{"product_id":"s58-and-b48-gen-1-alternator-overrun-pulley","title":"S58 \/ B58 Gen 1 \/ B48 Alternator Overrun Pulley","description":"\u003cp\u003eAn Overrunning Alternator Pulley allows the alternator to freewheel when the engine is trying to decelerate rapidly. This has many benefits by temporarily reducing drivetrain inertia. It saves your crank balancer from trying to tear itself apart which is a common problem on these engines . It also has the same affect as a lightweight flywheel on upshifts and allows for more rapid shifts and less wear on the transmission clutches on a manual or auto Trans. On some engines it even makes it run smoother!  There is no downside to using it and it does not increase belt or alternator noise. See video at the bottom for an in depth explanation. \u003c\/p\u003e\n\u003cp\u003eThis part is also known as a OAD (Overrunning Alternator Pulley) or OWC (One-Way Clutch) Alternator Freewheel Pulley or a Dutch Pulley. It is not an OAD (Overrunning Alternator Decoupler) or IDP (Isolator Decoupler Pulley) which refer to pulleys with a one way clutch and torsional spring. The version we use does not have a torsion spring in it as that task is taken over by the crank balancer and belt tensioner. This simply allows the alternator to freewheel in the counter-clockwise direction and act as a solid pulley in the clockwise direction to assist with rapid engine speed changes in the deceleration direction. \u003c\/p\u003e\n\u003ch2\u003e\n\u003cstrong\u003eFITMENT:\u003c\/strong\u003e\u003cbr\u003e\n\u003c\/h2\u003e\n\u003cp\u003e\u003cem\u003eThe best way to guarantee fitment for this pulley is to check if your current alternator has a 24mm nut holding the stock pulley on.  If your original pulley has a small plastic cap or a 22mm nut then this is the wrong pulley for your car. \u003c\/em\u003e\u003c\/p\u003e\n\u003cp\u003eThe images shown of the part installed are on a B48 engine. \u003c\/p\u003e\n\u003cp\u003eThere is an incredible amount of crossover between models and engines and alternators so please verify your fitment by looking up your VIN at realoem.com and matching the alternator part number with what we listed below. Or email info@strommotorsports.com with your VIN and we are happy to assist! \u003c\/p\u003e\n\u003cp\u003eWe have provided a list of what we know it fits but its impossible to correlate them all. \u003c\/p\u003e\n\u003cp\u003eIn every case we can find so far if you have a Bosch brand alternator on a B48\/ B58\/ S58 then you have a 24mm nut and you would use this pulley. If you have a Denso brand alternator and a 22mm nut then you would use the \u003ca href=\"https:\/\/strommotorsports.com\/products\/b48-b58-alternator-overrun-pulley?utm_source=copyToPasteBoard\u0026amp;utm_medium=product-links\u0026amp;utm_content=web\" title=\"B48 \/ B58D Overrunning Alternator Pulley\"\u003e99.00177 Pulley\u003c\/a\u003e.\u003c\/p\u003e\n\u003cp\u003eIf your car already has an aftermarket alternator then there is no way to verify other than by checking the nut size.\u003c\/p\u003e\n\u003cstyle\u003e\n.sm-fit {\n  \/* Paragraph text size. Everything else is sized relative to this.\n     Use px (or pt) here, NOT rem — Dawn sets the root to 62.5%,\n     which shrinks any rem value to 62.5% of its intended size. *\/\n  --sm-body: 16px;\n  --sm-ink: #1c1f22;\n  --sm-ink-soft: #5b6167;\n  --sm-rule: #d8dbde;\n  --sm-fill: #f5f6f7;\n  --sm-yes: #2f6b3d;\n  --sm-no: #9a3324;\n  font-size: var(--sm-body);\n  font-family: inherit;\n  color: var(--sm-ink);\n  line-height: 1.5;\n  max-width: 1000px;\n  margin: 0 auto;\n}\n.sm-fit *, .sm-fit *::before, .sm-fit *::after { box-sizing: border-box; }\n\n.sm-fit p.sm-fit__intro {\n  font-size: var(--sm-body);\n  color: var(--sm-ink-soft);\n  margin: 0 0 1.75em;\n  max-width: 68ch;\n}\n.sm-fit p.sm-fit__intro strong { color: var(--sm-ink); font-weight: 600; }\n\n.sm-fit__block { margin-bottom: 2.5em; }\n.sm-fit__block:last-child { margin-bottom: 0; }\n\n.sm-fit__head {\n  display: flex;\n  align-items: baseline;\n  gap: 0.6em;\n  padding-bottom: 0.5em;\n  border-bottom: 2px solid var(--sm-ink);\n  margin-bottom: 0;\n}\n.sm-fit__title { font-size: calc(var(--sm-body) * 1.21); font-weight: 650; margin: 0; letter-spacing: -0.01em; }\n.sm-fit__sub { font-size: calc(var(--sm-body) * 0.89); color: var(--sm-ink-soft); }\n\n.sm-fit table {\n  width: 100%;\n  border-collapse: collapse;\n  font-size: calc(var(--sm-body) * 0.97);\n}\n.sm-fit th {\n  text-align: left;\n  font-weight: 700;\n  font-size: calc(var(--sm-body) * 0.86);\n  color: var(--sm-ink);\n  padding: 0.7em 0.85em;\n  border-bottom: 1px solid var(--sm-rule);\n  white-space: nowrap;\n}\n.sm-fit td {\n  padding: 0.95em 0.85em;\n  border-bottom: 1px solid var(--sm-rule);\n  vertical-align: top;\n}\n.sm-fit tbody tr:nth-child(even) td { background: var(--sm-fill); }\n\n.sm-fit__engine {\n  font-weight: 650;\n  white-space: nowrap;\n  border-left: 3px solid var(--sm-yes);\n  padding-left: 0.7em;\n}\n.sm-fit--no .sm-fit__engine { border-left-color: var(--sm-no); }\n\n.sm-fit__codes, .sm-fit__models {\n  margin: calc(var(--sm-body) * 0.44) 0 0;\n  padding: 0;\n  list-style: none;\n  font-weight: 400;\n}\n.sm-fit__codes li { font-weight: 600; white-space: nowrap; }\n.sm-fit__codes li.sm-fit__sublabel {\n  font-weight: 650;\n  margin-top: 0.55em;\n  padding-top: 0.45em;\n  border-top: 1px solid var(--sm-rule);\n}\n\n.sm-fit__pn {\n  font-family: ui-monospace, SFMono-Regular, \"SF Mono\", Menlo, Consolas, monospace;\n  font-size: calc(var(--sm-body) * 0.9);\n  font-variant-numeric: tabular-nums;\n  letter-spacing: 0.01em;\n  margin: calc(var(--sm-body) * 0.44) 0 0;\n  padding: 0;\n  list-style: none;\n}\n.sm-fit__pn li { white-space: nowrap; }\n\n\/* Identical line box for every list row, in absolute units, so the P\/N column\n   lines up with the engine codes despite using a smaller monospace font. *\/\n.sm-fit__codes li, .sm-fit__models li, .sm-fit__pn li {\n  line-height: calc(var(--sm-body) * 1.455);\n  padding: calc(var(--sm-body) * 0.097) 0;\n}\n\n\/* Invisible stand-in for the group name, so the lists start at the same height\n   in all three columns. Hidden on mobile, where the cells stack. *\/\n.sm-fit__spacer { display: block; }\n\n.sm-fit__note {\n  display: block;\n  font-size: calc(var(--sm-body) * 0.89);\n  color: var(--sm-ink-soft);\n  font-weight: 400;\n  white-space: normal;\n  margin-top: 0.45em;\n}\n\n.sm-fit__flag {\n  margin: 1.25em 0 0;\n  padding: 0.85em 1em;\n  background: var(--sm-fill);\n  border-left: 3px solid var(--sm-ink);\n  font-size: calc(var(--sm-body) * 0.95);\n}\n.sm-fit__flag p { margin: 0; }\n.sm-fit__flag p + p { margin-top: 0.5em; }\n\n.sm-fit a { color: inherit; text-decoration: underline; }\n\n@media (max-width: 640px) {\n  .sm-fit thead { display: none; }\n  .sm-fit table, .sm-fit tbody, .sm-fit tr, .sm-fit td { display: block; width: 100%; }\n  .sm-fit tr {\n    border-bottom: 1px solid var(--sm-rule);\n    padding: 0.9em 0;\n  }\n  .sm-fit tbody tr:nth-child(even) td { background: none; }\n  .sm-fit td {\n    border: 0;\n    padding: 0.2em 0 0.6em;\n  }\n  .sm-fit td::before {\n    content: attr(data-label);\n    display: block;\n    font-size: calc(var(--sm-body) * 0.76);\n    font-weight: 600;\n    color: var(--sm-ink-soft);\n    margin-bottom: 0.15em;\n  }\n  .sm-fit__engine {\n    font-size: calc(var(--sm-body) * 1.05);\n    border-left: 0;\n    padding-left: 0;\n    margin-bottom: 0.4em;\n  }\n  .sm-fit__engine::before { display: none; }\n  .sm-fit__pn li { white-space: normal; }\n  .sm-fit__spacer { display: none; }\n  .sm-fit__codes, .sm-fit__models, .sm-fit__pn { margin-top: 0.2em; }\n}\n\u003c\/style\u003e\n\u003cdiv class=\"sm-fit\"\u003e\n\u003cp class=\"sm-fit__intro\"\u003eThere are many variations of the correct alternator. If one of the part numbers below is called out for your car in RealOEM, this pulley will fit. \u003cstrong\u003eThis list is not comprehensive\u003c\/strong\u003e — there are far too many alternator variants to catalog, so the pulley may still fit your car even if your part number isn't listed here. Engine codes, alternator part numbers and example models are listed independently within each group; a part number is not tied to the specific engine code beside it.\u003c\/p\u003e\n\u003cdiv class=\"sm-fit__block\"\u003e\n\u003cdiv class=\"sm-fit__head\"\u003e\n\u003ch3 class=\"sm-fit__title\"\u003eConfirmed fitment\u003c\/h3\u003e\n\u003cspan class=\"sm-fit__sub\"\u003everified against these alternators\u003c\/span\u003e\n\u003c\/div\u003e\n\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth scope=\"col\"\u003eEngine\u003c\/th\u003e\n\u003cth scope=\"col\"\u003eAlternator P\/N\u003c\/th\u003e\n\u003cth scope=\"col\"\u003eExample models\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd class=\"sm-fit__engine\"\u003eB58 Gen 1\n\u003cul class=\"sm-fit__codes\"\u003e\n\u003cli\u003eB58\u003c\/li\u003e\n\u003cli\u003eB58B30A\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cspan class=\"sm-fit__spacer\"\u003e \u003c\/span\u003e\n\u003cul class=\"sm-fit__pn\"\u003e\n\u003cli\u003e12318614276\u003c\/li\u003e\n\u003cli\u003e12318614278\u003c\/li\u003e\n\u003cli\u003e12318571357\u003c\/li\u003e\n\u003cli\u003e12318571358\u003c\/li\u003e\n\u003cli\u003e12318635552\u003c\/li\u003e\n\u003cli\u003e12318635553\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cspan class=\"sm-fit__spacer\"\u003e \u003c\/span\u003e\n\u003cul class=\"sm-fit__models\"\u003e\n\u003cli\u003eF20 1 Series\u003c\/li\u003e\n\u003cli\u003eF22 2 Series\u003c\/li\u003e\n\u003cli\u003eF30 3 Series\u003c\/li\u003e\n\u003cli\u003eF32 4 Series\u003c\/li\u003e\n\u003cli\u003eG30 5 Series\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd class=\"sm-fit__engine\"\u003eS58\n\u003cul class=\"sm-fit__codes\"\u003e\n\u003cli\u003eS58T\u003c\/li\u003e\n\u003cli\u003eS58O\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cspan class=\"sm-fit__spacer\"\u003e \u003c\/span\u003e\n\u003cul class=\"sm-fit__pn\"\u003e\n\u003cli\u003e12318571358\u003c\/li\u003e\n\u003cli\u003e12318635553\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cspan class=\"sm-fit__spacer\"\u003e \u003c\/span\u003e\n\u003cul class=\"sm-fit__models\"\u003e\n\u003cli\u003eG87 M2\u003c\/li\u003e\n\u003cli\u003eG80 M3\u003c\/li\u003e\n\u003cli\u003eG82 M4\u003c\/li\u003e\n\u003cli\u003eG82 M4 GT4\u003c\/li\u003e\n\u003cli\u003eF97 X3M\u003c\/li\u003e\n\u003cli\u003eF97 X4M\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd class=\"sm-fit__engine\"\u003eOther\n\u003cul class=\"sm-fit__codes\"\u003e\n\u003cli\u003eB46 \/ B48 — G30 only\u003c\/li\u003e\n\u003cli\u003eB48M\u003c\/li\u003e\n\u003cli\u003eB48B16A\u003c\/li\u003e\n\u003cli\u003eB57\u003c\/li\u003e\n\u003cli\u003eB57O\u003c\/li\u003e\n\u003cli\u003eB57S\u003c\/li\u003e\n\u003cli\u003eB57R\u003c\/li\u003e\n\u003cli\u003eB57T\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cspan class=\"sm-fit__spacer\"\u003e \u003c\/span\u003e\n\u003cul class=\"sm-fit__pn\"\u003e\n\u003cli\u003e12318614276\u003c\/li\u003e\n\u003cli\u003e12318614278\u003c\/li\u003e\n\u003cli\u003e12318571357\u003c\/li\u003e\n\u003cli\u003e12318571358\u003c\/li\u003e\n\u003cli\u003e12318635552\u003c\/li\u003e\n\u003cli\u003e12318635553\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/td\u003e\n\u003ctd\u003e\n\u003cspan class=\"sm-fit__spacer\"\u003e \u003c\/span\u003e\n\u003cul class=\"sm-fit__models\"\u003e\n\u003cli\u003eG20 3 Series — 320i, 330d\u003c\/li\u003e\n\u003cli\u003eG30 5 Series\u003c\/li\u003e\n\u003cli\u003eG01 X3\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cp\u003eTHIS PART DOES NOT FIT (But we are working on parts for these):      \u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eGen 2 B58 and all B46\/ B48 Inline OTHER than in the G30 - for that part \u003ca href=\"https:\/\/strommotorsports.com\/products\/b48-b58-alternator-overrun-pulley?utm_source=copyToPasteBoard\u0026amp;utm_medium=product-links\u0026amp;utm_content=web\" title=\"B48 \/ B58D Overrunning Alternator Pulley\"\u003eClick Here\u003c\/a\u003e\n\u003c\/li\u003e\n\u003cli\u003eFirst Gen B46\/B48 and B36 in Mini \/ X1\/ X2. Example alternator part numbers are: 12319845487, 12317646814, 12317640875. The pulley on these alternators is very short and does not have a shaft spacing out the pulley as seen on the new part.   \u003c\/li\u003e\n\u003cli\u003eDoes not fit any car with a 48V alternator 12318490540 - also known as Mild Hybrid. \u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003e\u003cspan style=\"color: #2b00ff;\"\u003e\u003ca href=\"https:\/\/strommotorsports.com\/pages\/tech-docs\" title=\"Strom Installation Instructions\" style=\"color: #2b00ff;\" rel=\"noopener noreferrer\" target=\"_blank\"\u003eInstallation Instructions\u003c\/a\u003e\u003c\/span\u003e\u003c\/h2\u003e\n\u003cp\u003e\u003ciframe width=\"560\" height=\"315\" src=\"https:\/\/www.youtube.com\/embed\/8CyWxnVRf28?si=b-f4wcrPj9KNZrSt\" title=\"YouTube video player\"\u003e\u003c\/iframe\u003e\u003c\/p\u003e\n\u003ch2\u003e\u003cbr\u003e\u003c\/h2\u003e\n\u003cp\u003e \u003c\/p\u003e","brand":"STROM","offers":[{"title":"Default Title","offer_id":51296837992691,"sku":"99.00183","price":169.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0700\/9219\/4035\/files\/8019D2D8-B040-41D2-B536-1410827F755A.jpg?v=1789595043","url":"https:\/\/strommotorsports.com\/products\/s58-and-b48-gen-1-alternator-overrun-pulley","provider":"Strom Motorsports","version":"1.0","type":"link"}