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700c to 26" conversion

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700c to 26" conversion

Old 10-14-13, 09:45 PM
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700c to 26" conversion (The Verdict is In!!!)

I am contemplating getting a 700c bike converted to 26" wheels. I have various reasons for doing this and have thought thru all of the pros and cons I can come up with and I just want to run it by you guys to see if I'm missing something.

First, the basis for the build is a 1995 Trek 730 Multitrack. I recently picked up a 1995 Trek 820 as a project/donor bike. Tonight, I took the 26" wheels with 2.15" tires and put them on the Multitrack and they fit fine with no clearance problems.

Second, this build will be a neighborhood bike. Something I take out and ride along the sidewalks in the greenbelt of our subdivision and over the dirt where construction is going on. I rode the Trek in it's original 700c configuration with only a front brake with no issues, so I'm comfortable with that.

Third, I was looking into having the canti mounts moved on my Multitrack fork when it occurred to me that the 820 fork already has them in the right location! I had assumed that there was a considerable size difference in the overall length but on a whim I measured and both are 400mm! Not only that, but my Multitrack is a 21" bike with a 100mm headtube. The 820 is a 22.5" bike with a 185mm headtube. Both are 1" threaded steerer tubes.

How feasible is it for a bike shop to chop the steerer tube of the 820 fork to the same length as the Multitrack fork and thread it so that it works in the Multitrack frame? Can most bike shops do this or is it a pretty specialized operation?

The final bike would be the frame and drivetrain from the Multitrack, the fork and wheels from the 820 and all other bits from the parts bin. There would be no permanent modifications to my beloved 730 and the 820 was bought as a donor bike so no worries about cutting the steerer tube.

The 820 fork has 3mm more rake so the final Frankenbike would have 66mm of trail compared to the 74 it had with 700c wheels. I see this as an improvement.

I have my Multitrack drafted in BikeCAD and with 26" wheels/50mm tires the BB height is 5mm lower than my road bike with 32mm tires. My biggest concern was too low a bottom bracket but that seems to not be an issue since I plan to run as fat a tire as possible.

Have I missed anything here?

Here is the Multitrack frame with the 26" wheels on it:




And a BikeCAD rendering of the final bike:




The Verdict


I finally got both of my 55mm Big Apple tires. First and foremost, this was a test of those tires for a possible, nice build of a fat-tire bike. They passed with flying colors and really don't have any more rolling resistance than my 700c x 40 Duremes, which are on my main bike.

The first bike I put them on was the newly cold-set 80's Takara MTB frame (a knockoff of a mid-80's Stumpjumper). I was thrilled with the ride and began making plans for this bike.

The next day I swapped the wheels/tires over to my 700c Trek 730. Within the first 20 yards, all thoughts of the Takara vanished from my mind. I knew instantly that I prefer the more sporty handling of my 730 over the very stable handling of the Takara.

About a week later I finally got around to trying the wheels/tires on the 1995 Trek 820 MTB. I waited so long because this one is at my absolute limits for stand-over clearance, in that I really don't have any. I would be totally comfortable on pavement but not so much so on dirt. This bike was a surprisingly nice compromise between the stability of the Takara and the agility of the 730, while falling closer to the agility side.

So, the verdict is........the 820! Even though it's really too big, it was more pleasant to ride and once I get it dialed in I think it might be more comfortable than my good, 700c bike.
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Last edited by corwin1968; 12-22-13 at 08:27 AM.
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Old 10-14-13, 10:39 PM
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What do you hope to gain b y going to 26" wheels over 700c wheels with similar tread tires?

Honestly, seems like a big waste of money. The 720 is just a typical flat bar hybrid, basically an 820 with canti posts up higher to accommodate 700c rims.

I would just source a 820 frame/fork and call it good. It would not be worth it at all to modify and move the canti posts on the 720 frame.

But again, I ask you, what do you hope to gain?

Seems like a huge waste of time and money when older nineties era mountain bikes are all over craigslist. You will spend hundreds of dollars geting the posts cut off and rewelded and the bike repainted and in the end, you will end up with nothing better than a typical 820 mountain bike.

Since you have the donor 820, just move the entire drivetrain of the 720 over to the 820 if you so desire. Then you will get your 26" wheels.

In the end, you will have spent a huge amount of money to make a bastarded 720 that can't use the desirable 700c tires and will be worth less than a stock nice 720 multitrack which in itself is only worth about 100 bux.
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Old 10-14-13, 11:05 PM
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To answer your question: you could easily shorten the 820 fork and have a machine shop thread it for use on your multitrack, but it would likely be cheaper and easier to buy a 26" fork that already has the appropriate length steerer for your 730 Trek.

I'm not going to try to talk you out of this; the fact that you
have various reasons for doing this and have thought thru all of the pros and cons I can come up with and I just want to run it by you guys to see if I'm missing something
, plus that you're claiming that you are only half-heartedly riding the bike over short distances, where a rear brake is not needed, would indicate that you already know that this is a terrible idea. You wanted to know if you missed anything; consider the fact that, in dropping the height of the bike, you'll drop the BB and risk pedal strike... You'll also likely alter the geo and steering characteristics of the bike, but that should hardly be of concern to someone who doesn't need a rear brake on a freewheelin' bike....

You've also possibly missed some of the economical realities of the equation;i suspect that you are trying to save money, and you're trying to make a bike that's slightly too big for you (730) smaller via the smaller wheels of a donor bike, which you already own. I suspect you could find a bike of similar quality that fits you with less effort and for less money, with better results if you actually get the right size this time.

Well, I guess I did try to talk you out of it, but I really was hoping to aoid that.
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Old 10-14-13, 11:28 PM
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That's a stupid idea. Buy a mountain bike that fits on your local craigslist for less than $100. Likely with better parts to boot. There is NOTHING special about the 730, the 820, or any of the parts that are in any way associated with either of those two bikes.

You have bikeCAD access, how are you even asking this question? You know better than this.
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Old 10-15-13, 03:46 AM
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When you go from 700C to 650B ground clearance becomes an issue. Going to 26" would really be a problem. Unless you're thinking of using some kind of fat bike tire. Which might explain the whole thing. Good luck on the project.
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Old 10-15-13, 06:37 AM
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Actually, I'm not trying to save money...at least in the short-term. I've chosen this route knowing it would be more expensive than simply finding an old MTB.

I want a bike that has specific characteristics that are not normally found on MTB's. I want shorter chainstays, a shorter top tube, a lower bottom bracket and a lower amount of trail. I love the agility of 26" wheels and I love really fat, smooth tires. I can get some of these characteristics in a hybrid and some in an MTB but I've never seen a bike that has all of these characteristics. So, while the recommendation to buy an old MTB is, generally speaking, a good one, it's not what I'm looking for. Think of a bike that is somewhere between a Bridgestone XO-1 and a Rivendell Atlantis.

I have communicated with a custom frameset builder and my general BikeCAD idea (not the 730 conversion I posted here) is very close to a bike he already builds. My design is based on my experience riding bikes and knowing the geometry of those bikes and figuring out what I like and what I dislike. When the time comes to commission him to build a frameset he will actually design it but I want a general template to give him that I can say "I've been riding a bike with these characteristics and I really like it". This will give him a very specific idea of what kind of ride I'm looking for. My 730 with 26" wheels is very close in geometry to the custom idea I've been working on. I don't mind spending a couple of hundred bucks on this experiment if it helps me nail down exactly what I want on a $2000 custom frameset.
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Old 10-15-13, 07:08 AM
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??
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Old 10-15-13, 07:38 AM
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Originally Posted by surreal

??
If I was a normal sized person I would seriously consider Handsome Cycles' "XOXO" since my Devil is a 700c version of that bike. But, the XOXO is relatively light-weight tubing and I weigh 400lbs. Part of going custom is the fact that he'll build a frameset that is suitable for my weight.
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Old 10-15-13, 08:50 AM
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just leave the wheels and run the MTB bars , and it's a 'hybrid' and a whole section of devotees :

here .. https://www.bikeforums.net/forumdispl...ybrid-Bicycles.

narrower 23 wide tires and it's a'fitness bike' ..

If cantilever brake bosses on the frame, they wont be useful any more

a replacement wheel set with Drum brakes will work..

I have such a wheel on my MTB-Studded tire , bring it out when there's Ice on the roads bike.

[yes , I work on V brake bikes often. I happen to like the function of the Maguras better ,
had mine 15 years , all Ive needed was to snap in a new set of brake shoes when Worn .

they literally snap on the slave piston ends .. ]

Last edited by fietsbob; 12-22-13 at 12:08 PM.
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Old 10-15-13, 09:20 AM
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Psssst-- hey, F-Bob?! A 730 Multi-Track already is a hybrid!

So, now's that part where you suggest he gets some Magura HS-33 brakes for it, right?
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Old 10-15-13, 09:45 AM
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OP is goofy then, but thats rather common here, a place to ask easy questions
and make other guess if they are serious, or Naive.

and bored writing on the company computer at work ..
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Old 10-15-13, 09:47 AM
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How long are the stays on the 730?

Doubt they're shorter than 43cm of a 1995 Trek 970. 930 should be about the same, maybe easier to find for cheap.

I'm not sure of the allure of the 730.
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Old 10-15-13, 09:54 AM
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The 1994 730 had longer-than-43cm chainstays. Tough to read the catalog scan but appears to be 43.6 or 43.8cm

Get an 18" 930 and you're gaining 6mm of ETT, easily corrected for with a stem or skooching the saddle up 6mm for a more roadie position.

1994 Trek catalog lists both the 930 and 730 BB heights @ 11.7 for most middle-of-the-size-range frames.

Last edited by LesterOfPuppets; 10-15-13 at 10:06 AM.
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Old 10-15-13, 10:34 AM
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The 1995 730 has 43cm chainstays and a 57cm ETT, which is actually longer than I prefer. I've been watching Craigslist and checking pawn shops for months and all I've seen are Trek 800's and an occassional 820. No 900 series whatsoever and those on E-bay seem to be drawing a premium price these days. The catalog year I checked for a 900 series showed an ETT of 60cm, which is way too long for me.

The allure of the 730 is that I already own one, I like the geometry and it appears I can run 26" wheels on it without making any modifications other than sticking on a different fork. The only geometry related changes I can see are a lowering of trail from 74mm to 66mm and a lower bottom bracket.
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Old 10-15-13, 10:44 AM
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Fools errand, use it as is , shop for an old MTB..
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Old 10-15-13, 10:45 AM
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Originally Posted by corwin1968
The 1995 730 has 43cm chainstays and a 57cm ETT, which is actually longer than I prefer. I've been watching Craigslist and checking pawn shops for months and all I've seen are Trek 800's and an occassional 820. No 900 series whatsoever and those on E-bay seem to be drawing a premium price these days. The catalog year I checked for a 900 series showed an ETT of 60cm, which is way too long for me.

The allure of the 730 is that I already own one, I like the geometry and it appears I can run 26" wheels on it without making any modifications other than sticking on a different fork. The only geometry related changes I can see are a lowering of trail from 74mm to 66mm and a lower bottom bracket.
You have to go down to an 18" frame 9xx to get the top tube dimension in the neighborhood of what you're looking for.
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Old 10-15-13, 11:06 AM
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I'm going to say that the OP knows enough where we're not being, like, negligent if we don't point out the drawbacks. I've spent money and done plenty of completely stupid things with bikes, but i never fret over it b/c 95% of the parts get reused in a different project or a friend's project, or whatever. What Corwin is doing is an experiment, as an evolutionary step towards future builds. Back brake aside, there's nothing dangerous about this project, so I'm not going to waste anymore time questioning the wisdom of the project.

I'd be lying if I didn't see enough Schwinn Varsity-to-26" pics online to inspire me to buy a basketcase Varsity so I can put some parts from the bin to use in making my own fake sidewinder/proto-mtb/diamond-klunk/whatever. A totally stupid endeavor, but who cares? Just having fun with bikes....
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Old 10-15-13, 11:09 AM
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For rear brake, a BMX caliper might reach.
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Old 10-15-13, 11:25 AM
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Before I spent too much money machining the 820 fork, I would get something like these:https://www.niagaracycle.com/categori...ake-pair-black. You could use the original fork and see how it handles. If it's not perfect, it would at least give you time to scrounge a MTB fork that fits for cheap/free. If you end up changing to a 26" fork, you can put canti's on it and leave the rear caliper like lesterofpuppets suggested.
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Old 10-15-13, 12:40 PM
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Need to caution you on running front brake only. I thought it was OK, too. Rode for quite a while like this and then had to make emergency stop. Without thinking I grabbed a fist full and immediately launched myself over the bars. Busted the 5th metatarsal in the left hand. Never did that again. Get a rear brake on there before you become a stat.
I like your idea of the conversion as I have done it myself, but with a road bike. Needless to say the BB was entirely too low, but the 26" wheels were beautiful in corners. Was running Conti Avenues at the time 26x1.75 baloney skins. Sweet!
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Old 10-15-13, 01:51 PM
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Originally Posted by likebike23
Before I spent too much money machining the 820 fork, I would get something like these:https://www.niagaracycle.com/categori...ake-pair-black. You could use the original fork and see how it handles. If it's not perfect, it would at least give you time to scrounge a MTB fork that fits for cheap/free. If you end up changing to a 26" fork, you can put canti's on it and leave the rear caliper like lesterofpuppets suggested.
So there is a chance those brakes might work? Do they bolt into the hole in the crown and bridge that I assume are for fenders? I measured the distances from those holes to the rims and they are with 99mm. I have no idea how wide my rims are at this point.

My 730 still has threadless headset parts on it so I pulled out the threadless fork and installed it along with my saddle/seatpost from my other bike and took it for a spin, sans shifters or brakes. I've got cheap, painful pedals on it and I'm stuck at 80 gear inches but the ride was a positive experience. Nothing wanky about the handling, at all.

I'm testing two final concepts before I start concrete steps toward a custom frameset. One is 26" wheels with fat near-slicks and drop bars.

I took this photo from a few feet away so all the vertical dimensions are distorted. Other than the bars being so high it looks pretty proportional in person, much longer and lower to the ground. And thanks Surreal, for acknowledging that I'm not committing one of the 7 deadly sins here but just experimenting with stuff I have on hand.

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Old 10-15-13, 03:08 PM
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OP- you are correct about mounting the brakes in the holes on the brake bridge and fork crown. To measure the reach, you need to go from the center of those holes to the center of the rim's braking surface. I'm not saying that the brakes will definitely work, but they might.
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Old 10-15-13, 07:28 PM
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They'll likely work. BMX calipers are great unless you need to remove your wheels a lot. If you stop to fix a flat remember to mount wheel back onto bike before inflating tire.
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Old 10-16-13, 02:27 AM
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Originally Posted by corwin1968
I want a bike that has specific characteristics that are not normally found on MTB's. I want shorter chainstays, a shorter top tube, a lower bottom bracket and a lower amount of trail. I love the agility of 26" wheels and I love really fat, smooth tires. I can get some of these characteristics in a hybrid and some in an MTB but I've never seen a bike that has all of these characteristics. So, while the recommendation to buy an old MTB is, generally speaking, a good one, it's not what I'm looking for. Think of a bike that is somewhere between a Bridgestone XO-1 and a Rivendell Atlantis.
Now the request makes sense.
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Old 10-16-13, 05:14 AM
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Originally Posted by LesterOfPuppets
They'll likely work. BMX calipers are great unless you need to remove your wheels a lot. If you stop to fix a flat remember to mount wheel back onto bike before inflating tire.
Are the Tektros that likebike23 posted a link to BMX calipers? What type of levers will work with them? I have plenty of traditional cantilever MTB brake levers so hopefully those work.
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