Changing from Nobbies to slick on mountain bike

you've just discovered something stupid about bike tires: 26xnumbers with a fraction (like 1 3/8) is a different diameter than 26xdecimal (i.e., 1.95). Believe it or not 26x1.5 is different and will not fit on the same rim or possibly frame as 26x1 1/2.

If you ever meet anyone who is responsible for this, please post it on here - it's one of my missions in life to slap them.


anyway, you need to get some decimal-sized tires.

So I take it that 26 inches is the outside diameter then.  I agree, that's just stupid.  I would have thought that 26 is the rim size.

I wanted to change from 23's to 32's on the road bike that I use for training and riding paths around town.  I was having a pinch flat problem and wanted a bigger tire.  Did all the research, measured to make sure they'd fit and checked the internet for pricing. I went to the bike store and paid an extra 5 bucks a tire but was having them installed... fair trade...  Glad I did!!!  tires rubbed had to go down to 28's.  They made the switch no harm done and I was on my way.  28's were 3 bucks less.

Long story short...  For 4 bucks over internet pricing I got the tires I needed, installed and made sure they fit before I paid a thing.  I can only imagine the stuff that would of got broke in my garage had I ordered on the net, waited,  went throught the processes of installing only to find out it was wrong and doing it all over again.

For cheap fixes and sizing issues go to the bike store.  They can give you your options. 

I changed mine a few weeks ago, and made sure I took my front tire with me when I went to the LBS.   He barely looked at it, and I ended up with 26 x 1.5 and they work great.  My nobbies were 26 x 2.0.  I was able to mount them myself (with the new tubes I got too), and they went on great.  It made a huge difference.  The PSI on the ones I got were 100 and WOW!   Much smoother ride.

I would say take them back and get the decimal ones, and take your front tire with you when you go!  Good luck!

oh, it's worse than that. 26" is nothing. There is no dimension on a 26" rim, wheel or tire that's 26 inches. It refers to the nominal outside dimension of the tire, but that's so obsolete no one even remembers what the width of that tire was.

There is another measurement: ISO, which makes a lot more sense, so of course we don't commonly use it. ISO for a common MTB rim is 559mm (the actual diameter of the bead seat). Thing is, your shop knows this; if you went in and said you have a mountain bike, and you want to put slicks on it, they should have known that 26x1 3/8 tires would not fit (fractional size isn't all that common anymore, and every mountain bike I've ever seen has 559 ISO rims, except some new wheel trends, the sort of thing you'd know if you had). If it were me, I'd be looking for a new shop; what if this was one of those situations where it sort of fit, but might give out dangerously at the wrong time?

here is enough info to make your head spin:http://sheldonbrown.com/tire-sizing.html
as with everything Sheldon Brown wrote, be aware that although there is a ton of information, he often forgets that bikes did not stop changing/advancing in 1971, so he is prone to talking about things that haven't been made in decades as if they are common.

I don't go to and LBS.  Probably my first error. I just went to a local department store that sold bikes and asked the shelf stocker boy there.  (my second mistake).  I think I will bring my front rim with me to return the tires I have and mount the new tube and tire right in the store.  If they don't have what I need, I'll head to an LBS and go from there.

Thanks

you can get as low as 26 x 1, but there are some 26 x 1.25 and plenty of 26 x 1.5 tires that areas good as slick with a minimal tread on the outside edge incase of cornering on hardpacked trails etc.

I use a tube that is supposed to be for 1.25 - 1.75 in all my mtb tires even the 1.95's I have on.
Your current tubes will work.

I'd take back the junk you got from the big box store.
There is a lot to be said for supporting your LBS but for just a tire, buy from performance, jenson, pricepoint etc.  Even E-bay has a good selection.


Edited by alex jb 2009-09-13 8:57 PM