adjusting front and rear mechs....?

[gazzab]

Guys
I had my bike serviced but when I was out the bike would slip from (when in gear 1 at the front) from rear gear 2 to rear gear 3. So I have started to adjust the cable at the rear mech. I have decided though that I might retune the whole system mainly cos the chain rubs against the front mech when in certain gears. So what order does one attack eg do I start with rear travel , then rear cable and then front mech ? thanks

[busta]

Pretty much what you said. The deraileur maximum travel stops ( 2 screws atop the deraileurs) and the overall cable length (adjusted at the pinch bolt on the mech) shouldn't need adjusting, just adjust the screw adjusters on the shifters. Select 1st on the back, spin the cranks and see what happens then go from there. Its all fairly simple stuff really!

[pdV6]

gazzab said:

the chain rubs against the front mech when in certain gears.

Which gears?

If you're running biggest chainring up front and one of the biggest at the back, take a look at the chain, it'll be doing somwthing like this: ``\_ and can't help but rub on the front mech.

Consider the fact that there's a lot of overlap in the gear ratios, so rather than run extremes change into the middle chainring and pick an intermdiate rear cog that gives roughly the same gear ratio but wiht a much straighter chainline.

Adjusting the rear mech, change into the middle chainring and select the 2nd smallest rear cog. Suspend the bike on a workstand (or get somebody to hold it up for you) and spin the pedals. As you gradually put pressure on the rear shifter to change to the 3rd smallest cog (i.e. shifting down a gear) as the slack takes up in the cable, the rear mech should start chattering as the chain rubs against the next cog. It shouldn't actually change gear fully until you've "clicked" the gear at the shifter. To adjust, the barrel on the shifter is easiest to get at. Winding it out (i.e. it moves from right to left) will encourage the downshift (i.e. to the next largest cog) and vice versa. Its easy to remember as the chain will try to move in the same "direction" as the barrel adjuster.

Note this advice is all back-to-front if you have a rapid-rise rear mech.

[gazzab]

you know when you wish you hadnt started something................! No ride for me tomorrow am ! aaggghhhh

[pdV6]

gazzab said:

you know when you wish you hadnt started something................! No ride for me tomorrow am ! aaggghhhh

I dunno - sounds like its not too far out actually. Try adjusting it as you ride - if the rear is reluctant to shift one way or the other, nudge the barrel adjuster on the shifter around 1/4 a turn at a time, turning it so that it goes the way you want the chain to go (i.e. reluctant to shift to a lower gear, unscrew it,,, reluctant to shift into a higher gear, screw it in).

There's always a bit of dialling-in needed when its actually under load after its been adjusted "perfectly" in the workshop.

The other thing to ask is: what did the shop actually do during the service? If a new chain's been fitted, maybe the cassette's too worn to support it, which may only be apparent under load.

[gazzab]

Thanks
Its a new chain and new rear cassette.
I have played too much and have adjusted the two screws too much and so it is very confused now. Going to try and get screws back to where they were and should then be fine tuning thereafter I hope!

[pdV6]

Aha! The mistake you made, then, was touching the limit screws at all.

All they do is set the limit for movement of the mech either way. You need to take the chain off and undo the pinch bolt that holds the gear cable to the mech. The mech will be sprung as far as it can go towards the highest gear (smallest cog). Adjust the "H" (high) limit screw until the top jockey wheel is in line with the smallest cog. Then, by hand, push the mech fully the other way to the lowest gear (largest cog) and hold it there. Adjust the "L" (low) screw until the mech lines up.

Next, click the shifter into its highest gear (8 or 9) and pull as much gear cable through the mech as you can and tighten the pinch bolt.

Put the chain back on and check that the gears index correctly - its likely to be pretty close (the shifter manages the indexing, not the mech) - and adjust as necessary using the barrel adjuster on the shifter as described earlier.

[gazzab]

thanks for advice. Got up at 7 am , fixed it and just got back from 3 hr ride! They were pretty good untl the very end when the shifting went off again. I am going to change the shifters - they seem to be inconsistent.
Jut looking at a set of Attacks on ebay. But they are marked as 9 speed. Have emailed to see if they can work on 8 speed (do you know?).

[snotrag]

- NO -

THE shifters and the Casette at the back must match.

Shifters all move the same amount of cable from highest to lowest, its the size of the increments that change.

[gazzab]

snotrag said:

- NO -

THE shifters and the Casette at the back must match.

Shifters all move the same amount of cable from highest to lowest, its the size of the increments that change.

But the advert reads Speeds 9/8 :-
Sram Attack Trigger Shifters 9 speed Pair
When you're ready to take your ride to the next level. When your goal is to move ahead, then SRAM® Attack™ is your best option. We've even added a trigger shifter to give you yet another way to add the advantages of the SRAM® Attack™ to your ride. Performance Level:: Performance Technology:: Impulse Technology(2:1 actuation ratio) Speeds:: 9/8 Weight:: 260g / pair Indicator:: Integrated clamp design Materials:: Alloy body with composite lower cover, Stainless steel hardware Push Lever:: Composite Nylon Compatibility:: Shimano® rear derailleurs, SRAM or Shimano® front derailleurs Other:: Stainless steel cables, StraightShot cable replacement

[pdV6]

That's just copied direct from SRAM marketing blurb; they make an 8sp and a 9sp model and you want the 8sp if you have an 8sp drivetrain.

As mentioned above, the shifter indexes the gears, so you need the right one for your cassette.

[pdV6]

gazzab said:

They were pretty good untl the very end when the shifting went off again. I am going to change the shifters - they seem to be inconsistent.

Note that the cables will stretch a bit when new, which means you'll have to keep adjusting the tension slightly until they've bedded in.