Bicycle Mechanics - Quick Question about Chainring

on my sirrus i have 48s/38s/28s on the crank. it has sora components. someone online told me that i can just swap out my 48s with a 52t chainring. then i would have to just raise the front deraileurs so the chain will clear and also get a longer chain.

now my questions are... first of all, is that doable to just change the 52t chainring? secondly, how long of a chain would i need? can i still use my exisiting chain and just have lbs add some more links to it? how do you measure how long u need? what about what kinda chainring will fit? is there a measurement of some kind for chainrings?

thanks
rui

Generally it is a safer idea to put a new chain on. Measuring out a chain for a chainring is easier to see by eye than to describe in words, because of the number of variables in the equation.

Generally it is a safer idea to put a new chain on. Measuring out a chain for a chainring is easier to see by eye than to describe in words, because of the number of variables in the equation.

ok.. that's what i thought. guess i'll bring it to my lbs to get them to do the job then. but other than the chain part.. i shouldn't have any problems with changing the chainring right?

What cassette do you have in the rear? You need to make sure you won't exceed the chain wrap capacity and front difference rating on the rear derailleur.

What cassette do you have in the rear? You need to make sure you won't exceed the chain wrap capacity and front difference rating on the rear derailleur.

here is the specs:

CASSETTE: Shimano HG-50, 8-speed, 12x25t

CHAIN: Shimano HG-53

CHAINRINGS: 48Sx38Sx28S, Super Shifter

here is the specs:

CASSETTE: Shimano HG-50, 8-speed, 12x25t

CHAIN: Shimano HG-53

CHAINRINGS: 48Sx38Sx28S, Super Shifter

Okay... according to the information I have on the Sora rear derailleur:



Speeds 8-speed
Max. Sprocket 27T (GS)
Min. Sprocket 11T
Front Difference 22T (GS) 14T (SS)
Total Capacity 37T (GS) 29T (SS)


So given that...

Chain-wrap capacity = (large chainring - small chainring) + (large rear cog - small rear cog)

(52 - 28) + (25 - 12) = 37

So it looks like you're okay on the wrap capacity. Hopefully you've got a GS rear derailleur which I believe you do have since you already have a triple. You are however going to be exceeding the front difference by 2T though. This may be okay... I'm not sure.

Okay... according to the information I have on the Sora rear derailleur:



Speeds 8-speed
Max. Sprocket 27T (GS)
Min. Sprocket 11T
Front Difference 22T (GS) 14T (SS)
Total Capacity 37T (GS) 29T (SS)


So given that...

Chain-wrap capacity = (large chainring - small chainring) + (large rear cog - small rear cog)

(52 - 28) + (25 - 12) = 37

So it looks like you're okay on the wrap capacity. Hopefully you've got a GS rear derailleur which I believe you do have since you already have a triple. You are however going to be exceeding the front difference by 2T though. This may be okay... I'm not sure.

thank khuon, that's good info there! now all i need to do is to find out if my 48t chainring is a 130mm or not. i've lost the link about how to measure between the mounting holes to determine the diameter for shimano chainrings. :(

ok... i took a close look at the 48t chainring. i think the BDC is 110mm with 5 bolt pattern. so is there an online shop what sells Shimano 110mm 52T chainrings?

ok... i took a close look at the 48t chainring. i think the BDC is 110mm with 5 bolt pattern. so is there an online shop what sells Shimano 110mm 52T chainrings?

http://store.airbomb.com/ba/asp/ic.CR4033/ab/Itemdesc.htm

http://store.airbomb.com/ba/asp/ic.CR4033/ab/Itemdesc.htm

sweet! thanks khuon.. for a while i thought only shimano brands will work.
who makes the FSA? are they about the same par as shimano?

in that case.. what about this one? will this work as well?

Sugino Chainring 52T/ 110mm (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3687689331)

sweet! thanks khuon.. for a while i thought only shimano brands will work.
who makes the FSA? are they about the same par as shimano?

FSA makes FSA. They're a small company that's made great inroads into the component market. They're actually based not far from me in Kenmore, WA and I've met some of their executives since they're friends with the folks at my FBS. Check out their website (http://www.fullspeedahead.com/). Some people tell me that the FSA rings won't shift as nicely as Shimano rings but I haven't been able to tell the difference between the FSA ones (39/53) on my roadbike and the Shimano Dura-Ace rings I've tried on other bikes.



in that case.. what about this one? will this work as well?

Sugino Chainring 52T/ 110mm (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3687689331)

It'll work but not as well. The old Sugino rings didn't have shift pins so won't shift as smoothly as either Shimano or FSA.

[QUOTE=khuon]FSA makes FSA. They're a small company that's made great inroads into the component market. They're actually based not far from me in Kenmore, WA and I've met some of their executives since they're friends with the folks at my FBS. Check out their website (http://www.fullspeedahead.com/). Some people tell me that the FSA rings won't shift as nicely as Shimano rings but I haven't been able to tell the difference between the FSA ones (39/53) on my roadbike and the Shimano Dura-Ace rings I've tried on other bikes. [QUOTE]

Khuon.. thanks for the info! i'll give that a try. besides their prices is not that bad either. thanks again!