wesley77803

Sheldon Brown https://www.sheldonbrown.com/k7.html#transplant, if you have a 7 speed free hub (126 mm) you can use 8 sprockets from a 9 speed cassette with the 9 speed spacers, or 9 sprockets and spacers from a 10 speed cassette. It is a way to get extra speeds without modifying the hub or spreading the frame. Of course, you do have to change the shifter from the original 7 speed to whatever the original cassette was (9 or 10 speed).

SeattleJG

Hello everyone, yes, I know this is a very old thread. I have a 1991 Trek 2300 Pro (the one with carbon straight tubes and aluminum lugs/fork/triangle). My bike has a measured 126.1mm distance between the rear dropouts with no rear wheel mounted. I had the original Shimano 600 7-speed downtube shifter setup. The bike was great, but I've been hoping for an update to brifters.

That led to a rabbit hole of planning, reading, talking to mechanics and buying parts. I found a great deal on a good condition full Shimano Dura Ace 7800 series 10-speed groupset. From this thread and many others and Sheldon Brown's archived website, I assumed I was going to start with a "9 out of 10" setup since I would need to measure my original hub body length and start planning for new washers and maybe a narrower cone nut on the drive side etc. to fit my 126mm OLD. I bought a brand new 10-speed cassette (Ultegra 6700 11-25) and confirmed that I could just take off the 11 tooth cog.

Believe it or not, after examining the Shimano literature, the part number for the 12 tooth cog that is the second smallest cog on the cassette I bought is the exact same as the smallest cog of a 12-X Ultegra 6700 cassette, knurled to mate with the lock ring and everything! The only difference is the lock ring is smaller for an 11 tooth cog, so I just bought a 12 tooth lock ring and thought I was ready to go for a 12-25 9 sprocket cassette with 10-speed spacing. When I started the transition to my new groupset I took off the rear wheel and took off the original 7 speed cassette. I also took off the clear plastic protector ring between the largest cog and my rear spokes.

So I decided to try the new cassette without the metal spacer washer that comes with it that one is supposed to use for a 8/9/10s hub body. It fit great but was *too narrow* with my intended "9 out of 10" setup (i.e. there was space between the smallest cog and the lock ring!). So I just slipped the 11 tooth cog on, switched lock rings back to the 11 tooth lock ring, and voila! Everything fit! I'm not sure how or why, but I didn't even touch my axle/spacers/locknuts/wheel dishing etc. Examining it more, it appears that the largest cog is suspended toward the middle of the hub (the largest 3 cogs are all on a central tree, I forget what it's called, on this cassette), and this is probably is what allows the extra gear space.

I've set up the bike completely and was stunned that I didn't have any derailleur or chain interference problems with the rear triangle or rear spokes. I've done multiple 10-20 mile rides to get things dialed in and I'm super happy. Anyhoo, I just wanted to share what I was expecting vs. what my reality is currently, i.e. with the Dura Ace 7800 groupset (shouldn't really make any difference vs. any other 10-speed group?) and the CS-6700 Ultegra 11-25 10-speed cassette, I have a working 10 speed setup on my original 7 speed Shimano 600 hub/hub body WITHOUT MAKING ANY CHANGES TO THE 126mm OLD or WHEEL DISH!

70sSanO

So what you are saying is that you installed a full 10 speed cassette on a Shimano 600 FH-6401 rear hub.

John

SeattleJG

Well, apparently I can't post pictures because I haven't made 10 posts... darn. But yes, that's exactly what I'm saying. I think the key is the choice of cassette. There are probably many that do this (I'm not a cassette expert), but the CS-6700 spider holds the largest cog inboard of the innermost edge of the hub body. I can't see any other reason why this works.

cb400bill

Pic Assist. https://www.bikeforums.net/g/picture/22240191

dddd

Wow, I've got a minty Klein Performance with 7s Ultegra and will have to try this!

Stay tuned.

70sSanO

I wouldn't hold your breath until you understand exactly what SeattleJG was using in the first place.

To start off with, Trek made 2500, 2300, and 2100 frames in 1991. As far as I can tell they are the same frame with the only difference being the component group. By 1991, "most" mfg were making their high end frames at 130mm, but at the very least 128mm so they could accommodate either a 126mm or 130mm OLD.

The 1991 2500, 2300, and 2100 came with 8 Speed Dura Ace, 7 Speed Ultegra, and 7 Speed 105, respectfully.

Case in point, I have a 1991 Specialized Allez Epic of similar construction with 7 speed 105. It came with 8 speed Dura Ace, 7 speed Ultegra, and 7 Speed 105.

The 8 Speed Dura Ace was 7403 and has an OLD of 130mm.

If I measure the top of the dropouts I'll get 126mm, but where the dropouts slide it is 128mm.

I have no clue what freehub or freehub body is on SeattleJG's bike. I'm somewhat skeptical that after 30 years of people converting from 7 speed, that the fix was as easy as using a CS-6700. And he is the first person to discover this. There is no knowledge if the original freehub body was ever replaced somewhere along the line. The only way to tell is to measure the length from the cassette stop to the end of the freehub. It is also a tough sell that a 1991 UG/HG freehub body can accept an 11t since there is no relief for that size cog. I'm guessing the freehub body was replaced along the way and a spacer was placed behind the 7 speed cassette and it fits into the frame because it is 128mm.

But if it is true, it is great news and I hope no one tells miamijim that his effort was a waste.

Many late 80's/early90's bikes, maybe even the Klein Performance, were made with 128mm dropouts. If it has a 7 speed freehub body, I have my doubts you'll fit a 10 speed, but it is possible to replace it with an 8-10 speed body... been there, done that.

John

Edit Added: Think off all the steel 126mm frames that have been cold set to 130mm to accommodate more that 7 speeds.

dddd

Firstly, thanks, SeattleJG (and CB400bill).

Ok, for starters I did mention 1992 as the date by which virtually all road frames were made to 130mm. My own Klein Performance date-codes to late 1989 and is solidly at 126mm and with Ultegra hub measuring same.

All of my road and mtb 10s cassettes have their rear mounting surface recessed about 2mm from the face of the largest cog, positioning the cogs that much closer to the hub centerline.

I grabbed several 7s wheels to test out with my 12-30t 10s Ultegra cassette and fitted the cassette to all of them.

All four hubs gave more than 3mm clearance from the face of the smallest cog out to the serrated locknut teeth on the axle.

The modest HB-RM40 hub (a later model perhaps?) is the best candidate of these four 7s freehubs because of it's having the best/most purchase with the splines of the smallest cog (it's splines are not threaded for UG cogs).

The Hyperglide-C hub fared the worst in that regard because the ends of the splines are shortened significantly, but it still engaged the splines even before I secured the lock ring.

The other two hubs (105 and Ultegra) both had UG threads cut into the end portion of the splines, which somewhat reduces their load-carrying area (if perhaps not as bad as the shortened Hyperglide-C freehub body).

A steel lock ring must be used, because of the minimal threading engagement with any of these hubs. There is not much more than one turn of engagement, but thankfully the freehub bodies here are all steel instead of aluminum.

There are steel lockrings from other brands having a bit more threaded engagement than Shimano's.
My own lock rings from IRD, SunRace (and even a Shimano-compatible Suntour specimen) all appear to have longer threading.

A down-sized 11t steel lockring seemed pretty good as it nested into the 12t smallest cog, adding another half-turn of threaded engagement (this is the lock ring used in my photo below on the Klein's 7s Ultegra hub).

Again though, there is a full 3.5mm of locknut protrusion out past the face of the smallest cog! Amazing.



Ok, all fitted up for testing and the derailer cage appears to still have 2-1/2mm of clearance to the spokes.
The top pulley bolt was ticking against the spokes, but only because some buffoon (me?) fitted Bullseye pulleys that weren't spaced out quite the same as the originals.
Still using the original 7s chain and shifter, and it indexed nearly ok during the trip across the 10s cassette (after I backed out the lo-limit screw two turns). Clearance to the dropout is adequate even with this 7s-width chain.



One more thing is that I do worry that this arrangement might suffer material failure in the area of the smallest cog if used under hard conditions of smaller chainrings and/or heavy loading while using the small cog.
Bigger, harder-riding riders with smaller chainrings in hilly terrain beware! Failure could lead to crashing and death.

70sSanO

I’m not convinced yet, but congratulations!

Since I have a lot of parts, I couldn’t get a CS-5700 on a 7 speed FH-1055. I can get 9 cogs, but not the 10th; doesn’t engage. No splines left on the freehub body.

John

dddd

That is quite surprising, since my own CS-6700(?) 10s cassette fits and engages well on my own FH-A550 and FH-6401, etc., ALL of my 7s freehubs.
My SRAM and IRD 10s cassettes as well (all have their largest cogs mounted on spider(s)).

Does your 10s cassette have the mounting surface recessed 2mm from the face of the largest cog?

(105/5700-equipped bikes often came with cheaper, all-steel cassettes (...perhaps having no recess/offset at the largest cog?).

Also might be the case that the smallest 10s cassettes have no offset/recess going on because of spoke-clearance issues(?).

70sSanO

I didn’t measure the offset, but the largest cog does extend beyond/farther in than the spider. I’d guess the cog thickness which is less than 2mm.

I’m glad it is working for you. It is just odd that it has been lost on so many mechanics over the years.

I probably won’t be convinced since over the span of 30 years a lot of freehub body swaps could have taken place. I know 7 speed freehub bodies have a cassette depth of around 31mm, and as you brought up Hyper-C loses about a mm of spline. Hard to do the math and fit everything into 126mm.

John

dddd

It'll be no big deal for me to now put a 10s chain on my Klien and give it a test-ride in friction mode.

I also bought some clearanced Tiagra 10s STI levers, and found a pair of shop-discard Ultegra 10s levers (with hidden cables). They're all waiting for suitable recipients such as this Klein.
I also stocked up on sale-priced 10s, 39t inner chainrings as well, before the pandemic.

dddd

I've got the 10s cassette on the stock(!) 6401 7s hub and with a 10s KMC chain installed. It all shifts perfectly after I replaced the cable housing and fitted a 10s Dura-Ace rear derailer. Using the DT levers in friction mode for now and it's very smooth with no clearance issues.

I had to use the full 116L(!) to accommodate the 52-30t crossover ratio, because of this Klein Performance's enormously long chainstays.

I'm now waiting for the smoke to clear a little before taking it for a hard test-ride this afternoon.

icemilkcoffee 

Ok. So you are acknowledging that the 10sp cassette is indeed wider than the 7 sp cassette and there is barely enough threads to screw the lock ring on.
But you know what- you are on the right track. Some people shave the back of a 11speed cassette to make it fit a 8/9/10 speed hub. You can probably shave a little more off the back side of your 10sp cassette to make it fit the 7sp hub. A bike shop with a head tube facing tool can probably do this for you.

dddd

I finally test-rode the actual bike with the 10s transplanted cassette on the stock 6401 7s freehub, and can report that there seem to be no issues in terms of function while hitting the steep hills surrounding me here.

I used a SR Suntour 11t cassette lockring because it engaged the most threads by nesting into the recess in the 12t smallest cog. I did also look around for similar lockrings that might work best with this conversion and noticed that my SRAM alloy lockrings appear to also have more/longer threading on them.

Anyone doing this conversion should be aware of how much threaded engagement that they can get between the lockring and freehub body. Most normal setups seem to achieve two full turns on the lockring whether it's steel or aluminum and whether the freehub body is steel or aluminum, but use your own judgement as this could be important in terms of safety and reliability.

This is kind of a game-changer for the couple of 126mm aluminum bike frames that I have waiting for a future build. My old 1990 Specialized Epic also uses a 126mm 7s hub so might be another good candidate for a 10s cassette upgrade. My Klein and perhaps my 1980's Calfee (20th production Calfee ever built) will also be getting upgraded with 10s shifters.

70sSanO

I went back and looked at the 10 speed cassette. Even though it was off a 105 5700 drivetrain, the 13t dies not have recess so the 12t can go .5mm deeper on the freehub body. So it is probably a SRAM 1050 and not a 5700.

I “think” I understand what you are doing as I have seen 2nd position cogs with a recess for the 1st position to nest. Your 12t is probably sliding just enough to catch the splines but not enough to fully seat as it would on an 8-10 speed freehub body. Maybe 10%-15% of the total cog width including the built-in spacer is being supported by the freehub body. The rest is just hanging off the end.

This is why you mentioned material failure under high stress conditions for the small cog since there is nothing but air under a good portion of that cog. It is also why you are using an 11t lockring. An 11t cog sits with the built-in spacer in the splines and the cog width sits on the end so the 11t lockring has more threads and sits deeper to ensure enough threads are engaged.

The only question you have is whether those 2 threads will support the directional forces that are placed on that small cog. Only time will tell. But as food for thought, Hope makes a 10 speed cassette that has a 9t. Obviously there is no way a 1st position 9t cog will fit on any freehub body. It sits outside of the freehub body, but it is part of a 5 cog cluster made from a solid piece of steel. That might be overkill, but using a lockring to support a cog and torque it to the freehub body might just be an accident waiting to happen.

I applaud you for getting it to work. And I hope it works for thousands of miles.

John

70sSanO

There is a twist to your setup that might be beneficial. I have used a UG 1st position cog with a HG cassette with mixed results.

I don’t have any 10 speed cassette bikes, as opposed to real 10 speeds, as I have not found any value in them for me. However, if you can get a UG 12t, I think they made one in 34.6mm, sand it down to give the proper spacing, thread it on to your 6401 UG/HG freehub body to hold the cassette tight, “and” then add a lockring for a bit of extra security.

The issue I had with a UG 1st is the teeth are so tall that shifting on and off was not as smooth. I had contemplated modding the teeth, but I found a 14t HG 1st position with a built in spacer. Friction shifting might make things shift better.

Since I have a couple of Cannondales this thread by miamijim was invaluable for me to understand how to fudge the OLD to fit into 126mm dropouts. I even copied and pasted it into a Word document. The reality of what I discovered was the answer isn’t necessarily getting to 126mm, but getting close. My magic number is 128mm or less. On a Shimano freehub it is pretty easy to find a couple to a few mm’s. 2mm’s is nothing especially since frame mfg’s allowed for that much on their late 80’s frames spaced to 128mm.

John

dddd

Yeah John, people have used UG threaded top cogs to put 7s cogs/spacers on a 6s freehub, but I warned them that the torque being applied to the threads would lead to failure since only the treads are taking the drive torque on the small cog.
With this "10-on-7" setup, there is a good couple of millimeters of actual spline engagement going on (that I feel is going to be many times better than a couple of threads in terms of handling pedaling torque).
The internal splines in the 12t smallest cog only have barely 4mm of width, and remember that these were often used with alloy cassette bodies having far weaker splines than the Shimano steel freehub bodies.
I note also that mere <1.8mm-wide cogs in much larger diameters than these top cogs sustain their much greater driving torque across that same engagement width on alloy freehub bodies, with perhaps some degree of digging into the softer body over time.

Was there perhaps a 6402 model hub that did away with the threads on the external body splines? That would be a good hub as would any other un-threaded-spline freehubs that pre-dated the "Hyperglide-C" series (with their shortened splines). I do have one here like that which is an HB-RM40 Hyperglide-only freehub.

Any road freehub later than 1995/6 will typically have the shortened splines (that made room for an 11t cog's integral reinforcing ring).
MTB freehubs got the Hyperglide-C shortened splines beginning in about 1993/4.

I should mention that "nesting" an 11t cassette lockring into a 12t cog (as I did) means that the retaining teeth on the lockring flange will meet only a smooth surface on the cog. So one must use LocTite on cleaned lockring threads to prevent it's possibly backing out imo.

I guess that my last words on this should be to advise using judgement when assembling this setup.
In other words, the choice of using threaded vs. un-threaded freehub body, achieving some decent amount of lockring engagement, and the amount of working chain tension (chainring size, rider weight, terrain, etc.) will all be critical to how well that such a setup might hold up in use.

dddd

Shimano's largest 11s, 11-34t road cassette has additional "flange overhang" on it's back side, since the larger 34t cog diameter gets the derailer cage further from the angled driveside spokes.

So this big 11s cassette can also be fitted to the older, narrower 10s freehub bodies (at least the steel ones with normal-depth splines). A spacer is used with this particular size cassette if it is to be used on a longer 11s freehub body.

So obviously I was curious if/how the narrower 11-34t version of Shimano's 11s road cassettes might fit on the 7s 6401 freehub!

It fits, but the last cog gets no purchase on the ends of the splines. Even with the HB-RM20/40 freehubs with full-length splines and no threads, there was no engagement of the splines.
I fitted the 11-34t cassette to an 8s Dura-Ace freehub and the 11s cassette fit perfectly in every sense. But even this narrow 11s cassette seems to need most of the extra 3.8m of spline length that the 8s hub has in order for the 11t cog to get the needed purchase on the splines.
Close, but no cigar.

So it seems like only the 10s cassette is the lucky one that is narrower at it's mounting than the 8s, 9s and 11s cassettes, and narrow enough to work on a 7s freehub.

SeattleJG

Hi everyone, I'm glad this is generating so much discussion. I had written the following on Friday, but got the "you can't post more than 5 posts in 24 hrs regulation..."

Ok, so I took photos yesterday and have uploaded them to an album, but still can't post them due to my 10 post limitation. Can someone do what they did for my first photos and help me get them on here?

It looks to me like the bike is a true 126mm gap between the dropouts (125.41mm per my calipers). It also looks to be a stock FH-6401 and original 7-speed UG/HG hub body (see pics and measurements). The actual OLD for this wheel setup is ~125.5mm per my calipers.

I will let all of you judge based on the photos what's going on and if you think it's safe. My take is that I do have an acceptable amount of the 11 tooth cog spline slots filled with the threaded UG/HG splines. There are at least 3 full threads of the end of the UG/HG hub that are engaged by the 11-tooth cog (see pic with 11-tooth cog removed), since it sits in the recess of the 12-tooth cog There is about a 1mm gap without the lock nut tightened (see zoomed in, lightened pic to see the gap), but the 11 tooth-specific lock nut has a considerable amount of purchase on the hub body, so it feels like it snugs down well. It looks like the largest cog (25 tooth in my case) sits about 1.7mm inboard of where the spider sits on the hub.

machinist42

machinist42

70sSanO

Looks great.

If it were me, I’d want as many lockring threads engaged as I could get.

I think Edco makes one that is deeper than a Shimano/SRAM 11t lockring.

John

silferion

Sadly, a decade later, these parts you mentioned are hard to find.

Steel Charlie

About four months ago after reading this I re-spaced a 7403 8 speed to 126. Fits fine and works great.

A super mod that made my day.