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> Replacing worn chainring
pugster007
post Jan 8 2009, 08:54 PM
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From: Chester



Can I use any old 4-bolt, 22t chainring to replace the worn inner ring on my XT M770 crankset ?

Or do I have to check for certain other measurements like PCD, or Shimano compatibility ?

Thanks in advance,

Craig
(Suffering chain suck on every ride !)
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Mad Pierre
post Jan 9 2009, 09:03 AM
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From: Melton Mowbray



It'll need to be a 64mm BCD - that's the distance between the bolts that hold it on.

Most will fit but beware older granny rings for none external bottom brackets won't fit as they don't fit around the external bearings.

e.g. this won't fit: http://www.chainreactioncycles.com/Models.aspx?ModelID=5698

This will: http://www.chainreactioncycles.com/Models.aspx?ModelID=9232


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Doug
post Jan 9 2009, 04:42 PM
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From: Wrexham, N.E.Wales.



QUOTE(Mad Pierre @ Jan 9 2009, 09:03 AM) *
Most will fit but beware older granny rings for none external bottom brackets won't fit as they don't fit around the external bearings.

e.g. this won't fit: http://www.chainreactioncycles.com/Models.aspx?ModelID=5698

However it will fit with one of these.



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pugster007
post Jan 9 2009, 08:14 PM
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From: Chester



QUOTE(Doug @ Jan 9 2009, 06:42 PM) *
However it will fit with one of these.



LOL !

Thanks for the advice Doug & MP ..... worship.gif

Craig.
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Chris S
post Jan 11 2009, 07:46 PM
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From: Sutton Coldfield



not really hijacking this thread - thought I'd post here rather than start a similar one - anyhow

Went out today in very muddy conditions and got loads of chain suck

Cleaned the bike down and discovered its time for some new chainrings to start.

Currently running shimano LX hollowtech 22/32/42

Q1. Is there a better wearing brand than shimano - I've only done 1500 miles on these

Q2. Can i change the ratio to say 22/34/42 or 22/32/44


ta !!
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marcliam
post Jan 11 2009, 08:22 PM
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From: Dorking



I'm no expert but yes you can change the ratios and as far as I know providing you get replacement chainrings with the same bolt configuration i.e. 4 bolts and the same Bolt Circle Diameter (BCD) they should work. Suggest/suspect though if you are doing this you definately will need to replace all the chainrings.

I'm sure others will confirm the above and may be able to suggest alternatives (although I have tended to stick with Shimano)



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Jarl
post Jan 11 2009, 08:32 PM
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Shimano deore is steel, and will last longer, LX, XT, etc. is lighter "higher performance" (haha) aluminium. Generally speaking, the best way to go is steel inner (weight savings by switching materials here are negligible), hard coated alu. middle (middleburn do this IIRC) or ti if you're blinging it up, normal alu outer (weight is getting noticeably at this point, and alu is lighter than ti... also cheapest to replace, and doesn't get much wear due to the lower usage and lower torque being put through it)

Personally I was a fan of 22-36-48 (before I went single ring wink.gif), the only thing to watch out for is the reduced clearance and your mech might not handle the big jumps between the rings so well.


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pugster007
post Jan 13 2009, 09:07 PM
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From: Chester



Damm it !!

I need another new tool to remove the rings !!! I nearly rounded the bolt with 4mm allen key !! banghead.gif

Can someone confirm, do I need a T30 star ?

Thanks,

Craig.
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Jarl
post Jan 13 2009, 09:20 PM
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T30? They're standard allen keys AFAIK. However, it may well be. If you've got a multi tool with a torx bit on it for disc brakes, that'll be T25, so go from there.


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Mad Pierre
post Jan 14 2009, 08:20 AM
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From: Melton Mowbray



QUOTE(pugster007 @ Jan 13 2009, 11:07 PM) *
Damm it !!

I need another new tool to remove the rings !!! I nearly rounded the bolt with 4mm allen key !! banghead.gif

Can someone confirm, do I need a T30 star ?

Thanks,

Craig.


The reason you are rounding the bolts is they are a 5mm allen!!!!


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pugster007
post Jan 14 2009, 02:03 PM
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From: Chester



Solved ! The chainring bolts for M770 XT crankset are T30 !

I managed to borrow one from work, now I'm happy ! No more chainsuck ! (hopefully !) whistling.gif

Thanks to all for the responses. agree.gif

Craig.
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Suggsey
post Oct 9 2011, 04:08 PM
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From: Nuneaton



Craig my granny ring is shot too on identical chainset. Did you go for the steel deore or identical XT replacement out of interest? Mine has lasted about 2 years of year round muddy riding and lots of use. I had an old steel spare in the garage but that too is worn but not as much as the alu one but there is qite a big difference in weight and I notice on my old XT ring there are two shorter teeth to assist in up shift/downshift, or maybe they are just worn down think.gif as they do not look apparant on any for sale on the web.
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Chris S
post Oct 9 2011, 04:21 PM
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From: Sutton Coldfield



Suggsey

have a look at this

http://www.on-one.co.uk/i/q/CSSHM590DE/shi...-piece-chainset

its a bargain !

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pugster007
post Oct 9 2011, 05:50 PM
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From: Chester



Suggsey,

I replaced like with like, just to be sure ! I now use rosebikes for all Shimano items, very cheap even vs. Merlin +10% VIP discount.

http://www.rosebikes.co.uk/article/shimano...eeth/aid:249915

You need to order ~30 worth of stuff as postage is about a fiver, but at 6.90 (merlin 13.95) you can't go wrong, get a couple of chains and maybe a middle chainring to make the order worthwhile.

Craig.
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The Saint
post Oct 9 2011, 06:47 PM
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From: Robin Hoodshire



I thought one of the series M770 or M760, required a specific type of chain ring as other rings don't fit correctly, I know I've done it and have had issues with front derailuer changing, as the rings are slightly out of alignment.

I will need to check what I have...


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Suggsey
post Oct 9 2011, 07:20 PM
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From: Nuneaton



Yes the M770 needs the lower profile tabs where the bolt rings are as the rings for the other chainset model will not go over external BB's as they have longer tabs (you can dremmel off about 3mm to make them fit) so it is important if you dont want to be bodging to get the right tab size.
Cheers for the link Craig- like you say good value however I still have a stock of chains etc so may well just pop into LBS for one. I have a steel new one in the post for 6 but may go with a new alu one to start off with-unless the steel one arrives first so i can get out mid week if I aint working.
Spent last night deep in reading some in depth article in the issues and causes of chain suck that made me remove the ring to look at it closer as it looked fine on the bike but with brand new chain was truly awful and caused much walking recently.
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Gareth
post Oct 9 2011, 08:05 PM
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Joined: 28-July 04



Jarl has specced it right:

Steel Granny. This ring takes the most wear and steel lasts four times longer than Alu plus the ring is too small to make a big weight difference. On Deore/SLX the steel granny can be flipped over to double the life of the ring, lovely.

Ti or Steel/composite middle. It's a bigger ring so weight matters and it takes a lot of wear so plain steel is out. SLX shimano is great with a nylon reinforced steel ring, steel is too flexible if pared down without reinforcement. An alternative is a Hardcote Alu ring e.g. Middleburn but if you live in a sand/grit area like the Peaks good luck with that.

Alu Big ring. Rarely wears out, hardly ever sucks, giant size so go light.

Only SLX seems to actually have this magic combo out of the box so beware all others if wear is an issue for you.


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Suggsey
post Oct 16 2011, 06:33 PM
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From: Nuneaton



As it turns out, the LBS only had an alu XT replacement so that will have to do for the next twelve months and as soon as it starts to suck I will make extra efforts to get an SLX steel ring.
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