Sensitive Brakes?

[Sharkie]

Also impressive to see a SUV that weighs 1600-1700kgs in sixth place!!

RAV4 V6 (1665kg) weighs the same as the Tiguan, and it came 3rd ..... point to note is that the RAV V6 runs 225s not 215s like the diesel Tig. Even 1 size wider is sufficient to substantially improve braking .... and RAVs come standard only with Bridgestones unlike VW who can fit a host of different brands (the cheapest tenderer wins).

Size and quality of your tyre has a significant impact on braking performance .....

[Maverick]

RAV4 V6 (1665kg) weighs the same as the Tiguan, and it came 3rd ..... point to note is that the RAV V6 runs 225s not 215s like the diesel Tig. Even 1 size wider is sufficient to substantially improve braking .... and RAVs come standard only with Bridgestones unlike VW who can fit a host of different brands (the cheapest tenderer wins).

Wider rubber doesn't always mean more grip for either acceleration or braking, there's a point at which wider becomes detrimental and it comes down to the quality of the tyre.

VW fit quite expensive high performance tyres to many models (like the CSC2's to the GTI and the SportMAXX to the R32) and I doubt that they're going to approve tyres for fitment to models at the factory based purely on price.

Car Bibles : The Wheel and Tyre Bible


If there's one question guaranteed to promote argument and counter argument, it's this : do wide tyres give me better grip?
Fat tyres look good. In fact they look stonkingly good. In the dry they are mercilessly full of grip. In the wet, you might want to make sure your insurance is paid up, especially if you're in a rear-wheel-drive car. Contrary to what you might think (and to what I used to think), bigger contact patch does not necessarily mean increased grip. Better yet, fatter tyres do not mean bigger contact patch. Confused? Check it out:

Pressure=weight/area.

That's about as simple a physics equation as you can get. For the general case of most car tyres travelling on a road, it works pretty well. Let me explain. Let's say you've got some regular tyres, as supplied with your car. They're inflated to 30psi and your car weighs 1500Kg. Roughly speaking, each tyre is taking about a quarter of your car's weight - in this case 375Kg. In metric, 30psi is about 2.11Kg/cm².
By that formula, the area of your contact patch is going to be roughly 375 / 2.11 = 177.7cm² (weight divided by pressure)
Let's say your standard tyres are 185/65R14 - a good middle-ground, factory-fit tyre. That means the tread width is 18.5cm side to side. So your contact patch with all these variables is going to be about 177.7cm² / 18.5, which is 9.8cm. Your contact patch is a rectangle 18.5cm across the width of the tyre by 9.8cm front-to-back where it sits 'flat' on the road.
Still with me? Great. You've taken your car to the tyre dealer and with the help of my tyre calculator, figured out that you can get some swanky 225/50R15 tyres. You polish up the 15inch rims, get the tyres fitted and drive off. Let's look at the equation again. The weight of your car bearing down on the wheels hasn't changed. The PSI in the tyres is going to be about the same. If those two variables haven't changed, then your contact patch is still going to be the same : 177.7cm²
However you now have wider tyres - the tread width is now 22.5cm instead of 18.5cm. The same contact patch but with wider tyres means a narrower contact area front-to-back. In this example, it becomes 177.7cm² / 22.5, which is 7.8cm.



Imagine driving on to a glass road and looking up underneath your tyres. This is the example contact patch (in red) for the situation I explained above. The narrower tyre has a longer, thinner contact patch. The fatter tyre has a shorter, wider contact patch, but the area is the same on both. And there is your 'eureka' moment. Overall, the area of your contact patch has remained more or less the same. But by putting wider tyres on, the shape of the contact patch has changed. Actually, the contact patch is really a squashed oval rather than a rectangle, but for the sake of simplicity on this site, I've illustrated it as a rectangle - it makes the concept a little easier to understand. So has the penny dropped? I'll assume it has. So now you understand that it makes no difference to the contact patch, this leads us on nicely to the sticky topic of grip.
The area of the contact patch does not affect the actual grip of the tyre. The things that do affect grip are the coefficient of friction and the load on the tyre - tyre load sensitivity.

[Sharkie]

Wider rubber doesn't always mean more grip for either acceleration or braking, there's a point at which wider becomes detrimental and it comes down to the quality of the tyre.

VW fit quite expensive high performance tyres to many models (like the CSC2's to the GTI and the SportMAXX to the R32) and I doubt that they're going to approve tyres for fitment to models at the factory based purely on price.

But we are not talking about the GTI and R32s here, the Tiguans come with some really nasty cheap tyres in some cases. As VW themselves said to me "The factory puts on from whichever batch they have at the factory and use many brands and its down to price" I had Hankooks and whilst quite, they were pretty bad grip wise.

And quoting an American article whilst interesting serves little purpose. Sure quailty of the tyres is the most imortant thing out there, but how do you (or that article) explain that fitting the same brand and model of tyre in 2 different sizes improving grip dramatically?

I have done this (funnily enough on a RAV) and the difference between 215 Bridgestones and 235 Bridgestones with the same ratings (model, load, wear & grip etc) are quite dramatic when it comes to braking and cornering.....

[Transporter]

But we are not talking about the GTI and R32s here, the Tiguans come with some really nasty cheap tyres in some cases. As VW themselves said to me "The factory puts on from whichever batch they have at the factory and use many brands and its down to price" I had Hankooks and whilst quite, they were pretty bad grip wise.

And quoting an American article whilst interesting serves little purpose. Sure quailty of the tyres is the most imortant thing out there, but how do you (or that article) explain that fitting the same brand and model of tyre in 2 different sizes improving grip dramatically?
I have done this (funnily enough on a RAV) and the difference between 215 Bridgestones and 235 Bridgestones with the same ratings (model, load, wear & grip etc) are quite dramatic when it comes to braking and cornering.....

H/W ratio (height to width ratio), has a lot to do with how well your car will handle.
If you have the same rim diameter than lower H/W ratio tyre will have larger contact patch.

H/W ratio = H/Wx100
Lower is better for handling and will improve braking as well.

edit: the above applies to the same tyre brand, make, model, composition and is fitted to the same car and tested at the same time under the same conditions, the only difference would be H/W ratio of the tyre fitted.

[Sharkie]

H/W ratio (height to width ratio), has a lot to do with how well your car will handle.
If you have the same rim diameter than lower H/W ratio tyre will have larger contact patch.

H/W ratio = H/Wx100
Lower is better for handling and will improve braking as well.

Thanks, exactly what I meant but wasn't able to say as well ....

[logger]

I have to be very careful braking with my Tiguan, its a sensitive flower, pushing too hard on the brakes makes it stands on its nose at low speed.
Makes it difficult to do a sensible rolling to a halt stop.
Has my Tiguan got a bad caliper or something, or are all Tigs super sensitive?
I notice also when I brake hard from 100km/h, it initially brakes well, but then hits a wall if I brake harder - it seems all its braking performance is used up in the first 2cm of pedal travel

Sanman, I also find the brakes on my Golf to be too sensitive for my liking. But just in the last couple of kmh when coming to a stop and when starting off. Just means the actual stop can be somewhat of a bump at times. Also when releasing the brakes to get moving they seem to release near instantaneously causing a bit of a lurch. Rest of the speed range I don't mind. Seems they have designed it all to happen in a very short pedal travel and this does not suit all of us. Here's a description of the two-stage brake servo, which I suspect may play a part in this...

Brake Servo
The brake servo reduces the amount of pedal force the driver needs to apply when braking.
A two-stage brake servo with a highly sensitive response was developed for the Golf. Up to a brake pressure of about 45 bar, known as the comfort braking range, the braking force is boosted five-fold. If the driver presses the brake pedal more forcefully, the braking force is boosted by up to a factor of ten. The driver notices this by the fast braking response combined with a short pedal travel, a good progressive brake modulation and reduced braking effort up to the point at which the ABS is activated.

[Sanman]

Sanman, I also find the brakes on my Golf to be too sensitive for my liking. But just in the last couple of kmh when coming to a stop and when starting off.

This is what I object to mostly. To roll fwd and stop in traffic requires fine foot control. The pads tend to bind (or grab) rather than slide at 1-2km/h. As you release you get a low resonance sound (graunch) as the pad grab and release.

[clip]

well I just picked up my tig after having the new brake servo fitted and while I didn't think there was anything wrong with my brakes before, when I drove out of the dealer and then pulled up at the first set of lights and had to use the brakes, I nearly went thru the windscreen. So I'm thinking that I had a problem from the start and see what you guys are on about now.

[Pinarelloman]

After driving a 13 yr old Landcruiser for the last 5yrs and stepping in to the wifes Tig, the brakes nearly put me through the windscreen.
Very impressive brakes. Wish the Landcruiser stopped like that!

[Dartiguan]

35 years ago my CX2400 Citroen, which had a button for a brake on the floor used to confound other drivers because of its sensitivity. Once you got used to it though, the extra control and response it gave was a pleasure to drive with. The Tiguans brakes are good, and in the same league but no more exceptional than my last two Volvos. I would rather have that than underperforming brakes.

[Tigger]

So maybe I am just being difficult, but I have no idea what you guys are talking about re brake Exta sensitivity....

I have driven so many GTI's and R's and Tigauns now, and did not notice any excessive difference in the braking sensitivity. I did not feel that any of them were TOO grippy....just how they should be....you know 'brakes'....(they are there to stop you after all, and one needs to adjust to each car)

Perhaps driving seating position is a factor?. If sitting too close etc...the pressure applied may be inappropriate for the car...esp if it is the first time in that specific verhicle....

[zhenjie]

I felt the Golf R brakes way better at modulating then the Tiggy on/off brakes. I really do hate the sensitivity of my Tigs brakes also, actually my poor passengers probably hate it more

[NZTiguan]

I'm with Tigger on this one, my tiguan's brakes are FANTASTIC, yes they have a relatively short pedal travel but you should be able to get used to that very quickly. I love the fact that they're so progressive and don't need a heavy foot to control the brakes. Personally I feel a lot of modern drivers leave their braking much too late and as a consequence end up with jerky stop / start motoring. Late braking is fine on the track but does nobody any favours on the road. What zhenjie's passengers dislike is his driving !! nothing to do with the brakes.

[hippyhippy]

do your brakes have a little squeak just before they stop? are my pads out or something? i notice this little sqeak just right before i stop when i press the brakes, i dont think its normal. Its not a high pitch squeak but quite a lower noise squeak.

[NZTiguan]

do your brakes have a little squeak just before they stop? are my pads out or something? i notice this little sqeak just right before i stop when i press the brakes, i dont think its normal. Its not a high pitch squeak but quite a lower noise squeak.

Not that I've noticed but I'm always easing off the brakes as I come to a stop (unless downhill) so that when I stop I'm using the minimum amount of braking required to stay in the spot I want to. To me, if a passenger, or the driver for that matter, rocks back and forth as I stop then I've made a poor job of it. Not sure what the noise you're getting could be, my only suggestion would be that you try braking differently (harder / softer / whatever) and see if that changes anything. If not then maybe it needs a quick look, I can remember many years back when I had a slightly loose "backing plate" (think that's what it was called) and it used to "clunk" when you stopped in reverse and started forward.

Cheers