RoadBikeReview.com's Forum Archives - Components


Archive Home >> Components(1 2 3 4 5 6 7 8 9 10 )


8 spd sti levers on 7 spd bike(7 posts)

8 spd sti levers on 7 spd bikedan ida
Jul 11, 2001 6:43 PM
I am installing the above 8 spd levers on a 7 speed bike. They work perfectly but there are two options for the extra shift position. I could use the low limit screw to lock out the last shift toward the spokes or I could have one extra shift click at the high gear end on the sti lever. Right now that is how I have it adjusted (one extra click at the high gear end that does nothing) because it seems safer from the possibility of putting the chain into the spokes. It also seems less stressful on the sti lever than having a shift being cancelled by the limit screw- stretch on the cable too. Any thoughts on which is better for other reasons. THANKS. This is my first frame build up and it works well. (Specialized Allez / shim 105 / rear wheel axle changed to 130 width)

DAN
Makes Sense to Me1 grzy mnky
Jul 11, 2001 7:03 PM
I'd concur on your setup. What did you do about the rear wheel dish if you went with the longer axle/spacer combo? The bike tends to ride a little funny and in a "crab" otherwise, you may not even notice it. Of course "correcting" the dish just makes the difference between the two sides greater......
wheel dish ideasdan ida
Jul 11, 2001 10:33 PM
The rear hub was changed to 130 before the wheel was built. When comparing it to my other seven speed rear wheels, which are still 126, the rim is more centered on the hub than the rest. It seems the spoke length must be more equal on this one wheel I have. Interesting you brought it up, since I have an Ultegra 7speed hub that I am planning to lace up for the smae bike and am wondering what will be the best way. I WAS planning on 2 mm spacers on each side and normal length spokes. But now I wonder if putting 4mm on the non drive side and using nearly equal length spokes is a better idea.

DAN (and thanks a lot)
Couple of ideas:Spoke Wrench
Jul 12, 2001 7:30 AM
I'd vote for the 4mm spacer on the non-drive side and more nearly equal spoke lengths. That will allow you to use more nearly equal spoke tension on the left and right sides. The more equal you can get the spoke tension, the more reliable the wheel will be.

I'm surprised that you say the shifting is perfect because the spacing of 7 and 8 speed drive trains is a little different. I've tried that a couple of times and could get to kind'a work, but it shifted a little funny. Basically, it took two shifts to get the derailleur to change directions and worked OK after that.
7 vs 8 cogsdan ida
Jul 12, 2001 12:05 PM
I took a seven cog and an eight cog and set them next to each other on a straight flat table (one set upside down) to see if the spacing was the same. they matched up exactly - at least by eye. Except of course that the eight had one more gear on top. Then I measured a stack of six eight speed cogs and it was 1.025 versus six seven speed cogs which were 1.052. A different seven speed group of six measured 1.045 - even closer. That's a difference of .020 - .027 over 6 gears and five spacers. Is that the slight difference you are mentioning or ???? If this twenty thousandths critical? Is the difference in the gears or the spacers???

DAN
Now you've made me look some stuff up.Spoke Wrench
Jul 12, 2001 4:27 PM
Shimano 7 speed cassette cogs are 5.0mm on center.
Shimano 8 speed cassette cogs are 4.8mm on center.

Over 7 cogs the difference is about 1.2mm 25%. I think that is close enough that it works, but not perfectly. Which is exactly the experience that I've had.
dan ida
Jul 12, 2001 5:26 PM
Great discussion- and THANKS AGAIN

DAN