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27" wheels on a 26" MTB frame?

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27" wheels on a 26" MTB frame?

Old 02-09-14, 02:15 PM
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Chitown_Mike
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27" wheels on a 26" MTB frame?

So I have been pondering about my early 90's drop bar MTB. I have all my parts left over from my now smooshed Conti, including the aluminum 27" rims. I really liked some of the gravel grinders that are shown on here, but I don't have the budget for a road frame, or another MTB frame, to do that out of. What I was thinking was swapping the 27" rims onto the MTB, or really just having another set of rims to throw on for less rugged traveling (commuting, road riding, etc.). This is my work-horse bike and something that gets used often, abused, and put away wet. So "looks" aren't exactly all important (the current front fender is a protein mix bottle).

Here I what I have gathered from reading up:
- No one seems to have done it with 27" rims, lots of 700 but no 27" specifically
- The brakes will be an issue
- Some tires maybe an issue hitting
- The fork needs to have a hole in it for non-canti brakes
- Nothing is at it seems

Here is what I have:
- Good MTB setup w/ drop bar and STIs, 26" Continental Double Fighter IIs
- Dia Compe Blaze road calipers w/ good pads (got these and a bunch of other parts for $20 the other day, really nice condition)
- Patience to learn and ability to do the fiddling myself
- Good 27" rims (one needs a tire....oh well)
- Lots of love and guidance from folks on BF


My question is has anyone attempted it or done it and perhaps never posted? I did do a search with a couple of different phrasings and couldn't find anything. I appreciate any input anyone might have.....otherwise I might undertake this in a week or so.
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Old 02-09-14, 02:26 PM
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the brake calipers might not reach. i did a conversion with 700x28 and some generic regular road calipers. the calipers were 5-6mm short. if you have medium to long reach calipers then not problem, tektro r559 have more then enough reach and width for any 27" set up. it was easy to drill the fork. center punch, 1/8" drill bit, then 1/4" for the front and 5/16" with a little filing for the rear unless you have a non recessed nut caliper (disclaimer: dont just use my drill size, yours may be a different size and i hold no responsibility for any miscalculations). same for the rear bridge. i think the conversion would work for any non suspension mtb frame/fork, plus it will also have room for full fenders!
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Old 02-09-14, 07:15 PM
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Originally Posted by Antieverything View Post
the brake calipers might not reach. i did a conversion with 700x28 and some generic regular road calipers. the calipers were 5-6mm short. if you have medium to long reach calipers then not problem, tektro r559 have more then enough reach and width for any 27" set up. it was easy to drill the fork. center punch, 1/8" drill bit, then 1/4" for the front and 5/16" with a little filing for the rear unless you have a non recessed nut caliper (disclaimer: dont just use my drill size, yours may be a different size and i hold no responsibility for any miscalculations). same for the rear bridge. i think the conversion would work for any non suspension mtb frame/fork, plus it will also have room for full fenders!

Those Tektros are what I was thinking, I came across them when looking up other calipers. This will more than likely be a spring thing since I want to keep the bigger tires on the bike while there is still snow on the ground.
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Old 02-10-14, 01:09 AM
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I've seen it done with 700c rims. Someone took a very nice Stumpjumper and made a very bad road bike out of it. The brakes almost fit, he used cheap stem shifters that almost worked, and he almost didn't hit his shoe on tight turns.

Thought about doing the same conversion with 650b rims on a disc brake equipped bike. Wasn't cost effective. Would have been better off just buying a hybrid.
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Old 02-10-14, 01:37 AM
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Rear dropout spacing will probably be off 5-10mm.
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Old 02-10-14, 08:07 AM
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Originally Posted by BluesDaddy View Post
Rear dropout spacing will probably be off 5-10mm.
Hmmm...I didn't think of that. I guess I'll have to measure first to see if I can even do that.
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Old 02-10-14, 08:14 AM
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You don't say what the frame is that you are working with. Is it steel? If so, just respace or spring the rear and you are good to go. I'd like to see this project go forward. It sounds interesting.
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Old 02-10-14, 08:32 AM
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Originally Posted by busdriver1959 View Post
You don't say what the frame is that you are working with. Is it steel? If so, just respace or spring the rear and you are good to go. I'd like to see this project go forward. It sounds interesting.

Yeah it is a cro-mo Trek 800. I already have a 7 speed freewheel crammed back there and everything has lined up so far. I did have to put a thick washer to shim the wheel to the left because the smaller cog would rub the frame when the chain was in it. I am waiting on some other parts and tools to come in before I attempt this. I need a freewheel remover tool first, been lazy about getting one but now I don't have an excuse!
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Old 02-10-14, 08:48 AM
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I use a 9/16 bolt to remove freewheels.
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Old 02-10-14, 09:40 AM
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Originally Posted by BruceHankins View Post
I use a 9/16 bolt to remove freewheels.
Shimano? Do you jam the bolt head in the splines?
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Old 02-10-14, 10:27 AM
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Okay, I have indeed done the 26" mtb to 27" wheel conversion. If you have the tire clearance and the drilled out points in the fork and rear; short reach brakes should have no issue reaching them. Now we need to talk shifters and levers, going drop bar changes the game obviously so you'll need road levers (sounds like you have those), and then to decide on shifters, we'll assume you don't have DT mounts, thumb shifters on that flats of drop bars are okayish, brifters IMO are the best choice (they currently make a070's btw 2x7).

So now reviewing your list, you appear to be set actually. Your only possible issue being clearance, now bear in mind my 700x28's were smaller than my 27x1 tire so you'll want lots of room in the rear and fork or it's just not going to work.

Other issues I've noticed, steering may drastically change necessitating a much longer stem, or possibly switching to a road geometry fork, your BB will be much higher up, so make sure you frame size is rather small for yourself since you will be raising it overall. If I think of anything else I'll get back to you.

Here's a mid 80's rigid 26" mtb converted to a 27" fixed gear (brakes and such were added after this pic)

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Old 02-10-14, 05:19 PM
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Well it's a 12 point tool and a 9/16 (I think, not quite a 21mm but a worn out lug but works too) bolt fits in with a little love tap. A used bolt with some rounder edges works better. Tap it in lightly, put a wrench on my lock bolt and spin it loose.
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Old 02-10-14, 05:38 PM
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I put 700c on a 26" bike. Laced a Mavic MA to an LX hub, using same spokes as when laced to 105 hub.

Looks like I'd need to file the slot or get shorter reach brake in back to handle 27" but the long reach RX100 front brake would handle 27" no problemo.

No toe overlap at all for me.






20131016_151703[1] by Lester Luallin, on Flickr
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Old 02-10-14, 06:34 PM
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Originally Posted by LesterOfPuppets View Post
I put 700c on a 26" bike. Laced a Mavic MA to an LX hub, using same spokes as when laced to 105 hub.

Looks like I'd need to file the slot or get shorter reach brake in back to handle 27" but the long reach RX100 front brake would handle 27" no problemo.

No toe overlap at all for me.






20131016_151703[1] by Lester Luallin, on Flickr
Glad you chimed in.. you started my SS/wheel size conversion insanity with all yours.
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Old 02-17-14, 08:21 AM
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Originally Posted by BruceHankins View Post
Well it's a 12 point tool and a 9/16 (I think, not quite a 21mm but a worn out lug but works too) bolt fits in with a little love tap. A used bolt with some rounder edges works better. Tap it in lightly, put a wrench on my lock bolt and spin it loose.
Bruce, do you have a picture of what you are using and how it fits?



And to those that chimed in, thanks! Giving me hope that this could be possible.
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Old 02-17-14, 12:53 PM
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It's a 9/16x3-1/2 (I think) bolt with a nut on bottom to take it loose and lock nut on top. You can use just a bolt and vise grips, but I like being able to put a wrench on there. Just give it a little love tap with a hammer an it fits snugly in there. Note an old worn bolt works best, if you use a new one, grind the edges slightly to allow an easier fit.
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