Does anybody know of options for chainrings for Ultegra 6700.

I'm not in front of the bike today but from memory, the big chainring has the female threads. replacements only seem to come in 50t .
Does anybody know the best way to fit more off road friendly sizing? (do you need spacers for the holes etc)

Alternatively, can you fit mtb chainsets to BB86 frames?
I'm struggling to find an adapter.

FLV wrote:Does anybody know of options for chainrings for Ultegra 6700.

I'm not in front of the bike today but from memory, the big chainring has the female threads. replacements only seem to come in 50t .

I might be talking out of my 4rse here, but I thought the shimano rings, the one on the outside might be a fancy one with female threads rather than the more normal hole through it and chainring bolts, but it's still a standard bcd (compact or not, so 110 and 130 I guess) and hence normal rings will fit. It's the newer 4 bolt shimano road cranks that went all weird standards I thought...
So std rings should do it, just won't look as pretty.

FLV wrote:Does anybody know of options for chainrings for Ultegra 6700.
Alternatively, can you fit mtb chainsets to BB86 frames?

BB86/BB92 is your standard shimo-esque 24mm crank axle affair innit? so a MTB chainset should fit (check your 73mm spacing or whatever it is you need), i often by the "road" BB cups rather than the "MTB" cups coz of price and they're identical.

I haven't checked my facts here, it's just what I thought/inkling towards. HTH and maybe gives you the starter for ten.

I expct you are right on the BCD of 110mm for the compact. I wondered if the holes were bigger or anything for special bolts, or the face might not be flat or something.


For the BB86, I thought that you ended up with an overall lower width, so the mtb cranks would end up with 'float' of about 5.5mm, I got this from checking hopes BB and crank compatibility charts. I thought road press fit ended up 91mm and mtb ended up 96.5mm.

For screw in ones, it all works as long as you dont fit the spacer tube?

FLV wrote: For the BB86, I thought that you ended up with an overall lower width, so the mtb cranks would end up with 'float' of about 5.5mm, I got this from checking hopes BB and crank compatibility charts. I thought road press fit ended up 91mm and mtb ended up 96.5mm.

For screw in ones, it all works as long as you dont fit the spacer tube?

Zippy wrote:

FLV wrote:Does anybody know of options for chainrings for Ultegra 6700.
Alternatively, can you fit mtb chainsets to BB86 frames?

BB86/BB92 is your standard shimo-esque 24mm crank axle affair innit? so a MTB chainset should fit (check your 73mm spacing or whatever it is you need), i often by the "road" BB cups rather than the "MTB" cups coz of price and they're identical.

Yeah, you might/will probably have a bit of spacing difference, but nothing a bit of careful measuring and some spacers won't sort out IIRC (call it 'calibration 'and it's suddenly fine )

BB86 is just the press fit standard iirc. You will need a to space out for a MTB chain set, but it'll work quite happily.
As far as I'm aware the smallest compact chainring you can get is a 33t but they're stupid expensive. Cheapest option is if your running the 10speed option is a 9speed MTB long cage rear mech with a 34 or 36t 10speed cassette

BCD is definitely standard 110. So any aftermarket rings/bolts should be fine.

http://si.shimano.com/php/download.php? ... -2956A.pdf

As mentioned you're only going to get down to a 33 on the inner (Specialities TA do one).

The frame shell width for (Road) BB86 is 86.5mm, essentially it mimics the total width of a HTII bb to work with standard Shimano 24mm axle cranks.

The MTB press fit BB shells are 91.5 (so known as BB92) again to correspond to the width of an MTB width HTII BB.

So it's possible you could use something like this
http://www.silverfish-uk.com/ProductDet ... pe-Adapter

with some form appropriate spacer each side for MTB cranks (You've got to find/make a spacer of right diameter!)

However I've no idea how these things fit together, do the left and right parts screw together?
What stops the whole unit rotating inside the frame?

ctznsmith wrote: However I've no idea how these things fit together, do the left and right parts screw together?
What stops the whole unit rotating inside the frame?

Press fit, so friction.
They do sell spacers for press fit, in fact I have the race face ones and they came with one iirc. Also made one using some copper wire once.

Zippy wrote:

ctznsmith wrote: However I've no idea how these things fit together, do the left and right parts screw together?
What stops the whole unit rotating inside the frame?

Press fit, so friction.
They do sell spacers for press fit, in fact I have the race face ones and they came with one iirc. Also made one using some copper wire once.

Well for the OP, it appears that yes he could fit an MTB crankset.