Bicycle Mechanics - Shimano Deore XT Crank Installation
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05-20-09, 12:49 AM
I have a 68mm Bottom Bracket shell and am installing a set of Shimano Deore XT Cranks with the included Bottom Bracket.
I installed the bottom bracket per the instructions using the specified spacers on the correct sides and my chain line was no good; the chainrings were way too far out (away from the frame). I reinstalled the bottom-bracket using a single 2.5mm spacer on the drive side and the rest on the non-drive-side.
The ideal chain-line for this setup is achieved by using no spacers on the drive side and putting them all on the non-drive side. By doing that and loading them all on the non-drive side it leaves what i think is an insufficient amount of thread for the non-drive side of the bottom bracket. Using a single 2.5mm spacer on the drive side appears to be a good compromise. The chain line is good (enough) and there's a good amount of thread on the non-drive side for the bottom bracket to be securing installed.
I took it on a short test ride and it shifts well; it's quiet, feels good etc
Is there any other way to go about this? Have I a made a mistake doing what i've done or this is pretty much par for the course with these cranks and the bottom bracket i have?
Also, am i to remove the small plastic loading screw on the non-drive side crank arm after setting it properly or does it stay in there all the time? I have an ultegra crank and that screw stays in: it's aluminum and appears to be designed to stay, the black plastic one on the deore set doesn't look like it belongs (doesn't match etc) although the instructions say nothing about removing it. I've left it in but can easily remove it.
thanks in advance for any answers or advice!
Is this a road bike? You mention Ultegra cranks, so I assume so.
XT cranks are made for a 50mm chainline. Ultegra double 43.5, triple 45mm. There's the 5mm. Mtb cranks like that are meant to stick out.
Did you read the manual for XT cranks... check it out. http://bike.shimano.com/media/techdocs/content/cycle/SI/Deore-XT/FrontDriveSystem/SI_6MPFA_002/SI-6MPFA-003-ENG_v1_m56577569830671849.pdf
If that's not your exact model, find the right one.
05-20-09, 06:58 AM
it is a road bike, i was looking at those instructions exactly and those chainline numbers you mention match up with what i've been working under. Do you mean i should install it exactly as specified in the manual?
it'll definitely throw the chainline back off those 5mm which upon visual examination looks like it'll be a mess but maybe it won't make any functional difference? It'll cross-chain now - it rattles around a touch but works fine, i doubt it'd be an option with the chainring kicked out 5mm more.
I assume there's some reason for it to be a farther out chainline, maybe the mountain bike chainstays are bigger or at more of an angle? This bike's a road/touring frame with 700c (x28) wheels/tires. Also - if it could possible makes any difference the rear-dropouts are 135mm and i'm running a mountain bike hub/cassette/RD. Tiagra FD to run a bottom-pull cable from friction shifters.
Hmm..... while I have zero hands-on experience with the integrated cranks and BB's, I do know chainlines. It does sound like it's a mess, but there's always a solution. Mtb cranks these days are made for larger tubes, larger tires, wider stays etc. ..... but it's not really an excuse for them to make these cranks with such large chainlines or Q factors. They make them for one size fits all. As you found out, it doesn't work so good on a road bike!.... at least not the outboard bearing type as it does not allow much adjustment or choice in axles like a tapered one would.
What's your FD, a clamp on?
What is your set up? Is it 126 or 130mm rear? Going to 135mm would certainly help, but not solve the problem. Is this a brand new crank? Are you really set on using this crank? My first thought is to use a different crank, because for a triple on a road bike with a 45mm chainline is exactly what you need. I know with a Surly Mr. Whirly you can get a 45mm chainline for a road bike by moving one spacer, but since the XT is set for 50, and the tech document states that one 2.5mm spacer can be moved to the non DS, it may not have enough threads for the cups, as you noted.
If you use a spacer on each side for a 47.5mm chainline, it would work, but not well.
You may have to get some further advice here, as I don't see any way you can get to a 45mm chainline and have proper # of threads in the bearing cups. My gut says.... wrong crank for the job. I could be mistaken though. Don't feel bad... your just another "victim" of the modernization of bike parts. It's not like the days when road and Mtb cranks could be used interchangeably.
Second thought.....For a road bike, do you really need that low of rings? There's a Sugino triple that you can get a hundred bucks that uses a tapered BB that you can get the right chainline(highly adjustable). Comes with 24 or 26/36/46 or 48.
that's all I know for the moment :)
05-20-09, 08:24 AM
The chainline specified for MTB cranks assumes a 135 mm rear dropout spacing.
05-20-09, 06:17 PM
hey there - thanks guys. it is a 135mm dropout in the rear, garthr, i think i'm in the situation you mentioned... i'll look into it some more, might not be the right crank for the job. more to come, i'll let you know what comes of it..
back to the drawing boards. i am looking for a 48-36-26 (or something real close to that anyway).
oh, and it is a clamp on FD
05-20-09, 07:25 PM
FWIW, I'm running deore triple cranks (48-36-26) on my bianchi axis (tiagra FD and shifters) with no problems I notice. If there is something I can measure to help you out, let me know.
05-20-09, 07:41 PM
pacificaslim - i'm assuming you're using the Deore Bottom Bracket. Do you have the spacers setup in the stock configuration (per the manual)?
I set mine up that way to begin with and the chainline was off quite a bit. I didn't measure it but it sure looked like more than 5mm, it looks like close to a centimeter.
How does you bike work while cross-chaining, or where does it start to not work well?
I have mine set up at a 47.5 chainline (removed a single 2.5mm spacer from the drive side and put it on the non-drive side) and it's workable going from big in front to big in back but it's not pretty. In general Running from Big in front to small in back makes some noise and it should be silky smooth.
I'm considering swapping out the crank for a Sugino with the same chainrings and 45mm chainline. i can probably get my hands on one to try and make sure it works.
Did you bike come with the deore crankset or did you add it? It looks like the current model of that bike comes with a Sugino.
thanks for the help!
05-20-09, 10:01 PM
Unfortunately for these purposes it was installed on the bike when I bought it. I got it as a left over '07 model from a shop and they had changed it out for some reason. They had changed a few other things too, but nothing of consequence and I only paid $650 out the door instead of the msrp of $1300 or whatever crazy price bianchi set.
Anyhow, I don't notice any rough shifting going up or down, regardless of chainring. It'll even completely cross chain either way (and the shifters allow those half-movements that move the front derailleur just enough to not rub). This is with my mavic wheels with a 11-26 sram 9-speed cassette.
The bottom bracket says "BC1.37". I'll try to figure out what spacers it has where and try to measure the chainline (gotta go to sheldon's site and give myself a refresher on measuring!).
Is it the Octalink or the Hollowtech bottom bracket? You may be able to get a shorter spindle if it is Octalink. I have changed out a Shimano Octalink crank set on my wife's touring bike. You have too be carefull about what Shimano crank you have,e.g., a Deore 443,their "trekking crankset" (48/36/36) has a different chainline than the 442 their "Mtn bike" crankset( 44/34/22). They look exactly the same and the chainwheels are interchangable, but the crak arms are constructed differently. I think Garthr is right about the mountain bike cranks being made to match the 135mm mountain bike drop width, making them too wide for stock road bottom bracket. Bottom line is that I had to use shorter bottom bracket spindles when going from a road or trekking crankset to a mountain bike crank set.
I have three Sugino cranksets that travel between my touring bike and my commuter bike. Two have the same bolt pattern. The trekking crankset takes a 110mm square tapered botom bracket and the mountain bike cranks take a 103mm BB to get approximately the same chian line. Between two sets of cranks I have the choice of 48,46/36,34/28,26,24 chainrings I tend to favor the 46/34/26 on my everyday ride, so they don't get switched around very often. The one I have on my touring bike now is a 44/34/22( took off the 48/36/26). The point of all this BS is that the advantage of the square BB spindle, is flexibility.
Is it the Octalink or the Hollowtech bottom bracket?
The way the OP writes about the spacers leads me to believe this is a Hollowtech integrated spindle type crankset. The mention of the plastic preload "screw" confirms it.
Considering that the OP has a mountain 135mm hub and a mountain crankset, what I don't understand is why the optimal chain line should be closer to the frame. Is it because of the use of a road type FD?
Well, this is interesting isn't it. Now that we know the rear is 135mm, and he has it set it up according to spec, it is "supposed" to work. This is also assuming the frame is properly aligned. It would be a good idea to check it at this point.
Then again ,after reading the OP's first post, the chainline with a spacer on each side was "good enough". I think we need to know what that means! What gears in what rings were usable? It would also be helpful to know frame material and FD clamp size.
We also have to consider what the 50mm chainline is for...... not only larger tubes, it helps rider who will ride more in the two small rings than the two larger rings. You can't have a chain work over the entire spectrum of 3 rings and 7,8,9,10 or 11 speeds, at least not without the high risk of breaking the chain and your face! A 45mmm chainline is good for road bikes, where you're mostly on the two larger rings, and the small is a bail out of 3-5 gears.
For example, on my steel road bike, 135mm rear spacing, I use a TA Zephyr crank, a mtb crank, tapered design, 122mm BB(+1.5mm driveside spacer). Using 26/44/48 rings with a 45mm chainline, I use 4 gears in the 26, 7 in the 44, 6 in the 48. This is a 7 speed setup. If I wanted to use the 2 small rings most of the time, I could use a longer BB, but I would lose 1 or two big ring gears, depending on how far out I extend the chainline.
As noted, this is where a tapered crank and BB really shine. With any given crank, you can set up the chainline any way you want by changing the axle or cartridge BB. Setting up a bike may be science for some, but to me it's really a merger of science and art. No manufacturer can conceive of all the possibilities in installation variables. This is a real drawback to the Integrated design.... no choice in axles.
05-22-09, 04:32 PM
hi guys! just got back home, thanks for all of the useful suggestions so far! to answer/confirm some of the questions, it's a hollowtech ii bb, sorry i forgot to mention that in the beginning.
The frame is steel (28.6mm is the size of the clamp on FD). As far as what gears were sort of the most usable, definitely the inside 2 chainrings worked pretty well, using the largest (48t) there was quite a bit of chatter once i got a couple/few cogs into the cassette. I rode it for a minute or two fully crossed on flat ground and it definitely didn't like it.
It's difficult to qualify what 'good enough' means, well really - what it meant at the time. I've only ridden it about 3 miles on a flat stretch of road near my house to work out kinks after assembly. I then promptly left the coast for a few days and just now returned a little bit ago. i could shift between all gears smoothly but there was lots of noise when i started to get to the inside of the cassette (11-34), i don't think it's something that's well configured for long-term use right now.
I just went and looked at it again to make sure i remembering it correctly. The chainline right now should be at 47.5mm given the spacer arrangement i've got (just a single 2.5mm on the drive-side). The chain is about as perfectly straight (parallel to the wheel) as it can be when on the big chainring and the smallest cog.
I think what i'm probably looking at is swapping out this deore crankset for a Sugino configured with the same chainrings. I've never had to fit a bottom bracket spindle properly before although i called a shop near me, explained the situation and they told me that a 110 was most likely what i would need.
My frame is similar in measurement to a 62cm Surly LHT and i keep seeing people post of positive results with a LHT frame, XD600 triple crank and a 110mm spindle.
UPDATE: Forgot to mention my intended use for the bike! I'm going to be primarily on the big (48t) chainring using the middle every so often and the granny for the hills when i'm loaded (my panniers ;) )) Most likely - flat rolling hills and some steep (but slow) uphill.
05-24-09, 04:41 PM
Just got back from a test ride and all is good.
I went to the shop yesterday and got a Sugino crankset with 48-36-26 chainrings and a Shimano 68/110 bottom bracket, deinstalled the deore, installed the Sugino, torqued to spec, adjusted the derailleur and i was all set, took about 15 minutes in total. I should have done this from the get-go and i would have saved a bunch of money in the process.
I was just riding out through a park where the roads are closed on Sundays so i could move around and test everything out. I found some traffic lines and centered it up right on the lines - i couldn't hear the chain at all, it was dead silent and the shifts were nearly as quiet. This is the quietest bike i've ever ridden. Visually the chainline appears to be dead on. The big ring is right about at the 2nd cog of the cassette.
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