Simon's new Xantia V6 and Leaf blog

[myglaren]

Would it be worth contacting Vredestein and asking for advice?

[daviemck2006]

I ran the vreds on the 107 5 psi more than the falkens that were on before. I think could even have been more, they were worn more on both shoulders when removed. I would try increasing the pressures a bit and see how they feel.

[elma]

Out of interest what's the load rating on them and on the OEM one's?

[Mandrake]

Out of interest what's the load rating on them and on the OEM one's?

The factory spec for the rear tyres is 175/55 R15 77V and the Vredestein's are 175/55 R15 77T. So a lower speed rating (but still well in excess of the top speed of the car, by nearly 40mph) but the same load rating.

I've increased the pressure from 36 to 40psi and will see how that feels to drive tomorrow. The sidewalls feel significantly firmer to a thumb press at the higher pressure.

A lot of i-Miev/C-Zero/Ion hypermilers run even their standard summer tyres between 40 and 46psi to reduce rolling resistance as much as possible to eek out every possible mile of range, personally I think 46psi is probably way too high from a wet grip and handling perspective but I think 40 will probably be OK, especially with a tyre that is softer than standard. And it may pay to let them back down to 36 again when the snow and ice does arrive for better traction...

[elma]

Thats interesting.
I put equally load rated winter tyres on a Xantia but went from h or v (don't remember) to t speed rating and found them to be a little wobblier than expected.
I wondered if it were just a brand thing but now the same has happened with yours I guess not.

[white exec]

At those high pressures, are you getting anywhere near the maximum pressure marked on the tyre?
Is ride comfort sacrificed? On XM/Xantia, those pressures would be intolerable, as the tyres provide the first line of bump absorption.

[Mandrake]

At those high pressures, are you getting anywhere near the maximum pressure marked on the tyre?
Is ride comfort sacrificed? On XM/Xantia, those pressures would be intolerable, as the tyres provide the first line of bump absorption.

Maximum tyre pressure marked on the tyre is 51psi, so at 40psi I'm well within it's limit.

As far as ride comfort goes, the Ion is already a fairly firm, stiffly suspended car, I wouldn't say its harsh, but its definitely quite firm.

When the suspension/damping is stiff you can't really have a soft under-inflated tyre because all that happens is the un-damped spring formed by the tyre sidewall allows the car to bounce up and down on the tyre without any real damping, because the suspension is too stiff to actually move during these tyre oscillations and thus the shock absorbers can't help to damp the tyre sidewall oscillation. The rear was definitely bouncing on the tyres a bit whenever I was hitting a bump.

If the suspension was a lot softer it would move when the tyre oscillates and therefore be able to absorb the tyre oscillation, so you can have softer tyres with soft suspension. But on a stiffly suspended car you need fairly stiff tyres as well so that any bumps are absorbed by the suspension moving and not primarily by the tyre flexing, then the shock absorber can act to damp the suspension oscillation and keep the car stable.

In any case I drove it to work with 40psi at the rear this morning and it feels MUCH better. Naturally it feels firmer but no firmer than it was with the original tyres, in fact the rear tyres at 40 are matching the characteristics of the front summer tyres at 36 quite closely. The rear is not bouncing anymore and feels much taughter and more stable. Not "wobbly" like before. Cornering and acceleration responsiveness seems a bit improved and grip in the wet still seems good so I'm going to stick with 40psi for now, and probably up the fronts to 40psi as well when Vredesteins are fitted there as well.

I was thinking about tyre pressures last night and they're a lot more complicated that it seems on the surface - I remember when I upgraded my NZ Xantia from 185/65/15 to 205/60/15 years ago that was unsure whether I should be reducing, increasing or keeping the tyre pressure the same.

One school of thought that many subscribe to is that tyre pressure should be proportional to the weight of the car and inversely proportional to the contact patch size of the tyre - that school of thought would say that a wider than standard tyre should be set to a lower pressure, but I didn't find that to be the case in practice - I actually found I ended up running the same pressure as original after experimenting with higher and lower.

Swapping between a hard and a soft tyre shows that its not just the air pressure supporting the car and dictating the contact patch size - a lot of the support comes from the structure of the tyre sidewall and tread itself and the air only "helps" support the weight. So on the summer tyre where the sidewalls are stiffer you don't need as much air pressure to achieve a certain tyre shape and contact patch - put a similar sized winter tyre on with a softer sidewall and now you need higher air pressure to achieve the same overall tyre shape and contact patch deformation because less of the weight is supported directly by the sidewall's own strength.

Another proof that the tyre wall stiffness itself supports a lot of the weight and the air only supplements it is that if it was entirely supported by air pressure (say a thin walled inner-tube with no plys etc) and you doubled the weight on the rear of a car from 500Kg to 1000Kg by loading it up, you'd have to double the pressure in the tyre from 30 to 60psi to maintain the same tyre shape and contact patch size. But in a real tyre you might only increase it from say 30 to 35psi when you double the load on the tyre to achieve the same shape. So most of the weight is carried by the strength of the sidewall and only a small proportion by the air.

So it would seem of all the factors - load, tyre size, and tyre material that the material the tyre is made out of is a large factor in determining what the pressure should be, along with the load on the tyre, and that tyre size doesn't have a lot to do with it. (Also interesting to note that they specify 36 psi for both the 175/55 R15 on the rear and the 145/65 R15 on the front - two very different width tyres)

[elma]

I'd add to that that I've usually found a reduction in profile requires a reduction in pressure. Your ions tyres being 36psi front and rear makes more sense then.

[Mandrake]

I'd add to that that I've usually found a reduction in profile requires a reduction in pressure. Your ions tyres being 36psi front and rear makes more sense then.

Don't confuse tyre profile with sidewall height... the rear tyres are "lower profile" but because they are wider as well the sidewall height from ground to rim is almost identical. They're the same just wider. Profile is the aspect ratio of how much of the circumference from bead to bead is in the sidewall and how much is in the tread.

Tonight on the way home the rain was fair pelting down and there was a lot of standing water on the road, but the tyres performed admirably, had plenty of grip and felt really good.

I tried a few times to get the back to slide out by flooring it on slow tight bends and while it did scrabble slightly a couple of times it held on well and never let go, and didn't slide right out in dangerous oversteer like it did when the tyres first went on and weren't gripping well. It was gripping really well even in deep standing water at the higher pressure so increasing the pressure doesn't seem to have hurt wet grip at all, if anything it feels a bit better.

The ride is now free of bounce at the rear - firm but well controlled and bounce free and it feels nice and stable around the corners as well. In short, a combination of 200 miles of "wearing in" and an increase in pressure have taken the new tyres from feeling decidedly dodgy and mushy to really excellent. I'm really happy with how they're performing now.

When (if ??) the snow and ice arrives, I'll compare their performance on slippery surfaces at 40psi and 36psi - I suspect they'll grip on ice better at 36psi, while they definitely feel better at 40psi in the warm weather so I may end up using different pressures in summer and winter.

[Skull]

Starting to look for a second hand small electric vehicle .. yours is starting to look like a bargain Simon £4,150 if I've read the blog right (Page 72).

This is too pricey but maybe as more people start to show an interest the prices on the second hand market will rise

2012 Ion 13K £6,750

[Mandrake]

That listing recently appeared in the discussion over at speakev and there were a few people expressing some concerns about the listing, including that the traction battery was supposedly replaced. Something doesn't quite smell right about that one and the price is a bit high. It's probably worth around £5000-£5500 at that age and mileage from what I've seen.

If it genuinely has had the traction battery replaced at such a low mileage (and under warranty) then I would hope the battery is in almost new condition. BTW the listing says 2012.

Yes mine was on sale for £4200 at 28k miles and 5 1/2 years old - but I got £50 knocked off because the radio had lost its coding and thus wasn't working - but I ended up being able to code the radio myself for free using Diagbox/Lexia. Mine has quite a few small marks and scratches on the outside noticeable up close but not from further away, and some wear to the inner door liners, carpet and seats - it's an ex council car and it does look that way when you look at it closely, but none of the cars I've ever owned have been pristine! It does the job though, it gets us to work and back each day and runs nearly all our errands for pennies. It's also quite fun to drive even though it isn't powerful and isn't a cornering machine. It's quiet, smooth (the motor, not the ride!) and nippy to drive, and has quirky looks.

[Skull]

Cheers Simon (corrected error)

Looks like another forum to join.

[Mandrake]

I keep meaning to work out the equivalent MPG (MPGe) that I'm getting with the Ion, so sat down and worked out some numbers.

There are two figures you can calculate - one is MPGe which is a comparison based on the amount of energy in fuel, in my example petrol, converted from MJ to kWh. The other is a price comparison which also factors in the relative costs of electricity and petrol per MJ or kWh.

With "normal" driving in my Ion that includes some heater use I am averaging about 4 miles / kWh measured at the wall when recharging. (This includes all battery and charging losses etc) If I thrash it or use loads of heater I can get it down to about 3.3 miles/kWh, while if I avoid the heater and drive like Ms Daisy I can manage 4.9 miles / kWh. Day after day on my daily commute to work I'm averaging 4 - 4.2 miles/kWh so for summer at least I think 4 is a good average figure which I will use in the following calculations.

Depending on the grade of petrol there is about 34.2MJ or 9.5kWh of energy in 1 litre of petrol:

https://en.wikipedia.org/wiki/Energy_de ... _materials

Lets take a journey of 60 miles, which is the range of the car. 60/4 = 15kWh required to make that journey. 15kWh/9.5kWh = the energy contained in 1.58 litres of petrol.

1.58 litres is 0.348 UK gallons, so if I am achieving 60 miles using the equivalent energy of 0.348 gallons of petrol I get 172.4MPGe Or roughly 8.7 times better than my 20MPG Xantia V6.

It's pretty clear that no Petrol or Diesel car will ever achieve anything like this - its about 3x better than the most efficient Diesel you can buy today. Also the ageing Ion is only middling to good as EV's go in terms of miles/kWh, partly due to poor aerodynamics at high speeds and older battery technology - it's a lot more efficient than a great big lumbering Tesla Model S, (which is twice as heavy...) approximately on a par or maybe slightly more efficient than a Leaf, (as long as you don't use the heater, as it doesn't have a heat pump...) but not as efficient by quite a bit as the current EV efficiency leader, the Hyundai Ioniq.

This is an indication of the relative energy consumption per mile, but what about cost per mile, factoring in the cost of both electricity and petrol ?

For this I'm going to use the UK's current average price of 95 unleaded, which is 119.3p/litre, (even though my Xantia V6 requires Premium which is about 5p more) and my own electricity tariff with Bulb which is 12.3p/kWh.

60 miles = 15kWh, which at 12.3p/kWh is £1.845, £1.845 will buy you 1.55 litres of petrol, or 0.341 UK gallons.

60 miles from 0.341 gallons is 176MPG So this gives an indication of relative cost to my pocket per mile for petrol vs charging.

Interestingly, the price of electricity on my tariff, and the price of petrol are both almost equal at the moment in terms of energy content, which is why the two figures came out so close, something I wasn't expecting. But if I had been paying 6p/kWh the equivalent figure would have doubled again to a ridiculous 352MPG.

[CitroJim]

Gosh! Cheaper to run than a little moped and possibly - given how much I spend on bike fuel* - possibly cheaper than running a pushbike or even walking/running...

* Food in other words - I get through a lot of it, not that you'd know from looking at me

[Mandrake]

Gosh! Cheaper to run than a little moped and possibly - given how much I spend on bike fuel* - possibly cheaper than running a pushbike or even walking/running...

How many MPG does a moped get ?

Yes it is crazily cheap to run, at least for charging vs petrol. Of course there are still maintenance costs - insurance, tyres, brakes, etc...and of course VED is currently free. For the mileage I'm currently doing (about 12k a year) its looking like tyres will be the main thing it chews its way through and the major maintenance item.

The front brake calipers are rattling a bit - from a report over on speakev it sounds like the guide pins for the caliper can wear down on these and get a bit loose, I haven't even so much as had the front wheels off to inspect mine yet (too much else to do, no time to fiddle with something that is still working! ) and I suspect new guides could be quite expensive due to the rarity of the car. It also sounds like it might need a drop-link or two at the front (they are hilariously tiny in stature) but these kind of wear items are unavoidable on just about any car!

Of course the traction battery will eventually degrade to a point where the usable range becomes insufficient, but whether that will take 3-4 years (at 12k/year) or whether it may last 5-10 years is anybody's guess! It's all a bit of an experiment and I'm taking an "informed" punt on it to see how well it lasts.

I'm hoping to get 4 years / 48k miles out of it with negligible loss. The battery is currently at a State of Health of 85.9% of original new capacity, and in the time I have had the car it has lost 0.8% over 4346 miles. (up to the last time I checked the battery) It's too small a capacity loss to extrapolate too far from but it's well past the initial more rapid loss you get with a brand new battery so assuming the remaining loss is linear that is another 8% lost over the next 43,460 miles, or about 4 years at my current mileage. (By which time it will have done nearly 80k) I'll be happy if it manages that, especially for such "old tech" batteries relative to modern EV's.