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  1. #1
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    flat statistics - front versus rear

    I had a flat last night, rear wheel, of course, a needle-like piece of wire had pierced the tire. On the plus side, the flat happened literally a hundred yards before the end of the ride so I could just walk the bike home and repair there.

    So, this got me thinking: As long as I can remember, I have never had a flat on the front wheel. I cannot completely rule out that I had one or two front flats in roughly thirty-something years of serious cycling, but if so that must have been a long time ago, and I don't remember any such case. In contrast, I typically deal with perhaps one flat or so per season, maybe a little less. So that makes a ratio of easily 30 rear flats for every one in the front.

    Now, I know about how the rear wheel is more highly loaded, and it's the driven wheel and all of that, but, 30 to 1? That wire last night would have pierced the front tire just as neatly as it did the rear, yet that practically never happens. Do others have the same experience? Is there a good explanation for this extreme discrepancy?

  2. #2
    wim
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    The late Jobst Brandt wrote about this in many of his entertaining (some would say "infuriatingly condescending") posts on the usenet. He believed that the front tire disturbs and positions the offending object in such a way that it has an easy time puncturing the rear tire. This does make sense to me, but only because I've observed the front tire kick up small sticks which landed in the rear wheel or rear derailleur. I'm not sure if anyone has ever seen a tiny piece of steel wire being positioned by the front wheel to puncture the rear.

    My front-to-rear flat ratio experience mirrors yours to some degree--and I'm one of those stupid but frugal people who rotate a worn rear tire to the front. You would think that my thin front would flat more, but it doesn't.
    Last edited by wim; 05-13-2016 at 04:32 AM.

  3. #3
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    I would say my ratio of rear to front flats is about 10:1.

    That one in front being F&^() catastrophic LOL.

  4. #4
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    Maybe 1/10. I'd think weight distribution would be a factor with some but certainly not a lot of them.

  5. #5
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    Quote Originally Posted by wim View Post
    The late Jobst Brandt wrote about this in many of his entertaining (some would say "infuriatingly condescending") posts on the usenet. He believed that the front tire disturbs and positions the offending object in such a way that it has an easy time puncturing the rear tire...
    Not a crazy theory... but if it were a significant contributor to rear flats, I'd expect to see the same results from the rear wheel of the rider in front, "positioning offending objects" for the front tire of the following rider... which doesn't seem to bear out in our anecdotal statistics.

    And yeah, I'm in the same 1:10, 1:20 or so ratio of "always seems to be the rear". As cool as Brandt's theory is, I suspect the reason(s) is/are much less interesting: More weight on the rear = glass/wire/shards, etc. just seat deeper. And, pinch flats... lots more pinch flats.

  6. #6
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    since I retook up cycling a few years ago... 3 rear 1 front.My one front I hit a large rock @ 25mph in a pace line that was not pointed out..almost wrecked and yes I was kinda pissed.

  7. #7
    wim
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    Quote Originally Posted by OldZaskar View Post
    I'd expect to see the same results from the rear wheel of the rider in front, "positioning offending objects" for the front tire of the following rider... which doesn't seem to bear out in our anecdotal statistics.
    You're right, I never thought of this. Too bad, could have used it when good old Jobst was still around beating up on fellow posters....:-)
    Attached Thumbnails Attached Thumbnails flat statistics - front versus rear-bernina.jpg  

  8. #8
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    flatted on the front last week.

    can't even recall the last time that happened.

    r:f ratio...? easily 20:1, maybe higher...

  9. #9
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    Weight distribution, sure, plays a role. I would say the major role.

    And, as we all know, rear tires wear faster. Less tread means more flats.

    Also, most people know where their front tire is tracking, but often they don't know where the rear is tracking. So you might swerve a bit to go between two bits of debris, but the rear might hit one of those bits. This is pretty evident on the MTB for most people, when the rear tire hits the rock the front missed on a turn, but not all that evident on the road.

    It is also easier to see off center bits picked up on the front, and brush them off, before they get driven deep on a turn.

    That's all I can think of off the top of my head.
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    Quote Originally Posted by wim View Post
    The late Jobst Brandt wrote about this in many of his entertaining (some would say "infuriatingly condescending") posts on the usenet. He believed that the front tire disturbs and positions the offending object in such a way that it has an easy time puncturing the rear tire. This does make sense to me, but only because I've observed the front tire kick up small sticks which landed in the rear wheel or rear derailleur. I'm not sure if anyone has ever seen a tiny piece of steel wire being positioned by the front wheel to puncture the rear.

    My front-to-rear flat ratio experience mirrors yours to some degree--and I'm one of those stupid but frugal people who rotate a worn rear tire to the front. You would think that my thin front would flat more, but it doesn't.
    Yep, that's it. Same thing on vehicles.

  11. #11
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    I have had one flat that I know was due to the front tire flipping up debris just so- it was a bolt that went through the rear tire, tube and aluminium rim.

    My front/rear flat ratio is about 1/3 front 2/3 rear.

  12. #12
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    I'd also say about 10:1 ratio.

    In a similar vein though, when I was commuting in all weathers, it was very noticeable how the rear rim and brake track got much dirtier than the front.
    There's sometimes a buggy.
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  13. #13
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    In the past year, I've gotten one flat identical to the way Pirx did; I had a 1/4" metal sliver puncture the rear tire. I have also found deeply embedded shards of glass in the rear tire, but not deep enough to puncture the tube. Nothing in the front yet.

    When I used to ride my MTB on trails in SoCal, it was a much closer ratio... probably 2:5, lots of goat head thorns.

  14. #14
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    I hesitate to refer to the "F" word in a public forum for fear of invoking the wrath of the F _ _ _ faerie, but the ratio I have experienced is similar to that of the OP and others, 1:bunch.

  15. #15
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    Of the 6 or so flats my group had in the past year, they ALL were rear flats.
    Wilier GTS W/helium filled tires
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  16. #16
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    IMO it's about 10:1 rear/front.

    Reasons:

    - rear carries more weight
    - the front can be steered to avoid an sharp object...
    - ...only to be run over by the rear!!
    - when hitting a pothole, the front is often times lifted up by the rider, while the rear hits it with full force. Boom!

    all in all, the rear flats more due to 2 main things: more weight and the inability to be steered

  17. #17
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    I've flatted a front tire I think twice in the last 3-5 years, about 2-3 years ago I was cross racing and while running 28psi on clinchers with tubes,which usually worked for me, even on a set of wider Belgium + rims I pinch flatted the front, I was off the front some and not far from getting the bell lap...not sure if I could hold onto the lead for the entire last lap...then Game over!! So that is the main motivator for me going tubeless on the cross bike, for cross racing and gravel ridding. Also had a front pinch flat while ridding gravel roads 2-3 years ago, was more of a short rocky trail section where I pinch flatted the front, not far from where I had parked the car, this was with the same Continental cyclocross speed file tread tire I had pinch flatted in the cross race, but on a narrower Open pro rim this time, I had put some Stans into the latex tube and that helped it keep some air a little longer, to limp the last 1/4 mile or so back to the car, and then I got out the regular pump from my car and pumped it up and it actually held, and I went back out for a little more of a ride. On a different ride I had similar sealant and latex tube combo on the same tire and rim and had a rear pinch flat, inflated the tire a bit with my frame pump, but it wasn't sealed well enough, and had to change the tube out a mile or so of ridding later.
    Not sure the last time or if I've had a front flat on a actual paved road ride, also been awhile since I've had a mountain bike flat, had a rear flat on the lead out lap on a 24HR mountain bike race-on a team of 4- had a good lap going feeling great and rode over a horse shoe nail, right through the back tire, and right through the tube, not too long after that I went tubeless for mountain bike, though not sure if that would have sealed up tubeless, it's pretty big hole

  18. #18
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    Quote Originally Posted by QuiQuaeQuod View Post
    Weight distribution, sure, plays a role. I would say the major role.

    And, as we all know, rear tires wear faster. Less tread means more flats.

    Also, most people know where their front tire is tracking, but often they don't know where the rear is tracking. So you might swerve a bit to go between two bits of debris, but the rear might hit one of those bits. This is pretty evident on the MTB for most people, when the rear tire hits the rock the front missed on a turn, but not all that evident on the road.

    It is also easier to see off center bits picked up on the front, and brush them off, before they get driven deep on a turn.

    That's all I can think of off the top of my head.
    Most people's rear/front weight distribution is in the 60/40 range which isn't that great of a difference so I have a hard time buying that argument. A 200lb guy doesn't get 20x the flats a 160lb guy does, all variables being equal (tire make, size, pressure, etc...).

    WRT a correlation between r/f flat ratio and r/f tire longevity, I don't think tire casing thickness has anything to do with it. If one doesn't rotate their tires front to back (and I suspect most people are in this category), each tire has the same average casing thickness over it's usable life.

    My theory is that the driving tire action is more likely to "grind in" puncturing debris than the front tire which "glides over" such objects.

  19. #19
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    I am running a rear to front ratio of 4:1 on this bike. The last front was after trying to navigate a wash out of rocks at speed. Caught a rock at just the right spot I guess to nail the side of the tire. Continuing down the hill with a front tire going flat was a bit hair raising until I was able to safely come to rest.

  20. #20
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    Quote Originally Posted by cooskull View Post
    Most people's rear/front weight distribution is in the 60/40 range which isn't that great of a difference so I have a hard time buying that argument.
    20% difference is not insignificant. Especially when one tire is always rolling, and the other tire is being driven by the rider... adding extra forces in the situation.

    And for that ratio, is it that every second of every ride? Of course not.

    How often is is 80/20 compared to 20/80? How often to people take all the weight off the front, and how often do they take all the weight off the rear?

    What happens when the road turns up for a climb? What happens when people stand on a climb?
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  21. #21
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    I expected to read this thread and immediately think to myself that the OP surely must have too much time on his hands to be pondering such a silly subject.

    But then I thought about my years of MTB, road riding, AND car driving. In each case, I'm certain that rear flats have occurred far more frequently than fronts. In the case of automobile use, between my cars, my wife's, and my work vehicles, I've changed about 7 flats - all of them on the rear.

  22. #22
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    Quote Originally Posted by cooskull View Post
    Most people's rear/front weight distribution is in the 60/40 range which isn't that great of a difference so I have a hard time buying that argument. A 200lb guy doesn't get 20x the flats a 160lb guy does, all variables being equal (tire make, size, pressure, etc...).
    Pretty sure 200 isn't 20x 160.

    And I doubt the group I ride with in totally unlike others in that the heavier guys definitely get more flats than the anorexic types.

  23. #23
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    If I recall correctly I can only remember having one (1) front tire flat since 2009 and that was about 3 years ago... knock on wood I don't have too many flats, most of my spare tubes are handed out to other riders who are in need

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  24. #24
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    I agree. In my group, the ratio of front to rear flats is easily 1:10. In my experience, the majority of flats aren't punctures but pinch flats. People hit a pothole or other obstacle, bottom out the tire and cause a flat. To me, it makes sense that rear tires would take the bulk of these types of impacts and it seems reasonable that rear tires would flat more often as a result. The fact that I've found running higher pressures drastically reduces the chances of me flatting seems to bolster my theory.

  25. #25
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    Quote Originally Posted by cooskull View Post
    Most people's rear/front weight distribution is in the 60/40 range which isn't that great of a difference so I have a hard time buying that argument. A 200lb guy doesn't get 20x the flats a 160lb guy does, all variables being equal (tire make, size, pressure, etc...).
    I tend to agree, I don't think the weight difference can explain such a large difference in flat rates. On the other hand, that steering argument has something to it. Pinch flats, sure, pretty much rear-only, but I have practically never had a pinch flat, and my ratio is still higher than 20:1 even without those. Jobst Brandt's argument about the front kicking up crap in just the right way may have some merit too, as unlikely as it may sound.

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