As shown here in the TIRES / RIM topic, even conventional bicycle technology is not spared from problems. Blistering tires, rattling rims or cracks in spoke holes and broken spokes have accompanied the Stromerbikes.
While rims from AlexRims repeatedly had problems with cracks in the spoke holes, especially on the rear wheel, since switching to the manufacturer Rodi in the summer of 2023 there have also been spoke breakages. Stromer is often accommodating in the event of such problems, as well as cracks in the rims, replacing entire wheels, front and rear, under warranty or repairing or resealing them. As you can read in forums and Facebook groups, these options are not always sustainable and the same problems can occur again.
How can you escape this hamster wheel?
To date (as of April 2025), there is no official solution to the problem of broken spokes that I know of. Anyone who knows of such a solution is welcome to share it via the comment field below or 'Contact/Feedback'.
Resourceful dealers in the large electricity markets of Belgium and Holland have found an unofficial solution to repair broken spokes. The details can be found in the chapter 'Cracks in spoke bores, broken spokes'.
In addition to repairing and re-spoking or replacing broken spokes, you can also switch to a different rim manufacturer or model. Below you will find a few alternatives to the original rims from AlexRims or Rodi.
Legal basis
When changing to an alternative rim, the question of legality arises. Is such a 'third-party replacement' permissible?
In contrast to tires, which must be ECE-R75 tested, rims are not explicitly mentioned in the type approval or Certificate of Conformity (CoC). See here die CoC des ST5/ST3.
They are considered approved with the version installed by the manufacturer.
If you want to use a different brand or a different type of rim, it still gets confusing.
In principle, the (warranty)Provisions of myStromer AG. Stromer remains inconsistent in its choice of rims across the model series. Newer Stromer models, e.g. the ST3 Pinion, switched from Taiwanese manufacturer 'AlexRims' to 'Rodi' (Spain) from around mid-2023. The old ST2s and the ST5 were delivered with branded (+Stromer) rims from DT Swiss (H612). The ST5 ABS / Pinion and ST7 ride with such rims without branding.
Alternative rims
Instead of a repair, you can replace the original rims with a rim of the same or even higher quality. You can find a few alternatives online.
The information listed is for information purposes only. No legal legitimization can be derived from it!
DT Swiss H612
The DT Swiss H612 cannot be found anywhere at Stromer with this designation. However, it was used with the brand name +Stromer- on the ST2S and ST5, and again without the brand name on the ST7.
It is a valid replacement for all bikes with rims from AlexRims or Rodi. NB: The ST3 and ST5 have the same CoC in the EU.
DT Swiss U683
The DT Swiss U683 has the same dimensions as the DT Swiss H612 but is reinforced.
DT Swiss writes:
The increased rim wall thickness and the larger cross-section of the U 683 rim ensure a very high overall stiffness. This is particularly important when used on E-Touring bikes, which tend to be ridden with a higher total weight. With an approved maximum system weight of 180 kg, the 27.5″ rim offers a correspondingly high level of robustness and therefore durability.
Ryde Andra 29
The Andra 29 from Ryde ist nicht baugleich mit den Felgen von ‚AlexRims‘ und ‚Rodi‘, passt aber für Reifen der Dimension 650B und ist speziell für Nabenmotoren und Lastenbikes konzipiert. Sie kann here gekauft werden.
Ryde writes:
With an inner width of 29 mm, the Andra 29 is an ideal rim for the latest e-cargo bikes and wide tire trends and can take loads of up to 150 kg. The thick, wide nipple bed allows various drilling patterns, perfect for use with e-hubs. Even 2 mm offset holes are possible
RAD15 - Storm33
The RAD15 Storm33-584 STROOP is advertised by the wheel manufacturer Spaakshop BV as a Stromer and Opium replacement. (Alternative link: rohloff.nl)
With the appropriately named 'Stroop rim' (STROmer & OPium), the Dutch rim manufacturer RAD15 presents a special rim that is intended to solve the wheel problems of various speed pedelec brands. To a small extent, these are due to the quality of workmanship, but they are mainly due to the use of unsuitable rims. RAD15 is now launching the 'Storm33' specifically for Stromer and Opium speed pedelecs. It has the correct positioning (angle) of the 32 necessary spoke holes.
Here also the 28-hole version for the front wheel.
Price: The wheel manufacturer Spaakshop writes:
New spokes with the STROOP rim and reinforced Sapim Strong spokes and nipples cost around € 233 incl. VAT. (Source)
New DT Swiss H 1900 Spline front wheel
If you want to avoid re-spoking with a new rim, you can also replace the whole wheel. After a figure of eight in the front wheel of my ST3, I ride the DT Swiss H 1900 Spline. Straight Pull Line is a technology in which the spokes run straight from the rim to the hub without forming a bend (J-bend). The letter H stands for Hybridwhich means that these products have been specially developed for use on e-bikes.
Unfortunately, the rim is not available separately. If you want the rear wheel to be identical, you have to buy two wheels and re-spoke them for the rear. Note that the number of spoke holes at the rear is 32!
Spoke calculator / Spoking
Wenn andere Felgen eingesetzt werden muss der Motor neu in diese eingespeicht werden. Bei Nabenmotoren kommen aufgrund des grossen Durchmessers meist Speichen in J-Bend-Form zum Einsatz.
Beim Einbau ist auch die Speichenlänge, die Flechtung und der Speichendurchmesser massgebend. Die Flechtung ist bei Stromer aufgrund des grossen Speichenwinkels 1-fach.
Aufgrund der Spoke breakage problem, empiehlt es sich Nippel mit 14 (statt 12mm) Länge, in Messing- bzw. Aluausführung ** und mit einem speziell gerundeten Nippelkopf zu verwenden. Mehr Details dazu finden sich here.
Bei vielen Nabenmotoren werden 14 Gauge (ø 2.0 mm) Speichen verwendet, was bei sauberer Einspeichung völlig ausreicht. Ändert man hier etwas muss das mit dem Lochdurchmesser der Speichenaufnahme im Motorflanch und der Felge korrespondieren. Entweder bohrt man die Löcher auf, verwendet U-Scheiben oder verwendet konifizierte Speichen, welche z.B. 13G (ø 2.3 mm) beim Motorflanch haben, danach aber auf 14G reduzieren um in der Felge zu passen. Letzteres ist bei meinem ST3 der Fall. Es werden sog. Single Butted Speichen verwendet.
The spoke length depends on the rim used, the motor dimensions and how the motor sits in the rear axle (Hub Shift *) and how it is positioned in relation to the center of the rim (Dishing Offset *). With Stromer, the rims are drilled symmetrically (right/left offset = 0 mm) and my ST3 has no hub shift.
The spoke tension must also be taken into account when spoking. Only uniform and correct spoke tension guarantees a stable rim. The spoke tension is determined, among other things, by the rim used. Its mechanical design determines how high the maximum spoke tension may be. Common values for S-Pedelec rims are 1100 - 1300 N. For the above-mentioned RYDE Andra 29 the manufacturer specifies a maximum value of 1400 N. With the DT Swiss H 612 und Rodi sind es 1200 N.
Here are the Calculation and the material used for my ST3:
- Motor: TDCM (specification TDCM IGH, but with 32 holes and 140 mm axle length)
- Rim: DT Swiss H 612, ERD*= 564 mm
- Spokes: Sapim Strong Spokes 13G/14G J-Bend Black, Single butted (from Custom Cut Spokes, Art. No. 41671)
Nipples: Sapim Polyax Brass Nipples - Black - 14g - 14mm (from Custom Cut Spokes, Art. No. 212-38656)
*/** Zusatzinformation
ERD= Effective Rin the Diameter
Dishing Offset= Impeller asymmetry (rim vs. hub).
Hub Shift= Frame asymmetry (axle vs. frame center).
Der Hub Shift verschiebt die Achsposition im Rahmen, das Dishing verschiebt die Felge auf der Achse. Beide arbeiten zusammen, um bei komplexen Antrieben (wie Nabenmotoren) ein funktionierendes System zu schaffen!
** Bei Felgen mit Aluminiumöse empfiehlt es sich Messing-Nippel zu verwenden da es a.) bei Aluminium-Nippel zu Kaltverschweissungen zwischen AL-Al kommen kann und b.) Messing korrosionsbeständiger und somit allwetter-tauglicher ist.
Links
Spoke calculator | GRIN Technologies [EN] for rear wheels with hub motor
Explanatory videos:
- 1 - How to use the spoke calculator for hub motors from ebikes.ca
- 2 - How to measure hubs and rims for perfect spoke lengths, wheel construction for e-bike hub motors
- 3 - How to mount a hub motor at home like a pro. The single-cross construction
There is a good basic article here von ‚bike-components.de‘. Wie der ERD genau und pragmatsich festgelegt wird erklärt die Webseite von Sheldon Brown here.
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