Author Topic: Clutch Cable Length  (Read 1351 times)

Online RichardL

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Clutch Cable Length
« on: 06.09. 2015 21:30 »
Trying to reckon the best way to calculate clutch cable length and looking for comments on my ideas. This stuff will be common knowledge for many here, but not me. I was using the original '55 cable (out of service from '79-'03) until it frayed a month ago and I grabbed the cable off of my '57 barn find. That cable was fine for a couple of rides but got much too sticky, and oiling didn't help. I was unable to make a working cable from the scrap and now face prime riding days without a working bike.

I will have a typical adjuster at the lever and the threaded tube adjuster at the gearbox. My thinking is that I should position both of these adjusters in the center of their travel and measure housing length between them. Then, I figure add the minimum exposed cable length to reach the unengaged clutch operating lever and the un-pulled handlebar lever. Is this close to the way it's done? Should the adjusters be positioned for the maximum housing length instead (or vice versa)?

Thanks, guys. It seems no matter how long I play this game there is some rule I am yet to encounter.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Online bsa-bill

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Re: Clutch Cable Length
« Reply #1 on: 06.09. 2015 21:45 »
I think you should allow for inner cable stretch Richard, (doubt it will shrink) so I'd set the adjusters to allow for that at a future date
All the best - Bill
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Re: Clutch Cable Length
« Reply #2 on: 06.09. 2015 23:22 »
When making cables I usually screw all the adjusters fully in, then out maybe one turn, then make the cable fit. I then usually find I need to screw the adjusters out a couple of turns after fitting the cable.
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Offline duTch

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Re: Clutch Cable Length
« Reply #3 on: 07.09. 2015 02:39 »

 I'll second both the above
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Online RichardL

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Re: Clutch Cable Length
« Reply #4 on: 07.09. 2015 05:09 »
Have to admit, never thought about the workings of my cables as much as I am right now. Trying to get my head around where clutch cable adjustment comes from or if there even is such a thing. The housing must remain trapped between the adjusters and the needed length of exposed cable is fixed for a given clutch activating arm position. If you unthread one or both adjusters you're just bending the housing with the cable inside. Maybe that pulls marginally on the cable, but doesn't seem a great way to plan for adjustment. This leaves me with the feeling that the only true adjusment for the clutch may be the screw behind the oval cover. I think I hope I'm missing something obvious.

Richard L.
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Re: Clutch Cable Length
« Reply #5 on: 07.09. 2015 07:28 »
Well there are only two critical dimensions - one being that the overall length reaches well enough without going around the houses three times, and the other is the differences between the inner and outers. The adjusters are only there to maybe allow the cable to be fitted, and then just to take up minor differences.

Best bet is to note that inner to outer difference when you have a good fitting cable, then make up to that next time out. Not much help if you've already substantially stretched or busted all of yours.

Adjustment at the arms and levers should really be used to allow them maximum advantage I would have thought.

Surely someone here can give a measurement for this that should be suitably average? I'm not even remotely near my bike right now.
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Offline sparx

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Re: Clutch Cable Length
« Reply #6 on: 07.09. 2015 07:30 »
I think the "obvious" that you're missing is that the outer cable doesn't "bend" to any extent when it's compressed. Think of it as a solid tube that is flexible.
 
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Online RichardL

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Re: Clutch Cable Length
« Reply #7 on: 07.09. 2015 08:11 »
I think the "obvious" that you're missing is that the outer cable doesn't "bend" to any extent when it's compressed. Think of it as a solid tube that is flexible.
 

Agreed, the adjusters can put the housing under greater (or lesser) compression. So, it seems, if centered when measuring for the housing, they can also expose more or less cable at one end or the other by turning one in and one out. It also seems there is no compensating in the adjusters for a cable that is overall too long or too short (as I believe was Butch's point).

Richard L.
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Online bsa-bill

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Re: Clutch Cable Length
« Reply #8 on: 07.09. 2015 08:34 »
Quote
It also seems there is no compensating in the adjusters for a cable that is overall too long or too short

The critical measurement is not the overall length or lack of (provided it will reach the two points of anchorage) but the difference between the inner and the outer, this is what the adjusters adjust
All the best - Bill
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Re: Clutch Cable Length
« Reply #9 on: 07.09. 2015 10:29 »
G'day Richard.
Just measured mine. The gearbox adjuster is part of the cable, the hand lever adjuster stays in the perch. So with the inner removed from the gearbox lever and the hand lever & perch and pulled till the nipple is against the gearbox adjuster there is 2 and 3/8" of inner to the inside of the hand lever nipple. Pics explain it better.
When it's all together the adjusters are at their smallest giving full length adjustment.
Cheers
Thought I'd better add. The gearbox adjuster is 1 and 3/4" so that makes the inner 4 and 1/8" longer than the outer not counting the nipples. Clear as mud!
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Offline duTch

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Re: Clutch Cable Length
« Reply #10 on: 07.09. 2015 11:19 »

 Richard, you may be over complicating it....I just referred to my 'notes' (which I had to edit to understand), but with adjusters top and bottom came up with a difference of ~108mm between the outer and inner, which is fairly close to Muskies 4+1/8" ...If you're making your own, do the top nipple and back off all adjusters, as per previous advice, and locate the bottom one where it needs to be, and you can't go wrong...Best to have at least one, preferably both nipples with swivel capabilities
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Online RichardL

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Re: Clutch Cable Length
« Reply #11 on: 07.09. 2015 14:48 »
Quote
It also seems there is no compensating in the adjusters for a cable that is overall too long or too short

The critical measurement is not the overall length or lack of (provided it will reach the two points of anchorage) but the difference between the inner and the outer, this is what the adjusters adjust

Bill, It seems to me that the outer ("housing") must remain trapped between the adjusters, so I can't see how they they can affect the difference between the inner and outer while doing that job.

Muskrat, I get your photos and they are helpful. Dutch could be right about overcomplicating (it is one of my faults, which are many) but I have more questions. But first, let's call it 2-9/16" so we're measuring to the center of the pull hole. The question is, is 2-9/16" at the lever the exact length between the inside of the adjuster to the center of the pull hole (lever not pulled, of course)? You say "adjusters are at their smallest" but this confuses me. I'd like to have the adjuster at the lever as far into the perch as possible for stability. So, this raises the question: assuming your cable inner and outer fit perfectly, what are the adjuster positions? are they all the way in or about halfway into the gearbox thread and lever? No need to be exact because another thing at play here is if we have the exact same perches? I can already see we don't have the same lower adjusters (mine will have the thumbwheel).

Dutch, Thanks for your contribution. Please explain "back off all adjusters." Do you mean before or after deciding on the housing length?

OK, I have well-tortured this topic and maybe all my friends here. Thanks for any additional info or opinions you have time or interest in offering.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Online RichardL

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Re: Clutch Cable Length
« Reply #12 on: 07.09. 2015 14:57 »
When making cables I usually screw all the adjusters fully in, then out maybe one turn, then make the cable fit. I then usually find I need to screw the adjusters out a couple of turns after fitting the cable.

I should have mentioned earlier that this seems quite logical to me for fitting the housing.

Richard L.
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Online RichardL

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Re: Clutch Cable Length
« Reply #13 on: 07.09. 2015 16:28 »
All in unison now, "Group groan."

Looking at the photo, you can see the distance from the rear of the adjuster to the center of the pull hole. Taking into account the depth inside the adjuster, if I let 2-9/16" be exposed here, the adjuster will be out of the perch. If 2-9/16" is the total exposed (with the bottom adjuster on the cable), it appears the cable will come up about 3/8" short.

Obviously, I'm determined to beat this to death. Feel free to grab a bludgeon and join in if you want, but if I've proven myself too thick to absorb advice, you are free to sit in the stands and just point your thumbs up or down while I await the lions.

Richard L.

Edit: The photo is upside down, but so what.
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Online bsa-bill

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Re: Clutch Cable Length
« Reply #14 on: 07.09. 2015 17:48 »
Quote
Bill, It seems to me that the outer ("housing") must remain trapped between the adjusters, so I can't see how they they can affect the difference between the inner and outer while doing that job.

 because screwing the adjusters in or out alters the length of the outer in comparison to the inner, you have the length of the adjusters to add to or subtract from the original length of the outer.
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All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco