replacing chainrings on SLX double chainset

armymankin

Hi all,

Currently have a SLX double (36/22) and i am think of getting bigger rings as my legs get bigger (yea right ) and i think i could a little higher ratio than 36-11

I am just thinking is it worth getting the rings replaced to 39/26 like the SRAM double chainsets, or shall i just get a new chainset instead.

currently running 11-34 cassettes at the rear. knowing if i buy the new SRAM then it is a lot of work to get into the 10speed system.

if just replacing the rings then what shall i do and which rings shall i fit? i heard rumours of not all chainrings would fit the SLX double crank, is it true? i have no clue, first time doing this job

thx guys
kin

Anonymous

well, new chainrings will be cheaper than a new chainset, so...

armymankin

yea, that is what i think, just to replace the chainrings. I am hesitating because shimano must have a good reason while keeping the chainset at 36/22. I am not sure if it is a good thing to replace different size rings to it.
also, would any rings with 4 holes fit onto it?

thx

nicklouse

I run 38/28 and 38/26 on two bikes. as long as the BCD is correct there is nothing that a file can not fix.

armymankin

nicklouse wrote:

I run 38/28 and 38/26 on two bikes. as long as the BCD is correct there is nothing that a file can not fix.

thanks man,

Bone question here.... what does BCD stand for? :oops:
yea, i was wondering, because shimano SLX has 2 sets of chainrings, the M660 (triple) and theh M665 (double).... i assume they are not compatible to each other despite both of them has 4 holes. just dont want to buy things that wont fit.

lonzo

I didn't know either so I looked it up on wikipedia! enjoy!

http://en.wikipedia.org/wiki/Crankset

Bolt circle diameter (BCD)Many modern bicycles have removable chainrings, to allow for replacement when worn, or to change the gear ratio provided (although the change is limited).

The holes on the spider arms used for attaching a chainring can have a variety of dimensions, referred to as the bolt circle diameter, commonly abbreviated as BCD. This measurement is sometimes referred to as pitch-circle diameter (PCD). Cranks designed to mount one or two chainrings will almost always use a single bolt circle diameter. Cranks designed to mount three chainrings will almost always use two different bolt circle diameters; the larger to mount the two outer rings and the smaller to mount the inner ring. Most modern two-chainring cranks use either a 110mm or 130mm bolt circle diameter.

Bolt circle diameters of common "named" cranks:

lonzo

I didn't know either so I looked it up on wikipedia! enjoy!

http://en.wikipedia.org/wiki/Crankset

Bolt circle diameter (BCD)Many modern bicycles have removable chainrings, to allow for replacement when worn, or to change the gear ratio provided (although the change is limited).

The holes on the spider arms used for attaching a chainring can have a variety of dimensions, referred to as the bolt circle diameter, commonly abbreviated as BCD. This measurement is sometimes referred to as pitch-circle diameter (PCD). Cranks designed to mount one or two chainrings will almost always use a single bolt circle diameter. Cranks designed to mount three chainrings will almost always use two different bolt circle diameters; the larger to mount the two outer rings and the smaller to mount the inner ring. Most modern two-chainring cranks use either a 110mm or 130mm bolt circle diameter.

Bolt circle diameters of common "named" cranks:

nicklouse

shimano 4 bolt are 104mm. and 64mm

more info in the links in my sig.

armymankin

great! thanks chaps. learn something new everyday.
one last question. for the M8 star bolts on the shimano chainset, which tool shall I use? it is unlike allen key measured in mm, the star torx key in measured in T?? it has me confused here. :roll:

nicklouse

it is torx as you say unfortunately sorry I forget the size.

cat_with_no_tail

nicklouse wrote:

it is torx as you say unfortunately sorry I forget the size.

T30

njee20

Most modern two-chainring cranks use either a 110mm or 130mm bolt circle diameter.

That's road compact and standard, MTB 'standard' chainsets are 104/64 as Nick says, however SRAM doubles are different, and XTR double is something different again!

No reason not to change rings though, TA Chinook do every size you could want. I liked 28/40.