new tyres - speedo 10mph out??

[eggy790]

lol ok i think the standard steelis come with 175/65/14 tyres on

bought some renault steelis off here that came with new 195/45/14 tyres on it.

i used to have 185/55/15 alloys on which was 3mph under according to sat nav

so 70 = 67mph on gps

but with these new steelis

70 on speedo = 60/61mph according to the sat nav!!!

lol i take it sat nav/gps is the more accurate one?

so basically ive got to rev higher to drive at 70? as the revs are the same yet im going slower

wtf have i done lol

well confusing, going to spoil my fuel consumtion i take it?

least ive got less chance of being caught speeding..

is this correct? the speedo is over reading? and the gps speed is the one to follow (give or take 1mph or 2?

cheers

 

[Tobs]

see ive heard that sat nav ones are more accurate but i dont think that they are, one example is, think of all the millions and millions of sat navs in the country being used, i dont think a computer could keep up with them all at once to be honest, there must be some sort of delay.

maybe we need a sat nav satelite geek to put us straight

anyone?

 

[eggy790]

yeah i know what you mean but im pretty sure the majority use 50mph on gps when going through the average speed check cameras on motorway and not the speedo.. i know my cousin does and he travels up and down it every week and not got a ticket.. that reads around 55mph on his speedo

i dont know but basically i think my wheel is smaller so not getting as far as it would with the old wheels? hence why im going slower?

it doesnt feel slower lol but thats because im revving higher and the decatted exhaust is louder lol

 

[DrR]

see ive heard that sat nav ones are more accurate but i dont think that they are, one example is, think of all the millions and millions of sat navs in the country being used, i dont think a computer could keep up with them all at once to be honest, there must be some sort of delay.

maybe we need a sat nav satelite geek to put us straight

anyone?

Lol what?

Does Radio 1, your TV etc go slower if more people listen to it?

 

[DrR]

http://www.alloywheels.com/tyrecalc.asp

Your new tyre Circumference is 9%ish smaller.

 

[eggy790]

according to that my speed would be 63.6 at 70mph.. which is probs right as sat nav is saying 61mph when dead on 70 on speedo so the gps is a little delayed i take it.

lol nothing i can do to make it more accurate? or just got to put up with the speedo over reading?

 

[realnumber 1]

see ive heard that sat nav ones are more accurate but i dont think that they are, one example is, think of all the millions and millions of sat navs in the country being used, i dont think a computer could keep up with them all at once to be honest, there must be some sort of delay.

maybe we need a sat nav satelite geek to put us straight

anyone?

PMSL, are you been serius lol.

 

[pablo_ni]

epic post! My BBC1 was a bit slow last night right enough.

 

[Groovejunkie]

Stands to reason that your speedo will read faster than you're actually going... !! It measures by revolutions of the axle surely... so if you alter the circumference of the wheel/tyre making it smaller then distance travelled per revolution will be reduced!?!

It's not rocket science!!!

 

[eggy790]

lol ok thats understood now, anyway to make it more accurate other than change the wheels? lol think ill just have to put up with it

 

[Groovejunkie]

I've always thought you can have it calibrated... that's what police cars have to have done to be able to verify you've been speeding isn't it... !?!

 

[eggy790]

where cud i get this done?

 

[Jamesy04]

Stands to reason that your speedo will read faster than you're actually going... !! It measures by revolutions of the axle surely... so if you alter the circumference of the wheel/tyre making it smaller then distance travelled per revolution will be reduced!?!

It's not rocket science!!!

this man has hit the nail on the head.... good shout groovie! :approve:

 

[motorola222]

a speedo vs sat nav argument is flawed all cars manufactured after 1999 have to be calibrated to 0.01% accuracy basically its only allowed to 0.01% out. and even then the law states it has to state ur going faster than u r. so yes ur sat nav is acuratish but chances are the speedo is right. in ur case thought uve thrown it off ballance, dont worry though u can have it re calibrated for about £30 ive heard.

 

[motorola222]

this man has hit the nail on the head.... good shout groovie! :approve:

also i think speedos work of gearbox speed not the axle itself.

 

[Jamesy04]

i always thought it was axle speed... im not 100% sure its not the biggest thing since the beggining of man-kind so it's eithier of them, you could be really anal and find out if you wanted to, but it wouldn't greatly improve my life by knowing this for sure! haa haa! The calibrater guy would be able to tell you anyways...

 

[motorola222]

i always thought it was axle speed... im not 100% sure its not the biggest thing since the beggining of man-kind so it's eithier of them, you could be really anal and find out if you wanted to, but it wouldn't greatly improve my life by knowing this for sure! haa haa! The calibrater guy would be able to tell you anyways...

+1

 

[eggy790]

lol anyone know where i can get it recalibrated then?

 

[ChrisPearson]

see ive heard that sat nav ones are more accurate but i dont think that they are, one example is, think of all the millions and millions of sat navs in the country being used, i dont think a computer could keep up with them all at once to be honest, there must be some sort of delay.

maybe we need a sat nav satelite geek to put us straight

anyone?

Comedy.

 

[motorola222]

Not sue tbh

 

[Rockford]

Always wondered this. Roadside speed signs that flash up with your speed to warn you to slow down always read the exact same speed as the speedo, never what the sat nav says e.g car says 34mph, sign says 34mph sat nav says 29mph.

 

[pablo_ni]

they dont round my way

 

[motorola222]

Always wondered this. Roadside speed signs that flash up with your speed to warn you to slow down always read the exact same speed as the speedo, never what the sat nav says e.g car says 34mph, sign says 34mph sat nav says 29mph.

sat navs satalites are 260 miles abouve the earth there is bound to be some delay and there only acurate within 1 metre as a result sat nav will be out slightly.

The road signs are radar guided and calibrated specifically for that purpose.

 

[pablo_ni]

260miles isnt far for a radiowave. you can talk to someone in the states with next to no lag.

 

[motorola222]

Satalites use microwaves not radiowaves radiowaves can't penatrate the ionisphere in the upper atmosphere they bounce right off it's the reason u can pick up radio luxemborg for example the waves bounce of the upper atmospherse and reflect back down. Yeah ur right it isn't far but u must concider a gps needs a minimum of 3 satalites to triangulate ur position these satalites talk to each other work out ur distance from each other work out ur position multiple times a second and then relay the information back to the ground.

Any questions?

 

[pablo_ni]

now you're being pedantic.

The GPS in your car doesnt communicate anything back to the satellites so the satellites dont have a clue where you are. The GPS unit does it by working out the signal delay from 3 sats and triangulating.

 

[motorola222]

That makes more sense but admit there us delay which is y ur speed is sometimes out.

 

[pablo_ni]

radio waves are what, 2/3 the speed of light? 260 miles is nothing.

 

[motorola222]

I do see ur point mate but by the time tom tom has processed and worked out the next lot I've already moved a few metres

 

[pablo_ni]

lol ok mate. tom tom use an abacus or something for processing?

 

[motorola222]

Stop being flipant. My point is there is a delay and an abacas is a calculator not a processor. There are other things like weather and emf that can effect it.

 

[ThePea]

radio waves are what, 2/3 the speed of light? 260 miles is nothing.

Radio waves travel at the speed of light iirc

 

[KDF]

see ive heard that sat nav ones are more accurate but i dont think that they are, one example is, think of all the millions and millions of sat navs in the country being used, i dont think a computer could keep up with them all at once to be honest, there must be some sort of delay.

maybe we need a sat nav satelite geek to put us straight

anyone?

OMG. I am literally dumbfounded.

 

[motorola222]

Io think ur right mate

 

[motorola222]

Lol @ kdf