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PostPosted: Sun Nov 18, 2012 9:05 pm 
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Excuse if I'm teaching Grandma to suck eggs


Thanks for your advice, greatly appreciated...

I tried this, I tried slightly different angles to see if my "in line" wasn't in line, tried raising and lowering (although I had it about 1-2mm clear not 3 or 4)

I could not get it to shift up, then when it did shift up it would shoot the chain off the outside of big ring, if i set the limit screw to stop the overshoot it wouldn't shift to the big ring then just when I got this just sorted, it wouldn't shift down..... I'll have to try it again..... I may have just been having an off day.

The only other thing that occurs to me is .... is the "throw" of the high band mech different to the "throw" of the low band type? I'm assuming all shimano is the same at this period???

As I said I managed to get a mech that shouldn't work to work in about 20 mins..... :roll:


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 Post subject: Mechs
PostPosted: Sun Nov 18, 2012 10:28 pm 
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I think there is a bit of "experience" required, I.e. a Knack that comes after setting a few up. Some mech's seem easier than others, even the same make and model vary. What front rings are using tooth wise?


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PostPosted: Sun Nov 18, 2012 10:36 pm 
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it has been a few years I must say :oops:

Middleburn standard in 24, 34 & 46t, I was wondering about getting some slickshift ones.

Just tried again and the weird thing is when the chain goes up to the big ring it seems to sit on top of the teeth before "dropping in", now that is confusing me as to why?


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 Post subject: Shifting
PostPosted: Sun Nov 18, 2012 10:46 pm 
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I think it's the 46t big ring that is giving you the problem, Only early Mtb's had that set up and so needs a very early mech. The inner plates on these were less profiled and pretty flat, later ones had steps pressed into them to suit 42-32-22 etc what happens is the pressed out profile, doesn't "mesh" with the middle ring and it won't shift-won't shift-won't shift, then a bit more pressure and it goes over the big ring and the chain slips. The ratios are too wide for that style mech, DX and M730/2 are the type that would work the best.
Slickshift would improve things a lot though.
Also lifting the mech a couple of mm or so would help, as the chain needs a bit more room to move than that.


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PostPosted: Mon Nov 19, 2012 12:27 am 
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If I went 26, 36, 46t would work better?


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PostPosted: Wed Nov 21, 2012 7:15 pm 
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matt24777 wrote:
If I went 26, 36, 46t would work better?


Would do, but 42/32/22 would be the ideal as the profile of the cage is too small for a 46 ring really.


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PostPosted: Thu Nov 22, 2012 9:54 pm 
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Right having done a little research I have concluded I can't get middleburn slickshift rings in 42/32/22 to fit an ATB spider.

Further I have ordered up a set of 46/36/26 slickshift rings to fit my RS3 ATB spider. I have also ordered another XTR M901 mech from the states as I have my doubts about the one I do have.

In theory I believe that XTR had 46/36/26 rings and that mech so they should work ok together.

If this doesn't work were back to square 1 :cry:


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 Post subject:
PostPosted: Mon Nov 26, 2012 8:59 pm 
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went for a ride sunday, (still waiting for the new mech from the states) and all seemed fine except....

the chain would keep jumping off / overshooting the inside of the granny ring. :shock:

so I measured the ring spacing as best I could and it looks to me like the Granny sits closer to the middle ring than the middle ring sits to the big ring :?:

so i packed it out with some 1mm washers and it seems fine now.

I'm a bit bemused by this latest glitch as they are middleburn rings on a middleburn spider. Big to middle seems fine in both directions but small to middle is a bit hesitant going up, and overshoots going down (without washers).

I've had to set the lower limit quite wide or it just wont shift to the granny ring at all, (I'm wondering if the mech cage is slightly bent, hence the new mech) but watching the chain come off the middle ring it would always miss the teeth of the granny ring as it can't bend that tight. (Its IG70).

Any suggestions/what am I missing? :?


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 Post subject: Middleburn
PostPosted: Fri Nov 30, 2012 8:32 pm 
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Are the cranks the version with granny spacers or not? Also Middleburn seem to do differing thicknesses of rings and some have the teeth more centred than others, maybe it's a mismatched set? You could also still be using too wide a bottom bracket for the chainset?


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 Post subject:
PostPosted: Fri Nov 30, 2012 9:04 pm 
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Quote:
re the cranks the version with granny spacers or not?


The ATB spider is flush on the granny ring side. Would it have come with spacers originally?

Quote:
Also Middleburn seem to do differing thicknesses of rings and some have the teeth more centred than others, maybe it's a mismatched set?


possibly but they were purchased as a set, so unlikely but not impossible.

Quote:
You could also still be using too wide a bottom bracket for the chainset?


The chain line to the middle ring is measuring up at 51mm which is indeed a little wide, I maybe should try a 109mm BB

Thanks for the advise :)


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