12mm or 15mm thru axle fork
 

For a gravel road bike- what's the benefit of a 15mm TA fork?

I haven't tried it, so I can't know what i dont know.
is a 12mm TA fork really not stiff enough for a gravel road bike or what is the reason(s) for a larger axle?

It seems the industry has decided for you, since most forks have already gone to 12mm axles. I went with the 15mm version of the Whisky fork, only because I already had a 15mm thru axle XT wheelset to use on the bike. Its getting hard to find a 15mm carbon Gravel specific fork.

I have a 15mm on my Raleigh Roker and a 12mm on my Canyon Endurace. The 15mm uses a thru axle that has a cam-like quick release that locks without any tools. The 12mm requires that I carry an Allen wrench to be inserted in the axle for removal. If I ever forget the Allen wrench, I would not be able to remove the front wheel.

I don't know if all bikes are like these two examples.

QR is plenty, much less 12mm TA.

For whatever reason, when road disc brakes started happening, rather than use the 15mm standard of most MTB front hubs, they decided to make a new 12mm standard. At first, gravel bikes tended to go with the 15mm, but now they are adopting the 12mm road standard. This is leaving a lot of prfectly good older MTB wheels stranded. As wider rims became popular with MTBs, the 19-22mm inner width rims that had been popular for years became out of favor for 2"+ MTB tires, but were perfect for 35-45mm gravel tires.

If you have a gravel bike for with 15mm TA, you can find those wheels fairly cheap. But if you have a 12mm TA, you can only use them if you are lucky enough to have end caps that have 19mm outer diameter instead of the 21mm OD that most 15mm TA hubs use. I had mixed luck when I changed from the All City Cosmic Stallion which used 15mm TA to the Black Mtn MCD which uses 12mm TA. I was lucky that the Roval carbon wheels that I picked up for a steal on closeout had 19mm OD end caps, so I was able to put a 12mm sleeve inside the 15mm hub and use the wheel. No such luck with the SP dynamo hub on the 650B wheels I built. That hub has 21mm OD ends which are not removable and do not fit in the hooded dropout of the MCD's fork.

Why did they make a 12mm TA, when 15mm TA already existed.


Even though they would no doubt be small, what advantages are there with a 12mm TA over a 15mm TA, which would have inspired them to create 12mm TA in the first place?

12mm axles and therefore hubs can be made smaller and lighter than 15mm hubs...in cases where the end-caps are not swappable to the larger size. Which some hubs just have swappable caps....many many more do not.

Okay I figured that would be the likely reason, but do you by any chance know what the weight savings would be on average?


I guess with the bike industry being so weight obsessed with its parts, even a 10 to 20 gram saving per wheel would probably inspire the creation of a new standard. :(

Varies by hub maker. Onyx Racing Products makes glorious hubs MUSA --however their QR/12x100 "CX/road" hubset is specific from their QR/12x100/15x100/15x110mm part

Road/CX
https://www.prowheelbuilder.com/onyx...-disc-hub.html
MTB
https://www.prowheelbuilder.com/onyx...-disc-hub.html

Claimed manufacturer weight difference between the two 75 grams. Now how much of that difference is sheer MTB "over-building versus road/CX, and how much is just due to the larger axle...I don't know.


I have a set of Onyx hubs laced up. Very ginchy. But because the carbon fork I wanted only had 15x100 TA (if you want a carbon fork, disc brake, with rack mounts-there aren't many choices), I had to get the Onyx MTB hubset.

Weight savings may be the stated excuse, but I think planned obsolescence was more of a factor.

It's so they can sell more hubs. There was no need for a 12mm TA when 15mm is more than fine. Plus it also made use of all of those cheap non boost mtb wheels that are floating around everywhere.

That wouldn't surprise me - but then again it could be that roadies had to be different from the MTB crowd, and gravel was caught in the middle (having either/or depending on brand).