50 crank with 28T ok?

blackstick

My current setup is 50/34 with a 11/28 cassette. 10 speed.

Previously I used an old Ultegra 9 speed rear derailleur with the 11/28 and it shifts good.
Bought a 10 speed new 105 rear derailleur from CRC then fitted. It shifts good, but chain just kept on hitting the rear derailleur cage not matter how I tune it.
Both of it is a short cage derailleur with the 105 cage being slightly longer...
Took it to a bike shop, they said I should not run a 50 with a 28...
I know that from the Shimano tech, but I did not have any problem with an old 9 speed derailleur which does not support the bike shop opinion.

Wonder what has happened? Chain too short? I have 53 links at the moment and it is a 10 speed chain.

Dave_P1

I run a 50/34 and a 11-28 cassette on the back without any problems so I'm not sure what the shop is talking about here.
I also run a 105 short cage rear mech.

Escadrille Ecosse

I also run an 11-28 with a 50/34 and short cage 105, both 5600 and 5700, without issues

smidsy

What they mean is you should not cross chain (big front big rear) as this creates excessive wear.

If you are cross chaining some set ups will not be able to eliminate chain rub no matter how much you twiddle the settings.

Best to avoid the practice of cross chaining altogether (as you LBS states)

blackstick

smidsy wrote:

What they mean is you should not cross chain (big front big rear) as this creates excessive wear.

If you are cross chaining some set ups will not be able to eliminate chain rub no matter how much you twiddle the settings.

Best to avoid the practice of cross chaining altogether (as you LBS states)

Now I see, so its best to keep the 28T for the small crank.

rolf_f

What the shop is probably really getting at is that the overall range of gears you want is outside Shimanos recommendation. In practice, you can normally get away with it - but no guarantee. And that means potentially everything could jam up if you end up in big - big.

However, I would probably choose not to set up a bike where this was a problem. It's all very well saying 'don't use big big' but you don't want to risk the bike if it does happen. I'd certainly want to test big big and if there was a problem, try again with a couple more links in the chain - which might fix the problem.

As it happens, I do tend to accidentally cross chain a fair bit but generally the other way - if you are on a fast descent in top gear and come round a corner to an unexpected steep climb, the first thing you'll want to do is drop to the smaller chainring - so you end up in small-small. The big - big equivalent would be topping a hill and finding a steep descent on the other side. Here you probably won't need to panic and shift the chainring first!

smidsy

blackstick wrote:

smidsy wrote:

What they mean is you should not cross chain (big front big rear) as this creates excessive wear.

If you are cross chaining some set ups will not be able to eliminate chain rub no matter how much you twiddle the settings.

Best to avoid the practice of cross chaining altogether (as you LBS states)

Now I see, so its best to keep the 28T for the small crank.

Yes, similarly at the other end of the scale do not use the smallest (12 or 11 or whatever you have) when in the small front chainring.

So avoid big/big and small/small.