What final drive ratio should I go for with a 17" wheel conversion?

[Spiff]

I've been fiddling with a bandit swingarm and wheel and now I'm gonna order sprockets and chain but I'm not completely sure what size sprockets I should go with.
My bike is a 750 with a 850 cylinder and head.
Stock gs750 gearing is 15/41 for a 2.7xx final drive ratio, the stock bandit 1200 gearing is 15/45=3.0 final drive ratio.
But considering the new 17" wheel results in a 3.9% decrease in rolling diameter over the stock 110/90-18 I'm not sure if I should try to stay close to the stock gs gearing or the stock bandit gearing or even lower or higher as I'm sure the decreased tire size impacts the final drive(a smaller tire would be the same as a lower final drive right?)

EDIT: If my math is correct then changing from stock to 17" tires will change the effective drive ratio from 2.7 to 2.808, which is pretty negligible. But if I want the same performance as before I would have change gearing to be in the 2.59 range. I think I might have overthought this whole thing

[Agemax]

i run a 19/48 530 conversion on my GS1000 with a 17" rear wheel if thats any use.

[Steve]

Personally, it is my opinion that unless you are at a dragstrip that measures elapsed times down to 1/1000 second, you will not notice a difference in performance with the 17" wheel.

It does not really matter what the stock Bandit gearing was, you don't have a Bandit engine. It also doesn't really matter what Agemax is running, he has a 1000 engine (that has been "enhanced"), you have an 850.

By the way, if you are going from an 18" wheel to a 17" wheel, your tire choices are going to change a bit. Not sure that you will have a 110/90 available, but there is a 120/90. I don't have time to do the math right now, but the overall rolling circumference will be pretty close, likely even smaller, which would ENHANCE your performance, not decrease it.

What is your incentive for the change?

.

[Nessism]

41/15 = 2.73

If you bump the front to 18 then that same ratio suggests 49.2 (or 49 teeth). If you want to adjust for the smaller wheel/tire then you may want to bump that tooth count down one or two teeth. You should have plenty of torque to push a bigger gear.

[Spiff]

Rear tire size would be 180/55-17 for the Bandit 5.5" rear wheel.
I was thinking about a 17/46 or 17/47 combination, that's 2.7 and 2.76 respectably.

@steve my incentive for the change is looks and hopefully performance. I've swapped the front end out with a sv1000s fork and will be doing some frame bracing also, hopefully I can find a 1000cc engine to really make it a restomod.

[Steve]

OK, I saw the "Bandit swingarm and wheel" mentioned, but did not realize the size of the wheel/tire involved.

Doing the math on the tire sizes, the 180/55-17 has 96.1% of the circumference of the 110/80. In theory, that will give you a 4% advantage with no gearing changes.

.

[Agemax]

that is why i mentioned mine, 19/48 gives a 2.52 ratio. ok so it wont upset anyone on the drag strip but it still accelerates pretty fast and pulls like a train through all the gears. plus, the 19t front sprocket gives plenty of clearance for the chain on the swingarm pivot.
if you went 49 or even 50 on the rear then your acceleration would be much better.

[Spiff]

Yes that's why I was thinking of going up to a 17 front, a 19 would probably get even more clearance as you say. Thanks for the help guys!

[Spiff]

Btw. Does anyone know how long of a chain I'm gonna need? Or how I can figure that out?

[Nessism]

It's customary to bump up 3 teeth in the front when going from 630 to 530.

Stock chain is 96 links (630 chain)

96 x 3/4" = 72"

72" / 5/8" = 115.2 - round up to 116 links

Of course this is simply showing how to convert from 630 to 530. With the different swingarm all bets are off.

[Agemax]

It's customary to bump up 3 teeth in the front when going from 630 to 530.

Stock chain is 96 links (630 chain)

96 x 3/4" = 72"

72" / 5/8" = 115.2 - round up to 116 links

thats odd, in a previous thread, you swore it was rounded down to 115. changed your mind now Ed?
Anyways, wont it all be different with a Bandit swingarm fitted?

[Nessism]

thats odd, in a previous thread, you swore it was rounded down to 115. changed your mind now Ed?
Anyways, wont it all be different with a Bandit swingarm fitted?

Are you always an a-hole are just practicing on me?

Ah, negative on the calculation with the Bandit swingarm. I overlooked that detail.

[Agemax]

Are you always an a-hole are just practicing on me?

eh? lost your sense of humour now as well Ed?

[Spiff]

If you know how long one 530 link is, can you take a piece of string and wrap it around like a chain and then measure how long it is and divide it by the length of one link to find out roughly how many links you need? Maybe add some extra and remove the excess if need be....

[Agemax]

this may help.......

https://www.rbracing-rsr.com/chainlength.html