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Very little space between tire and fork crown
#1
Hi!

I have an old road bike with very narrow tires. I plan to use this as a commuter bike, so I'd like to swap out to thicker tires, something like the Schwalbe Marathons. The wheel size currently is 700c.

The issue that I have is that the fork crown is very close to the current narrow tire. I've attached a picture. The only option I can think of is that I need to get a slightly smaller wheel and also possibly new brakes with long-reach.

I wondered if anybody has suggestions or other ideas.


[attachment=5282]
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#2
Need more info, including the make/model of bike and whether you know if it's original equipment. It's possible the bike originally had 26 x 1.xx/2.xx (559 ISO) rims. See http://sheldonbrown.com/tire-sizing.html

You might be able to convert to 650B rims/tires, but you would need to do front and rear to avoid altering steering geometry. See http://sheldonbrown.com/650b.html for info on 650B.
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#3
Hi cny-man,

It's a "Centurion Diamondback". I got it off craigslist so I have very little information about it. It looks like it is from the 1980s but that's just my guess. I don't know if the current wheel is original equipment...but if it is from the 1980s, I would have expected original wheel to be steel rim?

What sort of steering problems should I expect if only the front is 650b?
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#4
A Google search shows the bike was built to racing specs - tight clearance both at fork and seat tube. A conversion to 650b is the only chance you have to get clearance, and again I don't recommend changing only the front. You will significantly reduce the "trail" of the front fork and lower the handlebars. Larger tires might reduce the effect but you need more side clearance for a large tire and of course would need to change the brake calipers. http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_geometry. The only other possibility is a different fork, but that's a whole new set of complications.
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#5
Being rather cost conscious, I suggest ISO590 (aka 650a) instead of ISO584 (aka 650b). I am a fan on 590 because of low cost and wide selection of tires available. It is not as fashionable as 584, but for street use there at least as many tire choices.

Ref my 310: http://forums.bicycletutor.com/thread-3598-page-2.html
I need to add some pictures to that thread - it got wider bars last weekend, it will get cabled and taped this weekend.

And these tires: http://www.schwalbetires.com/node/143 which can be found for considerably less at Amazon, Niagara, etc. There are many other ISO590 choices, even

Interestingly, someone in Berkley also updated a Miyata 310 to a sports touring bike, and he also used ISO590 wheels.

The Sun CR18 is a well regarded rim, available in 32H, 36H and 40H drillings in ISO590 size.

You can measure your brake reach now with your ISO622 rims, and determine what you need for other sized rims. I recently coupled a racing 622 (700c) fork with a 559 rim using a Tektro 559 brake on a lugged Trek 950.
Nigel
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#6
Thanks for the useful tip nfmisso! I'm definitely on a tight budget with this bike...The ISO590 does seem a lot less expensive.
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#7
Thanks, Nigel - I'm not that much in touch with some of the more esoteric items, so I was not aware that 650A equipment was available and less expensive.

TO THE OP: Before you jump in it's still important to make sure you will have tire clearance on the sides as well.
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#8
(08-05-2014, 06:53 PM)cny-man Wrote:  .... esoteric ........

????

590 = 650a = 26 x 1 3/8 esoteric - NOT; it has been around for decades, common to almost all "English Racer" style 3 speeds, and many department store 10 speeds. You can purchase 590 tires at almost every Wal-mart - more like the opposite of esoteric Smile
Nigel
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#9
My bad, not paying attention - but you could have just said 26 x 1 3/8!
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#10
I hate to be a kill joy, but around here it would be less expensive to watch Craigslist like a hawk & get a different bike or frame/wheel donor for your project.
Your current bike will fit 622 x 28mm max right? Well to commute you're going to want what size tire? A 37mm or larger, especially on the rear right? I guess a 26 x 1 3/8" will get you that.
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#11
I am on a one person crusade to get people to use a technically logical designation for bicycle rim sizes - ETRTO aka ISO bead seat diameter in millimeters.
http://sheldonbrown.com/tire-sizing.html#iso

Note that sizes called 26 inch range from 559mm to 599mm - which is more than 1½ inches !!!!

Smile
Nigel
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#12
(08-05-2014, 11:29 PM)1FJEF Wrote:  I hate to be a kill joy, but around here it would be less expensive to watch Craigslist like a hawk & get a different bike or frame/wheel donor for your project.
Your current bike will fit 622 x 28mm max right? Well to commute you're going to want what size tire? A 37mm or larger, especially on the rear right? I guess a 26 x 1 3/8" will get you that.

Thanks 1FJEF. I'm keeping an eye on Craigslist, also checking out the local second hand bike parts co-op.
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#13
(08-05-2014, 11:42 PM)nfmisso Wrote:  I am on a one person crusade to get people to use a technically logical designation for bicycle rim sizes - ETRTO aka ISO bead seat diameter in millimeters.

Yes, I'm of course familiar with ISO designations, but I grew up with the old system, so sometimes it's helpful to just mention the traditional size as well.
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