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  1. #1
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    700c conversion to 26 wheels

    can i convert a 700c bike to mtb wheels? anything i missed before I get the wheels?

    the front n back caliper have been changed to larger
    tires would be the smaller type and fits.
    what about the back wheel portion?


    is the width of the 6 speed equal to 7 or 8?

  2. #2
    Senior Member LesterOfPuppets's Avatar
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    What frame are you using? Pics?
    You're using caliper brakes? What calipers are you using? You'd need a massive drop bolt and some long arm calipers to reach a 26"
    Why are you doing this?

    Quote Originally Posted by zzzzz View Post
    is the width of the 6 speed equal to 7 or 8?
    Sometimes. Answer my first question about the frame. Make/model/year, and I'll have some more for you here.

    Many 6sp MTB wheels are set up for a 130 dropout width, which is pretty common for 8 speed road frames, for instance.
    Last edited by LesterOfPuppets; 01-01-11 at 01:01 PM.
    1980ish Free Spirit Sunbird fixed * 1996 Mongoose IBOC Zero-G * 1997 KHS Comp * 1990-ish Scapin * Olde Western Auto Cruiser.

  3. #3
    coprolite fietsbob's Avatar
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    650b is closer to 700c 622 - 584/2 = 19mm radius drop. those are popular conversions lately.

    put 559, 26" in that calculation and the drop is 31.5mm

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    Since you've measured brake reach and believe that's OK, you've cleared the biggest mechanical hurdle. There are some issues of rear axle width, but you can simply measure yours and read the specs for what you're buying. Worst comes to worst, you can spread the rear triangle of your metal frame to fit the new axle.

    The one thing you should keep in mind is that you'll be lowering the bottom bracket and losing some pedal to ground clearance. It's a difference of almost 1" from the rim but will be less than that depending on the comparative width of the tires used.

    The only thing I can suggest, is that you ask yourself what you hope to gain by the switch, and decide that it makes sense for your needs before spending dough on a pair of wheels and brakes.
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    M_S
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    I'll make it simpler: Without disc brakes or welding on cantilever studs in the right place, no you cannot. 650b might work, and would screw up the geometry way less.

  6. #6
    tcs
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    Quote Originally Posted by zzzzz View Post
    can i convert a 700c bike to mtb wheels?
    The Cannondale Bad Boy models are designed to use either 700C road or 26" mtb size wheels.
    "When man first set woman on two wheels with a pair of pedals, did he know, I wonder, that he had rent the veil of the harem in twain? A woman on a bicycle has all the world before her where to choose; she can go where she will, no man hindering." The Typewriter Girl, 1899.

    "Every so often a bird gets up and flies some place it's drawn to. I don't suppose it could tell you why, but it does it anyway." Ian Hibell, 1934-2008

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    Quote Originally Posted by tcs View Post
    The Cannondale Bad Boy models are designed to use either 700C road or 26" mtb size wheels.
    They should have called it the "Hamlet", as is for folks who can't make up their minds.
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  8. #8
    Senior Member LesterOfPuppets's Avatar
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    You can run 26" on pretty much any disc equipped 29er if you really wanted to.
    1980ish Free Spirit Sunbird fixed * 1996 Mongoose IBOC Zero-G * 1997 KHS Comp * 1990-ish Scapin * Olde Western Auto Cruiser.

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    Senior Member shouldberiding's Avatar
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    Quote Originally Posted by LesterOfPuppets View Post
    Why are you doing this?
    I'd be interested to know as well.

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    Constant tinkerer FastJake's Avatar
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    Quote Originally Posted by shouldberiding View Post
    I'd be interested to know as well.
    Me too. One possibility is that you could fit a reasonably wide MTB tire in a frame that was originally designed for narrower "road" tires. But then again... why not just get a mountain bike?

    Without picture or specifics, I find it hard to believe you've found caliper brakes that will work.
    Why "derailer" is the correct way to spell the gear-change mechanism: sheldonbrown.com/derailer.html

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    Senior Member LesterOfPuppets's Avatar
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    I have a feeling he's just sourced some calipers that can accommodate some 2" tires, not that can actually reach a 26" rim from a 700c frame's brake bridge.
    1980ish Free Spirit Sunbird fixed * 1996 Mongoose IBOC Zero-G * 1997 KHS Comp * 1990-ish Scapin * Olde Western Auto Cruiser.

  12. #12
    cs1
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    Surly uses 26" wheels on all the LHT's under 56CM. They said the wheels are more durable and easier to find.
    1999 Waterford RSE-11, 1995 Waterford 1200, 1989 Specialized Rockhopper Comp
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  13. #13
    Real Men Ride Ordinaries fuzz2050's Avatar
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    Quote Originally Posted by cs1 View Post
    Surly uses 26" wheels on all the LHT's under 56CM. They said the wheels are more durable and easier to find.
    But that's neither here nor there, Surly designed the LHT's (all sizes are available now, not just the short ones) around the 26 inch wheels. That's an entirely different thing than simply sticking 26 inch wheels in a frame designed for 700c. While there are some benefits to 26 inch wheels, they are far outweighed by the trouble caused by converting a frame to a size it wasn't intended for.

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    I've seen 27" to 700c conversions and 26" (559mm) to 700c conversions, but I haven't seen a (non-disc) 700c to 26"(559mm) conversion, and am not sure it's feasible without modifying the frame (install canti studs or disc mounts).

    Looking at the wheel diameters I do have an off the wall question of my own; if you have a bike made for 26" wheels with u-brakes and convert to cantis or Vs could you use 28"(635mm) wheels?
    The size difference would be 38mm, with u-brakes reaching down 20mm and cantis extending up 20mm.
    I know it's not a common wheel size, but does anyone have them? How much clearance would the frame need to have (with the skinniest available tires)?
    Last edited by NightShift; 01-02-11 at 11:56 AM. Reason: Typo
    Quote Originally Posted by sprockets View Post
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    A quick search shows tires available from Schwalbe and Kenda in the 635mm size, but only 28"x1 1/2". There may be some 26" wheel frames that could fit a 28" rim, but probably not with a 1 1/2" tire.

    Don't suppose anyone makes a 635x25?
    Quote Originally Posted by sprockets View Post
    I talk to myself regularly - crazy is the technical term I believe. The only time I shut up is when I'm riding. (that's the best time to listen to all those voices in your head :D )

  16. #16
    Senior Member DVC45's Avatar
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    Also consider the drop in BB height as a result of this conversion. If you're okay with that, then go ahead and keep us posted.

    Thanks!
    "Cycling is for pleasure not penance"

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    coprolite fietsbob's Avatar
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    The Cannondale Bad Boy models are designed to use either 700C road or 26" mtb size wheels
    skinny 700c and fat 26" are close in OD of wheel. but rims are Not, disc brakes let you get away with that ..

    But I'll guess you cannot put Fat 29er MTB tires on those 700c rims and get them to fit in that bike..

  18. #18
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    Hi

    I am doing this because i recently bought a run down bike which I had wanted to make it my commutering bike. On closer inspection, it got dry rotted tires and a bad rim too. The rim was a 23 and it wont be practical to have a pillion on it. The most the rim can take is a 28c which is still too small.

    I decided to run 26" on it because I was always curious on whether that can be done. This for the advice! you guys are a very knowledgable lot.

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    Also,I got calipers, it barely fits. I could make the pads work by taking a couple of mm at the top so that it doesn't contact the side wall and the hub width didn't fit. The front seems to work. It would probably fit a 26 x 1 3/8 rim.

    I bought a rear wheel and went to put 26 x 1.5. not sure if it would fit a 1.75. and used a center brake instead. Something like a band brake but works more like a car's drum brake. The stopping power I reckon would be very good.

    The BB has been lowered. but will not know the extend until i mount the front wheels. thanks for the advice.


    I will be getting a a front rim soon. I hope that i would work and it can be my commuter bike where I can park outside. I have other 2 bikes but I rarely ride them because here in Shanghai, bike do get missing.

    Benefits to me is that smaller is more stable due to lower center of gravity( i hope) and stronger 26 vs 700c rim, its easier to get spare parts too. 26" tires tend to be thicker and lower psi and I have a lot of 26" bikes back home.


    The next one I would buy would be a rod braked roadster with steel rims. Would like to find out if the 26 inches 1 3/8 steel variety would fit a 26 MTB rim with a longer 28 inches brake and if not, would the braking power be sufficient with aluminium rims.

    Also, maybe coaster brakes or 3 speed hubs. I like to maintain rods as much as possible.

  20. #20
    Senior Member DannoXYZ's Avatar
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    Check out this Sheldon Brown - Tire Sizing website. You want to get familiar with the ISO/ETRTO tyre-sizing system. The critical dimension is the bead-seat diameter (rim overall-diameter will be slightly larger). Measure this on your existing bike, then make marks on the frame of where the new size would end up. Then you can test whether your brakes can work beforehand.

  21. #21
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    I think the project is a solution looking for a problem. But that is just my opinion. I sincerely wish you the best and I hope you and your new 'Frankenbike' have many thousands of safe and happy miles together.

    Some advice:
    First, on caliper brakes, the higher up the pads are mounted in the caliper the more braking power you will have - moving the pads closer to the brake pivot changes the leverage ratio in the caliper.

    Having a bike set up so it can only use filed-down brake pads is asking for trouble. In my opinion this is acceptable as a temporary measure only as it can result in the brake pad rubbing and damaging the tire if you are not careful, and it complicates maintenance.



    If the brakes do not quite reach, consider making or buying drop bolts as described by Sheldon Brown.

    Using a drop bolt to lower the mounting bolt allows you to have the pads higher up on the caliper so they make the correct contact with the rim, and so they are closer to the pivot and give you more power.

    Generally speaking, there are three ways to correct this:
    1. Have the frame modified
    2. Use a drop bolt
    3. Find another model or style of brake that has a longer reach

  22. #22
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    hi I managed to get the back wheel done and its running something like a band brake but works more like a car's drum brake. The front I will try the caliper and it should fit. If it doesn't, I would probably get a 700 c fork for disk mounts or a MTB fork with disc and V mounts. What would lowering the front fork affect bearing in mind that the rear has already been lowered to a 26 1.5 mtb rim with a drum brake? thanks for all the advice. 'Frankenbike' it is

  23. #23
    Senior Member LesterOfPuppets's Avatar
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    Drum brakes are ideal for running wrong size wheels. If they're ever available where you are, get them.
    1980ish Free Spirit Sunbird fixed * 1996 Mongoose IBOC Zero-G * 1997 KHS Comp * 1990-ish Scapin * Olde Western Auto Cruiser.

  24. #24
    Constant tinkerer FastJake's Avatar
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    Quote Originally Posted by zzzzz View Post
    I bought a rear wheel and went to put 26 x 1.5. not sure if it would fit a 1.75
    Quote Originally Posted by zzzzz View Post
    The rim was a 23 and it wont be practical to have a pillion on it. The most the rim can take is a 28c which is still too small.
    Some advice on tires: I've never run into a problem putting a wider tire on a narrower rim. You shouldn't go crazy, but I think you can put a 32-35c tire on pretty much any 700c rim. Just because it has a 23 now doesn't mean you can't go much wider than that. You only have to make sure they fit in your frame, and underneath your caliper brakes (if applicable.)

    Quote Originally Posted by zzzzz View Post
    What would lowering the front fork affect bearing in mind that the rear has already been lowered to a 26 1.5 mtb rim
    If you want to keep the bike at its original height, consider getting a wider rear tire for your 26" MTB rim. I have MTB tires 1.95" wide that are the same diameter as a 700x23c or 25c. Just something to think about.


    One other thing: pictures would help a lot. You're throwing around a lot of tire sizes and options, and sometimes I don't know exactly what you're trying to do. Plus I'm curious to see your Frankenbike
    Last edited by FastJake; 01-04-11 at 09:27 PM.
    Why "derailer" is the correct way to spell the gear-change mechanism: sheldonbrown.com/derailer.html

  25. #25
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    yes, i had considered welding a 5mm steel onto the rear frame so that I can mount the rear caliper if all else fails, good thing i din not have to do it that way. Will take a picture of the bike when completed. drum brakes are great and a cheaper alternative to disc. will have to try if the front wheel 26" works.

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