Speedo Error with larger Tyres

[nanbar]

It does read slower. Before...travelling 97 reads 100. Now....travelling 97 reads 97.

I thought he meant slower again but perhaps you’re right (and so was he)

[Hogey66]

As expected, speedo reads bang on now despite Bob Jane man telling me it would read slower!

It does read slower. Before...travelling 97 reads 100. Now....travelling 97 reads 97.

[nanbar]

As expected, speedo reads bang on now despite Bob Jane man telling me it would read slower!

[CamJam]

Use this...

https://www.willtheyfit.com

Type in what you have, then type in what you want. Then look down the left hand side and it will magically give you all the data that's probably on the half-dozen sheets of paper you currently have. Provided by someone else on here - so I can't take credit for it - but it's a bloody good site for those looking at seeing how much speedo will be in/ out and the distances wider/ taller/ more/less offset wheels will produce..

[MacroP]

Just note that the odometer will be out with the larger tyres. The speedo has an intentional (conservative) error with standard tyres as you know but the odometer is normally spot on so a change of tyre diameter will affect the odometer and the trip computer readings - slightly.

[nanbar]

Cheers guys

[carco]

I have 265/75's on my 90 instead of the factory 265/65's.
It's the only car I've ever owned where the speedo is spot on.
Just be sure you can readily buy the alternative sized tyres when out in the sticks. You might get stuck waiting for a delivery from the big smoke.
Mr's i-30 is doing around 94 at 100 indicated, seems the trend for today's cars to read low.
I notice the 90's power is not quite as good, makes a bit of difference when you don't have much to start with.

Yes correct.

[nanbar]

Just wanted to double check something. My speedo currently reads around 3 kph more than my actual speed with standard tyres (265/65/17) at 100 kph. That is, when the speedo reads 100 kph, I am actually doing 97 (by my gps, dash cam and speed app), 3% less. So if I put 265/70/17 tyres on it (~3% taller), my actual speed with be ~3% higher than my speedo correct? So by these calcs, my speedo will read close to spot on with larger tyres. I think this logic is correct, thoughts?