High Performance Under drive Pulley Sets with Accessory Belt UUC

(No charge for shipping in the continental US) Ships out in Priority Mail Box, packed in bubble wrap, 2-3 business day delivery, insured with tracking. International rates and delivery vary depending on location.

Pulley Kit (easy bolt-on assembly - no special tools required):
  • Replaces Water Pump Pulley
  • Replaces Power Steering Pump Pulley
  • Replaces Accessory Belt



What's an Under Drive Pulley?

An underdrive pulley is a replacement accessory pulley that bolts up the same as stock, but has a different size (ratio) and material specifications intended to free up lost horsepower. By increasing the diameter of each accessory pulley, the speed at which the accessories are turning relative to engine RPM decreases.

Does this actually make horsepower?

Underdriving the accessories does not add power to the engine, it frees up the power that is normally wasted on overdriven accessories. The theory is that a larger pulley will drive the accessories slower thus reducing their parasitic horsepower loss. No more power total, but more power sent to the wheels. As an additional benefit, the reduction in wear (less usage) on the accessories due to the lower duty cycles can extend the life of these parts.

However, a look at each pulley-driven system under the hood will tell you why it isn't as simple as "just a bigger pulley".

Which accessories can I underdrive?

Of the four accessories that can be underdriven with a larger drive pulley, one is electrical (the alternator) and two are fluid pumps (the water pump and the power steering pump). The fourth is a compressor (the air conditioning unit).

UUC Motorwerks Ultimate Underdrive Pulley set provides replacement pulleys for the water pump, power and steering pump. Please see the "Technical Details" page for more information.

What abut the weight?

WARNING: Some companies have been marketing replicas of UUC's original pulley design, but advertising them as superior due to "light weight". This clearly shows these replica manufacturers do not have an understanding of the underdrive concept... weight reduction is not a factor in producing power with underdrive pulleys... the gain comes from reducing the accessory speed, not from less rotating mass.

While some pulley advertisers do advertise "lightest weight", we feel that to be somewhat deceptive... in our extensive testing, we have proven that the actual weight of the pulleys is not a factor in increasing power gains whatsoever. Each pulley itself weighs just a few ounces... shaving off a small amount of additional aluminum will not make one single bit of measurable power. Weight savings in a BMW that are important are in the much larger rotating components such as a lightened flywheel or lighter road wheels.

BMW has designed specific pulleys in the engine compartment to drive the alternator, water pump, power steering pump, and A/C compressor.

These accessories present a parasitic drag on the engine’s horsepower. One way to reclaim that hidden horsepower is to replace some of the pulleys with an “under-drive” pulley. I’m sure we’re all familiar with the term “over-drive”, a ratio smaller than 1:1 in the gearbox to achieve higher speed at a given RPM. Under-driving a pulley is the exact opposite. A larger diameter pulley is used so that the accessory will make fewer turns for every engine revolution, thus requiring less work from the engine, but also resulting in less work done by the accessory.


UUC’s Ultimate Underdrive Pulley kit comes with a replacement pulley for the water pump and the power steering pump. It comes with two aircraft quality machined pulleys anodized in silver or black, along with a replacement belt. The built quality of the kit is excellent, with flawless machining on the pulleys and a beautiful design.

UUC optioned for the black anodized pulley set to blend into the engine surround. Installation of the kit is about as simple as turning a few wrenches, especially on cars that does not come with a mechanical cooling fan. On models that come with the mechanical fan, you will need the fan clutch removal tool (a long, 32mm/36mm wrench). Other than that there isn’t really any special tools required to do this job. The bolts that hold down the water pump pulley are 10mm bolt, and the bolts that hold down the power steering pump pulley are 13mm. There are some simple rivets and screws you will need to remove if you intend to remove the electrical fan, to allow you additional access to the pulleys, and you will need a 16mm socket/wrench to turn the AC belt tensioner and a T50 Torx bit to turn the accessory belt tensioner.

Installation is as simple as remove belt, remove pulley, install new pulley, and install new belt. Entire procedure takes about 1 hour for a shady tree mechanic, including jacking up the car and all the prep work. UUC includes a detailed instruction set with pictures and easy to follow steps, which takes all the guesswork out of a DIY project.


Well, they say it’s almost impossible to feel any performance improvement under 10% by the seat of the pants. UUC proclaims a 4hp-11hp increase measured at the drive wheel, which for most modern BMWs is a less than 10% increase.

Despite the moderate claims, there are tangible benefits to the pulley kit that you CAN feel. One of the most immediate results of installing the pulley kit is better engine response to throttle input. As best as I can describe it, it feels like the engine is “lighter”, or that it’s got less drag on it. The most obvious evidence of this is when you are engine-braking. There’s less drag on the engine and it takes longer for the car to slow-down. I’ve noticed a small increase of about 0.5 miles to a gallon since my last fill-up. Another benefit seems to be when I’m executing heel-toe downshifts. Since the engine seems more willing to rev up, I find it easier to control my blips to match the revs.


This is one of the more affordable and safe modifications you can make to your engine. Since the UUC kit does not under-drive the main crankshaft pulley, which acts as the harmonic dampener for the inline 6 engines, and it does not under-drive the alternator, it eliminates two of the sources for possible problems down the road. Some kits that under-drives the alternator may result in dropped voltage to drive in-car electronics, or alternator interference that decreases the performance of your FM and AM reception. And since the kit is so easy to install, if you’re familiar with changing the oil in your car and have the proper tools you should be able to perform this modification yourself. Best of all, it is certainly one of the most affordable modifications you can make to your car at this price point.

(No charge for shipping in the continental US with minimum $25 order) Ships out in Priority Mail Box, packed in bubble wrap, 2-3 business day delivery, insured with tracking. International rates and delivery vary depending on location.

RETURN Policy: 100 Days to Return for Money Back or Exchange. For our more detailed policy information: kinobilighting.com/policy.html

Questions? Contact us...

  • Vehicles & Parts: accessory pulley
  • Item #: UUC-UDP
  • Manufacturer: UUC Motorwerks: Underground Upgrade Club (Authorized Reseller)
  • Condition: New

Pulley Sets with Accessory Belt - High Performance - Under Drive

Price: $279.99
Availability: Out-of-Stock
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