SRAM Rival issues on a Giant TCR A0

Iain C

Ok so I'm back into road biking after a very long gap. My main road bike is a Giant TCR A0 which is standard out of the box, and has never been apart (save for some carbon headset spacers) However I have quite a noisy drivetrain and I need to understand what I should be expecting noise wise.

My old bike (CB Dalesman, rode in my teens and recently rebuilt, see sig) has indexed rear (7sp) and non index front. The drivetrain is always very quiet, and if I do get any front chain rub on the derailleur a slight tweak of the lever will shut it up. Obviously I never run big to big or small to small on any bike.

However on the Giant, whilst the rear gears (10 sp) work faultlessly, the front of the bike really is quite noisy, and it does suffer from chain rub. So as soon as I above 6th or so, I'll go onto the big ring and go a few down a few gears at the back to compensate. I will have a look at the SRAM website and Park tools again and have a proper go at it in the workstand at the weekend, but what is the best I should be expecting? Apart from big to big and small to small, should I expect a rub free drivetrain? Because with index front gears on the doubletap system theres no way to dial it out is there? It's obviously some kind of concern as I read that the new electronic Shimano system moves the mech across a bit to try and help with it?

The other thing that I find a bit odd is that if I'm on the small chainring and the last couple of small sprockets on the back, and make sure that there is no front derailleur rub whatsoever, I do get a noise as the outboard side of the chain rubs ever so slightly against the inside of the big ring. This is presumably nothing at all to do with the front mech...it would still happen even if the mech was removed. Seems more to do with chainline?

Appreciate some help or experiences of other TCR owners on the best I can expect with some serious tuning. I know I need to tune it, I just need to know what I can expect and when to say "that's it".

Thanks in advance...

John.T

The chain rub on the small/small will happen on most bikes regardless of group used especialy if using 50/34 rings. Both Shimano and Campag and I believe the dearer Sram systems do have a trim for the front mech. You may find fine tuning the front mech will help.

Iain C

John

I'll always avoid small to small...my bigger concern is why it's rubbing the inside face of teh outer chainring itself rather than the mech. Any thoughts? Chainset is not a compact by the way.

John.T

It is a chain line thing but there is not much you can do about it. I have 3 bikes and they all do it to some extent but only on small / small. They are ok on the next cog. I have fitted a spacer behind the BB cup on one bike. The one for fixed cogs fits nicely. Could be worth a try.

Iain C

Thanks...can you post a linky to the part you mean? It's an external BB job...

I was almost thinking about putting shims behind the big chainring...

John.T

I do not have a link but any good bike shop should have them. They fit any screw on rear hub and go on before the cog or freewheel. I am also using an external BB. I would not use more than 1 washer.

Iain C

OK great, will give it a go, thanks.

croggy

I seem to remember years ago chainrub didn't exist.I had chainsets with a 6mm gap between chainrings.Nowadays it's about 4.5mmm.

John.T

Chains were a lot wider though. In the 1960s I was using 52/43 and that was wide at that time. Tourers were using wider ranges but they were so far apart that the chain would fall between them if you missed a change.

MabBee

By coincidence. I've posted a similar question about a shimano chainset: I have swapped the chainrings over to TA and I now get the chain rubbing on teh inside of the large chainring when I'm on the smallest 3 or 4 sprockets.

John T -- you made the same recommendation to me, and I plan to give it a go. Just to be sure I've understood this correctly: I need to remove the drive side BB cup, place the spacer against the frame and re-install the BB cup. Have I got that right? Only I am a bit worried that (a) the axle won't line up properly with the inside of the bearings and (b) the non-drive crank will have a reduced contact area to clamp to.

John.T

You have it right. The washer is only about 2mm so does not give any problems. I would not put 2 on though.

MabBee

Thanks very much John.T, I'll try it out.

MabBee

Just for the interest of other users who might find this topic:

I notice from a wikipedia article that MTB hollowtech II BB's come with specific spacers. The article also suggests that the spacer that you have on the low-side of 10-speed cassettes is suitable as a 1mm BB spacer. So it looks like there are a few options.

Hopefully a 1 or 2mm spacer will alleviate the problem: I don't mind having the btootm 2 sprockets unusable, but 3 or 4 is just a joke. Actually, after all this hassle I'm tempted to go back to square taper. I have a nice stainless steel stronglight BB in the garage -- it would go nice with a posh TA chainset. In the long-run this might save money, since I end up replacing hollowtech II BBs every 6 months or so anyway -- they just don't last.

Iain C

I am such a muppet. Classic case of RTFM if ever there was one!

Bike came with a general bike instruction manual, which cleary I was never going to read! In my defence there was nothing SRAM specific, but only when looking at the SRAM website thanks to John T's post did I realise that the Rival front mech does have 2 settings for when it's on the small chainring! In fairness the chain rub on the inside of the big ring is there but I can live with that.

What a muppet, I can't beleive I've been riding like that for so long! :oops: