non-standard rim size? really?

I have a really hard time fixing flats on one of my bikes, a Miyata 1000, because it's difficult to get the tires off and impossible to get them back on. I have three other bikes and don't have trouble removing or replacing the tires on those. And yes, the bead is pretty tight, but the tires are probably near two years old--it seems as though they should have worn out a bit by now. I've come to just accept paying a bike shop to fix flats on that bike (bike shop mechanics can fix them, although I have gotten comments about how tough it is to get the tires back on). But I'm planning some long rides out of the city in the next couple weeks, and I'm not sure what I would do if I ended up needed to fix a flat on the road.

To get to the catchy subject head: A couple years ago, I was told by a mechanic at one shop in the suburbs that sometimes, wheels will be made just slightly too large or small--not enough so that it would be noticeable to the eye, or that it wouldn't fit properly onto the bike. Just enough that getting tires on and off could be a huge pain in the ass, or that the tires would be a little loose and cause a bunch of pinch flats. I have chosen to believe this, because it makes me feel better about my inability to fix flats on this bike.

But, I wonder, could this really be the case? Has anyone heard of this phenomenon?

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Permalink Reply by Ali on September 1, 2009 at 10:37am
Heather,

I have heard and experienced this phenomenon, but not exactly the way you are describing it...I have had number of bikes over the years and when I purchased my last one which came with awesome Campy wheels but crappy tires, first thing I did was to take the tires off my old bike and put it on the new one. Then I noticed that Conti GP4000S' that fit my old wheel just fine was fitting quite tight on my Campy wheels. In fact pretty much any tire I buy fits quite tight on those wheels. But I am more than happy to have a tight wheel to tire interface as I feel safer when I am carving a corner.

Also not all tires were made the same either, certain tires are better for putting on tighter rims, in my experience the folding clinchers go on easier than the wire bead ones. A well as some manufacturers seem to have fit tighter. From the brands/types of tires I tried here is a list from tightest to loosest.

1)Vittoria Rubino
2)Conti Gatorskin
3)Conti GP4000S
4)Michelin Lithion
5)Vittoria Rubino Pro
6)Specialized Armadillo
7)Michelin Pro Race
8)Michelin Krylon
9)Specialized Mondo Sport

-Ali
Permalink Reply by Homebuilt on September 1, 2009 at 10:39am
Doubtful. Especially since bike manufacturers just purchase wheels, they don't make them. For a discussion of wheel sizes see: http://www.sheldonbrown.com/tire-sizing.html
My road bike and tire combo is excruciatingly tight, it's a real PITA. Different tires may help, and your LBS may be able to point you in the right direction to tires that generally are looser. I got some serious tire levers and worked a lot on my technique, and can now do it myself, but with a lot of pain. You might also ask your LBS for some tips.
Permalink Reply by Barry Niel Stuart on September 1, 2009 at 10:40am
If I'm not mistaken, this bike should accept 7ooc x32 or 35 tires. I do recall that there may be slight variations in rim size among rim makers. Which company made your rims? It would not usually be the same as your bike. Often, the rim manufacturer stamps its name close to the valve hole. Also, some tires fit tighter than others on the rims. Are your rims original to your bike?
Permalink Reply by Homebuilt on September 1, 2009 at 10:46am
I would add Vredestein to the "very tight" end of your list.

Ali said:

1)Vittoria Rubino
2)Conti Gatorskin
3)Conti GP4000S
4)Michelin Lithion
5)Vittoria Rubino Pro
6)Specialized Armadillo
7)Michelin Pro Race
8)Michelin Krylon
9)Specialized Mondo Sport

-Ali
Permalink Reply by David P. on September 1, 2009 at 3:33pm
Yes, this does happen sometimes. Occasionally quality control lets manufacturing variances get a bit high for a batch. You can eliminate the tire as the cause of the PITA by mounting them on another set of 700c wheels - if it's much easier there, you know it's the rim. If it isn't, it's the tire.

david
Permalink Reply by Mike Schwab on September 1, 2009 at 5:59pm
http://www.parktool.com/products/detail.asp?cat=4&item=TL-5 for a little more leverage. Also be sure to get the bead in the center for maximum gap on the other side.

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