Topic: tire and wheel sizes

[KRONUS0100]

just oredered a saet of morris mags off of a kz750 4 cylinder.....1981.
the fron it 19x3 and the rear is 16x4.
my stock comstars are like 1.85x19 front and i think 18x2.25 rear........with a 120/90-19 on it.
the seller says there was a stock 130/80-16 on the rear Morris.   anyone got the math formula to figure out how much shorter/taller the new set up is going to be?   its coming with a 630 pitch rear sprocket, so i gotta switch the front out.
thanks alll.
Matt

[KRONUS0100]

     update.they have arrived, and they are NNOT MORRIS MAGS or KAWI clones.   they are the ENKEI's.  16x4 rear, and 19x2 front.  will convert rear to 530 pitch, and will prolly need offset front sprocket.   they are goin on my 76 CB750F.

[KRONUS0100]

oopsy, forgot pic.

[lucky]

A very good set of wheels!!!

[lucky]

Tire size formula for OD with tire, By LUCKY.

Lets say the tire is a 100/90-19.
Here is the formula for outside diameter.

.90 x 2=1.8 x 100=180( devided by)25.4=7.0+19"=26" diameter

[KRONUS0100]

thanks for the formula.  my planned new rear tires should be roughly an inch shorter in height than the old one was.

[lucky]

You are welcome KRONUSO100!

[EDU]

thanks for the formula.  my planned new rear tires should be roughly an inch shorter in height than the old one was.

You'll be fine then. It should reduce 'flickability' a little (not much at all) but if the new wheels are lighter you won't even notice. Also, if you want to keep the gearing close to what it was, just run a rear sprocket with one less tooth 'cause by running a smaller tire you've also shortened your gearing a little.

[KRONUS0100]

home from vacation.  will have to upgrade/replace the front rotors.  they are smaller and closer together than what i have now on the comstars.  found a set of rotors from a 800 Vulcan that have same inner diameter and bolt hole spacing, plus they are 300mm, so my calipers from the gs1150 will fit now, once i make the mount adapters for them to the goldwing forks.

[lucky]

thanks for the formula.  my planned new rear tires should be roughly an inch shorter in height than the old one was.

You'll be fine then. It should reduce 'flickability' a little (not much at all) but if the new wheels are lighter you won't even notice. Also, if you want to keep the gearing close to what it was, just run a rear sprocket with one less tooth 'cause by running a smaller tire you've also shortened your gearing a little.

One less tooth on a rear sprocket will do almost nothing, and it would be expensive and may not even be available.

If the gearing is too low, go one tooth larger on the front sprocket.
It will be much easier to get, and cost a lot less money.

[EDU]

thanks for the formula.  my planned new rear tires should be roughly an inch shorter in height than the old one was.

You'll be fine then. It should reduce 'flickability' a little (not much at all) but if the new wheels are lighter you won't even notice. Also, if you want to keep the gearing close to what it was, just run a rear sprocket with one less tooth 'cause by running a smaller tire you've also shortened your gearing a little.

One less tooth on a rear sprocket will do almost nothing, and it would be expensive and may not even be available.

If the gearing is too low, go one tooth larger on the front sprocket.
It will be much easier to get, and cost a lot less money.

I get an extra 5km/h on the straight when dropping a tooth on my race bike, not very perceptible at all to be honest. But changing the tire diameter can throw your speedo off, that's why I suggested keeping the gearing close to what it is.