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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 11-05-08, 02:54 PM   #1
Cacti Dodger
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switch from 53/39 to compact - how? tools?

right so i have a felt55 with a 53/39 ultegra chainset. just moved to very mountainous region with massive hills and virtually no flats. went for a few rides and definitely could do with a few lighter gears. so i just bought a 105 compact chainset. The only problems is i will have to change the chainset all by myself. i am technically inclined and don't mind doing it but am quite inexperienced - my questions are:

- do i need any special tools?
- is there any step-by-step guide somewhere maybe with pictures that i can follow?
- any advice, tips, tricks, stuff i should be aware of?

thanks,

cd
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Old 11-05-08, 03:03 PM   #2
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This is a link to the Park Tool website's repair/overhaul for the cranks, which you'll be needing to remove:

http://www.parktool.com/repair/byreg...ageField2.y=14

This is an excellent resource for aspiring mechanics for all things bicycle. They have section for many other repairs, etc. Here is their front page:

http://www.parktool.com/repair/

Lists of tools are given on this site as well. You'll have questions, of course, so do return and ask. You didn't mention what sort of cranks/bottom-bracket you have on your bike at present. If you could give us all this info, people here can more quickly figure out what needs doing.

Good luck!
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Old 11-05-08, 03:41 PM   #3
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Are you swaping out the chainrings or changing the crankset completely.
If it is the crankset, you want to make sure that your old cranks and your new ones both use the same kind of bottom bracket. If it is the newer type outboard bearing bb i think all you need to do is remove the non-drive side crankarms with an allen wrench and pull it apart.

If your 53/39 is an octalink and your newer crank is the newer integrated type, you will have to buy a new bottom bracket...as well as the tools to remove the old one and install the new one.
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Old 11-05-08, 04:04 PM   #4
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Indeed - or have your LBS do the job for you and avoid purchasing tools. Unless you wish to learn mechanics and become self-sufficient regards bicycles.
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Old 11-05-08, 06:52 PM   #5
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Quote:
Originally Posted by Cacti Dodger View Post
right so i have a felt55 with a 53/39 ultegra chainset. just moved to very mountainous region with massive hills and virtually no flats. went for a few rides and definitely could do with a few lighter gears. so i just bought a 105 compact chainset. The only problems is i will have to change the chainset all by myself. i am technically inclined and don't mind doing it but am quite inexperienced - my questions are:

- do i need any special tools?
- is there any step-by-step guide somewhere maybe with pictures that i can follow?
- any advice, tips, tricks, stuff i should be aware of?

thanks,

cd
I'm thinking that you can do it with an 8mm allen wrench, a 5mm allen wrench and a chain breaker.

Your Ultegra crankset should be self extracting. Use the 8mm allen wrench and a good amount of torque to remove the old cranks.

Installing the new compact crankset is the reverse. lightly grease the crank spindle interface, be positive that the splines are aligned and reinstall the crank bolts. The torque spec on the crank bolts is 30 lb/ft. That's a good amount - probably more than you can achieve with just a 6 in long allen wrench. If you don't have access to a torque wrench, use a piece of tubeing for an extension and imagine a 30 lb weight hanging off of a foot long wrench.

Use the 5mm allen wrench to lower your front derailleur.

Shift into your little/little sprocket combination to check your slack take up. When I did mine I had to shorten my chain by an inch.
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Old 11-06-08, 04:44 AM   #6
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If the OP has purchased a new 105 crankset then it's probably the external bearing bottom bracket type. If the Ultegra cranks are also the Shimano external BB bearing Hollowtech type you will need a 5mm allen key and not a huge amount of torque - just enough to overcome the 12-15Nm it was torqued up to.

First remove the chain (since you are going to need to shorten it. Otherwise you wouldn't need to remove it). You will then need the plastic tool to unscrew the cap on the non-drive crank arm. (You may have got one included for free with the new 105 crankset). Unscrew that. Then loosen both 5mm crank bolts. Unscrew and completely remove the outer of the two crank bolts. With a small screwdriver or similar, flip up the little black metal plate between the crack on the non-drive crank (it pivots on the back crank bolt). Keeping the plate up, gently pull the non-drive crank off. Then you can push the crank axle through towards the drive side (it's all one piece with the drive crank). If it sticks part way through, ensure it isn't catching on something, then tap the end of the axle with a block of wood to encourage it.

Installation is really the reverse. Push the new crank axle through from the drive side (assuming you are keeping the old BB), grease the splines, push on the non-drive side crank arm, ensuring the little metal plate sits down correctly, screw on the cap on the crank to pull the crank arm fully onto the axle (finger-tight is fine), then alternately tighten the two crank bolts a little at a time. Torque them up to 15Nm which is a pretty hard turn on a 3" allen key, not quite so hard on a longer key. Double check tightness (and again after you ride it a bit)

Lower the derailleur height as Retro Grouch said, so it is just above the new (smaller) 50T chain ring. This will screw up the adjustment of the FD cable so you will have to adjust the cable to compensate.

Shimano have downloadable PDFs with instructions for each crankset type on their website. Look under Cycling/Technical Documentation/Road Bike/105 (Ultegra is identical). Click Here and here

In all seriousness changing the cranks is easy. You will probably do more cursing shortening the chain and getting the FD adjustment right.

Last edited by scirocco; 11-06-08 at 05:15 AM.
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Old 11-06-08, 04:16 PM   #7
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thanks all for the useful replies! i will have a go at trying to change them myself. I would very much like to learn how to do it quickish and alone so i would be abele to switch between the two chainsets when necessary without too much fuss.

i am not sure what exactly type of bottom bracket i have, but if helpful here are the specs of my bike with the original ultagra:http://www.feltracing.com/08/product...,1515&pid=8663 - it is a 2008 model. The 105 i bought looks very much like this: http://www.bike24.com/images/products/p015047.jpg.

thanks again for the tips - will let you guys know how it works.

cd
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Old 11-06-08, 05:47 PM   #8
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that's an outboard type, the 5mm allen key will do.

just remember, when removing the non-drive side arm, there's a small lever arm with a pin that keeps the arm from just falling off when not tightened down. simply lift the arm up with a flat screw driver to allow it to slide off.
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