Speedo reading incorrectly with larger alloys?

[Stoned]

Just wondering, now i've gone to 16" wheels with 195/45 rubber I should presumably find the speedo reading slower due to the larger wheel circumference right?

Does anyone know how much the effect is?

Most speedo's overread slightly anyhow so I might now find it's actually bang on!

 

[geetee]

This will tell you all you need to know.

http://www.net-comber.com/tirecalc.html

Cheers
GeeTee 8)

 

[Stoned]

Cool

But I have no idea what specs the original wheels and tyres were?

Can anyone tell me?

 

[geetee]

I believe the standard wheels / tyres are 195/55 on 14 inch rims

So you'll be doing 66.35mph when ur speedo reads 65mph.

Speedos are only accurate within about 5% anyway so I wouldn't worry about it.

Just lose a few mph past cameras and ur OK.

Cheers
GeeTee 8)

 

[Anonymous]

I'm on 17's and whenever i go thru a camera i always loose 5mph off the speed limit just to make sure. bloody tax cameras :evil:

 

[geetee]

I'm the same. I crawl past the buggers.... I don't trust the combination of low profile 17's and el cheapo kmh->mph conversion black box to keep my license safe past these tax machines.

I must get a Road Angel or the like.

Cheers
GeeTee 8)

 

[mattygti-r]

i dont go on the speedo no more dont trust the crappy converter

i go on the Apexi

 

[geetee]

How does the Apexi calculate ur speed... I presume it still takes a read of the same speed sensor??

Unless it does some clever satellite bollox.... but then I wouldn't trust that either. I've been reading a lot in the trade press recently about mandatorily enforced speed limits...

The current projection by the government is to have this in force by 2010. Your speed is monitored by both roadside sensors and GPS systems... this is hooked into the car's ECU and will limit your driving forcefully by changing the map / fuel feed / ignition timing etc etc.

This scares the sh1t out of me... most of the stuff I read on this is in the motorbike trade circulations. It is legit and it is going to happen. From a biking perspective, it's madness... if you're mid corner and the 'system' decides to cut your power you're in grave danger of a possibly fatal highside.

I can see the benefit of enforcing a particular speed on congested roads to stop the surge effect but the scope of current proposals goes way way beyond that.

This new system is under practical trial (yes they have got that far!).

I think I have gone a little off topic here.

I'll scan and post the articles in another thread.

Cheers
Geetee 8)

 

[AJ4]

luckily a new dawn is breaking.... the days of grease monkey mechanicals is finally coming to an end and the electronics boys are taking over. In the past, most good mechies have been treated like gods in the tuning industry, but not for much longer. For a long time us electronic gimps have just been faceless nerds, forced to suffer ridicule at the hands of our mechanical betters, our day is coming !!! <manic world dominating chuckle>

Seriously though, if they ever come up with some electronic method for speed control, I _guarantee_ it will get hacked and disabled. And there are a damn site more electronic engineers out there than mechanics who would love to get there heads round this sort of system....

I personally can't wait until all cars are run on electric fuel cells and all the theiving rip-off mechanical tuners are out of a job...

 

[Dooie Pop Pop]

luckily a new dawn is breaking.... the days of grease monkey mechanicals is finally coming to an end and the electronics boys are taking over. In the past, most good mechies have been treated like gods in the tuning industry, but not for much longer. For a long time us electronic gimps have just been faceless nerds, forced to suffer ridicule at the hands of our mechanical betters, our day is coming !!! <manic world dominating chuckle>

Seriously though, if they ever come up with some electronic method for speed control, I _guarantee_ it will get hacked and disabled. And there are a damn site more electronic engineers out there than mechanics who would love to get there heads round this sort of system....

I personally can't wait until all cars are run on electric fuel cells and all the theiving rip-off mechanical tuners are out of a job...

 

[Dooie Pop Pop]

luckily a new dawn is breaking.... the days of grease monkey mechanicals is finally coming to an end and the electronics boys are taking over. In the past, most good mechies have been treated like gods in the tuning industry, but not for much longer. For a long time us electronic gimps have just been faceless nerds, forced to suffer ridicule at the hands of our mechanical betters, our day is coming !!! <manic world dominating chuckle>

Seriously though, if they ever come up with some electronic method for speed control, I _guarantee_ it will get hacked and disabled. And there are a damn site more electronic engineers out there than mechanics who would love to get there heads round this sort of system....

I personally can't wait until all cars are run on electric fuel cells and all the theiving rip-off mechanical tuners are out of a job...

YEAH