Tyre Pressures

[Mick F]

Hi,
I see ratio is height 50% on your 16" tyres.
What the comfort like?
All these suv's with low profile tyres............ours feels like a go cart.......rock hard suspension.......but I like it like that

Is that 2 miles on battery? The battery weighs 1/4" of a ton? Or is that another model...................

Comfort is fine.
Given the choice, I wouldn't have 50% tyres coz they are more expensive. The four Kumhos we bought last month cost £288 - £72 each. Had we bought the original spec Conti Ecocontacts, they would have been £110odd each!

Yes, two miles at a constant speed on battery, but you can't do it unless you run out of petrol because the computer system won't allow you to get a flat traction battery so it starts up the engine and that joins in with moving the car along whilst topping up the battery.

When you reverse, you are only running on battery because there isn't a gearbox. The traction motor has the phases reversed so it turns backwards. The engine cannot help ....... but it would start up to keep the traction battery charged.

What about in the hot weather though, what happens to tyre pressures then? Oh and what's happening with Mick F's old tyres in his back garden? Have the neighbours complained yet?

Yes, hot weather versus cold weather alters the pressure. You're supposed to check the pressures "cold" but there's no definition of "cold".

The tyres remained with us for some months. Can't remember how many we had. A dozen or even 15 perhaps, could have been more.
The idea never got off the ground, so they went to the recycling place in Tavistock. I took them there only one at a time when we took other stuff as they won't accept a trailer load of them at once.

Back to the subject.
I wonder if car tyre pressures aren't that critical. Maybe they are for performance/racing use, but for the normal car on normal roads it doesn't matter much - hence the rather wooly instructions and figures.

I intend inflating to 3psi higher than what Toyota say, and see how it feels and how the tyres wear.

[Mick F]

Traction battery.
I took the rear seat out to have a look-see.

Silver lump is the traction battery.
You can also see the 12v battery too. This is an auxiliary battery to start the system and to allow lights/radio etc when the system is off. Also it locks and unlocks the car central locking of course. Without it, the car won't start up. The traction battery is charged by re-gen and/or the engine, and the traction battery charges the 12v battery.

No fan belts, no cam shaft (so no cam belts or chains) and no alternator.
Electric steering powered by the traction battery.
Electric air conditioning powered by the traction battery.
All electrics powered by the traction battery.
Heating powered by the engine water temp.

[NATURAL ANKLING]

Hi,
Is it petrol electric as in diesel electric transmission trains

Oh, over inflate a little as you will loose air so you will also spend half the time checking tyre pressures in future.

Brand name tyres will last twice as long in general.

Suck it and see, you will know whats right when the tyres wear, buy a tyre gauge - mechanical - fiver max, your got one any way.
Within 5 psi wont affect handling / safety for now.

[NATURAL ANKLING]

Hi,
https://www.economist.com/node/3422941

[Mick F]

Hi,
Is it petrol electric as in diesel electric transmission trains

I see you've sussed it!

The diagram is a little too simplified, but it illustrates the idea very well.
When you move away gently, the electric motor does the work. Engine only runs at this point to either keep you warm, or charge the battery, or both.

Pull away hard, and both the electric and the engine do the work.
The system is rated at 100bhp, but if you add the engine bhp to the electric bhp, you get 132bhp and a huge torque ........... it will give you this power for only a short burst to safeguard the whole system, so it evens out at 100bhp for prolonged power.

This means that the Yaris Hybrid will get away from the traffic lights faster than your average performance car, but 0 to 60 is like a normal hatchback. It's absolutely wonderful to floor the throttle to overtake. No slotting down to a lower gear, no kickdown and hesitation like an automatic. It just gives its all with a roar and no hesitation at all. it pulls away from rest immediately with no needing to rev the engine and dropping the clutch. It just sprints away in electric and engine combined and as much power as it can give you.

If the engine is stopped when you need it, it is turned over by an electric motor which starts it up immediately. No starter motor to engage.
No camshaft - the valves are operated individually by electric/hydraulics and controlled by the computer.

Also, the engine isn't your average Otto Cycle four stroke. It's a simulated Atkinson Cycle engine which is more economical but has less of a bandwidth in rpm. Simulation is done by the valve timing.
https://en.wikipedia.org/wiki/Atkinson_cycle

[Mick F]

...... hot weather versus cold weather alters the pressure. You're supposed to check the pressures "cold" but there's no definition of "cold".

I popped into Halfords on Saturday and bought a digital tyre pressure gauge. £14.99

It's hot outside - 24degC - and I thought I'd connect up the pump and see what the pressure reading was. I picked the front left.
Last time I checked it, it was 32psi like I'd set it.

Today, in the heat, the pump says 35psi and the new digi pressure gauge says 36psi. The pump isn't very good IMHO, as I've had to repair it twice and if I leave the batteries in, they go flat.
This one:
http://www.halfords.com/workshop-tools/ ... l-footpump

The tube split so I fitted a new one.
The valve connector broke, so I fitted a spare Lezyne Air Chuck.
Also, the clip thingy on the bottom to hold the pump shut, has broken.

All in all, it was a bad buy, so I'm not convinced that the pressure gauge is accurate. I have better hopes for my new gauge.
It's similar this one but a cheaper model that only records PSI. They don't show one on their website:
http://www.halfords.com/workshop-tools/ ... sure-gauge

[Mick F]

Done the car tyres in the "cool" temp of 15degC with no sun and overcast skies. Pressures set using my Halfords gauge.
I put in 34f 32r ............ as opposed to Toyota's 32f 29r statement.
The Michelin foot pump read 1psi low.

I checked the space-saver tyre in the boot. On the side of the tyre, the writing says inflate to 60psi - but it was down to 40psi so got the foot pump connected and tried and tried and tried, but it was very hard work. Got my Lezyne track pump out instead, and although that was easier, it was still a bit of a job mainly to do with the volume of air as the pump does my bike tyres to 120psi with ease. 60psi indicated on the Lezyne dial agreed with my new Halfords gauge ......... so that was nice!
Michelin foot pump read 57psi.