nz
http://www.velogicfit.com - 3D Motion Capture and Frame Finder Software

by Weenie


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