Converting a 26" Mountain Bike into a 700c Bike

A few weeks ago, I damaged my 700c steel race bike frame which I bought as a NOS (New Old Stock) without any warranty. It was hurt to the extent that I neither wanted to ride it nor wanted to sell out of safety concerns. I'd rather don't make any money than sell faulty products...

In my stable I have a 26" mountain bike, at one point I converted it into a road bike for my daily errands - like shopping, recycling paper/alloy, or riding around town. Both of the bikes are parked in my home office and I pass them many times daily.

Rear Wheel Awakening

One day, I was looking at both bikes and it came to me, that I could try if the 700c rear wheel would fit into the 26" MTB frame. I followed my instinct and was surprised, that the rear wheel of the race bike worked perfectly in the mountain bike frame:

- there was enough space behind the chainstay bridge;

- the hole in the seat stay bridge

a. would fit the bolt of my road bike caliper brake

b. was perfectly sized for the brake reach (distance mounting bolt → brake pad mounting slot) for my caliper

brakes to be used on a 700c wheel.

This surprising 'discoverthat of the 700c rear wheel would work in a 26' frame started a new direction of what I could do with the higher quality parts of my damaged road bike frame.

Decisions

After some deliberation with myself and my wife, I've decided to upgrade my 'old' mountain bike with road bike parts rather than buy a 'new' road bike frame. My 3rd bike is a roadie, it would satisfy my occasional 'need for speed'.

Fork

Both of my frames would take a 1 1/8' steerer of a front fork. I could mount the complete carbon road fork with the Shimano R7000 caliper brake and the front wheel (wheelset, inner tube, tire) on my 26' mountain bike frame.

The headsets of both frames were different, I combined the parts of three (!) different headsets until it worked properly on the 'new' bike.

Frame

Some years ago, I bought an alloy 26' front suspension fork MTB frame (21' high), Wheeler Pro 2900, as a NOS (new old stock). The seller contacted me that he did not have the advertised blue color but only a matte black with white graphics - I accepted gladly because a matte black looks more neutral.

Steering:

I've used my 'original' white Deda handlebar (420mm) with a black 120mm Deda Mud stem. I've cleaned the residue of the old bar tape which was messy and took, with the help of different cleaners, quite some time. I've returned the Shimano 105 (R7000) STI shift/brake levers to my now shiny white handlebar.

Shifting/Braking

* Shifting:

For shifting, I've used Shimano R7000 11-speed 105 STI-shift/brake levers and the long rear derailleur from my road bike. All the parts were easy to mount except for the front derailleur.

Mountain bike front derailleurs are designed as pull-ups (from the top) - but road front derailleurs are pull-down designs with the cable running along the downtube and below the bottom bracket. To compensate for the discrepancy I've designed a 'noodle' with an additional 31.8mm double cable guide. This way, I could use the traditional road bike front derailleur on a mountain bike frame for several 100s of trouble-free kilometers. Unfortunately, the Shimano R7000 front derailleur did not work as it was supposed to: the upshift needed too much energy, and the downshift literally threw the chain to the lower chainring.

In my parts bin, I had a Shimano FD-CX70-F-T Front Derailleur- Direct Mount - Top Pull - Road - 2x10-speed, "developed specifically designed for cyclocross". When my mind serves me correctly, this is actually Shimano's only top pull road bike front derailleur...I will write more about it in a separate post.

* Crankset

I had to use my older Shimano Sora 9-speed crankset due to the wider Q-factor (distance between both crankarms) of 152.2mm.

a. my newer 11-speed Shimano RS500 road bike crankset has a Q-factor of146mm

b. Shimano 2 x 11-speed Shimano GRX gravel bike crankset has a Q-factor of 151mm

The Sora 9-speed Q-factor would be wide enough for my mountain bike frame, but my RS500 would be too close to the wider chainstays and occasionally touch them, depending on my power on the pedals.

*Rear Cassette

My 11-speed road bike cassette (11-32T) worked on my new 135 OLD rear wheel trouble-free. I've cleaned it before assembly and the red spider is shining through the chain wheels.

*Chain

The 11-speed KMC SL chain works fine with the 9-speed crankset and 11-speed rear cassette.

- Braking:

I've used the Shimano R7000 front caliper and a no-name front caliper on the rear. The seat stay bridge is not designed for a recessed nut so I had to use a longer screw and used a simple nut to fix the original front calipers into place. I the pads of both caliper brakes I've replaced with Kool-Stop rubber, they are softer and friendlier to my alloy rims than Shimano's originals.

Wheels:

- Front Wheel

I've used my complete front road bike wheel (incl. 'old' inner tube and tire)

- Rear Wheel:

I've mounted the tube and tire of my old 130mm wheel onto the 'new' rear wheel, 135mm. The rear wheel was the only purchase of the whole build for NT$2.000 or USD 65.25.

* Alloy black, CNC & polished braking surface

* 28 black spokes

* chromed nipples

* Bitex hubs with 4 sealed bearings

* weight: 950g, incl. rim tape but without inner tube, tire, quick release.

(to be continued)