How much do tires affect speed?

lol what happened to alienator? the use of "was" gives me the feeling this forum is going to become quite boring...., oh and I know its kind of late but how did you do in yaletown? (sorry if you were in svein tuft's category he had no business being there, well I think at least)

 

Tires are very important, period!

 

I know, I never ride without them!

 

Truth so pure.....

/img/vbsmilies/smilies/ROTF.gif

 

Something that has not been addressed is weight to pressure ratio. Lighter ridders can run a softer tire and not get snake bit (pinch flats) as a heaver ridder would at that same lower pressure. In other words if you are 200 or more you may want to think about upping the pressure some to avoid a pinch flat and possibly a damaged rim too.

 

Cool, thanks for that 12yr old outdated test.

 

hmm, but wouldn't you want to always ride at the max air pressure to get the fasted ride?

 

not necessarily, if they are inflated too much instead of absorbing bumps you will harshly bang over them, losing contact with the ground and essentially be less efficient. It's also a less comfortable ride.

 

+1 And your tires may be more likely to get puncture flats when they are inflated to the maximum air pressure..

 

but I thought when tires are at high pressure it's better because debris deflects off it, whereas with soft tires it allows debris to puncture into it with less resistance. I dunno, high pressure tires always works for me.

 

How do tires affect speed?

We would ask the winners of this past season,

Except that the men of 1898 are so fast, they've not returned.



((am missing my Bontrager Hank Slicks and my Trek Lime...both rolled off last week, stolen))

 

I think the balance between durability and speed is the is an interesting piece of the pie. I'm running Specialized Armadillos now - not the fastest tires out there. But after spending one season on ultralight folding bead tires before transitioning to the Armadillos I'd have to say that the 1 - 1.5 mph I lost in average speed was WELL worth the lack of flats.

I think folding bead tires are really easy to mount because they have to be. Seriously, I never rode on trails or gravel or anything besides roads and I still had to dismount those tires at least once a week. The last 2 years riding Armadillos I have not had a single flat. I imagine the Gatorskins offer the same peace of mind and convenience. I wouldn't race with them, but for the riding I do I'm very happy to have tires that are both road specific and durable. They are a bit pricier than the others but will save you that money and more on the cost of tubes in the long run!

 

All this stuff about tires is very interesting, because it was all well-understood by...about 1896.

Google book search, free read online, "Palmer Tire" and choose 19th century view.

Read about how perfect various bike tires were by...1898? Tubulars were -easy- to patch on the road, if merely punctured.

True then and now: the thinner the tread and the more supple the casing and the higher the pressure and the narrower the tire,
the easier the roll at high speed, but...thin, high-pressure tires give up much of the cushion effect.


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I love, will always love, the easy roll (excellent for 15mph biking on asphalt, for instance)
and the soft, lovely ride of a Bontrager Hank,
huge volume, slick tread, rolls by itself, nearly, very efficient for cruising bike speeds,
and laughs at ruts and bumps and sandy patches of asphalt are no slip-risk to a Hank and yourself.

Hank is perfectly slick, and so no tread noise at all, dual compound, (sticky on the sides)
and we don't need tread, as we all know, for a street tire, not even on wet roads.

There are very few balloon tires with true slick treads.
Hank is not puncture resistant or thorn resistant,
no more than a thin glove, but it is comfort defined, the best possible, nearly, for a fat, cushy tire,

Hank will take jumps and bumps without damage.
It is tough against impact, any impact on the street.
It comes in your choice of black wall, or black with a red stripe on the sidewall.

The Schwalbe "Kojak" is another candidate for any MTN biker
who wants to get a taste of what road bike slicks are like,
but wants to keep to relatively large volume tires for comfort too.

((I have not price-searched for best price))
http://www.amazon.com/Schwalbe-Kojak-Mountain-Bicycle-Tire/dp/B003ZJBQT2

Bontrager Hank is only available through your local Trek dealer or direct from Trek online.
http://bontrager.com/model/02856
(good picture above)
It's a beautiful tire, but it is also so relatively fat, that it may not fit in some skimpy front forks.
It is a handsome devil, though.
http://tinyurl.com/6chxlbu

(((so much for fat tires that roll sweet on cruiser and mountain bikes))

Schwalbe Kojak images for comparison,
http://tinyurl.com/6hk9ct4
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The narrow and hard-pumped tire is fastest and easiest to power.

The hard-tread, thick tire, not too highly-inflated, tends to be more resistant to punctures.

The wide or soft tire is softest to ride on and offers traction and footing unrivaled by others.

Tread is not needed or wanted for asphalt roads.

 

Higher tire pressures do not calculate to less rolling resistance.

Most folks (and I used to be one of them) erroneously think that a rock hard tire makes less overall contact with the ground (that is true) which means less rolling resistance, which under most circumstances is false. Only on a perfectly smooth track does this hold true.

Rolling resistance is a direct function of a tires ability to deform along with road irregularities. A tire's pressure range is based on a riders weight and should be inflated accordingly.

Aside from a lower rolling resistance, lower pressure tire punctures are way less catastrophic, and ride quality is greatly improved.

Tire responsiveness, which has nothing to do with rolling resitance, is improved with higher pressures. The goal should be to find a pleasant compromise among all those factors that are important to you.

Maxing out on tire pressure will exponentialy increase the number of surface cuts and chance of puncture. Do an experiment with a balloon, blow it up so it's super fill. Drag a scissor edge over it... BOOOM! Same balloon at a moderate fill may have you dragging the same scissor edge over repeatedly with no explosion.

 

There is all this concern about the smoothness of the road relative to the tires.

So what is smooth enough for high pressure and narrow profile tires?

Most of the roads around here are newish concrete or asphalt. Certainly not indoor track smooth but hardly enough bumps to require pressures below 120psi. (I ride at 110psi becasue my air compressor will only go that high.)

 

Yes they do, but not in ALL circumstances. Your statement lacks proper qualification.
Higher pressure (to a point) on a relatively smooth surface is faster than a comparable lower pressure. Don't know about you, but most races around here are conducted on very smooth, paved surfaces. ymmv....
Did you take a look at the tire test report I posted awhile back on this thread? See the section "Pressures Other than 120 psig".

Yeah, on bumpy, chip-seal roads I agree to not run relatively higher pressures.

edit: Keep in mind the tires used in the tire test were exclusively high performance. With non-performance tires, the performance benefit from higher versus lower pressures would've been even more pronounced.

 

Most races I ride in are conducted on either New York State highway roads or local parks in NYC.... not very smooth.

I use the track example for a smooth surface with no irregularities. No irregularities, no need to deform, better rolling resistance at higher pressures.

The well known Bike Tech Review study runs 99% of the tests at 120 psi - gathering from responses here and on other forums, that would be on the low end of what many think about as normal. Folks start talking about running 140, 170, and beyond thinking they are going to roll faster - not sure how skittering all over the road equates to faster. Confusion may result from the assumption that I am suggesting less rolling resitance is available at less than manufactures recommended PSI's I do not recommend running your CX's at 85psi, unless of course you are riding to Roubaix /img/vbsmilies/smilies/wink.gif

The TUFOs and other variable PSI's are tested on 100% smooth rollers.

From the studies legend: Crr values are typical for very smooth surfaces - Crr on typical road surfaces may be 50 to 100 % higher

This comparison was done on a smooth drum. The exception I offer regarding the smooth track Crr's being different are fully supported by the study. We have no clue how these numbers would pan out when having to stay glued to anything other than glass. There is nothing I put forth that contradicts the study. There is nothing put forth in the study that contradicts what I am saying.

If it makes us all happy I will caveat and add:
Higher tire pressures do not "neccesarily" calculate to less rolling resistance.

 

The study may be "well known", but that still doesn't stop people from claiming higher pressures are slower than lower pressures...Hopefully, with continued promulgation it will at least allow even more individuals to make a more informed decision about how much pressure to run...

 

"Well known" was an inappropriate label... it's well known among me and my nerdy bike chums but a great source of data nonetheless. I'm also erroneously assigning lower rolling rolling resistance to equate to a faster roll. Theoretically a bike with solid steel tires would have less rolling resistance than rubber tires and so I will caveat even further and add that higher tire pressures do not necessarily calculate to covering ground at a faster speed, your bumpy chip seal road as a good example.

 

Hypotheticals aside - as I race on smooth roads, I run 130-140psi at my 195lbs. Feels comfortable and fast enough. Would I run higher? Nope, don't find it necessary. If I was TT'g, I might. If I raced on poorly surfaced roads, I'd probably run around 100psi.

FWIW. I run 700x20mm clinchers and 700x21 tubulars when I race. Obviously, I haven't bought into the 'wider is faster' theory. However, if I raced on poor roads, I'd go with a 700x23 or 25mm...ymmv.

Ergo - smooth roads > thinner and harder; rough roads > wider and softer. Those are my opinions - not to be equated with Matthew, Mark, Luke, or John's gospels.

Got nothing against nerds. Even the nerdiest of nerds can offer up incomplete info as gospel. I like to think of myself as a geeky jock who's been known to offer a mulligan or two in my career...no problem.