larger tyres - difference in economy /acceleration?

Red XS

Red XS

Forum Member
Joined
Dec 6, 2013
Messages
908
Location
Perth, West Aus
Car Year
2006
Car Model
SG Forester XS
Transmission
1.447 Low SG Manual
I wouldn't touch Coopers either.

Now for a different question
Would there be much difference in power and fuel economy between 215/60R16, 215/65R16 and 235/60R16's? I was wondering how must the larger diameter will effect the power+economy and then how much more a wider tyre would add on top of that.
 
Larger diameter tyres make for taller gearing, which reduces acceleration. Wider tyres will add slight rolling resistance and wind resistance at speed.

From personal experience, I've gone from 215/60's to 215/65 and apart from the speedo being spot on instead of reading under and that the spare doesn't fit in the spare wheel well, I've noticed no real measurable difference.
 
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I haven't by going larger diameter. I think going a road going or all terrain tread pattern would make a larger difference to economy.
 
I have noted some differences. My XT has been fettled a bit and as such does not get the best fuel use but here

Standard 17in XT alloys with Standard tyres 400-420kms per tank (approx. 40-45ltrs) over 15,000kms

Standard GT 16in alloys with standard tyres 490-510kms per tank over 4000kms

Standard GT 16in alloys with BFG AT KO (215/70/16) 450-500km per tank over 5000kms

Lot more variation with the ATs, most likely as I am more likely to hit the longer dirt roads home. Slight reduction in 0-100 time but not overly noticeable.
 
I did, but i think that is more due to the A/T vs.s road tyre being a lot heavier and the ej20 being a little asthmatic at best.
 
Depends.... how big verse stocl? AT, Muddies or roadies?
Go 215/65r16 in an all terrain. Geo AT-S or 697 I'd recommend and call it a day. Since ypu like your car stock thats your best option.

when my forester was stock the first thing was to upgrade to 215/70r15 from the stock 205/70r15. I did notice it was marginally slower but after a day I was used to it. On the highway I returned better fuel economy and on one occasion managed to get from Geraldton to Perth on half a tank. Thats 450km distance!
 
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Going from stock to big dirty 215/70/16s with my 2.5L there was only a small drop in grunt. By far the biggest difference was the handling. It made the car feel like a big 4wd versus a road car.
 
I run 215/60/16 road tyres for everyday. For snow I run Yokohama ATS 215/60/16 and notice no difference in economy. Off road I run 215/65/16 Yokohama ATS 215/65/16. In Fifth gear I have slightly less power, apart from that no real issues. I have to say I prefer the ride quality with the 65 series and the 60 series just look too small!
 
215/65r16 vs 225/60r16 vs 235/60r16. So not that large, and in a H/T because they are better for sand IMO (but I know that's quite debatable). Also, won't be getting new tyres until these wear out, which will still be a while. Just having a think about it.

Would be great to see a forry with 31's, but not mine, maybe your auto GT :P
 
Red XS said:
215/65r16 vs 225/60r16 vs 235/60r16. So not that large, and in a H/T because they are better for sand IMO (but I know that's quite debatable). Also, won't be getting new tyres until these wear out, which will still be a while. Just having a think about it.

Would be great to see a forry with 31's, but not mine, maybe your auto GT :P
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235 60 16 equal to 215 70 16 so it is 2 size up from stock and the speedo would be out while the left 2 will give you dead on speedo.
 
tuckerbag said:
235 60 16 equal to 215 70 16 so it is 2 size up from stock and the speedo would be out while the left 2 will give you dead on speedo.
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I believe 235/60/16 is almost an inch smaller than 215/70/16.
235/60/16 according to my calculator is 27.1" vs 27.9".
They should be a good size imo that will put your speedo close to stock maybe a touch over and give you some good height and traction.
 
Fazed said:
Larger diameter tyres make for taller gearing, which reduces acceleration. Wider tyres will add slight rolling resistance and wind resistance at speed.

From personal experience, I've gone from 215/60's to 215/65 and apart from the speedo being spot on instead of reading under and that the spare doesn't fit in the spare wheel well, I've noticed no real measurable difference.
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Going to 215/65s I've noticed that i now have to drive up my parents road in 3rd as 4th doesn't have quite enough grunt at 50kph for that hill.
 
Davidov said:
I believe 235/60/16 is almost an inch smaller than 215/70/16.
235/60/16 according to my calculator is 27.1" vs 27.9".
They should be a good size imo that will put your speedo close to stock maybe a touch over and give you some good height and traction.
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Yes 235/60R16 pretty much bang on same diameter as a 215/65R16 at 27", which to my mind is the ideal rolling diameter.
 
Will 235s clear the strut though? IMO it would be pushing it, at least at the front. That's with my +48 Forester wheels though. There's a little over a centimetre with my 215s.
 
235/60R16 are only 2mm more diameter than the 215/60R16, so near enough the same.
And they'll be about 10mm wider on either side of the tyre. So how much more than 1cm clearance is there kiwi?
Another note, will my H/T's use slightly less room than A/T of the same size?
 
Widths can very between all tires even with the same measured size, especially between H/T's and A/T's.
But the big thing to think about is when airing down. Sure your tire fits when it's at road PSI, but when you air that sucker down it's gonna bag out a ton, especially if it's an A/T with an aggressive sidewall and sidetread.
 
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