Speedo calibration for bigger tires!
 

Thought I'd just share the following link which I just stumbled upon...

Universal Speedometer Signal Interface

It's not especially cheap - and even worse for me to pay both shipping to the UK and duty when it arrives - but it is something that would make me much more likely to consider fitting bigger tires for FE purposes!

But then - maybe this can be corrected from within VCDS/VagCom for us VW diesel owners???

Here is a free option... Tire Size Calculator - Compare Tire Sizes

Yup - there are plenty of tire size calculators around - but I am a driving instructor. I need to have my pupils comply with the law - especially when they are taking their driving test in my car!

My little automatic has desperately 'short' gears, and it would be great to fit bigger tires... but I need an accurate speedo. As it happens, my automatic has an old fashioned ( non electronic ) speedo, so it would be a matter of making measurements and then having the speedo re-calibrated by a company that does such work.

But a gadget such as is available from the link, would allow you to try different size tires, and correct the speedo calibration yourself, when ever you want... Very handy!

... Or if you're handy with a soldering iron, you could try this.

Speedo Corrector MkII Kit "Kit Back Catalogue" - Jaycar Electronics

Back in the late 1990's, Andy Granatelli (of Studebaker and STP fame) sold something similar for GM cars, an "electronic" speedometer corrector module that plugged 'in-line' between the OEM sensor and the dashboard/ECM.

My Hypertech programmer I bought for my 2003 S-10 truck has a speed calibrator built in, I would say you could find something similar

I think it can be fairly easily achieved with Arduino or any other microcontroller. First you have to get the pulses from VSS then calculate pulses that you need for your speedo and just generate output pulses accordingly to the pulses from VSS.

Cool!

Does anyone know of something like that can change tire size inputs for an electronic control brake module? These types of things always seem to have some disclaimer like on their site:
"If your vehicle is equipped with an anti-lock braking system (ABS), it is generally advised to ensure the signal reaching the ABS controller is not altered to eliminate any potential problems affecting control algorithms within the system."

Dealers want an arm and a leg to do a simple ECBM tire size edit :mad:

I don't think that difference up to 10-15% in tire size will alter ABS functionality. My friend changed tyres in his SUV from 27 to 33" and ABS still works perfectly.