Will a corroded sprocket damage the hub oil seal?

[goosander]

The other day I removed the chain from my RST and gave it a good clean with paraffin and a tooth brush and also took the opportunity to remove the sprocket, partly for cleaning & partly to reduce the likelyhood of it becoming stuck on (it takes serious force & a strong chain whip to get the it off).  After cleaning I noticed that on the exposed side of the sprocket, it was a bit corroded & pitted due to road salt etc, so was wondering if the pitting was likely to damage the hub oil seal when the time came to reverse the sprocket.

After going to all that effort, I thought I would get another couple of thousand miles out of the chain & sprocket (currently at 6700 miles), but today the chain failed with broken side plates in three places, so it looks like I'll be replacing the chain & reversing the sprocket a bit sooner than I hoped, so should I go ahead and reverse the sprocket or would I be better replacing it?

[stutho]

When I reversed my sprocket the same thought occurred to me.  I cleaned it up the best I could and gave it a bit of a polish before reversing. It still wasn't perfect, but every little helps.

Incidental what chain were you using?  I got quite a few more mile out of mine before I retired it (Sram PC 68 - I belivethey have now renamed this model)

[goosander]

It was a SRAM PC48.

I'm a bit disappointed with the mileage.  I had hoped to get 10000 miles out of it, certainly the sprocket & chain ring looked good for more.

[stutho]

I managed to get the legendary 10,000   

[expr]

The using of a corroded sprocket will prematurley reduce the usable life of the hub lip seal.  This is like putting a light sanding paper to the seal and spinning the wheel, the seal will still seal due to the way in which it is made if the corrosion isn't to bad as the lip seal in under spring tension allways keeping an even pressure on the face.

But to perform as it was designed to the face should be in contact with a smooth polished surface not a pitted or corroded one.

It would be cheaper in the long run not to reverse the sprockett, but to put a new one on instead of furhter down the road having to replace the hub seal. Even if you do the hub seal yourself the tool to do the job is around £40 plus the £9.99 hub seal, plus £14.99 for the oil change or should I say top up as the oil will have started dripping out of the lip which is what will have alerted you to the fact that you should have changed the sprocket not turned it around .   - vs £28.99 for a new sprocket.

[goosander]

Well I cleaned it up as best as I could and the surface seemed quite smooth, so its OK.

Why do you need a tool to remove the oil seal?  It looks like it can just be levered out and a new one pressed in, though I didn't look closely.  Do you have a link to where the seal & tool can be obtained from, just incase they are needed in the future.

[stutho]

The tool is a press to insert the new seal squarely to the hub - I wouldn't bother getting one! IF the seal does go then I am sure that SJSC would be able to replace it for a small fee.  If the seal went on tour then Rohloff claim that the hub can be used with no free oil inside the hub  for up to 5000K. -  NOT RECOMENDED

(NB There will be some oil sticking to the gears - running the unit total dry will kill a Rohloff very quickly - maybe 5 miles! )

[expr]

Well I cleaned it up as best as I could and the surface seemed quite smooth, so its OK.

Why do you need a tool to remove the oil seal?  It looks like it can just be levered out and a new one pressed in, though I didn't look closely.  Do you have a link to where the seal & tool can be obtained from, just incase they are needed in the future.

Hello goosander,

in answer to your question the tools and seal can be purchased from sjs cycles. Personaly I would buy the tool and do the job myself but thats because I enjoy doing such tasks and have always done all types of repair / service jobs with most tasks around the house and beyond, not because i want to be smart but because i enjoy it, as other people have suggeted they would allow some one else to do the job and that is something that I would never consider.

[goosander]

If as Stutho suggests, the tool is simply a press to ensure correct seating of the seal, I doubt if I would buy one either.  I'm sure a suitably sized socket would do the job.

BTW, this site might be of interest:  http://tricolour.net/rohloff.html

This guy has seemingly successfully disassembled & reassembled his hub including replacing the bearings without anything much in the way of special tools.  Can't say I'm particularly keen to dismantle it without good reason, but I might have ago if the bearings ever need replacing and the alternative is an expensive service by Rohloff.

[expr]

Hi goosander,

 yes im aware of that guy, I to have had the hub apart but decided to leave the oil seal's in the hub, iv'e had all the pawl springs out and the planetary gears very interesting. Yes you could possibly press the new lip seals in with a sockett but the actual wall on the lip seal is very slight and would require a certain amount of concentration. I have myself used that method for similar tasks and got the job done, but as I say on this occasion and given the cost of a new hub I wouldn't take any chances of a socket slipping etc. I am a great believer in the right tool for the job and that does include making it myself if i can, in the case of the oil seal driver the correct rohloff tool actually uses the sprocket thread to engage the tool and it pushes the oil seal down by winding the tool in without causing any possible damage. I do actually like making my own tools and get great satisfaction out of it but sometimes its more cost effective to just buy the right tool and bite your lip.

In no way am I trying to be smart on this question but it's a no brainer for me I just would not have fitted the corroded sprocket, I have seen many oil seals ripped apart over the years in my job just through the shaft being exposed to the elements, its a vicious circle a little corrosion wears the seal a bit, so then more corrosion gets in underneath and so on, it does'nt get better! 

As I have said in a previous post the oil seal is under spring tension and will probably keep a good seal for some time , just not as long as it would have done if the sprocket had been a perfect face.The other thing to consider aswell is that for the majority of time the oil is around the inner case not up the sides where the seals are, so not a great deal of chance of loosing much oil unless tiped on its side but the down side is that liquid and foreign objects can enter the hub, I'm not even going to go in to that one as it speaks for itself. It boils down to how much your hub matters to you and how you want to look after it. Again £40 for the hub seal tool seems insignificant to the £850 or so for the new hub. You can see oil coming out but you can't see water and grit going in. Which is a part of the problem that the guy in the link had with his hub.

Regards

Dave.

[goosander]

It seems you may have been right about fitting a new sprocket - my oil seal is now leaking.  More worrying is that the sound that the hub makes when freewheeling has changed, so I suspect that one or more of the internal pawls are not functioning correctly though the hub is still functioning normally.

[expr]

Hello Goosander,

It could be one or two reasons, firstly it could be that the sprocket has worn the seal face away and the oil is passing due to this,

secondly it could be because the sprocket has the pitting / corrosion in it that the seal face can't properly mate with the oil seal and so its the sprocket letting the sealing down.

I would be tempted to change the sprocket for a good new one and test for leaks by spinning the wheel on its sprocket side down, if that doesn't work then the oil seal/s will have to be changed.

The noise in the gearbox could be one of two reasons firstly it could be that you are just thinking that it's different due to the fact the hub is leaking or it could be the change in oil amount is allowing the pawl/s to make a different noise when opening / closing.

The pawls either work or don't there is no in between.

The only other thing it could be but I'm clutching at straws here is if the bike has been in a very warm room then this could affect the internal pressure to rise therefore forcing oil out, giving the illusion of an oil leak.

http://www.photobox.co.uk/album/168875892

[goosander]

I've now had a closer look at it and I'm not so sure that the oil is actually leaking between the sprocket and seal as I originally thought.  The oil seems to be coming from the vicinity of the driver nut (the odd shaped alloy nut with two flat sides), which might suggest that the oil seal on the driver bearings have failed.

Unfortunately, the leak doesn't seem to be very obvious, e.g. turning the hub on its side doesn't cause oil to leak.  I think I may have to give it a good clean and then take it for a decent cycle and hope that the normal action of the hub will force a bit more oil out so I know for sure.

Thanks for the photos.

[expr]

Hello goosander,

the driver bearings have four seals, two on each of the bearings, at first when I originally looked at the hub and how it was made I thought that it was a bad design having such a delicate seal face exposed to the elements, and although this is still an issue, the potential problems that can arise are not as bad as I thought.

By this I mean, if the seal face becomes damaged by an external source then I thought that all oil could be lost, but that's not the case, the oil is still kept in by the remaining three oil seals on the remaining faces (which are internal) of the hub and this side of the oil.

However there is a possibility that oil can migrate/ sweat around the periphery of the pressed in bearing and cause it to look like an oil leak. Also temporary leaks can be caused from foreign objects becoming lodged between the oil seal face lip and the sprocket.

Have you also looked to see if the hollow axle is wet inside, this is also an area of possible leakage.

Best thing to do is as you suggest, if you get a nice clean paint brush with a little soapy water and clean the hub totally around that area and then keep your eye closely on the situation.

Hope this helps,

Dave.   

[goosander]

There is no oil leakage on to the QR but it is definately leaking oil.  The chain has needed hardly any lubrication over the last couple of months, so I think it has been lubricated by leaking hub oil, and the sprocket area smells strongly of hub oil.

Unfortunately, I won't have any time to look at it for at least a week, but will report back later.

Thanks,

David