Bottom Bracket Spacers not working per Shimano instruction sheet. Curious.
#1
Si Senior
Thread Starter
Join Date: Nov 2004
Location: Naperville, Illinois
Posts: 2,669
Bikes: Too Numerous (not)
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 23 Post(s)
Likes: 0
Liked 10 Times
in
8 Posts
Bottom Bracket Spacers not working per Shimano instruction sheet. Curious.
Finally getting around to building up the 88 trek 850 into a touring setup. Installing a new Shimano FC-M591 Deore Crank+BB and the spacer instructions don't work. Shimano instructions show (for 68mm shell) three spacers on right (2.5 + 0.7 + 1.8) and one on the left (2.5). All are required to fit the crank to the BB shell, but Shimano's recommendations throw my chainrings way outside where it should be. Even the arm distances from the chainstays are off (much closer on non-DS than DS). I'll rearrange the spacers until it works right, but I'm curious if others have seen this. Or maybe I shouldn't have read the directions at all.
#2
Si Senior
Thread Starter
Join Date: Nov 2004
Location: Naperville, Illinois
Posts: 2,669
Bikes: Too Numerous (not)
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 23 Post(s)
Likes: 0
Liked 10 Times
in
8 Posts
It appears that "no spacers" on the DS and "all spacers" on the non-DS is the only thing that gets them close to equal in the BB shell, and the chainrings still seem too far outside. The protective plastic cylinder gets torqued and starts to warp if I eliminate any spacers. And "all spacers" on the left leaves it with not much bite on the threads. Looks like I may go freestyle on this and shorten the plastic cylinder, eliminate several spacers, and possibly abandon that tiny latch pin (if the non-DS arm pushes in too far). Anybody know something I'm completely missing here? Maybe weird leeway using (68/73) MTB crank on road frame (88 850 is 26" wheel mtb frame supposedly, but the 68mm bb shell and 130 rear drops makes it more like a road frame)
#3
Senior Member
Join Date: Dec 2007
Location: San Jose, California
Posts: 3,504
Bikes: 2001 Tommasini Sintesi w/ Campagnolo Daytona 10 Speed
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 145 Post(s)
Likes: 0
Liked 35 Times
in
30 Posts
Well...I did want to ask, "Why did you decide to go with this type of crank and bottom bracket?" It would seem to me to be easiest to go with a square taper crankset and bottom bracket as you would have close to a dozen symmetrical spindle sizes to choose from, and for asymmetrical spindles, half a dozen sizes to choose from each with several degrees of variation in the asymmetry.
And then there's Phi Wood's bottom bracket....
Just asking, that's all.
=8-)
And then there's Phi Wood's bottom bracket....
Just asking, that's all.
=8-)
__________________
5000+ wheels built since 1984...
Disclaimer:
1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:
Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life
5000+ wheels built since 1984...
Disclaimer:
1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:
Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life
#4
Senior Member
Join Date: Jul 2002
Posts: 6,956
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 6 Times
in
5 Posts
but Shimano's recommendations throw my chainrings way outside where it should be.
For example, in the early '90s, I was accustomed to having the inner face of the granny ring somewhere near the plane of the BB shell's driveside face. Nowdays that's not the norm, not for Shimano's stuff anyway. If they did that, the tail of the FD would be hitting the tread on the rear tire on many bikes, especially in this era of 29er popularity. Hence the 50mm chainline.
If you want to fudge the positioning by one spacer, you should still have enough bite on the non-driveside. Myself, I'd use metal spacers that won't split if they're under a lot of torque, and install the cups quite tightly... you don't want issues when you're on tour.
#5
Si Senior
Thread Starter
Join Date: Nov 2004
Location: Naperville, Illinois
Posts: 2,669
Bikes: Too Numerous (not)
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 23 Post(s)
Likes: 0
Liked 10 Times
in
8 Posts
I kinda like these newer external bearing setups --and I was assuming there was a element of universal fit. (and the 48-36-26 was the chainring set I was looking for). It looks like it won't fit even if I freestyle the fit. The spindle is a full 10mm longer than a road crank spindle. Non DS crank arm pushed to its limit bottoms out before I can fully take up the needed slack.
Back to the drawing board on cranks. I might use the tiagra road crank from the bike that will be donating its shifters (it's 50-39-26). Or I start from scratch.
Back to the drawing board on cranks. I might use the tiagra road crank from the bike that will be donating its shifters (it's 50-39-26). Or I start from scratch.