Yet another 1x11 packpedalling thread

Spagoose

I wont go into massive detail because I'm sure most of you know the compaint I'm talking about; that in the lowest gear on a 1x11 the chain will drop onto higher gears if you backpedal.

https://www.boardmanbikes.com/gb_en/pro ... t-8.8.html

I have had this bike completely replaced 4 times now, each one by a different store and every time without fail the bike has the exact same issue with the mechanics having no clue on how to fix it.

I have contacted boardman about it and they are telling me this shouldn't be happening at all full stop. In addition to this I found a display model which had zero backpedalling issues. I was also under the impression that this issue was largely limited to shimano drivetrains and that SRAM issues were much more uncommon.

My questions now are, is there a simple fix for this or do boardman hardtails just have terrible chainlines? Should I just reject these bikes and look elsewhere or keep trying new ones until one works? I'm limited on the C2W scheme and other halfords bikes are not really an option for me so anything else I look at will be much less value for money.

steve_sordy

I had a 1x11 SRAM set up that I fitted to replace a Shimano 2x10. I had none of the problems you refer to. I also have had two different SRAM 1x12 set ups, one came with the bike, and one that I used to replace a Shimano 2x10. Again zero problems with backpedalling.

If you believe that it is the chainline that is causing it why not have it adjusted?

Until then, don't backpedal!

cycleclinic

For starters measure the chain line. It could be chainring used. What are the differences between the demo bike that works and the bikes you have had. The answer is there, either in the chain line or the chainring used.

Spagoose

The bikes had the entire same drivetrain, chainring included so the chainlines should be identical.

Also because I have not accepted the bike I can't do any tinkering with it so at most I can just ask the techs to check this and that.

Also apart from moving bottom bracket spacers, how else wold I be able to adjust the chainline? I am not keen on moving the cranks off-centred from the frame.

cooldad

Mechs are not designed to back pedal. It happens.

Why the need to back pedal anyway?

steve_sordy

Spagoose wrote:

..........

Also apart from moving bottom bracket spacers, how else wold I be able to adjust the chainline? I am not keen on moving the cranks off-centred from the frame.

In addition to redistributing the BB spacers, I have also on occasion found it necessary to add washers behind the chainring to move it closer to the frame.

I aim to set the single chainring directly in line with the centre line of the cassette. If you can't get it bang on, err towards the frame.

Spagoose

cooldad wrote:

Mechs are not designed to back pedal. It happens.

Why the need to back pedal anyway?

Moving the pedals in a position to clip in easier, to do ratcheting on technical climbs and to avoid pedal strikes.

robertpb

Sounds more like the mech needs adjusting to me, put it on a bike stand and adjust the mech until it stops doing it.

The other thing to check is the wheel alinement correct, is the cassette free of wobbles.

cycleclinic

Since the op has not even got the bike he can't check anything. So it is probably best to buy a different bike now as the op is asking us to help with a problem on a bike he does not own yet.

robertpb

thecycleclinic wrote:

Since the op has not even got the bike he can't check anything. So it is probably best to buy a different bike now as the op is asking us to help with a problem on a bike he does not own yet.

Read carefully "I have had the bike replaced 4 times"

So he seems to have the bike.

Spagoose

thecycleclinic wrote:

Since the op has not even got the bike he can't check anything. So it is probably best to buy a different bike now as the op is asking us to help with a problem on a bike he does not own yet.

Yeah, I was more hoping someone might come along and say "Oh yeah I had this issue, you just need to do XYZ."

Halfords have been pretty reluctant to actually look into this issue other than building new ones again and again and have pretty much left me in a position to either figure it out myself or get something else.

But like you say I'm not in a position to tinker with the bike myself.


I actually noticed something else about the display bike that was fine; the paint finish was different to the bikes that were built up for me. As in the display bike had a matt paint finish while the newer ones were glossy.

I am starting to think that maybe it could be a batch issue with some of the frames.

I spoke with boardman on the phone and they could only suggest moving the BB spacer and that maybe this is normal behaviour but also maybe not, nothing really definitive. They also say that this is the first they are hearing of this issue but after 4 in a row having this issue I find that hard to believe. Maybe I am just getting unlucky.


Just to clarify, I paid for the bike but after the first one I have not taken any home from the store yet, I don't want to take one home for them to turn around and say they wont fix it under warranty/replace it if I can't figure it out myself. This way I can still just get a refund.

I'm thinking of giving them one last go because otherwise I am gonna end up at leisurelakes getting something more expensive with lesser components.

robertpb

When you say you are not in a position to tinker with the bike, why?

Never had a new MTB in 33 years that I didn't tinker with within hours of purchase.

The last bike I bought from Halfords was a Boardman team CX, changed the stem the same day of purchase, adjusted the gears which are 1x11 and tightened the crank arms.

Within a month the saddle had been changed, mtb 29" tubeless wheels put on and a set of WTB 40c Nanos.

Spagoose

robertpb wrote:

When you say you are not in a position to tinker with the bike, why?

Never had a new MTB in 33 years that I didn't tinker with within hours of purchase.

The last bike I bought from Halfords was a Boardman team CX, changed the stem the same day of purchase, adjusted the gears which are 1x11 and tightened the crank arms.

Within a month the saddle had been changed, mtb 29" tubeless wheels put on and a set of WTB 40c Nanos.

The bike is currently at Halfords, they are waiting for me to either take the bike as is (ie the latest one they have built which still has issues) or decline it and get a refund. They are not interested in finding a solution it seems. If I take it and can't sort it out myself then they are unlikely to agree to take it back again.

robertpb

So go to Halfords get them to put the bike on a stand then get them to pedal it backwards and adjust it properly, it's not a problem with the bike only the adjustment.

Most mechanics do this anyway when adjusting.

cougie

How far are you back pedalling ? It should be less than a full rotation ? Does this happen in the shop with that much back pedalling ?

Spagoose

cougie wrote:

How far are you back pedalling ? It should be less than a full rotation ? Does this happen in the shop with that much back pedalling ?

There's no specific amount that is required before it drops, sometimes it happens as soon as you start going backwards, sometimes it makes a couple rotations, but more often than not, it happens in less than 1/2 a rotation.

billycool

Something isn't right and if Halfords/Boardman can't give you a bike that doesn't work how you want it to, I'd ask for a refund.

It's a shame as Boardman are such good value for the money.

I'm not sure how much you need to back pedal, but if it's dropping the chain it's not great.

It's up to you but I wouldn't want a brand new bike having an issue with no apparent solution.

Spagoose

I have asked Halfords to give the derailleur adjustment ago as robertpb has suggested, I'm waiting to hear back on that front.

I also tried Leisure Lake bikes to see what the deal with their 1x11s were. Turns out they were all doing it and the staff says that it is normal...

So I'm in a weird limbo where I don't know if it is faulty or it's just a quirk or the system. I'll update once I hear back anyway.

Vino'sGhost

operator error.

the chain will frequently seek to find the optimal chainline if you pedal backwards. At the extremities of the cassette the chainline is in its most suboptimal state. the pick ups and other cassette and chainring features are not designed for reverse direction and so the chain moves.

the symptoms you describe are perfectly normal. Generally speaking when starting off and clipping in theres no reason to be in the smallest cog anyway. In fact that is suboptimal too even if youre at the top of a F off drop off like an olympic BMX start ramp.

Vino'sGhost

why does the chain seek an easier chainline? because its bending slightly in order to get on the cog. get a length of chain and bend a small amount of it a few degrees and you can feel for yourself the pressure to return.

so why dont the chain mfrs develop a chain more able to bend without spring back? Simple its a trade off with longevity and strength. were asking the chain to do something its not ideal to do. if we used heavier chains such as those found in the the bmx and track worlds the problem would be worse. Lighter and more flexible and the result would be broken chains.

I suspect were about as far as we can go without a change in link length standards.

JBA

Vino'sGhost wrote:

operator error.

... Generally speaking when starting off and clipping in theres no reason to be in the smallest cog anyway. In fact that is suboptimal too even if youre at the top of a F off drop off like an olympic BMX start ramp.

He isn't on the smallest cog. He is in the lowest gear.

Spagoose: It's not unusual for the chain to skip down the cogs when you back pedal. There are 5 bikes in my household; 2 of them skip on back pedalling, 2 never do and 1 sometimes does. They are all set up correctly with optimal chain lines.
In real life riding though it is never really a problem as the most I ever back pedal is half a rotation to start off or reposition the pedals.
Stop worrying about it and start riding the bike.
Also learn how to set up the derailleur correctly so you can tweak it if necessary.

Vino'sGhost

JBA wrote:

Vino'sGhost wrote:

operator error.

... Generally speaking when starting off and clipping in theres no reason to be in the smallest cog anyway. In fact that is suboptimal too even if youre at the top of a F off drop off like an olympic BMX start ramp.

He isn't on the smallest cog. He is in the lowest gear.

Spagoose: It's not unusual for the chain to skip down the cogs when you back pedal. There are 5 bikes in my household; 2 of them skip on back pedalling, 2 never do and 1 sometimes does. They are all set up correctly with optimal chain lines.
In real life riding though it is never really a problem as the most I ever back pedal is half a rotation to start off or reposition the pedals.
Stop worrying about it and start riding the bike.
Also learn how to set up the derailleur correctly so you can tweak it if necessary.

Well even if he’s in the biggest cog the same applies re chain line.

Any chain that is not straight is sub optimal. It’s a limitation of the system and a law of physics. Full stop.

steve_sordy

Vino'sGhost wrote:

..............
Any chain that is not straight is sub optimal. It’s a limitation of the system and a law of physics. Full stop.

I agree a chain that is not working in a straight line is working in a sub-optimal manner. But it is not against the laws of physics.
There is a small gap between the inner and outer side plates that enables that deflection in addition to any elastic bending of those plates themselves. This ability of chain to deflect like that is why bicycle chain has a high mechanical efficiency on a derailleur equipped bike. It is why chain on a derailleur equipped bike has not been replaced, despite well over 100 years of development.

FishFish

Vino'sGhost wrote:

It’s a limitation of the system and a law of physics. Full stop.

Well conservation of energy is not violated and momentum too given that it is not a closed system. There are no issues with parity so I think that you are discrediting physics.