All Season Tyre choice

Faults and Technical chat for the Jaguar F-Pace.
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Re: All Season Tyre choice

Post by 47jag » Sat Jan 05, 2019 9:13 am


It’s the Michelin Cross Climates that I have fitted. On the Pirelli’s I got a real big fright one morning. I had to turn right across traffic, I saw a gap and ‘went for it’. Instead of making the turn the car shot at a 45degree angle, leaping and howling until I backed off when it regained a bit of composure and made the turn. I still think there’s something wrong with the steering geometry as even on the Michelin’s I can still feel a ‘slipping’ sensation on lock. Not a lot but it’s there. It’s almost like the car can’t make up its mind if it wants to be FWD or RWD but a lot better than with the Pirelli’s.


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Re: All Season Tyre choice

Post by mik » Sat Jan 05, 2019 12:28 pm

I am NOT a tyre engineer. But I understand some of the complexities and theory. It's interesting stuff.

There is nothing "wrong" with the steering geometry. It has been designed in this way because that is what market research told Jaguar their customers wanted.

You've bought a Sports 4x4 (or whatever the market moniker is today).

F-Pace customers didn't want a Land Rover Defender, as they want something that looks better. But more importantly they want something that drives better on the road - where they will be 99.9999% of the time - and they want 4WD for extra security. They want the car to be safe and composed at 150+ mph. In fact they want it to handle predictably at 150+ mph and still provide plenty of steering feedack.

They want it to be a big comfy compliant-riding family carrier at one point, and act like a "sports car" when the family and dogs have been kicked out and Dad/Mum is going on a solo drive along their favourite piece of twisty tarmac.

Which is why they spent so much time at the Nurburgring fine tuning things. (Like most other manufacturers). The F-Pace buyer demographic wants a large comfortable 4x4 family super-sports car.

This is all well and good, but gives the designers some headaches, and compromises have to be made somewhere. One of those is in the steering geometry.

The F-Pace is my wife's car (and the family car). It is a superb piece of kit.

My car is a Lotus. If you get upset at the low-speed steering scrub on your F-Pace, you would be very very angy indeed at the low-speed steering scrub on my car. :evil: You'd be apoplectic as it is terrible. Particularly in reverse. The front tyres chung-chung-chung as you go anywhere near full lock in reverse. It is not pleasant, but it does this for a reason.

And that reason is that the Lotus chose to set the car up with "Anti-Ackerman" steering geometry. Essentially (and very simplistically) the engineers / marketeers have placed high-speed handling / grip / feedback very high up the priority list. They've accepted that this will bring compromises at manouvering speeds.... can't have your cake and eat it mate.

The F-Pace isn't as extreme, but to get all the traits listed above for the F-Pace buyer demographic, they have clearly set the car up with the ackerman steering angles biased towards high-speed capability.

If you are interested in the topic, you might want to watch a couple of videos. Boring techy vids, possibly a bit too long for your needs, annoying Aussie accent (sorry Aussies ;) ) but hey... You need to watch them in order as the second vid assumes you understand the theories covered in the first.

Tyres and Slip Angles

Ackerman Steering (Pro and Anti)

Speaking about the 22" wheels (as that's what we have on ours) - the Pirelli P-Zero's are clearly a performance-biased summer tyre. They have been chosen to provide the high levels of grip, and immediacy of response that the F-Pace demographic want. Comfort/compliancy is compromised in favour of these factors. Because that is a compromise the F-Pace demographic are prepared to make. The rubber compound has been selected to optimise their performance capability - so they don't overheat when you find yourself on a clear 10-mile stretch of deserted tarmac when out for a summer run in the Highlands of Scotland. That was a nice run....

Unfortunately this means they don't work well at low temperatures. The compound is hard and unyielding as you get down towards 5DegC so it struggles to key into the surface of the road, and the sidewalls don't flex as they would in warmer weather when you apply steering loads / slip angles to the tyre.

On a hot summer day you can reverse on full lock and feel a little squirm from the wheel.

On a cold winter day you reverse on full lock and get some skipping from the tyres - they cannot follow the slip angles the steering geometry is requesting.

Stick a set of cross-climate tyres on. Hey presto - much reduced low-temperature skipping.

We just fitted Vredstein WintracS tyres to our F-Pace. Immediately all low-temperature skipping was completely banished. You don't even feel any "struggle" from the steering rim. These tyres remain sufficiently compliant of sidewall and adequately keyed into the road surface that this trait does not appear.

People increasingly want everything without compromise. Fast but frugal. Comfortable yet agile. Luxurious but cheap. Big but light. Tyres that perform well in hot and cold, in dry and wet conditions, on tarmac and snow and ice and mud, and sand. Car designers these days pull off some pretty impressive magic tricks, but as the great Scotty (allegedly) stated - you cannae change the laws o physics. :)
2017 F-Pace 3.0D S for her
2014 Lotus Evora S SportsRacer for him

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Re: All Season Tyre choice

Post by Smitten » Sun Jan 06, 2019 8:22 am

Very informative post and couldn't agree more. I must be bang in the middle of the demographic described!!!!
3.0d S, Santorini black, black pack, 22" black rims, LEDs, Priv, 350W, ICTP, Ebony interior, AdSR, space saver, config ambient, remote release, lumbar, winter pack, rear recline. Build date Friday 13/4/18 :D

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Re: All Season Tyre choice

Post by catwoman » Sun Jan 06, 2019 1:20 pm

Yep, good post mik :)
mik wrote:
Sat Jan 05, 2019 12:28 pm
I am NOT a tyre engineer.
. . . be interesting to see what it might have been like if you were a tyre engineer! ;)
8-) . . been enjoying since July '16, 2.0d R-Sport, Ammonite + Black Pack, Jet/Red interior and a few useful options

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Re: All Season Tyre choice

Post by Jim » Sun Jan 06, 2019 2:23 pm

+1, very informative post mik.
Ex 2016, MY17 - 2.0 D, Portfolio - Dec 2018 RR Velar D300 HSE R-Dynamic

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Re: All Season Tyre choice

Post by pgk » Tue Jan 08, 2019 12:22 pm

In preparation for trip to Alps over Christmas, looked at all the advice and decided on the All Season single set rather than the double of Winter and Summer - Sorry Arianne, but here in the Thames Valley, snow and ice are still unusual!

Finally decided on the Vredestein Quatrac 5 all season tyres, which took about a week to come in to local dealer from Holland(?). Immediately impressed by how much quieter they were than the P Zeros; and no low speed problems in the cold.

Advised that the minimum lead time for a replacement would be 48 hours, I took one of the old tyres home (still a few thousand miles in them) in case of a puncture, rather than buy a brand new temporary one. About 24 hours prior to leaving for the ferry, drove out and as soon as ICTP woke up it told me there was only 2psi in front near. Luckily, the location of the Phillips screw buried in it, allowed it to be repaired so I departed with a full set of matching tyres!

The alpine resort was c 2000m high, and the road changed to partially covered in snow from about 1300m on way up - clear on way down. No issues with grip. The lack of Armco barrier when you cant see over the edge of these climbs never ceases to unnerve me, so I am always happy to let the faster drivers past when convenient, so I was not pushing the limits of the tyres! (The climb out of valley was about 14 miles, and sat nav estimated about 50')

So, very happy with my choice.

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Re: All Season Tyre choice

Post by Wookiee » Wed Jan 09, 2019 1:47 pm

mik wrote:
Sat Jan 05, 2019 12:28 pm
What he said. ^^^
2018 Portfolio 25T; Firenze Red; ICTP 380; sliding pano roof; cold-climate pack; configurable dynamics; BSM; 20-way seats; privacy glass; adaptive dynamics; configurable mood lighting; spacesaver; cooled glovebox; reclining rear seats

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