[{"data":1,"prerenderedAt":317},["ShallowReactive",2],{"radtype-en-mountain-bike":3,"radtype-eval-mtb":247},{"id":4,"title":5,"applies_to":6,"author":8,"body":9,"confidence":227,"description":228,"extension":229,"faq":230,"meta":231,"navigation":232,"path":233,"seo":234,"sources":235,"stem":242,"test_bike":243,"topic":244,"updated":245,"__hash__":246},"content_en\u002Fen\u002Frad-typen\u002Fmountain-bike.md","Converting a Mountain Bike to an E-Bike",[7],"all","fabio-gentsch",{"type":10,"value":11,"toc":215},"minimark",[12,16,21,24,28,80,83,87,98,104,110,116,127,131,138,142,179,183,190,194,202,206,209],[13,14,15],"p",{},"A modern mountain bike with thru-axles can usually only be converted with a mid-drive. Hub motors are built for quick-release axles at 100 and 135 mm, while your bike probably has 15 × 110 at the front and 12 × 148 at the rear. A mid-drive does not care about that, because it sits at the bottom bracket.",[17,18,20],"h2",{"id":19},"what-makes-a-mountain-bike","What makes a mountain bike",[13,22,23],{},"Typical features are an aluminium hardtail, a suspension fork, hydraulic disc brakes, an 11- or 12-speed derailleur and thru-axles (Boost: 110 mm at the front, 148 mm at the rear). Wheels are 27.5\" (ETRTO 584) or 29\" (622). Our example bike: aluminium hardtail, 29\", 13 kg, 73 mm BSA bottom bracket, 420 mm down tube.",[17,25,27],{"id":26},"what-usually-works","What usually works",[29,30,31,45,62,68],"ul",{},[32,33,34,38,39,44],"li",{},[35,36,37],"strong",{},"Disc brakes:"," a good basis for the extra weight. With hydraulic brakes the motor cut-off is usually a magnetic sensor at the lever, see ",[40,41,43],"a",{"href":42},"\u002Fen\u002Fknowledge\u002Fbrakes","Brakes",".",[32,46,47,50,51,57,58,44],{},[35,48,49],{},"Bottom bracket:"," Bafang BBS and Tongsheng TSDZ fit BSA 68 to 73 mm (",[40,52,56],{"href":53,"rel":54},"https:\u002F\u002Ffasterbikes.eu\u002Fen\u002Fconfigurators\u002F",[55],"nofollow","fasterbikes","). With press-fit (BB86\u002FBB92) you need adapters, see ",[40,59,61],{"href":60},"\u002Fen\u002Fknowledge\u002Fmeasure-bottom-bracket","Measure the bottom bracket",[32,63,64,67],{},[35,65,66],{},"Aluminium frame:"," suitable; carbon is not.",[32,69,70,73,74,79],{},[35,71,72],{},"Hills:"," the example bike is meant to manage 600 m of climbing a day. A mid-drive is the right choice for that, and Upway calls it strong on hills (",[40,75,78],{"href":76,"rel":77},"https:\u002F\u002Fupway.de\u002Fblogs\u002Fnews\u002Ffahrrad-zum-e-bike-umbauen",[55],"Upway",").",[13,81,82],{},"For the example bike the configurator rates the mid-drive green, and the verdict is \"convert\".",[17,84,86],{"id":85},"what-it-fails-on","What it fails on",[13,88,89,92,93,97],{},[35,90,91],{},"Thru-axles."," Standard hub motors need 135 mm at the rear (quick release) and 100 mm at the front. At 148 mm at the rear the configurator finds no matching rear motor, so the rear motor is red. At the front there are special motors, see ",[40,94,96],{"href":95},"\u002Fen\u002Fknowledge\u002Fhub-spacing","Hub spacing",". That is an assumption Fabio is still checking.",[13,99,100,103],{},[35,101,102],{},"Suspension fork."," A front motor in a suspension fork is not a good idea without the manufacturer's approval. It puts extra load on the fork, and the disc mount has to match the motor. The configurator rates the front motor yellow for the example bike.",[13,105,106,109],{},[35,107,108],{},"Traction."," On gravel and forest tracks a front motor gives less grip.",[13,111,112,115],{},[35,113,114],{},"Friction drive."," It has little power and suits hills badly. The configurator rates it yellow for the example bike.",[13,117,118,121,122,126],{},[35,119,120],{},"Room in the frame."," Many MTB frames have short down tubes or bottle-cage mounts where the battery is supposed to go. The battery often needs 35 to 45 cm, which is a rule of thumb, see ",[40,123,125],{"href":124},"\u002Fen\u002Fknowledge\u002Fbattery","Battery",". With a mid-drive, the chainline and the chainstay are tight, and a front derailleur usually goes.",[17,128,130],{"id":129},"which-motor-type-fits","Which motor type fits",[13,132,133,134,44],{},"Mid-drive, with a clear reason: it needs no wheel hub, it uses your gears and it gives power on hills. The price: more work to fit, more wear on chain and sprockets, and you should not shift under full load. The example bike has 12 speeds, which matters for chain care. The comparison: ",[40,135,137],{"href":136},"\u002Fen\u002Fknowledge\u002Fmid-drive-vs-hub-motor","Mid-drive vs hub motor",[17,139,141],{"id":140},"what-to-measure-first","What to measure first",[143,144,145,153,161,169],"ol",{},[32,146,147,150,151,44],{},[35,148,149],{},"Bottom bracket shell"," (width and type), see ",[40,152,61],{"href":60},[32,154,155,158,159,44],{},[35,156,157],{},"Hub spacing and axle standard"," at the front and rear, see ",[40,160,96],{"href":95},[32,162,163,166,167,44],{},[35,164,165],{},"Frame triangle"," for the battery, see ",[40,168,125],{"href":124},[32,170,171,174,175,44],{},[35,172,173],{},"Total weight"," with rider and luggage, see ",[40,176,178],{"href":177},"\u002Fen\u002Fknowledge\u002Fframe-and-weight","Frame and weight",[17,180,182],{"id":181},"the-law-in-short","The law in short",[13,184,185,186,44],{},"Pedelec means: at most 250 W rated continuous power, assistance only while you pedal, up to 25 km\u002Fh. A throttle is only allowed as a walking aid up to 6 km\u002Fh, above that it is a motor vehicle. See ",[40,187,189],{"href":188},"\u002Fen\u002Fknowledge\u002Fpedelec-law","Pedelec law",[17,191,193],{"id":192},"when-you-should-leave-it","When you should leave it",[13,195,196,197,79],{},"Leave it if your MTB has a carbon frame, or is a full-suspension bike whose shock gets in the motor's way. With a bottom bracket shell that does not suit a mid-drive, or a bike with a high-end drivetrain you do not want to wear out, a ready-made e-MTB is often the better solution. The manufacturer's warranty mostly lapses, and some workshops refuse conversions (",[40,198,201],{"href":199,"rel":200},"https:\u002F\u002Ffahrrad-xxl.at\u002Fblog\u002Fe-bike-umbausatz",[55],"Fahrrad XXL",[17,203,205],{"id":204},"how-sure-is-this","How sure is this?",[13,207,208],{},"There are sources for mid-drives fitting BSA 68 to 73 mm and for workshops refusing conversions. That thru-axles rule out hub motors and that a suspension fork with a front motor causes problems is an assumption Fabio is still checking. The assessment of the example bike comes from our configurator.",[13,210,211],{},[40,212,214],{"href":213},"\u002Fen\u002Fconfigurator","Does a conversion fit your bike?",{"title":216,"searchDepth":217,"depth":217,"links":218},"",2,[219,220,221,222,223,224,225,226],{"id":19,"depth":217,"text":20},{"id":26,"depth":217,"text":27},{"id":85,"depth":217,"text":86},{"id":129,"depth":217,"text":130},{"id":140,"depth":217,"text":141},{"id":181,"depth":217,"text":182},{"id":192,"depth":217,"text":193},{"id":204,"depth":217,"text":205},"assumption","MTB with thru-axles, suspension fork and disc brakes: why usually only a mid-drive fits, what to measure and when to leave it.","md",null,{},true,"\u002Fen\u002Frad-typen\u002Fmountain-bike",{"title":5,"description":228},[236,238,240],{"title":237,"url":199},"Fahrrad XXL: e-bike conversion kit (German)",{"title":239,"url":76},"Upway: convert a bike to an e-bike (German)",{"title":241,"url":53},"fasterbikes: configurators","en\u002Frad-typen\u002Fmountain-bike","mtb-steckachse","mtb","2026-11-09","ubHnKkqIm2K8VwmfiHxJvVE9FQA6Y0HAQQHWTXN225U",{"name":248,"profile":251,"recommended":272,"verdict":273,"motors":274,"top":300},{"de":249,"en":250},"Alu-Hardtail mit Steckachsen (Boost)","Aluminium hardtail with thru-axles (Boost)",{"goal":252,"daily_km":253,"elevation_m":254,"budget_eur":255,"frame_type":256,"frame_material":257,"wheel_etrto":258,"front_spacing_mm":259,"rear_spacing_mm":260,"front_axle":261,"rear_axle":262,"bb_shell":263,"brakes":264,"drivetrain":265,"rear_cogs":266,"suspension_fork":232,"battery_space":267,"downtube_length_mm":268,"max_total_weight_kg":269,"rider_weight_kg":270,"bike_weight_kg":271},"hills",25,600,1200,"mtb_hardtail","aluminium",622,110,148,"thru_15","thru_12","bsa_73","disc_hydraulic","derailleur",12,"downtube",420,130,85,13,"mid","convert",[275,277,285,292],{"mt":272,"status":276,"finding":230},"green",{"mt":278,"status":279,"finding":280},"friction","yellow",{"rule":281,"status":279,"message":282,"fix":230},"friction-low-power",{"de":283,"en":284},"Reibrollen haben wenig Kraft und rutschen bei Nässe: für Berge und Lasten eher schwach.","Friction drives have little power and slip in the wet: weak for hills and loads.",{"mt":286,"status":279,"finding":287},"front_hub",{"rule":288,"status":279,"message":289,"fix":230},"suspension-fork-front",{"de":290,"en":291},"Frontmotor in einer Federgabel nur mit Freigabe des Gabelherstellers.","A front motor in a suspension fork only with the fork maker's approval.",{"mt":293,"status":294,"finding":295},"rear_hub","red",{"rule":296,"status":294,"message":297,"fix":230},"no-matching-kit",{"de":298,"en":299},"Für dein Rad passt keines der Kits dieser Motorart aus unserer Datenbank.","None of the kits of this motor type in our database fits your bike.",[301,307,312],{"rule":302,"status":303,"message":304,"fix":230},"mid-chain-wear","info",{"de":305,"en":306},"Mittelmotoren fressen Ketten: E-Bike-Kette nehmen und nicht unter Volllast schalten.","Mid-drives eat chains: use an e-bike chain and don't shift under full load.",{"rule":308,"status":303,"message":309,"fix":230},"warranty-lost",{"de":310,"en":311},"Die Gewährleistung des Fahrradherstellers entfällt nach dem Umbau meist.","The bike maker's warranty usually ends after the conversion.",{"rule":313,"status":303,"message":314,"fix":230},"worn-parts-first",{"de":315,"en":316},"Verschlissene Teile (Kette, Bremsbeläge, Reifen) vor dem Umbau erneuern.","Replace worn parts (chain, brake pads, tyres) before the conversion.",1794249628641]