Shimano freehub body internals

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hoogerbooger
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Re: Shimano freehub body internals

Post by hoogerbooger »

I can see there won't be agreement here. Apologies to have lengthened the debate.

All I can say is I appreciate very much the reasoning outlined in the posts as it is from that others can learn/ come to their own conclusions.
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rogerzilla
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Re: Shimano freehub body internals

Post by rogerzilla »

The last time I did one, I took the freehub body off and left it submerged in oil for a few days.
Pebble
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Re: Shimano freehub body internals

Post by Pebble »

Have never used SFG, is it viscous enough to assemble it after a dismantle ?

I seem to do mine every year just using as little multi purpose grease as possible, have always believed too much could cause the pawls to stick down ?

anyway busy doing mine tonight, as usual it is just full of black road gunge.
before and after cleaning
Image
Image
Last edited by Pebble on 15 Apr 2021, 9:48am, edited 1 time in total.
TheBomber
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Re: Shimano freehub body internals

Post by TheBomber »

If Shimano's 'freehub grease' is SFG then your answer is 'yes'. As i don't have a Landrover I'm not so sure about anything that is labelled 'SFG'. The Shimano stuff is expensive but you don't need a lot so it should last.

For an annual servicing routine that old grease does look a little black and watery. What state was the wheel bearing in? Or perhaps it is an older freehub body with no seal on the inside face? Seeing the size of those pawls does remind me how much more robust looking the older/more basic freehub models are though - compared with the 2 pairs that I have had issues with recently.
Pebble
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Re: Shimano freehub body internals

Post by Pebble »

I think the seal on this has been gone a few years now, so yes that black gunge will be a mix of grease, water, road salts, oil, gt85.... That's why it needs cleaned out at the end of the winter. I noticed last week it done a few little skips so I suspected it would be a bit of a mess. The pawl you can see would stick in the recess if pressed in.

I have just used multi purpose grease in the past and it seems to work OK, but after reading this thread thought I might try something else. I have some marine grease - may be I will try that (its a bit stinky though)

I am always fascinated by the way they offset the two pawls - is this to somehow let them both engage better ?
Image

the detail in the photo shows there is still a bit of stubborn dirt in the ratchet, that pawl should be going fully down
TheBomber
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Re: Shimano freehub body internals

Post by TheBomber »

I am always fascinated by the way they offset the two pawls - is this to somehow let them both engage better ?
That always gets me too - especially as there always appears to be a slot where a third one should go (well highlighted by your last photo) even though as I recall you can't actually put a pawl in there. As for an answer, we need a proper engineer to explain. Brucey probably has in the past but I've not seen it/can't remember it.

A more sticky grease will increase the chance of the pawls getting stuck down so it feels like you are heading the wrong way there. However, if the seals are worn then a SFG might just get pushed out so that's no good either. Perhaps your current grease and maintenance regime is exactly right?
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531colin
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Re: Shimano freehub body internals

Post by 531colin »

SunTour used to make freewheels with the pawls diametrically opposed; some junior freewheels were also made that way.
As soon as you get the slightest bit of play in the freewheel, it will rock from side to side (with the 2 engaged pawls as fulcrum) twice every pedal revolution, going clonk clonk clonk down the road.
With the 2 offset pawls (both engaged at the same time) you have a third point of contact which isn't a pawl, its the inner and outer ballraces of the freewheel, so this one can't clonk, because it can't rock.
Other working solutions are 2 pawls in any orientation you like, but with only one engaged at any one time, and 3 pawls all engaged at once, as on some Tandem special freewheels.
TheBomber
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Re: Shimano freehub body internals

Post by TheBomber »

Colin - thanks for that explanation. I do wonder how long it would have taken me to think of that!

What is the chance of that clonking issue occurring within a freehub body that has offset pawls? I fitted a new replacement one to an SLX hub (2 pairs of offset pawls with only 1 pair engaged at any time) last year and it does occasionally suffer from a clonk - clonk - clonk sound. That’s why I now have a tool to open the things as it felt like there was excess play even though it was new. I removed one of the spacer shims from the inside (which still left a tiny amount of play) and the problem has reduced in frequency of occurrence as well as volume. It’s still there though and has remained a mystery to me. Whenever it occurs a momentary freewheel before restarting pedalling cures it.

Incidentally the XT freehub body I bought for the hub that this post was originally about also had excessive play - again resolved by removing a whole shim. It would seem that Shimano freehubs are not being made as well as they used to be. Or maybe I’m just more fussy now.
Pebble
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Re: Shimano freehub body internals

Post by Pebble »

TheBomber wrote: 16 Apr 2021, 8:16am Colin - thanks for that explanation. I do wonder how long it would have taken me to think of that!

What is the chance of that clonking issue occurring within a freehub body that has offset pawls? I fitted a new replacement one to an SLX hub (2 pairs of offset pawls with only 1 pair engaged at any time) last year and it does occasionally suffer from a clonk - clonk - clonk sound. That’s why I now have a tool to open the things as it felt like there was excess play even though it was new. I removed one of the spacer shims from the inside (which still left a tiny amount of play) and the problem has reduced in frequency of occurrence as well as volume. It’s still there though and has remained a mystery to me. Whenever it occurs a momentary freewheel before restarting pedalling cures it.

Incidentally the XT freehub body I bought for the hub that this post was originally about also had excessive play - again resolved by removing a whole shim. It would seem that Shimano freehubs are not being made as well as they used to be. Or maybe I’m just more fussy now.
where did you get the special tool from - I ended up having to make my own
531colin wrote: 15 Apr 2021, 8:50pm SunTour used to make freewheels with the pawls diametrically opposed; some junior freewheels were also made that way.
As soon as you get the slightest bit of play in the freewheel, it will rock from side to side (with the 2 engaged pawls as fulcrum) twice every pedal revolution, going clonk clonk clonk down the road.
With the 2 offset pawls (both engaged at the same time) you have a third point of contact which isn't a pawl, its the inner and outer ballraces of the freewheel, so this one can't clonk, because it can't rock.
Other working solutions are 2 pawls in any orientation you like, but with only one engaged at any one time, and 3 pawls all engaged at once, as on some Tandem special freewheels.
I had sort of thought it would somehow help distribute the load more evenly over the two pawls but never quite got my head round why.

The pawls do have a lot of work to do with all the energy is going through them, and only engaging 12mm up a 350mm radius wheel gives them quite a mechanical disadvantage - I am surprised they last as long as they do
TheBomber
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Re: Shimano freehub body internals

Post by TheBomber »

Freehub tool came from eBay. I also made one originally and it worked for the first freehub but subsequent ones were too tight - my home made one didn’t have a bolt through the hub to hold it in place so it had a tendency to slip. The eBay ones are Chinese made but seem to be absolutely fine for the job and it was delivered much faster than the 2 weeks predicted.
Pebble
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Re: Shimano freehub body internals

Post by Pebble »

TheBomber wrote: 16 Apr 2021, 8:57pm Freehub tool came from eBay. I also made one originally and it worked for the first freehub but subsequent ones were too tight - my home made one didn’t have a bolt through the hub to hold it in place so it had a tendency to slip. The eBay ones are Chinese made but seem to be absolutely fine for the job and it was delivered much faster than the 2 weeks predicted.
Indeed I see they are available now on ebay, quite reasonable and I like the idea of the skewer. I couldn't find anything 4 or 5 years ago so ended up making my own out of a 11/16th socket
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531colin
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Re: Shimano freehub body internals

Post by 531colin »

TheBomber wrote: 16 Apr 2021, 8:16am........
SLX hub (2 pairs of offset pawls with only 1 pair engaged at any time) ..........
You can't mean 4 pawls in a hub body? I'll assume you mean a pair of pawls, (each pawl having a groove where the spring seats) and only one pawl engaged at once.

One pawl engaged means that opposite the engaged pawl is a contact point, which would normally be the inner and outer rows of ballbearings in the hub body, which is a wide base so it can't rock, can't clonk. The only thing I can think of which might allow a clonk is a problem with the distribution of the balls, maybe too few balls in one raceway so one raceway has a gap and it becomes point contact?
rjb
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Re: Shimano freehub body internals

Post by rjb »

531colin wrote: 17 Apr 2021, 5:57pm
TheBomber wrote: 16 Apr 2021, 8:16am........
SLX hub (2 pairs of offset pawls with only 1 pair engaged at any time) ..........
You can't mean 4 pawls in a hub body? I'll assume you mean a pair of pawls, (each pawl having a groove where the spring seats) and only one pawl engaged at once.

One pawl engaged means that opposite the engaged pawl is a contact point, which would normally be the inner and outer rows of ballbearings in the hub body, which is a wide base so it can't rock, can't clonk. The only thing I can think of which might allow a clonk is a problem with the distribution of the balls, maybe too few balls in one raceway so one raceway has a gap and it becomes point contact?
I had a Quando freehub on the tandem. It had an annoying once a revolution tick. When I stripped it I found 24 balls on one race and 25 on the other. I rebuilt it with 25 balls on each race and it's now quiet.
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
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kylecycler
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Re: Shimano freehub body internals

Post by kylecycler »

TheBomber wrote: 16 Apr 2021, 8:57pm Freehub tool came from eBay. I also made one originally and it worked for the first freehub but subsequent ones were too tight - my home made one didn’t have a bolt through the hub to hold it in place so it had a tendency to slip. The eBay ones are Chinese made but seem to be absolutely fine for the job and it was delivered much faster than the 2 weeks predicted.
I'd echo that - same experience - arrived so soon it was as if it was from the UK (although I don't know how or if the pandemic will affect shipping now), and it's a quality tool. Pebble did a nice job on the 11/16th socket but for all the tool costs it's well worth getting one.
TheBomber
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Re: Shimano freehub body internals

Post by TheBomber »

You can't mean 4 pawls in a hub body?
Yes, that is what I mean. I can’t seem to find a photo at the moment but obviously they are smaller than the ones in Pebble’s picture above. Each pair have their own spring squeezing on an ‘ear’ that is either on the inner or outer side of the freehub body. The idea is they give you faster pick up of the ratchet as the required rotation is halved. This is only an issue when trying to restart on a steep off road climb with clipless pedals and low gears. The problem is real but I’m not convinced the freehub modification really solved it.

Given what you say, and rjb’s comment, I may investigate the ball bearing situation. They are just spare wheels now though, since I brought the XTR ones back into service by building them onto some nice 700c rims.

Re the freehub tools, I made mine during lockdown 1 as I needed to sort a more serious problem with the freehub and wasn’t convinced anything I ordered would arrive quick enough. It can be done with a hacksaw and a file but the eBay ones are better with their securing bolt. I don’t keep either one in the fruit bowl though :wink:
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