Any benefit using 20mm width tire
- Thread starter novetan
- Start date
The only and very slight benefit of using 20mm tires on conventional 19mm clincher rims is slighly improved aerodynamics in low wind or direct headwind situations. In every other way you're better off with wider tires. Wider tires in 23c or better yet 25c sizes will improve:
- Rolling resistance (the wider tires will roll faster for the same air pressure)
- Cornering (larger contact patch is more stable in corners)
- Comfort if you run the wider tires at a bit lower pressure which you should
- Handling on poor roads or rough pavement
There's basically almost all upside and very little downside to running wider tires. Many pro racers are racing on 25c tires these days.
I would not run 20c tires for general riding around but go with at least 23c and ideally 25c tires for most of your riding. At your weight you won't want to run a ton of pressure in those wider tires but you'll get a nice smooth and fast ride and should get improved confidence while cornering fast, especially in wet conditions.
-Dave
- Rolling resistance (the wider tires will roll faster for the same air pressure)
- Cornering (larger contact patch is more stable in corners)
- Comfort if you run the wider tires at a bit lower pressure which you should
- Handling on poor roads or rough pavement
There's basically almost all upside and very little downside to running wider tires. Many pro racers are racing on 25c tires these days.
I would not run 20c tires for general riding around but go with at least 23c and ideally 25c tires for most of your riding. At your weight you won't want to run a ton of pressure in those wider tires but you'll get a nice smooth and fast ride and should get improved confidence while cornering fast, especially in wet conditions.
-Dave
Well not nearly as many narrow tires are sold these days, especially with the advent of the new wider rims. But a lot of it is historical, when I started racing 19mm and 20mm tires were standard for racing. But that was long before on the bike power meters and a lot of folks doing careful rolling resistance testing and they were believed to be very fast tires. I took a break from racing for about a decade and when I came back to the sport around 2006 suddenly everyone was racing on 23c tires which back in the day were considered fat tires for poor course conditions. But a lot of testing had demonstrated that they roll very well and folks tend to find they race very well and feel good even when the pavement isn't great. In recent years the trend has continued and suddenly 25c tires are the new norm for a lot of races. Not everyone, but a lot of folks have switched to wider tires and they roll plenty fast and feel great on a wide variety of road surfaces. It's possible we'll start to see fewer tires offered in the narrower sizes.
Hopefully not all the narrow tires will disappear from the market. For instance in pure timed events with traditional narrow rims a 19c or 20c tire is still one of the fastest choices. They're getting harder to find but I keep a stock of Bontrager 19mm Aerowing tires for my front tire on a 19mm HED Trispoke time trial wheel and run 20c Continental Supersonics on my 19mm wide disc wheel in the back. There are still a few choices for fast time trial tires to match narrower rims but not nearly as many as there once were, I sure hope they don't all go away.
I guess one other 'benefit' of narrow tires is that they're proportionally lighter than 23c or 25c tires. A lot of cyclists buy just about everything with an eye on weight and perhaps that's one reason racers stayed with narrow tires for so long but realistically the handful of grams difference between the same high end tire in a 20c vs a 23c or even a 25c has almost no bearing on actual performance, especially compared to the rolling resistance advantage you get with wider tires of the same build. Except of course for the aero consideration when those tires are mounted on traditional 19mm rims as mentioned above but again that mostly matters in pure timed events.
So some of it is tradition, some is that rims are evolving to be a bit wider and a wider tire mounts nicely on those wider rims and some of it is that not everyone pays attention to things like rolling resistance, contact patch shape or the advantages of running a bit less pressure but an awful lot of folks still count every gram.
So I guess as long as enough folks still buy the 20c tires for time trialing or just personal preference reasons they'll stay on the market at least I hope so for TT purposes alone.
-Dave
I would definitely recommend at least a 23c tire for general riding including fast group riding and mass start racing even if the leap to 25c is hard to accept but think about giving it a try. After all we run through tires pretty fast so at worst you go a few months on tires you don't love and then switch back on your next set. Regardless of which way you go I'd highly recommend Continental GP4000s tires in either the 23c or 25c sizes. There are faster tires and there are sturdier tires but it's hard to beat the GP4000s for a tire that's both reasonably sturdy and still quite fast, the black chili tread compound they use also sticks like glue in corners either wet or dry which is a nice plus.
I race road races and crits on either the Vittoria Corsa CXs or the GP4000s tires but of the two the GP4000s is clearly longer lasting. I ran Michelins for many years and really liked their Pro Race 2 and Pro Race 3 tires but haven't liked the ride of the Pro Race 4 nearly as much and have gone back to Vittoria and Continental. But there are a lot of other good tires out there as well and lot's of opinions if you search around on the web.
-Dave
I race road races and crits on either the Vittoria Corsa CXs or the GP4000s tires but of the two the GP4000s is clearly longer lasting. I ran Michelins for many years and really liked their Pro Race 2 and Pro Race 3 tires but haven't liked the ride of the Pro Race 4 nearly as much and have gone back to Vittoria and Continental. But there are a lot of other good tires out there as well and lot's of opinions if you search around on the web.
-Dave
Dave,
Presently I'm using 23c for both front and rear. What do you think if I just change the rear to 25c. Which could also means higher pressure for the front (23c) and maybe slightly lower pressure for the rear (25c). As you are aware i'm light weight and I mostly ride on good surfaced road, would you able to confidently say i shld able to pick up speed even using both front and rear 25c.
Tks.
I would confidently say you could pick up comfort and high speed cornering confidence without losing speed but that's not quite the same thing as saying you'll pick up speed.
But sure the 23 up front (where aero matters a bit more) and the 25 in the back is a very reasonable setup. As you've mentioned you're pretty light make sure you're not going overboard on tire pressure. That's a very common mistake as folks believe rock hard tires and feeling all the road vibration and buzz at speed means they're going faster. In general if your tires are pumped up so hard you feel all the road buzz you're actually going slower for the same effort. I've posted this before, but it's a good discussion of why we shouldn't go crazy on tire presure: http://www.slowtwitch.com/Tech/What_s_in_a_tube__1034.html
My main point in answering your questions on this thread is that 20mm tires are NOT in general faster with the exception of the aero question on narrower rims. So I definitely would not move to 20c tires in search of speed. I'm still running 23c tires on my road bike race wheelsets but train on 25c tires that are plenty fast. I'm not convinced the 25c would make me noticeably faster but I am convinced they'd improve comfort and cornering without a speed penalty. So don't get me wrong I'm not trying to oversell the virtue of 25c tires or say there's magic there as I haven't fully made that switch myself. Just that going narrower is the wrong direction and you may prefer the 25c tires overall if you give them a try.
-Dave
If you're using a modern deep rims wheel there's enough test results for most brands as to what tire width works best and what doesn't. Even on a silly wide rim like the new Bontrager Aeoleus, the wheel will "stall" much earlier with a 25mm tire. If you want to go fast of that 26mm wide rim you stuff on their 22mm wide tire. When spending $1000+ per wheel in order to gain performance, chucking on a set of tires "because it feels better" or because you "feel it goes around corners better" is a bit like wearing a tin foil hat under your helmet so your rivals find it harder to anticipate your moves. If you need comfort and the roads ain't to bad drop a few psi - if you're riding cobbles or unpaved roads then preserving your taint becomes key and your priorities might change somewhat. The difference in contact patch between a 20mm gp4000 and a 23mm with a few psi less Gp4000S is very small and I can't tell any difference between them when leaning the bike over hard. The black 20mm gp4000 has the same rubber tread compound as the 4000s - the pretty colored ones don't. Even back in the day riding TT's with my Campag Shamals with Conti LA tubulars (19mm i believe) jackhammering my butt at 170psi on concrete roads and the expansion slots, I never really wanted for more grip in the bend and leaning the bike over at 27+mph when ready to barf near the finish is the last place "sketchy" handling is required. 170psi was concrete duty only and even then it was a little tiresome - but the whistle or the tire was like a bike **** soundtrack. The Shamals were hardly what you'd call comfortable or forgiving in nature either and complemented the 170psi "nicely". On rough roads that pressure would be stupid - I'd run 115psi read and 105psi front, more than enough for ~145lb. What I notice on the bike, but lack data for, feels similar to what I noticed when racing cars, with limited data - ambient temp, tire temp, pressure, rollover, is that for a given tire of a similar size there's not much difference in performance in the twisties - tire pressure is where it's at. On my car, running a 205 or 225 on a 7.5" wide wheel was about the same per ~ 1 minute run with the only difference being that the wider tire would be slightly easier to control at the limit. Run the same 225 tire on a 9" rim and its be night and day. Given that on flat to rolling roads aero trumps rolling resistance every day of the week, I'd go with a tire that more closely matches the width of the rim. Bicycle tires don't have a structural sidewall like say a cantilevered racing tire does on a car (or even a high performance street car tire with reenforced sidewalls) so running a wider tire doesn't really give as much of a benefit as I would have expected. Sadly, I never owned a set of said racing tires but did get to drive an old lotus elan with some on... Drool worthy.
Good post, Swampy. I wonder what the contact patch of my old 19-20 MM sew-ups are in comparison to a modern 25 MM clincher in square inches...not much difference I would guess. Especially with both tires at 110 PSI on the local camel paths they call roads. More a function of pressure and loading.
At the same pressure, sure, but since the wider tires have a larger volume, they can run at lower pressures and significantly increase the contact patch size, meaning higher cornering speeds and better traction. There's no question about it.swampy1970 said:
Because some manufactures still manufacture 19mm rims.
Wider tires roll faster. Narrow tires cut through the air quicker .
However as rims get wider, the "lightbulb" (aero-killing) effect caused by wider tires is reduced.
In the Velo News (independant) wind tunnel results for their recent aero bike test, the Scott Foil with the widest frame tubes was one of the faster, and more aerodynamically sound bikes in the test. Wait Wut!? A bike with wider tubes was more aerodynamically sound than one with narrower tubes? Shape matters. The tire forms the leading and trailing edges of the rim, it does not define the aerodynamic behavior of the wheel as a whole. For aero performance one would want that ratio of tire width to rim width to be as close as possible. 25mm tires are still very aero on the Zipp 303's with an aero width (measured at the widest point of the rim) in the 27-28mm ballpark.
Narrow clincher tires roll slower (fact) and handle like **** (my opinion). Folks who may not agree with the latter are very likely basing their response on their memory of tubbies. Tubulars by nature roll and "feel" better than clinchers, although clinchers are quickly catching up and I believe a widely referenced internet resource actually has a clincher trumping all others in a very large pool of Crr tests (the Specialized Mondo). 20mm and 22mm tubbies actually still feel pretty good. But I garantee you, one single ride on 19mm clinchers will have one change their tune in a heartbeat. Narrow clinchers are the quickest way to demote ones riding experience with close to zero real world benefit.
Narrower is indeed lighter and there are quite a few threads on this forum adressing those (so-called) benefits. But it cracks me up to no end when someone is talking about 20 grams on a tire making any real world difference. If anything it just increases the chance at a puncture which is definitely not good for a podium result. Just ask Tony Martin.
The times they are a changin.
Edit: and as per usual without reading all posts before mine I have repeated (reinforced) what others have already said /img/vbsmilies/smilies/wink.gif
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