Tire replacement - when/how often should this be done?

Discussion in 'Road Cycling' started by xplicity, Jan 14, 2012.

  1. alienator

    alienator Well-Known Member

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    I've got some 25mm PR3's. On my 23mm wide A23 rims, the PR3 is 27.4mm wide, and on my Kinlin XR250 (19mm wide), the PR3 is 26.1mm wide. Michelin seems to be pretty honest about tire width. That's much better than the manufacturers that try to win the weight game by making a tire narrower than its stated spec just so they can save a small handful of grams. I'll gladly take a tire that is a little wider than its stated spec.

    I'm looking forward to reading some reviews of PR4's.
     


  2. alienator

    alienator Well-Known Member

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    Yup. Finding the Higgs Boson is a lot easier than cracking that flat mystery. The only time I can reliably predict flats is during the monsoon here (and then I only know the flat rate is likely to go up), when all the trash, sharp rocks, goatheads, cactus needles, and other pointy things get washed out onto the pavement. About 4-5 years ago, right in the middle of the monsoon season, I had a 2 week period during which I had 10 flats: 4 on tubulars, and 6 on clinchers. Oddly enough, I developed a pretty damned surly attitude--as well as sore thumbs from stitching repaired tubies back together--during that period.
     
  3. Froze

    Froze Well-Known Member

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    Don't you think a testing site that has only a few tires being tested and advertised by Conti might be just a wee bit bias? Here's a site that is completely unbiased, tested around a hundred different tires, and shows the "god of tires" - Conti tire to be nothing more then just about average. http://www.biketechreview.com/tires_old/images/AFM_tire_testing_rev9.pdf

    Personally I don't happen to like Conti road tires, I've tried them at various times throughout the years and they always tend to be fragile in both protection and longevity, and they cost more then their worth. However, I've had really good luck with their MTB tires that tend to be tough and long lasting, and which they discount more then road tires at sale or closeout time.

    Nowadays I refuse to spend more then $25 to $29 tops for a tire. My last big purchase was 4 pairs of Kenda Konstrictors normally $40 on sale for $19 each, these tires are easily better then the Conti GP4000's that I had previously. I did buy a pair of Vittoria Rubino Pro Slick that was on sale for $29 each normally $50; so these tires were on the top of my willingness to pay, but I wanted to try Vitts because I can't recall ever using them, and the Pro Slicks got high reviews, but I won't be using then till sometime next year. There are lots of nice tires that go on sale or closeout all the time for around the mid 20's price range reduced from $50 to $60 range that even get high reviews, there's no reason in my mind to pay $50 plus for a tire unless your racing.

    By the way, I don't buy tires according to some rolling resistance test, I don't race so I don't care how fast they roll. And the reason I won't spend more then 25 to 29 dollars is because I have a tough time spending $50 or so for a tire that will only last an average of 3,500 miles...that's like paying $700 for a car tire!! I won't do it. Call me weird for thinking that way.
     
  4. danfoz

    danfoz Well-Known Member

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    Could be somebody on Conti's board of dir's is in bed with someone at the Geman Magazine in question, or they posted the review on their site because an independant source declared their tire the winner. Who know's? Back in the day when Bicycling magazine used to "objectively" road test bikes it was usually just a couple of bikes, not every bike on the market. How long would it take to test hundreds of tires, probably some time.

    I have used the BikeTech review testing and even referenced it on this very forum. It's a good source. It is interesting that the Conti's are some way down on their list of RR performers.

    In twenty+ years on the bike I have ridden way more than two different tires along many different price ranges. I also have a good personal sense to subjectively assess a tires ride quality. I do not own a Mercedes but I'll tell you that slamming the door on one feels completely different than slamming a door on an old Ford. I have ridden the Rubino Pro's. I didn't flat once over a couple thousand miles and the tread lasted quite long. However to me they feel like shit and are completely unresponsive. I pay a lot for tires because I spend a lot of time on the bike. I have ridden a lot of tires that people have recommended for some reason or another (seems like everyone thinks THEIR pizzeria is the best). I use CX's for both training and racing because they feel nice. IMO Conti's are a compromise, but they do seem to last longer.

    It's doubtful that in the real world of my own road racing, quite entry level in the overall scheme of things, that RR is going to have any effect on my result. The way that lovely 320tpi CX tire feels under my ass however has everything to do with my enjoyment of riding.

    Maybe there are cheaper tires that feel just as nice. But I've tried a lot of pizza and I will tell you that the pizza at my local joint is the best there is /img/vbsmilies/smilies/wink.gif
     
  5. alienator

    alienator Well-Known Member

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    In Tour's defense, they do a pretty spiffy job of testing bits. They definitely are a technically oriented magazine. Their tire test was pretty good, although the worthiness of their cornering rig is questionable. I don't think there is any bias towards Conti in their testing. Likewise, I don't think there's any bias toward a given company in Bicycling's efforts to "test." I do think Bicycling displays a significant lack of creativity or, in the case of bikes chosen to test, a lack of motivation to test anything that isn't from their common, small pool of the same 5 - 7 brands they always test. Still, Bicycling is not meant as a technical rag. With the exception of a few stories, BikeSnob, and the Bob Mionske bits, Bicycling is pretty much the Reader's Digest of bike rags. It is perfectly suitable for toilet reading, unless you have really bad constipation, in which case you just might finish an issue well before finishing your peristaltic exercise.

    With tests done to measure Crr and other such performance variables, test setup, assumptions about variables, test procedures, and data reduction methods can all impact the results. As such it's very possible to see differences in outcome like you see between the AFM and Tour test results. Note that Tour's cornering test can introduce signifiant variance into the data since it would be next to impossible for each test run to trace exactly the same arc through a given corner, covering exactly the same tarmac.

    There is a newish cycling test facility in Finland, The Wheel Energy Tire Testing Laboratory that, among its services, offers rolling resistance testing. They've got a physicist on board doing their testing, and I'm hoping someone contracts them to do an updated rolling resistance test series for bike tires.

    Crr can of course be significant. If AFM is using the standard expression of Crr in a force term [Crr*m*g*cos(θ), where m is the mass of the bike/rider system, and θ is the angle between the road and a horizontal plane], then Conti GP4000s (Crr=0.00284) tires would produce about 232g of rolling resistance, whereas the best tires in their test, Vittoria Pista EVO CS tubies (Crr=0.00220) would produce 179g of rolling resistance. The Tufo (Tufo is Lithuanian for "rides like a wagon wheel") S33 would produce 381g of rolling resistance. Of course, those values are all done on Tacx PVC rollers. On the road, the Crr would be significantly higher.

    It really doesn't matter if someone is concerned about Crr or not. It's one of those personal preference things. I can understand the urge to use, even when not racing, low Crr tires. I love fast descents, and I could see someone using such low Crr tires just so they can "sail" much faster. Speed is a powerful drug (Danfoz, no double entendre intended here).
    I liked the feel of Vittoria EVO Corsa CX (as well as KX) tubies, but they were difficult to justify in my local riding environment. They are virtually invisible to thorns, cactus needles, goatheads, and the most prevalent threatening vegetation, broken glass. As for Conti tires, their Crr used to suck very badly, but their new Black Chili compound has improved things a lot.
     
  6. Froze

    Froze Well-Known Member

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    By quite a bit, what do you mean? Because according to the rolling resistance web site I gave earlier the Black Chili performed at below average at rating of 18.9 watts; it's crr is 0.00384 which is also below average in the field of tires tested. So what is it you feel they've improved a lot...Comfort? Handling? something else? because it can't be speed.

    Speed wise and wattage usage I doubt anyone who doesn't race could feel even a 2 watt difference and definitely not less then a 2 watt difference; and those that do race wouldn't really feel it so much as they see slightly better results at the end of a race. 2 watts will only save you about 10 seconds over a 25 mile course (significant over a 100 mile race), but I doubt your going to feel a less then a 1/2 second gain every mile...but the end result is there. And if your just a recreational rider riding below an average of 16mph the savings of 2 watts won't matter the least bit.

    The same problem comes up with aero rim designs, you get very little aero effect until you get to between 45 and 60 mm deep rims, anything less then that doesn't do anything over standard box rims, yet people think their getting better results with a 30mm rim because they were told they do.

    http://www.biketechreview.com/tires_old/images/AFM_tire_testing_rev9.pdf
     
  7. Dave Cutter

    Dave Cutter Active Member

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    1. Not a problem.

    2. I agree! Like I stated in my original post "Sooner or later.... we all have a flat." But I didn't want to just say this is a basic skill all cyclist need to have. I tried to point out that it was actually rewarding to learn these skills.

    3. If I didn't learn something here from time-to-time I wouldn't come back. I learned a bit about repairs on a couple older bikes before I bought my new one. And, it would be a stretch to still call it a new bike. Although I do keep it looking like new. I also found the YouTube videos helpful. I do really like the LBS I use, and I don't mind if all the people there aren't perfect.

    I ride through an urban area that provides me with every road hazard I can think of. Potholes, and broken bottles are just part of the route. Although I got about 2000 miles out a cheap set of Kendra tires that came with the bike. A similar set of cheapies didn't seem to work out well. With only about 500 miles and three flats on the back tire I noticed the tire itself seemed glove soft. The Vittoria tires I switched to and am using now, seem promising. I haven't used enough tires or brand of tires to make any recommendations. I am cheap.. so I might try a few different tires and brands while I learn more about them.
     
  8. alienator

    alienator Well-Known Member

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    According to the AFM test I have in front of me, they measured the GP4000s' Crr to be 0.00284, not 0.00384. That is a very good Crr. It's very close to the Crr of a 21mm Vittoria Corsa EVO CX tubular, which is 0.00275.



    You could very well notice the difference between the Conti GP4000s and, say a Conti GP3000, the worst tires in AFM's test. It's impossible to say what will matter to a rider or not. You shouldn't confuse what matters to you with what matters to another rider. Note that someone being a recreational rider doesn't necessarily mean that person just likes to putter around. They might, for example, enjoy getting all the speed they can. Speed and maximizing it isn't just something of interest to racers.



    That's completely false. The equations that model aerodynamic forces on bikes--or anything for that matter--do not include step functions. They do not just turn on at some magical speed. There is absolutely a reduction in drag with deeper rims. It doesn't matter if those deeper rims are only 30mm deep. Perhaps the aero benefits aren't as large as a rider believes or as a marketing person has led someone to believe, but the benefits are still there. Similar to above, whether the benefits are acceptable or not is entirely up to the rider.
     
  9. Froze

    Froze Well-Known Member

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    So which tests results are correct, the site I gave of the AFM? And why is there such a difference between the two? I don't have testing equipment to verify either findings, so someone "hopefully" is not publishing false data. Or is simply the tests used different methods? Which leads us back to which method is correct, or should I say more correct?

    As far as the depth a V rim should be, I don't know if your right or wrong! I once went to a bunch of web sites and found one that did a study showing no benefits till it got to 45 and up...of course when I search the web now to post it I can't find it. But I couldn't find any web sites today that could prove anything whether shallower 30's or deeper 50's were better by wind tunnel testing! I found a lot of sites that yacked and yacked but showed no documented proof from wind tunnel testing to back the yack. Maybe you can help me with one or two?

    But I do think a lot of cycling products, not all, that promise to be faster is all hype and that hype makes people think they work and makes them think their faster. Maybe the sheer thinking that their faster makes them perform physically better without knowing their physically doing anything better.
     
  10. alienator

    alienator Well-Known Member

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    Aero drag is given by Fd=(0.5)(Cd)ρAv^2, where Fd is the force generated by aero drag, Cd is the aero drag coefficient, ρ is the air density, A is the area presented to the relative wind, and v is the free-stream relative velocity. This is the most basic form of aero drag, and more precise form will be more complicated (i.e. have more terms and possibly modulation terms) and likely will have to found numerically. No matter the case, the more complex form will be like this form in that the drag force only goes to zero when velocity goes to zero. If there's a relative wind with non-zero velocity, there will be aero drag. If there's aero drag, then a device with lower drag than a box section wheel will allow the rider to go faster at a given speed. Nowhere is there a term that causes the reduction of aero drag to "switch on" at a given speed. If this weren't the case, the aforementioned term would be incorrect, and we'd have to send physicists and engineers back to school and revamp all fluid dynamics courses. People can argue about whether the aero benefits at 10 or 15mph are significant or not, but that's an entirely subjective call.

    The AFM paper I have is attached. Given how close are the measured Crr for the GP4000 tires and for the Michelin PR3's, it would seem the data in the included paper is correct. After all, the GP4000 tires and the Mich PR3 skins perform similarly. Certainly, the Conti's don't have upwards of 50% more rolling resistance. It's important to take note of the note in the report stating that real roads (as opposed to the PVC rollers on which the Crr measurements were done) can have on the order of 50% more rolling resistance than the test apparatus. That makes Crr an even bigger factor. In light of that, it's important to note that while Crr can vary for a given tire from surface to surface, the relative of tires by Crr shouldn't change much with changes in road surface. That is to say that the tire with the lowest Crr on the test apparatus is likely--but not definitely--to have the lowest Crr on any surface.
     

    Attached Files:

  11. Froze

    Froze Well-Known Member

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    Thanks for the lesson on aero dynamics, I think I understand better now. I think that one site that I read a year or so ago that stated the aero effects of a rim don't start till you get to at least 45mm was probably in error. I did find one thing interesting in my recent search due to this post, was that a study by Zipp showed that CX-Ray Oval 14/16 spokes were more aerodynamic then bladed spokes (of course more so then round), but I had away's thought bladed were the best due to the knife like effect in the air, but the oval had less wake disturbance then any other spoke design regardless if they tested their own oval spoke or a different brand...of course they showed that their oval design was just slightly better then another company's oval design.

    The AFM test you showed is the same one I showed, and the test results for the tire in question is not as good as a slew of other tires above it. You have to go to the 3rd page down toward the lower third of the page to find the Conti 4000 Chili results, and the results of the test is 0.00384 CRR using latex tubes and a tubular tire...not a clincher which would do worst-usually anyways. The test your showing is not for the Chili compound but for the GP4000S clincher with latex tubes. Even with the GP4000S results of 0.00284 there is still a page and a half of tires that did better. A popular tire the Michelin Pro 2 and 3 (with latex tubes) did among the best for clinchers at 0.00254 and 0.00257 respectfully which translates into a 1.5 watt decrease in wattage usage. But I still believe an average rider will never feel 1.5 watts or even 2 watts.
     

    Attached Files:

  12. alienator

    alienator Well-Known Member

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    Well, you're always free to do a test that shows that riders will not notice a difference. Belief, however is neither proof nor is something worth debating. For many riders, choosing clincher is the sensible choice, the only choice, or one of several other types of choices. The Conti was 51 out of 112. Tires. Make sure to note that some of those tires that had lower Crr than the GP4000 were tubulars, time trial tires("chrono" or "light"). If you analyze data, you have to take such considerations into mind. Those factors are relevant, especially as it's not every rider that rides tubulars or time trial tires. Also, there are a number of tires in that test that aren't even available any more. Certainly, Crr is not insignificant. It's also not so small that it's out of the realm of possibility that someone could tell the difference between a "fast" and a "slow" tire, especially out on the road where, according to AFM, Crr can be on the order of 50% more than their lab derived values. I know I could damn well tell a difference between Tufo S33's and Vittoria Evo Corsa CX's--in how they rode (which encompasses several factors) at the same pressure, just as there was a difference between the Tufo's and even Conti Sprinter Gatorskins at the same pressure.....and the difference in each case wasn't in Tufo's favor.

    On a more general note, the AFM tests need to be read carefully and viewed with proper skepticism. It would be appear that some tires had an insufficient number of runs. Simply put, the more runs that a tire sees, the more the uncertainty in the measurement should go down. I noted at least one tire had only one run, and for this tire it was reported that the standard deviation was zero. That of course is strictly true since standard deviation cannot be measured for one tire. A great number of tires were only tested 2 times, which IMHO, is still low since it's debatable whether, again, a standard deviation should even be applied in the case of two. A much better option would have been to test each tire at least 5 times, but preferably 10. Also, testing used tires adds an unknown factor which could be very signficant: the change in Crr per mile used. It's well established that Crr goes down with tire wear. It has to: there is less tread and thus the hysteresis must be less since the primary mode for energy losses in a tire is through heat generation. The tests should have been standardized to one type of inner tube and possibly to one pool of such inner tubes. I'd be very hesitant to put any significance on Crr changes of 0.00005 or so given the unkowns in the tests and the varying numbers of runs per tire.
     
  13. Mark George

    Mark George New Member

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    you are so full of Sh--------------
     
  14. alienator

    alienator Well-Known Member

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    If you have an issue with anything I said here, post it. I'd be happy to discuss aerodynamics, hysteresis, and related topics. As it stands, Froze and I were having a civil discussion about those things. I assume from your "curtailed" response, you've got nothing of value to say on the topic.
     
  15. Froze

    Froze Well-Known Member

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    I agree, thanks for saying that, someone needed to.

    Back to our discussion. I tried the Tufo tires on the very high words of an LBS and was I never more severely disappointed in a tire purchase...and they weren't cheap. I tried them on the premise that they feel just like tubulars without the headaches...no, they felt nothing like tubulars and they felt sluggish, and were a pain to put on, and wore out fast. So after about 2 months I sheet canned them (they were about 75% worn out anyway) and went back to clinchers. What a waste of money that was.

    I understand there was a mix of tubs and clinchers in the test, but some tubs didn't perform all that great either, in fact you go all the way to the bottom of page 4 and you'll find the Bontrager Race Lite Tubular with a 0.00440 rating! Note, a Tufo tire is below that! But there are plenty of tubs that did worse then a lot of clinchers. So to be really fair they probably should have separated the tubs from the clinchers so it wouldn't be so confusing to those who buy clinchers and those who buy tubs. But noting that there are plenty of bad and good performing tubs that still the GP4000's only did as well as about the top 33% to 50% of the tires did, depending on which GP4000 they tested.

    The highly rated Mich Pro 2 and 3's are not racing tires, more like training/racing tires, and both performed better the any Conti that wasn't race specific. The older Specialized Mondo did better too, without a latex tube! Even the cheap Mich Axial pro lite clincher that can be had for under $25 performed better then the Conti 4000's clinchers did, and the Conti will set you back $40 unless you get the Chili version then you'll pay $75!

    I'm a tightwad, I can't see spending more then $30 for a tire that last only an average of 3500 miles. I pay far less for car tires when it comes to miles traveled. For a two $75 dollar bike tires I would have to spend $2050 for two car tires over the same 50,000 mile period if they only lasted 3500 miles! So I'm not going to spend that kind of money for a bike tire over 50,000 miles!! Call me weird, but that's my logic. So I wait for closeout bargains, and then read the reviews to make sure their not problematic; I could care less about CRR of a tire as long as I get a great deal on a highly reviewed tire.

    Certainly, now with new tire models out and a lot of the old models gone they need to redo the tests. I wonder if they will? And they should have more continuity in the test, either test all tires with latex or all with butyl, either all new tires or all 25 or all 50% worn; they didn't do that they had both mixed in; and separate the clinchers from the tubs so the comparisons are easier to read. The road thing is a variable I'm not sure they can do; the only way to test the tires is on a drum, so to simulate an average road might be impossible?
     
  16. alienator

    alienator Well-Known Member

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    I think a road surface could be simulated with a textured drum, but it might not be worth it. Using an iBike power meter, you can back out a rolling resistance value, but it takes a little bit of work. Also, the iBike power meter is very sensitive to setup.

    I don't mind paying $50-$80 or so for a clincher so long as it meets my expectations in terms of ride quality, Crr, durability, and puncture resistance. In the end, what someone feels about their tires is going to be a result of how they interpret the inputs into their bodies, so it's virtually impossible to remove subjectivity from a tire purchase. My go-to training set has been Maxxis Re-Fuse tires for some time. They don't have the lowest Crr....not even close, but they do have a nice ride, grip well, resist punctures well, and are well economical at around $25 - $30 a piece.
     
  17. ambal

    ambal Active Member

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    If you're not replacing tiers monthly, you're either not training enough or you're not replacing them often enough. /img/vbsmilies/smilies/duck.gif
     
  18. Froze

    Froze Well-Known Member

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    I've seen those Maxxis Re-Fuse tires on sale every now and again for below $30 and they get high reviews though most of the reviewers said they felt dead and sluggish, any thoughts on that? Thought about trying them out but haven't yet, thanks for the thoughts on those; next time I need a set of tires I'll try those. How many miles do you get on a set of these?

    I've been using the Kenda Konstrictor (no longer made) tires since last Spring (for $19 each from $40), and really like those. They ride a tad stiffer then the Conti due to the stout sidewall but in 3800 miles I've only had one flat, and that particular set of tires look like they'll go for at least another 1000 miles. If they go for another 1000 like I think they can, they'll be the longest wearing lowest puncture rate tire I've ever had besides the Armadillo. And the Kenda's fell like they roll pretty well.

    I haven't really cared a whole lot about comfort from a tire, in fact unless it's a tubular or using latex or some sort of paper thin sidewall tire like the Conti I can't really feel much of difference in ride quality on a 700x23 size tire. I could tell a huge difference going from a Conti Gatorskin to a Specialized Armadillo All Condition tire once in California, needless to say I didn't like the ride of the Armadillo but with goatheads penetrating any tire or puncture strip I tried the Armadillo was worth the nearly flat free ride I got. I like the feel of the Cont's GP series but their fragile and they don't last long, on top of being expensive.
     
  19. alienator

    alienator Well-Known Member

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    Maxxis Re-Fuse tires don't ride like race tires, but they're not dead, either. I think they're acceptable. They provide plenty of grip in fast corners and in the wet. I can get 3000 miles out of 'em.
     
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