Club Car Clutch Testing Results
Anyone who has paid attention to our Club Car product offerings over the last couple years may have noticed several different clutching options. During the pandemic, there was a major supply chain constraint and we had to adapt to what we had to work with. This meant that we were forced to do further R&D in order to maintain our ability to offer kits for Club Cars.
In short, we tested every feasible clutching option for 1984 and later Club Cars that we could find. We used the same golf cart and driver for that testing to minimize inconsistencies. Below are the results of that testing:
(The cart is a 1999 Club Car DS w/670 Predator, 4" lift, 23" Tires & Stock Gearing)
Comet 780 Primary (1-3/16") and CVTech INVANCE Secondary
This was the standard offering for many years (Approx. 2013-2021). While this was a nice clean option that was bolt on and looked great, it was very costly and the clutch compatibility wasn't the best. The 780 and the INVANCE work together but not as well as they could. Since there is a space constraint on Club Cars, it was the best we could do at the time with what we had.
Top Speed : 32.7mph
Subjective Drivability : 7/10
Subjective Acceleration : 7/10
Overall Score: 7/10
Notes: This is overall a very good setup but it does lack acceleration from a stop. It gives the feeling of belt slip right off the line and you can tell theres more in it. It is harder to shift F-R when the engine is running because the 780 does not have an internal idler bearing.
Comet 780 Primary (1-3/16") and Comet 790 Secondary
This was the very first setup we tested and the biggest issue is that it doesn't fit any 1997 or newer Club Cars because of the way the clutch cup interferes with the inside the transaxle casting. Additionally, it sticks out too far on the 1984-1991 Club Cars so much that the Primary hits the frame when the clutches are aligned.
For the above reasons, we had to machine the clutch cup down in order to force fit it inside the transaxle. This weakened the clutch and we do not recommend doing this.
Top Speed : 32.3 mph
Subjective Drivability : 7/10
Subjective Acceleration : 3/10
Overall Score: 4/10
Notes: The secondary clutch needs a stronger spring as the belt slip is significant on the low end. The speed was similar to the CVTech but because of the fitment issues..its a hard pass in our book.
Comet 780 Primary (1-3/16") and Tuned OEM Secondary w/.28" Spacer
This was a cool idea that we discovered while reading a BGW thread. We disassembled a Club Car secondary that we had, took some measurements and made a quick CNC program on a lathe to cut out a .28" spacer which gave us the exact opening dimension of the CVTech clutch.
Top Speed : 27.5mph
Subjective Drivability : 6/10
Subjective Acceleration : 8/10
Overall Score: 2/10
Notes : I had high hopes for this setup but it proved to be a bad idea. The spacer reduced the secondary clutches travel and its ability to open fully. This meant that the primary clutch couldn't do its job and open fully either. This killed speed significantly and left a distinct rubber ring on the primary clutch from the heat buildup. A great way to kill belts and clutches. We did notice better acceleration than the CVTech but similar F-R shifting issues.
This setup was so bad that we made a quick video of the clutches so you can see how they are only opening about 60%-70% at full throttle:
Comet 780 Primary (15/16") and Tuned OEM Secondary
This setup worked out the best for the 1984-1991 carts because using a Taper Adapter and cutting the engines shaft down is just not an attractive option for most people. Besides voiding the engine warranty, its rather difficult to cut the shaft down and re-tap it for most DIYers.
Top Speed : 33mph
Subjective Drivability : 8/10
Subjective Acceleration : 8/10
Overall Score: 8/10
Notes: The only downside to this setup is the 780 clutch that has been modified to use a 15/16" clutch still doesnt have an idler bearing so shifting is alittle rougher than using the OEM Primary, but it gets the job done and is close as you're going to get to an OEM Primary.
Tuned OEM Primary & Secondary using a Custom 15/16" Belt:
Initially I discounted this setup as I figured the stock clutches were too small, but they were ideal in the sense that they were plentiful and would mean a huge costs savings to our customers. It took awhile to have a custom belt made but it turned out to be the best R&D decision of 2021.
Top Speed : 37.7mph
Subjective Drivability : 9/10
Subjective Acceleration : 9/10
Overall Score: 9.5/10
Notes: The drivability was unmatched with improved torque, throttle response and speed. Acceleration was on point because we were able to try 3 different springs and pick the one that worked the best to prevent belt slip on acceleration. There are many other key benefits to this setup:
1. The center bearing inside the factory primary that allows for much easier shifting from F-R as the belt has little friction on it when the engine is idling.
2. The clutches are a matched set and they are 100% compatible.
3. The smaller clutches provide the most amount of clearance and no clutch to frame contact.
4. G-Boost Technology sells many different springs for them so they can be fine tuned much better than any aftermarket clutch.
I wish we had spent more time in the early days testing the OEM clutches instead of passing them off as undesirable because they were small and inconvenient to work with due to their tapered input shaft.
As I write this 1.5 years later, I can say with confidence that they are reliable as well. Our shop cart gets driven like it was stolen on a daily basis and its yet to have a clutch problem.
There was talk about the thinner belt potentially being a downside but we have kept an eye on it and taken a heat measurement after running the cart hard (it runs cooler than the thicker 1-3/16" belt did with the CVTech secondary). To be safe, we had the custom belts made from a harder grade of rubber and added heat ribs to them. The reality is that the surface area on both belts is the same and the extra width doesn't have any noticeable affect on performance or longevity, despite looking anemic.