Why won't a 8/9 speed hub/wheelset fit on an older bicycle with a factory 6/7 hub?

Question

I've got an old Norco Kokanee that needs a rebuilt hub, so I figured, why not upgrade to an 8-speed, but I noticed that the sealed 8-speed hub/wheelset from my newer Marin won't fit the old Norco frame (i.e., the hub is too wide for the area allocated). Why is this? Why aren't all frames/hubs a standard width? Mostly, is there any way to get a 8-speed hub onto this bike, or am I stuck with a 6/7? Thanks.

Answer 1

I did it last week.

The process is very long, very stressful because of the risk, and overly frustrating.

First, one spreads the frame to 130mm between the dropouts. Only steel frames can be spread.

Next one runs a string through the dropouts and around the head tube.

One continues to struggle with the frame until there is exactly an even measure between seatpost and string on both sides.

Next, one takes the new wheel and attempts to center it in the frame. This won't work. It will be tilted to one side or the other.

Measuring from a tape mark or pen mark put onto the centerpoint of the new rim, and with the tail of the ruler against the seat stay, one finds the narrowest side. Now one removes 1mm of material from the dropout on that same side.

After that, the new wheel will be straight.

See Sheldon Brown's articles at harriscyclery.com

You can also take the bike to a long-established bike shop that happens to own a "frame table" to get more precise results or you can take/mail the bike to a builder to have it re-sized.

Also possible is the selection of a modern hub of the cup-n-cones (adjustable re-buildable) design.

Now, THAT is the easy way. Simply remove the spacer from the non-drive side. Stack axle spacer washers instead. When those, plus the bolt fits your 126 overlocknut dimension size, have the hub adjusted correctly (easily done) and then have a rim installed.

Whoops! If your rear derailler mounts with a bolt that goes through the rear dropout, then you will also need to add a 1.5mm spacer underneath the bolt to the drive side or else a 12t gear (modern) will push the chain into the derailleur mounting screw. I also did that last week, so it would have been far easier just to re-space the hub and leave the frame alone. ;)

If you do this to an existing wheel, you will need to tighten the spokes on the drive side to re-dish the wheel so that it runs centered through your brakes. Temporarily set your brakes close and as evenly spaced as possible. Use the brakes as you would a truing stand. Do lots of squeezing on the spokes to guess the tensions approximately even. As a last step, true the wheel for roundness without changing the dish.

The chain that works from an 8 speed rear hub to a front crankset made for 6/7 is HG70 for Shimano 8 speed cassettes or SRAM PC58 if you use the featherweight, high performance PG850 cassette. Chain must match cassette.

For a 9 speed rear drive or a 10 speed rear drive, there is no full compatibility to a crankset made for 6/7 speeds and you would need a replacement crankset.

At this time, you might measure your old chain to see if 24 links (a foot of chain) is more than 1/8" past the 1 foot mark. If so, you'd need a new crankset anyway, so might as well go 9 speed. The new Tiagra 9 is quite a good value.

Whether 8 or 9, you can "hide" a Alivio 8, Deore 9 or Sram 9 (non-numbered Shimano-ready series) mountain "trigger" shifter at the top grip, cyclocross style, near the stem. This is from $24 to $55. Yes, it is a tight fit on road handlebars, but it works fantastic--no long reach over the front. ;) A plain lever can shift the front derailleur with high-quality results. Nice ratcheting alloy models are to be found, and with those, there's no front indexing which can (and usually does) go wrong.
A very high quality shifting option is an economy Campy (doesn't index the front) set matched to a Shimano drivetrain with the $25 Jtek Engineering roller that plugs into a Shimano rear derailleur. These are more reliable than Shimano STI, and can be found for low prices. See the Jtek Engineering website for compatibility/selection.
I'd check aebike.com for shifter options at lower prices.
Also, Ultegra, Dura Ace, and non-series bar end shifters are available. These can be mounted on Paul Components Thumbies adapters so that you can locate shifting (time trial style) wherever you usually put your hands. Now, doesn't that make sense? Personally, I never, and oh, I mean never, hold the bike completely over the front while riding. ;)

A Weinmann or low-priced Shimano hub will usually be of the cup-n-cones design. You can re-space those.

You'll need axle spacer washers (thin 1mm and 1.5mm washers), a spoke wrench (probably green Pedros), a cone wrench (probably 13/15mm Park), and the little cassette remover (installer) tool (Park FR-5) so you can put the cassette on.

The articles on harriscyclery.com will help you to adjust the hub after you have re-spaced it. Hint: It should neither growl/grind or have any slack. This adjustment is exactly like all other cup-n-cones parts like older bottom brackets and all headsets.


Why is the 8/9/10 wider than the 5/6/7?

A severely dished wheel is weaker, so to make room for the extra gears, the bike was widened. Today's mountain bike is 135mm but today's road bike is 130mm.

However, in order to prevent the rear wheel from being weaker, you can just tighten the drive side spokes to a nice firmness. This results in a slightly firmer, but not weaker wheel.

See you down the road!

Answer 2

The rear spacing on a mountain bike with 8/9 speeds is 135 mm from the inside edge of the rear dropout to the inside edge of the other dropout. The 6/7 speed hubs for mountain bikes used a narrower spacing, somerimes it wa 126, sometimes 128, and sometimes 130mm, so the 135 8/9 won't fit!

However, there's always a however - if you have a steel frame it is easy to spread the rear triangle and realign the dropouts and the rear derailure hanger when you are done so that the 8/9 hub can fit and the derailure is in correct alignment.

You can put a 7 speed cassette on the 8/9 hub so you won't have to replace the shifters to 8 or 9.
A full 7 speed to 8/9 speed conversion ca turn into a big job.
If the chain is stretched - and it probably is - it will have to be replaced to mesh correctly with the new gears - and the 9 speed definetly uses a narrower chain and the 8 speed should. This would the necessitate the replacement of the front chainrings because they are narrower as well to go with the narrower chain. If you have rivited on chainrings you will have to replace the entire crank-set and the bottom bracket and this could cause you to have to replace the front derailure.

It can be a can of worms to change one component on a drivetrain! You can try it one piece at a time but it can be maddening.

Answer 3

What Daniel said. Mostly because older frames were made of steel which has some spring to it and can be bent to some extent and accomodate the 130mm 8-9spd hub. You can't do that with more current aluminum frames because they will crack if bent similarly.

I say instead of messing around trying to upgrade an old Norco, buy a comparable new bike. It would be less hassle and more than likely better than the Norco.