Bicycle Mechanics - 7 speed wheels for a 15 year old MTB

I have a 1993 Diamondback Ascent with the original 7 speed drive train (Shimano Atlus A10) and the original Araya CV-7 wheelset. I'd like to swap out the wheels for something a bit lighter, but I've had an impossible time finding 7 speed wheels online. 8 speed seems to be as low as I can find for MTB wheels. I'm pretty sure it's not possible for me to put the original 7 speed cassette on a wheel made for 8 speed (please tell me if I'm wrong about this!), and I really do NOT want to go through the expense of changing the whole drive train to 8 speed on this old bike esp since it works perfectly fine still after all this time. I really don't want to spend an absurd amount of money on new wheels for this bike, so does anyone know what my options are here? I was expecting to be able to find 7 speed wheels for next to nothing online, however that does not seem to be the case.

Hell jstraw,

The only problem is that current cassette wheels are made for "modern" cassettes (8 speed or more). 7-speed cassettes will fit but not stay put.

Well, there are several solutions:

1. Quick, dirty and cheap(ish):
Use the original cassette or buy a new 7-speed one if you want (easily found online: http://www.performancebike.com/shop/profile.cfm?SKU=11469&subcategory_ID=5130) and put them on the new wheel using a 4.5mm spacer. The spacer goes on the freehub body between the hub and the cassette (close to the center of the wheel). You can find the spacer online or retrieve some sprocket separators from the LBS or an old cassette (or your old cassette if you buy another one)

2. Somewhat more complex and unnecessary: (in my humble opinion):
Buy the new wheels and change the freehub body (look in the forums on how to do that) to 7-speed body (if possible).

3. Slightly more expensive but nicer:
Buy a new wheel, a new 8-speed cassette and a new 8-speed shifter. I just did that to my old MTB. I changed the original 7-speed SRAM Grip Shift to a new, similar 8-speed one (very easy to do, not expensive at all and it almost looks the same esthetically speaking). I also changed the rear derailleur since my old one was crap, but you don't have to do that. You will need to adjust it to match the new cassette (especially to change the limit for the largest sprocket).
I hadn't needed to change the chain as most(all?) 7-speed chains works also for 8 speeds.
This way you have some a new and nicer 8-speed wheel on your old MTB.

BTW, are you sure about your rear wheel: cassette or freewheel? In any case, if you originally had a freewheel you can change it to a cassette without worries.

Cheers,
Dan

Thanks for the reply. As for my "cassette", no I'm not sure and it probably is a freewheel in all actuallity. I have a much newer road bike that I work on too so I always end up calling them cassettes by default. I think your first option is the most attractive one to me. So you're saying a new 7 speed cassette will be compatible with a new 8 speed wheel as long as I use a 4.5 mm spacer? Are the sprocket separators different on my old 7 speed freewheel compared to a new one? I have no problem buying a new 7 speed cassette if this is the case. Thanks again!

There are still 7 speed freehubs available as parts through the local shops or at some parts specialty places online. So either shim as suggested or buy a wheelset and new freehub and swap out the freehub before you remount your 7 speed cassette.

I'd also check your dropout spacing as per Sheldon Brown's site. If your bike uses a freewheel setup it may well be a smaller spacing than the cassette/freehub size of 135mm's that all the online wheelsets will have.

Also if you're using a freewheel setup it'll explain the weight you're feeling. Those freewheel and cog cluster assemblies are VERY heavy..

ID your present setup first......

http://sheldonbrown.com/k7.html

and....

http://sheldonbrown.com/k7.html#up7

And this to measure your spacing to see what wheelset will fit....

http://sheldonbrown.com/gloss_sp-ss.html#spacing

According to bikepedia.com, your bike has a 12-28 cog set. I'm quite sure that's a cassette, instead of FW, with that combo.
You could swap the current 7 speed body to the new wheel as an option.

What I would do, is get the new 8/9 speed body and use the 4.5MM ($2) spacer. That way, if you later decide to upgrade to more gears, it'll just be a matter of shifters & cassette. (& chain if 9 speed)

By 1993, freehubs and cassettes had pretty much completely replaced freewheels on all but the cheapest bikes. I expect your bike already has a cassette. I further expect is is spaced the still current 135 mm.

As noted, an 8-speed freehub with a 4.5 mm spacer will let you use a 7-speed cassette. That's the least expensive way to adapt newer wheels.

As noted, an 8-speed freehub with a 4.5 mm spacer will let you use a 7-speed cassette. That's the least expensive way to adapt newer wheels.


Thats the way I went with my 96 Jamis Durango. Replaced the original wheelset in 2003, all I needed was the spacer.

Choice (1) is what I did as well. A nice new 7-speed cassette will only cost $20-25.

Anyone know where I can get the 4.5mm spacer everyone has been talking about?

You get an old worn out cassette from an LBS and rip it apart. I believe that it's a spacer plus the thinner washer that often fits under the last small cog. The spacers used between each cog will add up in some combo to make a spacer you can use. The actual size isn't really critical other than you want to be able to tighten the cassette while not having it stick out so far that it rubs on your stays or dropout.

Standards seldom seem to apply when you think they should. I'd still measure the dropout spacing as shown in that link to Sheldon's site I posted above just so you know what you're dealing with and go in prepared. If you do have a 135mm spacing then you're golden to go ahead. If not then you need to stop and consider the alternatives. After all, it's not like it's a lot of work to check it. Also I've found from working on a few older and less expensive bikes that the freewheel equipped bikes most often had the narrow spacing. If so then you need to stop and consider if you want to go ahead and cold set the frame or just stick with freewheel setups.

Anyone know where I can get the 4.5mm spacer everyone has been talking about?

Right here: http://www.thethirdhand.com/index.cgi?d=single&c=Cassette&sc=Spacers&tc=&item_id=WB-NCS4.5&id=948974518928

Any LBS should have the spacer.

If you choose to go the 8 speed route, you may need to change the derailleur as I found out that a 7 speed derailleur (like my Shimano STX) does not have enough range to reach the inner cog (the biggest one).

If you choose to go the 8 speed route, you may need to change the derailleur as I found out that a 7 speed derailleur (like my Shimano STX) does not have enough range to reach the inner cog (the biggest one).
I have an STX "7-speed" rear derailleur on an older road bike running an 8-speed cassette and it has no problem whatsoever shifting to the largest cog.

If you are having that problem, it's likely your inner limit screw needs to be adjusted.

Ah, it might not be the number of cog on the cassette that messes with a older rear derailer (like the older STX unit), but rather the number teeth on the biggest and smallest cogs.

An older MTB bike has a 12-28 tooth range on the cassette. If you replace it with a more modern one, say a 11-34, it's possible it won't work. The old STX rear derailer may not handle 34 tooth granny gear. It's also possible that the chain will crunch into the frame using the smaller 11th tooth cog. Neither of these problems have anything to do with the number of cogs, BTW.

If you'd like to keep things simple, stick with the same specs the bike came out of the factory with.

I have an STX "7-speed" rear derailleur on an older road bike running an 8-speed cassette and it has no problem whatsoever shifting to the largest cog.

If you are having that problem, it's likely your inner limit screw needs to be adjusted.
The limit screw was all the way out and it would not work. I tried a 12-28 8 speed cassette (the original is a 13-30 7 speed cassette). Anyway, my bike has been happy since with 7 gears (it's now my winter bike).

The limit screw was all the way out and it would not work. I tried a 12-28 8 speed cassette (the original is a 13-30 7 speed cassette). Anyway, my bike has been happy since with 7 gears (it's now my winter bike).

Did you think to try 8 speed shifters?
Did you start the RDER adjustment from scratch? No cable tension when in the smallest cog?
Which limit screw?

I assume the dropout spacing is 130mm for 7 speed. Modern mountain bikes are 135mm. A decent bike shop can cold set a steel frame to that for ~$15. Or you can build a wheel using a modern 130mm road hub and a 26" rim.

You know, Shimano 8-speed cassetes and 7-speed cassettes have nearly the same tooth spacing, and IIRC, Altus 7-speed hubs are 135 mm OLD. So, you can just get a new modern wheel and put on an 8-speed cassette, and adjust your RDER so it uses 7 out of the 8 speeds.

You know, Shimano 8-speed cassetes and 7-speed cassettes have nearly the same tooth spacing, and IIRC, Altus 7-speed hubs are 135 mm OLD. So, you can just get a new modern wheel and put on an 8-speed cassette, and adjust your RDER so it uses 7 out of the 8 speeds.

Well, if you want to almost change the speed, go ahead. I've tried, didn't liked. You still need to use a new 8-speed shifter with the new 8-speed cassette