Weird Boardman/Rival front mech problem

Holyboy

So I had an urgent gear adjust today for a customer doing the Wicklow 200 tomorrow, he left the bike with me for a while, I put it in the stand and done the usual adjustments all seemed perfect so I took it on a little test ride and the rear gears weren't indexing properly so a slight adjustment on the road and all seemed perfect once again, back in the shop and in the stand again rear gears were off, left it and took another spin and they were perfect, all good I thought as I've had bikes before that work in the stand but when ridden they don't and vice versa, so customer comes to collect it and I suggest a quick spin just to make sure, he returns and can't get the chain to shift to the large ring, I jump straight on and it shifts perfect, I suggest he hold the shifter in untill the chain picks up and less pressure on the pedals but it still won't engage, back in the stand it goes I show him it shifts well, so he tries and yes in the stand he can shift to the outer ring,more test rides follow with various adjustments but still not working for him, in the end I had to unscrew the H limit screw out loads and when in the stand the chain over shifted every time but on the road with him it didn't,there's about a five stone weight difference (he's not a fatty I'm just very light) I even thought at one stage it could be a broken frame but checked it all over and nothing.
Any mechanics had this problem before, it's a new one for me!!!!

kona

Yup, and the only way I got it to work was with a **** load of cable tension, so much so that on the down shift the shifter made a fairly loud bang.

****ing hate sram

Actually I had a Hybrid Boardman in during the week, and the chain was actually trying to shift up on the chainset without any input to the front mech, it even did it when I pulled the mech right away from the chain.

What happened was is chain was crossing so bad in 8 and 9 that it was being pulled onto the little castings on the top gear on the chainset to help the mech shift. In 7 years I have never ever seen that before. I dont know who to blame. Sure maybe Halfords, they must have done something haha

Lemag

This may seem stupid and obvious but you've adjusted the cable stop, right? I recently converted to SRAM and I had a bit of hassle getting up on to the big ring. I found, as Kona mantioned, that a lot of tension was required along with a fair bit of adjustment with the cable stop on the down tube.

Holyboy

kona wrote: »

Yup, and the only way I got it to work was with a **** load of cable tension, so much so that on the down shift the shifter made a fairly loud bang.

****ing hate sram

Actually I had a Hybrid Boardman in during the week, and the chain was actually trying to shift up on the chainset without any input to the front mech, it even did it when I pulled the mech right away from the chain.

What happened was is chain was crossing so bad in 8 and 9 that it was being pulled onto the little castings on the top gear on the chainset to help the mech shift. In 7 years I have never ever seen that before. I dont know who to blame. Sure maybe Halfords, they must have done something haha

Hmm, sounds like a good way to bust a shifter!!!

I've had the problem of the chain being picked up by the shifting pins and ramps on the large ring a lot over the years,it's usually just poor chainline, it can be sorted either by adjusting the spacing on the rear hub slightly or some chainring spacers.
But the problem yesterday only happened when the customer was on the bike and not me and the only difference was weight!
I noticed yesterday that when I shift gears it's always at the same stage in the pedal revolution so I changed when I was shifting and it was still perfect for me but as soon as he got on it just wouldn't shift, it's just odd!

kona

Holyboy wrote: »

Hmm, sounds like a good way to bust a shifter!!!

I've had the problem of the chain being picked up by the shifting pins and ramps on the large ring a lot over the years,it's usually just poor chainline, it can be sorted either by adjusting the spacing on the rear hub slightly or some chainring spacers.
But the problem yesterday only happened when the customer was on the bike and not me and the only difference was weight!
I noticed yesterday that when I shift gears it's always at the same stage in the pedal revolution so I changed when I was shifting and it was still perfect for me but as soon as he got on it just wouldn't shift, it's just odd!

I dont think the shifter has broken and this was almost a year ago. Yea I put some washers on the chainrings as I didnt wanna **** about with the rear wheel as they have poxy avid brakes which are a total ballache sometimes.

I find sometimes when shifting, especially with BSO gripshift, you can shift better by applying a different approach, usually holding the shifter until it shifts.

What was the angle and height of the front mech like on the Boardman? TBH if you can make it work on the stand and on the road, Id be inclined to blame the way the customer is using the gears for it not shifting.