rcommbikes 

We have a Fulcrum wheel with a freehub that has this spline configuration. Does this take special cogs? It looks weird to me like once the cog slides on over the wide part of the hub it will slip back and forth in the larger space near the wheel. Why are the splines shaped like this? Thanks for your comments.


Fred

FBinNY 

I suspect that they milled away whatever they could to save weight.

In any case, it's the same as other freehubs with the same spline pattern.

Cogs are centered by the outer surface so the deeper cut doesn't matter. Also, since it's a freehub, cogs will rotate forward to rest against the straight spline and stay there, so the cut away back side doesn't matter.

Crankycrank

You might have to ask Fulcrum but seems to me to be a possible weight saving tactic where they have the steel where it's needed and not where it isn't and still functions properly. Cogs will slide on the same as any other conventional freehub splines. Fulcrum HG 11v Racing Light 2014 Freehub Body | Bikeinn (tradeinn.com)

Looks like FBinNY beat me to it above.

KCT1986

The splines are cut-away in the non-driving side. But as picture, at least 1 of the splines is full width so the sprockets can't rotate. Should not be enough force in that direction to need more that 1 full spline.

FBinNY 

The wide spline isn't for strength. It's an orienting spline to ensure that individual sprockets are all in the same position relative to each other.

That's critical because the shift gates all have to be in the right place.

BTW there's no need to prevent sprockets from rotating back off the driving bar because it's a freehub and therefore impossible.

KCT1986

Never said the wide spline was for strength.

Said that as long as one of the splines is not cut-away on the back side, it is strong enough to prevent the sprockets from rotating in the non-drive direction.

Even the extra wide spline could be reduced, as long as the outer end is its full width and one of the other normal width spline is full profile. One spline should still be full profile to make installation easier, if not the inner sprockets or spider can initially rotate out of position until driving force pulls it against the spline.

FBinNY 

That's exactly the point I was countering.

There's simply no (zero) need for anything to prevent sprockets from rotating or being installed without the front edges fully butted against the spline. The first time they're used the chain will pull them forward as far as possible. Once there, they'll obey Newton's first law and stay put.

As I said, the wide spline is for orientation and ONLY for that.

rcommbikes 

I agree with weight reduction although I can’t imagine that it’s more than a few grams. Thank you all