1. Mid-rim Area (Rim Height 35~55mm)
As of 2024, a standard mid-rim with a 50mm rim height would be considered quite light at around 400g. For wheelsets, around 1,300g was thought to be a really lightweight product. However, nowadays, not just Chinese brands but also major manufacturers are putting in considerably more effort into weight reduction than before. Enve's SES Pro 4.5 (front 49mm) and Reserve 49SL show very light weights of 369g and 385g respectively. Of course, Chinese brands are going even further, with Nextie's Alpha 50 and LightBicycle's Airia 52 showing a standard weight of 330g, which is almost unbelievably light. Domestically, Wheellab's Olta50 carbon rim is said to be 365g, which is almost the same level as the Enve SES Pro 4.5 in terms of weight.
With these rims, when combined with one of the very light hubs like Nonplus's Primaro and lightweight steel aero spokes, you can expect weights in the 1,090g ~ 1,190g range. Of course, using carbon spokes allows for further weight reduction, and combining with an H-work HX hub and lightweight carbon spokes around 2.0g makes weights around 970g possible. (Though I don't recommend carbon spokes around 2.0g as their stiffness is too low.)
2. High-rim Area (Rim Height 60mm or Higher)
Though this is a field where weight reduction requirements are relatively lower, I was pleasantly surprised to see that PrincetonCarbonWorks (PCW)'s WAKE 6560 EVO V2 was lighter than expected. Though it does use a Tactic hub that weighs the same as the ultralight Nonplus and Alpina Hyperlite Aero spokes, the wheelset showed a measured weight of about 1,244g with a 65mm rim height, which is quite impressive. Based on my previous building experience, calculating the rim weight resulted in approximately 415g, which is very light for its rim height.
This is nearly the lightest 65mm carbon rim I know of, and at the level of LightBicycle's Airia 65 ultralight option (400g), it's among the lightest rims currently available. While weight varies by material and its impact is less significant for high rims, it's a weight that raises concerns about stiffness. Reserve also added an SL option while doing a complete renewal of their Tubulent Aero models, but given that their lightweight 64mm rim is 495g, the wheelset weight difference is over 160g, which shows that PCW's rim weight reduction was quite aggressive.
3. Low-rim Area (Rim Height 35mm or Lower)
For domestic riders, a 50mm rim height is the standard, but typically even at 30mm the difference in aerodynamic performance isn't that significant. Of course, it depends on how much importance you place on watts, but in reality low rims are a very unpopular category domestically. However, lowering the height does provide several advantages. You can expect weight savings and improved ride quality as spoke length increases. Anyway, in the low-rim area, combining with Nextie Alpha 28 you can expect weights around 960g for steel spokes and 840~850g for carbon spokes. However, if you want stiffness, I think it would be better to build with a height of about 35mm at around 950g per wheelset.
4. Ultra-light Carbon Rim Trendline
I simply created a linear equation, and with the formula below it seems to be almost the ultralight limit for rim weight relative to rim height. (h is rim height (mm), W is rim weight according to rim height (gram))
The trendline equation plotted above (red line) shows approximately 260g at 30mm, 340g at 50mm, and 380g at 60mm, indicating a weight change of about 40g per 10mm. The correlation with products recorded in the actual chart above also seems to match roughly, except for very high rims (around 80mm). Roughly speaking, if it's below that trendline, it's an extremely lightweight carbon rim.
Additionally, the green trendline is the ultralight rim trendline as of 2024. It represents the carbon rim weight of products like Pasports Feder or Hyper from that time, but now you can see that even major brands like Enve and Reserve are generally lighter than the 2024 ultralight rim standard.
5. Ultra-light Wheelset Standards
Let me roughly calculate ultra-light wheelset weights considering the carbon rim weights above.
Roughly speaking, at 50mm you can expect weights around 970 ~ 1,110g depending on spoke type. Personally, I've built the bolded wheelsets at around 890g for 30mm rim height and around 1,010g for 50mm rim height, and they are really light. However, many report that unless using the Nonplus + Ultralight combination, the above combinations lack stiffness. If stiffness is needed, you could consider options like increasing rear wheel rim weight or using slightly heavier spokes.
6. Future Outlook and Miscellaneous Thoughts
- Carbon Rim Hub Weight Reduction: Considering that Nonplus's M4/T-head hub (24-hole) has already been released or is planned, carbon spoke hubs with 20 holes seem to have about 15~20g of weight reduction potential.
- Major Brand Rim Weight Reduction: Looking at the prominently featured Enve SES Pro 4.5 and PCW WAKE 6560 EVO V2, it seems the weight has come down quite a bit, but brands like Reserve, Zipp, Roval, and DT SWISS seem to still have some room for further rim weight reduction.
- Carbon Spoke Weight Reduction seems difficult unless the Tapered End method changes to a different method. Carbon spokes in the 2.0g range already have such low stiffness that many report them as too flexy, and since the end material is titanium, it's difficult to apply lighter metallic materials.
In conclusion, with the current carbon spoke structure and carbon rim production methods, it seems difficult to meaningfully reduce weight unless there is innovation in materials. Moreover, since the thru-axle diameter and length also have no further room to be reduced in disc brake bicycle systems, there's almost no possibility of weight reduction from external factors.
