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Shimano 105 derailer fit new 7 speed cassette?
#1
I have a 1988 Miyata 712 (12 speed). I recently got hit by a car and had to replace the original Mavic front wheel (with a Mavic Aksium). Surprisingly, it was stiff enough and aerodynamic enough compared to the original wheel, that it has me wanting to replace the rear wheel. too. Not wanting to spend too much on an older (though still nice) bike, I want to do this without spending much beyond the wheel itself. Of course, all of the new factory wheels are equipped with cassettes rather than freewheels.

I was wondering whether if I swap out my current (13-24T) 6-speed freewheel for a 7-speed cassette, if I can get away with my current 1988 Shimano 105 rear derailer and just swap out the current indexed (downtube) shifter for one that fits the new 7 speed cassette. That would limit me to about $50 on top of the wheel.
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#2
how about a pic of the rear D and the Model number on it
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
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#3
1988 6 spd Miyata!? Wow. We need the 'Way Back Machine'! Smile

Your first concern seems to be the shifter. What is it? Can it change modes between Index and Friction?
If it can do Friction mode, it will pull enough cable to travel 7 cogs. In Index mode, nothing will match up.
Whether or not the 105 RD will work - it will, provided that the cage length allows capacity of largest cog and chainring without binding. As you have described the situation, it should.
Funny thing is - 1988 seems so recent.
Wheelies don't pop themselves. (from a QBP fortune cookie)
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#4
(08-14-2012, 09:35 AM)RobAR Wrote:  Funny thing is - 1988 seems so recent.
Yep.
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#5
Tonight we're gonna party like it's 1999. Prince.
Wheelies don't pop themselves. (from a QBP fortune cookie)
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#6
You have to consider the width of the frame / hub. Older road hubs are 124mm wide, newer are 130mm. So keep that in mind. If you have a steel frame you can try cold setting it to the new width. But be careful. I have done that to three of my frames and do not have any problems, but still: be careful!
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#7
My shifters are also Shimano 105s. The front is a non-indexed (I assume friction) shifter. The rear shifter is indexed for 6 speeds, but I don't know whether it can convert to an un-indexed friction shofter.

(08-14-2012, 09:35 AM)RobAR Wrote:  1988 6 spd Miyata!? Wow. We need the 'Way Back Machine'! Smile

Your first concern seems to be the shifter. What is it? Can it change modes between Index and Friction?
If it can do Friction mode, it will pull enough cable to travel 7 cogs. In Index mode, nothing will match up.
Whether or not the 105 RD will work - it will, provided that the cage length allows capacity of largest cog and chainring without binding. As you have described the situation, it should.
Funny thing is - 1988 seems so recent.

I measured the inside width of my frame (at the rear hub) with a calibrated scale and got 5 inches exactly, which works out to 127mm. My first thought would be that the frame was bent, but it fits the hub perfectly. The hub is also a Shimano 105, so I think that it is the factory original wheel/hub.

(08-15-2012, 02:44 AM)Joe_W Wrote:  You have to consider the width of the frame / hub. Older road hubs are 124mm wide, newer are 130mm. So keep that in mind. If you have a steel frame you can try cold setting it to the new width. But be careful. I have done that to three of my frames and do not have any problems, but still: be careful!

(08-14-2012, 09:28 AM)painkiller Wrote:  how about a pic of the rear D and the Model number on it

I took some photos, but they ended up being out-of-focus slightly. I will take more tonight. Besides, I cannot find any part number (other than the 10 label) to distinguish short frame, long frame, etc or other features.
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#8
Ooops, my mistake. So it's just 2.5mm more per side. That usually works out well without respacing the frame, though you might want to realign the dérailleur hanger.

http://sheldonbrown.com/frame-spacing.html
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