Rotor Aldhu24 spacers?

[cvbm]

I'm swapping cranks for a set of Aldhus with the 24mm spindle.

Kind of confused by rotor instructions vs reading across various online forums and hoping someone here has insights.

I have a (mtb / older style) HTii bottom bracket on a 68mm BSA bb shell. Specifying mtb style since I think recent road HTii bbs are a bit wider?

Anyways it seems like the DS cranks/chainrings are perilously close to my chainstay while the NDS is miles away such that the preload collar can't take up the slack.

I assume that this is an instance where Rotors instructions should be followed and I need a 1mm spacer on each side of the spindle? Confused as I've read elsewhere that the aldhu can be a straight swap for shimano road cranks, but now I'm thinking that must be for the road style BBS, and the mtb style BBS do indeed the spacers.

As an aside, are the o-rings rotor says to use necessary? Their own instructions seem to handwave them away

[skouri1]

Straight replacement as in it's designed to fit a hollow tech bottom bracket. Axial spacers may be needed however, just as you will have to adjust the preload with the rotor collar. If you search the forum you'll find a thread where people advised me on how to fit it to an external t47 my Shimano was in. From recollection I needed 1mm on each side in addition to the o rings.

[cvbm]

Thanks! Yeah 1mm on each side is what the instructions do say. How critical are the rotor specific spacers on the axle? Could I get away with non-rotor spacers? Think I have some steel 1mm spacers for 24mm axles laying around... maybe 1mm on the BB cups between the bb shell and cup would be preferable to move the bearings slightly wider and eliminate the need for spacers on the axle at all?

Idk maybe I'm splitting hairs here and I should just chuck it all on and call it a day

[mmendoza87]

After installing Aldhu cranks on several frames, I learned not to rely on Rotor's specific spacer instructions and to just install spacers based on feel. First I find a center point of the frame, either under the BB shell or downtube, then put spacers on either side of the BB to "center" the crankarms. In other words I measure to the sides of the crankarms from the centerpoint of the frame and make sure they are even. My frames are round tubed so it makes finding the center of the frame quite easy. Use the preload adjuster take up any slack. I do use the o-ring. Make sure it's not too tight so the bearings spin freely. Never had any problems.

Another reason to avoid the suggested spacers is because not all frames have perfect BB shells. For example, one of my frame's bb width was closer to 67mm not 68.

[skouri1]

agree with above. a 1mmx24mm axle spacer has nothing special to it. The o ring is a specific diameter but will squish. I actually sourced all from powermetercity . they threw in the axle spacers i needed (and some extras) when I ordered the O ring. Excellent service.

[.RJ]

Originally Posted by cvbm

How critical are the rotor specific spacers on the axle? Could I get away with non-rotor spacers? Think I have some steel 1mm spacers for 24mm axles laying around... maybe 1mm on the BB cups between the bb shell and cup would be preferable to move the bearings slightly wider and eliminate the need for spacers on the axle at all?

Spacers are spacers. I have a whole little bin full of them that come in handy when building stuff up from spare parts and I'll do whatever makes sense (crank spindle or bb cup).