Recognize its bottom bracket axle diameter.


4 main versions of existing axle diameter
4 main versions of existing axle diameter

The LIFT MTB bicycle crankset motor is designed so that you can keep the same bottom bracket bearings when transforming your bike into an electric bike, which in addition to being a simpler operation for the conversion, also to go faster during processing.

 

 

There are 4 main versions that are found in 80% of cases:

 

-Diameter of axle 30mm: Rotor, E13, HXR, Race face (version with aluminum axle).

-28.99mm axle diameter: SRAM DUB (version with aluminum axle).

-Diameter of axle 24mm: Race face (steel axle version) and Shimano hollowtech, some FSA

-Diameter of axis 22mm / 24mm (22mm left side, and 24mm right side): SRAM (gxp)

 


If you want to check the diameter of the crank axle of your bike to assemble our crankset motor kit and transform your bike into an electric bike, it takes less than a minute to disassemble a SHIMANO / SRAM / RACE FACE / HXR crankset. / ROTOR ...

 

Here is how to proceed:


-1- SHIMANO cranksets with thru axle:


On a SHIMANO crankset, you just have to completely unscrew the two small BTR pinch screws, then unscrew the large torks wrench (usually the screw is plastic) which screws in the axle.

 

Axle size found at SHIMANO:

-24mm for 100% Shinano thru axle cranksets

(this is the most common standard which represents 70% of sales!)


video of electric motor for bicycle

Here is how to disassemble the crankset in video.

 

From the 40th second to 60 second on the video:



-2- SRAM cranksets with thru axle:


You just have to unscrew on the left side the smaller of the two BTR screws which are screwed in the axis

 

-1- We release this BTR screw.

-2- Once released, the screw turns freely a few turns.

-3- The screw becomes harder to unscrew again when the small BTR screw comes up against the larger one, it is generally there that we hesitate to force, but you can go there you have to continue to force the unscrewing, because in fact the small screw that you unscrewed will come into abutment on the larger screw, which will allow the crank to be extracted.

 

Axle size found at SRAM:

-22 / 24mm for steel axles (in this case it is often GXP engraved on the crankset or on the bearings)

-29mm for aluminum axles (DUB marked on the crankset or on the bearings)

-30mm some versions are released in 30mm aluminum but this is rather rare at SRAM.

 


video of electric motor for bicycle

Here is how to disassemble the crankset in video.

 

From the 40th second to 1 minute on the video:



-3- RACE FACE pedals with thru axle:


You just have to unscrew on the right side the smaller of the two BTR screws which are screwed in the axis

 

-1- We release this BTR screw.

-2- Once released, the screw turns freely a few turns.

-3- The screw becomes harder to unscrew again when the small BTR screw comes up against the larger one, it is generally there that we hesitate to force more when we do not know the principle, but you can go there You have to continue to force the unscrewing because in fact the small screw that you unscrewed will come into abutment on the larger screw, which will allow the crank to be extracted.

 

Axis size found at RACE FACE:

- 24mm for steel axles

- 30mm for aluminum axles


video of electric motor for bicycle

Here is how to disassemble a RACE FACE crankset in video.

 

From 1.10 minutes to 1.45 minutes on the video:



 Once disassembled you can measure the diameter of the crank axle on each side where it bears on the bearing or the inside diameter of the bearing which is on the bike, thanks to a caliper. (See photo)

 

-Diameter of axle 30mm: Rotor, E13, HXR, Race face (version with aluminum axle).

-28.99mm axle diameter: SRAM DUB (version with aluminum axle).

-Diameter of axle 24mm: Race face (steel axle version) and Shimano hollowtech, some FSA

-Diameter of axis 22mm / 24mm (22mm left side, and 24mm right side): SRAM (gxp)

 

AXLE 30MM carbon face race crankset
AXLE 30MM carbon face race crankset

-4- Special cases: cranksets with crimped axle


bsa case set with E-MTB
Crimped BSA case

 

Some cranksets of all brands use crimped bottom brackets, that is to say that the bottom bracket bearings and the bottom bracket are one and the same inseparable piece.

 

These are cranksets which generally date from 2005 or before most brands have replaced this type of crimped case by the standard thru axle cited above (case 1/2/3).

 

The dimensions of a BSA bottom
The dimensions of a BSA bottom

 

This type of crimped crank axle exists only for versions of frames with a BSA type thread, the bearing / axle assembly therefore comes to aim in the frame, see dimensions opposite.

 

To adapt the conversion kit to an electric bicycle, this crimped bottom bracket assembly must be unscrewed from the frame, to be replaced by external bearings such as the 1/2/3 cases, which will allow a thru axle with a diameter of generally 24mm to be fitted.

 

 

The axis of the LIFT MTB crank motor will then slide into the bearings.

 


Additional information on crimped bottom.


 Brands and models of crankset which used this standard of crimped case, and which one finds on bicycles generally before 2005 and are:

 

- Crankset with SQUARE axle version whether shimano / sram / race face ...

- Shimano OCTALINK version crankset.

- ISIS version crankset (race face, fsa ...) TRUVATIVE HUSSEFELT and TRUVATIV HOLZFELLER.


Crimped bottom with square axis
Crimped bottom with square axis
Crimped bottom with OCTALINK axis
Crimped bottom with OCTALINK axis
Crimped bottom with ISIS axis
Crimped bottom with ISIS axis


 

To recognize this crimped standard:

 

There are two particularities to recognize this type of box:

 

-1- The number of screws:

 

These are 3-piece cranksets, so we have two cranks, left and right, and the axle / bearings assembly referred to in the frame.

 

There is therefore a tightening screw on each side of the cranks on this type of crimped axle.

 

Additional info:

The other models with thru axle presented above (and more common), are in 2 pieces so we will have a single crank and a crank / axle assembly in one piece.

There are therefore only screws on one side of a crank, on through-axle cranksets, the other opposite side being generally simply hollow.


 -2- The clamping imprint of the case:

 

We see the typical imprint of the internal lugs to come and put the loosening tool inside the frame.

 

(Below is a view of the 2 types of tools with lugs which allow the crimped cartridges to be removed.)


Crank puller tool.
Crank puller tool.

 

To remove cranks with a crimped box type ISIS, Square, or OCTALINK.

 

It will first be necessary to extract the crank using a crank extractor as in the photo opposite and as in the video below.


LIFT-MTB video

Here is how to disassemble the cranks of a crankset with a set bearing / axle crimped in video.



Read a complementary article below on the different types of bottom bracket bearings:



bolt on motor
Transform your bike into an electric bike




e-bike kit made in france