Changing a crankset

[steveindenmark]

Im sorry if this is something you all think I should know how to do. But I thought I would ask the questions before I start spending money.

At the moment my bike has a Shimano Tiagra FC 4403 52x42x30T crankset and Shimano CS HG50 9 speed cassette.

I want to keep the cassette as it is but change the crankset to a Shimano FC-T551 48x36x26 Crankset.

I am capable of actually changing a crankset but am not knowlegable enough with bikes to know the practical implications.

Would this be a straight swap over or would it mean altering the chain or rear cassette and dialling in the gears, something I do not know how to do.

Any advice would be appreciated.

 

[Spoked Wheels]

Assuming both cracksets use the same type of BB then it's a straight swap.
The front derailleur would probably need adjusting as you would have less teeths in the proposed crankset so maybe slightly smaller chainring.
The chain would need adjusting too as it would be a bit too long. No indexing adjustment of the rear mech is needed though.

 

[raleighnut]

^^^^^+1

 

[I like Skol]

The chainset you already have appears to be a square taper bottom bracket while the proposed new chainset is a Hollowtech II model. This is no problem as the two bottom brackets will live in the same place but be aware that some people have had issues with short lifespan from the Hollowtech and this is often attributed to poor installation or poorly faced BB shell in the frame.

Swapping from one chainset to the other should have no effect on the rear gear shifting. the front mech will ideally need dropping down the frame a touch but it wont be much. The indexing and limit screws should be carefully set up to suit the new chainset as the chances of the chainrings being offset from the original set up is high. Your existing chain length should be fine (providing it is right in the first place) as the reduction in teeth count on the big chain ring of 4 teeth will equate to a 2 tooth difference seen by the chain, or 1 link, you can take this out if you are a perfectionist but it is unlikely to have any effect.

 

[ColinJ]

If the original chainset is square taper then take a look at the Stronglight chainsets at Spa Cycles. I bought a very nice 48/38/28 from them recently and they also do a 46/36/26 if you didn't mind losing 2 teeth from your proposed big ring.

 

[Nigelnaturist]

or from Spa their own crankset and choice your own rings.
crankset http://spacycles.co.uk/products.php?plid=m2b0s109p3051 £20
Spa chainrings http://spacycles.co.uk/products.php?plid=m2b0s210p0 £45 for all three and choose colour or silver or black and whatever size your happy with, its a 74/110 BCD crank, so £65 for the set though it has 113mm BB which you may need to change, but the rings are really nice and shift well, even a 26/38/50 a range of 24th

They go down to 24th on the inner if you want to go 24/36/48 should work.

 

[steveindenmark]

Thanks for you advice guys, it is appreciated.

I am a total newbie at taking cycles to pieces and want to make sure I am doing the right thing and using the correct tools before I start attacking my Koga. I am not worried about using tools, my other hobby is trying to restore vintage, single cyclinder Moto Guzzis. But I know from first hand experience about how to make a short job very long by using the wrong tools.

I remember a long time ago taking pedals off a bike but the cranks had square holes, my koga doesnt. I need a socket to fit the crank and have nothing which even resembles it in my tool kit. I do not even know the name of what I am searching for and am hoping someone can help me.

Here is a photo of my Kogas pedal crank.





Looking at what I have read so far, I can either change the entire cranks or just the rings. Is that correct?

If I change just the rings. Do all rings fit all cranks or am I looking for a specific make or type?

 

[raleighnut]

That's just a preload cap to set the bearings up correctly before tightening the 2 allen bolts that hold the non-drive side arm on. The dedicated bearing spanner I have comes with a plastic thingy that fits into that and has a knurled ring to grip with your hand to loosen/adjust the cap (hollowtech bearings)

 

[bikeman66]

It may also be the case that you might need to replace the cassette and chain too, as if they are showing any significant signs of wear it is highly likely that you'll find the chain jumping around a bit on the new teeth of the chainrings. It's good practice to replace chainrings, cassette and chain at the same time anyway to avoid any new v old compatibility issues. I used to think that was a line spun by component manufacturers to get you to spend more money, but experience tells me it is worth replacing all three as a unit.

 

[steveindenmark]

Bikeman the bike is less than 6 months old with only a couple of hundred km on it and so the everything on the bike is fine.

Raleighnut. I am not at all sure what you are telling me. Treat me like an idiot. I dont mind

Do I need a Hollowtech bearing spanner and if so where do I get one?

 

[raleighnut]

I got a Cyclepro external bearing spanner (might be a 8918 as that is the only No. on it) that has on the side an allen key for FSA crank caps and a plastic splined component that slides on for Shimano crank caps. The fastening method of these cranks is similar to how a threadless stem is attached in that its the 2 allen key bolts hold the non-drive crank to the splines on the centre shaft and the end cap is used to simply take all of the play out the bearings in the same way that the top cap does on a stem. Its best to take one or both of the bolts out as there is a plastic 'safety' fitting with a small tab that engages in a groove on the shaft as well. I've never needed any 'puller tool' to get these cranks off so I'd say undo and remove both the 2 allen bolts on the crank arm, remove the centre adjuster cap (its only finger tight) and use a rubber mallet to tap the shaft with the drive side crank and rings through.
As for where to get one mine came from my Local Bike Shop and cost about £15 but 5 of my bikes have been fitted with this type of crank (by me) so I needed the spanner.

 

[steveindenmark]

I will probably need this and the spanner to go along with it.

http://www.amazon.com/Shimano-Hollowtech-II-crank-arm-tool-TL-FC16/dp/B000F5JOT8

 

[raleighnut]

I will probably need this and the spanner to go along with it.

http://www.amazon.com/Shimano-Hollowtech-II-crank-arm-tool-TL-FC16/dp/B000F5JOT8

That's the thing for the cap.
If you google 'cyclepro external bearing bottom bracket spanner' you'll see the one I have at £14.99 this has the plastic cap tool on the side of the spanner but is only needed if 1 you're changing the bearings, 2 the bearing is threaded and not a press fit into the frame.
The Park tools website has a good description/how to page but the spanner is more expensive (just delete cyclepro from the front and search again)

 

[RecordAceFromNew]

Im sorry if this is something you all think I should know how to do. But I thought I would ask the questions before I start spending money.

At the moment my bike has a Shimano Tiagra FC 4403 52x42x30T crankset and Shimano CS HG50 9 speed cassette.

I want to keep the cassette as it is but change the crankset to a Shimano FC-T551 48x36x26 Crankset.

I am capable of actually changing a crankset but am not knowlegable enough with bikes to know the practical implications.

Would this be a straight swap over or would it mean altering the chain or rear cassette and dialling in the gears, something I do not know how to do.

Any advice would be appreciated.

Am not sure why you want to swap the chainset, or whether the existing is a Tiagra (in the OP) or 105 (as shown in the photo attributable to a Kona), but one thing you might want to be aware of is that the road chainsets (such as a Tiagra or 105) and the FC-T551 don't have the same chainline. This can have implications, e.g., if your existing front mech can't reach an extra 5mm outboard.

Whether you can just swap rings or not dependent on the bcd of the chainset's spider. What is the model of the existing chainset?

If I were you I would get a HT2 bb tool like this. They are far less likely to chew up the alloy bb cups than the ones that look like a spanner.

 

[Cubist]

Stop! You only need a HT bottom bracket tool of you plan to change the Bottom Bracket. The crank itself needs a 5mm hex key to undo the pinch bolts, a 20p piece to undo the nylon preload cap, wiggle the crank arm off the non drive side splined axle and then tap it through with a rubber mallet. That's it.