Tire Grip | EXPLAINED

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  • Опубликовано: 5 июл 2020
  • What is up with tire grip? Why do wider tires have more grip? The answer is not what you think. Does the contact patch area matter? Why is it important to understand that tires are viscoelastic?
    Lets figure out the Dark secrets of tire grip.
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Комментарии • 476

  • @sferreirac
    @sferreirac 4 года назад +368

    Damn, as an engineer I feel ashamed for not questioning the theories used on those videos mentioned earlier now. That's very enlightening overall, love your videos, keep educating us please.

    • @GraymatterPix
      @GraymatterPix Год назад +2

      My thoughts exactly. Although I'm no longer working in engineering, that was what I studied and F=uN was my explanation for tyre grip. I'm glad I watched this before buying a spring balance and setting up an experiment to make myself look daft.
      Just goes to prove that "a little bit of knowledge can be a dangerous thing".

  • @ziqijia5203
    @ziqijia5203 4 года назад +456

    while other youtubers talk about high school physics, Mike starts to explain the materials science. Good.

    • @user-mg4ph8ee8y
      @user-mg4ph8ee8y 3 года назад +8

      well still just enjoing the fact of understanding only 1% of the material xD

    • @unclenickynvp5074
      @unclenickynvp5074 3 года назад +2

      Blessed comment

  • @Gersti96
    @Gersti96 3 года назад +50

    Seeing someone correct Ryan slightly broke my heart
    But in another video i remember him being a bit more precise than in that dark side video

  • @khawajadotd
    @khawajadotd 4 года назад +141

    THANK YOU!!
    I've been looking for years for a good summary on this topic, because tire grip is such a misunderstood topic. Now I have finally have a reference to point people to when they regurgitate myth.

  • @johnhoolihan9452
    @johnhoolihan9452 3 года назад +11

    I’m a mechanical engineer turned musician and I have never heard such a thorough description of motorcycle tire dynamics. Well done!

  • @WiltshireBornandBred
    @WiltshireBornandBred 3 года назад +7

    Speaking as a former tyre test development rider, it also needs to be pointed out that upping tyre sizes, even from the same manufacturer & model, rarely gives more grip at the contact patch is defined by the tyres vertical stiffness, lateral stiffness, & rim produced profile. Often 2 tyre sizes have differing vertical &/or lateral stiffness, & the larger tyre may well have a smaller contact patch area on the same rim, as tyres can be fitted generally on approx 5 rims sizes and their vertical/lateral stiffness, contact patches upright, & leant over, profile, grip, & feedback will be different on each rim. Shape is everything

    • @falcn12
      @falcn12 11 месяцев назад

      Great point.

  • @Arkoss
    @Arkoss 4 года назад +80

    I don't really leave comments on such big channels, but I feel that the like button is not enough here.
    Thanks for taking the time to do such informative videos, and describe complex topics so simply. Even though they might not get as many views as I dunno, supermoto contentent, there's people that really appreciate what you do!
    Your's is one of the few channels that I don't miss any video from. Keep it up!

    • @StellarStreak
      @StellarStreak 2 года назад +1

      I've discovered this channel recently, and I'm hooked. The research that goes into his videos is staggering.
      This channel gives similar vibes to another channel albeit on cars i.e. "Engineering Explained".

  • @BraappMalaysia
    @BraappMalaysia 4 года назад +61

    If this a actual film, out in theaters. I would watch it together with my lady. 😂 you had me at opening vid

    • @Quazacolt
      @Quazacolt 4 года назад

      hey holla fellow Malaysian! :D

  • @saikosuku_trial6215
    @saikosuku_trial6215 4 года назад +31

    When the bubbly music comes on I know I’m gonna learn something🤔. Thanks Mike.

  • @Bothermewithdetails
    @Bothermewithdetails 3 года назад +1

    Every motorcycle rider needs to study this channel over and over.. you are spoiling us my friend thankyou for the information on riding

  • @alexvondergulasch1500
    @alexvondergulasch1500 4 года назад +26

    Congratulations Mike, this is one of the best researched and set up motorcycle video I have ever seen! Greetings from Germany, keep up the good work! I always learn something. Kind regards, Alex

  • @cetusrojo
    @cetusrojo 4 года назад +4

    I had this doubt for years, and didn't find satisfaction in any other answers before. You are such a great teacher!

  • @levgtz7814
    @levgtz7814 3 года назад +18

    “Based on real empirical data”. That sentence is really profound. Great!

    • @DumbledoreMcCracken
      @DumbledoreMcCracken 3 года назад +3

      Many "engineers" think the equations they learned dictate the behavior of real physical systems. Those equations are only applicable to a narrow set of conditions, and nature is free to generate data that is in disagreement with the (simple) equations, given the limited applicability of the equations.
      My hypothesis is that Germans are taught that electrical systems behave as per the aggregate of manufacturer's specification, and design fragile systems based on the inability to imagine corner cases. That's the only way I can imagine the stark difference between German electrical systems and Japanese electrical systems.

  • @undisputedt4604
    @undisputedt4604 3 года назад +6

    9:08 when you head matches the tyre profiles and your explanations. This man speaks the truth

  • @MikeonBikes
    @MikeonBikes  3 года назад +84

    Some references for the curious:
    The Racing & High performance tire, Paul Haney, 2003
    Motorcycle Handling and Chassis design, Tony Foale, 2002
    Motorcycle Dynamics, Vittore Cossalter, 2006
    Car suspension and Handling, Donald Bastow, 1993
    Chassis Engineerings, Herb Adams, 1993
    Competition car suspension, Allan Staniforth, 1988
    Drive to win, Carroll Smith, 1996
    Engineer to win, Carroll Smith, 1984
    Fundamentals of Vehicle dynamics, Thomas D. Gillespie, 1992
    Mechanics of pneumatic tires, Samuel K. Clark, 1978
    Prepare to win, Carroll Smith, 1975
    Race car aerodynamics, Joseph Katz, 1995
    Race car vehicle dynamics, William F. Milliken and Douglas L. Miliken, 1995
    Science and Technology of rubber, Frederick R. Eirich, 1978
    The physics of Tire traction, Donald F Hays and Alan L. Browne, 1974
    The Shock absorber handbook, John C. Dixon, 1999
    The Tire pavement interface, Marion G. Pottinger, 1986
    Tires, suspension & handling, John C. Dixon, 1996
    Tune to win, Carrol Smith, 1978
    Vulcanization of Elastomers, G. Allinger and I. J. Sjothun, 1964

    • @duane6343
      @duane6343 3 года назад +7

      I'm reading Motorcycle Dynamics at this exact moment! As a tire nerd/material scientist/chemist/mechanical engineer/former racer, thank you SO MUCH for making this video. Tires are so under appreciated, they're all just black and round right? This video is already in depth, but only scratches the surface of the complexity. Could have added (and probably way too technical) the Loss Modulus and Storage Modulus based on temperature (such as a DMA graph). Which is a discussion on glass transition temperature/rubbery plateau/flow region to demonstrate exactly why operating temperatures are so critical to tire operation, tire warmup, and over-heating. It would also be cool to see a comparison of a 190 rear on a 5.5" and 6" rear wheel. U vs V profile on the wheel, and contact patch at lean angle vs straight line stability based on that profile.
      Such a great video.

    • @tomdickharryjane
      @tomdickharryjane 3 года назад +1

      Wow, what a list! thanks.

    • @RedTurbocar
      @RedTurbocar 3 года назад +1

      What do I win if I own all of the above referenced?

    • @tomdickharryjane
      @tomdickharryjane 3 года назад +3

      @@RedTurbocar My undying respect and a whole lot of knowledge.

    • @lucysmith4242
      @lucysmith4242 3 года назад +2

      Ohhhh man I fucking love the Carrol Smith books. Have devoured all of them. Holy fuck you actually read Miliken? Clearly you are my type of person. I've also read Gillespie. If you get a chance read "Race Car Engineering" by Paul Van Valkenburgh. I may have misspelled it. His books are very similar to Carrol Smith's books, but it's interesting to see the same information from someone else's opinion.
      Got a new subscriber by the way

  • @bondedtruth6317
    @bondedtruth6317 3 года назад

    Thanks a lot for this video. For me personally, your channel is one of the most educating channels to learn and have a proper understanding of bikes.

  • @hunterhealer8022
    @hunterhealer8022 3 года назад

    Underrated channel. Motorcycle grips as with other things in life, are not always as simple.
    Thanks man

  • @TheBigdutchster
    @TheBigdutchster 3 года назад

    Rarely do I come across something so well and thoroughly explained. Thank you greatly.

  • @MaxShpirka
    @MaxShpirka 4 года назад +4

    This video earned my subscription. Never thought about tyre slip in corners. Though I could see semi-circles on the edges of a new tyre that I slowly break in. I suspected this was due to tyre slip in corners, but was not sure how it really works.

  • @ropro5402
    @ropro5402 Год назад

    Okay, this is one absolutely oustanding video on tires! Exactly answers all the questions and doubts I had. Thank you for sharing the knowledge!

  • @firebladeadam
    @firebladeadam 3 года назад

    Love the technical understanding you have of the physics of bike geometry. And your McGyver T shirt. Rockin'

  • @noufaltariq
    @noufaltariq 4 года назад +36

    You are awesome, one of the gems in YT, keep it coming , love you mike.

  • @me73941
    @me73941 4 года назад +7

    The MacGyver shirt is classic!!! And as always, excellent video!

  • @Gkuljian
    @Gkuljian 3 года назад

    It just donned on me that part of the keying aspect relies on how rubber acts like a spring. Great video. The best I've seen on this subject.

  • @Ganzonx1
    @Ganzonx1 4 года назад +1

    MIKEEEE keep up the good work sir. This was very informative for me and my riding buddies. Thanks for helping us ride more safe.

  • @peterbigblock
    @peterbigblock 6 месяцев назад

    When you said, “Contact patch shape” I yelled thank you! The shape of the contact patch is so important. Same for car tires. It also has an effect on traction under braking and acceleration. Thanks for giving people the real scoop.

  • @sutrebloggentv756
    @sutrebloggentv756 3 года назад +9

    You prove Einsteins saying: "If you can't explain something simply it is because you don't understand it well enough." Now even I understand it better.

  • @coopertrooper87
    @coopertrooper87 3 года назад +1

    That was EXCEPTIONALLY informative! Thank you! Brilliant content! 👍🏻👍🏻👍🏻

  • @braackw
    @braackw 4 года назад

    Very informative video. Gets to show that friction and grip is fundamentally two different things. Friction only contributes to the overall concept of grip.

  • @user-kk5nl5go6k
    @user-kk5nl5go6k 6 месяцев назад

    As a physics student and track day rider and enduro rider, this is now my fave channel on youtube.
    Dirt knobbies next!

  • @andyjonathan2486
    @andyjonathan2486 Год назад

    Great video and excellent explanations. For SCCA autocross, I found that if went with too wide of a tire, it would generate less grip because for lightweight cars, the tire temperature would not increase enough during a 50-60 second run. The pressure at the contact patch decreased too much, in which hysteric deformation of the rubber into the tarmac asperities was reduced.
    Tire dynamics is indeed a very complicated topic. My head was spinning when I studied the brush model, dugoff model, and ‘magic’ tire formula back in school.

  • @jasonnaubur8759
    @jasonnaubur8759 3 года назад +2

    I think I need to watch this a few more times, well done. Also love the high quality audio, video and sets right beside the torn scraps of cardboard and hand scrawled notes, lol. Reuse that packaging!

  • @picassojeus6114
    @picassojeus6114 3 года назад

    Your erudition commends respect. Looking forward to more such explanations. Good job. Educating is serving. Your service is priceless. Keep it up man. 👌👍

  • @wizbangdiving
    @wizbangdiving 2 года назад

    1:36 in and I have renewed my subscription for 5 years. Very well done. Thanks 🙏

  • @MaDcOw1986
    @MaDcOw1986 3 года назад

    A very good explanation with real world scenario. Unlike other videos that only compares laboratory conditions

  • @johnnytopgun6414
    @johnnytopgun6414 3 года назад +1

    Awesome video. It's a community's job to keep tabs on the other's no harm done. Most of us all love canyon, ryan and yourself

  • @lukeskywodka8562
    @lukeskywodka8562 3 года назад

    Hey, i´m a tire Engineer for Car Tires and your video is the first on on youtube that i watched without feeling any pain!:) Great job!

  • @bernhtp
    @bernhtp 4 года назад +1

    This is the best explanation I've seen on how contact patch and tire size affect grip. It would have been great to provide effective coefficients of friction and how they change with tire size in a few select circumstances, but this data may not exist.

  • @shubhamupman7260
    @shubhamupman7260 2 года назад

    Dude. This is the best video I have seen regarding road grip!!
    Thanks!! ❣️

  • @lovelessissimo
    @lovelessissimo 4 года назад +3

    I love how the ultra technical concepts are explained on ultra technical torn-up cardboard.

  • @nlo114
    @nlo114 4 года назад +100

    I'm not sure how 'grip comes from weight', I weigh a lot, but I lost my grip years ago!

    • @jmc2567
      @jmc2567 3 года назад +1

      Cool comment,I don't weigh much and I,very got fk all grip too.cheer,s, happy and safe new year from,Auckland,New Zealand,all the best...

    • @derekbrown1064
      @derekbrown1064 3 года назад +2

      Underrated comment

    • @f308gtb1977
      @f308gtb1977 3 года назад +2

      🤣

    • @GeorgeTsiros
      @GeorgeTsiros 2 года назад +1

      bro you can find replacement grips on ebay n stuff
      you can even get heated grips

    • @juststatingfacts01
      @juststatingfacts01 2 года назад

      @@jmc2567 what???....🤔💭

  • @Birb_of_Judge
    @Birb_of_Judge 3 года назад +1

    This was very interesting and informative.
    And I ride a Honda Cb125r (not for much longer though) and that thing for some reason has a 150/60 rear, when most other 125cc bikes I know have 120 rear tires.
    But I have to say it has great handling and corners very well.

  • @brianmorse8811
    @brianmorse8811 4 года назад

    I got it the first time you talked about it. and I got myself a supermoto like you suggested. that 450 Husqvarna nice! great fun thanks... thumbs up!

  • @TanveerAhmed10
    @TanveerAhmed10 4 года назад

    man, we learned so much solid stuff from you. cheers!

  • @anuardelcastillo2627
    @anuardelcastillo2627 3 года назад

    Mike! Its great to have you talk real shit!!
    Now a days that its crowded with "experts" and "influencers" knowing nothing!
    THANKS SO MUCH

  • @youwantmyname9208
    @youwantmyname9208 4 года назад +2

    Man this is incredible and informative

  • @Bukester72
    @Bukester72 4 года назад

    Very, very good content! Thanks for putting this together. Awesome stuff!

  • @jakobbeentjes7511
    @jakobbeentjes7511 4 года назад +127

    When will you make a video about the knobs on dirt bike tires?? (13:10)

  • @blipco5
    @blipco5 4 года назад +1

    You are far and away the BEST motorcycle channel on the internet. Ride well.
    I subscribe also to Canyonchasers and Fort9. 🍻

  • @chrisgoes9610
    @chrisgoes9610 2 года назад

    I have a honours degree in Mech Eng and understand about 20-40% of this (albeit I qualified 30 years ago). That’s me being dumb rather than Mikes explanation. For the bits I did understand it seems to make sense and the graphics really help. My conclusion- it’s a complicated business and I’m really glad we can benefit from the research and testing those top brand manufacturers put in. I will give it a passing thought the next time I put on a wide track tyre. Mike you have done a great job here really useful content and well presented, many thanks for putting this together.

  • @OlmanEg
    @OlmanEg 3 года назад

    Wow! I was very sceptical of this video, because of all the trash on YT. You explain everything so clear for everyone!

  • @Pretko99
    @Pretko99 4 года назад

    Best motorcycle tire video I have seen so far

  • @MonoMoto
    @MonoMoto 3 года назад

    Seen your progress for a long time. This must be your best video yet and cool intro :D

  • @mowman7777
    @mowman7777 3 года назад

    Finally, an accurate explanation of tire grip.

  • @anandzope3236
    @anandzope3236 4 года назад

    You always have good informative content. Love from India

  • @MrJuggernautishere
    @MrJuggernautishere 3 года назад

    what an absolutely phenomenal video..finally somebody managed to distill and simplify Tony Foale as well

  • @jonathanharmon23
    @jonathanharmon23 2 года назад

    Just discovered your channel. Dude, your explanations are on point! Great content!

  • @astramorikes224
    @astramorikes224 3 года назад

    Truelly awesome video! I would love to have you as a teacher! :D
    Thank you for all your great work!

  • @DanielCastillo911
    @DanielCastillo911 3 года назад

    thanks, i liked your explanation, it is most needed in the bikes world. very hard to find explanations like this one

  • @johnsy59
    @johnsy59 4 года назад

    Nice work, you put into words many of my concerns/suspensions of many current grip and contact patch theories. It's not an either/or thing, it's a combination of a lot of black sciences interacting in a highly dynamic environment.

  • @biscuitsalive
    @biscuitsalive 3 года назад +1

    I’m remembering the friction experiment when you interlock two phone books.
    Page into page, for the whole book, the resulting friction was so high a champion weight lifter couldn’t separate the books.
    And that’s just the weight of paper.

  • @Haplo59
    @Haplo59 4 года назад

    This is great content.
    Thanks Mike !

  • @adrianm5147
    @adrianm5147 3 года назад +2

    LOL! I've been riding my whole life! You can tell there's something going on down there. Easiest way to explain it? It's like scotch tape. The bigger the piece, the more grip. You rock mike!

  • @lovepcgaming2335
    @lovepcgaming2335 3 года назад

    Got a sub from me for this vid. Explaining both the common theory and the actual material science behind it in laments terms is highly educational.

  • @jameslewis2810
    @jameslewis2810 3 года назад

    Loved this one, Mike!

  • @mauricioconzattifrison920
    @mauricioconzattifrison920 4 года назад +20

    When the engineering knows race and what are talking about. Great job for make me (engineering student) understand the real fisics behind those simplifications.

    • @victorperezADSK
      @victorperezADSK 3 года назад

      As an engineering student you should know the video is wrong. its first year physics

    • @victorperezADSK
      @victorperezADSK 3 года назад

      @Benjamin Vadocz see my other comment

    • @MikeonBikes
      @MikeonBikes  3 года назад +1

      @@victorperezADSK Some references for you to read up.
      The Racing & High performance tire, Paul Haney, 2003
      Motorcycle Handling and Chassis design, Tony Foale, 2002
      Motorcycle Dynamics, Vittore Cossalter, 2006
      Car suspension and Handling, Donald Bastow, 1993
      Chassis Engineerings, Herb Adams, 1993
      Competition car suspension, Allan Staniforth, 1988
      Drive to win, Carroll Smith, 1996
      Engineer to win, Carroll Smith, 1984
      Fundamentals of Vehicle dynamics ics, Thomas D. Gillespie, 1992
      Mechanics of pneumatic tires, Samuel K. Clark, 1978
      Prepare to win, Carroll Smith, 1975
      Race car aerodynamics, Joseph Katz, 1995
      Race car vehicle dynamics, William F. Milliken and Douglas L. Miliken, 1995
      Science and Technology of rubber, Frederick R. Eirich, 1978
      The physics of Tire traction, Donald F Hays and Alan L. Browne, 1974
      The Shock absorber handbook, John C. Dixon, 1999
      The Tire pavement interface, Marion G. Pottinger, 1986
      Tires, suspension & handling, John C. Dixon, 1996
      Tune to win, Carrol Smith, 1978
      Vulcanization of Elastomers, G. Allinger and I. J. Sjothun, 1964

    • @victorperezADSK
      @victorperezADSK 3 года назад

      @@MikeonBikes Thanks for the input 👌

    • @duane6343
      @duane6343 3 года назад +2

      No first year engineering student can make any statement on the validity of this video. The concepts here just begin to get into polymer science. Viscoelastic materials can be thought of as a dash pot and spring combination. I guarantee you that no undergrad ME has a scientific understanding of this topic (viscoelastic materials was a 500 level class in my Master's program). Please see the references Mike has listed.

  • @arjunp1835
    @arjunp1835 3 года назад

    The best channel to be a better Rider!

  • @b-radsadventures6846
    @b-radsadventures6846 3 года назад

    Always awesome, Mike. Thank you.

  • @shngsam8777
    @shngsam8777 3 года назад

    finally!! there is proper explanation on why wider tires giving more grip

  • @GurrasGarage
    @GurrasGarage 4 года назад

    Excellent, very informative!

  • @goodnewsnavid479
    @goodnewsnavid479 3 года назад

    that was a helpful video. thankyou for your simple explanation

  • @nbertolo
    @nbertolo 3 года назад

    Thank you for explaining this!

  • @ChadOHara98
    @ChadOHara98 4 года назад

    I gotta pick up that book! Sounds like a good read.

  • @HanahbibiVarietyVlogs
    @HanahbibiVarietyVlogs 3 года назад

    So, after I watched 5-6 videos of yours, I guess I can call you great teacher now.

  • @thunderbolt854
    @thunderbolt854 3 года назад

    Brilliantly explained .. nice i learnt something today

  • @kalle5218
    @kalle5218 4 года назад +24

    Fortnine heard boss music when this was posted :) Keep killing it Mike

    • @PK-lo6ws
      @PK-lo6ws 3 года назад

      who was the other youtuber who said it grip came from the weight??

    • @kalle5218
      @kalle5218 3 года назад

      @@PK-lo6ws i dont remember

  • @NoahN44
    @NoahN44 4 года назад

    Very informative. Thank u Mike

  • @hondaracer7784
    @hondaracer7784 4 года назад

    Now this is a good informative vid thank you

  • @patrickjoseph6237
    @patrickjoseph6237 3 года назад +1

    Best explanation ever and waaaaay faster than reading a book. Thank you for doing what you do. Wish I could recommend this video more highly than just a thumbs up.

  • @lucysmith4242
    @lucysmith4242 3 года назад

    This video was excellent. Thank you

  • @jozefsk7456
    @jozefsk7456 3 месяца назад

    just found your channel, finally someone without a finger up their nose

  • @heftyheft5185
    @heftyheft5185 4 года назад +2

    You should do a Collab with engineering explained for the ultimate motorbike aerodynamics lesson! Love all your vids

  • @Kergrist
    @Kergrist 3 года назад +1

    Excellent - and I taught motor vehicle. Superb graphics, 👍

  • @NikeAirOnesGaming
    @NikeAirOnesGaming 3 года назад

    Very good video. Very well put together, and very good and usual information

  • @alexf9472
    @alexf9472 4 года назад

    great presentation, thanks!!

  • @touringfolks4404
    @touringfolks4404 3 года назад

    I always watch your videos mike, so helpful. Imagine getting a heart from mike 😁👌
    from Philippines here👋

  • @laz1go286
    @laz1go286 3 года назад

    Great video!
    An interesting topic would be:
    What happens to dinamics and grip if you install mismatch tires front and rear on a bike (compound, wear,age, brand, surface design, etc)
    Coz many people change rear tires due to quicker wear on the rear whilst still keeping the front for a while.

  • @mr.screenshot9452
    @mr.screenshot9452 3 года назад

    Thanks for the info Mike 👌🏻

  • @kadir801
    @kadir801 3 года назад +1

    Awesome . Thanks for information.

  • @hwjucal9365
    @hwjucal9365 3 года назад

    Every type of material have different kind of coefficient of friction. I agree with Mike.

  • @krisnestorurian9127
    @krisnestorurian9127 3 года назад +7

    I don’t know if anyone has asked: “Why does Road tyres work better than street legal 21-18s on dual-purpose bikes?” I know the obvious answer is because it’s made that way, perhaps maybe you can explain further (and better than what I’ve read so far in Tyres and Vehicle dynamics).

    • @AntaresSQ01
      @AntaresSQ01 3 года назад

      Work better in what way? Grip? Turning? Longevity?

  • @heydario
    @heydario 4 года назад

    Great vid, very creative and interesting

  • @francisrevil854
    @francisrevil854 3 года назад

    very informative video for long distance riders too..

  • @carmarusso3869
    @carmarusso3869 3 года назад

    I gotta say this is a subject on my mind lately.
    I am an ex racer who rode before the tire tech came along! I have not ridden hard and fast on bias tires yet and am about to get back on bikes.
    Let's hear what you have to give as advice

  • @boynatzir9779
    @boynatzir9779 4 года назад

    Very informative and entertaining.

  • @jamest5149
    @jamest5149 2 года назад +1

    You have to throw stiction in to this as well, friction is seen in movement and stiction is the force to overcome to start a movement or slide, this is higher value than the measured friction value in movement. 👍

  • @andreavalota1926
    @andreavalota1926 3 года назад

    Wow! Really well done !

  • @jimhamilton2477
    @jimhamilton2477 3 года назад

    Excellent video!!

  • @maximilliancunningham6091
    @maximilliancunningham6091 9 месяцев назад

    You cover some points that others skip over. TY.

  • @Vroness
    @Vroness 2 года назад

    Nice presentation, I love it.