Characteristic or fault?

[XK140]

I'm just getting used to my RC F and I find that when braking to a stop,if the road surface is uneven,the car tends to "tramline",i.e pulls one way or another before it comes to a halt.

When braking from speed all seems normal.

Is this because of how the geometry of the front suspension is set up? I also notice some Ackerman effect that is skipping of the front wheels at slow speeds on full lock,again normal?

I've got the car booked in for a front alignment check which should correct the steering wheel being slighlty (very slightly) off centre,we'll see if it shows up anything else.

Also,I'm perhaps thinking it might have been best to go for a 4 wheel Hunter machine check.

The tyres have plenty of tread and are evenly worn,they are all Potenza re050a....perhaps not the best.

Any thoughts,please?

[V8ORBUST]

10 minutes ago, XK140 said:

I'm just getting used to my RC F and I find that when braking to a stop,if the road surface is uneven,the car tends to "tramline",i.e pulls one way or another before it comes to a halt.

When braking from speed all seems normal.

Is this because of how the geometry of the front suspension is set up? I also notice some Ackerman effect that is skipping of the front wheels at slow speeds on full lock,again normal?

I've got the car booked in for a front alignment check which should correct the steering wheel being slighlty (very slightly) off centre,we'll see if it shows up anything else.

Also,I'm perhaps thinking it might have been best to go for a 4 wheel Hunter machine check.

The tyres have plenty of tread and are evenly worn,they are all Potenza re050a....perhaps not the best.

Any thoughts,please?

I must admit I've personally not had the front tyres skip on full lock. I'm very familiar with this too as my Alfa was a pain with it.

I'm running pilot sport 4's.

[Silkmen]

I have very minimal tyre skip with MPS4's, only happens when the temperature drops into single digits. I've found the tyres are very pressure sensitive and running them anything below 36psi casues the tyres to feel like they have flat spots and can tramline. 

Had my balance and geo checked recently and everything is ok. Keep the Michelin's at 36psi and they are great👍 Maybe the same with the Potenza's?

[XK140]

11 minutes ago, Silkmen said:

I have very minimal tyre skip with MPS4's, only happens when the temperature drops into single digits. I've found the tyres are very pressure sensitive and running them anything below 36psi casues the tyres to feel like they have flat spots and can tramline. 

Had my balance and geo checked recently and everything is ok. Keep the Michelin's at 36psi and they are great👍 Maybe the same with the Potenza's?

Good point about tyre pressures,I think they are are about 33/34 cold at the moment...I’ll try some more air!

[scott-o]

The tyre skipping thing sometimes happens on my ISF at very low speed/ plenty of lock scenarios. I did a bit of googling and seems common practice. I was surprised at how much lock the car has to be honest.

Funny you mention Ackerman, interesting reading if you're a nerd (i've been reading into it on and off for awhile now as was considering trying a rack and pinion system on my old bmw!)

[Linas.P]

14 hours ago, XK140 said:

I'm just getting used to my RC F and I find that when braking to a stop,if the road surface is uneven,the car tends to "tramline",i.e pulls one way or another before it comes to a halt.

When braking from speed all seems normal.

Is this because of how the geometry of the front suspension is set up? I also notice some Ackerman effect that is skipping of the front wheels at slow speeds on full lock,again normal?

I've got the car booked in for a front alignment check which should correct the steering wheel being slighlty (very slightly) off centre,we'll see if it shows up anything else.

Also,I'm perhaps thinking it might have been best to go for a 4 wheel Hunter machine check.

The tyres have plenty of tread and are evenly worn,they are all Potenza re050a....perhaps not the best.

Any thoughts,please?

Sounds to me like generic wheel alignment issue and not RC-F specific. The tyres you have are not bad for UHP summer tyre, dry/hot roads or even occasional track use (could be considered "budget track tyre"), but they are not great tyres for - fuel economy, comfort and in my experience all Brigdestones I had tended to tramline more than I felt was necessary (although my experience were more Potenzas 001s and Turanzas, not specifically Potenzas re050a, which is more of sport/track oriented).

[Twellsie]

maybe a silly question but do you have the same tyres on the back as the front?

Also another one for tyre pressure, i set mine with a temp gun to make sure i am getting equal heat across the width, 2.9 bar front, 2.8 bar rear, may be slightly different on a RCF but should be close enough as a starting point

[XK140]

11 minutes ago, Twellsie said:

maybe a silly question but do you have the same tyres on the back as the front?

Also another one for tyre pressure, i set mine with a temp gun to make sure i am getting equal heat across the width, 2.9 bar front, 2.8 bar rear, may be slightly different on a RCF but should be close enough as a starting point

Potenzas all round.I’ve upped the pressures today and things seem better with just a quick drive round.

I’ll see if the tracking check finds anything.

[Silkmen]

Glad to hear upping the pressures seems to have helped.

[BillNick]

Do we have tyre pressure sensors?

[XK140]

22 minutes ago, BillNick said:

Do we have tyre pressure sensors?

Yes,set the pressures at 38psi on my gauge,the reading on the dash now shows 2.6 front and 2.7 rear cold.

Why the difference when I tried to set them the same all round I don’t know,human error I suppose.

If I was feeling rich I’d probably change the Potenzas since they only have a C wet rating and the fronts are getting old with a 2015 stamp on them....but they have plenty of tread left.

Also,the fronts have some superficial cracks in the tread grooves,which from what I’ve read is not a safety concern but a sign of ageing and reduced grip.

On balance, I do see a new pair of front tyres on the horizon.

[markeyszoo]

My 250 SEL sometimes does that.