Bicycle Mechanics - 7 speed - 9 speed conversion

I just picked up an older hardtail Specialized Rockhopper. (Couldn't pass it up. Perfect condition and in a large frame that actually fits my 6'2" frame - $100) I would like to, eventually, put better rims on the bike. It makes no sense to rebuild on my existing hubs as they are not the best quality. Good wheels with compatable hubs are not readily available. The most cost effective solution seems to be to purchase some 9 speed cassette wheels on sale. I assume that means that I would also have to replace the deraillers and the shifters/brake levers. I am willing to do that, but would prefer to not to spend the money all in one shot. Is there any way that I can phase in the conversion? For example, can I configure a 9 speed cassette so that it will work with the current 7 speed indexed shifters and derailleurs? Thanks for your feed back.

No es necesario. Just throw a 7s cassette on that 8/9s hub with spacers to take up the difference.

Where do the spacers go? On the inside of the cassette?

Where do the spacers go? On the inside of the cassette?

Yeah, on the hub-side, not the lockring-side.

Two things to consider :

- Check the dropout width. With 7-speed bikes, it used to be 126 mm, then it increased to 130 mm (for MTBs and hybrids only, I think). Then, from the measurement you get and from the material of the frame, you can decide what to do.
1. If it is a steel frame, then it's easy to spread the frame to 135-mm and get a new wheel with a 9-speed MTB-type hub such as LX or XT.
2. If it is an aluminium frame, don't spread it! Then get a new wheel of the proper width. Two years ago, I had no problems finding locally a 126-mm wheel with a 7-speed freehub, so it still can be done. If you have 130-mm spacing, then you can go with a "road" hub with a 9-speed freehub.

- Number of speeds and drivetrain. A lot depends on the age of the bike and components.
1. If your system isn't indexed (i.e. no clicks between gears), then don't worry, be happy. Your derailleur and shifters will work irrespective of the number of speeds.
2. If your rear derailleur is a Shimano indexed derailleur, then as far as I know, it will be compatible with any new shifting requirement, whether you go to 7, 8, 9 or 10 speeds. If it's a pre-1985 derailleur, then it might work in indexed mode. Basically, it's the shifters, not the derailleurs that decide how many gears you shift.
3. As said above, you can install a 7-speed cassette on a new 8/9 speed hub. Just add 1-2 spacers. If you cannot find them locally (I can't, except in my own spare-parts box), you could also install an 8-speed cassette on an 8/9 speed freehub.Decide which gear (lower or upper) you don't want to use, set the limit screws and adjust the shifters accordingly. Then your existing 7-speed shifters will shift – indexed – through the 7 gears you have selected.

A lot of explanations may be found at http://sheldonbrown.com/k7.html

Two things to consider :

- Check the dropout width. With 7-speed bikes, it used to be 126 mm, then it increased to 130 mm (for MTBs and hybrids only, I think). Then, from the measurement you get and from the material of the frame, you can decide what to do.
1. If it is a steel frame, then it's easy to spread the frame to 135-mm and get a new wheel with a 9-speed MTB-type hub such as LX or XT.
2. If it is an aluminium frame, don't spread it! Then get a new wheel of the proper width. Two years ago, I had no problems finding locally a 126-mm wheel with a 7-speed freehub, so it still can be done. If you have 130-mm spacing, then you can go with a "road" hub with a 9-speed freehub.

The current hub spacing is very likely either 135mm or 130mm. Never heard of a 126mm spaced 7s mountain bike, but have seen plenty of 135mm spaced ones. This page has lots of relevant info on this topic: http://sheldonbrown.com/frame-spacing.html




- Number of speeds and drivetrain. A lot depends on the age of the bike and components.
1. If your system isn't indexed (i.e. no clicks between gears), then don't worry, be happy. Your derailleur and shifters will work irrespective of the number of speeds.
2. If your rear derailleur is a Shimano indexed derailleur, then as far as I know, it will be compatible with any new shifting requirement, whether you go to 7, 8, 9 or 10 speeds. If it's a pre-1985 derailleur, then it might work in indexed mode. Basically, it's the shifters, not the derailleurs that decide how many gears you shift.
3. As said above, you can install a 7-speed cassette on a new 8/9 speed hub. Just add 1-2 spacers. If you cannot find them locally (I can't, except in my own spare-parts box), you could also install an 8-speed cassette on an 8/9 speed freehub.Decide which gear (lower or upper) you don't want to use, set the limit screws and adjust the shifters accordingly. Then your existing 7-speed shifters will shift – indexed – through the 7 gears you have selected.

On point #1, the OP mentioned the index derailleur and shifters on his bike. I agree with point #2, but only if one sticks to Shimano-compatible index (also known as SIS) components (Sram, Suntour, and Campagnolo all had/have different systems). On point #3, the cog spacing of Shimano-compatible 7s cassettes is different from that of Shimano-compatible 8s cassettes.

7 speed casettes are 5 bucks new on ebay. Forget nine speed. It just wears out faster.

Forget nine speed. It just wears out faster.
That certainly hasn't been my personal experience