Campagnolo SR rear derailleur fixing bolt

neeb

Can someone just confirm that the fixing bolt for the current SR rear derailleur is a torx T25 on both sides? (*edit - it's actually T30 on the inside, see below*)

The thing is an absolute nightmare because the bolt is recessed a long way on the outer side, such that even some long reach wrenches/bits can't reach it because the straight part of the wrench is slightly too wide to fit in the hole... Many wrenches and bits, although they are long, have the body of the wrench slightly wider than the actual torx-cut end, and Campagnolo have conveniently made the recessed hole for the bolt extremely narrow...

On the back side (from the hub) it is definitely a T25 (*edit - sorry, it's a T30*), and although the campag manual says it is T25 from the other side too, I am not 100% sure this is the case. I can fit a long T20 in there and it sort of bites but seems too loose, while a long T25 won't go in, but I'm not sure if this is because the bolt is not T25 or if the stupid recessed hole is stopping the bit reaching the bolt socket...

edten

I had a similar issue. I cant remember what I used in the end but as you dont need to remove the mech much just undo it from the rear side. You'll have to take the wheel out of course.

neeb

edten wrote:

I had a similar issue. I cant remember what I used in the end but as you dont need to remove the mech much just undo it from the rear side. You'll have to take the wheel out of course.

I've used the rear side before but I've had problems with the bolt sticking - for some reason this seems to happen more easily if you tighten it from that side, or at least that's the impression I get. Last time it required so much force to undo that it slightly bent the dérailleur hanger... I'm getting a new hanger (for other reasons), so I want to try to do it right this time. I might actually try buying a proper Park Tool T25 wrench, if that doesn't fit I'll sue Campagnolo for the cost of buying it, their manual definitely says to use a T25 and from the dérailleur side...

I think it might be down to the shaft of the wrench having to be no wider than the flanges on the torx part. Many cheaper ones flare out slightly from the torx bit to the rest of the shaft.

proto

I'm at work at the mo, so can't check, but I thought the rear mech (Super Record) mounting bolt was Torx T27. Or is that the brake block mounts?

You mention 'both sides' when undoing the bolt. I don't think it is designed to be undone from the outside of the mech, but the inside/wheelside only. FWIW I always put some copper grease on the thread/bolt.

neeb

proto wrote:

I'm at work at the mo, so can't check, but I thought the rear mech (Super Record) mounting bolt was Torx T27. Or is that the brake block mounts?

You mention 'both sides' when undoing the bolt. I don't think it is designed to be undone from the outside of the mech, but the inside/wheelside only. FWIW I always put some copper grease on the thread/bolt.

The diagram in the Campagnolo installation instructions shows it being tightened from the outside. Pretty sure it's T25 on the inside. (*edit - actually it's a T30*)

proto

Just checked, and unless you have a very special Torx driver then it cannot be tightened/loosened from the outside.

Secondly, I use a Torx T27, which is a better fit than a T25 (although I suspect that the latter would work okay).

neeb

proto wrote:

Just checked, and unless you have a very special Torx driver then it cannot be tightened/loosened from the outside.

Secondly, I use a Torx T27, which is a better fit than a T25 (although I suspect that the latter would work okay).

Thanks for checking! Actually though, I just checked mine again and as far as I can tell it's a T30 from the inside / wheel side. I must have been remembering incorrectly when I said T25 above (I'll edit the post to avoid confusion). With torx the next size down will often work without slipping (such as T27), although I guess it's not very good for the bolt.

I still think that it must be possible to tighten it from the outside, as I can actually get a grip with a T20, although it's not very tight and I don't want to use it. It's not going all of the way through to the T30 socket on the wheel side, so there's definitely a narrower socket accessible from the outside, which I'm guessing must be a T25, except requiring a very slim tool.

I have the Park Tool T25 on order, when it arrives I'll tell you if it works or not...

proto

Hmmm, I only said T27 as that's what I packed when I took my bike to Spain, so assumed that was the correct size, but have to admit it's a bit sloppy, so T30 might well be the correct size. I'll check again tonight and report back. Again. :oops:

proto

Yep, T30 is the correct size. No idea why I thought T27 was correct, but T30 is the right tool, and only from the inside.

neeb

proto wrote:

Yep, T30 is the correct size. No idea why I thought T27 was correct, but T30 is the right tool, and only from the inside.

Thanks!

I still have a suspicion that the right T25 (not widened at all in the shaft) may work from the outside. Waiting from my Park Tool PHT25 to arrive, I'll keep you posted...

neeb

I was right! 8)

Got the Park Tool PHT25, and it works, from the front!

So it's T25 from the front and T30 from the back. The problem is that most torx wrenches are wider than their "business ends" once you get past the business end. You don't get this problem with allen wrenches because the shaft is usually just a continuation of the business end. Here's a picture that illustrates this - on the left is a standard torx T25 from torx wrench set I have, on the right is the Park Tool one. Because most wrenches flare out after the business end, they don't fit in the narrow recessed hole for the derailleur bolt...

rjgr

neeb wrote:

I was right! 8)

Got the Park Tool PHT25, and it works, from the front!

So it's T25 from the front and T30 from the back. The problem is that most torx wrenches are wider than their "business ends" once you get past the business end. You don't get this problem with allen wrenches because the shaft is usually just a continuation of the business end. Here's a picture that illustrates this - on the left is a standard torx T25 from torx wrench set I have, on the right is the Park Tool one. Because most wrenches flare out after the business end, they don't fit in the narrow recessed hole for the derailleur bolt...

As usual you get great advice from this forum which is a reference whenever you are stumbling around, torn between the costs of a bike shop (never open when you need them most) and the worry of damaging your pride and joy, because you are too stupid to know that some threads on bicycles are reverse threaded for very good reasons!!

So for those as inept as me I can confirm it's definitely T25 from the front. Running two Campagnolo equipped bikes I often rely on the T25 on my Topeak mini 20 tool that goes everywhere with me and the T25 bit on that is long/slim enough to do the job.

If you are working from the back (wheel) side it is a T30 but don't forget it is a reverse thread from that side!