Shifters/Rear Mech Compatibility

[Brucey]

I'd say that it is almost guaranteed with that setup that you will run out of total capacity, and that you are probably best off setting it up so that you have slack running in small-small.

cheers

[Mick F]

Yep.
I tried shortening the chain a pair of links, and it wouldn't do big/big, not even close!
I have 118links on the chain. That's the 114links of the Campag standard - minus the joining link = 113 links. Then with three spare Campag links plus two KMC Missing Links = 118links.
I shortened the chain by using a single inner link between the two KMC MLs.
I've gone back to the way it was.

I'll measure up the Tiagra Medium with respect to the new XT mech later, but there must be a tad difference in them.

I popped out the seals of the lower jockey wheel as recommended, and indeed there was a paucity of grease in there, so I lathered it in more grease. The top pulley has a light oil in the plastic bushings, and I left it alone.

The XT mech fitted easily, and I played around with cable length, and inserted the in-line adjuster in a place that I thought was good. It doesn't matter much at present, I can always move it.

A quick and easy setup later, and I'm extremely impressed with the mech. Maybe I'm impressed due to the horrible Tiagra mech ......... or at least I consider it horrible. This new one is more akin to what I'm used to being a Campag man, but I love the way it operates. I love the way it's solidly mounted on the dropout too.

Sadly, I won't be out for a test ride today, and tomorrow is looking bad too. Saturday is a good bet. This comes with leading a busy life.

[Mick F]

I'll measure up the Tiagra Medium with respect to the new XT mech later, but there must be a tad difference in them.

More than a tad difference.

XT mech 79mm between the jockey centres.
4600 Tiagra has them at 87mm.

Both are described as Medium Cage, though I'm doubting that my Tiagra actually was. More like a Long Cage eh?
Not that it makes any difference as the actual metal cages are the same lengths. It's where the jockeys are positioned that is the mechanical thing I suppose, and how low the bottom one is off the ground.

I'm not about to re-fit the Tiagra to measure from the ground up absolutely, but I think they will be similar.

[Neilo]

My long cage XT is about 100mm between centres.

[Mick F]

Been out for a few hours, but before I went, I sorted out a new photo and compared it to an old one and then made composite screenshot. Plus, I measured the Campag Comp on Mercian. Comp is long cage and measures 89mm between centres.
There seems to be no set standard for these things.

Tiagra 4600 on the left, and Deore XT on the right.
Same gears selected, and the cages are as low as they'll go. XT is a little better, and one heck of a chain wrap too.

[Brucey]

.... I popped out the seals of the lower jockey wheel as recommended, and indeed there was a paucity of grease in there, so I lathered it in more grease. The top pulley has a light oil in the plastic bushings, and I left it alone.....

the top pulley has a ceramic-on-ceramic bushing. I find this bushing doesn't wear noticeably (over extended mileages) when lubed with finish line ptfe grease, and as I mentioned previously, the seal lips will only work if kept wetted with something a bit thinner; if they are allowed to run dry they pretty soon wear.

cheers

[Mick F]

.....the top pulley has a ceramic-on-ceramic bushing ...........

Wish I'd looked more closely.
The centre bit where the bolt went through was white, but I can't remember the colour of the outer bit in the pulley. I suspect that it wasn't white.

Therefore if they are ceramic/ceramic, they are different ceramics ............... perhaps?

Been busy all afternoon, and this evening too, but I'm free tomorrow morning for a time, so I may get round to taking out the top pulley.

[Brucey]

these are pulleys from a "Santé" rear mech, showing that shimano used ceramic for both upper and lower pulleys for a while. The bushing design is basically the same as the XT/ultegra guide pulleys, but the modern version (below) has seals added.




The grooves in the outer bushing are to provide a reservoir for lube/ a trap for any particles.

With white bushings, and white grease, it is very easy to see if there is any contamination or not. I have a feeling that wear debris from the shields is the primary source of contamination. IIRC shields are always stainless steel if fitted to a pulley with a ceramic bushing, but bad adjustment and/or many gear changes may create wear debris even if there is lots of grease present.

cheers

[Mick F]

Just taken out the top pulley to have a proper look.
Spot on, like this one.

Screen Shot 2017-11-10 at 06.43.02.png (123.41 KiB) Viewed 697 times

[Mick F]

Managed to get out for half an hour for a test ride.
Busy for the rest of today, and Sat and Sun are forecast to be rotten, so Monday will be a good ride day.

Absolutely gobsmacked at this XT rear mech.
It changes the rear sweetly and accurately and instantly. Totally perfect.

The jockey cage has a strong return spring, and it makes for a clunky front change and you can hear and feel the jockey cage taking up the slack when I go inwards. It's a bit "mechanical" going outwards, but it works well and gives much confidence.

This rear mech means business!

As an aside, I'm on record on here telling about the noisy SA 3sp I have with the 10sp cassette. I could swear that the back end is quieter now. Could it be that the Tiagra mech was loose and rattly and adding to the SA rattles?
I actually don't know, but I'll monitor it over the miles to come.

[english john]

Hi Mick
Can you tell me what you think about the barrel adjuster you used? Does it work ok in this position?

Cheers

John

[Mick F]

Hi John,
I did the whole job with the bike on the stand and it fitted easily though the outer cable ends need a good push to get them seated in properly. I had to cut out maybe an inch of outer cable to compensate for the adjuster's length.

I set up the adjuster to less than half way point and fitted the inner and clamped it up. I guessed it would need tightening rather than loosening, so less than the half-way was about right.

By turning the cranks in the middle ring, I set up the limit stops and adjusted the indexing by turning it using the rubber thumbwheel. It indexed well all the way from small to big on the cassette, then checked the outer few cogs on the outer ring, and then the inner few cogs on the inner ring. Basically, after a few minutes, it was fine.

Out on the road, it was a bit of a faff. I've always found that I can check all the indexing on a stand and get it perfect, but out in the real world, there's always a tweak required, and usually a few tweaks. It's easy if you have adjusters on a downtube, but I had to stop, get off, take an educated guess where the next adjustment should be, ride away and then suck it and see. After maybe three of four stops and adjustment, all was well.

We've been away in Spain for the past week, so not cycled. The weather is forecast to be ok mid-week this week, so I'll be out riding.

[deliquium]

I'll measure up the Tiagra Medium with respect to the new XT mech later, but there must be a tad difference in them.

More than a tad difference.

XT mech 79mm between the jockey centres.
4600 Tiagra has them at 87mm.

Both are described as Medium Cage, though I'm doubting that my Tiagra actually was. More like a Long Cage eh?
Not that it makes any difference as the actual metal cages are the same lengths. It's where the jockeys are positioned that is the mechanical thing I suppose, and how low the bottom one is off the ground.

I'm not about to re-fit the Tiagra to measure from the ground up absolutely, but I think they will be similar.

An info update on the annoying vague terms 'medium' and 'long cage' . . .

Just bought the rather nice SUN XCD 'long cage' rear mech in a sale

. . . its jockey wheels are @ 76mm centres

[Mick F]

Very nice!

Short, Medium, Long.
All relative terms I suppose.
Instead of distance between the centres as a figure - which doesn't state the diameters of the jockey wheels or where they are fitted - we should only consider Total Capacity.

Not what they state as TC, but what the actual figure that the cage can cope with.
I'm ruunning 61/48/34 with a 11-28 cassette on the Moulton. This gives (61 - 34) + (28 - 11) = 44
With Mercian and the Campag Comp rear mech, I'm 53/42/28 and 12-30 cassette. Giving (53 - 28) + (30 - 12) = 43

Yes, I had issues with Moulton at TC 44, but by shortening the chain by a couple of links, it's just about fine. Mercian is perfect at TC 43 and would be ok at TC 45 if I fitted a 26t inner ring.