Hardware update gained 15% range

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anorak
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Re: Hardware update gained 15% range

Post by anorak » Thu May 30, 2019 6:03 pm

Reddo wrote:
Thu May 30, 2019 2:25 pm
….Surely the biggest factor with larger wheels is likely to be that the 22s increase the ride height of the vehicle relative to the 20s (BTW 255x50R20) would be identical in radius) a higher ride height would massively increase drag at motorway speeds.

Given that iPace generates all of its torque from zero revs would larger radius wheels increase acceleration? I am not sure how the physics work in the real world here, has anyone done some accurate experimentation?
The O.P. was switching from 22" to 18" wheels which have the same overall tyre diameter of 763mm and hence identical ride heights.

Also the 5mm difference in ride height (c. 3%) with the slightly smaller diameter 20" tyres wouldn't account for anything like a 15% difference in efficiency, if indeed that proves to be the case.

And larger overall diameter wheels would reduce the rate of acceleration compared to smaller ones, given the same applied torque.

You're right about the 255x50R20 tyres. I assume the 20" wheel width is better suited to the 245 section tyres?
I Pace EV400 S, Caesium blue, Oyster leather, 18" wheels
MY19, delivered 01/2019
IMC: S19B_19.40.4-436082 || Telematics: 17.2
Now on its 2nd front EPIC


Chewy
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Re: Hardware update gained 15% range

Post by Chewy » Thu May 30, 2019 8:07 pm

Reddo wrote:
Thu May 30, 2019 2:25 pm
Given that iPace generates all of its torque from zero revs would larger radius wheels increase acceleration? I am not sure how the physics work in the real world here, has anyone done some accurate experimentation?
Force at the road surface is what moves the car, not torque. Increasing the tyre diameter decreases the force generated between the tyre and the road, hence slowing the car acceleration.


FENorway
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Re: Hardware update gained 15% range

Post by FENorway » Thu May 30, 2019 8:26 pm

The optimal 20" tyres are 235/50r20.
1.They are lighter
2.They are narrower(drag)
3.They are available with rolling resistance label A from several brands, which is not the case with 245/50r20.
FE Corris grey light oyster/light oyster Performance 22" 5069 & 18" 1022 19B_19.40.4-436082 and 14.2


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anorak
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Re: Hardware update gained 15% range

Post by anorak » Thu May 30, 2019 8:59 pm

That size tyre would have a 20mm smaller diameter than the standard 18" or 22" ones though. Might start to actually look noticeably smaller on the car?
I Pace EV400 S, Caesium blue, Oyster leather, 18" wheels
MY19, delivered 01/2019
IMC: S19B_19.40.4-436082 || Telematics: 17.2
Now on its 2nd front EPIC


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Thincat
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Re: Hardware update gained 15% range

Post by Thincat » Fri May 31, 2019 10:17 am

sciencegeek wrote:
Thu May 30, 2019 3:34 pm
Reddo wrote:
Thu May 30, 2019 2:25 pm
This is a very interesting thread, I am mystified by that the suggestion that of mass being at a further out radius of the wheel is significant.
It may not be the only factor but it contributes a lot (most), I'm sure. People who ride bicycles have figured this out long ago. That's why there are tubeless tires and carbon rims now. I can tell you I feel the difference (and so does anyone who does performance-oriented riding) on a 29er mountain bike between tubeless (virtually no increase in tire mass) vs with inner tube, and same with aluminum vs carbon rims. Huge difference.
By "huge difference" do you mean lower rolling resistance and/or harder ride? For me, investing in 18" wheels to replace my 20" ones would be because I was looking for a significant range increase AND lighter steering AND softer ride, That sounds like a big ask but worth the cost if it delivers all of those things.
Cesium Blue HSE no sunroof, air suspension, HUD. Changed 20in wheels to 18in :D .


DougTheMac
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Re: Hardware update gained 15% range

Post by DougTheMac » Fri May 31, 2019 10:49 am

Thincat wrote:
Fri May 31, 2019 10:17 am

By "huge difference" do you mean lower rolling resistance and/or harder ride? For me, investing in 18" wheels to replace my 20" ones would be because I was looking for a significant range increase AND lighter steering AND softer ride, That sounds like a big ask but worth the cost if it delivers all of those things.
I’m thinking of doing the same thing. I’d add to the list a hope for less road noise.

Will I get all of these? Has anyone changed from 20” to 18” and noticed worthwhile improvements?
HSE Silicon Silver Pano Air+AD Oyster since 1Mar19
S19B_19.40.4-436082 & anon


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anorak
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Re: Hardware update gained 15% range

Post by anorak » Fri May 31, 2019 1:43 pm

I'm thinking of doing the opposite - going from 18" to 20" wheels. For vanity reasons more than anything.

Would be happy to meet up with anyone potentially interested in a wheel swap / part exchange type of deal. Try before you buy, so to speak.....
I Pace EV400 S, Caesium blue, Oyster leather, 18" wheels
MY19, delivered 01/2019
IMC: S19B_19.40.4-436082 || Telematics: 17.2
Now on its 2nd front EPIC


Reddo
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Re: Hardware update gained 15% range

Post by Reddo » Sat Jun 01, 2019 9:47 am

My daily commute takes in equal measure terrible potholed single track roads (never gritted), A, B roads, dual carriage way and finally city roads. From my experience the biggest irritations with excessively low profile tyres are rim damage and the steering following imperfections on the road. The ipace has rims which are deliberately more narrow than is optimal for grip and that tradeoff should prevent the peril of curbs. Perceived harshness of ride is very personal and subjective, for me the 22s just look too big for the car and the 18s are a little too flabby for summer driving, looking into options for possibly 21s and keeping the 20s for my winter tyres.


FENorway
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Re: Hardware update gained 15% range

Post by FENorway » Sat Jun 01, 2019 10:13 am

@reddo. If you go for 21" you should choose the GY Eagle F1 Asymmetric 3 SUV 245/45r21. They have B in rolling resistance and only 68 dB in noise level. If you do some research and find some lightweight rims, it should be possible to have a consumption very similar to that you have with 20 inch. The standard 5070 FE wheels are BTW 29 kilos.
FE Corris grey light oyster/light oyster Performance 22" 5069 & 18" 1022 19B_19.40.4-436082 and 14.2


Reddo
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Re: Hardware update gained 15% range

Post by Reddo » Sat Jun 01, 2019 6:39 pm

Hey thanks - yes looking at putting the 245/45r21 on forged 8.5 x 21 rims, just hunting for some with an appropriate offset. Thanks for the info, most helpful.


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