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 Post subject: Re: Cheap di2 group
PostPosted: Tue May 23, 2017 7:54 am 
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Joined: Fri Nov 04, 2016 3:43 pm
Posts: 40
The RD cannot decipher between a 10 or 11 cog cassette (number of spockets). It will always think it is 11spd. If you put a 10 spd cassette on (still with 11 spd spacing) and you try to click into the 10th cog (last). The RD will hit the high limit screw hard (where it normally has free space) and the safety feature will kick in and it will automatically shift the RD to the 9th cog to protect the motor. The RD will regard the limit screw position as being extreme and then force it out of harms way. The high limit screw should not ever be touching the stop. It should be loosened outwards 1 full turn from where the RD finally stops in line with the last cog. This because Di2 RD has an overshift feature (called overstroke allowance) at the end of the cassette. In normal operation the RD shifts slightly further past the last cog then it corrects itself and aligns. If you prevent the RD from doing so you could then potentionally damage the servo, or put load on the servo and cause the battery to quickly drain.


Last edited by SL1 on Wed May 24, 2017 6:44 am, edited 1 time in total.

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 Post subject: Re: Cheap di2 group
PostPosted: Tue May 23, 2017 12:17 pm 
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Joined: Wed Jan 10, 2007 10:56 pm
Posts: 1386
Location: Canada
You should read the manual. The biggest gear on the cassette has the limit set to just touching the stop. It's only on the smallest gear that you put the stop one turn beyond touching to allow overshift. And since that stop isn't being reset all is good. The limits are adjusted as per normal. As I said, this is a pretty standard method that has been used many many times without issue.

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 Post subject: Re: Cheap di2 group
Posted: Tue May 23, 2017 12:17 pm 


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 Post subject: Re: Cheap di2 group
PostPosted: Wed May 24, 2017 7:32 am 
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Joined: Fri Nov 04, 2016 3:43 pm
Posts: 40
That's exactly what i said. The high limit screw (top side stopper) and smallest cog (11t)

Here's the manual. Page 68

http://si.shimano.com/pdfs/dm/DM-UL0001-03-ENG.pdf

Im not sure i follow you. If you did not reset the high limit screw for the 10th last cog, as you describe, If you leave the high limit screw open (i think that's what your saying ?) then the RD buttons would still have the 11 potential positions. So that would introduce the possibility of accidently shifting from the 10th cog to the 11th cog (which has been removed) and would then allow the chain to be thrown off the outside of the 10th cog. Would it not ?

I dont see how the low limit screw position can be reset. If its even touching the screw a tiny bit too much it will auto shift to the next cog. So i dont see how you could move that 1 gear inwards.

If it can be done and made to work then somebody else can chip in and comfirm it.

Then i will admit to being wrong.


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 Post subject: Re: Cheap di2 group
PostPosted: Wed May 24, 2017 1:51 pm 
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Joined: Wed Jan 10, 2007 10:56 pm
Posts: 1386
Location: Canada
Ok. Once you modify the cassette as per DarkSpeedWorks blog (11 speed cassette modified to remove one gear), you adjust the limits as per the manual for this "new" 10 speed cassette. The limits are adjusted as per this manual page, where the limit at the largest gear end is just touching the stop, and the limit for the smallest gear end is one turn beyond the stop. If you do that, and then try to move past the stop for the biggest gear, to the phantom 11 gear, it will hit the stop and go back as you say.

Apologies for the post to another forum, but there are lots of people on slowtwitch.com who have done this successfully without issue, including this post from the Felt rep.

http://forum.slowtwitch.com/forum/?post=4988062#p4988062


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