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Re: Dropped chain with chain spotter [lyrrad] [ In reply to ]
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lyrrad wrote:
Youngtano wrote:
SummitAK wrote:
Youngtano wrote:
lyrrad wrote:


The real problem here is manufacturers substituting cranks and running out of spec chainstays.
I am the local mechanic.



You are a mechanic? Like to your neighbors or friends, or one who works in a shop? Please show me the chapter in the unwritten rule book of frame design where it states what makes a chainstay in or out of spec. Also, please tell me how you'd appreciate a customer (or your neighbor) coming to you and saying "fix your F up".


The specs actually come from the component manufacturers based on such things as the front derailleur to be utilized, chainring diameters, rear hub width, etc. Go short on the chainstays and there will be shifting performance trade-offs due to the chainline. Experienced mechanics understand these issues.



Just out of curiosity:

What kind of shifting issues would I have if my bike has standard 135mm hub spacing, a chainstay length of 40.5, 53/39 chainrings, Di2 group, a chain length of 108 links, with a B tension gap of 3.8mm on a 25T cassette. Let's say for simplicity, I'm running a Shimano crank with Shimano chainrings, just incase you want to bring shifting ramps or chainring flex into this.

If you could provide your complex experienced mechanic math formula to calculate this, it would be greatly appreciated.

Asking for a friend.


You also need to consider the BB and the associated chainline.
Also where the front derailleur is mounted in relation to the chainring, as in it rotation around it as well as it's setback.
But 40.5 is right on the minimum limit for chainstay length for a complete Shimano road setup.


Let me know when you both can answer my original question, on your own. Lyrrad, congratulations on knowing how to do a basic front derailleur setup.

Also, the chainstay length mentioned, is from an S3 disc.
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Re: Dropped chain with chain spotter [lyrrad] [ In reply to ]
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Go here:


http://si.shimano.com/#/


Everything you ever wanted to know about every Shimano product made.
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Re: Dropped chain with chain spotter [lyrrad] [ In reply to ]
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lyrrad wrote:
Go here:


http://si.shimano.com/#/


Everything you ever wanted to know about every Shimano product made.


So, YOU can't answer. Thank you. That's all I wanted to know.
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Re: Dropped chain with chain spotter [Youngtano] [ In reply to ]
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Youngtano wrote:
lyrrad wrote:
Youngtano wrote:
SummitAK wrote:
Youngtano wrote:
lyrrad wrote:


The real problem here is manufacturers substituting cranks and running out of spec chainstays.
I am the local mechanic.



You are a mechanic? Like to your neighbors or friends, or one who works in a shop? Please show me the chapter in the unwritten rule book of frame design where it states what makes a chainstay in or out of spec. Also, please tell me how you'd appreciate a customer (or your neighbor) coming to you and saying "fix your F up".


The specs actually come from the component manufacturers based on such things as the front derailleur to be utilized, chainring diameters, rear hub width, etc. Go short on the chainstays and there will be shifting performance trade-offs due to the chainline. Experienced mechanics understand these issues.



Just out of curiosity:

What kind of shifting issues would I have if my bike has standard 135mm hub spacing, a chainstay length of 40.5, 53/39 chainrings, Di2 group, a chain length of 108 links, with a B tension gap of 3.8mm on a 25T cassette. Let's say for simplicity, I'm running a Shimano crank with Shimano chainrings, just incase you want to bring shifting ramps or chainring flex into this.

If you could provide your complex experienced mechanic math formula to calculate this, it would be greatly appreciated.

Asking for a friend.


You also need to consider the BB and the associated chainline.
Also where the front derailleur is mounted in relation to the chainring, as in it rotation around it as well as it's setback.
But 40.5 is right on the minimum limit for chainstay length for a complete Shimano road setup.



Let me know when you both can answer my original question, on your own. Lyrrad, congratulations on knowing how to do a basic front derailleur setup.

Also, the chainstay length mentioned, is from an S3 disc.

As specified, your chainline is out but in a good way if you are using road group crank and not a cross series crank.
Experience on Cervelos, I built quite a few, but not an S3 disc, says chainstays run short but manageable.
Your S3 sounds a little longer.
So I don't predict any problems with your setup.
In your favour is a small largest cog on the rear as well as a slightly inboard chainline that says shifting on that side of the cassette will be fine. You may find some quirkyness when in the small cogs in the back and not be able to run the smallest couple in small front chainring.
If running 11 speed, watch out for the chain going too far into the dropout when shifting into very top gear and you will have to back out the B tension a little to prevent the chain coming off and getting stuck.
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Re: Dropped chain with chain spotter [lyrrad] [ In reply to ]
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lyrrad wrote:
Youngtano wrote:
lyrrad wrote:
Youngtano wrote:
SummitAK wrote:
Youngtano wrote:
lyrrad wrote:


The real problem here is manufacturers substituting cranks and running out of spec chainstays.
I am the local mechanic.



You are a mechanic? Like to your neighbors or friends, or one who works in a shop? Please show me the chapter in the unwritten rule book of frame design where it states what makes a chainstay in or out of spec. Also, please tell me how you'd appreciate a customer (or your neighbor) coming to you and saying "fix your F up".


The specs actually come from the component manufacturers based on such things as the front derailleur to be utilized, chainring diameters, rear hub width, etc. Go short on the chainstays and there will be shifting performance trade-offs due to the chainline. Experienced mechanics understand these issues.



Just out of curiosity:

What kind of shifting issues would I have if my bike has standard 135mm hub spacing, a chainstay length of 40.5, 53/39 chainrings, Di2 group, a chain length of 108 links, with a B tension gap of 3.8mm on a 25T cassette. Let's say for simplicity, I'm running a Shimano crank with Shimano chainrings, just incase you want to bring shifting ramps or chainring flex into this.

If you could provide your complex experienced mechanic math formula to calculate this, it would be greatly appreciated.

Asking for a friend.


You also need to consider the BB and the associated chainline.
Also where the front derailleur is mounted in relation to the chainring, as in it rotation around it as well as it's setback.
But 40.5 is right on the minimum limit for chainstay length for a complete Shimano road setup.



Let me know when you both can answer my original question, on your own. Lyrrad, congratulations on knowing how to do a basic front derailleur setup.

Also, the chainstay length mentioned, is from an S3 disc.


As specified, your chainline is out but in a good way if you are using road group crank and not a cross series crank.
Experience on Cervelos, I built quite a few, but not an S3 disc, says chainstays run short but manageable.
Your S3 sounds a little longer.
So I don't predict any problems with your setup.
In your favour is a small largest cog on the rear as well as a slightly inboard chainline that says shifting on that side of the cassette will be fine. You may find some quirkyness when in the small cogs in the back and not be able to run the smallest couple in small front chainring.
If running 11 speed, watch out for the chain going too far into the dropout when shifting into very top gear and you will have to back out the B tension a little to prevent the chain coming off and getting stuck.



Mr. Madison, what you've just said is one of the most insanely idiotic things I have ever heard. At no point in your rambling, incoherent response were you even close to anything that could be considered a rational thought. Everyone in this room is now dumber for having listened to it. I award you no points, and may God have mercy on your soul.
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Re: Dropped chain with chain spotter [Mackanic] [ In reply to ]
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All hail Mr Madison, whoever he is?
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Re: Dropped chain with chain spotter [Mackanic] [ In reply to ]
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Mackanic wrote:
Just out of curiosity:

What kind of shifting issues would I have if my bike has standard 135mm hub spacing, a chainstay length of 40.5, 53/39 chainrings, Di2 group, a chain length of 108 links, with a B tension gap of 3.8mm on a 25T cassette. Let's say for simplicity, I'm running a Shimano crank with Shimano chainrings, just incase you want to bring shifting ramps or chainring flex into this.

If you could provide your complex experienced mechanic math formula to calculate this, it would be greatly appreciated.

Asking for a friend.

You're being pretty rude. And your chainstays don't meet Shimano's spec for a 135OLD bike.



This is for everything except DA9100. SRAM has the same issues and that's why they have their 'wide axle' cranksets.
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Re: Dropped chain with chain spotter [Mackanic] [ In reply to ]
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Mackanic wrote:
lyrrad wrote:
Go here:



http://si.shimano.com/#/


Everything you ever wanted to know about every Shimano product made.



So, YOU can't answer. Thank you. That's all I wanted to know.


https://en.wikipedia.org/wiki/Argument_from_ignorance
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Re: Dropped chain with chain spotter [tommyrus11] [ In reply to ]
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To the OP, what kind of chainspotter are you using? A couple different types are pretty easy to remove and reinstall without messing up your FD adjustment (SRAM and K-Edge Pro). That'd probably be the easiest way. Taking your crank or even just the large chainring off could be your next option. Or if you have a quick link and the right tool, breaking your chain might be an option.

Did this even happen while shifting? It's happened to me a few times after putting my rear wheel back on after transporting it in my car. The chain would come off of the bottom of the ring since there wasn't enough tension on the chain without the cassette, then when putting the wheel back in the cranks would backpedal and it would force the chain past the chain spotter. If that's the case, there's likely nothing wrong with your set up.
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Re: Dropped chain with chain spotter [lyrrad] [ In reply to ]
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lyrrad wrote:
All hail Mr Madison, whoever he is?

Just a movie quote from Billy Madison.

Look, I'm not trying to be rude. I'm trying to see if the question can be answered and present a challenge for the two guys who are mechanics on here. It was said that chains can't or won't (don't remember which preface was used) fall off the front ring if the derailleurs are set up properly. To which I chimed in and disagreed. From that point, I presented the challenge in reply to your remark of "manufactures need to stop making frames out of spec as it causes problems" or something to that effect.

The problem I wrote out, came from the top of my head, the frame geometry in relation to chainstay length, was right from Cervelo's website. Anyone can fish out tech doc's online, but tech doc's don't fix bikes, mechanics do. That's why I was asking the two of you.

So, apologies if I offended you with my words, but know that I was presenting a challenge and trying to pick your brain once you presented this to be an equation-ish solvable problem. Or that's how I perceived it at least.

Carry on.
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Re: Dropped chain with chain spotter [Mackanic] [ In reply to ]
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The problem is you are asking for an exact answer when you simply haven't supplied enough information to do so.
The combination of chain stay length, rear derailleur bolt position, front derailleur position, rear mech, front mech, crank and chainrings, rear cluster configuration creates an almost infinite combination and is not simply calculable.
I gave you the likely problem you will find with the setup you proposed and that is of over shifting onto the last cog and also offered up the answer that has worked in the field.

But most Tri bikes are out of suggested spec by component manufacturers and push the limits of workability.
All that needs to be done is increase both the chainstay length as well as the front centre and all of these problems go away.

Still, however far these bikes are out of spec, it is normal with modern groups to be able to have them work with proper setup and anti chain drop devices.
There are a shitload of differing devices and each frame configuration requires some thought as to which one to implement.

This is not out of the realms of any proficient bike mechanic to orchestrate.
Hence my comments re taking it back and make them fix it.

There are some combinations of components that simply won't work.
We generally know of them or can spot the potential trouble before it becomes a dropped chain during a race.

The general cycling tri public has come to accept as normal that chains drop, and that is simply not right.
They drop because they have not been set up competently and manufacturers are so far out of recommended spec that anything less than perfect and they will give problems.

This needs to change.
The only thing that should ever slow you down mechanically on the bike during a race is an unfortunate puncture.
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