Adjusting speedo, due to diff ratio change

[Pablouk]

Just curious, what are you asking is correct ?

Your speedometer indicates what it does.

Your GPS (or police radar/laser) gives some indication against standard.

That is really the only difference that matters.

I was asking if my reckoning is correct. I have no idea if my odo is set correct.

 

[TURBO200R4]

I have some information the triumph diff ratio is 2.846:1 Tyre 240/R16 50 outside circumference 79.9"
mine diff ration is 2.9:1 Tyre 275/R18 35 outside circumference 80.3

Difference mines reading 1.4% fast, is that correct?

if ? your figures r correct then u would be off 1/2 mile in a 100 miles and a guess of the speedo reading 95 when doing 100 mpr.
just to be on the safe side i would measure the circumference on both tires.

 

[warp9.9]

I have some information the triumph diff ratio is 2.846:1 Tyre 240/R16 50 outside circumference 79.9"
mine diff ration is 2.9:1 Tyre 275/R18 35 outside circumference 80.3

Difference mines reading 1.4% fast, is that correct?

.00498132 % faster

 

[Ralsmith]

.00498132 % faster

I got 1.37% faster in my math, either way it negligible

 

[Pablouk]

I got 1.37% faster in my math, either way it negligible

I didn't use a calculator

 

[Pablouk]

I was asking for 3rd party to verify my calcs, I think 1.4% reading fast is fine.