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This weekend I tried to fit a set of middleburn cranks to my bike. I got the cranks 2nd hand and they came with a 5 bolt spider. I bought a new 4 bolt spider from CRC to fit my existing chain rings.
The problem I have is that the outer ring goes on fine but the middle ring wont fit on.
The middle ring mount is a larger diameter than the outer (88mm outer, 90mm middle, both 104mm pcd) so no rings will fit on it although outer and middle rings both fit on the outer ring mount.
Do middleburn have some strange standard I'm not aware of or I am just being stupid??
Help please!!
Did CRC send you an XTR spider by mistake or something?
Did CRC send you an XTR spider by mistake or something?
Excuse my ignorance but how would I know?
The Middleburn 4 bolt spider I have at home has the middle ring using the same chainring bolts as the outer ring.
Just had a look on Middle burn, they cant have sent me an XTR as it has a different engagement pattern and wouldnt have fitted on my middle burn cranks.
4 bolt xc
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XTR
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Any other ideas?
Are they Shimano rings? I had the same problem with shimano rings on both a middleburn and a truvative noir spider, XT and Deore 36T rings, so I'm beggining to suspect that it is the shimano middle rings that are the non standard size. I ground a small amount off the tabs on the rings to make them fit - a bit of a bodge but it worked.
The Middleburn 4 bolt spider I have at home has the middle ring using the same chainring bolts as the outer ring.
Thats the same on my spider, they share the same bolts but the ring wont fit over the shoulder so cant be seated.
Are they Shimano rings?
I tried middleburn, fsa and truvativ rings, all with the same result.
Here's a quick shonky drawing of the problem in profile. Imagine a section through one of the arms of the spider.
Rings will sit fine on the 88mm shoulder but not on the middle ring 90mm shoulder
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Mines the same, thought they are supposed to be like that.
Mines the same, thought they are supposed to be like that.
What rings are you using on them?
Deore 36T middle ring with a blackspire bashguard outer, like I said I had to gind a small amount off the tabs. I did a search on the internet at the time and there are several threads about differences between shimano rings with nominally the same BCD, thats why I assumed it was the ring rather than the spider, especially as I had the exact same problem with a shimano XT/Saint 36T ring on a truvative spider. Sorry I can't be of more help, but from what you've described I would say the spider is correct.
What rings have you tried?
Cheers Seamus, I'll get the file out when I get home for now and see if I can find out anymore in the future for a non ramped ring.
It seems Middleburn are supplying spiders that only fit the older Pre-Hollowtech-II middle rings with the thinner metal at the inside edge of the bolt holes.
You are OK filing down the newer HT-II aluminium or steel rings to fit, but I would not attempt to fit a composite XTR/XT/SLX middle ring.
You can see Middleburn offer a 32T HT-II ring as a separate item in their website.
http://www.middleburn.co.uk/chainrings_mtb.php
PaulD
PaulD,
I'm a little confused here. So should I be able to buy a chainring which will fit straight off without filing down and if so, what should I be looking for?
Cheers
Nick
Nick,
A new 'regular' 4-bolt Compact Drive Middleburn middle ring will fit straight on.
Any HT-II ring (from Shimano or others) will need filing down to fit.
I have a few Middleburn hardcoat slickshift rings and am very impressed with their life and lack of chainsuck. I cannot say the same about some other middle rings.
Hope this helps.
PaulD
Cheers PaulD,
I'm running this as a 1x9 setup so I'll get hold of a middleburn hardcoat, none slick shift.
It does seem an odd setup though, I wonder why they haven't changed it, there's loads of meat left so it can't be a strength issue.
I do not know for sure, but I think Shimano paved the way for their composite rings, which require more meat around that part of the fitting.
Anyway, you seem to have things nicely under control.
You could either buy their 4-arm solid DH ring or a 4-arm 'regular mtb' middle ring, just not slickshift as you identified.
http://www.middleburn.co.uk/chainrings_solid.php
http://www.middleburn.co.uk/chainrings_mtb.php
Good luck.
PaulD.
I got a reply from Middleburn, new rings are the answer!
To Nick
The normal ID for a 4-ARM middle is 90mm. This is all older Shimano, Race face ect
Shimano changed the ID on there middle to 88mm a couple of years ago.
If you are fitting one of our middle rings you would need a CR7932
Hope this helps
From Matthew
i'm going to try and fit a middle burn cr7940 104spd as a middle ring and a cr9026 as a small ring on a m970 xtr crank set.
it currently has chinnock 40teeth and 26teeth rings on, so i'm trying to keep the same setup, but using middle burn instead.
will this work? or should i get middle burn specific m970 rings? if so they dont do a middle with 40 teeth?.
am i better going back to TA chinnock?
I've filed down a composite Shimano middle ring for this is fine. Funnily enough once you have filed through the composite an hit the steel it's the right size!
no-one got any ideas then?