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I have a Takara Kabuto. It has 700x32 tires (I don't really know what that means).

I was looking at upgrading the brake calipers. I was looking at these, among others.

How do I tell if they will fit my bike? On the page for the SRAM calipers linked above, it says that they fit 28c tires, but in the questions sections, a person said they'll fit on 32c tires. How do I know if that's correct?

I can't find any size information whatsoever for the Tektros.

How do I make sure that any pair of brake calipers I purchase over the internet will be the right width, length, etc.?

  • Have you tried emailing the manufacturer? – mattnz Mar 9 '15 at 2:15
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    Whether they fit or not depends on the bike. The real question here is: "Does this bike require long-reach calipers?" You should be able to inspect your existing calipers (or post the exact model here) to find out. – John Zwinck Mar 9 '15 at 3:28
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Road brake calipers are built with "reach" dimensions. The reach is the distance from the center mounting bolt to the pads. Usually this is a range of values (e.g., 47mm-57mm) as you can adjust the pad vertically within the caliper. It is important you replace the caliper with another caliper of the same reach. If you do not get the appropriate reach you will not be able to position the brake pads to engage the rim braking surface.

Generally, there are 3 common sizes for road brake calipers.

  1. 39-49 mm - "short" reach - Common on race road bikes, lower volume tires (e.g., 700x23c). The Tektro R540 (what you linked) has this reach.
  2. 47-57 mm - "long" reach - more common on road bikes that slightly larger volume tires (e.g., 700x32c).
  3. 57-76 mm - "Extra long reach" - less common and found on more boutique frames which are designed to fit even larger volume tires or 700c to 650B conversions.

You need to determine which reach your current calipers are. Given the tire size of your current bike (700x32c), if I were to guess, it is likely option (2) 47-57mm.

If you peruse Sheldon Brown's web page on brake calipers you can see which brands and model numbers will match this reach specification. I would however suggest measuring your caliper reach to confirm my guestimate before any purchases.

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To start with, an aside. 700x32 describes the physical size of the tyre. 700 is 700mm, which is the diameter of the tyre. That size is very common. 32 is 32mm, and describes the width of the tyre. The wider the tyre, the more rubber in contact with the ground while riding (sometimes you want to have lots of contact, sometimes you don't). Note that due to evolution, tyre sizes are not necessarily expressed in millimetres. For some genres of bicycle (notably mountain bikes), these numbers are expressed in inches, just by convention, a quirk of history.

To address your actual question, you say your current tyre is 32mm wide, whereas these calipers are specced for tyres up to 28mm wide. So, just going be what the manufacturer says, the caliper will not fit.

Now, you say you have heard someone say that, actually, they will be ok. (And to be honest, this is not at all uncommon in the world of cycling.)

So essentially you have to take a punt - do you trust this person, buy the brakes, and run the risk that they don't fit? Or, do you buy some brakes which are specced to your current tyre?

The choice is yours...

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    Another consideration, unlike rim diameter there is no universal convention dealing with tire width. One brand of tire 32mm wide may fit and another brand may not. – mikes Mar 9 '15 at 11:06
  • absolutely @mikes, I fully agree. Also, a great reference is Sheldon - even if you ignore every piece of information on that page, you just need to look at the size of those tables to realise just how many "standards" there are – PeteH Mar 9 '15 at 11:24
  • Actually, for completeness, it's probably worth saying that brake calipers typically carry some kind of stamp to indicate the maximum tyre size they support. But again, I'm not sure how "standard" this is – PeteH Mar 9 '15 at 12:02
  • I don't think it will fit as the Tektro R540 (suggested replacement) is a short reach caliper and I suspect the bike has long reach calipers given the tire size. – Rider_X Mar 9 '15 at 16:38
  • Additional point: 700 is not any physical dimension but a designation for 622 mm rim. Sheldon's site explains the reasoning behind it. – ojs Jul 3 '15 at 20:35

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