Has anyone retrofitted a schlumpf on their strida?

Hi all.

The problem with the speed drive is that its ratio is not accurate for a single-gear bike.
The speeddrive is designed for adding versatility to a multi-gear bike.
So, in multigear bikes, the speed drive ratio works good because multiply the options you can choose for two. (if you had a bike with 5 gear, with the speeddrive you get 10). You allways can get the right ratio between 10 gears.
But for a single geared bike like the Strida, the speeddrive is only a “less-bad” solution. The jump between the low and the high gear is too big for a fine use.
When 16 wheels, you get a very very low first gear you never can use in flat ground. The second gear is the same that the original strida.
When 18 wheels, you get a first gear “almost” the original Strida ratio (a little bit lower), but the secong gear is too high, and you cannot use it if the wind blow a little bit against you or if the ground is not totally flat. Even with flat ground, the feeling is that you must make a big effort.

Now, my veredict.

Not a accurate design for the Strida.
Very expensive.
Would I buy it again?: YES :open_mouth:
Why? Because it is better than nothing.

A last advice:
After 200 km. the effort for pedaling is decreasing a lot. I think the mechanism comes very tight from factory and It needs a little of use for a right work.
At the begining, pedaling in the high gear (with 18" wheels) was a pain. Currently is very much better.



And an added advantage for the SD.

You can secure your Strida easyly if you put your chain-lock crossing the speeddrive plate and the bottom alloy welded triangle.

This is the most safety method for locking a Strida, if you must leave it alone.


@RichardCoffey: Thanks for ATS research and your friendly words.
On Spring 10 I asked Strida europe:
“The Taiwanese 2-speed gear of the Strida MAS is said to be very unreliable. Do you know more about that?”
“The MAS Schlumpf cannot be ordered as a spare part.”
----- ? ------

@smitt53: Thank you very much for the pics, will there be more?
The Schwalbe Kojak tires of my 18" Strida, inflated at 8,0 bar, seem to lose air relatively fast (about 0,3 per day).
Did you make this experience as well?

@hydractiva: Fully agreeing to your verdict, I am sorry to say that I have trouble with your gearing description.
Please do not take this personally.

@All of you
My first impression after riding a few kilometers on the 16" Schlumpf Strida: at this moment I realized that I had not been biking for decades before I bought my Stridas in Spring 10:
The lower gear feels much too low for me and the higher one awfully high.
The smooth original 100:30 gear is suitable for a completely untrained stork leg but not the higher gear of the Schlumpf.
It’s true, with the higher Schlumpf gear you can go much faster … if you can.

But things are getting better every day…

There are no “hills” in the area I usually ride, but a few “drive-ups” or “raisings” hardly managable with the 16" original gear are nearly not to be managed with the 18" Strida. The lower Schlumpf gear lets me climb up these places without any problem, slowly of course. Acceleration in the lower gear is certainly much better than the original on flat road. After 2 or 3 rounds of the pedals it is advisable to switch to the higher gear, which brings me to shifting:
As smitt53 said, you will need practice first. But in my case shifting became automatic after 40 or 50 kilometers, meanwhile I shift almost intuitively and frequently. Always wearing high shoes, I kick the shifting button with the heel or ankle - the Strida aluminium pedals are a bit more slippery than the original black ones and support the little sideways movement of the shoes better.
Also shifting without interrupting the movement of the cranks is possible, it is just a question of the right moment (and really cool!).
With increasing practice I am on the way to handle the higher gear, my top speed on Schlumpf 16" might be around 22 km/h at the moment, and it feels the same as top speed on 18" with original gear, but at lower cadence.
By now I have ridden about 80 km with the Schlumpf 16" and about half this distance on the 18" Strida for comparison.

For better understanding of the gear mystery I did some research on the web, then I took a ruler and used these online gear calculators:



The tires:
size; name; description; diameter (measured), circumference (arithmetical); circumference (measured)

16"; Kenda Kwest; 16 x 1,50 (40-305); 38,5 cm; 120,95 cm; 121,2 cm
18"; Schwalbe Kojak; 18 x 1,25 (32-355); 42,1 cm; 132,26 cm; 132,6 cm

Based on the two measured diameters of the wheels, the gear inches were calculated, and here are the results:
the first values are calculated with wisil, the values in brackets are from the soulbike calculator.

16" with original gear: 50 (50,4) Schlumpf low: 40 (40,4) Schlumpf high: 66 (66,7)
18" with original gear: 55 (55,3) Schlumpf low: 44 (44,2) Schlumpf high: 72 (72,9)

From my subjective feeling and corresponding to the results I have to say that the higher Schlumpf gear with Kenda 16" tires is certainly not the same as the original, as hydractiva mentioned, maybe her/his gear calculations are based on different tire sizes?
Anyway, I’ll have to train a huge load before changing the wheels of my Stridas against each other :mrgreen:

Here is another interesting thread about sport duos:
savedbybikes.com/blog/blog/sport … mpression/

Did you know that Strida Europe offers the MAS again, “available third week of June”?
Update 06.07.10: “available last week of july”
Update 06.08.10: “available last week of august”

Warmest regards

Hydra’s descriptions of 16" gear inches are inaccurate, at least according to the official specs. Check out the savedbybikes.com link shared by Blackstridaaustria and also areaware.com.

Sorry for the mistake.

The high gear with 16" is higher than the orginal Strida one.



Here is the opinion of Mark Sanders about the ATS and Schlumpf versions of speed-drive:

Hmm. Are there differences between the bottom bracket of the Strida 5.2 and the DS? Was playing around with the idea to do a 1 to 1 swap of the ATS for the Schlumpf to do a comparison before I reinstall it on the Strida 5.2.

I think the BB shell is the same on all 5.x Stridas.

Hi Blackstridaaustria,

Just out of curiousity, as we know that you have anodised many parts of your Strida into black, why didn’t you order the speed-drive kit with black crank arms + black easy-shift levers instead of the one with sliver crank arms from Schlumpf? :unamused:


Hi Amuro,

nice question…

Meanwhile a lot of time went by, at first was the Schlumpf, then the “black phase” overwhelmed me, inspired partially by users of the HK Strida Club, who are customizing their bikes in various ways.
At the moment are, of course, black crankarms and black kick shift levers to be found on my black Strida.:laughing:
These black parts were brought by my dear Mrs. Blackstridaaustria directly from Switzerland to Austria as a present. :smiley:
The silver ones I kept for Mrs. BSA’s brushed silver Strida, maybe the time brings a second Schlumpf?

Any other questions?

Warmest regards

Hi Blackstridaaustria,

Oh I see. So every part of your Strida is in black now. :sunglasses:

Best regards,

Did it again…

…so the silver Strida is Schlumpf powered also :sunglasses:



I recently wrote to ATS to ask them if a Speed-Drive for my Strida is available direct or through a US distributor. Here is the reply I received yesterday:

Dear Richard,

We don’t have distributer in USA.
We can sale directly. But U have to pay the freight cost (Ship out from Taiwan).
And U have to make sure, U can apply the ATS-speed drive on your bike. Pls check your bike first:
(1) Is your bike can fit our standard BB?
(2) Do U have belt chainring on your Strida already? (Right length of belt and chain ring…)
(3) Do U know how to install ATS-speed drive?

Best Regards
Mark Liu

Their prompt and considerate reply is a big step forward, but apparently they do not have a Strida-specific installation kit available, as Schlumpf does.

I am not certain how to answer their three questions for my single-speed 2010 Strida 5.0. I would greatly appreciate any advice on how to proceed.

Thanks and Regards,

Dear Richard,

I’m sorry to say, but there will be big problems to find/create the missing parts.

The standard ATS bracket is made for bottom bracket shell diameters of 33.6 - 34.5mm, according to their website.
The Strida bottom bracket shell has a diameter of ~ 52 mm, you will need an excentric bottom bracket mechanism similar to that you have now in your Strida.
Similar, not equal, the new one has to be more broad!
So I think it’s not possible to modify the existing bracket mechanism…

The 80 teeth beltwheel you will need is not available as a spare part, as far I know.
(I will try to verify that and ask Ming about it.)
Btw, Mr. Schlumpf had obtained these 80 teeth beltwheels from Ming Cycle directly, he did not make them himself.
Mr. Schlumpf also told me that these beltwheels were not manufactured precisely; therefore he had to chisel them out ~ 0,4 mm.

The belt should be no problem.

Just like the Schlumpf drive, here is an interesting video about the process:

Please note: The video is showing a chamfering procedure, done by a hand milling tool.
This procedure is needed for all bikes, except the Strida (due to the excentric bottom bracket).

Best regards,


Below a few pics of the new buttons and plates:

Detail for our weight-weenies:
The new black buttons are much more heavy than the old silver ones; ~ 9 grams instead of ~ 3 (per piece!) :smiley:

12 more pics of the Schlumpf speed drive are here:

1600 x 1200

480 x 360



I have a bad experience with the old kickplates, I tried them twice but I removed them twice because of the bad shifting: I regularly found myself "pedalling in the air " when the traffic light was becoming green. It appeared very difficult to balance the preload between the 2 kickplates.

A big advantage of the kickplates is that you can’t loose the shift buttons… :laughing:

Did Schlumpf reduce the stiffness of the kick plates or are the the magnets so strong that they can always keep the kickplates in contact with the crank levers?

Hello Bietrume,

I did not notice any difference in the plates.
The magnet seems indeed strong, at least for it’s thickness, just ~ 0,8 mm.

I suggest to ask Mr. Schlumpf himself about your problem:

(Please replace [at] with @)

Above new plates (and the drive) are not for myself, they will be sent to an American Strida fan.

How to „do the Schlumpf“ 2-speed conversion DIY
(Version 2.0 with more details)

Important note: Ming cycle definitely recommends assembling neither the Schlumpf speed drive nor the ATS speed drive yourself. There will be no warranty by Ming cycle!

Personal note: The ATS speed drive is not available as a retrofit kit for Strida. The Schlumpf speed drive kit will be delivered with five years full warranty.

Before doing anything else, please check the wear of the freewheel! It would be senseless to install a two-speed drive together with a worn-out freewheel!

The required tools and detailed information can be found here:
Strida workshop tool guide

Before starting, mount your Strida into a bike stand, or, if you don’t have a stand, turn your bike upside down. Here’s an example of how that can be done:

Take two small blocks of wood and put them below the grips. If the saddle is in a lower position than shown in the pics, take some old books or another, bigger block of wood and put it under the saddle. (The cord between the small wooden blocks is helpful to keep the correct distance, but is not implicitly necessary.)

Let’s start

  1. Loosen the big groove nut of the bottom bracket by using a 60 mm hook key

  2. Remove the pedals by turning clockwise (for the left pedal), and turning counterclockwise (the right pedal) with a 15 mm flat wrench (caution: accidentally, a 16 mm wrench is shown here – that’s the wrong size!)

  1. Remove the belt tension bolt (and the kickstand) with a 6 mm Allen key

  2. Remove the left crank

a. Remove the crank cover and the crank bolt with a 8 mm Allen key

b. Remove the small conical part of the crank extractor tool (depending on the used tool!) and turn the bolt inside the tool out as far as possible

c. Screw the tool, as far as possible, in the crank thread

d. Now screw the bolt mentioned in point b) in the tool, the extractor tool should be held with one flat wrench (16 mm), the bolt should be turned with another wrench (15 mm), in brackets are the wrench sizes for the example BBB tool BTL-14

e. The crank will now be extracted from the bottom bracket axle

  1. Remove the rear wheel bolt, the metal and the plastic washer, the counterpart of the magnet, the two plastic washers below the magnet’s counterpart and the so-called magnet spacer, part.nr. 338, with a 4 mm Allen key (caution: if the magnet spacer is bent or broken, replace it!)

  2. Remove the rear brake caliper by turning the two caliper bolts with a 5 mm Allen key (caution: The two washers, part nr. 7 of drawing 340-04, between caliper and frame might fall down and get lost!)

  1. Remove the snubber bolt, snubber and the corresponding washer by using a 5 mm Allen key (caution: Do not lose the washer!)

  1. Release belt tension by turning the excentric bottom bracket, usually the bracket should be turned clockwise (seen from the left side) to release, but the bottom bracket can be mounted upside down. If your bottom bracket is mounted that way, it must be turned counterclockwise to release tension.
    (Further information is here:
    Strida for someone tall
    18" Wheel Upgrade: not that easy…
    How much play in Strida 5 belt?)
    The bottom bracket can be moved easily by inserting a 6 mm drift punch in the tension (kickstand) bolt thread.

  2. Carefully pulled sideways, while turning the beltwheel, the belt can now be removed from the belt wheel.

  3. Now remove the rear wheel, the belt should be pushed near the locking mechanism of the frame

  1. Remove the bottom bracket groove nut

  2. Pull out the old single-speed bottom bracket from the right side of your Strida

As everything except the belt has been removed now, I suggest to have a break and think about the next steps. It’s time to open the frame to remove the belt, but this is a bit dangerous, the Strida will become unstable. To avoid any damage we should open the frame for a short time only.

  1. Changing of the belt:
    a. Move the old 1440 belt as near as possible to the locking mechanism
    b. Take the new 1360 belt in the right hand and grab the bottom tube simultaneously

c. Grab the steering tube with the left hand below the frame lock

d. Open the frame lock with the left thumb, then push the bottom tube downwards with the right hand

e. Let the old belt fall down with a little help from some spare fingers :smiley:

f. Contrive the new belt over the bottom tube

g. Lock the frame again

  1. Put the belt over the freewheel and push the wheel onto the axle (caution: do not clamp the belt between the freewheel and the lower caliper mounting of the frame)

  2. Remove the big groove nut from the Schlumpf drive, push it into the bottom bracket mount, hold the belt between drive and frame and be careful not to clamp the belt. Secure the drive with the groove nut, do not tighten it yet

  3. Move the drive to the lowest belt tension position and pull the belt over the belt wheel from inside

  4. Unscrew the kick shift button and the crank bolt with its washer

  1. Push the single crank onto the axle and secure it with bolt and washer (caution: do not use a thread locking compound like Loctite on Schlumpf parts!)

  2. Tighten the crank bolt to a torque of 50-55 Nm (40,6 lb ft) by using a 14 mm socket wrench (it’s recommendable to follow the instructions of the Schlumpf speed drive manual, chapter B-4/Axle bolts, to be found here: haberstock-mobility.com/Manual Schlumpf speed drive.pdf)

  3. Mount the rear wheel bolt, washers, magnet counterpart and magnet spacer, for correct sequence please refer to the pic below or to the exploded drawing of the Strida manual (caution: do not tighten the bolt too hard - the magnet counterpart should be easily moveable - and use a thread locking compound – Loctite or similar!)

  4. Mount the snubber bolt, bearing and washer (caution: washer between bearing and frame, do not forget to use Loctite!)

  5. Mount the brake caliper (caution: use loctite!)
    a. Take the caliper in the right hand

b. Push the first, upper washer onto the caliper

c. Slide caliper and washer behind the frame mount

d. Press the caliper softly against the frame mount to secure the washer

e. Screw in the upper bolt (caution: do not forget Loctite!)

f. Push the second, lower washer onto the caliper

g. Rotate the caliper to the frame mount

h. Screw in the lower caliper bolt (caution: use Loctite!)

i. Tighten both bolts to a torque of 8 Nm (5,9 lb ft)

j. It might be possible that the brakepads must be readjusted, please refer to the Strida manual, page 17 Strida manual revised.pdf

  1. Mount the belt tension bolt (and kickstand) and adjust belt tension. (caution: the speed drive manual recommends not to use Loctite on Schlumpf parts, I mean this bolt is an exception!)

  2. Tighten the big groove nut really hard, recheck belt tension

  3. Mount the kick shift button(s) and adjust it (them) carefully. For this step, please refer to the Schlumpf drive manual chapter B-5 or to the information supplied with the drive.
    haberstock-mobility.com/Manual Schlumpf speed drive.pdf

  4. Finally, mount the pedals, alternatively kick shift plates can be used. Further information about these plates is also available in the speed drive manual. To use the forum search might also be useful, keywords „kick shift plates“ and „kick shift buttons“.

Have a safe ride with your new two-speed Strida!

Schlumpf FAQ’s site

Schlumpf mount V2.0 1600x1200



I been reading this thread since yesterday, I recently bought a strida LT (single speed) to use for daily commute from home to office here in France, I thought I wouldn’t be needing the gear option that’s why I bought the LT, but i was wrong…

Is Schlumpf speed drive compatible for my LT? I’m not well verse about the gearing description. On hydra & Blackstridaaustria post, it looks like it is not advisable to do my planned upgrade.


Hello and welcome,


I’ve meant it’s not advisable for people without some mechanical skills to do the upgrade themselves.
(And it’s still not that cheap…)

For an experienced bike mechanic should neither the ordering nor the installing of a Schlumpf drive into a Strida be a problem, I believe.

Sadly is the upgrade of an LT to a 3-speed drive (the new EVO) technically impossible, however, with the EVO you can get more gear per money.

Every (further) question about the Schlumpf drive is welcome… :smiley: