Bicycle Mechanics - Does 10 speed truly require special cranks?

I have a 7 speed that I'd like to upgrade to 10 speed, all depending on cost. Currently has 52/39 Shimano 600 cranks (early 90's bike).


Question:
If I already have 10 speed shifter (ultegra SL), rear derailer (ultegra), 10 spd chain and cassette (105), can I just run my current cranks (originally 7 speed bike)? Would I need to change the FD?
Also, if I wanted to change to compact spending as little as possible, can I run the new Tiagra compacts (FC-4550) or do I need something "designated" for 10 speed?


Thanks.

I thought the new Tiagra compact crank was listed as a 9/10 speed.

Most likely the 10 speed chain will drop between the two chain rings, as the chain is significantly more narrow than the 7/8 speed you were running on it.

You may have to change the FD as well due to the narrower chain.

tiagra works fine with 10sp

spider thickness between 10sp 5600 105 and 7sp 6400 600 is the same, which is 3.5mm

the newer 9/10sp shimano chainrings do have better teeth designs so they shift way smoother.
even the tiagra compact shifts very smooth.

tiagra works fine with 10sp

spider thickness between 10sp 5600 105 and 7sp 6400 600 is the same, which is 3.5mm
Right, but Shimano's 9/10-speed inner chainring has the teeth offset toward the large chainring to narrow the gap. If the OP want to retain his current crank there are two options:

1. But a 9 or 10-speed inner chainring and replace the current one.

2. Keep the current crank as is but don't shift it under load. When 9-speed first came out Shimano's recommendation to those not wanting to upgrade their older cranks was to "always shift while seated". That assured you never shifted while the chain was under a big load and kept the chain from "skating" between the two rings.

I ride a 52/42 Zeus crank from the early 1980s with a Shimano 10sp chain without any problem. I'm using a Campy NR front derailleur from the same period. I just don't worry about front shifting problems since you don't go back and forth that much. All I ask is that the chain stays on when I shift, and in this case it does.

One thing that hasn't been mentioned here is whether you're planning to update your rear wheel (or at least freehub body) as well. If your bike is all 7-speed, you likely have a 7-speed freehub on the rear wheel, and 8/9/10-speed cassettes are wider than 7-speed cassettes so you'll need to at least update your freehub body in order to fit a 10-speed cassette on the bike.

Thanks all. I have a 7 speed cassette (not freehub) but I definitely will have to spread the frame to make the conversion. Glad to hear that the new Tiagra will work well with 10 speed though.

Glad to hear that the new Tiagra will work well with 10 speed though.

I have not had a good experience with using Tiagra with 10sp. I transferred my one-year-old Tiagra 9sp compact cranks onto my 10sp Ultegra bike to try out the compact gearing. The shifting was usually fine and smooth but occasionally the chain would drop between the rings. In fact I was going to start a thread here to discuss the pros and cons of grinding a small amount off the ring support lugs to shift the rings slightly closer together.

I have not had a good experience with using Tiagra with 10sp. I transferred my one-year-old Tiagra 9sp compact cranks onto my 10sp Ultegra bike to try out the compact gearing. The shifting was usually fine and smooth but occasionally the chain would drop between the rings. In fact I was going to start a thread here to discuss the pros and cons of grinding a small amount off the ring support lugs to shift the rings slightly closer together.

Scirocco - your Tiagra cranks, are they the 4550 (i.e. new model) or the older 44XX series crank?

Scirocco - your Tiagra cranks, are they the 4550 (i.e. new model) or the older 44XX series crank?

They are stamped FC-4550 and both rings appear to be genuine Shimano parts. They are installed facing the correct directions. The Tiagra bike is only a year or so old and was bought from a reputable LBS.

Like I say, most of the time the shifting was fine; just once every ten or twenty shifts the chain would slip between the rings. And this was not even shifting under load, out of the saddle or anything.

One day I'll get round to removing the rings and measuring the thickness of the lugs on the spider to see how they compare with 10-speed cranks.

Dropping when shifting NOT under load does not sound like a good thing.

Agreed, which is why I suggest that Tiagra FC-4550 cranks are not really 10-speed compatible at all. (They are now back on my 9-sp bike.) :)

I'll shill out the $ for a 10 speed compact, I guess. Anyone ever try SRAM Rival? Also, I found a website from UK (not PBK) that has decent prices, so I'll probably buy from there when I'm ready to make the conversion.

Thanks all. I have a 7 speed cassette (not freehub) but I definitely will have to spread the frame to make the conversion. Glad to hear that the new Tiagra will work well with 10 speed though.
A cassette is the type of gear unit that goes over a freehub body.
A freewheel is the alternative, where the gears are combined with the mechanism that allows backpedaling and coasting and they screw on together.
So if you are switching from a 7-speed cassette to a 10-speed cassette, you'll need to get a new (wider) freehub body and redish the wheel. Or just get a replacement rear wheel that came with the ride size freehub (8/9/10 speed compatible) to begin with.

One day I'll get round to removing the rings and measuring the thickness of the lugs on the spider to see how they compare with 10-speed cranks.

Well, I did exactly that today (I really need to get out more :) )

The ring mounting lugs on a Tiagra FC-4550 are 3.9mm thick, while the 10-speed spacing is only 3.5mm, so the 9-speed rings have a slightly larger gap between them. Nearly half a millimetre difference.

However, since Shimano sell the Tiagra as 9/10-speed, they must have got the Tiagra cranks to work okay with 10-speed chains. Perhaps the lugs on my set of Tiagra cranks are just out of tolerance. I may file them down a little to see if that improves matters.

Well, I did exactly that today (I really need to get out more :) )

The ring mounting lugs on a Tiagra FC-4550 are 3.9mm thick, while the 10-speed spacing is only 3.5mm, so the 9-speed rings have a slightly larger gap between them. Nearly half a millimetre difference.

However, since Shimano sell the Tiagra as 9/10-speed, they must have got the Tiagra cranks to work okay with 10-speed chains. Perhaps the lugs on my set of Tiagra cranks are just out of tolerance. I may file them down a little to see if that improves matters.

Scirocco, the Tiagra is marketed for 9 speed only. See link below.

http://bike.shimano.com/publish/content/global_cycle/en/us/index/products/road/tiagra/product.-code-RD-4500-SS.-type-rd_road.html

Well, someone needs to tell liquefied; New Crankset - Tiagra/105/Ultegra? (http://www.bikeforums.net/showthread.php?t=47150).

Hate to see anyone have an accident because they're running gear that's mis-matched.