One of The Craziest Wheel Conversions I’ve Heard About

from Rookie’s Keyboard

Hello, friends

Today, I am going to talk about one wheel conversion that I was asked about in a comment a month ago, namely putting 26-ers on a 700c frame

Overall, I’m against it.

Obviously, a 700c frame has more than enough clearance for 26-ers as it’s designed for bigger wheels.

But the conversion has some pretty significant issues: 

  • If you have rim brakes, the brake shoes will end up at the wrong location (too high) to grab the rim. So, you will have no functional brakes.
  • The bottom bracket will get super low and will cause pedal strikes.

Rim Brakes = Nightmare For Wheel Conversions

Rim brakes are the absolute worst for performing any wheel conversion. 

Let me explain.

A 700c frame is built for 700c wheels and those have a rim with a 622mm diameter.

On the other hand, 26″ wheels operate with 559m diameter rims.

That’s a 63mm difference in diameter(I calculated this in my head – what a math prodigy I am :)

If your new host frame has rim brakes, they will be located about 3.2cm higher than where the 26″ wheel will need them to be. The outcome is that you will have no brakes unless some “shaman” tactics are deployed.

Possible solutions(to the rim brake issue)

  • Caliper Extender

If the frame operates with caliper brakes and has rear rack mounts, you can install a caliper extender adapter to lower the brake and allow it to reach the rim of a 26″ wheel.

Caliper Extender Frame

Caliper Extender Fork

A similar extender could also be installed on the fork.

You can purchase those from online platforms such as eBay.

  • BMX Caliper Brakes

Another alternative is to get long-rach BMX caliper brakes such as Odyssey 1999 or Dia-Compe Bulldog. Those will also allow you to run wider tires (if the frame and fork have clearance for those in the first place).

Ultimately, however, every setup is different and some annoying tinkering will be required. And if you have accessories (e.g., fenders), the game difficulty increases.

  • A Lower Seat Stay Bridge(only if you have the skills)

One could theoretically weld or braze on a second seat stay bridge under the original one and mount a brake to it.

But this method is super complicated for the following reasons:

  1. Only possible if the frame is made of steel.
  2. You need advanced welding or brazing skills as bike tubing is super thin.
  3. Someone has to machine the seat stay bridge and heat treat it.
  4. Repainting (the easiest part).

V-brakes or Cantilever Brakes

If your system consists of V-brakes or cantilever brakes, we have a few different alternatives.

  • Clamp-on V-brake mounts

There are bolt-on V-brake mounts that you can attach anywhere you want on the seat stays or fork.

But those mounts are expensive. And the price doubles if you need 2 sets.

Disc Brakes Make Life Easier

Disc brakes won’t be affected by the new wheel size because the disc rotor is always in the same place regardless of how big or small the wheels are. 

The frame and fork will therefore“welcome” the new wheels without complaints.

And this is the ideal situation, IMO.

Alternatively, you could also consider the following combinations:

  • Front Disc Brake +“Fixie Rear Brake”(or a coaster brake)

You could get a fork that supports a disc brake and combine it with a fixed-gear drivetrain (the fixed-gear will allow you to stop by resisting the pedals).

This is a super unusual combo but provides a lot of braking power and eliminates the issue that rim brakes create when installing 26″ wheels on a larger frame. Of course, if you don’t like fixed-gear braking, you can install a coaster brake.

The Geometry Will Change Too

As already mentioned, the smaller 26″ wheels will lower the bottom bracket. 

The change will decrease the bike’s clearance. The downtube may even hit the ground when riding on off-road terrain.

You may also experience a pedal strike(the pedal hitting the ground when riding on technical terrain and cornering). This issue is more likely to occur if you use longer cranks such as 175mm models.

And if you use shorter cranks (140mm or so), the chances of pedal strikes are of course reduced.

The bottom bracket drop can be negated by installing a wider tire that will make the overall circumference of the wheel closer to that of a 700c model with a slim tire. But that will be possible only if the frame and fork have clearance for a tire of that width.

Having said that, a lower bottom bracket has a positive side too – it increases the bike’s stability by lowering the center of gravity.

The Pros of 26″ Wheels Are Nice…But Are They Enough To Justify The Conversion?

26″ wheels are cool and offer the following pros:

  • Strength

A smaller wheel is a stronger wheel when all variables such as rim material are the same

A quality 26″ inch wheel can handle a lot of abuse. Hence why 26″ wheels are often seen on “ghetto” touring bikes.

  • Clearance

If the conversion is done with skinny tires, it will be easier to fit racks and fenders on the bike.

But the skinny tires will exacerbate the bottom bracket issue.

Another way?

You may also consider a 650B/27.5″ conversion. 

27.5″ wheels operate with 584mm diameter rims – only 38mm less than that of a 700c wheel.

Also, that method won’t lower the bottom bracket nearly as much as 26-ers would. If the tire is wide enough, the bottom bracket height will remain unchanged or…even increase.

There’s a lot of info about this conversion online as it was pretty common back in the day. 

Overall, I wouldn’t install 26″ wheels on a frame designed for something larger. I just don’t think the effort is worth it. 

And if you want to run 26″ wheels for some reason, just get a retro steel MTB. You can find those for cheap almost everywhere. 

I hope the info was useful.

Until next time, 

– Rookie






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