94 or 110 BCD??

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Rabbit
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Joined: 19 Aug 2012, 10:43pm
Location: The New Forest

94 or 110 BCD??

Post by Rabbit »

Could someone explain to me please what difference there is between a 94 and a 110 BCD triple chainset, apart from the circle diameter? Do they both work in the same way and equally well for touring or is one preferable to the other? Thanks...
Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: 94 or 110 BCD??

Post by Brucey »

IIRC you can go down to 30T on 94mm but not on 110mm, obviously.

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Rabbit
Posts: 287
Joined: 19 Aug 2012, 10:43pm
Location: The New Forest

Re: 94 or 110 BCD??

Post by Rabbit »

You mean 30T on the chainset middle ring? Is that the only difference?
Brucey
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Re: 94 or 110 BCD??

Post by Brucey »

Rabbit wrote:You mean 30T on the chainset middle ring? Is that the only difference?


pretty much, yes, but remember that the inner ring fixings vary too, and so do the available chainrings, crank lengths, chainlines... did you have particular chainsets in mind?

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Rabbit
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Location: The New Forest

Re: 94 or 110 BCD??

Post by Rabbit »

I was looking at either a Sugino Alpina or XD2 triple, or the Spa version that they do which are all 110 BCD or a Middleburn R01 chainset which is 94 BCD. I couldn't work out if 94 was an odd size which might cause me problems. I wanted it to run on a 9 speed bike in a 48-36-24 configuration.
Brucey
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Re: 94 or 110 BCD??

Post by Brucey »

IIRC the middleburn crankset may well give you a lower Q value than the others. The rings are also harder wearing than most. But the Spa crankset is tops for value, no mistake about that.

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pwa
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Re: 94 or 110 BCD??

Post by pwa »

I imagine the Spa XD2 (nice chainset) will have a BCD of 110 for the outer and middle rings, and 94 for the inner ring. Spa are the obvious place to buy replacement rings in the future, and 110 / 94 are plentiful. The so-called Q factor of the XD2 (how far apart it puts your feet) is about 15mm less than a standard MTB triple chainset, so its okay. Spa also let you choose how much you spend on the actual rings, with the posh TA ones an option for durability.
Brucey
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Re: 94 or 110 BCD??

Post by Brucey »

XD2 is 110/74 BCD

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andrew_s
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Re: 94 or 110 BCD??

Post by andrew_s »

If you want 48/36/24, go for a 110/74 bcd triple like the Sugino/Stronglight/Spa XD2 or TD2/new Impact, which will be a lot better value, and chainrings are much more readily available too. Note that the X2/old Impact has one of the bolts behind the crank arm, where a non-standard bolt is needed.I'd go TD2.

It's only worth doing something different if you think that 24T isn't a low enough gear, in which case the next option is a Middleburn R01 5-arm triple, with 94/58 bolt circles allowing down to 20T. It will probably be special order, to get the non-stanvard spider

For chainrings, Spa's own brand are best value.
bgnukem
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Re: 94 or 110 BCD??

Post by bgnukem »

110/74mm is the old PCD standard for non-compact MTB chainsets. Used to be sold with 46-48T outer 'rings, 34-36T middle and typically 26-28T inner.

94/58mm is the compact drive MTB standard, prior to the 4-bolt chainsets being introduced. They used to be sold with 42-44T outer 'ring, 32-34T middle and 20-24T inner.

The main difference will be whether or not you want to run smaller 'rings. I think the larger PCD will allow down to something like a 34T middle 'ring and a 24T inner, whereas the smaller PCD will permit a 32T middle and 20T inner.

Obviously, if you choose to use large rings (46-48T) on the smaller PCD there may be a little more flex in the 'rings as they are not quite as well supported by the spider.

I would guess the chainline won't be radically different, assuming both chainsets were originally specced for mountain bikes.

Be aware that the Spa / Sugino XD2 may not work briliantly with 9/10-speed chains. I find a 9-speed chain tends to fall into the gap between the middle and outer 'rings on my Spa triple. I guess the original Sugino pattern was designed back in the days of 7/8-speed MTB transmissions.
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