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If you own an M57-equipped BMW, you already know this twin-turbo diesel powerplant is an absolute torque monster. What you might also know is that all that low-end grunt and high-compression diesel vibration wreaks absolute havoc on your accessory drive system.
From the factory, both the E90 335d and E70 X5 35d utilize a rigid alternator pulley. With each cylinder's fire, the crankshaft experiences a violent micro-acceleration. Because the alternator has a heavy internal rotor spinning at high speeds, it wants to keep spinning at a constant rate. When the engine suddenly slows down (even minutely between firing cycles), the alternator fights the belt. This constant tug-of-war results in extreme stress on your engine's belt-driven components. At best, it’s an annoying, unrefined chirp at idle; at worst, it’s a ticking time bomb for your expensive harmonic balancer.
To solve this issue, many enthusiasts choose to run a clutched alternator pulley (also called an overrunning alternator pulley). A clutched pulley allows the alternator to "freewheel" or coast when the engine slows down, completely isolating its rotational inertia from the belt drive to prevent component wear. While the N52's clutched pulley (12317560483) is a straight bolt-on, the offset is incorrect for the E90 335d's accessory drive. This simple, zinc-coated spacer from Turner Motorsport provides the precise amount of spacing needed to perfectly align the new pulley with existing belt drive components.
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Products are warrantied by their manufacturer. Eurosport Performance is an authorized reseller: every part we sell is covered by the manufacturer's own warranty, with its own terms and duration. Claims go through us, so you deal with Eurosport Performance rather than a form on the brand's site, but whether a claim is accepted is the manufacturer's decision.
Manufacturer terms apply Duration and coverage are set by the brand and differ from one to the next: some cover one year, some a lifetime, some only the original purchaser. The brand's warranty page is the reference; ask us if you cannot find it. | We file the claim for you Contact us with your order number, photos and a description of the issue. We open the claim with the manufacturer, follow it up, and arrange the repair, replacement or credit they approve. The manufacturer decides whether the claim is accepted. |
Fitment guarantee: North America only We guarantee fitment for vehicles sold in the North American market. Vehicles from other markets are out of scope; specifications differ, and it is the customer's responsibility to confirm compatibility before ordering. | No warranty on tuning files ECU and TCU tunes and other software files are sold without warranty and are not returnable once delivered or flashed. Tuning can affect your vehicle's factory warranty; please read the brand's terms before purchasing. |
Proof of purchase Your Eurosport Performance order is the proof of purchase every manufacturer asks for. Keep the order confirmation; it is also in your account on the site and in the SPECD app. | What is usually not covered Damage from improper installation, modification, abuse, racing or an incorrect application for the vehicle, and normal wear items such as pads, clutch discs and filters. Shipping and labour are covered only when the manufacturer's terms say so. |
It is the manufacturer's warranty for that product. Where the brand publishes it, we note it in the description; otherwise contact us before ordering and we will confirm the exact terms with them.
Stop using it if it is a safety-related part, then contact us with your order number, clear photos, and when and how the issue appeared. Do not return anything until we confirm the claim; manufacturers often require an inspection or an authorization number first.
The manufacturer. We prepare and submit the claim, provide the proof of purchase and push for a fair outcome, but acceptance, replacement or credit is their call under their terms. We pass their decision on to you as soon as we have it.
It depends on the manufacturer. Simple cases are approved in days; claims that need the part inspected can take a few weeks. We keep you updated at each step and push when it drags.
No. Tuning files are software; once delivered or flashed they cannot be returned, and they carry no warranty from Eurosport Performance or, in most cases, from the tuner. Support for the tune itself (revisions, flashing questions) comes from the tuning brand under its own terms.
No. Our fitment guarantee covers vehicles sold in the North American market only. European, Japanese and other market vehicles can differ in engines, electronics and dimensions, and a part listed for the North American model is not guaranteed to fit. If you order for one of these vehicles, confirming compatibility is your responsibility, and fitment issues on such vehicles are not covered by returns or warranty.
Labour is not covered unless the manufacturer's terms specifically include it. Having the part installed by a qualified shop protects your claim: improper installation is the most common reason a manufacturer declines.
No. Returns cover unused parts you no longer want, under our refund policy. Warranty covers a part that fails in use, under the manufacturer's terms. If you are unsure which applies, contact us and we will point you to the right one; please do not open a bank dispute, as it pauses both processes.
Questions about coverage before you buy? Email us with the product and your vehicle and we will confirm the manufacturer's terms.

