Dura Ace 7900 Freewheel Issue

[NickR]

A little back story, noticed my chain skipping under load. After several attempts to diagnosed issue and ready to throw in the towel. For some reason i can recall, i removed the rear tire and had the Eureka moment. I dissembled the hub in the hopes it was a inexpensive fix. I need to replaced the Freewheel body since it doesn't always engage. Looking around the web the replacement body is almost the same price of complete hub. Anybody have a link to a less expensive replacement like half the price :) or a cheaper alternative that would work on the hub. Thanks in advance.

Nick

https://smartbikeparts.com/search_details.php?itm=Y3D898060


Update 1.29.2016:

Thanks to a member on here i picked up a complete hub. Finally had some time to do the freewheel body swap, all when well. I had my LBS swap the freewheel body since i don't have a big enough allen to remove it. The freewheel spun nice and smooth, so i reassembled it. Checked again to make sure it all spin without issue, installed the cassette and took it for a ride. 20 miles into the ride my skewer broke and shootout and i come to a complete stop (It felt like someone grab my bike). Once home i started the task of disassembling the hub and notice it's bind up, won't freewheel or spin while holding the axle ends. I had to grind the left side cone to be able grab it with a adjustable wrench, one loose the freewheel spun like normal. So what did i do wrong?

[oldpotatoe]

A little back story, noticed my chain skipping under load. After several attempts to diagnosed issue and ready to throw in the towel. For some reason i can recall, i removed the rear tire and had the Eureka moment. I dissembled the hub in the hopes it was a inexpensive fix. I need to replaced the Freewheel body since it doesn't always engage. Looking around the web the replacement body is almost the same price of complete hub. Anybody have a link to a less expensive replacement like half the price :) or a cheaper alternative that would work on the hub. Thanks in advance.

Nick

https://smartbikeparts.com/search_details.php?itm=Y3D898060

Have you tried to remove, take the seal off the back, flush and light lube?(I use Mobil One)..It's a simple 2 pawl system. Maybe one is just stuck down.

Titanium so expensive.

[palincss]

Is this the freewheel that everyone says is the "best freewheel ever made," and "there's nothing made today with anything like that level of quality"?

[oldpotatoe]

Is this the freewheel that everyone says is the "best freewheel ever made," and "there's nothing made today with anything like that level of quality"?

Think it's the 'freehub' body, since he mentioned '7900'.

[Look585]

Like OldPotatoe said, first step is to try to clean/lube the one you have. You can often wake up the sleepy pawl and get back on the road.

Otherwise, your best option is to find an old hub with a good FHB. Lots of 10s (7900) hubs have been obsoleted by 11s and will be cheaper than a new FHB replacement. Or just buy a DA9000 hub and rebuild the wheel for about the same $$$ as the replacement FHB.

I have a (useless to me) 7900 rear with a good FHB I'd sell cheap... :)

[CiclistiCliff]

Check to see if the 6700/5700 freehubs are compatible. No Ti, but if they fit, it's a 30 dollar freehub.

[NickR]

Have you tried to remove, take the seal off the back, flush and light lube?(I use Mobil One)..It's a simple 2 pawl system. Maybe one is just stuck down.

Titanium so expensive.

I'll give that a try

Like OldPotatoe said, first step is to try to clean/lube the one you have. You can often wake up the sleepy pawl and get back on the road.

Otherwise, your best option is to find an old hub with a good FHB. Lots of 10s (7900) hubs have been obsoleted by 11s and will be cheaper than a new FHB replacement. Or just buy a DA9000 hub and rebuild the wheel for about the same $$$ as the replacement FHB.

I have a (useless to me) 7900 rear with a good FHB I'd sell cheap... :)

Interested, pm coming

Check to see if the 6700/5700 freehubs are compatible. No Ti, but if they fit, it's a 30 dollar freehub.

Not sure if they are compatible and couldn't find any info on the web. The reason for posting here, hoping someone had experience with swapping FHB from another model saving $$$

[NickR]

Have you tried to remove, take the seal off the back, flush and light lube?(I use Mobil One)..It's a simple 2 pawl system. Maybe one is just stuck down.

Titanium so expensive.

By flush, i take it with compress air? or WD-40?

[NickR]

bump

[kramnnim]

WD-40, diesel, etc...

[bicycletricycle]

The wheel bearings and freehub both bound up?

And with a simple loosening of the wheel bearing non drive side cone both freed up?

Hmmm, the easiest explanation is that one of the wheel bearing cones unlocked from its locknut and crept inwards preloading the bearings till they where seized.

However

I don't think that this would seize the freehub as well

the free hub bearings are not adjustable and shouldn't be effected by the preload of the wheel bearings.

The freehub has a washer between it and the hub shell, if it is missing than normally the freehub just seizes up as soon as you tighten up the huge hollow Allen bolt that holds it onto the hub shell.

If for some reason the large hollow bolt that attaches the freehub to the hub shell came loose it might cause the problem you are having.

If someone forgot the washer or used the wrong one than perhaps they didn't torque the freehub down properly to keep it from seizing.

So, either the freehub came loose or the cup and cones tightened up.

I'm betting the freehub came loose, it explains the bearing and freehub seizing more easily than just the hub bearings.

Get the huge Allen wrench and do it yourself this time.

IMHO

[NickR]

The wheel bearings and freehub both bound up?

Yes

And with a simple loosening of the wheel bearing non drive side cone both freed up?

Yes

Hmmm, the easiest explanation is that one of the wheel bearing cones unlocked from its locknut and crept inwards preloading the bearings till they where seized. That might be the case, i though i double checked the bearing adjusted was on right. From the looks of it, the bearings wore into where they get seated and seized after a while. In hindsight I do recall a tick when spinning the wheel prior to installing on bike.

However

I don't think that this would seize the freehub as well

the free hub bearings are not adjustable and shouldn't be effected by the preload of the wheel bearings.

The freehub has a washer between it and the hub shell, if it is missing than normally the freehub just seizes up as soon as you tighten up the huge hollow Allen bolt that holds it onto the hub shell.

If for some reason the large hollow bolt that attaches the freehub to the hub shell came loose it might cause the problem you are having.

If someone forgot the washer or used the wrong one than perhaps they didn't torque the freehub down properly to keep it from seizing.

So, either the freehub came loose or the cup and cones tightened up.

I'm betting the freehub came loose, it explains the bearing and freehub seizing more easily than just the hub bearings.

Get the huge Allen wrench and do it yourself this time.

IMHO

[oldpotatoe]

I'll give that a try



Interested, pm coming



Not sure if they are compatible and couldn't find any info on the web. The reason for posting here, hoping someone had experience with swapping FHB from another model saving $$$

Lower end FH bodies are not compatible with other hubs, like a 6700 into a 7900, type thing. shimano has always made hubs 'in triangles'..in that they are designed and built w/o any intercompatibility built in..

[jc031699]

The bearing race on the driveside is integral to the freehub body, right? So if the bearings seize the freehub body will no longer ratchet. That is my guess.

Believe it or not I have overhauled a shimano freehub body. I was able to find a drag link socket that fit perfectly with minimal grinding. Not rocket science. If you can overhaul a campy shifter you can do this.

[oldpotatoe]

The bearing race on the driveside is integral to the freehub body, right? So if the bearings seize the freehub body will no longer ratchet. That is my guess.

Believe it or not I have overhauled a shimano freehub body. I was able to find a drag link socket that fit perfectly with minimal grinding. Not rocket science. If you can overhaul a campy shifter you can do this.

I have too, have this..that race is left threaded-righty-loosey. Watch the bearing balls..1/8 inch and a bunch of them.

[bicycletricycle]

Ya the freehubs are rebuildable but they aren't really meant to be, pain in the ass really, forcing a bunch of oil in does the same thing in my experience

[bicycletricycle]

The bearing race on the driveside is integral to the freehub body, right? So if the bearings seize the freehub body will no longer ratchet. That is my guess.

Believe it or not I have overhauled a shimano freehub body. I was able to find a drag link socket that fit perfectly with minimal grinding. Not rocket science. If you can overhaul a campy shifter you can do this.

The bearing race is part of the freehub body but race rotates in sync with the hub not the freehub when attached. The drive side bearing should be able to be seized while still having a properly working freehub.

[oldpotatoe]

The bearing race is part of the freehub body but race rotates in sync with the hub not the freehub when attached. The drive side bearing should be able to be seized while still having a properly working freehub.

I agree, something else is going on. Tight drive side bearing/cone shouldn't prevent FH body from freewheeling. I wonder if big spacer under FH body not there.

[jc031699]

The bearing race is part of the freehub body but race rotates in sync with the hub not the freehub when attached. The drive side bearing should be able to be seized while still having a properly working freehub.

Ah yeah, that's right-

[moobikes]

I think your non-drive side cone is the problem. It was not properly locked together with the keyed locknut. Forward motion of the wheel will cause the cone to rotate clockwise until it is so tight the hub seizes.

Bearing cup on the drive side is machined into the FH body, or pressed into FH, same result, and rotates with the FH. If non-drive cone tightens down to the point the hub seizes, the FH will seize too. Once the non-drive cone is loosened, FH is free to rotate.


I do not know how the broken QR is connected to the event. If the QR was tight enough to hold the non-drive cone in adjustment, then it might explain how the bearings seized after it broke.

[bicycletricycle]

the cup in the free hub does not need top rotate for the freehub to freewheel freely.

[moobikes]

On the drive side the cone is epoxied to the axle. The cup is the rotating part. Squeeze the two tightly enough and the freehub will seize.

[moobikes]

I meant cup, not race.

[NickR]

The bearing race is part of the freehub body but race rotates in sync with the hub not the freehub when attached. The drive side bearing should be able to be seized while still having a properly working freehub.

I agree, something else is going on. Tight drive side bearing/cone shouldn't prevent FH body from freewheeling. I wonder if big spacer under FH body not there.

The bearing race on the driveside is integral to the freehub body, right? So if the bearings seize the freehub body will no longer ratchet. That is my guess.

Believe it or not I have overhauled a shimano freehub body. I was able to find a drag link socket that fit perfectly with minimal grinding. Not rocket science. If you can overhaul a campy shifter you can do this.

Thanks guys, need to order some tool and see if i can remove the bearing race from the Freehub body. On further inspection i noticed it's cracked, and due to the non drive side cone tightening that's what actually cause it to bind. At least that's my guess

I think your non-drive side cone is the problem. It was not properly locked together with the keyed locknut. Forward motion of the wheel will cause the cone to rotate clockwise until it is so tight the hub seizes.
That's what I'm leaving towards. I just though it was dummy proof how they design the bearing adjuster & cone to lock in to the axle. Also that it would've locked sooner instead of 20 miles later. To me it felt fine then all of a sudden it seized.


Bearing cup on the drive side is machined into the FH body, or pressed into FH, same result, and rotates with the FH. If non-drive cone tightens down to the point the hub seizes, the FH will seize too. Once the non-drive cone is loosened, FH is free to rotate. That's what i experienced trying to losing the non drive side cone. As soon I loosened it, it went back to normal operation. It did take getting out the dremel out to create flats spots for the wrench.


I do not know how the broken QR is connected to the event. If the QR was tight enough to hold the non-drive cone in adjustment, then it might explain how the bearings seized after it broke. I think this was the weakest link in the chain so it gave out before other things.

[bicycletricycle]

holy crap, cracked cup in the freehub body.

i don't think you can get those, shimano views the whole freehub body as one component.

i guess the cones did just super tighten and freeze everything up.


i would call that hub toast.

[NickR]

holy crap, cracked cup in the freehub body.

i don't think you can get those, shimano views the whole freehub body as one component.

I have my old one, just hoping it comes off like OP posted with the tool.

[oldpotatoe]

I have my old one, just hoping it comes off like OP posted with the tool.

Righty-loosey-left threaded.

I slam mavic all the time for their crappy 2 pawl rear hubs but shimano has been doing the same..yes, their FH bodies are more durable and bolted to hub body(via patent, only hub maker to do this), but 2 pawls are so 1980s..be nice of they had one ala 7800/7801..but betta.