Jolt when driving from cold, Rear axle/Diff

[ColinBarber]

2 hours ago, Anthony B said:

I admit I don't fully understand wha's going on but the idea  seems to fit the observed phenomenon better than other ideas.  But I've learned much from the posts in this series since the topic was first raised.

Low speed crabbing of the tyres is common on a lot of vehicles with low profile wide tyres when the steering is near full lock. Happened on my IS300h and my GS when reversing off my driveway during cold weather when the tyres don't have as much grip.

[Anthony B]

I admit that it may have nothing to do with the diff, which is balancing torque between the rear wheels as intended.  I think, as has been pointed out, it's down to my very hard rear tyres reacting, particularly when cold, to a sharp left or right turn.  I'm content not to lose any more sleep over the matter. Just for interest I may try the experiment of lowering the tyre pressure and seeing what effect that has.

[paulrnx]

7 minutes ago, Anthony B said:

I admit that it may have nothing to do with the diff, which is balancing torque between the rear wheels as intended.  I think, as has been pointed out, it's down to my very hard rear tyres reacting, particularly when cold, to a sharp left or right turn.  I'm content not to lose any more sleep over the matter. Just for interest I may try the experiment of lowering the tyre pressure and seeing what effect that has.

Hi. I wondered why you fitted runflats on your IS? I always though runflats needed a slightly different design of wheel that keeps the tyre on the rim if the tyre goes flat. Just curious that’s all.

[route66]

On 2/2/2021 at 2:33 PM, royoftherovers said:

OK Peter, if your happy, then so am  I !  Enjoy your car and stay safe and well.

Sounds like you should follow your own advice John and "digest the Handbook" ☺️

Starting off in Eco mode is perfectly fine. In fact, leaving the car in Eco mode for 100% of the time is also fine.

From said manual:

[matt8]

26 minutes ago, route66 said:

Sounds like you should follow your own advice John and "digest the Handbook" ☺️

Starting off in Eco mode is perfectly fine. In fact, leaving the car in Eco mode for 100% of the time is also fine.

From said manual:

Yes! And here's something that backs this up:

Using car in sport mode, turning the car off in this mode, then turning it back on next time I go out, I find I am reverted back to normal mode.

When using car in eco mode and turning the car off whilst set in this mode, the next time I come to use it, eco mode is preserved. It does not revert to normal.

Indeed, if starting the car in eco was not good for the car, it would not preserve it and instead revert to normal.

Using sport from the get go can't be bad for it, it's more just to preserve fuel and maximise efficiency as far as I understand.

[Brechin Slate]

On 02/02/2021 at 2:15 PM, royoftherovers said:

Why are you starting off cold in  Eco mode?

You need to digest the Handbook Anthony

What does the handbook say about this? Nothing in mine, I leave it it Eco mode most of the time.  Eco mode controls the rate of acceleration and limits the functionality of the A/C.  Nothing wrong with starting off from cold in Eco.  If quoting the handbook we need to be accurate?

[ColinBarber]

6 minutes ago, Brechin Slate said:

What does the handbook say about this? Nothing in mine, I leave it it Eco mode most of the time.  Eco mode controls the rate of acceleration and limits the functionality of the A/C.  Nothing wrong with starting off from cold in Eco.  If quoting the handbook we need to be accurate?

As you say the handbook states nothing about it because it is perfectly fine and the vehicle even remembers what mode you are in from last time. It there was an issue then the software wouldn't let you choose that mode - like it does when the ICE first starts up and states EV mode currently unavailable if you push the EV button.

[NemesisUK]

To be fair models do differ in this. My RC will always revert to Normal mode and will allow one to use EV mode when the ICE is cold, as long as one presses the buttonn before the ICE starts up (approx 10sec, up from 2-5sec in my 1st gen RC)

That all said there is no problem with selecting to ECO from cold equally no problem selecting Sport+ if desired. If there were the car wouldn't allow it!

[royoftherovers]

3 minutes ago, NemesisUK said:

To be fair models do differ in this. My RC will always revert to Normal mode and will allow one to use EV mode when the ICE is cold, as long as one presses the buttonn before the ICE starts up (approx 10sec, up from 2-5sec in my 1st gen RC)

That all said there is no problem with selecting to ECO from cold equally no problem selecting Sport+ if desired. If there were the car wouldn't allow it!

Sorry fellas, it was my mistake. I read EV for ECO. Apologies all round.

[Kermitpwee]

8 hours ago, ColinBarber said:

It can only really be diff/brakes/suspension at the rear. Are your rear brakes freeing correctly, especially the parking brake?

Being in Eco mode should have nothing to do with it, and it is a mode that is perfectly acceptable to be using from startup if you so wish.

Brakes are working perfectly and not sticking. I tried Normal mode this morning and it didn't happen, I will try different modes over the next week and report back

[Kermitpwee]

6 hours ago, Anthony B said:

I admit that it may have nothing to do with the diff, which is balancing torque between the rear wheels as intended.  I think, as has been pointed out, it's down to my very hard rear tyres reacting, particularly when cold, to a sharp left or right turn.  I'm content not to lose any more sleep over the matter. Just for interest I may try the experiment of lowering the tyre pressure and seeing what effect that has.

It's your front tyres that are causing your problem

[Kermitpwee]

In Normal mode its driving perfectly from cold, I will continue with this for the weekend, next week I will revert to Eco mode and report back with my findings, thanks again.

[Brechin Slate]

37 minutes ago, Kermitpwee said:

In Normal mode its driving perfectly from cold, I will continue with this for the weekend, next week I will revert to Eco mode and report back with my findings, thanks again.

Please also make a note of weather/ground conditions with each mode, it will be a factor.

[Kermitpwee]

8 hours ago, Brechin Slate said:

Please also make a note of weather/ground conditions with each mode, it will be a factor.

It's pretty steady conditions here for the next week so that should be good. 

The jolt happens in Eco mode everyday regardless of weather

[Kermitpwee]

Final report, it only happens in Eco, normal and sport mode it never happens. I'm quite happy with that