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Discussion Starter · #1 ·
Hi, I realize there have been many posts like this before and I have read quite a few of them, but still have some questions. As the title says, I am doing the 520 conversion on my 2013 Ducati Corse. I also plan on increasing the number of teeth on the rear sprocket, +2, i.e. to 41. I wanted to go +3 to 42 but unfortunately the stock is none existent.

Based on what I have read, adding teeth at the rear will increase the rear ride height, and, if I want to restore it, I would need to buy adjustable ride height rod as the original one is solid. BUT, and here start the questions, as fare as I understand, adding rear ride height would make the bike turn in more easily, something with which I struggle to begin with. Why would I then want to restore the ride height? What would be the down side of leaving rear ride height as is, i.e. a couple of mm higher?

If I add +2 teeth at the back and go to a narrower pitch, how many links would I need on the chain? According to Gearing Commander - Motorcycle Speed and Drive Train Calculator v7 it is 100 links, is that with or without the master link? I thought 100 links were the norm with these kind of conversions, but the dealer said I should get 102-link chain and that got me a bit confused.

Finally, any experience with the AFAM kit for this conversion? Have no experience with them so far, any input would be appreciated.
 

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Determining Chain Length

Here's the deal — first count the number of links in your chain. Yes, that includes the master link. Then measure the rear ride height.

Tire Wheel Automotive tire Motor vehicle Hood

This is how you measure rear ride height changes.

Every additional tooth on the rear sprocket shortens your wheelbase about 4 mm. So going from a 39 to a 41 tooth rear sprocket shortens it 8 mm. A shorter wheelbase will reduce your high speed handling stability.

Using an eccentric chain tension adjuster, this also raises the rear ride height. Raising the rear ride height changes the handling characteristics from the standard developed by Ducati test riders. The rear ride height adjuster is delivered from the factory at its shortest length so you can't bring the rear ride height back down to the correct amount without machining the adjuster rod.

Using a two link longer chain adds (5/8-in) 16 mm to your wheelbase. For a 15/41 gearing you get a (16 minus 8) 8 mm longer wheelbase having more stability, and a lower rear ride height that can be easily be brought back up to the stock height.
 

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Discussion Starter · #3 ·
Determining Chain Length

Here's the deal — first count the number of links in your chain. Yes, that includes the master link. Then measure the rear ride height.

Every additional tooth on the rear sprocket shortens your wheelbase about 4 mm. So going from a 39 to a 41 tooth rear sprocket shortens it 8 mm. A shorter wheelbase will reduce your high speed handling stability.

Using an eccentric chain tension adjuster, this also raises the rear ride height. Raising the rear ride height changes the handling characteristics from the standard developed by Ducati test riders. The rear ride height adjuster is delivered from the factory at its shortest length so you can't bring the rear ride height back down to the correct amount without machining the adjuster rod.

Using a two link longer chain adds (5/8-in) 16 mm to your wheelbase. For a 15/41 gearing you get a (16 minus 8) 8 mm longer wheelbase having more stability, and a lower rear ride height that can be easily be brought back up to the stock height.
thanks for replying, was hoping actually you would, as I have read many of your previous posts on this topic and consider myself more knowledgeable because of it :).

if I am getting this right, since I will add 2 T in the back and at the same time prolong the original chain, which has 98 links, by 2 links, I can readjust the ride height by tightening / slacking the chain?

I had a more detailed look at the current setup done by the previous owner, he had 14 T at the front, 39 at the back and 100 link chain, which is puzzling to me, as I thought you dont need to change the chain lenght, if you go one T down in the front.

Can you please confirm, for my intended setup, i.e. 15/41, a 100-link chain is ok?
 

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Rim Bicycle part Machine Nickel Font


If you are starting from the original Ducati configuration of 15T/39T 98-link chain, and when you have the correct chain tension, the eccentric adjuster has rotated the axle placement to be near the 4 or 5 o'clock position, the ride height adjuster rod will be at its shortest length, and the bike rear ride height and wheelbase will be correct.

Note that the correct chain tension is achieved by rotating the eccentric adjuster, and although a byproduct of this is a change of ride height, it would be incorrect to set the chain tension out-of-spec to achieve a different ride height or wheelbase.

When the previous owner changed to 14-tooth front sprocket, in order to achieve the correct chain tension the eccentric adjuster needed to be rotated from the 4-5 o'clock position a small amount toward the 3 o'clock position — not enough to require a shorter chain. Then adding two links to get a 100-link chain caused the eccentric to be rotated even further toward 3 o'clock with the (possibly intended for high speed stability) effect of lengthening the wheelbase but with the additional effect of lowering the rear ride height. So you need to check if the ride height adjustment rod was previously lengthened if you want the handling with the new sprockets and chain to be correct.

A 15/41 100-tooth combination will move your axle back 8 mm from stock, and when the chain is tensioned, will move the eccentric back towards the 3 o'clock position. This lowers the rear ride height. You need to determine the previous owners rear ride height rod adjustments.

EVERY sprocket and chain length change on Ducati models using eccentric adjusters will change both wheelbase and rear ride height — that in turn affect handling.

Note below how sprocket/chain combos affect axle position (wheelbase).

Font Material property Pattern Parallel Number
 

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Such a process, any change in rear axle eccentric adjustment effects, wheelbase, ride height, and sag....but so very important the bikes overall stability and and handling......😎
 

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Discussion Starter · #6 ·
If you are starting from the original Ducati configuration of 15T/39T 98-link chain, and when you have the correct chain tension, the eccentric adjuster has rotated the axle placement to be near the 4 or 5 o'clock position, the ride height adjuster rod will be at its shortest length, and the bike rear ride height and wheelbase will be correct.
If I am getting this correctly, if the rear ride height rod is original, which I am pretty sure it is, by changing to a 15/41 100-link combo and correctly tightening the chain, I should be only slightly off of the original geometry? And, IF I then want to get back to the original geometry 100 %, I would need to either replace the original solid rod with an adjustable one or machine the original one. But as said, I might prefer the new geometry as is.
 

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If I am getting this correctly, if the rear ride height rod is original, which I am pretty sure it is, by changing to a 15/41 100-link combo and correctly tightening the chain, I should be only slightly off of the original geometry? And, IF I then want to get back to the original geometry 100 %, I would need to either replace the original solid rod with an adjustable one or machine the original one. But as said, I might prefer the new geometry as is.
Correct. A+
 
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