Thursday Magic: The “Fake” 7-speed Hub

from Rookie’s keyboard,

Hello, friends

Today, I will tell you about the “fake” 7-speed hub I discovered while working on some ancient MTB.

First, you need to know is that there are two types of 7-speed hubs – a “dedicated one” and a “fake” one.

The first is short and works only with 7-speed cassettes (or smaller ones with a spacer).

The other one is “fake” as it’s essentially an 8-speed hub with a spacer and a 7-speed cassette or freewheel.

Many entry level retro MTBs are equipped with those “fake” 7-speed hubs.

To know if you have a 7-speed specific hub, examine it and search for a spacer behind the largest cog/gear. A spacer is essentially a thick washer designed to fill space.

If you can see a spacer behind the 7-speed cassette, then the effective length of the hub is greater and it can accommodate 8, 9 and even 10-speed cassettes.

Shimano’s 8,9,10,11 and even 12-speed cassette hubs have almost the same width. And you can quickly upgrade to more speeds without having to change the hub.

This is accomplished by reducing the space between the cassette cogs and thinning out the chain with each gear jump. Hence multi-speed chains are known to be weaker than single-speed models.

The overall thickness of the sprockets, however, stays the same across all cassettes.

Freewheel Or a Cassette

Since we are talking about a 7-speed drivetrain (an outdated but still practical setup), there’s a chance that you have a freewheel rather than a cassette.

If you have a freewheel, the hub can’t operate with more than 8-speeds as there aren’t freewheels designed for more gears.

Freewheels come with their own ratcheting mechanism and screw onto the hub.

Therefore, hubs designed for a freewheel are incompatible with a standard cassette.

You can find out whether you have a freewheel or a cassette by examining the front of the cassette or freewheel.

A freewheel has two parallel dots on the front whereas a cassette does not.

The images below show both a 7-speed cassette and a 7-speed freewheel.

Converting From 7-speeds To 10

A conversion from 7 to 10-speeds requires:

Case A. No Hub Replacement

If the hub is “fake” and therefore 10-speed compatible, you will need:

• a 10-speed cassette
• a 10-speed chain (You can’t use a 7-speed chain because it’s too wide and will rub against the surrounding cogs.)
• a 10-speed shifter
• a new gear cable and housing

Case B. Hub Replacement

If you have to replace the hub (it’s a real 7-speed model), you will need the following parts:

• а 10-speed hub (You will have to buy a new wheel or rebuild the old one.)
• а 10-speed chain
• а 10-speed shifter
• а new gear cable and housing

1x Drivetrain

If you plan on switching to a 1×10 drivetrain, you will also need a narrow-wide chainring to ensure decent chain retention.

It’s also highly advisable to get a chain guard or use the existing front derailleur as one by adjusting it via the limit screws.

Are More Speeds Worth It?

Theoretically, yes. In practice – it depends. I have a 7-speed road bike commuter that offers sufficient gearing at the moment.

But in general, a conversion from 7 to more speeds has the following benefits:

• Smaller gear jumps

The greater the number of gears, the smaller the gap between them. As a result, the rider has an easier time maintaining high cadence.

Cadence is a term referring to the rotations of the cranks per minute. High cadence (e.g., 90RPM) is associated with greater average speed and minimal energy expenditure.

• Greater range

A 10-speed cassette can offer substantially lower gearing. Some 10-speed MTB cassettes have a large rear cog with over 40 teeth.

• 1x Drivetrain

Thanks to high-capacity cassettes, 1x drivetrains have become a lot more popular, especially in the world of MTB.

A 7-speed cassette, however, is too limited to make a 1x drivetrain viable. 10 or more speed cassettes solve that problem by offering extra cogs.

The Price?

10-speed components are more expensive, and you will have to buy many to make the conversion possible.

You will have to wait for the new parts to arrive (if you can’t find them locally) and then invest 1 or 2 days in mechanical work.

Of course, one can always pay a bike shop like ours to perform the conversion, but if you have the needed tools, you can save some money and perform it yourself.

Until next time,

Rookie