Recent couple gearing issues

[Two-Wheels]

So I have a couple issues that are becoming more & more of an annoyance lately & wanting to know what might be causing them and what the fix is. The bike is actually due its annual service in a couple months so I'll probably just mention it to them when it's booked in but it doesn't stop me wanting to know what's going on.

For the record, I've 8 gears at the back & 3 up front. Not sure the correct terminology or how I'm 'supposed' to say that but I'm sure you get the gist

1) The most common one - I'll be in 7 at the rear & 2 up front. I'll go to shift to 3 up front & it'll then start making a horrible noise that I can't describe in words but it just wont go in to gear at all. My only solution so far has to be 'shift' (even though it hasn't shifted from 2) back down to 2 (so in other words just move the selector back to 2 but the chain doesn't move) & try again. Some times this works, it's getting more often than not that it doesn't & I just have to wait a while.

At first I thought maybe I wasn't going fast enough because the first couple times or so my speed was questionable, but it's since happened when I've been going plenty fast enough for the change. On one I was going all out on a flat sprint & shifted up & it just wouldn't move. Kept making the horrible noise so I had to give up on the segment sprint.

2) This might've happened when I've shifted from 6 to 7 but I can't quite remember. I know for sure it happens when shifting from 7 to 8 though...
I'll shift from say, 7 to 8 & it'll certainly sound like it's shifted & I'll be going for it only to then on a random push down of the pedal will the chain 'give' & my foot/pedal just totally gives/drops to the bottom & all momentum is gone. I actually had it today when going up a bit of a climb so it must've been in lower gears. Whatever gear I'd selected - it had sounded like it had selected perfectly fine & then as I'm climbing a hill, I get so far up & the pedal/chain just 'gives'. Totally wrong moment for foot/pedal to drop to floor & lose momentum.

Sorry for the vague descriptions. Tried my best. Any ideas?

 

[Cycleops]

Sounds like an adjustment issue or some components in drive train might need replacement. If it's due a service id leave it to the bike shop.

 

[Pat "5mph"]

Hi, I'm certainly not a bike mechanic, but I know that you're supposed to ease on the pedals while changing gears, not attack the drive drain with fury

 

[Paulus]

It could be that the front mech is not going over far enough to move the chain onto the big ring.
There are several things it could be.
A mucky mech that needs a clean and some lubrication.
The limit screw needs to be loosened off a bit to allow the mech to move far enough over.
The cable needs adjusting to get enough tension to move the mech over.

Will the mech move over far enough if you move it by hand?

There are plenty of videos on you tube on how to adjust a front mech.

View: https://youtu.be/ZNG7g83lI-s

 

[Ian H]

A worn chain can adversely affect gear changes.

 

[Ajax Bay]

OP surely can't wait 2 months for the LBS to sort this.
I suggest you unclamp the front derailleur (FD) and reset it from scratch. The failure to shift onto the large chainring will be either the 'H' screw is too far in (unscrew half a turn and see if that makes a difference) or that there's a lack of tension in the cable when you are in the small chainring. Or the FD is not fit for purpose, which I think is very unlikely.
". . so I had to give up on the segment sprint"

 

[Big John]

Agree with Ajax. If you have a problem now it needs sorting so don't wait another couple of months. See if your LBS can fit you in ASAP. It's pointless us lot telling you how to fix things if the bike shop is going to be servicing it. Where I work the problems you mention would be addressed under a normal service.