[Closed] XTR M980/M985 Q-Factor?

I would if I was in the office today. I should be back in tomorrow and will check if you haven't already found out. Bump this thread back up to the top in the morning to remind me.

cheers

Ah bugger, the Shimano spec book only gives centre of BB to inside of pedal arm, not the outside of it. An FC-M980 chainset is 69.0mm where as an FC-M985 chainset is 66.0mm An older FC-M970 chainset is also 69.0mm.

I hope this is of some help at least?

I would offer to measure my M985s later, but frankly it'd be virtually impossible to do with any degree of accuracy whilst on the bike.

However... is it not just double Mister Ps measurement, plus the width of the crank? Ie 138 for M980s and 132 for M960s plus about 20mm for the cranks?

[i]However... is it not just double Mister Ps measurement, plus the width of the crank?[/i]

It is double the measurement plus two crank widths. That measurement is not in the Shimano frame builders book unfortunately and I don't have a crank and calipers to hand to measure one.

thanks guys

had a look at the frame builder details for the M970 which i know the q-factor of (170mm)

69.0mm
69.0mm

center of bb frame to inside

so the M980 is 170mm same as the M970 and the M985 should be 164mm if 3mm narrower each side

ordered the 2x10 M985 cheers

I must say I didn't really think anyone cared that much 🙂

M985 will not fit some frames thats all, was trying to work out if they would before shelling out 300 quid

i like the 88mm bcd

I must say I didn't really think anyone cared that much

Nail on head

i care if i spend 300 notes on some cranks that dont fit my bike 🙄

Lol good point mate!!

Actually, I care a bit. But only because most kit is too narrow. I always end up with the shoes setting as far out as possible.

i care if i spend 300 notes on some cranks that dont fit my bike

Since when has a crank set not fit a bike due to the Q factor!?!?!

errr all the time,

try fitting XX 156mm qfactor cranks on a modern full sus,

Modern parts not fitting modern frames shocker, whatever next 😕

m985 doesnt fit the orange 5 for starters, but the m980 fits, but not in the 38/26 guise

I can measure my xtr's Monday when I can borrow a large vernier from work
If that's any help!?

i like the 88mm bcd

That's just weird. How can you like a BCD? Particularly when it's totally unique and precludes you from buying any other off the shelf rings?

That's just weird. How can you like a BCD?

what he said.

Particularly when it's totally unique and precludes you from buying any other off the shelf rings?

3rd parties make rings already, there was another thread about it yesterday. Now if only MRP would release their chainstay-mount X-1. Maybe I'll just have to 'borrow' Kabush's next week.

88mm bcd allows you to run a single 28t (not seen anything lower) to 42t chainrings on the same point on the spider, while keeping a good chainline,

sram now use 80/120mm bcd, you cannot run anything small on the 120mm bcd

and on the 3x triples 64/104mm bcd on the 104mm bcd you cannot use less than 32 on the 104mm bcd middle (you can sometimes run 31t if you file your crank arms)

so if i want to run 1x10 i can do 32/36, but that means im off and pushing on some hills (MTFU?) so i can run 30/36 or 28/34 which are just right

😀

Have you ever been accused over analysing things?

looks rational to me 😆

You can run at Extralite 30t Octaramp on 104, as you say you have to file your spider.

IMO a 28t single ring is rather undergeared! Ymmv of course!

28/34
are you climbing the north face of the Eiger?

Anyone know if it's possible to shim the race crank 29/42 out to 165mm q is the no drive side arm on a pinch bolt?

Titus x racer info suggests crank with q factor over 165mm. I don't want to use xx

It's either that or the triple, although the triple is not a huge problem, 40 grams or so

Each to their own and that but do folk seriosuly believe 6mm of Q factor makes any difference?

Surely it's a case of wanting the double cranks, and getting the reduced q-factor at the same time, rather than specifically wanting a lower q-factor.

Cav uses custom Dura Ace pedals to add 20mm to his q-factor, so narrower isn't always better.

I always shim my pedals out, I low Q factor is no good for me.

Single 28t ring? what do you do when it's flat or downhill?

Ah Ok I just saw teh OP which was purely about Q-factor.

I doubt it makes any difference, having ridden a 100mmvbb bike!

For me im happy with a double at 42/29 even on 9 spd with a 34 rear sprocket, the bike is light.

But the q factor of the double could be too low to clear the chain stays, if I got the triple that's ok, the trail double has 26/38 rings which may actually be a bit low at the top end for what I want and so I'd have to change rings...it's already expensive enough!!!

So I don't care about the q other than it fitting the bike.

So if Cav and Blazin-saddles both increase their q-factor it's clearly the way to go fast, low q-factor is rubbish! 🙂

But the q factor of the double could be too low to clear the chain stays, if I got the triple that's ok, the trail double has 26/38 rings which may actually be a bit low at the top end for what I want and so I'd have to change rings

What do you want? You may surprise yourself with what you can get away with, unless you're really putting in loads of road miles and wanting to pedal down fireroads. I've gone single 36t ring and love it. Tend to be near the top for the c8 miles on the road to the trails, but don't spin out. Off road it's fine.