Changing the crank? (Stories of the Noob)

Dec 17, 2011
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kanazawa
#1
Hello people,

I've been thinking of changing the crank of my Giant Defy 3, from an FSA not-sure-what-it-is-but-looks-cheap (edit: it looks like it's an FSA tempo 34/50T ) to an 105 compact double crank. The only problem is that the bike's mech is the 2300 8-speed shimano stuff, but the 105 is designed for 10 speed sets.

So, I thought of taking off the chainrings of the 105 crank and use the chainrings from my current crank. Do you think that this could work? Are chainrings for compact cranks interchangeable? They do look so in my untrained eye...

Another point I'll have to consider is changing the BB. Browsing on sagamicycle I only saw two types of BB, the "JIS" size and the "italian" size, I guess I have to go with the JIS one?

The reason I want to do this is because the current crank feels.. mushy/flexy and because further down the line I want switch to a full 105 set, but don't have the cash to do it all at once. Any insight would be welcome! Cheers!
 
May 22, 2007
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halffastcycling.com
#2
I think you'd be setting yourself up for problems. You might conceivably get it to work if the chainrings can be transplanted. Otherwise - running an 8 speed chain on 10 speed chainrings - I'm not sure what would happen. Could be fine until you put the pressure on and then the chain starts dropping off exactly when you least need it to.

I had a cheapo FSA crank on my (now deceased) Felt F4C. Everything else was Ultegra except the DA rear mech. What a mongrel! After I while I got a kosher Ultegra crank for it and that was much nicer. After t-boning a van and trashing that frame I moved everything over to my new GS Astuto carbon frame... which then went swimming.

I would think it better to wait and get the 105 all at once. It's (only) ¥50,000 these days. It will transform your bike! I've got 105 on the titanium bike.
 

FarEast

Maximum Pace
May 25, 2009
5,528
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Yokohama
#3
Totally agree with Mike.

Also one of the other issues is that FSA cranks is that they use a different bottom bracket cup system than SRAM and Shimano. (The only difference between JIS and Italian is the direction of the threads)
 
Sep 2, 2009
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#6
Ah good idea. Yeah, Yahoo Auctions is great for this kind of thing. That is massively cheap. Wonder what the bidding will end on. Will keep an eye on this for interest!
 
Dec 17, 2011
267
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kanazawa
#7
Thank you all for your replies, appreciate it!

First, the auction looks good, but I have a feeling it's maybe going to go north of 40.000yen by the end.

Second, I do want to switch to an 105 set but, just can't put the money down all at once. In light of this, I think I will pursue the option of getting just the crank for the time being, and try to "transplant" the chainrings.

Best case scenario: the transplant is successful and I'm happy.

Worst case scenario: the rings don't fit, can't use the crank right away and have to wait a few months till I gather all the other parts. I think I can live with that..

Sheldon Brown seems to imply that chainrings are pretty much standardized these days, as long as I keep to the same type of crank (in this case a compact one), so maybe there's still hope that the transplant will work.

I'll be probably placing an order in the next couple of weeks, let's see how that'll turn out..
 
Sep 2, 2009
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#8
It is highly unlikely you will be able to swap out the rings on a 105 crankset. The only time I have seen anything other than Shimano rings on a recent Shimano chainset is when something custom has been made (I believe FarEast has a custom ring set on his Dura Ace 7900 cranks, and can testify to this).

Honestly, I think you are going to get into bother with this if you don't do the whole lot at the same time. You could compare the chain on your bike with a 10 speed 105 chain to see if the pitch and width is the same, then make a decision based on how close they are.

What BB do you have in your frame at the moment?
 
May 22, 2007
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halffastcycling.com
#9
Yeah, I third what Mike said; 48,519yen and you get yourself a complete groupset which you can install once and forget, delivered to your door.
Cassette
Chain
F Mech
Shifters
Chainset
R Mech
This will also save you a HUGE amount of fannying about.
Or buy from Rakuten and get the brakes and BB, too, for only a few dollars more than that pick 'n' mix at Wiggle. The 105 brakes and 105 brifters are designed to work together, and it does make a difference in the stopping power and modulation.

Shiny.

proxy.php?image=http%3A%2F%2Fthumbnail.image.rakuten.co.jp%2F%400_mall%2Fmapsports-syuppin%2Fcabinet%2F1183848%2Fshimano105-5700_sil.jpg&hash=c53a075e39e244d92688928b2a93e14c
 

GSAstuto

Maximum Pace
Oct 11, 2009
945
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tokyo
www.roadfixie.com
#10
TA Specialties now makes and sells replacement rings for Ultegra level cranks. They work just fine on all shimano cranks, btw, but just cosmetically matched to the 6700s. Very nice if you are looking for combos not usually available or reasonably priced , or you wear them out quickly.

It is highly unlikely you will be able to swap out the rings on a 105 crankset. The only time I have seen anything other than Shimano rings on a recent Shimano chainset is when something custom has been made (I believe FarEast has a custom ring set on his Dura Ace 7900 cranks, and can testify to this).

Honestly, I think you are going to get into bother with this if you don't do the whole lot at the same time. You could compare the chain on your bike with a 10 speed 105 chain to see if the pitch and width is the same, then make a decision based on how close they are.

What BB do you have in your frame at the moment?
 

FarEast

Maximum Pace
May 25, 2009
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#11
It is highly unlikely you will be able to swap out the rings on a 105 crankset. The only time I have seen anything other than Shimano rings on a recent Shimano chainset is when something custom has been made (I believe FarEast has a custom ring set on his Dura Ace 7900 cranks, and can testify to this).
Yes I run customised Dura Ace 7900 with Stronglight chain rings - However there are plently of optional chainrings out there that will fit both 110 and 130 BCD cranks, however they may look rather nasty due to the design of the Shimano spider on the cranks.

Also to be honest, you're probably looking at paying the same amount in chainrings as you would a brand new pair of Shimano 105 cranks with BB.
 
Dec 17, 2011
267
8
38
kanazawa
#13
Honestly, I think you are going to get into bother with this if you don't do the whole lot at the same time. You could compare the chain on your bike with a 10 speed 105 chain to see if the pitch and width is the same, then make a decision based on how close they are.

What BB do you have in your frame at the moment?
Aaah... I ... .must be patient.... and get the whole thing at once...

The BB is a .. square taper-thingy, internal, that I'm not quite sure about... and of course not compatible with the 105 crank so it has to be changed too.
 

m o b

Speeding Up
Jun 22, 2008
341
23
38
Bremen
cyclitis.wordpress.com
#14
If you really want to change the crank only, you could do that by changing the bottom bracket from a square taper to a Shimano 105 one (probably with external cups) which isn't too expensive, mount the 105 crank set and use a new 8 speed chain.

For the bottom brackets, there are two (old) standards, BSA which is for 68mm brackets left and right threads and a little smaller diameter and ITA which is for 70 mm brackets right and right threads and a little bit bigger diameter.

I am pretty sure that your Giant has BSA standard 68mm.

Also there is a JIS and ITA standard for the square taper, your FSA will be JIS standard but it doesn't matter anyway because your new 105 crank has no square taper.

You can run a 8 speed chain on a 10 speed chain ring but not vice versa. Zero problem in my opinion. I have ridden similar setups. OK, this is not the manufacturers recommendation but it works well.
 

Sheep

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Jul 27, 2009
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#15
Just want to say this thread has been really useful for me, as I'm in a similar situation with my Defy 3. Started with a need to replace the wheels (screwed hubs, long story) and then thinking about compatibility issues leading to thinking about upgrading the group set (probably to Tiagra).
 

FarEast

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#16
Seriously - though if you are going to upgrade then upgrade EVERYTHING in one go - living off cup ramen for 1 month is no real issue, we've all done it at least twice :D
 

Sheep

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Jul 27, 2009
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Tokyo
#17
Seriously - though if you are going to upgrade then upgrade EVERYTHING in one go - living off cup ramen for 1 month is no real issue, we've all done it at least twice :D
(Sorry to threadjack, but it is still related to the original poster)

For my upgrade, I can afford to go Shimano 105, but this is not my 'nice' bike and often has to be left parked outside at work, so I'd rather not spend too much money on it. I've only experienced the Defy's 2300s and the 105 on my other bike. How huge is the difference between tiagra and 105 (or between 2300 and tiagra)?
 
May 22, 2007
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halffastcycling.com
#18
How huge is the difference between tiagra and 105 (or between 2300 and tiagra)?
I think the main differences between Tiagra and 105 are that Tiagra (1) still does not have along-the-bar routing for shift cables and (2) still has those tacky indicators to indicate what gear you're in. There's a slight weight advantage, I expect. There were rumors of the 2013 Tiagra changing the cable routing - that's rumors for ya.

I have 2005 9S Tiagra (still going strong), 2006 10S Ultegra (replaced various bits) and 2011 10S 105.
 

Sheep

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Jul 27, 2009
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#19
I think the main differences between Tiagra and 105 are that Tiagra (1) still does not have along-the-bar routing for shift cables and (2) still has those tacky indicators to indicate what gear you're in. There's a slight weight advantage, I expect. There were rumors of the 2013 Tiagra changing the cable routing - that's rumors for ya.

I have 2005 9S Tiagra (still going strong), 2006 10S Ultegra (replaced various bits) and 2011 10S 105.
Ah yeah, those indicators are there at the moment and are rather unnecessary. Hmm, the price difference isn't THAT much I suppose...
 

joewein

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Oct 25, 2011
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joewein.net
#20
I think the main differences between Tiagra and 105 are that Tiagra (1) still does not have along-the-bar routing for shift cables
There's an upside and a downside to the Tiagra vs. 105 cable routing.

While the under-the-tape routing of the derailleur cables on the current 105 looks cleaner, has less potential for obstruction of handle bar bags, lights, etc. and an ever so slight advantage on aerodynamics, it involves more or sharper bends in the cable path, which can mean marginally more friction and cable wear. For that reason Shimano specifies PTFE (teflon) coated derailleur cables for the current (5700) 105, but not for Tiagra or the older "5600" 105, which is what the current Tiagra is based on.

The difference in cable routing is also the reason why my Bike Friday folding bike has Tiagra shifters while the rest of the group is 105. Basically it needs the extra flexibility from external routing when folding the handle bar, plus with the folding mechanism the routing is less direct already, so more bends along the bars would not be welcome. I heard that when the 6700 Ultegra replaced its 6600 predecessor and Shimano first moved the shifter cables under the bar tape, Bike Friday stopped offering Ultegra to avoid problems for its customers. Ultegra only became available again when Ultegra Di2 came along, since it uses electronic shifting and the electric cables don't care about how they are laid.
 
Likes: Sheep