Flash

Hello, I'm preparing to execute the Sheldon Brown 8 of 9 on 7 trick on an older Japanese steel frame with 126mm rear spacing.

My plan:

-- keep original rx100 7spd rear hub
-- install 8 of 9 cogs from an ultegra 6500 or dura ace 7700 cassette
-- install ultegra 6500 short cage RD (not strictly necessary according to Sheldon -- apparently the original 7 spd RD will work
-- install Ultegra 6500 double cransket with octalink BB (68 x 109.5)

question: since my rear spacing is 126mm, will I have to somehow compensate for the extra 4mm since Ultegra 6500 was designed for 130mm rear spacing. Put another way, will 109.5 in the front, 126mm in the back work OK in this case?

well biked

One thing I've learned about bb spindle lengths: you can think about it all you want, but there's no way to know for sure what will work best until you actually try it. And a lot of stuff will work, but not necessarily be the best setup.

Bottom line, you're the one with the frame, so you're in the best position to find out if it will work.

dabac

8 of 9 on a 7 is a direct swap, the bike won't "see" any difference in the way the rear wheel and the sprocket cluster sits in the frame.
The RD doesn't care much about the numbers of speeds it's moving over. Unless you're too far off with the chain width( but running a narrower chain in a wider RD is usually OK) or the amount of chain wrap required the old RD should do fine. The exceptions to the rule are the RDs with an oddball amount of travel vs cable pull. (SRAM, some Dura-Ace being the most common examples)
If you're worried about chainline, keep in mind that you're takling about a bike with derailers here. It HAS to be tolerant of chainline error to work at all.

Steev

You didn't mention in your list that you were going to replace the chain. You need to use 9 speed chain as your cassette is spaced for 9 speed.

Flash

Thanks for explaining this. And now for the wildcard. I'd really like to run a compact crank up front, 36-52 is my preference, or the more common 34-50. My cassette would be the 12-27. I've been reading a fair bit about chain wrap and the published Shimano specs. I must admit I'd prefer to run the short cage RD-6500 even though the total chainwrap would be 31t which I believe exceeds Shimano's published specs. In practice, since I meet Sheldon Brown's definition of a competent cyclist ;-), I would never be running small chainring to smallest cog.

If performance will suffer with short cage 6500 under the above scenario, I'm happy to go to long cage 6500. I don't have the parts yet, just trying to get organized.

thanks again

Flash

thanks. Yes, I would have the 9 speed chain

LarDasse74

The only problem you will see is that the derailleur might ride directly on the small cogs when you are in the small chainring/smaller cog combinations - IF IT IS SET UP CORRECTLTY! If you are using a gear combo out of range for your RD you must run the chain so you can use the big/big combination (and sacrifice the small/small) as running too short of a chain and shifing to big/big can rip your derailleur clean off.

Do they still make a medium cage Ultegra? Or XT (same quality as Ultegra, 100% compatible RD)

Flash

Thanks. Any drawback to simply running the long cage ultegra RD 6500?

HillRider

A trivial weight increase and a loss of "image" with your riding buddies but, otherwise, no drawbacks whatsoever.

Flash

This is what I suspected ;-)

Well, since the ultegra components will be going on this old Panasonic bike, my image will be shot even before I get to the assembly stage!

Retro Grouch 

1. You'll need to use a cheaper cassette. Assuming you want to keep the spacing between gears even, you have to remove the biggest cog. Ultegra and DA cassettes have the 3 largest cogs on a carrier so removing just the biggest one would be a project. The first (smallest) cog is unique because it has serrations for the lock ring so I don't think you'll want to remove that one.

2. Don't worry about BB spindle length. It'll be fine. The whole object of the 8 of 9 is to use the narrower 7-speed freehub body so there's no need to change the crankset.

3. You are aware that you'll need 9-speed shifters? That's generally the most expensive component to buy.

TallRider

As has been said above, if your present chainline on the 7-speed system is correct, then it will also be correct on the 8-of-9-on-7 setup, as the rear gears will be in the same spot as before.

Flash

Good point. So, if I snag a HG-compatible 9-spd cassette -- such as the **edit: Shimano CS904 XT: edit** which has 28 and 32 as the last two cogs, I could drop the 32t and still have the 28t. Or I could build my own 9-speed cassette, which would be more fun. The question: are all Shimano 9spd HG cassettes -- Deore, Ultegra, 105 or otherwise -- using the same spacing in between cogs? What about SRAM 9spd? Same spacing as Shimano?


gotcha. So I could keep the Sugino Alp cranks and 52t outer chainwheel and substitute a 36t for the inside (original was a 42t)



Yes, and you are correct on price, at least current e*ay trends

HillRider

Be sure the 28 and 32T cogs are "full plate", that is they are complete cogs with the necessary splines as part of the cog. As RG mentioned, many of the upper level Shimano cassettes have cogs grouped together and riveted to a spider. The cogs themselves are hollow center rings so they cannot be used individually. I believe the CS-M9XX series have several or most of the cogs on a carrier.

I know the 105 level road 9-speed cassette has all full-plate cogs so you have liberty to remove any one you want except the first position. I checked the Shimano web site and the highest level MTB cassette that has all full-plate cogs is the LX (CS-M580).

BTW, "build your own" is impractical as the cost of individual cogs is so high that a DIY cassette will cost several times what a complete one does.

Little Darwin

Just as a point of curiosity... WHY????

The 8 of 9 on a 7 was Sheldon's solution for a bike where cold setting was not an option (for example, carbon fiber or aluminum).

You are using an old steel bike... Why not just use a 9 speed hub and either spread the rear triangle or cold set the frame and run as a 9 speed?

Steev

If you have a 52t chainring then you probably have 130mm BCD crank. I believe the smallest ring that goes on 130mm BCD cranks is 38t.

HillRider

Correct and the other point for the OP is the Suguino crank has it's chainrings spaced for 7-speed chains. A 9-speed chain is significantly narrower and may want to fall between the chainrings and "skate" on the inner ring instead of shifting cleanly.

A 9-speed chain can be used on an older crank but you will have to pay attention to your front shifting and avoid shifting under load. Also, the old Suguino chainrings lack the ramps, pins, etc. enhansements that make new cranks shift so well. Using the Ultegra crank can pay more dividends than you may think.

Flash

good question. I really like the rx100 hub -- strange as that may seem -- and even though I know 4mm spread is no problem for a steel frame, part of me still wants to keep it at the "proper" 126mm.

the more I think about it, however, the more it seems to make sense to spread the frame 4mm and get a 9spd hub.

decisions, decisions

Flash

so looks like 9spd Ultegra 6500 across the board may be the best decision in terms of minimizing headaches.

HillRider

If you really want to keep the RX100 hub (basically a 105 with a little less finish) You could replace the 7-speed freehub body with an 8/9/10-speed body and respace the hub and redish the wheel.

You could even keep your current 137 mm axle as the resulting 3.5 mm of axle extension beyond each locknut (5.5 mm is standard) is adequate.

Little Darwin

After I posted my question I realized that using the existing hub is a reasonable objective as well.

The thing about upgrading the vintage bikes is that we can each do it in different ways and have our one of a kind bikes, and enjoy them a lot...

It isn't as if the extra gear, going from 8 speed to 9 speed is really all that important to an enjoyable ride... I just had this compulsive need to make sure you knew there were other options for your bike.

dabac

I've been running 9-spd on an LX crank that came from a 7-spd bike for years with a total sum of zero problem like that. Of course it's possible that Sugino 7-spd would have other tolerances than Shimano 7-spd, but I wouldn't worry about that.

Flash

Yes. It's just a feeling I have that I should try 8-of-9-on-7. Going 9spd across the board seems like the easy solution and I'm not sure that's what I'm after.

So, thanks to everyone for the great comments and advice. I'll keep you posted as the project gets underway.

cheers

ericm979

It works on my Vitus, which has the same components you'll be using.

Flash

ok so you put 8 of 9 on a 7spd hub, keeping it spaced at 126mm in the rear?

Can I ask you to list the specs on your Vitus? Curious about the RD, FD and crankset. thanks