Bike weights - aluminum vs carbon frames
 

I've never considered myself a weight weenie. That said, I recently bought a Cannondale SuperX and it feels a bit heavy to me. It's a carbon frame CX race bike with hydro disc brakes and Shimano GRX 1x drivetrain. The drivetrain is a mix of GRX600 and 800. I love the bike, it's fast and smooth and soaks up rough terrain. I've had it for a few months and haven't touched my old bike since getting it. Yesterday I was moving stuff around in my garage and picked up my old bike, which is an aluminum Cannondale CAADX with cantilever brakes and it definitely felt a little lighter when picking it up. I've never weighed my bikes before, so out of curiosity, I decided to weigh the two by standing on the bathroom scale with each, and then subtracting my own weight:

56cm SuperX with GRX 1x, disc brakes, stock aluminum wheels, 33mm tires/tubes, 2 bottle cages and XTR pedals = 20.3lbs
56cm CAADX with Force 1x, cantilever brakes, carbon clincher wheels, 33mm tires/tubes, 2 bottle cages and XT pedals = 18.7lbs

So my new $3000 carbon race bike is 1.6lb (around 725g) heavier than a 7 year old aluminum frame CX bike with some cheap chinese carbon clincher wheels. I find this surprising and am wondering where the added weight is coming from on the SuperX.

The wheels on my CAADX aren't featherweight, probably in the range of 1600g. I'm assuming the stock alloy wheels on the SuperX are on the heavy side, so maybe 1800g? The disc vs cantilever likely accounts for some of that difference as well, as the rest of the stuff is basically the same on the two bikes. Both have alloy handlebars and stems. The CAADX has an alloy steer tube/carbon fork whereas the SuperX has full carbon steer tube. The CAADX has a carbon seat post (some generic thing I bought ages ago) whereas the SuperX has an alloy seat post.

Cannondale lists the SuperX GRX as 19.8lbs. The current SuperX Force 1x model (also with alloy wheels) is listed as 18.6lbs. Is that 1.2 lb difference all coming from GRX vs SRAM Force? The Force model gets a carbon seat post, and a 7050 Alloy handlebar vs, 6061 on the GRX model so there might be some tiny differences there. Both have alloy wheels, though the Force model has "CX 2.0" whereas the GRX has "CX 1.0". No idea if there's any weight difference in the wheels.

I really like the GRX shifting and it's way smoother than the Force 1x on my other bike, so I'm not planning to make any changes there. I am wondering if a new wheelset, or a carbon handlebar/seat post would make a difference? I'll probably get used to the extra weight and I know it doesn't really matter for most riding, but when you're shouldering a bike and jumping over barriers, etc during CX racing, a few extra lbs can start to add up over the course of a race.

I've weighed quite a few aluminum frames in my size (I'm 5'9") to pretty confidently say an aluminum frame is about 2.8 lbs. It's funny, both road and mountain, 26er or 29er, vintage or last year, that's kinda what they weigh unless there's something exotic. Give or take .2

2.8lbs = 1275g

From my shopping online, carbon frames, especially gravel, seem to be 950g-1200g.

So yeah, you pretty much nailed it, brakes + wheels could easily be the difference. What tires are you running? Tires can be a huge difference from road to gravel.

Bikes are heavier than 20 or even 10 years ago. Heavier brakes, hubs, more spokes, wider tires. Probably safer at speed and more comfortable.

I think to run a gravel bike with 40mm tires under 20lbs would get expensive with marginal gains.

My 1998 steel frame and fork cross bike is 22lbs (21.76 actually). Discs are heavy, brakes are heavy, wheels have more spokes, and disc hubs are heavy. And if I ever replace my steel monster, it'll have all that.

Those huge cassettes on 1x bikes are heavy. I'm guessing most of that extra weight is in the rear wheel.

Interesting about the aluminum frame weights. Sounds about right though.

Both bikes were weighed with 33mm CX tires. The CAADX has Donnely MDX's on it, and the SuperX has Vittoria's that came stock. I definitely notice a difference when I install 28mm GP5000's on there. I haven't weighed the difference, but they feel a lot lighter and spin up, roll faster.

Neither bike is running what I would consider a large cassette. I think the GRX is running an 11-34 and the Force is an 11-32.

Weight weenieism is a game of grams on every single part. See here for some thoughtful stuff. This is about 4 years old but the philosophy is the thing

https://2lo8.wordpress.com/my-non-carbon-bike-6-7kg/

those weights looks spot on, you saved maybe 200-300g with the carbon frameset but lost those weight savings by going hydro. Also stock disc wheelset is prob in the 2000g range plus extra 300g for rotors

I have nothing good to say about stock wheels.

The way to save money and get better value is to upgrade the tires. That’s where the difference will be immediately felt.

A carbon fiber frame may give you bragging rights but you won’t notice any significant improvement over an alloy one, all specs being equal.

From the blog post:
"If you don’t sit around weighing your tubes for the lightest tubes in your collection, can you really call yourself a weight weenie?" :lol:

Interesting. Those numbers (+400g on the wheels and +300g rotors) would account for almost all of the 725g weight difference between the two bikes. I hadn't thought of how much weight the rotors alone add. Later today I'll weigh the two bikes without wheels just to get a different comparison.

While I can't really do much about the weight of the rotors, I will probably be buying a new wheelset at some point, just to make it easier to swap between road/off-road tires and allow me to set up tubeless. Nice to know I could drop some weight by doing this.

I feel like carbon framed gravel bikes are overbuilt compared to their road brethren. I felt the same when I got my Topstone Carbon, but it's still light. Just not the 19lbs I had in my head (and which Cannondale doesn't advertise for the 105 anyways, I just want Carbon => light) :p

Still 13lbs lighter then my hardtail!

OK, so I've gone full weight weenie on this and started thinking about ways I can trim fat from my SuperX.

Wheels are an obvious one, and while I haven't pulled the trigger yet, I'm thinking I can drop 500+ grams right there, assuming the stock wheels are in the 1900g range and a new set would be in the 1400g range.
Tires aren't as easy. The stock Vittoria Terreno Mix 33C tires are heavy at 425g. I'm going to run 32C GP5000TL's for summer road/gravel, and they weigh 375g/ea, but the sealant weighs slightly more than the tubes (125g vs 105g) so it ends up almost the same.
Rotors: The stock RT56 rotors are 133g. It looks like I can get other rotors around 110-115g so not a huge difference, but if I get a second wheelset it's another 30g savings.
Saddle: The stock Fabric Scoop Sport seat is pretty heavy at 374g. I have a Selle Italia SLR Superflow (195g) on my old bike. If I swap them, it saves 184g.
Seat post: Stock post seems to weigh around 300g. A carbon post would be 50g-80g lighter and may improve ride quality, but name brand carbon seat posts are surprisingly expensive so I may wait on this.
If I swap the 105 chain and cassette for SRAM stuff (Force cassette and Red chain) that I already have laying around, I can save 75g.

The one area I was surprised to see little difference is the stem and handlebars. I had assumed carbon parts would be way lighter, but it seems like the Cannondale C3 stuff is fairly lightweight already. Internet forums suggest 115g for the stem, and 319g for the bars. I'd have to spend big bucks on those items to drop any weight.

The saddle, seatpost, chain, cassette changes would total 360g. Wheels/rotors would be another 500g. So those changes alone would drop around 2lbs of weight.

This way madness lies...

Any calculation of $/gram?

The Easton ECSL90 is an interesting option. BB30 friendly and easy chainring swapping.

An easier option here might be to just swap my Cannondale SI (non Hollowgram) crank arms for SI Hollowgram. It looks like I can buy a pair for around $180 that would drop 115g of weight.

Ashtima Ai2 rotors $47 132g (134g savings)
Fabric Line Race Shallow saddle $105 239g (135g savings)
FSA SL-K seatpost $90 220g (80g savings)

That's $242 for 349g weight savings.
Add another $450 for a GRX wheelset and another 300ish grams of savings, and I'm 650g lighter. The chain and cassette are 80g and free since I already have them.

Total cost $700, total weight savings 729g. I do all that and my new hydro disc carbon bike will be the same weight as my 7 year old aluminum cantilever brake bike.

The rotors are an easy one, they are $0.35 per saved gram.
The saddle is a good deal at $0.78 per saved gram.
Carbon crank arms are not good, $1.81 per saved gram. Wheels are also a bit expensive at $1.48 per saved gram, but I get other benefits from a second wheelset so I'll be buying some regardless.

Alloy handlebars don't make any sense. $110 for Zipp Service Course saves 50 grams over the stock bars. Carbon bars aren't a great deal either and cost upwards of $200 to save 100 grams.

Ashima rotors are 6 bolt, GRX wheel is centerlock; adaptors have some mass.

Around $20 and 25g each for the DT Swiss CL adapters, which I accounted for already in the wheel cost. I can get GRX wheels for $419.

Is there a lightweight center lock rotor option? My quick googling didn’t turn up much.

I’m also considering a custom wheelset. PWB can do Stans Grail laced to Bitex hubs. Comes in around 1530g and $545. Would save 100g over the GRX but also costs $100 more.

I could get 6 bolt hubs so no adapter needed, which saves another 50g.

Carbon bars are so much nicer to ride... weight is secondary to me. Same with most carbon frames, they do soak up some buzz and vibration.

I had a 58cm 2016 Cannondale Synapse Carbon disc with 2x apex, alloy bars, rims and post... weighed almost 23 lbs with Dura Ace pedals. I think Cannondale’s lower end carbon bikes are pigs, generally speaking.

I have never rode carbon bars so I'll withhold judgement on the ride benefits. 100g weight savings over alloy is a nice bonus, but I do worry about the durability of carbon bars on a CX race bike. It's not a part I want to be replacing every season, and I've yet to go an entire CX season without at least one crash.

I'd agree about these C'dale bikes being heavy, but I'm not sure I'd consider the SuperX a low-end bike. They don't make a "hi-mod" version of this frameset anymore, so every version uses the same frame/fork and it's used by pro-level CX racers. What is surprising to me is that even the top-level (Force eTap) model still has a listed weight of 18.9lbs. I'm sure there could be some additional weight savings on top of that (I assume the pro riders are on SRAM Red, not Force and maybe there are lighter weight wheelsets than the Hollowgrams), but that bike is already running carbon bars, seatpost and wheelset so even with ultra light components it would still be in the neighborhood of 17-18lbs. I always assumed pro bikes were close to the UCI limit of 15lbs.

For comparison, a Canyon Inflite CF SLX 8.0 with SRAM Rival and alloy wheels is 17.5lbs. This bike is closer to what I assumed the SuperX would weigh.
Canyon bike at Pros Closet

Mine is closer to 16.5lbs. I bought the 2x version, which is lighter, and put some lighter wheels and tires on it.

I have no worries at all about carbon bars. They feel great and I'm not sure how you would hurt them in a crash. Carbon can take a huge amount of torque, but they can't take a point load. But - as they are wrapped in tape - its gonna be hard to get a point load on them.

I do worry about the carbon steerer tube. Every crash torques the handlebars, and I know that is scarring the steerer tube.

If you get 6 bolt rotors, don't forget to cut off the unused ends of the bolts. ;-)

JOM did a good explaination on how to get a gravel bike down to 17.4lbs.
https://gravelcyclist.com/training-r...n-gravel-bike/

Good link, thanks for sharing. 17.4 lbs seems perfectly acceptable to me. Not weight weenie light, but still not heavy. I'm not sure I'm ready to start shopping for titanium bolts and DA components to get there, but who knows... this stuff can be fun in a weird way. Next thing you know I'm sanding off the paint and drilling holes in things...

The Inflite was the other bike I was considering, but was unavailable in my size and I got tired of waiting. They had a Force 1x model with carbon wheels that seemed like a killer deal.

Thanks for the input on the carbon bars. I hadn't considered that they're wrapped which does provide some level of protection. I have a carbon seatpost on my other bike that has been crashed a dozen times and I've never worried about the damage, so I guess bars aren't much different.

I’ve been riding a Boone with Bontrager Aero carbon bars for a couple years. Inlooking at how thin they are in the flat segment, you wouldn’t think they could hold up to much. I weigh 240 and I’ve had a couple incidents, one where I hit a 6” deep washout at about 25 mph and did a beautiful OTB that nobody got to see. The bars were spun around in the stem so far they had locked into the frame... still riding them.