Harold74

Big Picture Plan

I want to take an FH-HB6500 hub (9sp / 130 OLN) and lace it into a vintage wheel (7sp / 126 OLN). Based on my measurements of the hub flange spacing and hole circle diameter, this should be possible from a wheel strength perspective. These hub dimensions actually match those of the existing 105 7spd hubs that I will be replacing.

The Detailed Plan

1) Remove the existing 9 speed freehub body and replace it with a new 7 speed freehub body.

2) Remove the existing 130 OLN axle and replace it with a new 126 OLN axle.

3) Do some spacer voodoo to get the hub laterally positioned properly within the wheel.

4) Dish the wheel to get the rim centered on the frame.

The Question

Does anyone foresee any hiccups that would prevent my executing this plan successfully?

Harold74

Huh, I see your point. This will work even better than I'd anticipated as I was bracing myself to have to purchase a $168 CAD axle spacer kit by Wheels Manufacturing. If the cassette width difference is 4.5 mm, as I believe that it ought to be, I'll only be out by 0.5 mm.

Thank you so much for your input Bill.

HillRider

Actually, you don't even need to purchase a new 126mm OLD (137mm length) axle. Just cut 4mm off of the 130mm OLD (141mm length) axle you have. Axles cut easily with a good quality hacksaw blade followed by smoothing the cut with a fine file. Thread one of the locknuts on the end before cutting so removing it after the cut will clean up the thread lead.

Harold74

Related question: mathing things out, I feel that it is probable that I can move the rim over the requisite 2mm without getting new spokes. Does that sound right? It doesn't seem to take much nipple adjustment to shift a rim over a couple of millimeters.

KCT1986

Do you already have a 7 speed freehub body that will fit the FH-6500 properly?

The 6500 body is different from the common bodies that Shimano uses. Below is the 6500 body and the more common type (pictured is a 9 speed FH-4500 but most 7 speeds are the same in the rear), notice the difference in the depth in the attachment area.




There are 7 speed bodies that have a similar shape to the 6500, but not many. Most will more similar to the 4500. Possibly a body from FH-M732, XT from 1990s.

Harold74

Ughh... there's the rub. I have a Deore DX 650 hub as the freehub body donor. It looks just like the one shown below. Is there a way to ascertain the compatibility without taking the thing off? I'm guessing that I've got the wrong kind.

KCT1986

Not sure what type of body the FH-M650 you have uses, probably the common shallow mount type.

Also, dug up some pics from my old computer and must cancel the possibility of a FH-M732 being a replacement.

Although the M732 is deeper, the shape may not fit the 6500 shell's recess. The shell has a different taper along the edge of the recess. See the arrow and angled area part way down into the recess



The M732 body is relatively straight in the area that would fit into the recess of the shell and probably will not clear the taper in the 6500 body shell. As seen in my earlier post the 6500 body has a step in the area that would fit into the recess. From the 7 speed bodies that I have seen, don't recall any bodies with the needed shape.

Hondo6

Per the Shimano EV for the FH-6500, that hub has a 4.8mm spacer on the NDS between the locknut and cone. Seems to me the following should work fairly well:

1. Replace that spacer with a 1mm washer.
2. Shorten the existing axle by 4mm.
3. Add a 4.5mm spacer behind the 7-speed cassette to account for the difference in freehub length.

This should result in a hub with an OLD of approx 126.2mm. The spacer behind the 7-speed cassette should place the cassette in the expected lateral position.

Advantages are no searching for matching compatible 7-speed freehub required, as well as no transplant needed. Disadvantages are possible need for new spokes (I'd guess the existing spokes would work OK, but you'd need to do the calcs to be sure) and a somewhat more highly dished wheel after you build it.

Your bike, so your call.

rccardr 

You might do better by just using the donor hub if it’s in good shape. Assuming it’s 135mm OLD, there should be a large spacer of 8-10mm on the NDS side. Remove that, shorten the axle as described, amd you have a 126OLD rear hub.
Alternatively, use a later 6700 or 7700 hub, that shorter freehub will work just fine. Same shallow design, remember to use the thin freehub washer.

maddog34

Loosen the side you're moving away from first, tighten the side you're moving towards second.

go with one full turn each time through this procedure.... i use the valve stem hole or the rim joint "label" as a reference point.

Check the progress after each set of loosen/tighten...
getting close? go to 1/2 turn per spoke.

tFUnK

Haven't fully thought this through but here's what I'd do:
- keep the 9sp freehub body. A 7sp cassette should slide right on. You'll need to put a spacer on before installing the cassette. Exact spacer thickness escapes me, basically the difference between a 7sp cassette and an 8/9sp cassette.
- do the spacer math inside the hub - most likely if you take off the 4mm difference from the NDS side spacer, you'll need to re-dish slightly. Do a quarter turn per side (loosen from NDS, pull from DS), and see where you end up.
- keep the existing axle if you have thick enough dropouts to accommodate. If the dropout is thin and the ends of the axle protrude beyond the dropouts, you can use a 20mm OD x 10mm ID washer to take up the excess (exact thickness TBD, maybe 2mm each side), then install the QR skewer. The washer goes on the outside of the dropouts but under the QR clamp surfaces.

rccardr 

Most wheel builders consider the use of an 8-9-10 speed freehub in a 126mm OLD wheel to result in a very weak end product, as it moves the center-to-flange distance too far to the drive side.
Can it be done? Sure...but I'd be very concerned about building/using a wheel with that much dish.

icemilkcoffee 

Agreed. The only way it could be acceptable is if you use an OC (asymmetrical) rim.

Harold74

I've been noodling on this concept since it was suggested above. Sticking with the 10 speed freehub body would definitely steepen the angle of the drive side spokes. According to my rough calculations, however, this would basically put the drive side spoke angle right where it is on a modern 11 speed / 130 OLN setup.

1) Do you agree?

2) If you do agree, is there a reason to be any more concerned for the wheel setup being proposed than we would be with riding an 11 speed / 130 OLN wheel?

Harold74

That is indeed something that I'm considering. Unfortunately, my 7 speed hub is 36H while the rims that I'd like to use are 32H which matches the 6500 hubs. Oh well, the money that I waste on extraneous bike parts is still cheaper than an addition to cocaine or golf.

rccardr 

The factual numbers prevent me from agreeing.

Although 11 speed freehubs are about 2mm wider than 8-9-10 speed freehubs (35.75 vs 34.95), the actual hub bodies are slightly different. So the center to flange distance only decreases from 16.8mm to 16.2mm, which is not significant relative to the strength of the end product.

In other words, a standard 11 speed wheel is pretty much as strong as an 8-9-10 speed wheel.

Edit: Aha, I see there’s a hub-rim hole difference. Maybe then the best thing would be to just source a 32 hole 126mm 7 speed HG compatible rear hub. They are out there in the USA, mostly 90’s Tricolor 6402, 105 1055. Deore from that period was just a quality road hub with a big old 9mm spacer hanging off the end of the NDS- remove that and it’s magically 126mm wide. There would be shipping cost involved, but perhaps a friendly BF member has or can locate one at their co-op for cheapies.

Harold74

Thanks for that. If you're willing, I'd welcome a check of my math:

11 SPEED WHEEL w/ 130 OLN

43.5 mm chain line - 39.0 mm cassette width / 2 = 24.0 mm distance from large cog to frame centerline. <-- I take this to be a measure of drive side spoke angle unless the cog to flange distance changes from hub to hub.

10 SPEED WHEEL w/ 126 OLN

43.5 mm chain line - 37.2 mm cassette width / 2 = 24.7 mm distance from large cog to CL.

This is what leads me to believe that the 10 speed w/ 126 OLN would be as strong as the 11 speed w/ 130 OLN. A trivial amount stronger actually.

Where've I gone wrong?

Harold74

Thanks for the recommendation. I'll look into that but, mostly likely, will do one of the following instead:

1) Find a set of 36H Mavic Open Pro to pair with the Deore hubs. These seem to appear frequently in the local used market and aren't even prohibitively costly brand new.

2) Find a set of 36H Mavic Open Pro to pair with a 7sp 1050 free hub that I've got a bead locally. I'll probably purchase this as a backup plan if nothing else. My only real objection to this is that there is no matching front hub and the hub is non-shiny (I'll live).

I really wanted to use my sexy Ultegra hubs for this build but, alas, I guess they'll have to await a future project. In my travels here, I've discovered that:

a) 11 speed freehub bodies are not compatible with 10 speed freehub bodies and;

b) 10 speed freehub bodies are not compatible with 7 speed freehub bodies.

In future, it seem prudent to just assume that no freehub bodies are compatible unless I've good reason to think otherwise.

That's good to know as it's something that I've been curious about. I did read somewhere that the old Deore hubs were really built for 126 wheels and were initially just adapted to 130 wheels with spacers.

Are the old Deore hubs different from road hubs in any meaningful way? Larger bearings? Heavier? The hub came off of a 1991 Miyata 1000 which was sort of like an early generation mountain bike as you surely know.

icemilkcoffee 

I don't have solid numbers in front of me, but the Shimano 10 speed and 11 speed cassettes actually have the back side dished in slightly, such that the biggest cog will overhang the hub flange somewhat. So it's not a straightforward calculation of large cog to center-line.

rccardr 

Large cog location relative to wheel build strength is not as critical as flange distance to centerline. In your illustrative case, you'd put a 4.5mm spacer behind the large cog anyway.
In simple terms, the closer the hub centerline is to the DS, the weaker the wheel. Removing 4mm from the NDS essentially moves the center to flange distance that much to the DS.
4mm is a LOT.
To compare a standard 8-9-10 speed hub to a standard 11 speed hub, Google 'Shimano Freehub Widths' and go to the Images tab.
There's a great chart there that shows the difference in hub offsets side by side (unfortunately the file format won't copy here).

EDIT: There are 7 speed freehub bodies that are compatible with 10 speed hubs, I just don't know all of the numbers for them. That 1050 freehub is indeed 126mm wide but is UG only, which will further complicate your life. Open Pro rims are excellent IMHO and if that solves your problem, well, great. Believe you are correct with regard to early 90's Deore hubs, but they were 135mm wide for MTB frame applications. Later on they became their own line and not modified road designs. I have an early 90's Deore rear hub in front of me pieces on the bench, and everything internal looks just like a road counterpart- bearings, etc. There may be some internal freehub differences in pawl size or something, but if so it shall remain a mystery to me.

Harold74

My point was that, to some degree, large cog location is a proxy for flange distance to centerline. But, as I mentioned, that's only true so long as the large cog to drive side flange distance is constant. And icemilk has indicated that it's not. I'll measure the cassette dish when I get home from work and see if that's enough to matter structurally.

icemilkcoffee 

Some 7 speed freehubs come with a shim. Sometimes the 6500 hub also come with a shim between the body and the freehub. So play with the shims and see where it gets you.

Harold74

So I did this. The upper is a seven speed cassette on a seven speed hub. The lower is an eleven speed cassette on an eleven speed hub. The difference in the dimensions from the insides of the flanges to the insides of the large sprockets are less than 1mm (larger for the seven speed). So the lateral difference in the drive side spoke positions at the hub should be 1.0 mm - 0.7 mm = 0.3 mm. Relative to a 20 mm +/- flange to frame centerline distance, that's less than 2%. I can't see how that would make an appreciable difference in wheel strength.

Tentatively, my verdict is that these two wheel combinations would be of equal strength:

A) 11 speed hub + 130 OLN
B) 10 speed hub + 126 OLN

It would seem that Hondo's proposed method checks out (thanks for that). I still may not be brave enough to try it but but it's nice to know that the option has legs.

Thanks to everyone who has contributed to this discussion, it has been immensely helpful.


I

Harold74

Sure. Measuring to the inside of the flanges of the 11s & 10s hubs shown below, we have:

11s = 50 mm
10s = 48 mm

So that's a difference of two millimeters. And that comes out in the wash when one considers that the dropout shifts inwards 2 mm in going from 130 mm to 126 mm.

By this math, these two options are identical in terms of wheel strength:

a) 11 speed hub (FH R7000) w/ 130 OLN
b) 10 speed hub (FH 6600) w/ 126 OLN <-- note that I mistakenly referred to it as FH 6500 previously).

I agree with the concept but feel that you're asking the wrong question. The relevant question here is not "do steeper drive side spoke otherwise weaken a wheel?". They absolutely do.

Rather, the relevant question is "will the proposed wheel build possess adequate strength?". And the answer to that would seem to be yes unless someone is suggesting that ubiquitous, 11s w/130 OLN wheels are insufficiently strong.

FWIW, this is a vintage racing bike build. There will be no fully loaded touring happening on these wheels.

rccardr 

You asked for people to Vet Your Plan.
They responded with proven facts about relative wheel strength.
Your responses indicate that you just want to do what you want to do and don’t care about facts.
You present all sorts of irrelevant measurements and ignore the relevant ones.
If you don’t want to accept the facts from people who know what they are doing, well, build your wheel and see what happens.