21 posts • Page 1 of 1
Pardon my ignorance.... but I never saw my freehub like this.
Does this mean the rider is a strong climber? or the freehub has seen so many miles?
I'm not sure if I should be happy or sad to see a freehub like this?
I had to copy this image from another WTS thread.
looks pretty normal for a shimano freehub. It must be a lightweight aluminium body. they seem to mark easier.
All of my aluminium freehub bodies look like this. It's usually caused by gearing down under load...like sprinting.
You can see that the freehub body isn't marked where the 3 largest sprockets are because the largest 3 sprockets are on a spider and the spider spreads the load across a wider area on the freehub.
If there is too much damage you will have problems getting the cassette on/off the freehub. I've had to file mine down to get the cassette on easily.
I don't think there are any performance issues.
I din't know the freehub is alloy... i thought alloy would be too soft for this application and steel would make more sense. anyways i got the 3 largest cogs on a spider to distribute the load, but why can't they put all the cogs (except the smallest few) in a spider to spread the force more evenly and make the whole cassette even lighter?
I don't think having a spider on the rest of the cogs will make the cassette lighter. i reckon it'll make the heavier...more material.
It would take more work manufacturing the cassette and more labor intensive too, so more expensive.
Steel makes more sense in terms of durability but at a weight cost.
Alloy freehubs aren't a bad thing, they last for 1000s of kms before needing replacement. They wear quicker than steel but they are light. Light = fast...in theory.
You'd probably go through a few cassettes before having to replace an alloy freehub.
The problem with most high end, light weight parts is that they tend to wear quicker like chains, chainrings, cassettes, tyres, brake pads.
For a weight weenie like myself it's worth it
It just hurts the bank account.
No, it's not normal.
The major cause is not tightening the cassette lockring to Shimano's specification, which is 40Nm.
I will go with lightweight alloy freehub body and Shimano cassette.
Used to have this exact problem using Shimano on American Classic or Token wheelsets.
Shimano cassettes will particularly cause this due to the 3(?) outer cogs being seperate from the rest of the cassette.
As suggested by someone earlier a little filing and deburring and you are AOK.
i just use a big wrench and tighten the cassette lockring by feel. any tips how tight a 40Nm is if you don't have a torque wrench?
If I remember right, simplistically speaking 40Nm is the equivalent of a 40kg weight placed at the end of a shifter with a one metre long handle (assuming little to no weight in the shifter). The equivalent downward force exerted by that weight is 40Nm.
there have been a few threads about this in the past
mine has not gotten any worse after I installed the kit, but my freehub was worse before I installed the kit and the free hub was new and I had definitely done less than 1000km (from memory it was probably more like 200km)
Yes, it is normal. There isn't a used aluminium freehub that i've seen that doesn't have marks on it from shimano cassettes...and i've seen 100s of freehubs when i used to build wheels for a shop.
Tightening your cassette to 40Nm won't stop this from happening. As important as it is, it has little to do with this issue at hand IMO
The issue here is when a single cog engages the freehub, it 'point loads' the freehub. Tightening the cassette won't stop point loading nor will it spread the torque load across the body of the freehub.
There are also other factors at play here also. One being the quality of the aluminium the freehub is made out of and another is the ride style of racer.
Criterium sprinters chew through aluminium bodies. Mainly from tremendous torque loads while sprinting.
Two main methods of damage are:
- the massive amount of torque produced when the chain re-engages the cog after down shifting.
- the massive amount of torque produced when the sprinter re-engages the peddle from coasting.
To supplement... Half metre handle needs 80kg and a 25cm handle needs 160kg. Might as well stand and jump on it if the handle is short.
This isn't correct. From high school physics Torque = mass x g x moment arm g being gravitational constant of 9.8. so its closer to 8kg for a half metre handle.
It is actually big wrench x pretty darn tight.
You are correct. There's a factor of 9.8 for the a (in F =ma). I was just concentrating on the lever length aspect which is in direct ratio.
Ah yes, and for a one metre long handle - it is about 4kg of force to the (end of the) handle to generate 40Nm on the lockring. Which actually isn't very much.
It's still a lot. Maybe six times as tight as the bolt pinching a brake cable in place, a tension most of us are familiar with ...
http://www.parktool.com/blog/repair-hel ... d-concepts
Yeah, I was thinking that 40kg on a metre lever would just about jack a car off the ground. You would strip the thread on any nut or bolt way before you finished applying that amount of force.
You have officially become your parents.
If thats the correct math, i need to go loosen my cassette rings !!!! I use a wrench thats a bit short of half a meter and I was cranking it !!!
thanks for the numbers guys, Ill have a better idea of what 40 is now ie anything bigger than my 15 NM torque wrench will go.
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