Has anyone ever tried to measure what deceleration they get from their tyres?

 

I bought Vredestein quatrac light all-season tyres about 1 month ago, due to some good reviews and needing to be able to get up narrow, steep roads in frosty weather. Having tried them for a bit I think they are not as grippy at maybe 10-15 C as the mix of continentals that were on previously. The traction control has lit up a few times when pulling out of junctions, and I think I'm getting more wheelspin.

 

So I've just tried using an Android app for measuring acceleration, running while I braked from 25 mph. I get about 0.5 g max, with the ABS kicking in, on a damp road.

 

Can anyone comment? Looking on the internet it seems 0.6 - 0.8 is typical for a wet road. I just wonder whether the tyres really are a bit iffy. I will try again on dry tarmac when I can find some. (Not sure how accurate the app is, but I've just tried dropping it onto a cushion and it shows about 1g which is right as the difference between normal gravity and free-fall)

 

I'd had Goodyear Vector 4 seasons on a previous car and they'd seemed ok in comparison with the super-cheap tyres before them.

Can't offer any comparison measurements but all tyres are a compromise, Summers work best above 12c Winters work best below 7c. All seasons can not be expected to perform as well as either of these in their ideal operating zones but offer a compromise between both, as such you have to accept that limitation and drive accordingly.

 

If you want the best performance under all conditions then be prepared to have at least 2 sets of wheels, summers and winters, and change them to suit your local conditions.  It does sound as though you really need winters to cope with narrow frosty roads.

Using a mobile phone App isn't very scientific is it?

Using a mobile phone App isn't very scientific is it?

Yes I'd also posted in "performance upgrades" asking about whether measurements based on gps, accelerometer or both are best, or a system linked to obd and gps. The obd system could be most accurate I guess as it can get speed from rpm, but the bluetooth interface is pricey. (I thought the performance upgrade people would be most interested in knowing how cars perform)

What's your thinking behind saying that the mobile app version isn't scientific? (I agree that it maybe doesn't sound promising, but then again sensors on modern phones might be good, so it'd be good to have data to make a judgement with)

What's your thinking behind saying that the mobile app version isn't scientific? (I agree that it maybe doesn't sound promising, but then again sensors on modern phones might be good, so it'd be good to have data to make a judgement with)

Because it's a phone, it's not a specially designed scientific instrument calibrated by a registered body.

Also I assume you're testing your tyres on exactly the same type of surface and same conditions as what you're comparing them to? Also you're a using the same car as the other tyres tested?

Because it's a phone, it's not a specially designed scientific instrument calibrated by a registered body.

Also I assume you're testing your tyres on exactly the same type of surface and same conditions as what you're comparing them to? Also you're a using the same car as the other tyres tested?

I'm just hoping to learn. Yes the road condition is variable: From your comment, can you say anything about how much effect the surface has? I found a paper from 2003 where the authors had tested on "dry" and "soapy pavement" and got mu as ~1 and 0.6 respectively   "Estimation of the Maximum Tire-Road Friction Coefficient" DOI: 10.1115/1.163677

 

I'm thinking that the phone (maybe surprisingly) might be as accurate as I can judge my position + speed before hitting brakes if I was to measure it by stopping distance instead. So maybe +/- 10% or something. Hopefully better than the 40% increase of 0.7 g over 0.5 g . (& on testing I found it repeatably measured <0.05 g when stationary and about 0.9 g in free fall. So maybe it under-reads by 10%).

 

As some Skoda peeps are into measuring what their cars can do (like the power and torque outputs etc.), and there are threads on brake replacements and vcds, I was hoping people might chip in with data. I'd like to find the typical range of values for dry / damp / wet etc., so i could tell whether mine was within those populations, within the limits of accuracy of the sensor.

 

If there was a simlpe, robust enough way to measure this it might be handy for people to tell if their tyres really are safe

I found Winter Vredestein Snowtracs and Extremes to be definitely better in cold wet conditions. not so sure if the temperature was higher, ie the warm 10-15 degree temps you mentioned. But I guess the tyres was designed to excel in winter temps. Mind you, in general warmer conditions, the winters were poorer in almost all situations compared to an all season/summer type tyre. :( 

The big (huge) problemin your equation is the variability in road surface.  100 metres away may be different, let alone 100 miles, given the state of our roads.

Applaud the sentiments, but don't see a real way round to achieve re-producible data, far too many variables.

One thing is for certain -- your stopping distance will be far, far better than the figures you are supposed to take note of as published in the Highway Code! Those figures must be donkey's years old, probably tested with a Ford Anglia on cross ply tyres and drum brakes all round!

 

Mike

Only partly true.  A large proportion of the stopping distance is the thinking distance, and they haven't improved the shaved monkey in the driver's seat recently.

Has anyone ever tried to measure what deceleration they get from their tyres?

I bought Vredestein quatrac light all-season tyres about 1 month ago, due to some good reviews and needing to be able to get up narrow, steep roads in frosty weather. Having tried them for a bit I think they are not as grippy at maybe 10-15 C as the mix of continentals that were on previously. The traction control has lit up a few times when pulling out of junctions, and I think I'm getting more wheelspin.

So I've just tried using an Android app for measuring acceleration, running while I braked from 25 mph. I get about 0.5 g max, with the ABS kicking in, on a damp road.

Can anyone comment? Looking on the internet it seems 0.6 - 0.8 is typical for a wet road. I just wonder whether the tyres really are a bit iffy. I will try again on dry tarmac when I can find some. (Not sure how accurate the app is, but I've just tried dropping it onto a cushion and it shows about 1g which is right as the difference between normal gravity and free-fall)

I'd had Goodyear Vector 4 seasons on a previous car and they'd seemed ok in comparison with the super-cheap tyres before them.

I use a decellerometer quite regularly at work to calculate the coefficient of friction between tyres and the road surface as it is needed to work out pre impact speeds in collisions.

A dry road would be roughly 0.7, a wet one 0.5-0.6 and an icy one as low as 0.1

One thing I can tell you is that whether it be a 44 tonne artic or a golf gti, the tyres all act pretty much the same at the point of ABS activation hence in a lorry crash a car can be used to carry out the skid tests.