Shimano free hubs. 7 & 8 speed differences

[mattsccm]

I am in the process of building a rear wheel starting from a bare Shimano hub shell . It will be to take a 8 speed + Shimano cassette but Without stripping another wheel I can't check the widths of 7 and 8 speed freehubs across the cones. . I know they are different widths across the splines and I have a pile of 7 speed ones . What I was wondering was if I build with a 7 speed one will the cones/spacer/locknuts etc. be the same when I acquire a 8 speed freehub and the different width be the overhang. This would mean I could assemble a hub now to start on the lacing and at a later date just whip the freehub out and bung a 8 speeder in.
I could pull another wheel apart and use that free hub but was trying to avoid that.
Anyone ant to swap some 7 speed ones for 8 speed ones?

[Brucey]

7s hubs come in 126, 130 and 135mm variants. They are all approximately the same width from the right flange to the right locknut, and this measurement is about 3 or 4mm less than the equivalent 8s hub which come in 130mm and 135mm flavours. So 7s wheels have less dish and are a fair bit stronger than the same width 8s hub.

cheers

[SilverBadge]

Speaking vaguely, with primary reference to Ultegra 6401/2 (early 90s):
The 130mm 8sp hub has the same hub body as the 126mm 7sp. With the RH cone at the outside of the freehub body, the distance between cones increases, though this negates the need for extra spacers. If memory serves the 130mm LH side has one slightly thinner washer c.f 7sp, suggesting that the freehub is nearer an extra 5mm, and minor need to lose some LH width.
I also had an XT 135mm 7sp hub - this had 5mm extra in LH spacers. Having converted an 8sp 130mm hub to 135mm I now have a 7sp 130mm from the leftover parts.
My assumption is that the various hub widths are all assembled with the cassette and top cog close to the RH locknut and then use spacers as required on LH to make up the required width - this will minimise the dish the wheel requires, though as a consequence any change of cassette width necessitates redishing.

[mattsccm]

Laced it up with a 7 on and will mess about moving it side to side when I find a 8 speed freehub.
Ta anyway.

[531colin]

Not sure I understand the question here, but I forsee a problem which may be real or imagined......
I don't think every freewheely bit will fit every alloy hub shell.....will it?..... Do the splines differ between different hubs?

Apart from that, an 8 speed freewheely bit is wider than the equivalent 7 speed one (by one sprocket and spacer, about 5mm?)
and I think the spoke flanges are all the same distance apart, and the width differences between various speeds and OLNs is adjusted by spacers on the left.

Ah,,,,too late, I see......

[mattsccm]

I was thinking about future issues when setting the RHS cones and locknuts etc I would have to swap them when changing to an 8 speed freehub. Just put it on hold apart from lacing until I can scrounge one from a shops bin.

[ardeidae]

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[Brucey]

yes the splines on a shimano hubshell can vary but the primary variations are to be found in

- Dura Ace hubs (they do their own thing)
- more recent designs that use oversized aluminium axles in the rear hub
- the budget hubs in the FH-RMxx series

outside of this, it is odds-on that the freehub body (6s, 7s, 8s etc) will bolt up to another shimano hubshell.

The snags are that

a) the RH seal can vary considerably, often requiring that the dustcap is replaced in the end of the freehub body

b) there is sometimes a washer between the freehub body and the hubshell. This stays with the hubshell.

c) the cones, locknuts and spacers will need revision. There is less room for a 7s seal vs an 8s seal.

On the latter point the 'complete hub body' i.e. the hubshell with the centre part of the freehub fitted (but less the outer, moving part of the freehub body) is the same length whether it is 7s or 8s. This means that when going from 8s to 7s, you will need to remove an axle spacer on the RH side, and/or find a slimmer locknut/cone. Some 8s hubs have only a long cone and thin locknut fitted. I have occasionally shortened the RH cone in order to make a conversion to 7s, and ground two flats on it for the cone spanner.

BTW although the spline length is a little more on an 8s freehub body, you will often find that a 7s freehub body is not so much shorter overall as you might expect. This is often because the #1 sprocket is set a little further away from the spokes in a 7s hub. Again I have occasionally machined a 7s freehub body on the LH side so that the splines are between 7s and 8s in length. If fitted with a dished #1 sprocket, such a freehub body will accept 8 sprockets at 8s spacing or 9 sprockets at 9s spacing, but on a hub that will build to 126mm without a stupid dish.

The caveat is that the #1 sprocket must be large, and the rear mech of slim design, else the rear mech will tangle with the spokes. [This approach is otherwise similar to shimano's 10s/11s MTB approach, but with a slightly shorter spline.]

Also, some dish improvement is usually possible by simply respacing until the chain is almost touching the inside face of the RH dropout in top gear. If you do this, note that not every wheel will come out of every frame with slotted dropouts easily, because the smallest sprocket will often tangle with the end of the chainstay.

If you revise a 7s hub thus, and build it to 135mm, it can be built almost dishless, which makes for a super strong touring wheel.

cheers

[ardeidae]

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[Brucey]

Brucey, much obliged for your reply. I hope it will be useful for lots of other people considering the effort that you put into it. Great info but not even nearly straightforward or practical or economical then. Oh well, back to my original plan. Thanks again.

well I suppose it depends on your perspective.... removal of the dust shield from the freehub body is required when you re-shim the bearings anyway, and isn't terribly difficult.

Respacing the axle to suit is more tiresome than anything else; I just count my blessings that shimano freehubs can be respaced; most other hubs don't allow this. At most I'd expect you to have to buy one cone for the RHS, and that is if you can't be bothered to shorten one.

Overall I'd describe what is necessary as only a little more effort than is required to service the hub properly. I've probably made it sound worse than it really is....

BTW very few of the freehubs that I use have not been fiddled with in this (or similar) fashion; there are almost invariably aspects of the spacing which can be adjusted so as to significantly improve wheel dish and therefore increase reliability and/or allow the use of lighter rims etc without troubles.

BTW it occurs to me that you can probably make a hybrid body (i.e. one that is between 7s and 8s in spline length, to accept a 9s cassette with a dished #1 sprocket) by shortening an 8s one (by about 2.5mm would do it). Aside from the usual axle respacing issues, I can see two difficulties with this; first, the lockring threads inside the freehub body may not be quite long enough; it may be necessary to use a shortened lockring, or small spacer. Second, if you want to use a very small top gear sprocket, the outside of the freehub body will probably need a tickle with the grinder too, (in order to replicate the original shoulder) else the top gear sprocket won't fit correctly.

I know that you can't shorten an 8s body by 5mm (and therefore turn it into a 7s body) but a smaller length reduction is almost certainly possible, and will give a small (but significant) improvement in wheel dish.

cheers

[ardeidae]

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[Brucey]

Are the 5500's any different regards doability? IYDMMA

http://bike.shimano.com/media/techdocs/content/cycle/EV/bikecomponents/FH/EV-FH-5501-2170_v1_m56577569830608912.pdf

shows a standard hub body interface, and there is even a 3.7mm wide spacer that can be removed from the RHS of the axle. Similarly there is a spacer on the left as well; I think you will need to remove both these and then put some thinner spacers back to get the correct width.

If the RH side seal becomes problematic, it is often possible to fit a part such as Y3CR09000 or Y3CR08000 into the freehub body. This type of seal is intended to seal directly onto the cone itself (not where the flats are, obviously) or any nearby spacer, provided the diameter is about 17mm. Seals of this type cost less than £3 and can be ordered from any shimano dealer, or bought from suppliers such as SJS.

BTW I recommend that you use a semi-fluid lubricant inside such hubs; the seals need a fluid film on the seal lips to last well; without it the seal lips wear away and then water can get into the hub more easily.

hth

cheers

[recordacefromnew]

A further question.

Can 105/Ultegra rear hubs 5600/6600 onwards be respaced to 126mm? I have got spare 7sp HG freehub bodies.

To my mind whether it is 5500, 5600 or 6600, they are all eminently respaceable to 126mm with a 7sp freehub, for the simple reason that we are talking about shrinking only 2mm a side, while a) a 7sp freehub is more than 2mm shorter than the original 8/9/10 one, and b) all these hubs have ample sized spacer on the left to be thinned out by 2mm.

As a matter of fact, to minimise dish for a stronger wheel, you should find that once the 8sp freehub has been swapped with a 7sp, the oln distance ought to be close enough to 126mm without messing with the spacer on the left.

The key question is in fact what the 7sp freehub model is, because this determines whether it has the same typical hub/freehub interface, and whether drive side spacers and seals of the 8sp hub can be utilised if the 7sp freehub did not come with a matching set.