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| Sometimes Single Is Better
As we mentioned before, the number of manual transmission drivers on the road decreases every year. We, the preservationists of the third pedal, are more dedicated than ever to rowing our own gears. Last week, we took a closer look at the new Turner Motorsport Double Adjustable Ultimate Short Shift Kit and how it can help improve your driving experience with your manual transmission BMW. This week, we’re going to talk about a related subject, one that BMW drivers who insist on the do-it-yourself gearbox should highly consider. We are of course referring to the clutch and flywheel that allow you to put your power to the ground when you release that ever-important third pedal.
You may remember an older article where we spoke specifically about how a clutch works and looked at the multiple types of clutches, flywheels, and kits available for your BMW. Today, we’re going to focus more on what we think is the best way for the majority of BMW drivers to transmit the power from their engine to the wheels. Of course, clutches and flywheels are varied in style and purpose, so this may not apply to those of you who strictly want factory operation or need something aggressive for high horsepower and competitive use. However, if you have a stock or modified BMW with a manual transmission and want something more engaging than the factory equipment, this is for you.
First, let’s do a bit of refreshing. The manual transmission uses a flywheel, friction disc, and a pressure plate to allow the engine rotation to be sent to the driveline. The flywheel provides continuous motion from the engine and a friction surface to meet the clutch disc, the clutch disc is pressed into the flywheel by the pressure plate when the clutch pedal is released and pulls it away from the flywheel when the pedal is depressed. You probably knew that already since you read the Keys to Performance Clutch Upgrade Guide.
You may also have seen some of the upgrade options like lightweight flywheels, puck-type clutch discs, multi-disc kits, and more. However, if your BMW is a daily driver or only needs something to hold up to a few modifications, you probably have a few questions as to how aggressive a setup you need.
For daily driving, you won’t want something that has an overly stiff pedal feel or on-off engagement. The feel of a racing clutch, especially an unsprung clutch, will be too aggressive to drive easily on the street. Thankfully, finding a happy Goldilocks zone is fairly easy. Really, what you should consider comes down to how much horsepower/torque you have and how fast you want your engine to rise and fall in revs. |
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This all comes down to the disc itself and the flywheel. Most BMWs are equipped with a dual-mass flywheel and fairly tame clutch. The dual-mass flywheel cuts down on vibration, but it adds rotational mass which increases the response time when you hit the throttle. An easily daily-driven option would be to upgrade to a single-mass flywheel. There may be more gear rollover noise, but you will experience reduced weight for better engine response and will save money over a dual-mass version. The single-mass flywheel conversion clutch kit is our suggestion for anyone looking for improved performance without making too many sacrifices.
For the clutch disc, you need to take into account your horsepower. Clutch discs are rated to certain horsepower outputs, but you don’t want to run right up to their capabilities. For instance, if you have a 300hp BMW, a clutch rated to 300hp will not be sufficient. The idea is that we want to prevent slipping the clutch so we can put all our power to the ground. So you will want something that can withstand your power, but you don’t want to go too aggressive either.
Since this is for street driven applications, we suggest a sprung clutch. You can still upgrade to a disc capable of supporting your HP/Torque output, but won’t have to sacrifice pedal stiffness in the process. We also suggest for moderately upgraded BMWs to stick with a full-face type clutch disc, as it won’t be too grabby for street driving. While a puck-type can be beneficial for high-horsepower applications, they tend to be harder to drive on the street and do not last as long due to the reduced surface area. For the longest life, best pedal feel, and appropriate power rating, an upgraded full-face, sprung, clutch disc is your best bet. |
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| Fortunately, we have put together kits with all this in mind for you. All you have to do is install the kit and you’re ready to put all your power to the ground. With a single-mass flywheel improving the response time and saving you money, a clutch disc capable of transmitting all your power effectively, and an appropriate pressure plate for the assembly, your BMW will feel and perform the way you want. |
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| Additionally, we suggest making a few upgrades while you are in there replacing the clutch assembly. By using a Brass Pivot Pin instead of the OEM plastic pin, you can ensure that you will never lose pedal feel or need to replace the pin ever again. This is honestly a must for any BMW manual transmission. There is no reason you should use a plastic pivot pin you will need to replace or that wears down over time, just get the brass one and never worry about it again. |
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Lastly, an upgraded stainless steel clutch line from the master to the slave cylinder will help improve overall pedal feel. The tighter feel makes your pedal more engaging and arguably better to drive, plus the line is more durable than the OEM rubber version that eventually needs to be replaced. We highly recommend you make this upgrade as well the next time you service your clutch.
So, armed with a bit of information, you should feel confident in your knowledge of what to do for your BMW to put all its power to the ground, especially if you have made significant changes to the power output of your engine. With an upgraded clutch assembly that is still daily drivable, you will enjoy a more engaging driving experience and won’t need to worry about losing power to a slipping clutch. Now go out there and make your BMW all that you’ve always wanted it to be with a single-mass conversion kit and upgraded clutch disc! |
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