SE 15" Tyres - Alternative Sizes

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SE 15" Tyres - Alternative Sizes

Postby elaverick » Tue 04.12.2018, 20:58

Has anyone tried running with 195/60 R15s?
A friend who works in the tyre industry was enlightening me about the way the sizes are calculated and pointed out that 195/60's are only 1.38% (8.5mm) wider than the 205/50 R15s that are recommended. He says that they should fit without causing too many problems, but advised me to ask here in case anyone had actually tried them to see if there were any issues with rubbing or other unexpected fit issues.
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Re: SE 15" Tyres - Alternative Sizes

Postby Giniw » Tue 04.12.2018, 21:04

195*.6=117
205*.5=102.5
diff=117-102.5=14.5mm if I am not wrong so I am not sure where he finds the difference is 8.5mm?

Anyway, I can't see why you would put 195 60 tyres on an Elan, I certainly would not want that on my car.
It would be a pity to ruin the handling and looks of a great car to possibly save a couple of pounds.
But that is just my opinion %)
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Re: SE 15" Tyres - Alternative Sizes

Postby par » Tue 04.12.2018, 21:31

I think you guys are getting tyre width and sidewall height mixed up.

The width of the tyres are as those stated i.e. a 195 tyre is 195mm wide and a 205 tyre is 205mm wide.

The 50 and 60 dimension referred to is the side wall size as a percentage of the width so for a 205/50 tyre the sidewall is 50% of 205 = 102.5mm and a 195/60 tyre the sidewall is 60% of 195 = 117mm.

Adding the wheel diameter into the mix allows for a side by side comparison of overall diameter which involves a quaint mix of imperial and metric units:

205/50 x 16" = 102.5 + 102.5 + (16 x 25.4) = 611.4mm

195/60 x 15" = 117 + 117 + (15 x 25.4) = 615mm

So this means this very little difference in the diameters of the 2 packages before factoring any tyre wear but the 195 option will be a narrower tyre by 10mm.

HTH :D
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Re: SE 15" Tyres - Alternative Sizes

Postby Giniw » Tue 04.12.2018, 21:52

par wrote:I think you guys are getting tyre width and sidewall height mixed up.
Mmm no I was referring to the sidewall size too?

Adding the wheel diameter into the mix allows for a side by side comparison of overall diameter which involves a quaint mix of imperial and metric units:
205/50 x 16" = 102.5 + 102.5 + (16 x 25.4) = 611.4mm
195/60 x 15" = 117 + 117 + (15 x 25.4) = 615mm
So this means this very little difference in the diameters of the 2 packages before factoring any tyre wear but the 195 option will be a narrower tyre by 10mm.
Why do you use 16" wheels in the first expression? Unless I read something too fast it's both the original OZ SE sizes, ie 15 inches rims — so 14.5*2=29mm difference in diameter.
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Re: SE 15" Tyres - Alternative Sizes

Postby elaverick » Tue 04.12.2018, 21:56

Giniw wrote:diff=117-102.5=14.5mm if I am not wrong so I am not sure where he finds the difference is 8.5mm?


It was going off the tool here - https://www.oponeo.co.uk/advice-and-tip ... veTireTool

And yeah it should be for 15" not the Federal/S2 16" ones

(Edit)

Having compared again it would actually need to be the 195/55 15's I think my friend had plugged in our standard tyres as 205/55 15's rather than 205 50 15s
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Re: SE 15" Tyres - Alternative Sizes

Postby par » Tue 04.12.2018, 22:06

Giniw wrote:
par wrote:I think you guys are getting tyre width and sidewall height mixed up.
Mmm no I was referring to the sidewall size too?

Adding the wheel diameter into the mix allows for a side by side comparison of overall diameter which involves a quaint mix of imperial and metric units:
205/50 x 16" = 102.5 + 102.5 + (16 x 25.4) = 611.4mm
195/60 x 15" = 117 + 117 + (15 x 25.4) = 615mm
So this means this very little difference in the diameters of the 2 packages before factoring any tyre wear but the 195 option will be a narrower tyre by 10mm.
Why do you use 16" wheels in the first expression? Unless I read something too fast it's both the original OZ SE sizes, ie 15 inches rims — so 14.5*2=29mm difference in diameter.


Sorry I misread the original post and thought it said 205/50 r16, however the OP was comparing width and the calculations being used are for sidewall height and comparing diameters.
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Re: SE 15" Tyres - Alternative Sizes

Postby elaverick » Tue 15.01.2019, 20:18

Ok so I’ve pushed the button on a set of 4 Michelin CrossClimate+ 185/55R15’s which are -0.3% different to the 205/50R15’s we normally run. With the mileage I do each year I didn’t think having a set of winter and a set of summer tyres was really economical, but as I couldn’t find all season tyres from a decent brand I decided to take the plunge on the smaller tyres.
I’ll report back once they’ve been fitted on the 2nd Feb.
It’s worth mentioning that my driving experience is very limited and my current tyres are now over 10 years old, so my findings may not be all that much use, but you shall have them anyway :D
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Re: SE 15" Tyres - Alternative Sizes

Postby Fredjohn » Tue 15.01.2019, 20:48

Interesting decision. However:

Your overall wheel/tyre diameter is only 1mm less, pretty much irrelevant as your speedo will only be reading 0.2kph slower when travelling at 60kph.

But you will be following Colin's philosophy of adding lightness: each corner will be about half a kilo less: reducing overall (and un-sprung) weight by 2kg. :clap: :clap:

It'll be interesting to hear of your experiences of how the car handles over the next few months.
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Re: SE 15" Tyres - Alternative Sizes

Postby rip » Wed 16.01.2019, 09:07

It is recommended to use slightly narrower tyres for snow & ice because they shift it out of the way better.
So I completely understand why you would be looking at 195s if you drive the car regularly in the winter.
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Re: SE 15" Tyres - Alternative Sizes

Postby Fredjohn » Wed 16.01.2019, 09:28

rip wrote:It is recommended to use slightly narrower tyres for snow & ice because they shift it out of the way better.
So I completely understand why you would be looking at 195s if you drive the car regularly in the winter.


Oooops Ian typo I assume. He fitted 185s, which are narrower.

Narrower tyres are better on snow because the contact surface is less, so increasing the pressure/weight on a smaller area and improving grip. Snow clearance is a function of tread depth and design.

They will help in winter conditions, being "CrossClimate", but not as much as full blown winter tyres. These have a better tread design for snow and more importantly different rubber compounds which work better at low temperatures, typically below 8degC.
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Re: SE 15" Tyres - Alternative Sizes

Postby rip » Wed 16.01.2019, 11:36

There was a mention of 195s earlier.
205s are standard so either 195 or 185 will be narrower.
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Re: SE 15" Tyres - Alternative Sizes

Postby elaverick » Tue 05.02.2019, 13:45

So the tyres have been on since Saturday and they've made a hell of a difference. In fairness I think this is just down to them being fresh rubber (compared to the 10 year old ones that were on there). I can tell any difference in cornering performance (although with the miserable weather at the moment I've hardly been pushing it), but the car just feels... fresher. Ride comfort is improved and the affect of some of the oddly cambered local roads seems to have been reduced as well. General road noise is significantly better as well, but this does now mean I can hear all the other squeaks and rattles around the cabin.

I'm not sure how much of the above is a psychological improvement - "they had better be better after spending all that money", and how much is genuine improvement, but the net effect appears to be big improvement with no trade off on performance or handling.
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