Drive Chain & Sprockets

16/45t Sprocket pairChains & Sprockets are a subject like engine oil and filters – everyone has an opinion and you can bet your last Rolo, it’s different from yours! The problem of course is that there are such a large choice of manufacturers worldwide that no two riders necessarily have the same experience of chain/sprocket combination. So this is simply my own experience and some techie info to help you better make a choice when it’s time to replace yours.

Sunstar front sprocket stress analysisThe standard Caponord has a sprocket ratio of 17(front)/45(rear) while the Rally-Raid has a ratio of 16/45 as standard, both use a 525 drive chain with a length of 112 links. The lower the number of teeth on the front sprocket, or more on the rear, the lower geared the bike is overall – lower top-speed and higher RPM at motorway speeds.

Why lower the gearing? Well some folks prefer to take their Capo’s off road and the lower gearing makes the bikes more flexible at lower speeds without having to resort to slipping the clutch – hence Aprilia nodding in that direction when they reduced the front sprocket size for the Rally-Raid. Some folks of course will never go off-road and will prefer the higher gearing for fast-road/motorway riding where the bike will feel less stressed at higher speeds. Horses for course as the saying goes!

Currently the commercially available sprockets for the Caponord are:

• Front: 15t / 16t / 17t
• Rear: 45t / 47t

To best appreciate the differences between the various sprocket sizes and combinations, I’ve put together a couple of tables regarding speeds, RPM and chain lengths to be considered.

Firstly road speed (in Mph) of the various ratios in each gear at 5,000rpm – with the top speed at 8,500rpm thrown in as well!

Table 1

Secondly the sprocket dimensions and chain turn angle as it passes around the sprocket – higher angle will promote higher wear. Also I’ve added the clearance dimension of the chain side plate to sprocket carrier … more on this later!

Table 2

Lastly the expected RPM indicated at a (EU) motorway speed of 80mph (130kmh). Also the number of teeth the particular combination has and the resultant chain length required.

Table 3

ChainSo  now the experience bit ….. well I’ve used Renthal front 407-525-16 and Sunstar rear sprockets with DID ZVM-X  drive chains since owning the Capo. Combined with a chain oiler system ( Scottoiler in my case) which is invaluable regarding extending chain/sprocket life. To date (Oct 2014) the chain/rear sprocket has over 42,000 miles and it’s on the third front sprocket – although the first two were perfectly usable, they were begining to show signs of wear.

Of course although the quality of the parts is paramount, the way they are looked after will greatly lengthen or shorten their working life. So chain oiler or can-lube? Another ticking time-bomb question to ask! So let me ask this …. if I spray a little lube onto a finger, let the solvent evaporate I end up with a highly sticky (none-fling) residue – the stuff to lube the chain/seals yes? Now dab your finger on the ground and now look a the dust/grit you’ve picked up ……. now try cleaning it off. Not easy is it. I rest my case, a light oil lubricating the seals and plates of the chain that allows dirt/grit to fling off is far more desirable than the grinding paste mix you’ll end up with from a spary can!

TIP: If you’ve a main stand fitted, briskly rotate the rear wheel backwards and forwards. If the sound made as the chain passes over the front sprocket is markedly different, drop the cover and check the teeth, they are probably worn. A new sprocket will sound almost identical when you rotate the wheel either way.

worn front sprocket after 19,410 milesUPDATE November 2014

Here is a photograph of the front sprocket that was just replaced after 19,410 miles. A slight vibration was beginning to be felt through the pegs and using the above method, it was obvious that the sprocket wasn’t in good condition. This deteriation happened quite quickly, in less than 500 miles or so. The chain was thoroughly inspected and is STILL perfectly serviceable – as is the rear sprocket. So I chose simply to replace the front sprocket. I didn’t even have to re-tension the (slightly slack) chain as the new sprocket bought it back into adjustment!

Considerations ……

Not all components are created equal! Remember that manufacturers will no doubt use different materials, manufacturing techniques and designs to produce their product. So here’s a worked example of why you should always thoroughly check out what your buying. As an example, I have a Renthal 407-525-16 front sprocket and a Sunstar equivelant. Take a look at the photograph below ……

Front sprocket tooth profileOn the left is the Sunstar sprocket, 7.15mm wide and a noticeably narrower tooth profile (less area), on the right the Renthal, 7.4mm wide and maintaining the width further up the tooth. Bottom line? Well it seems to me that the Renthal has a greater area to take load and that should mean longer life, however the wide tooth means the chain must be very well aligned to engage correctly without causing undue wear to the chain side plates, while the narrow tooth of the Sunstar will be more friendly to chain misalignment/slop – in other words, a worn chain! To my mind, one is a precision item that requires the best from the drive line to give its best, the other is a fit-and-forget (for a while!) item that will be more tolerant to drive chain abuse. You makes yer choice ……

Fitment

It is a page about sprockets after all, so I should at least give the front sprocket fitment a mention for anyone who’s been out of the galaxy for the past 15 years or so and doesn’t realise that the Capo front sprocket is fitted differently to all the other V60 engines ….

Caponord ETV1000 front sprocket fitmentClick to open bigger image

Lastly, alternative rear sprockets

Of course not everyone wants to gear their Capo down, some may want to raise the gearing to reduce the RPM further while long-distance/motorway cruising and this would entail increasing the front sprocket size (>17 teeth) or lowering the rear sprocket size (<45 teeth)…… so what’s available?

Nothing commercially as far as I’m aware – front sprockets over 17 teeth wouldn’t fit in the casing and rear sprockets run into a unique problem of their own. The possibility of the chain and sprocket carrier hitting one another. From Table 2 above you can see that a standard 45t sprocket has a clearance of approx. 5.2mm ( not a great deal) – below is a picture showing the expected clearance from a 43t & 44t sprocket.

 ETV1000 Rear sprocket sizesIn my books the clearance of the 43t sprocket is just too small to consider …. so the only viable size left is the 44t and as far as I’m aware (please chip in if you know better!) no one supplies it off the shelf. So if you do go to the expense of having one made, how would you benefit? Well that one lone tooth will buy you a measly 100rpm/3mph at best ….. is it really worth it? 🙄 Only you can decide!

5 Responses to Drive Chain & Sprockets

  1. Viv Wright says:

    Karl:

    Very useful article and data on the chain and sprocket set-ups.

    Do you have any experience or thoughts on the Ognibene “silent” front sprockets, would these improve chain life as they absorb shocks?

  2. Hi Viv,
    I was due to fit an Ognibene front sprocket a couple of months back, unfortunately I couldn’t get one in time and went with the old favourite – Renthal. I hope to have one on the shelf shortly ready for the next time! The tooth profile looks very similar to the Renthal and the damper should make a huge reduction in side-to-side vibration/noise between chain and sprocket, reducing wear. If you get one fitted before me I’d love to hear your thoughts on it.

    Cheers
    karlB

  3. Alex says:

    Hallo Karl,
    Could you clarify what mean “sprocket carrier clearance”? From technical side: advantages and minuses.
    P.S. I found 15/47 sprocket set for off-road (for exp. from Ognibene) and 18 tooth front sprocket from Afam.
    Now I would buy or produce 43 tooth rear sprocket. I prefer to keep the std. 112 links chain.

    BR
    Alex

  4. Hi Alex,
    “Sprocket carrier clearance” refers to the gap between the chain plates and the area of the sprocket carrier where the sprocket bolts onto (x6 bolts) …. take a look at the lower picture of four different sprocket sizes. At the top of each sprocket a chain link is shown with the clearance distance from it to the carrier. My concern is that the clearance of a 43 tooth sprocket is too small – especially as the sprocket will wear over time. As for an 18 tooth front …. I’m not sure it would fit into the case or give sufficient clearance for the chain onto the sliding block.

  5. Alex says:

    Thank you, Karl.
    Now I understand ))

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