Are Wider Tyres a total WIN? The Aerodynamics. 

Besides getting a ‘fast’ tyre the most important call out to me from this is to match the tyre width (or range of suitable tyre widths) to the rim. e.g. 25mm Conti 5000 have the flattest transition on my current 5yr old aero carbon wheels but I’ve got a newer, wider wheel set and 28mm Conti 5000 appear to me to give the flattest transition. And yes you can feel it on the road. So it’s clear rim width is your primary determinant of tyre with.

everyday we are closer to the park hybrid dad bike, they've been the answer for ages.

"hey Margaret, that strange man is biking up and down the road again"

On my Polaris 69s, the 32mm GP5K isn’t much wider than the 28mm, but it is significantly taller. It’s effectively creating a deeper profile in the wheel+tire system.

Don't forget you can measure vibration attenuation with your other set of cheeks too! Thanks for showing that the P42 is good with 32mm tires as well - great for winter months and rougher roads.

These tests are great, and I sure hope you keep doing them, especially taking into account mere mortal average speeds into your testing. The cycling media and industry has somehow decided that an average speed of 40 km/h (or more) is somehow statistically significant as a reference, as if most cyclists, regardless of sex, age, fitness level or weight are fully comfortable with pushing 300W average powers on a daily basis.

In the 80s for time trials I used Wolber Profil 18 18mm rims with 19mm tubular tires. That was pretty common in the professional ranks. 165psi Now I use a 21 on the front and 23 in the back or a 23 in the front and 25 in the back. Also the standard setup in the 80s was Vittoria CX silk tubular in the front and a Vittoria CG cotton in the back.

I'm pretty sure that I'll never apply any of this to my cycling life/habits, but I sure do enjoy those videos and the amount of work that was put into them. Thank you a thousand times for that!

Drat! Going from a 76mm internal rim to 80mm internal isn't going to reduce aero drag on 27x4.5 inch studded tires. I'll just have to wait until the ice melts. Winter biking aside, these videos make me very tempted to get tires with a better compound for the spring/summer/fall.

3:31 casually flexing the beamer

I'm excited to see part 2 of this video on suspension losses. I've drunken the Jan Heine juice and run very wide 650B Rene Herse tires (48mm). I frequently wonder how much speed I'm losing due to aero and how much I gain from the increased suspension.

When I started using the Michelin Pro4's (well, at the time they were just Pro's) I was shocked at the substantially lower rolling resistance. When I tried the GP5K's, I didn't notice any improvement in RR, though perhaps in cornering speed, which is difficult to quantify. The Pro4's are cheaper and seem more puncture resistant. But the change from high pressure 23's to 28's made such a difference to ride comfort that I wouldn't have cared if they were slower. Since you're perhaps 15 lbs heavier than me, perhaps the wider tire is more comfortable for you. I have a recurring problem with speed being used for the quality of a ride, but then I am 78. But when I was riding 10,000 miles per year, I don't believe I was especially interested in speed on group rides unless everyone else was very fast. Then, I had a carbon fiber fork fall apart and drop me on my forehead, and my life changed completely. For two years, I was completely out of it. I was not even remembering to eat, and my previous 100kg fell to 60. I was finally taken by a cop friend to a competent neurologist who determined that I was having seizures that I couldn't remember afterward. It took about 6 months to determine the best medication and dosage, but suddenly, I became aware. I returned to riding with a vengeance on all of the latest bikes, but slowly, I became more uncomfortable with a bike made from strong fiber held together by weak resin. Finally, my cop friend who had saved my life had the entire head tube fall off of his C40, and he was lucky to only lose a finger because he was making a sharp slow uphill turn. But 5 minutes later, he would have been descending at 40 mph in heavy traffic. That was the final straw. I tried aluminum bikes and didn't care much for the noise. (The new ones like they Trek Alpha do not have that problem). Back to steel and 90s, welded frames are only marginally heavier than carbon fiber. My present Tommasini Fire that I put a steel fork on is 1/2 lb. heavier than my Trek Emonda. Somehow, I couldn't care less about the extra weight. I am shocked by the RR difference between the GP5K'S and the Vittoria Corsa.

I have been quite vocal on the approximations from the previous video, you have been quite more accurate on this one. Good job on the accurate pressure adjustment between width. A table with rim and tire measured width would put things in perspective and the real point missing is a 25mm tire there.

I went from Tufo S3 tubulars to 28mm GP5Ks + latex tubes on ~30x60mm aero wheels and probably saw about a 25W gain at ~30km/h. I was probably going 3-5km/h faster at the bottom of descents with no other changes. Tires, wheels and clothes are prob ground zero for low hanging fruit.... I would damn near say everything else is window dressing, especially for amateur watts. Thanks for the study

My chamois meter has long detected that the tire compound, carcass, etcetera was a bigger factor in overall wattage than rims.

I’m currently using Vittoria Corsa N.ext 28mm I have no complaints at all,they are certainly quick enough for mild winter riding. Once summer comes around I may shift back to Michelin Power Roads. Great video by the way

Great video, of course. But is that your E46 M3 at 3:31? Gorgeous car!..

Thanks for the excellent methodology and clear reporting.

I saw that E46 M3. Nice!

Good to know rolling resistance is first, then matching tire size/profile to rim external width gives the best aero.

Super cool look at detailed 'stuff'. One thought - a treaded tyre like the Vittoria Corsa has virtually zero chance of achieving laminar (attached) airflow over the curve (leading edge) of the tyre. The treads act as turbulators that trip the air flow up causing it to tumble. The more prominent the tread the greater the boundary layer of turbulent air between the tyre and the smooth flowing surrounding airmass - this effectively increases the profile drag of the entire wheel. For best aero ride slicks and match the tyre width to the rim such that there is as little indentation or difference in width as possible (smooth transition). In fact tyre designers should be exploring this to make tyre/wheel combos that have zero interference to airflow - completely flush join at bead.

Vittoria Corsa cotton fanboy here. Yes, I have run older Continental GPs and Michelin Powers a few years ago, when going to Corsas I felt like I am on really fast and comfortable rail tracks. On pair prior to my last Corsa Controls I made 10Kkm rear/14Kkm front, changing them after 1st flat on the rear, while even the rear one had at least half of the profile left. And the wear is not square as on nylon tyres. From autumn I am on Controls and they have been a blast. I can even descend with them on partially snow covered roads with confidence, that's how good the grip is, no wonder that most of peloton used these in tubular version just a season or two back. I can't feel difference to standard Corsa profile in speed, while I can feel minimal penalty on flat speeds on Corsas vs older GPs, but there is no way a 19W difference in ride feel. That is more than difference if I put on alu shallow wheels vs aero carbon - which I can surely feel then. And my times on Strava are in favour of Corsa cottons, so I really must trust them more than slippery GP/Power even on climbs. And it is a much more comfortable ride even at higher pressure than on GP to match the comfort. If I was racing crits then I would think of faster tyres, but for my style of riding Corsa cotton are FTW and I am maybe even staying on Controls in summer as these are probably one of best real 4 season tyres. Saying all that I would like to try newest Michelin Power Cups, does anybody have a real world comparison between Power Cup/Corsa cotton?

Hey PT, cannot remember for the life of me your opinion about the 105% rule. 28mm wide rims usually have that larger part measuring 30 so in accordance with 105% rule with 28 tires

Always look forward to peak torque content. Thanks buddy!!!!

After rewatching, the ratio between outer rim width and stated tyre width versus the aero performance makes sense: the 28mm wide Ican aero 35 wheels were faster with the 28mm tyres, and the 33.5mm wide Ascent Polaris 42 wheels were (slightly) faster with the 32mm tyres. The smaller benefit with the 42s and 32mm tyres may be because the rim is actually wider than the tyre in that case? This suggests a 1:1 ratio of rim width to stated tyre width is the best in terms of aero, what makes sense really

Very interesting data as usual. Would love to see a similar test with 25-28-30-32 mm tyres on the same rim, preferably a bit deeper (like 60 mm). Quantifying the gains and proving/debunking the 105% rule. Huge props for doing these, I've tried doing some experiments myself, had some success when gravity or RR caused most of the losses, but I also found that there simply isn't enough resolution, or the circumstances change too much to analyse aero losses/gains - without the pitot tube, of course :D

Nice to have the data back up the intuitive result. You'd expect the wider tire to be less detrimental on a deeper wheel, to the point that a solid disc wheel would be fine with tires that would really screw up a shallow rim of the same width. Those Polaris rims are a bit of a joke in width really, you'd have to get a mountain bike tire to be in the "too wide" range 😄

Great video. Well explained. I'm looking forward to the next video.

good suff, I am riding Zipp 303 firecrest with GP5000str. Had multiple punctures recently and was considering the Corsa NEXT as an alternative. Now will think twice...

would have loved to see a 25mm compared to a 28

We need the measured width of the tires on the rims (at the PSIs you mentioned). That would be immensely helpful. I don't assume tires are their labeled width after being mounted on a rim.

that transition is not at least a design issue, the eye got to like the ride as well, but on top of all that, one should remember to consider much more important issues for layman riders with the tire choice, as - grip, - durability, - how they actually drop off in corners or when braking, how they perform in their second half of their life span, - comfort/traction vs. weight/agility concerning width. Differences in the mentioned are staggering - and decisive for the pleasure and safety of the sport. I opted twice for top ranking products in a bike magazine's comparative test. Both had to get off the bike after one or two rides. They just were dangerous fun preventers and in one case have even shown very quick wear. So some self education and research pays off, as well as incrementally testing forward from a once well-proven selection.

That intro is stronger than pre-mutation Covid-19 LOL

Thanks for all the great videos you make. You're top 3 on YT for sure. I follow you all the time. Thanks for all you do. The best wheelsets you can ever buy are Flo, made in America. I sure would like to see you do a video comparing these to any wheels you might choose. I would say these are better than anything else you can find.

Am I thn correct in understanding that the smooth transition is still the most important aspect - so right size tyre for the rim rather than wider or narrower per se?

would've loved to have seen some winspace wheels with 25mm tyres (given they're sold as being designed to fit 25mm tyres best. my set is flush af with 25mm gp5k's). RR vs cda for 25 vs 28 would be super nice to see. my hypothesis is still that 25mm front and 28mm rear is fastest (as seen on some WT team setups), but you're the only person who could test this, lol ((btw ERTRO standard rim for measuring width is the same for 25 and 28mm tyres, 19mm inner since Jan 2020. ultra wide wheels are a meme, same as road tubeless))

Does your data suggest that narrow rims, with narrower tires, require less power to maintain a specific speed?

Tyres with the same construction but in different widths will have lower rolling resistance with increasing width. That is at least true in any reasonable range - like 1 to 10 cm. Also you cannot get the same comfort (equals performance) on a 20 mm tyre as on a 42 mm tyre. Jan Heine did a FKT this year on 54 mm tyres. He was concerned about the width but in hindsight he doesn't think it was holding him back. So the optimal tyre width is probably larger than what you think.

Something else - bigger tire at lower pressure becomes less flat prone. Or, put another way, it takes a sharper object to puncture said tire at the lower pressure. Can only guess at what percent lower rate of flatting...... Although, folks in their black soot belching turbo-deisel 4x4 pickup trucks are still gonna' throw thumbtacks in the bike lanes 😔

Would like to know how just changing the rear wheel width affects the result. Guessing there’s less aero watts lost with a wider tire in the back

massive value! thank you!

Well Continental claims that much of the aero efficiency of their GP5000 is due to the side thread in the tyre, so that might explain why two tyres of the same diameter perform differently, and still via an aerodynamic rather than rolling effect

if that E46 is your car you have great car taste as well!

All size tires are win Your body weight has vital effect on that win The more you weigh the more drag the more slower you are

Reason why I love wiser tyres is a lot of roads where I live are absolute shit. Torn up, I encounter gravel roads when I don’t want to. So a good tyre that I can run tubeless at a low psi is good for my everyday riding.

Thanks for all your hard work!

Although these tests with a living thing in the saddle (you) are unscientific, and uncomparable, I really like your effort and dedication. You are on the right level, but to find the right door either your tests' limitations should be better explained, or go to a more showlike approach, where everyone suspects them and the product is still entertaining.

You publish quality content when you are not discussing wheel building. Chapeau.

Great timing. I run 32mm GP5000S TR and just upgraded from 23mm external width standard rims to Roval Rapide CL II (35mm max width) aero rims. Using the "Chung method" I found a 12% lower CdA. I know a lot of that is due to eliminating the "light bulb" effect. Also, since the Rapides are optimized for 28mm I was wondering how much aero I was giving up running 32mm tires. Roval support said the differences would be quite minor and your work backs that up.

Top video, love the detail. Would like a pair in the tan side wall but losses on BRR puts me off big time. Don’t suppose you or anyone else has tested against black. Thanks 🙏🏻

great test! I have a road bike with the "default" 28mm tyres it came with, and the inner rim is 17mm wide. Should I stay with the 28mm or go with a 32mm tyre (the max that my bike allows)?

Fantastic data, subbing on Patreon I want to see more.

Most 23mm tyres came down in price. On 19mm wheels tyres expand to 25mm. With lowish pressure (front) they match and roll just fine. (more aero and lighter)

Brilliant work, thank you.

I think it might be a mental thing, but I really don't like riding anything wider than 25mm, despite how many times I hear how wider being faster.

Excellent channel and a great video. Do you run special tubes in your GP5000 tires? Can you confirm that the system weight for the 76psi ideal on the 28mm tires is just over 100kg? My system weight is 95kg.

can you try 25mm gp5000 on the 21 internal rims? thats what im running now they measure 28mm external width

Someone needs to pave a shitty road inside a huge building so we can do these aero tests without worrying about wind

Excellent information.

Thank you!

Have you ever tested the effect of filling in the gap between sidewall and rim with a rtv silicone/caulk? I've heard rumors of pros doing it, I don't think it'd be practical for flat repair, but it would make a nearly perfect transition and I'm curious what it would save. Great video.

Superb. Good work.

Interesting how all the tire trends are going back to the old standard of 27 x 1 1/4 (32mm !)

Would be interesting to know how 25mm GP5ks would have done on the ICAN 28mm wide wheels. Since 28mm GP5k on 21mm internal is about 30mm so wider than the rim.

I've got a 28mm tyre on a narrow back rim (internal 19,6), with an ez disc cover, it does bulb - but is it as important for the back wheel as it is for the front wheel? The wheeks are giants hookless slr1 42's so tyre options are limited for an 80kg rider trying to stick under the crappy 73psi etrto limit. so its either ride cadex or suck up a 28mm bulbing gp5000 s tr

Super video. So for those on rim brake with 17C/19C rims, does it means, that for more "aeroness" we maybe should stick on 25mm tyre?

I'd love to see a deep/ shallow comparison!

So the difference of (narrow rim & narrow tyr)-(wide rim & narrow tyre)=6 W (aero). What if you take into account rolling resistance and friction? High chance the gain would be bigger than those 6W

Tire sizing is all over the place which is a bit annoying, I gotta say. I got Vittoria Corsas labelled 25c. On a rim with around 22mm internal width they measure a true 29mm. So they're just fractionally narrower than my rims at around 29.5 external. It's a fast combination. Schwalbe and Conti tires have been significantly downsized. The 25c Corsa is wider than a 28c Schwalbe One on the same rim. You really got to do your research when buying tires these days.

My thought, technically, rim width will determine your tires size. Overall weight will tell you the tires pressure. Other than that is just feeling, subjective. Today you are good, next day you are not, yesterday wet road, today dry road, an hour before you are fresh, after that you are not, this parameter are subjective. Wider tires are flabby, lost power, however you get comfort to accommodate power lost and help you focus for overall performance.

How much less important is it for the rear wheel I wonder.

Your sunglasses look like the ones FAUSTO COPPI used to wear! 😊

Did you measure the actual width of each tyre vs the labelled width? I ask because in the last 18 months I've had 3 sets of 28mm Conti 5000's First set came stock with Canyon Endurace on the stock DT swiss rims (I believe 21mm Internal Width). In order of purchase the 28mm Conti 5000's measured (calipers) at: 30.5mm/31mm 29mm/28.3mm 27.8mm/27.3mm At my weight this results in a 14psi difference between the first and last tire.

Good test and video! My experience going to wider internal rims (28mm measured clincher to 30.6mm measured tubeless tire on ~55mm deep wheels) also felt like not much, if any aero penalty with tires narrower than rims. I am somewhat surprised b/c some (like Hambini) suggest that once you go to wide tires, the required chord ratio for aero benefits is well beyond 80mm deep wheels. (Which I may have misunderstood to mean that wider tires require deeper wheels to maintain same CdA). Or is the better understanding that the max width of tire/rim system is determinative, and so long as you keep the tires < rim, you can maintain CdA (or perhaps slightly improve since the overall system is deeper)?

Great work once again 👍

Is the overall recommendation to get to as close to 1:1 measured tire width and external rim width to maximize options for rolling resistance and comfort while maintaining the aerodynamic relationship between the tire and rim?

Would it be safe to assume that that these results would hold if the size of the lightbulb effect was constant? So if the 32mm tire and 28mm iCan rim has a 4mm lightbulb effect, would a 28mm tire and 24mm rim have the same aero losses? I assume there’s a few other things you’d have to assume as constant, but like… the same-ish aero effect?

perhaps I have missed it, have you tried to do an aero test of skinsuits and jersey/shorts? i.e. same as GCN tried recently

I enjoy your hair splitting style.

All this is cool and great, but I have an important question with winter coming: Where did you buy this cute orange gilet? I’m a convert, riding 28mm GP tires on 32mm WR40 LightBicycle rims. No 30 or 32mm tires due to the marginal weight penalty. In tubeless with 4 bar/58 psi. I haven’t noticed any performance drop in my usual pelotons and will never go back to thinner wheels, mainly for the sake of long-ride comfort.

I suggest a “guide” for aero optimizing tire and rim width combos.

Bloody brilliant 👍👍

l run 100 psi in my 25s on 38mm deep wheel ,now with faster tires WOW difference , and 80psi on my 32s with 28mm deep rim not as fast but way more comfortable overall and less buffing from the winds, that s why its everyday bike the other for fast days in the saddle :) GRANTED two very different bikes but l know the tires sizes and psi play an important part of feel overall too when just rolling around town

Nice E46 M3. :)

Trek und Spec are beyond a doubt best chois quality/cost ratio.

how wide was the gp5000 32mm tire on the p42, and the gp5000 28mm tire on the Ican rim?

nice troll with the community post lmao

I wonder how Polaris 42 and zipp 303 firecrest compare. Only 2mm difference in depth. 303 is 2mm internally wider. Same price point too. They’re roughly the same weight too.

Thank you so much for your testing efforts!! Do you think the effect comes manly from the front wheel?

Argh, I'm even more confused now. I have 19mm internal width rims (Giant SLR1) designed for 25mm tyres. I wanted to try 28mm for the comfort benefits, rolling resistance should be about the same. Hookless aside, I'm 70kilos and had no issue running 25mms for 10000km now at 80 psi. I want to go 28mm so I can drop the pressure a bit but seems like aerodynamics wise, I will be penalised ... What would you buy if you were me? :D

Cant afford new wheels with the wider internal width so, with my good old 25mm external diameter rims, Im going back to 23mm front tyre for aero and 28mm rear tyre for comfort and puncture resistance.

In terms of rolling resistance have you looked at Veloflex vs the GP 5000? I am debating which ones to get

Howabout getting hold of a few different tyres to test if other brands can match the gp5000 tubeless

Amazing video PT. Been waiting for this one to come out! I’m looking to buy a new wheelset for racing and considering the hyper 65s. I feel like 28mm (GP) tyres on those wheels will offer better grip, lower rolling resistance, and aerodynamics than current 25mm on 404NSW (19mm internal, 58mm depth). Thoughts? And with the downsized sized from continental, should I be running 30mm on those wheels? Thanks a million and loving the content brother!

I have light bicycle ar375 which are 25mm and bulge out to 30mm and currently run 25mm gp500Str (27mm measured), would there really be a penalty if I swapped to a 28mm F and 30mm R?

so a 23mm tire with a proper wheel set in a frame that is designed for that wheels is still the fastest setup?

You might be getting a call from eastenders with acting like that in the intro 😂

what is going on with your seat tube? looks like there's no seatpost and only seat tube 6:40. Is your seatpost just the same colour as the frame and it's hard to see?

question non-topic related, what is the front light you're using? super cheeky and elegant mounting system right below the stem, I'd love to know what brand/model it is?

What’s the best tyres besides a Conti 5k? Pirellis?