Are Disc brakes Slower? Rim Vs Disc Aero tested. 

I think cross wind performance and measurement would be much more beneficial. Most people slow down if they feel the cross winds are jerking their wheels around--that would affect speed more than anything else.

Low CdA mate. 53mpg+. Remember the Volvo estate in BTCC? Was it banned for being too quick?

​@@PeakTorque A load of tosh, that CdA is going to be way worse than my car! It's because you are contributing to lung problems for the masses with your diseasal. for our next video powerpoint reaming I think we should have "Cycling RU-vidrs and what they drive". I think the masses would be hooked.

I was disappointed the bikes weren’t in the TR6.

@@Gregory_tottie Thule disappointed ?

The Merc has discs, front and rear. Just sayin’. 🤷‍♂️

But everything else is different! Wheels, frame, bars… can’t drive any conclusion

Watch mine then. 2 riders then swap bikes each lap so wind and air pressure is IDENTICAL.

Speak for yourself ❤️😆. Some of us ride over 25kph and use race tires. Road disc IS slower and more dangerous.

@@durianriders what? I also ride above 25kmh and use race tires. I actually race. For over 10 years. So yeah my opinion but more dangerous? What? Only for the hamfisted and those that lack skill. Get good.

Disc brakes: extremely dangerous

Glad you liked it!

+++

There has been a noticeable historic tendency for roadies to aim to emulate the look and equipment of the pro's, this has got to the point now with tech advancements where many riders end up with equipment barely suited to their real usages - or more specifically a higher degree of wasted 'needless' performance. I'd like to see a definitive split between ProTour level race bikes and a more realistic alternative marketed towards keen enthusiasts...without it having to tend towards the old-man comfort bike - a sort of 'classic' Tour bike with an emphasis on ride feel and enjoyment.

Isn't that why we're here? We love all this minute detail.

@@PeakTorque Oh don't get me wrong. Your videos have probably saved me $1000's by not buying shit that really won't help me. This probably isn't helpful if you are looking for sponsors though. :P

They can only get marginal gains now. That's just the reality of engineering within UCI rules. As for pricing, it's hard to say they care that they're pricing people out if people are still buying their bikes in mass. *Also, PT noted that his fit between the two bikes may be enough to throw off the data anyway

Practicality. Ive Tested no front rotor and the difference is within the error bar (about 1.5w at 35kmh). A partner has also tunnel tested it up to 55kmh in a tunnel. Am under NDA on that, so say no more.

@@PeakTorque PTwheels inc?

That's the main point on a comment I just posted. The 2 bikes are too different to isolate the braking system impact!

Despite the advertising fluff, the fact that you don't lose watts, but get better breaking gives the win to disc brakes. At least with comparing these two bikes. I'd also like to see a similar test done with two bikes without so much cable housing. Even the disc bike in this scenario has plenty of cable housing showing.

You have so much apple and bananas differences between those two bikes that you can’t drive any conclusions. The rim brakes has an aero bar… but it’s wider (probably the biggest I pact since rider will generate a lot more drag), rim brake has a different rim height, and has exposed cables, cranks are different… we have no idea how this add up.

How many rim brake riders you at the side of the road with a brake problem? Rim brakes on road bikes FTW! 😱🫠🐸😎

Heloooo 😂

Credit to the Dark Install. Rest his soul.

I doubt this setup would be able to measure a difference there, that's an effect another order of magnitude or so down from this.

My rim brake bike with tubular carbon wheels brakes as good as my disc bike in dry weather and I get consistency with my rim bike as I have days of terrible front end disc braking due to contamination until I clean off the rotor. Where my disc bike ultimately wins is the all weather braking and long life of the rims

The Rim Braked Bike had the slower tires, wheelset, handlebars, and cabling, and the rim brake bike still won. If you don't believe me, then you are welcome to do the test yourself.

I agree. And the aero data from your magazine can support this-for example, the rim brake madone was a few watts faster than disk madone (in a wind tunnel, that is). There are a couple more examples. R&D on rim brakes is almost non existent it seems. Those integrated rim brakes were also a pain to work on though, and as PT says, disk brakes can be faster due to late braking, confidence, and relaxed upper body on descending. They also permit more complex wheel designs and contours. Though I would love to continue seeing TT bikes with aero rim brakes with development there, and I think this will continue… just not on road bikes.

Front rim brake still got cable exposed.

Yeah, that's why all new high end bikes have fully integrated cockpits and an aero monobar. That's the sector where they had the largest gains left. I mean the result is - discs are only a bit worse. Probably not too surprising considering their position on the bike and the relatively small size of the disc. Also they try to hide the breaking mechanism behind the fork which helps. But since all they do nowadays are marginal gains it's funny that they force everyone on discs. I mean with discs they can make the bikes more expensive, the maintenance is more costly, fewer people do it on their own and most important point - they had an argument to sell new bikes to people who already had great ones and there was no real performance gain anymore.

.....wind tunnel a good reference, but often real world results are different. Unless a pro racer, I have serious doubt anyone is beating all comers who ride disc vs rim......

Speculation. Its still almost square shape.

That's why i don't really trust tunnel data at these lower speeds. There's too much swirl in the real world, and the results are less flattering.

basically

The yaw is fully dependent on the wind direction, not the equipment. I'll get in touch with the engineer at Aerolab to ask about yaw error but i imagine it about a tenth of a degree.

Not really, his CdA is approaching 0.400 m^2. That's quite high for an aero-aware road cyclist. A pro cyclist of average height will be closer to 0.300 m^2 if not lower

I'm 195cm and 90kg. Most tests run around .38 on the hoods, elbows slightly flexed. Pretty good for my height.

Good call! Pile of buttons, it was after that.

You're not wrong, but fortunately 'accuracy' is not the same as repeatability. That's why we do repeated runs! And there does seem to be some bias in terms in favour of the disc bike, albeit very slim.

@@PeakTorque Great research vid by the way, it is quite interesting to see some independent real world riding data. However, statistically speaking, I'm not sure if 10 laps is enough data to favor even a small bias when the results are within 1% of each other and the measurement devices' margin of error is at best +/-1%. If you were to do a bigger sample size there is a good chance that small bias could flip. Not trying to torture you man, I just find the discussion interesting. Cheers!

Price and maintenance are moot points in reality. The majority of cyclists entering the market, and thus will eventually dominate the population, are covid era cyclists. These folks have 1) cash to burn and 2)self-maintenance offers a low return of investment for time spent. As such, money ain’t an issue, and if there are any issues, it’s the mechanics problem to deal with, not theirs. So they have every incentive to use whatever is cutting edge in cycling, regardless of the time or servicing technicality.

@@slowcyclist4324 Ahh gee! How could I miss the fact that cycling isn't about seasoned riders who are passionate about the sport and log in thousands of miles each year but actually cycling is about the covid era cyclist who just picked up the sport and hardly rode a few Ks of miles during the pandemic because he/she found cycling fashionable during their "new normal". I probably walked into more bikeshops and dealt with more mechanics then you have seen browsing online. Without being a moot schmuck like yourself, I most likely spent way more $ than you have in cycling. A real cyclist who actually rides will benefit from maintaining own bike, knowing that every bolt is specced to torque and the bike is safe to ride hard. Dropping off expensive equipment to get serviced by random bike shop mechanics is a recipe for disaster, I know from first hand experience and not blabbering assumptions like you. Finally, only a confused pandemic era cyclist would think they have every incentive to use the "latest cutting edge" on their twice a week 30 mile rides with 15 mph average speed. These also happen to be the same group of people who claim that rim brakes don't stop but they think they can descend "oh soooo good" with disc brakes. Now go on and wear your $400 pink Rapha jersey which you put on every week and go on a ride. Stop by the LBS on the way back and buy a new bike since $ is no issue for you and you get to show how you dominate cycling with the latest and greatest tech under you. Good job Fred!

No, i would say that's the most important above about 20kmh!

Was the wind and air pressure the same each lap? Impossible. I did this test using 2 riders then swap bikes and average the data. Road disc IS slower.

@@durianriders Keep telling yourself that Durian and maybe it'll come true

@@durianriders You should test riding down a steep descent with no skewers in the quick release and see what happens

​@@durianriders you also said, that the Trifox X8 is a good frame for the value. But I chewed through 2 seatposts, the wrap on the fork was unwrapping itself from the getgo,, had to drill the front brake hole, at the rear the painting started to melt away around that hole, the seat tube and the post were so out of their intended dimension I had to use 2 and 3 layers of sports tape for the posts, yet the second one went down still and got stuck, ofc many tiny painting imperfections (I cpuld live with them actually), but no warranty, very bad customer support. So I am glad you had good experience with that shitbox Trifox, but I would seriously reconsider recommending it without mentioning all the problems which that brand has.

I used to be an Airbrush/tattoo artist. That was a lie

I can't wait for the industry to make a U train on Disc brake bikes like they did with threaded BBs...

😎. Practicality of doing these tests in winter without being paid. Is the answer from me 😎

@@PeakTorque @Peak Torque yeah no obviously not practical at all. Although my impression that I am getting from the result of this test is... Alll things being equal between the two bikes equipment wise, the Disk brake equipped model should be a hair faster.

Its a nice video but from a science point of view it is flawed given the differences between the bikes.

@Teakhead Al that isn't how science works.

Disc brakes are heavier and harder to service , maintain, noisy ect and ugly I don’t understand the appeal

@@KushPizzaSleep piss easy to maintain, work significantly better (even more in the rain), don't wear out your wheel. I'll take the wee bit of weight over better braking. only thing I hate about road discs is the price.

@@MTBScotland disc brake bikes are quite a bit heavier and hydraulic disc brakes are a pain in the arse ask Chris froome. Total over kill on skinny tyre road bikes but it’s a world full of all the gear no idea morons

Interesting test - new wheels, new bike or just a new aero helmet?

Aero enough helmet, tall lycra overshoes and 45mins in the shower with the Bic.

@@nellyx1x493 love it! Yes Nelly!

New helmet for sure. Clothing and body position are the most important factors in aerodynamics by far

As tested with all the slight differences in set up, the disc bike was slightly faster. To go 35km/h it required 1.7w's less which is tiny! I don't know about you but I ride at about 31km/h on the flat. Extrapolating up to 50km/h with equations, it would take about 4.8w's less to maintain this speed on the disc brake bike. As stated, a slight adjustment of body position would more than account for these differences.

Cheers. Obvious but theres always that niggle of doubt when it comes to air... that has now been eliminated.

He isn't even a patron. What a douche

Tell us how road disc increases traction in the wet? Why so many more crashes now in wet races with road disc? Tony Martin retired because it's 'just ridiculous out there now'.

Geez, that'd be getting to some epically marginal gains :)

I dont like to speculate as you know but that would 99% chance be WELL inside the error margin!

Its white until it rains, then it goes grey and sludgy and ruins everything!

@@PeakTorque Perfectly said-turns out cycling is made up of more gray areas than marketing shills or old-school purists would have you believe

Narrow is faster aerodynamically. But then there’s rolling resistance on less than perfect roads to think about, which is why modern wheels are getting wider.

@@lukeh3020 Yeah, the roads in Adelaide are so fucking shit. But about 100 pot holes a ride and it’s hit them or a car. I am thinking of zipp 303 firecrest, light and good crosswind stability and good price.

It's also dependent on the rim's external width. No two 21 mm internal rim width rims are the same. The Rapide CLX's front rim is a lot wider than the CLX 50's. There's also the 105% rule to follow, most easily done with Goodyears.

@@yonglingng5640 what are your thoughts on 303 firecrest with 25mm internal

@@jarrodfife242 With Zipp fully committing to disc brakes and tubeless (except for 303 Firecrest Tubular, 404 Firecrest and 808 Firecrest, the latter two wheelset can still run clinchers), I'm very much less fond of them now (never was a sucker for Zipp wheels) due to them going 25 mm internal and hookless, so in my opinion, they're only best for riders who fully prefer riding tubeless. Because of the tubeless commitment, the running costs of almost all of their wheels aren't cheap.

Speculation.

Speculation.

@@PeakTorque I think the differences are so small it could overall make the difference I was shocked it was so close as the newer tcr is meant to be more aero... I remember when GCN did tests back when John was on the show with 2 identical pinerellos and the rim model was faster across the board 🤔 Great video enjoyed it I've had a disc and rim tcr myself but prefer the rim one by a mile 😂 but that's me

the rider is always going to be the heaviest and dragiest part of the equation, and component differences are always going to be small, but folks keep spending money on the things underneath them hoping itll make em faster, at least placebo is measurable.

Yes, but the bike as a system doesn’t change in aero performance because of fatigue etc. you, as a rider, are way more inconsistent. Your weight fluctuates, your posture changes as you ride, and your clothes also changes depending on what’s in the wash. So, if I have a constant variable that will never change (aka the bike) doesn’t it make more sense to fully optimise that consistent factor, over a variable like posture and weight which changes consistently? In short, money spent on an aero bike/equipment is actually the best investment you can make. Your body comes next, as that comes over time and changes constantly.

The best bang for your buck is tyres. Way more savings there than the difference between wheelsets/frames.

@@PeakTorque that is true. That said, inevitably when you’ve gotten your wheel/tyre down( because in all seriousness how long can that take?), the next area for investment should be your bike frame.

@@PeakTorque only interms of rolling resistance, or do you think that width (25mm vs 28mm same tire model) is also important for aero gains?

Not much global in it. There's an Irish guy... 😅

Brilliant reframing of the GCN name