Wheel sizes VS dodgy speedo

[markov1723]

Gday

I am being a bit dim today but heres the deal..

Our lovely bongo is 8 mph slower than its speedo says.

WE have the standard 195/65 R15 wheelsetup and I have read the Alloy database spreadsheet about wheel size / roll etc vs sppedo fluctuations.. so my idea is to look at wheels to get the speedo accurate.. and make ze bongo look a bit cooler

I cant for the life of me work it out, like i say having a dim day

Anyone help?

Ta much

[g8dhe]

If the scale was changed perhaps the needle was put back on in the wrong position and not calibrated?

[markov1723]

If the scale was changed perhaps the needle was put back on in the wrong position and not calibrated?

Thats a poss. Its been like it since day one though. Im kind of used to it, just trying to use this as an excuse for bigger wheels

[g8dhe]

If its a constant offset no matter what the speed then that is the most likely, if its always 0.95 of the speed then that would suggest its a ratio problem.

[skater]

WE have the standard 195/65 R15 wheelsetup

Standard is 215/65/15 on the rear, which is bigger.
When I had these my speedo read 60mph and the sat nav 57
so I guess your satnav says 52 when speedo is 60?

If you get bigger tyres your speed will be truer.

[markov1723]

WE have the standard 195/65 R15 wheelsetup

Standard is 215/65/15 on the rear, which is bigger.
When I had these my speedo read 60mph and the sat nav 57
so I guess your satnav says 52 when speedo is 60?

If you get bigger tyres your speed will be truer.

Ahh, thought mine was standard ;-0 what i probably/subconciously menat was mine has the tyres it came with.. maybe. Im pretty sure they are same front and rear but will have a check.

Yep, thats the one.. for residential i have to do 42 ish to be doing 30 and we are getting into summer season so lots more road traps round here than usual

[Northern Bongolow]

put a GA5R speedo in out of a early mazda 626 then see how it is then, no speedo chip then needed, mines spot on with 15 inch wheels and tyres. and its in mph both speedo and oddmeter. simplze.

[markov1723]

put a GA5R speedo in out of a early mazda 626 then see how it is then, no speedo chip then needed, mines spot on with 15 inch wheels and tyres. and its in mph both speedo and oddmeter. simplze.

Hmm, £30 speedo off weevilbay or £700 on chromed 18" wheels..I know which one makes sense for the future.. equally I may keep this option quiet

[jutwit]

try this for changing the wheel and tyre size

http://www.kouki.co.uk/utilities/visual ... calculator

[splitpin]

Mine is similar to yours, when speedo reads 50 the true speed is 43, I think is something to do with the speedo facemarkings being changed to mph, I have heard hat it is possible to re position the needle to compensate for this but havent tried this myself. I did toy with the idea of fitting larger tyres/wheels but decide to leave as is and just make allowance for difference , has been like this for five years now so am used to it.

[splitpin]

Mine is similar to yours, when speedo reads 50 the true speed is 43, I think is something to do with the speedo facemarkings being changed to mph, I have heard hat it is possible to re position the needle to compensate for this but havent tried this myself. I did toy with the idea of fitting larger tyres/wheels but decide to leave as is and just make allowance for difference , has been like this for five years now so am used to it.