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Discussion Starter · #1 ·
I bought some Specialized Fat Boys for my touring bike about 6 months ago. Believe it or not I have Specialized brand inner tubes, and Specialized brand wheels (old mtb rims). While on tour, I got a flat, and changed to another inner tube. Of course, at that time, it was raining and I wasn't in a particularly good place to change a tyre, but I got it done as fast as I could. Now here's the mystery:

At the time, once I replaced the tyre and pumped it up, I noticed there was a huge flat spot when I spun the wheel. I mean it was HUGE. About a centimetre lower than the rest of the tyre over a ten centimeter length of the wheel revolution. Hastily, I deflated, re-inflated (kneading the tyre just in case the tyre had not seated properly the first time). Same result, if slightly less of a flat spot. Because I was short on time, I just rode, and eventually tuned out the slight bump-bump-bump motion. Once I did get used to it, I rode it home like that, completing the tour.

Fast forward to a week ago, I wanted to retune my tourer -it's been sitting in my basement since I got back from my last tour last August. I remembered my experience and was determined to fix the flat spot. Here's what I did:

i. at first I thought it was the tyre ("stupid Specialized Fat Boys.... not very good quality.....should never have bought them....." etc, etc) so I thought I would change the orientation of the tyre -usually I always put the tyre label where the valve is for easier finding of the valve. I rotated the tyre around to another label (there are two labels on one side)..... pumped up to 100psi (recommended), and........

ii. the darn flat spot was still in the exact same position!!!! But it was noticeably less. "Oh no" I groaned..... "It's the rim badly out of true". I whipped off the tyre and inner tube and put the wheel on my truing stand. Hmmm the wheel was true both laterally and longitudinally within a millimetre or two. Not the rim!!! Next.....

iii. Could it be the inner tube? It was noticeable the flat spot was always at half past five. I flipped the inner tube around so that if it was the inner tube, the flat spot should now be at half past six..... which it then was -as well a slight flat spot at half past five again. Now both of these flat spots were acceptable. Then I changed the tyre position (so that no label was close to the valve) and I could hardly see any flat spot at all apart from a very acceptable very slight flat spot at half past six and a slight (but acceptable) flat spot that seemed to follow the orientation of the tyre!!

The strange thing is the Specialized inner tubes -when pumped up -do have a very slight lessening in thickness where the flat spot was, but certainly not enough to make you think that at 100psi it would hold back the inflation of the tyre. But it was.

My conclusion? I believe it's a combination of the Specialized inner tubes having deformities (where I believe the tube in joined incidentally) AND the Specialized Fat Boy tyres being slightly tighter at certain spot. My solution is to not use Specialized inner tubes, or align the tyre in such a way that where the tyre might be a bit tighter does not correspond to where the inner tube is joined.

Strange, but true..... anyone else had similar crazy stuff?
 

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Discussion Starter · #3 · (Edited)
Good guess, but I'm pretty sure it wasn't -I checked the tube had seated by inflating a little bit. Something else I should have mentioned -same thing (to a slightly lesser extent) happened on my other wheel with another Specialized Fat Boy, same type of inner tube, same type of rim, etc..... It should be noted I bought both Fat Boys at the same time, along with the same inner tubes at the same time. So maybe if there were any bad tolerances, chances are they might have been manufactured close together. I also tried a 26x1 3/8 Raleigh branded inner tube, and though there was a very slight flat spot, nothing like when I used the Specialized ones.......

It is the strangest thing I've encountered in my cycling days. If someone told me my story, I'd definitely be suspicious! But honest.....

Lifelover said:
I would have guessed you had the tube twisted.
 

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Seating the tire

To me it sounds like a classic case of the tire not seating on the rim. I have had this problem with various tires on lower quality rims, and solved it every time by dusting the bead of the tire with talcum powder. If the tire is not seated properly, it is VERY easy to see by looking at the tire/rim interface as you slowly spin the wheel - you will see a significant dip where the tire is not seating properly. I have had tires that gave a loud POP when you were pumping them up as the bead finally seated on the rim.
 

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Nigeyy said:
I bought some Specialized Fat Boys for my touring bike about 6 months ago. Believe it or not I have Specialized brand inner tubes, and Specialized brand wheels (old mtb rims). While on tour, I got a flat, and changed to another inner tube. Of course, at that time, it was raining and I wasn't in a particularly good place to change a tyre, but I got it done as fast as I could. Now here's the mystery:

At the time, once I replaced the tyre and pumped it up, I noticed there was a huge flat spot when I spun the wheel. I mean it was HUGE. About a centimetre lower than the rest of the tyre over a ten centimeter length of the wheel revolution. Hastily, I deflated, re-inflated (kneading the tyre just in case the tyre had not seated properly the first time). Same result, if slightly less of a flat spot. Because I was short on time, I just rode, and eventually tuned out the slight bump-bump-bump motion. Once I did get used to it, I rode it home like that, completing the tour.

Fast forward to a week ago, I wanted to retune my tourer -it's been sitting in my basement since I got back from my last tour last August. I remembered my experience and was determined to fix the flat spot. Here's what I did:

i. at first I thought it was the tyre ("stupid Specialized Fat Boys.... not very good quality.....should never have bought them....." etc, etc) so I thought I would change the orientation of the tyre -usually I always put the tyre label where the valve is for easier finding of the valve. I rotated the tyre around to another label (there are two labels on one side)..... pumped up to 100psi (recommended), and........

ii. the darn flat spot was still in the exact same position!!!! But it was noticeably less. "Oh no" I groaned..... "It's the rim badly out of true". I whipped off the tyre and inner tube and put the wheel on my truing stand. Hmmm the wheel was true both laterally and longitudinally within a millimetre or two. Not the rim!!! Next.....

iii. Could it be the inner tube? It was noticeable the flat spot was always at half past five. I flipped the inner tube around so that if it was the inner tube, the flat spot should now be at half past six..... which it then was -as well a slight flat spot at half past five again. Now both of these flat spots were acceptable. Then I changed the tyre position (so that no label was close to the valve) and I could hardly see any flat spot at all apart from a very acceptable very slight flat spot at half past six and a slight (but acceptable) flat spot that seemed to follow the orientation of the tyre!!

The strange thing is the Specialized inner tubes -when pumped up -do have a very slight lessening in thickness where the flat spot was, but certainly not enough to make you think that at 100psi it would hold back the inflation of the tyre. But it was.

My conclusion? I believe it's a combination of the Specialized inner tubes having deformities (where I believe the tube in joined incidentally) AND the Specialized Fat Boy tyres being slightly tighter at certain spot. My solution is to not use Specialized inner tubes, or align the tyre in such a way that where the tyre might be a bit tighter does not correspond to where the inner tube is joined.

Strange, but true..... anyone else had similar crazy stuff?



I've had this problem too. Here's what I did: Completely dismount the tire from the rim and wash both with soapy water. Remount the tire/rim/tube complex (I use baby powder too but I'm not really sure that does anything). Pump the tire up to max pressure. The tire should reseat onto the rim. If it doesn't examine the rim and make sure you didn't dent/warp it.

-lammy
 

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Discussion Starter · #6 ·
So last night the wife was out working, the kids were sleeping.... I went down to the basement and tried the talcum powder a.k.a. baby powder (rims looked pretty clean as I'd washed them the time before when I was cleaning up the braking surfaces).

And..... the result was the same! I really tried to be *extremely* careful putting the tyres on, making sure the inner tube wasn't snagged, tyre was fully seated, etc. I've never had this problem before -changed inner tubes on wheels and tyres many times before, so it's not like I'm doing this for the first time either. Again, once I changed the orientation of the tyre and inner tube so that where I thought where the inner tube was joined did not correspond to a certain spot on the tyre, no more big flatspot (I should say the tyre still is not perfectly round, but close enough for me not to worry about it).

Really, really weird. Actually now that I think about it, I didn't check the inner sides of the rim carefully, but since this problem seems to not be associated with the rim (i.e. big flatspot appears either at half past five or half past six depending on the orientation of my tyre and inner tube) I kind of discounted that -especially since I can also make the problem go away with careful inner tube/tyre orientation. Strange, very strange -first time I've seen this ever. Maybe I'd better lay off the drink.

Lamourish said:
I've had this problem too. Here's what I did: Completely dismount the tire from the rim and wash both with soapy water. Remount the tire/rim/tube complex (I use baby powder too but I'm not really sure that does anything). Pump the tire up to max pressure. The tire should reseat onto the rim. If it doesn't examine the rim and make sure you didn't dent/warp it.
-lammy
 

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Nigeyy said:
So last night the wife was out working, the kids were sleeping.... I went down to the basement and tried the talcum powder a.k.a. baby powder (rims looked pretty clean as I'd washed them the time before when I was cleaning up the braking surfaces).

And..... the result was the same! I really tried to be *extremely* careful putting the tyres on, making sure the inner tube wasn't snagged, tyre was fully seated, etc. I've never had this problem before -changed inner tubes on wheels and tyres many times before, so it's not like I'm doing this for the first time either. Again, once I changed the orientation of the tyre and inner tube so that where I thought where the inner tube was joined did not correspond to a certain spot on the tyre, no more big flatspot (I should say the tyre still is not perfectly round, but close enough for me not to worry about it).

Really, really weird. Actually now that I think about it, I didn't check the inner sides of the rim carefully, but since this problem seems to not be associated with the rim (i.e. big flatspot appears either at half past five or half past six depending on the orientation of my tyre and inner tube) I kind of discounted that -especially since I can also make the problem go away with careful inner tube/tyre orientation. Strange, very strange -first time I've seen this ever. Maybe I'd better lay off the drink.
Wow, got me. Do you have another set of rims or tyers to switch over? Maybe narrow th e problem to one or the other.
 

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I've been using Specialized Fat Boys since the early '90's. Between my wife and me, we've put at least 50,000 miles on them, touring and commuting. With this experience, I wouldn't use anything else on tours -- they wear well, pump up high, lightweight with little rolling resistance, and we typically go 400-800 miles between flats (on tour -- commuting is something else).

'Course, everybody has their favorite.

But I mention this because I've rarely had a "build quality" issue with them that would cause the problem you asked about. Once in a while I have one where the sidewall gets threadbare prematurely (say, with 1/2 the tread left), but that's all.

Could it be that the tube is folded inside the tire? I've never been able to fit 26" tubes in a Fat Boy, once the tube has been used. My solution: use only 24x1 3/8" tubes. It's a skinny tire with a small circumference, so the smaller tube is appropriate. The 24" tube gets stretched a bit, but -- hey -- it's rubber, that's what it's designed for. If anyone tells you that you're asking for trouble with a "smaller" tube, tell 'em that you trust experience. Believe me, 50,000 miles is proof.

I use cheap tubes from the local sporting goods store. 24x1 3/8" are hard to find now (mostly replaced with "universal 24inch" which are too wide). I've never used Specialized tubes, so I don't know if they have a quality issue; but I'd say if they're 26", they're too big for this tire.

-- Mark
 

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Discussion Starter · #10 ·
Wot? Cor blimey mate, strike a light, on me 'ead son, on my 'ead. It must be what wiv my English upbringing 'n all.... :)

The Walrus said:
The problem you're having is because you're using tYres instead of tIres...
 

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Discussion Starter · #11 ·
Mark:

you could have a point here as I did try a Raleigh brand 26x1 3/8 inner tube, and that considerably lessened the problem (I did, by the way, notice it seemed to be a of a smaller diameter as well -which bears out what you said). I think I will try your suggestion of 24x1 3/8s in the future (as things currently stand, I believe my "issue" is fixed). Judging by the way a tyre inflates, I fully believe a difference in diameter of 2 inches is easily negated as you mentioned. And 50,000 miles bears that out!

Still, the 26" Specialized inner tubes do not appear to kink or fold back on themselves in any way, and even if they did, it's still strange it only occurs in one spot -well, at least once I orient the tyre and inner tube to a certain position. I'm still favouring my theory of a slight tightness in an area of the tyre and a restriction in the inner tube at the same place.

Yes, I've been impressed with the Fatboys so far -my only quibble is that I noticed a cut (not on the sidewall) and it will be interesting to see if I get anymore. I'm always willing to write off one cut to some awful object I went over that would cut any tyre anyway. I cycled fully loaded in some heavy rain down off the top of the Berkshires in Massachusetts (steep, steep hills/mountains!), and much to my surprize, I felt comfortable with the grip these slick tyres offer. Mind you, obviously I wasn't pushing it, but I was always ready to feel for the lack of grip, and it never happened.


EmmCeeBee said:
I've been using Specialized Fat Boys since the early '90's. Between my wife and me, we've put at least 50,000 miles on them, touring and commuting. With this experience, I wouldn't use anything else on tours -- they wear well, pump up high, lightweight with little rolling resistance, and we typically go 400-800 miles between flats (on tour -- commuting is something else).

'Course, everybody has their favorite.

But I mention this because I've rarely had a "build quality" issue with them that would cause the problem you asked about. Once in a while I have one where the sidewall gets threadbare prematurely (say, with 1/2 the tread left), but that's all.

Could it be that the tube is folded inside the tire? I've never been able to fit 26" tubes in a Fat Boy, once the tube has been used. My solution: use only 24x1 3/8" tubes. It's a skinny tire with a small circumference, so the smaller tube is appropriate. The 24" tube gets stretched a bit, but -- hey -- it's rubber, that's what it's designed for. If anyone tells you that you're asking for trouble with a "smaller" tube, tell 'em that you trust experience. Believe me, 50,000 miles is proof.

I use cheap tubes from the local sporting goods store. 24x1 3/8" are hard to find now (mostly replaced with "universal 24inch" which are too wide). I've never used Specialized tubes, so I don't know if they have a quality issue; but I'd say if they're 26", they're too big for this tire.

-- Mark
 
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