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  1. #1
    Senior Member Brian Sharpe's Avatar
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    Dumb Newbie Question about tires

    I have a Marin hybrid bike that is equipped with the Alexrims T19 rims and 700x35c tires. For just recreational riding & a bit of commuting the bike has been very satisfactory but I'm trying to push a little better performance out of it and was wondering if going to a narrower tire (a 28 or 32) would make any noticeable difference in terms of rolling resistance.

    It has the origina Kenda Kwest tires on it - would I accomplish the same objective by going to a lighter/faster tire (eg a Schwalbe Marathon Racer (420g) vs a Marathon Plus (890g)

    I know I'm eventually going to need a real road bike but I'll need to save up my pennies for that!

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    How much do you weight and what tire pressure are you currently running?

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    LET'S ROLL 1nterceptor's Avatar
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    I used to have a hybrid that originally came with 700X40 tires,
    switched to 700X28 front and 700X32 rear. Bontragers I think,
    slicks max pressure 110 psi. Very little change in speed, it was
    when I lost 30 lbs. that I really felt some improvement in my speed.

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    Bicycle Repair Man !!! Sixty Fiver's Avatar
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    I find the Kenda Kwest to a very slow rolling tyre and the wet weather performance has not inspired me either.

    The standard Marathon offer a nice balance of speed, handling, and all weather performance and unless you live in goathead central should not need the Mplus as the standard tyre offers decent puncture protection.

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    Senior Member meanwhile's Avatar
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    Look at the threads about the same subject from the past few days. Basically: tyre quality is what sets RR. You can buy fast 35mm tyres like Sports Contacts, Marathon Racers, or Supremes and keep the advantages of the wider size. Of these the Supremes have the best grip and puncture protection. (Contacts can be a little scary in the wet.)
    Last edited by meanwhile; 09-11-10 at 11:51 AM.

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    Or you can buy the same fast tires in narrower widths and go even faster.

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    Bicycle Repair Man !!! Sixty Fiver's Avatar
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    For urban riding a wider and faster tyre makes better sense and this is why we probably see more mtbs on the road here than anything else... our winters wreak havoc on our roadways and potholes and ruts are a fact of life.

    Run skinnies and those little ruts become a much bigger deal.

  8. #8
    Senior Member meanwhile's Avatar
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    Quote Originally Posted by qmsdc15 View Post
    Or you can buy the same fast tires in narrower widths and go even faster.
    ...If you either simplify the matter to the level of idiocy or are a very fast rider on an aerodynamic bike and in the mood to hustle, then yes.

    If two tyres are the same then the wider one has lower RR; a narrow tyre can still be faster for high power output because it is more aerodynamic and that counts more above a certain speed - which is generally one you should switch to a bike with drops for. People who are too lazy to read the docs provided with by the tyre companies find this very confusing and/or annoying... http://www.schwalbetires.com/tech_in...ing_resistance

    ..The bottom line is that for a typical commute speed a 35mm-40mm made of fast rubber is probably as efficient a choice as any other and offers more safety and comfort than a skinnier tyre.
    Last edited by meanwhile; 09-11-10 at 05:15 PM.

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    Quote Originally Posted by meanwhile View Post
    If two tyres are the same then the wider one has lower RR; a narrow tyre can still be faster for high power output because it is more aerodynamic and that counts more above a certain speed
    Woah, apples and oranges here.

    The document talks about rolling resistance, and that at speeds of 20km/h air resistance is the main resistance force. I understand this to mean ALL air resistance, to include all the air pushing on the bike and rider. Further down it mentions that narrower tires have less air resistance and that this is an advantage at speed. It sounds like (and I could be wrong) that you mixed both pieces of information and came up with 'narrow tires are only less rolling resistant than wide ones because of them being more aerodynamic at speed.

    Doesn't work that way. Skinner tires can be pumped at higher pressures, thus having less deflection than a fat tire could ever dream off, and here lies most of their lower rolling resistance.

    OP: how much do you weight and what pressure are you running with? Without knowing this is is hard to offer meaningful advice.

    Basically your tires are (among other things) your first line of suspension; you can change the whole way your bike feels by changing tires and pressure. Depending on your weight a given set of tires will have an ideal range. For the sake of this argument let's say that for your weight, you can pump a set of ACME touring tires between 90 and 120 PSI. The lower range will give you a nice and soft ride, at the expense of rolling resistance (the tire will yield more, putting more rubber in contact with the road). At 120 PSI the tire will deflect the least, but every time you hit a pebble you will feel it. Also, your bike carries more weight on the back, which is why most folks have lower tire pressure on the front. This softens the ride and keeps a lot of road vibration from rattling you through your arms.

    I'm currently running 90psi front 110psi on the back. For a long ride I did 115psi front and back, never again.

    My buddy doesn't check his tire pressure as often as he should. I can tell every time he is running low by the fact that on downhills, he has to pedal to keep up with my coasting.

  10. #10
    Senior Member Brian Sharpe's Avatar
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    Quote Originally Posted by meanwhile View Post
    If two tyres are the same then the wider one has lower RR; a narrow tyre can still be faster for high power output because it is more aerodynamic and that counts more above a certain speed - which is generally one you should switch to a bike with drops for. People who are too lazy to read the docs provided with by the tyre companies find this very confusing and/or annoying... http://www.schwalbetires.com/tech_in...ing_resistance

    ..The bottom line is that for a typical commute speed a 35mm-40mm made of fast rubber is probably as efficient a choice as any other and offers more safety and comfort than a skinnier tyre.


    Very interesting read - thanks!

  11. #11
    Senior Member Brian Sharpe's Avatar
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    abdon - I'm 200lbs & running 80psi.
    Last edited by Brian Sharpe; 09-13-10 at 07:48 AM. Reason: fumble fingers!

  12. #12
    Senior Member Brian Sharpe's Avatar
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    Quote Originally Posted by Sixty Fiver View Post
    For urban riding a wider and faster tyre makes better sense and this is why we probably see more mtbs on the road here than anything else... our winters wreak havoc on our roadways and potholes and ruts are a fact of life.

    Run skinnies and those little ruts become a much bigger deal.
    Winters here in Ottawa do the same - I think we're the pothole capital of the universe.

  13. #13
    Sumerian Street Rider khutch's Avatar
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    Quote Originally Posted by abdon View Post
    Doesn't work that way. Skinner tires can be pumped at higher pressures, thus having less deflection than a fat tire could ever dream off, and here lies most of their lower rolling resistance.
    Not always.

    If you want to talk sensibly about tire performance you first have to define your perspective. Are you racing, training, or distance riding? If you are not doing one of those three then tire performance, as long as they grip the road, is no real issue for you. If you are training then you actually might want a high resistance tire so that your engine develops a cushion of power that you can use on race day with better tires to crush the competition. If you are racing, formally or just trying to best your buddies or your personal best, then any increase in performance is worth chasing since a win only has to be by a millimeter if the timing is accurate enough. If you are distance riding then I presume your main interest in tire performance is so that you feel fresher at the end of the ride. In that case only a fairly large change in tire performance is going to have a noticeable effect. If you can't get a 5% or greater reduction in your total effort for the ride then you are unlikely to notice the difference. I'm not sure that this level of improvement can be gotten from tire changes. There is little to no quantitative data available and all the hype you are going to read about tire performance is race related where a 0.01% difference can win an event.

    There are other factors that drive the selection of tires too. For a distance rider on open roads durability, especially puncture resistance, is an important factor. Comfort is important too but there is no point in discussing that since we have no quantitative data and the discussion will always degenerate to focus on raw efficiency anyway. Terrain is also important. High pressure tires don't roll over rough surfaces as well as low pressure tires will. A distance ride on open roads may involve rougher surface conditions than high inflation pressures will be efficient on and pressures low enough to be efficient may demand wider tires to prevent pinch flats.

    The aerodynamic performance of a tire can be important but for a distance rider who is not racing it is of secondary importance at best. The reason for this is that the rider is much wider and taller than the tires and is likely to have a higher drag coefficient. The bike frame and mechanism is also likely to have at least as high an aero drag contribution as the tires/rims. For a lot of riders I'm not sure the aerodynamics differences matter enough to worry about. But of course in a race everything is important.

    But if you want to ignore all that and focus on rolling resistance you can. Even rolling resistance is complex. Most of it comes from tire flex and there are two ways to reduce tire flex: higher pressure and wider tires. There is a third factor that is less often considered in these discussions and that is the effect of tire flex. Tire casings made from high thread count fabrics with thinner rubber layers are more efficient at any given amount of tire flex than those with low thread count fabrics and thick rubber sidewalls. Another factor that is usually not considered is the load (weight) on the tire. The 23 mm, 145 psi tires that 145 pound professional racers use were optimized for them. Without a lot more information than we typically have it is impossible to say that a 185 pound rider would not be better off on 38 mm, 95 psi tires.

    Even the assumption that skinny tires run higher pressures is generally but not strictly true. Vittoria makes 700c road tires in widths from 20 to 28 mm and they all run the same maximum pressure, 145 psi. Switching from 23 to 28 mm carries no penalty in inflation pressure and a heavier (heavier than 145 pounds?) rider might be better off on the 28 mm tire. Vittoria makes 150 threads per inch (tpi) tires in widths up to 28 mm. If you want the higher efficiency of their 220 tpi and 320 tpi tire casings you are limited to 25 mm in maximum width. Again, if you weigh much more than 145 pounds and you want the highest efficiency casings I suspect you are better off on the 25's.

    If you are as concerned about puncture resistance as efficiency you might instead consider their better protected "city trekking" tires. If you look through their catalog you will see that some of their widest tires run at the highest maximum pressures for those series'. Their "absolute best" Randonneur Hyper tires run at 70 psi in the 32 and 35 mm widths, 95 psi in the 38 mm width and they have 120 tpi casings that should be reasonably efficient. None of those tires runs more than 95 psi even though they go as narrow as 25 mm. Their 28 mm Randonneur (reflective sidewall) tire runs the same 70 psi as its 48 mm cousin. Continental tends to relate pressure and width as you would expect from the received wisdom but even they offer 85 psi touring tires over a fairly wide range of widths up to 42 mm and nothing wider than 28 mm goes higher in their touring lines.

    Higher pressure always gives less rolling resistance in a given tire, narrower tires do not always run at higher pressure than wider tires when you stay within a given tire series where the other factors that affect efficiency are also held constant. So, when comparing apples to apples (as meanwhile said) wider tires can indeed have lower rolling resistance.

    Ken

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    Brian,

    Khutch went into far more detail that I had time for and his post is golden. Save it on your favorites so you can reference it from time to time

    Start by riding your current at max PSI. If yours can take 100psi, go there front and back. With this you will experience first hand what it feels to sacrifice shock absorbing on the altar of rolling resistance. Whether you go 28 or 32 boils down to this; with the 32s, you can ride at a lower PSI without having to worry about pinching a flat. It's all about where you want your compromise to be, and what pressure range a given tire will give you based on your weight class.

    Regardless of what you are running with, you should get in the habit of checking tire pressure on a regular basis and adjusting your pressure depending on what you are riding that day. I have two sets of tires for my steel frame bike. I run 25c for the daily grind but if I'm going touring, I switch to 28c. (On my case not only I like more suspension on the open road, but my skinny tires are horrible when wet).

    Heck, that's the ticket. Get them both

  15. #15
    Slow But Handsome Mild Al's Avatar
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    Brian Sharpe--

    You've just discovered what all newbies soon discover: never ask about tire pressure/width/diameter unless you want to start a "tire war." (Back in the old days, I inadvertently started a few of them myself!) If you ask 10 cyclists about tires, you will get at least 12 or 13 opinions, all of which will be supported by plausible-sounding arguments.

    Okay, here's my 2 cents: I like wider tires. I used to have 35mm tires on my hybrid, and they were fine. On my current bike, I have 40-559 street tires, which are fast enough for me. But then, I'm slow anyway, so I figure I might as well have a cushy ride.

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    Quote Originally Posted by khutch View Post
    Not always.
    But as a general rule ... yes.

    Quote Originally Posted by khutch View Post
    But if you want to ignore all that and focus on rolling resistance you can. Even rolling resistance is complex. Most of it comes from tire flex and there are two ways to reduce tire flex: higher pressure and wider tires.
    You sure about that, ie., wide tires reduce flex ? At any rate, you just confirmed what he was saying in a backhanded way.

    Quote Originally Posted by khutch View Post
    Even the assumption that skinny tires run higher pressures is generally but not strictly true.
    But that is all he was saying. Any statement can be nitpicked.



    Quote Originally Posted by khutch View Post
    Higher pressure always gives less rolling resistance in a given tire, narrower tires do not always run at higher pressure than wider tires when you stay within a given tire series where the other factors that affect efficiency are also held constant. So, when comparing apples to apples (as meanwhile said) wider tires can indeed have lower rolling resistance. Ken
    This is an unnecessary complication (and a convoluted one at that) of a straight forward generalization that, for all intents and purposes, can be relied on when assessing everyday tire performance and choice vis a vis rolling resistance. Yes, there are exceptions, but that in no way negates a broad and valid generalization.
    Last edited by Talldog; 09-15-10 at 06:20 PM.
    In theory there is no difference between theory and practice. In practice there is. - Yogi Berra

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    Quote Originally Posted by Sixty Fiver View Post
    I find the Kenda Kwest to a very slow rolling tyre
    That is contrary to my experience and the experience of many others. Maybe you are speaking in a relative sense ? I hope you are not passing judgement on them based on the Canadian Tire version of the Quest ? If so, then I would probably agree.
    In theory there is no difference between theory and practice. In practice there is. - Yogi Berra

  18. #18
    Sumerian Street Rider khutch's Avatar
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    Quote Originally Posted by Talldog View Post
    You sure about that, ie., wide tires reduce flex ? At any rate, you just confirmed what he was saying in a backhanded way.
    Meanwhile linked to the Schwalbe discussion that explains why, I don't believe that any actual tire makers disagree.

    But that is all he was saying. Any statement can be nitpicked.
    There is a difference between nitpicking and addressing an over simplification. Einstien's rule, not mine.

    This is an unnecessary complication (and a convoluted one at that) of a straight forward generalization that, for all intents and purposes, can be relied on when assessing everyday tire performance and choice vis a vis rolling resistance. Yes, there are exceptions, but that in no way negates a broad and valid generalization.
    It is not a complication at all. In many cases when you make an apples to apples comparison the wider tires in a series will run at the same pressure as the narrower ones in the same series. What you term "exceptions" are quite common among the two brands of tires I looked at. Comparing a fairly delicate 320 tpi racing tire to a tank-like 27 tpi balloon tire is nonsensical, yet that is what people generally do. If you want to pick more efficient tires then you have to look at all the factors that effect efficiency to make an intelligent choice. And you have to be prepared to make the tradeoff between a tire optimized for speed over everything else versus reasonably efficient tires that shrug off the slings and arrows of outrageous fortune with a smile. And you have to understand that your weight is an important factor. If you are a clyde who is trying to best a buddy with the physique of a horse racing jockey that 17 or 20 mm tire that serves him so well will not work as well for you. Find a 25 mm or 28 mm tire in the same series and pressure as he is using and you will make the playing field more even. Truth be told a whole lot of us are closer to clydes than jockeys, telling us all to use the jockey's tires is not good advice.

    Personally I don't want to have to deal with the flats that the super tires with 320 tpi casings are likely to give me on the routes I ride. I'm looking for good medium width touring tires in the 100-200 tpi range with some of that efficiency robbing puncture protection built in. And I'm not going to pump them up to max pressure, I'm going to run them for about 15% tire drop for better comfort and better efficiency when the trail gets rough. Tire selection is an engineering tradeoff between efficiency, hazard resistance, and comfort. If you do not think through the engineering you are not going to make the best tradeoff. You are just going to buy the 23mm tire and run it 20 psi over the max, because that is what your buddies do. As for me and my house we are going to try the Vittoria Randonneur Hypers or Pros. I would have said 38 mm but with my new wider rims I think 35 mm may be as wide as will fit the frame.

    Ken

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    Quote Originally Posted by khutch View Post
    Meanwhile linked to the Schwalbe discussion that explains why, I don't believe that any actual tire makers disagree.
    In the interest of addressing an over simplification, that is not exactly what they (Schwalbe) are saying, but hey, I think nitpicking describes it better.
    In theory there is no difference between theory and practice. In practice there is. - Yogi Berra

  20. #20
    Bicycle Repair Man !!! Sixty Fiver's Avatar
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    Just swapped the 28:622 Marathons on my hybrid for 35:622 Schwalbe CX Compes...

    Have run both types of tyres in the past and find the CX gives up little, if anything to the narrower (and heavier) Marathon in the speed department despite running a lower psi, the bike handles like it is on rails, and the ride quality is astounding.

    They are also puncture resistant but not to the same degree as the Marathon.

  21. #21
    Sumerian Street Rider khutch's Avatar
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    Quote Originally Posted by Talldog View Post
    In the interest of addressing an over simplification, that is not exactly what they (Schwalbe) are saying, but hey, I think nitpicking describes it better.
    You are clearly nitpicking semantics. If you did not understand the Schwalbe discussion here is another one that has more detail and a better explanation of the effects of tire width.

    Ken

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    Quote Originally Posted by khutch View Post
    You are clearly nitpicking semantics. If you did not understand the Schwalbe discussion here is another one that has more detail and a better explanation of the effects of tire width.

    Ken
    Thanks anyway, but I do understand completeley how it works.
    In theory there is no difference between theory and practice. In practice there is. - Yogi Berra

  23. #23
    Senior Member AdelaaR's Avatar
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    Quote Originally Posted by Mild Al View Post
    You've just discovered what all newbies soon discover: never ask about tire pressure/width/diameter unless you want to start a "tire war." (Back in the old days, I inadvertently started a few of them myself!) If you ask 10 cyclists about tires, you will get at least 12 or 13 opinions, all of which will be supported by plausible-sounding arguments.
    This may be true and many people may use plausible-sounding arguments.
    However: what Ken and meanwhile said about the subject does not fall into that category.
    There is such a thing as "simple physics" and one can simply not argue with science, right?
    What Ken & meanwhile said about tyres is basicly just how it is, regardless of what "10 cyclists" may come up with as "plausible-sounding arguments"

    Narrow tyres will only help once the bike reaches a certain speed.
    The OP did not mention how fast or how slow he rides and so we can not determine if narrow tyres would help him.
    But, as Ken said: if one is not racing ... a wider tyre will be more suited.

  24. #24
    Slow But Handsome Mild Al's Avatar
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    Of course, some arguments are plausible-sounding because they actually ARE plausible!

  25. #25
    Senior Member AdelaaR's Avatar
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    Quote Originally Posted by Mild Al View Post
    Of course, some arguments are plausible-sounding because they actually ARE plausible!
    I'm affraid you are still not getting it.
    They aren't "plausible" ... they are simply "scientifical".

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