middleburn bottom bracket length question

Charlieboy28 · Mar 23, 2013

right my middleburns require a 113 axle, but i have spotted a nice un91 road bb with a 115mm axle thing.

would this work 2mm seems so teeny tiny, but then i also hear of people using 107mm with middleburns

any thoughts

Charlieboy28 · Mar 23, 2013

oh goodness im a feckwit, can a good mod please move this so that i can be enlightened please

Woz · Mar 23, 2013

I use 68/107mm. I think a 73/107 would be pushing it and the cups would hit the crank.

107 and 113 are symmetrical, but I don't know if the 115mm is. 110mm is asymmetric and therefore not suitable unless you use a 1.5mm spacer on the DS.

taffy · Mar 23, 2013

2 mm should not make a huge difference if your chain line is 47.5 -50 mm now pushing it to 51 mm should not create mega indexing or chainline disasters.

NeilM · Mar 23, 2013

RS3's use 107mm axles, I seem to recall that RS7's use a longer axle, 113mm is probably right.

I fancy you could get away with 115mm, as it's only a mm either side and Shimano chain line is usually around as 47.5 to 50 mm.

FluffyChicken · Mar 23, 2013

115 is all on the non-drive side compared to 113 iirc.
Its an old road (and suntour MD) spec

Charlieboy28 · Mar 23, 2013

Its this folks.

I do have a new un 55 in the correct length.

http://www.ebay.co.uk/itm/Shimano-UN91- ... 1c313c0002

So will it work.

Woz · Mar 23, 2013

The 115 will put the cranks off-center which you may not be fussed about....it will go round though

middleburn bottom bracket length question

Charlieboy28

Charlieboy28

Woz

Old School Grand Master

taffy

Old School Grand Master

NeilM

FluffyChicken

Charlieboy28

Woz

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