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View Full Version : Bigger rear sprocket??? PHWOAR!


kwikbitch
19-Apr-2005, 23:23
Just to let you all know....Nelly fitted me a new 43 tooth rear sprocket and new chain today.....
:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D :D:D:D

Feels like a new bike!.............
:roll::bouncy::roll::bouncy::roll::bouncy::roll::b ouncy::roll::bouncy::roll::bouncy::roll::bouncy::b ouncy::roll:

Fankyou Nelly for dropping all spanners this after when I turned up 4 hours early and sorting the chain before my "important meeting" that I was an hour late for:D

nelly
19-Apr-2005, 23:28
PHWOAR........................??????

so all the explaining what a bigger rear sprocket does, why it does it and what it'd make the bike feel like, comes down to "PHWOAR......that's great" :(


now then................when's the 14T front going on then ;):devil:

andys 900ss
19-Apr-2005, 23:32
Thats the one Nelly,

You gotta try it with the 14t front too Lisa, it really boosts torque and power wheelies are in order !!! Just one thought thou', you may need the shorter 96t chain to even things out, which shortens the bike making turn in better too.

Andy

Iconic944ss
19-Apr-2005, 23:33
Hee Hee - easiest upgrade EVER isnt it !!!!!!!!!!

New head bearings anyone ???

Enjoy - Frank

Redruth
19-Apr-2005, 23:33
Originally posted by nelly
PHWOAR........................??????

so all the explaining what a bigger rear sprocket does, why it does it and what it'd make the bike feel like, comes down to "PHWOAR......that's great" :(


now then................when's the 14T front going on then ;):devil:

As usual, Lisa, you've hit the nail on the head. Perfect description of how it feels to ride the bike with that big rear sprocket. Mine's a 42 but 1 tooth is only an additional 100 revs ... or something ... according to Shazaam!. I definitely prefer the effect of that having switched from 36 just before Easter. That Phwoar is on a par with seeing Chillo with his shirt off... Doesn't get much better. ;);)

PS You're looking very bouncy ce soir x

kwikbitch
19-Apr-2005, 23:50
BLOODY BLOODY BLOODY...FLIPPIN...
FANTASTIC:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D: D:D:D:D:D

andys 900ss
19-Apr-2005, 23:52
Isnt it amazing Lisa, you alter something so trivial & it really tranforms your bike.

Really pleased it worked for you.

Andy

antonye
20-Apr-2005, 11:03
You should try 14 / 45 :D

fremoy
20-Apr-2005, 12:25
So what is the + (apart from a bigger smile on a KwikBitch) of changing the rear sprocket??

ta
Mark.

Jools
20-Apr-2005, 12:29
So size is important then :(

Oh... and Ruth...take a cold shower :frog:

antonye
20-Apr-2005, 12:32
Going up teeth on the rear will bring down your top speed, but improve the acceleration of the bike, because you're "squeezing" the output of the bike into a shorter range.

This has the side effect that you will alter the revs you are doing at certain speeds. For example, on my 748 it wouldn't sit happily at 40mph because it was too high for 1st (screaming) and too low for 2nd, in that it kept spitting and missing and generally running poor.

This made town traffic a nightmare. Changing the gearing move the range of the gears so that 1st is shorter, but in 2nd it now runs lovely at 40mph because it's slightly higher up the rev range and runs much better.

If you go the other way of removing teeth from the rear, you're making the gears "longer" and increasing the top speed, but obviously it will reduce the acceleration.

This topic has been discussed many times before and it's generally accepted that dropping to a 14t front from an original 15t (equivalent to going up 2 or 3 teeth at the rear) is the best and cheapest (a new front sprocket is about £15 from Ducati) modification you can make to most of the Ducati range.

chicken
20-Apr-2005, 12:40
Welcome aboard Mark!

The short answer is that you get faster acceleration at the expense of lower top speed. Since you rarely get to go 130mph on the roads you won't miss the latter, but you'll certainly appreciate the former!

Long answers are forthcoming from the experts.

cheers, Chi

chicken
20-Apr-2005, 12:41
beat me to it Antony. See you at Jamies!

antonye
20-Apr-2005, 12:58
:lol:

misterpink
20-Apr-2005, 17:16
so what would be good for a 748 - the front is a 14 already i think and the rear 38 or 39 from memory - so would a 14/42 combo be good?

antonye
20-Apr-2005, 17:30
I run 14 / 40, which is pretty good. It's 14 / 38 as standard and a 39 isn't going to do much.

The only problem is that 14 / 40 needs a longer chain to get the eccentric hub in the right position.

paulmort
21-Apr-2005, 16:27
Wow
So much tecky knowledge, and from such a small girlie...................

Go Lisa go..................Phwoooaaaarrrrrr indeed

see you all REALLY soon

24 hours to goooooooooooooooooooooooooooooooooooooooooooooooo

Mort missing Blooo

paulmort
21-Apr-2005, 16:29
or was it Blooo missing Mort ???????????

rich
25-Apr-2005, 23:06
OK I am convinced that i NEED this mod too!!!!!

What sizes would be recommended for the 1000SS?
What part numbers? Where to buy them from? and how much?

PLUS what about the chain, longer/shorter etc...

Would like to keep the original chain if possible.

:D:D:D:D

Shazaam!
26-Apr-2005, 02:38
For the 1000SS I recommend changing from 15/38 96-links to 15/42 98-links. You'll be geared slightly higher, but can keep your chain (and save quite a bit of money) if you just change the front sprocket to 14/38.

Mad Dog Bianchi
26-Apr-2005, 07:56
Shazaam,
what is the change in wear on the chain in going to a 14t. I did this to my SS750 and it improved acceleration of course and also made the engine spin at higher rpms on the highway, reducing gas mileage. No real chain problems on that bike, but I am thinking of doing the same thing to my ST4 as it is really geared tall. 195kmh comes very easy in 6th, but is not very usable in Japan.

Also, you are in SD and I will be there from May 14th. anyway to look you up??

Shazaam!
26-Apr-2005, 15:54
There’s not a significance difference in wear for the gearing combinations commonly-used on Ducatis, but there are three front/rear combinations that are particularly hard on chains and sprockets: 14/43, 14/44 and 14/45.

A 14-tooth front sprocket will see more wear because:

• 7% higher tooth contact pressure

• More tooth contacts per mile

(But, alloy rears usually wear faster and cost more.)

The main reason to avoid a smaller front sprocket is that it results in a higher chain tension. Just using a 14-tooth is probably OK, but when you combined it with a 520 chain that has a lower-than-stock tensile strength, it's a formula for chain failure on bikes producing more than 80Nm of torque.

14-Tooth vs. 15-Tooth Front Sprocket Wear

For (say) a 96-link chain ...

A 15-tooth front sprocket will contact the same chain link every 32 revolutions. 15 x 32 = 480 links ÷96 = every 5 chain revolutions.

A 14-tooth front sprocket will contact the same chain link every 48 revolutions. 14 x 48 = 672 ÷96 = every 7 chain revolutions.

With the same rear sprocket and at the same road speed, the 14-tooth sprocket and the 15-tooth sprocket both contact the same number of chain links per unit time.

So for example, for every 35 chain revolutions, the 15 tooth sprocket contacts the same link 7 times and the 14-tooth sprocket contacts the same link 5 times.

If we assume that there is a defect on one of the front sprocket teeth (or a particular chain link) that can cause abnormal wear to the same chain link (or sprocket tooth) when contacted over and over again, the 14-tooth sprocket would actually result in (7-5)/7 = 29% LESS defect-related wear than a 15-tooth sprocket.

However, for the same 35 chain revolutions, the 15-tooth sprocket rotates 224 times and the 14-tooth sprocket rotates 240 times so the 14 tooth sprocket (and the chain) would see (240-224)/240 = 7% MORE continuous wear than a 15-tooth sprocket.


Odd vs. Even Sprocket Teeth Wear Pattern

For reduced wear to the sides of the sprocket teeth, it’s better to run odd-numbered tooth sprockets, front and rear. Here’s why.

A chain alternates its links inside-outside such that side-to-side chain positioning is controlled by contact between a sprocket's teeth and the inside links. Because a chain always has an even number of links, each tooth on an even number-tooth sprocket will always contact either an inside link or an outside link. Each tooth on an odd number-tooth sprocket will alternate between inside and outside links that gives a uniform wear pattern to the sides of the sprocket.

Of course, this really isn't a significant problem with steel sprockets, so Ducati uses a 14-tooth front sprocket on some models. Even-tooth rear sprockets are standard on a number of models. However, if you intend to replace your sprockets with aluminum which is a lighter, but softer material, accelerated sprocket wear will be a consideration.

But who cares? A little wear on the sides of a sprocket doesn't significantly affect chain engagement.

Wear to the face of the tooth is the reason for using a hunting tooth when meshing two gears. When you have a chain-driven sprocket instead of gear-to-gear contact, the wear issue becomes avoiding the same teeth on the sprockets repeatedly meshing with the same links on the chain.

http://home.san.rr.com/shazaam/SprocketWear.jpg

How often the same tooth meshes with the same link can be calculated by comparing the number of teeth on each sprocket to the number of links in the chain.

The first step is to factor the number of teeth and links into prime numbers. Here’s some common results:

Front Sprockets

14 tooth - factors: 7x2
15 tooth - factors: 5x3

Rear Sprockets

36 tooth - factors: 3x3x2x2
37 tooth - factors: 37
38 tooth - factors: 19x2
39 tooth - factors: 39
40 tooth - factors: 5x2x2x2
41 tooth - factors: 41
42 tooth - factors: 7x3x2
43 tooth - factors: 43
44 tooth - factors: 11x2x2
45 tooth - factors: 5x3x3

Chain Links

94 links - factors: 47x2
96 links - factors: 3x2x2x2x2x2
98 links - factors: 7x7x2

Two numbers are defined as relatively prime if they have no common factors. The front sprocket/chain combinations from above that are relatively prime are:

15 tooth front - 94 link chain, 98 link chain
The sprocket and chain will meet at the same spot every 15 turns of the chain and 94 or 98 turns of the sprocket respectively.

14 Tooth front - none of the combinations are relatively prime. If the two numbers aren't relatively prime, then the number of turns will be divided by the common factors. For example:

14 tooth front - 94 link chain
Here, 14 (7x2) and 94 (47x2) have the common factor of 2. Consequently, the sprocket and chain will meet at the same spot every 7 turns of the chain and 47 turns of the sprocket.

14 tooth front - 96 link chain
Here, 14 (7x2) and 96 (48x2) have the common factor of 2. Consequently, the sprocket and chain will meet at the same spot every 7 turns of the chain and 48 turns of the sprocket.

14 tooth front - 98 link chain
Here, 14 (7x2) and 98 (7x7x2) have the common factors of 2 and 7. Consequently, the sprocket and chain will meet at the same spot every 1 turn of the chain and 7 turns of the sprocket. Not very good for wear.


The rear sprocket/chain combinations are computed separately, the same way as for the front. Here’s the result for combinations that are commonly used:

36 tooth rear (18x2) - 94 link chain (47x2)
Here, the common factor is 2. Consequently, the sprocket and chain will meet at the same spot every 18 turns of the chain and 47 turns of the sprocket.

38 tooth rear (19x2) - 94 link chain (47x2)
Here, the common factor is 2. Consequently, the sprocket and chain will meet at the same spot every 19 turns of the chain and 47 turns of the sprocket.

38 tooth rear (19x2) - 96 link chain (48x2)
Here, the common factor is 2. Consequently, the sprocket and chain will meet at the same spot every 19 turns of the chain and 48 turns of the sprocket.

40 tooth rear (5x2x2x2) - 96 link chain (12x2x2x2)
Here, the common factor is 2x2x2. Consequently, the sprocket and chain will meet at the same spot every 5 turns of the chain and 12 turns of the sprocket.

42 tooth rear (21x2) - 96 link chain (48x2)
Here, the common factor is 2. Consequently, the sprocket and chain will meet at the same spot every 21 turns of the chain and 48 turns of the sprocket.

42 tooth rear (21x2) - 98 link chain (49x2)
Here, the common factor is 2. Consequently, the sprocket and chain will meet at the same spot every 21 turns of the chain and 49 turns of the sprocket.

44 tooth rear (22x2) - 98 link chain (49x2)
Here, the common factor is 2. Consequently, the sprocket and chain will meet at the same spot every 22 turns of the chain and 49 turns of the sprocket.

45 tooth rear (5x3x3) - 98 link chain (49x2)
No common factors. Consequently, the sprocket and chain will meet at the same spot every 98 turns of the chain and 45 turns of the sprocket.

These results are sumarized in the above table.


Send me a U2U so we can make arrangements to meet while you're in San Diego.

[Edited on 4-26-2005 by Shazaam!]

Mad Dog Bianchi
29-Apr-2005, 02:09
Thanks. U2U in the mail!