Brake LEVER Force Measured
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- čas přidán 19. 05. 2024
- Ever wonder exactly how hard your brake levers are to pull? Well, we've got answers. Bike pseudoscience in this video.
This video measures force required to pull various levers, which has an effect on brake lever feel. It definitely does not measure any type of braking power.
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I hadn't any idea that the drop-bar brakes required so much more force than the straight-bar ones. This is great! Thanks! (...and close-enough science is close enough.)
Hey, man! Cheers from a fellow mechanic enthusiast from Bulgaria. This topic is very interesting to me, and I was going to comment on the recent podcast of You and Russ but never found the time.
In my opinion, the cable-actuated drop bar brakes are bad because of a messed-up cable pull ratio. I'm pretty sure that manufacturers know about this and do nothing to address the issue because it promotes the hydraulic options better.
So, let me tell you a story - A few years ago, I was building my first disc road bike (winter & commuter) and I mixed my existing Shimano ST-2300 levers with Avid BB5 Road calipers. All was great, and the stopping power and lever feel were more than adequate. Later, I switched the calipers to BB7 Road (just for the bling and extra adjustment). Again - all great, brakes felt even better. I rode this setup for a few years, and finally, I decided to ditch the ST-2300 levers and switch to the newer generation ST-R2000 (this is a 3x8-speed bike, and I plan to keep it this way as long as possible). After switching the levers - Oh My God - the brakes felt awful! Way harder to press and so much less stopping power. It was night and day compared to my previous setup. I then decided to investigate the matter and found that basically all Shimano levers since the first gen with hidden shift cables had increased pull ratio for the brakes. And the increase is by a lot, something like 1/1.7 (old/new levers). No wonder the same calipers worked well with the older lever and worse with the new ones. I then decided to try MTB calipers (also known as long-pull or V-brake pull). I installed BB7 MTBs for the sake of testing, and guess what - this combo is the best brake I've ever had.
Long story short, on this and a few other bikes, I tried a few more levers and calipers afterwards (Shimano BR-RS305, TRP Spyres, etc.), all felt like trash with supposedly compatible levers - the latest gen Shimano STI's. I even tried to increase the pull ratio of a Spyre by grinding the ball ramps inside with partial success, but I don't like this brake anyway (too finicky and small internals that are IMO not suitable for purpose).
So in summary, my thinking is that the latest mech STI's have a much greater pull ratio than the old ones and are very close to the V-brake levers. Many mechanical calipers are built around the older (shorter) pull ratio; some newer models are somewhere in between (for the sake of compatibility with old and new levers), but that just makes them not perfect with either levers.
My winter bike has the BB7 MTBs for a few years now, and this combo is the best brake I've ever had in my life. I've had a few different Shimano hydros on one of my other bikes (Ritchey Road Logic Disc), and believe it or not - the mechanical combo is better, at least for me. This spring I switched the Ritchey to mechanical brakes too - trusty BB7 MTB up front, but the rear was a big problem because of the flat mount and the close proximity of the seatstays. You may know that for a PM caliper to fit with the proper FM-PM adapter, the seatstays need to have enough clearance, and this is a problem with some Flat-Mount frames. I rode with a Spyre out back for most of the year, and I can tell you - this caliper is a joke in comparison with the BB7 MTB up front. I had the idea to modify a PM BB7 caliper to fit on the FM mount of the Ritchey, and I recently did the mod, but it is still in a kind of testing phase (bad weather, so I ride another bike).
As I said, this matter is very interesting to me, and I encourage you to do more testing and compare the pull ratio of levers and calipers. I can show you pics of disassembled levers of the two types; you'll be amazed at how different the ratio is.
Best regards, Marin
This sounds fascinating and I want to make sure I got it right. You are saying that with Shimano ST-R2000 short-pull road bike levers you find that Avid BB7 MTB long-pull calipers work well, and that you suspect the reason is that modern levers like these have a different pull ratio compared to older levers like the ST-2300?
I'm rather ignorant on the topic, so I'm wondering whether it's possible that the issue isn't in the pull ratio but instead it may be about the distance between the pivot point of the lever and the place where one typically presses on the lever. If the newer ST-R2000 levers shorten the distance between the pivot and the fingers on the lever, that would make the lever feel "harder" because of the lower mechanical advantage. By switching to brake calipers with a longer pull you recover the mechanical advantage that you had lost with the newer levers. Do you think this could be what's happening?
It would have been nice to have some kind of force sensor in the caliper and measure how much force it took to provide a set amount of force on the pads. Seems like there isn't a ton of variation for most of them in terms of force to move the lever, but if you're stopping before you hit the rotor, then you aren't really measuring how much force is required to stop the bike, which is the important part.
Haha me and some of my students are working on exactly that test bed.
@@TheBikeSaucejust wrote a comment about that.
I would want to see the force required to lock the wheel from spinning at a stipulated average speed and at a torque derived from a simulated system mass traveling at said average speed, all using the same brake pad and rotor. Great video!
Thanks for this. A great data backed validation of how superior those growtacs are. They can be fiddely at times for sure, but once dialed in I just forget about them. I also use them on my Outback BA and love the modulation. I’ve had doubts about migrating to hydraulics as well but not anymore. Why bother.
Great info as usual! BTW, your son's bike is totally cute!
Merry Christmas Mr sauce
Never would have guessed! Thanks for making this kind of stuff 🙌
Right on! I wanna try that brake ace sometime 🤘😀
That was cool. Interesting for sure. I just looked at my Cannondale. Has Shimano rx100. I love those rim brakes.
Very cool, i was thinking about testing this very thing and you beat me to it! I kind of find hydraulics uneccesary for most people. I have an old mtb with cantis/drop bars and the brakes feel fantastic. It all depends on the setup.
This was _nerdily_ informative.
Ive been coveting info & feedback on the Growtac Equals. I'd love to hear your further anecdotal thoughts on those.
I’ve got that video on my list 👍
@@TheBikeSauce many, many thanks. I'll be looking forward to it. (Also not ashamed to say how much I envy you w/ that Outback. That's an aspirational bike for me.)
Love the test! Reflecting on bad drop bar experiences with Spyres and BB7, I reckoned the leverage on the brake levers from the hoods is poor from an ergonomic perspective since you are pulling towards the palm. Flat bar and in the drops, you pull towards the thumb which feels much more powerful. One third the leverage adds to that problem . Grip strength testing from different positions could be a fun addendum to the series.
Nice testing! I know you're limited in the amount of brifters you can test but I would be most curious about GRX-di2 levers. Those have the best feeling braking to me and I would be curious to see if the data backs that up or not.
I totally agree!
Just watched & found it very interesting. How much difference do you think different cables would make?
Hey, that's a really interesting thing to test and the methodology is reasonable enough. I don't know how I would set up the experiment but I would be interested in quantifying the force required to stop wet carbon rim brakes from the drops. It certainly felt like tons.
Yea a comprehensive brake study would be awesome. Certainly would require more than an afternoon garage video session 😀
I'm curious if you would achieve the same figures if you used the hanging bike weighing scale and yanked on the levers instead of pushed on them.
Happy holidays!
If the scales were 5kg max then pull would be better
I recently picked up my first drop bar bike with hydraulic brakes (Rival AXS) and immediately noticed the higher force required to engage vs the mechanical rim brakes (SRAM double tap and shimano Dura Ace) than I had previously been used to. I am still having a hard time adjusting to this as I have been hearing people raving about hydraulic brakes for years. Honestly the feeling of my rim brakes were just as good if not better than the hydraulics.
The lower force required to engage in the drops is probably due to the increased leverage from the end of the brake which probably correlates to the similar leverage point on the flat bar brakes.
Not probably, definitely proportional to the lever arm
Hmm should I swap out my spyres for hydro on my old diverge? Or try these gro-tachs (sp?)
The Growtac Equal is installed with the tip of the brake lever pointing more sharply backwards compared to the Shimano and SRAM system. And we know force required to do work is inversely proportional to the distance of the applied force from the pivot in a lever system. Have you controlled for the potential difference in distance between the hand and the pivot in the drop bar brakes? Because if the leverage is longer for the Growtac that’d explain the why it was requiring a lower force than the SRAM and Shimano.
Lot to unpack here. But yes, I tried to square the scale to the axis of rotation on each lever. For the drops, I pushed right where the dip is on all levers. The levers are essentially the same length, but the discrepancy may be that the pivot point on the r7000 is at a different location than on the grx, which would change the effective moment arm.
Nonetheless, in a natural riding position, the growtacs with r7000 levers are lighter action.
Are those R7000 levers the same model that are sold for the rim brakes?
Interesting testing. Curious what a standard road rim brake would come out as, I assume higher than the disc brakes based on my assumption that assumptions are just assumptions.
Makes sense that the drop levers are designed for optimal braking from the hooks. If they were easy to pull when on the hoods they'd lockup or have no modulation from the drops. state's brakes... yikes
Any chance we could get the 3d print file so we can test our own brakes at home?
I think that's pretty on point with the grotacs as one of the main review comments seems to be that they are powerful but very off then on. Some small bit of lever resistance is useful in allowing you to modulate the pull since hands over bumpy terrain aren't the most precise machines.
Regarding v-brakes a lot depends on the tension of the spring that is human-adjustable for each of the break arms, so I think this would need dedicated movie to be able to draw conclusions 🙂 From my experience a lot of bad reputation of v-brakes and cantilevers is because of misadjustment.
That's brake.
Wow, the imperial system sure is confusing. How are ounces used for volume, mass, and apparently force? Other than that, super interesting video!
😆 was waiting for this comment. Fwiw, kg is also used for mass and force, just not volume.
@@TheBikeSauce I noticed you used kgf, I don't think I've ever seen that before. The SI unit of force is Newtons
Haha! The Science hat!!!
😀 it comes out once in a while
Growtech brakes look impressive. Only thing is price is very steep.
I was scared about going from rim to disk BUT even the GRX 815 with the extra leverage our not that powerful
Im legitimately confused about this comparison. Braking force is a combination of the force multiplication of the lever/caliper as a system, combined with friction of the pads on the rim/rotor in motion.
What on earth is even being measured here for comparison? I mean if you put a high friction brake pad you could stop with much less finger effort.
😆. Yea there’s no braking power measurement here. I was just curious how hard some levers are to pull. I explained that the measurement is taken just before the pads contact the rotors.
I’m not sure if you were measuring the right thing. The force you measured to make the brake pads touch the rotor is your spring tension. You can replace the spring with a more r less stiff one and change that force. Not related to brake power. Brake power depends on
1. Spring pull
2. System loss
3. Ratio of lever to pad movement (before brake engagement)
If you measure the force on the lever needed to keep the bike still while the bike is being pulled at a certain force, subtract the lever spring pull, multiply by the ratio of lever movement to pad movement (measured separately) and take off the losses, you get the brake power. It will be more complicated for a brake that has servo movement like the new shimano drop bars.
An easier thing to do is to apply a certain force to the bike: this could be a certain weight you hang from a pulley (on a fixed location) and the string is pulling the bike horizontally. Then measure how much force you need to apply on the brake lever to keep the bike still even though it is being pulled by the string. Come up with a table showing the results for two or three weights.
Again, we weren’t claiming to measure brake power. Simply brake lever force, which affects braking feel to some degree
@@TheBikeSauce thanks. I am waiting to see how you like that Polygon Bend.
Easier to pull to engage or better braking?
This experiment only measures force required for pulling to engage. We do have an experiment in the works for quantifying braking power
I love your content. Thank you for what you do
@@TheBikeSauce But does it?
If you wanted to approach this with a slight bit of scientific rigour, you would need to install a load cell at both the caliper and lever to measure how much force at the lever is necessary to create a set amount of force at the caliper. Even then, you need to define what force you are looking for at caliper, and why that amount matters. Simple engagement is not the same as peak force required at the lever. Perhaps a better metric would be force required at caliper to stop system weight of Xkg from speed Y in time Z. It's still complete junk science, but at least you have a relative comparison to draw a conclusion from when you can quantify the resulting braking force for your efforts at the lever.
What you've done in the video does not take into account any of the variables (force multipliers and pull ratios, for one. E.g. servo wave) and is highly skewed by how hard you pushed on the scale. Since you can't even see the calipers, you're entirely reliant on your ability to both "feel engagement" through a scale and 3d print part while at the same time trying to read the scale. My personal experience with brakes is that initial engagement is heard before it is felt, and there's basically zero perceived deceleration at that point. You can also pull as hard as you want on a lever but that doesn't correlate to more usable braking force beyond the point a tire locks up. With a bike in a stand you have zero idea if you're applying lockup force or normal braking force. Without a braking load it's really pretty useless to anyone.
Thx for your input, but let’s back up for a second: the video is called brake LEVER force. Merely measuring tension in various braking systems because it affects lever feel a great deal, but it’s not a quantified specification in the bike industry. Video isn’t claiming any more or any less.
I've wanted to measure shifter down change force for a long time, one of my deore 10s shifters needs 1kg+ which makes for a terrible ride
Not measured was the force required to stop an x kilogram rider from x kph in x distance. Bigger rotors help as well as big soft compound tires and a bike that doesn't flip.
🎉
Is the difference you measure noticeable by an adult and does the data match the experience?
Difference between deore and SLX was negligible in feel. Everything else agreed with the numbers
Let’s hope there aren’t extra pivot points in the levers.
Drops use less force than hoods because of more leverage
👍 and should be inversely proportional to the lever arm
😂tell me how many bikes you have without telling me how many bikes you have!
😀 is this what call a ‘subtle flex’?
Thanks so much. Confirms the feeling of budget minded cyclists that Deore and Tektro are the winners. Fascinating that the Grotac brakes confirm something the alt cyclists have been claiming, dropbar brakes don’t have to go fully hydraulic. Overall we could be offered simpler mass produced systems at a reasonable price on all bikes but the industry doesn’t want to lose the higher margin products.
A bike with only rear brakes? That sound wrong. Only front brakes would give you a lot more stopping power.
your not really testing the force needed to stop the bike, you’re testing the tension on the return spring. you need to normalize for pressure into the rotor.
Explicitly stated we’re not testing brake force 😀. Just brake lever force
I commend the inquiry and the effort, but I think your measurement technique is entirely flawed. You pushed the lever to a point you *thought* was adequate, but how much braking do you get from that effort? You need to set a baseline which yields a given amount of braking for each brake so you can compare the forces required at the lever. You probably pressed until you reached a point of steeply increasing effort but that does not translate to any given amount of braking, especially since the various brakes you tested have such different characteristics. I could be wrong, but this is how it seems to me. I think to make this a valid test, the bike’s wheel should be spinning a drum such as on bike rollers, and the bike rollers need to measure the amount of deceleration somehow. When it reads a certain amount of deceleration, it is at that point that you should measure the force at the lever.
Thx for the feedback! I get what you’re after, but this test is only measuring brake lever force. Basically just the nominal tension in the system. Nothing to do with braking power.
@@TheBikeSauce OK then what effect does that tension have on the cycling experience? And how did you limit the amount of force you applied? In other words, couldn't you have squeezed the heck out of the lever in each case? So you pressed with less than a "heckful," so how much did you squeeze, and what does it show us about the different systems?
I believe that tension in the braking system has a great effect on the ride experience, despite not being a formally discussed metric. The hypothesis is that reducing brake lever tension frees up hand strength for modulation.
The experimental process was outlined pretty well: articulate levers to relieve any stiction, square the scale to the lever, zero the scale, push and hold in static equilibrium until just before the bite point, record the force.
Again, not precise science by any means, but confirmed a couple of interesting results nonetheless.
@@TheBikeSauce OK I think I understand now. I believe it is true that reducing the required pressure frees the hand to modulate well as well as giving more braking power to those who are not strong enough to fully engage a brake that requires a lot of pressure. Thanks. I enjoy your videos very much.