New rear wheel why do I need to re-index?

[bad boy]

Hello all,

Hope everyone Is well, not posted for a while.

I got some open pros built up on some 105 hubs for the commuter and for some reason found myself having to tweak the tension slightly to sort out the shifts going down the cassette.

I've also checked as a result the stop screws but I can't understand why I've had to do this, just thought all I needed to do was swap the cassette over and job done.

I did initially think it was the dishing but this would be in relation to the entire wheel being centered between the rear drop outs. Only thing I can thnk of is the hub must be slightly longer therefore pushing the cassette out ever so slightly ??.

My old wheels had standard spesh own branded hubs.

Just wanted to eliminate the possibility I've done something wrong !

 

[Norm]

I'd be very surprised if having to tweak the tension slightly meant anything at all. The indexing can need a tweak just from removing and replacing the wheel, if you don't take a bit of care to make sure that it's exactly in line and where it was previously, or it can just need a tweak because it's been a while since you last tweaked it.

Cables change length, muck gets into the outers, having seen how little you are actually moving the derailleurs when you do a tweak, I'm surprised that they don't need doing more often.

 

[Red Light]

The distance between sprockets on a ten speed cassette is 4mm so it only needs a small difference in the thickness of the axle nuts or washers to shift the wheel over slightly and need re-adjustment of the derailleur. Its small enough that you probably won't notice it on the limit screws but enough to notice it on the gear changing.

 

[accountantpete]

You didn't transfer a spacer (between the hub and large cassette ring) did you?

 

[bad boy]

Hi all,

Thanks for the replies.

Yes I did move the very think spacer over when installing the cassette thought I had to as its a ten speed cassette

 

[Sittingduck]

You sure it isn't just cable stretch? Have you tweaked the barrel adjuster on the rear mech to try?

 

[bad boy]

It was spot on before the wheel change. After I had to loosen the tension a small amount to get the down shifts sweet as they were sluggish. The indexing is spot on now with the new wheel in but just wondering what caused it.

 

[Sittingduck]

Perhaps the new wheel isn't dished right? Just thinking out loud here... not sure if that would make the diff but could do. Either that or the wheel isn't sat in the dropouts just right.

 

[bad boy]

Good point I thought that too but wouldn't that determine rim position central to the dropouts as opposed to the cassette position on the hub ? .

I think account pete and red lIght are on to something, maybe I need to remove the small spacer perhaps

 

[boydj]

Think it's just a very small difference in the way the hub is built. It's not unusual when swapping between different makes of wheel to have to re-tune the indexing - I have half a turn on the adjuster swapping between commuter wheels and the 'week-end' wheels. No big deal.