Just wondering about changing my chain and sprockets. 2001 748s so I assume 14/38T on a 94 link 520 pitch chain (dark outside, garage locked, can't be arsed to look!).
I wouldn't mind going up to 40 on the rear to gain a few more revs per mph - not particularly for better acceleration, but to make town riding a bit easier (I did a similar thing on my Monster and it just made lower speeds easier to cope with).
Questions are:
Where is a good place to buy them? Would like a gold chain and pretty rear sprocket ideally. Renthals I assume require a carrier at 100 odd quid so I have read on B+C Express. Are there other manufacturers recommended?
Will I need to go for a 96 link chain?
What will this do to my ride height? I have recently had it set up properly so am a bit reluctant to undo this work.
It depends on how high your ride height is now. The effect on rear ride height is variable depending upon the initial clock position of the eccentric chain tension adjuster which is why you should take a initial height measurement before making the change so you can reset it to the desired height.
Here’s a way to estimate the effect on wheelbase and ride height.
As delivered from the factory, a stock bike will have its ride height adjuster rod set in the lowest position. So the ride height can be raised from this position, but not lowered.
For a given length chain, and for rear sprockets in the range of 38 to 43-teeth, adding one tooth will DECREASE the distance between the center of the front sprocket to the center of the rear sprocket approximately 4mm.
This also decreases the wheelbase by a similar amount and raises the ride height. If the ride height adjuster is initially set in its lowest stock position then the way to compensate for this is by raising the front ride height an equal amount.
The eccentric adjuster has a limited allowable range of rotational adjustment. The rear axle should be confined to the lower rear quadrant.
A 5xx chain has a link pin-to-pin distance of 5/8-inch or 16mm. Links need to be added in pairs so adding two links increases the distance between sprockets about 16mm.
Also, note that for a given length chain, changing from a 15-tooth to a 14-tooth front sprocket will INCREASE the distance between the center of the front sprocket to the center of the rear sprocket approximately 4mm. This also increases the wheelbase by a similar amount.
So to answer your question.
First, measure your ride height.
Then, replace your 38-tooth with a 40-tooth rear sprocket. This will decrease the distance between sprockets about 2 x 4mm = 8mm.
Remeasure your ride height and you’ll see that you’ve raised your ride height a similar amount.
Decrease the length of your adjuster rod to lower the rear ride height back to the starting position. If it has never been adjusted it’s already at its shortest length. If it has been raised previously but cannot be shortened enough to get back to the desired ride height you’ll then need to replace the chain with another one 2-links longer.
Adding 2-teeth adds (say) 8mm ride height
Adding 2-links reduces (say) 16mm ride height
So now with a longer chain, when you remeasure ride height you’ll see that you need to increase the adjuster rod length (which you can now do) to recover to your desired rear ride height.
Just been reading this. Can I assume then, if I want to add one or two teeth to my standard 38 tooth sprocket as I 've been thinking of doing, I will probably get away with NOT having to replace the chain for a longer one?
Probably not Mike, assuming you have a 748. Because of the swingarm length, the 748 14/38 stock set-up is right on the cusp of needing a longer chain. A 14/40 (which I recommend for a 748) will need a longer 96-link chain in order to allow you to recover your stock rear ride height.
(Please everybody update your profile to include your Ducati year and model.)
I was only thinking of going to a 39. Because it's had a Baines conversion I didn't really want it reving much higher, I'm quite happy with it. Just wanted to take that endge off for town.
Think I'll get away with it? I haven't been bothered to lift the bike ans fiddle yet to see if I could
Hancym, changing from a 38 to a 39-tooth rear sprocket will raise your engine speed at 120 kilometers/hour by 140 RPM. Not worth the effort or expense in my opinion. But, you can probably get away with using the same chain if you also raise the front end to match the ecpected increase in rear ride height. However, you'll also get a shorter wheelbase however that tends toward decreasing high speed stability.
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shazaam, i have a 37 tooth stm rear sprocket in the post, what effect will this ahve on my bike, i'll be running a 14 tooth at the front, will a standard size chain be okay ???
Shazaam!
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