Shimano SLX Chainring Compatability

iLukeKendall

Last week, I had my drivetrain upgraded to Shimano SLX by the LBS. Unfortunately, I made the mistake of assuming they would replace the components like-for-like, however I've ended up going from a 44/32/22 setup to 40/30/22, and I'm really noticing the difference.

I'm wanting to replace the outer chainrings to 44t and 32t, although I'm a bit confused as to which chainrings will be compatible. On my receipt, it says that the chainset is M675 10spd, however when I looked at Shimano's Tech Docs, it appears this is the double crankset - I have a triple crankset which I think must be M670.

I've tried searching for chainrings for those part numbers, however it doesn't appear that 44t is available.

Can anyone suggest chainrings that would be compatible?

Many thanks!

BigAl

Chain Reaction have SLX in 32 & 42

But, being 104 BCD, there's lots to choose from. Not for me to say but do you really need a 44T ring?

iLukeKendall

BigAl wrote:

Chain Reaction have SLX in 32 & 42

But, being 104 BCD, there's lots to choose from. Not for me to say but do you really need a 44T ring?

Thanks BigAl - would this mean I'd also need to find a 24 somewhere to keep the combination as Shimano suggests?

I've been referring to this Shimano tech document, and the impression I get is that I'd have to have either 24/32/42 or 26/36/48, with part numbers M670, M780 or M660-10.

http://techdocs.shimano.com/media/techd ... 801179.pdf

As for the 44, I guess I could probably make do with a 42. It's just part of my ride is a 5 mile Tarmac paved path with a slight downhill gradient, and I often found myself in the 44 chainring hitting stupid speeds coming back! Kinda missing that at the moment with the 40t.

BigAl

No need to change the little ring.

Personally I would run the rings you have from your lbs. Sound a perfectly reasonable combo to me.

Change rings if you need to extend the gear range.

You don't need to stick to the 'stock' combinations mentioned in the tech docs.

Chunkers1980

Out of interest how much did you pay them for this swop?

taffygriffiths

i woud imagine this:
http://www.chainreactioncycles.com/shim ... prod108983
is what you have been given.

just seems to be a lower ratio version of the M675 chainset.

one website suggested that it is better for 27.5/29" wheels.

As it is essentially a 10 speed chainset, then eash ring is only 2 teeth smaller than the 'std' ones. (24/32/42)

by the sounds of it, you had a 9 speed chainset which i believe to be 22/32/44. possibly why you're seeing such a difference.

I would just give it a go. i took my big ring off completely!

iLukeKendall

Thanks for the advice guys.

I spoke to Madison, the main UK Shimano dealer today, and it turns out I have an M672 crankset, which is 22/30/40.

They told me that it's compatible with M670 chainrings, and the only option would be to go to 24/32/42. It's a shame they don't do a 44t that's compatible, but at least the 24t might be more useful than the current 22t.

I'm limited to those rings because it's a Shimano Dyna Sys drivetrain, so they have to have specifically shaped teeth or something I believe.

I've managed to find someone selling brand new 24/32/42 M670 rings on Singletrack forum, which he's sending me tomorrow. They were brand new and taken straight off new cranks, so I've made a reasonable saving compared to retail prices.

As for the smaller rings being better for a 29er, I'm not finding this the case. I feel like I'm having to put a lot more effort into pedalling and not being able to reach the speeds I was able to previously.

Which brings me onto my next question...

My current setup is 22/30/40 - will I need to adjust the length of the chain to accommodate the larger ring? If so, by how much? The bike shop didn't give me any extra links, and the chain is Dyna-Sys specific so I don't know what my options would be to extend it?

I'm also assuming I'll need to move the front derailleur up slightly to accommodate the larger ring?

cooldad

Measure round big/big without going through the mech and plus a link. You can probably add a bit in with some quick links but ideally a new chain if it's too short.

iLukeKendall

cooldad wrote:

Measure round big/big without going through the mech and plus a link. You can probably add a bit in with some quick links but ideally a new chain if it's too short.

Damn, I was hoping not to buy another new chain as this one is only 40 miles old! Do you think going from a large to large ratio of 38:40 to 38:42 would require more than a single quick link to be added?

I can't measure until the chainrings come, and I don't really want to be waiting on a new chain before I can use my bike

Chunkers1980

Quick links will be fine.

supersonic

Or use a 9 speed SLX chainset. Has the ratios you want. Is compatible.

iLukeKendall

Chunkers1980 wrote:

Quick links will be fine.

Thanks, would one be enough? I'm guessing it's not possible to daisy-chain missing links anyway as they're female to female?

supersonic wrote:

Or use a 9 speed SLX chainset. Has the ratios you want. Is compatible.

I've literally just spent £275 on 10 speed SLX groupset, so I'd have to change everything again to go back to 9 speed! I've managed to find the ratios I want now anyway, with the exception of a 44t, but a 42t should at least be an improvement over the 40t.

Chunkers1980

No, you need some middle bits from cuts offs, and to measure it properly

supersonic

You'd have to change just the chainset. They work fine with 10 speed parts.

iLukeKendall

Chunkers1980 wrote:

No, you need some middle bits from cuts offs, and to measure it properly

Ah, that could be a problem. The bike shop shortened the chain and will probably have binned the excess by now. Not only that but it's a Shimano HGX directional chain, so putting in multiple chain links probably isn't ideal.

It's probably safer just to order a new chain - at least it's not as expensive as I thought it would be at about £15 on CRC. I'm assuming I can then just measure, disconnect the excess, and join it with a single KMC quick link?

supersonic wrote:

You'd have to change just the chainset. They work fine with 10 speed parts.

Hmm, too late now anyway, already paid for the new chainrings. Still wouldn't be practical spending out extra for cranks as well. I also can't see how 9 speed parts can work with 10 speed parts - isn't the 10 speed chain narrower, so it wouldn't fit on the 9 speed chainring?

supersonic

It still works fine - I tested all this kit for WMB ;-).

The Rookie

iLukeKendall wrote:

They told me that it's compatible with M670 chainrings, and the only option would be to go to 24/32/42. It's a shame they don't do a 44t that's compatible?

As far as I know Shimano have never done a 44T big ring, that's a SRAM thing, Shimano have been 42T or 48T for trecking.

For the sake of the 1/3 of a gear difference (spaces between gears is about 12-15%) frankly I wouldn't bother anyway.

iLukeKendall

The Rookie wrote:

iLukeKendall wrote:

They told me that it's compatible with M670 chainrings, and the only option would be to go to 24/32/42. It's a shame they don't do a 44t that's compatible?

As far as I know Shimano have never done a 44T big ring, that's a SRAM thing, Shimano have been 42T or 48T for trecking.

For the sake of the 1/3 of a gear difference (spaces between gears is about 12-15%) frankly I wouldn't bother anyway.

My old crankset was a Shimano Alivio and that definitely had a 44t big ring!

As for not bothering, do you mean not bother changing chain rings or extending the chain?

Ouija

All my Deore and SLX mtb cranksets have 44T rings. Last time i saw Shimano using 42t outers on triples was back in the 8 speed days.

As for lengthening the chain, there probably isn't a need in most cases. A lot of people set up the chain long enough so that you can have it on the big ring at the front and the big ring at the back without over extending the derailleur. However, it's not a good idea to use those combinations as it wears the chain out, so you can often get better performance by shortening the chain so that it doesn't rattle and slap the chain stays as much (often gives tighter shifting over bumpier ground). So, i'd try it with the shorter chain first and just try to avoid using the big/big combination.

supersonic

10 speed Shimano does not have 44. Some 9 did. Tehre was a curious 38/32/24 set up too!

The Rookie

iLukeKendall wrote:

The Rookie wrote:

iLukeKendall wrote:

They told me that it's compatible with M670 chainrings, and the only option would be to go to 24/32/42. It's a shame they don't do a 44t that's compatible?

As far as I know Shimano have never done a 44T big ring, that's a SRAM thing, Shimano have been 42T or 48T for trecking.

For the sake of the 1/3 of a gear difference (spaces between gears is about 12-15%) frankly I wouldn't bother anyway.

My old crankset was a Shimano Alivio and that definitely had a 44t big ring!

As for not bothering, do you mean not bother changing chain rings or extending the chain?

Not bothering changing the ring, it will add about 1-2mph at most to your top speed.