195/60 R15 on 1.4 Sport.

Providence

Providence

A2OC Donor
Please see below a picture of my car. I obtained these wheels from A2Steve (thanks mate) and have immediately put some new Bridgestone Turanzas on them. The comfort level has improved very much over the RS4 215/40 R17 that they have replaced. In theory I have :

Improved ride.

Slimmer tyres and low rolling resistance should improve MPG.

I've just been for a run and the steering is slightly lighter but still not too light and the turn in is quicker. The dry grip is not much different to before but didn't really manage to get to the ragged edge on this trip!

The tyres look a bit chubby but I think I'll get used to the look!

I have been worried for some time that by doing this I would ruin the handling but I am pleasantly surprised that if there's a difference it's very slight.

It has been mentioned around the club that 205/45 R17 makes the speedo close to true. The 195/60 R15 is very close to the same diameter and on my test run it seemed speedo was overreading by a lesser amount. 50 MPH showed 49 on the nav.


IMG-20191031-00100.jpg
 
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Just thought I'd refresh this. The main point of putting this up at all was for reference for any present or future member who may be considering softening the ride.

I went out in torrential rain on Saturday and managed to go for it a bit due to the roads being quite empty. I 'pushed' it round most of the roundabouts and was impressed with the wet grip. I managed to make it let go once and it was a very controllable progressive slip that stopped immediately with a throttle lift. The previous tyres were Kumho Ecsta Le Sport KU39 which were good in the wet anyway.

I really cannot tell the difference on dry grip at all.

The comfort level is much improved. On the roads round here I have deliberately driven at bumps I used to swerve with no distress! Speed ramps can be taken at 20ish and those hard ridges they have in Asda do not bang the rim.

I haven't measured it but it feels like the car is faster. I can only assume that the combination of the low rolling resistance of the Bridgestone Turanza T005 and the reduced width must produce more acceleration due to the lower friction.

Too early to report on fuel.

I can honestly say that I was worried that I would enjoy driving the car less with these wheels/tyres but that is not the case.
 
The Holy Grail of Tyre Sizes doesn't list 195/60/15's so I'm curious to find out how you get on with these as I'm currently looking in to changing from the 175/60/15 Summers I have on to something a bit wider in an All Season. Love the comfort of the 60's, and they're pretty much a requirement for the roads around where I live!
 
Tsu said:
The Holy Grail of Tyre Sizes doesn't list 195/60/15's so I'm curious to find out how you get on with these as I'm currently looking in to changing from the 175/60/15 Summers I have on to something a bit wider in an All Season. Love the comfort of the 60's, and they're pretty much a requirement for the roads around where I live!
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195/55/15 are what you want; they will actually be marginally taller as well as wider than your existing boots, and providing you drop your tyre pressure slightly, will be more comfortable too.
 
I haven't mentioned tyre pressures. I'm running 30PSI front and 28PSI rear which seems to be the recommended pressure for most tyre sizes that are listed inside the fuel flap for light loads. It's usually just me, my wife and the dog (chihuahua) and shopping.

The diameters given on a tyre size calculator are as follows:

215/40R17 23.77"

205/45R17 24.26"

195/60R15 24.21"

I was running 215/40R17 tyres and they would rub on big bumps at the back when I had two adults in the back. I was not aware of any rubbing on full lock at the front. This of course might not apply to an SE, as I think the Sport had the 17" wheels as standard.

I have yet to go on a decent length trip or had any load in the car yet but will report back.
 
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steve_c said:
195/55/15 are what you want; they will actually be marginally taller as well as wider than your existing boots, and providing you drop your tyre pressure slightly, will be more comfortable too.
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I ran 195/55/15's on my AUA for 3 years and never gave them a second thought until I recently acquired a BBY with 175/60/15's and the ride is so much more comfortable. It may be down to the suspension as I bought it with 69k on the clock so could still be original. No service history to say otherwise and I haven't been underneath it for a look yet to confirm. Having said that I overhauled the AUA with Spidan's and Monroes only a year ago so it felt firm without being crashy. The BBY feels more floaty, but in a good way. More Audi-like.
 
Providence said:
I haven't mentioned tyre pressures. I'm running 30PSI front and 28PSI rear which seems to be the recommended pressure for most tyre sizes that are listed inside the fuel flap for light loads. It's usually just me, my wife and the dog (chihuahua) and shopping.
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Your tyre pressures seem a bit high.

I would suggest you drop to 29psi front and 26psi rear in a lightly loaded car (ie. if you aren't carrying rear passengers and luggage), but you may be able to go lower if you read the rest of my post and do some simple calculations.

175/60R15 tyres have a load index of 81 (462kg).

195/60R15 tyres have a load index of 88 (560kg).

As 175/60R15 tyres are a standard size, you should be able to find out the recommended tyre pressures for that size.

When you have found the recommended tyre pressures for the standard 175/60R15 tyre size, multiply by 0.825 (462/560) to get the tyre pressures you need for the larger 195/60R15 tyres.



STOP READING THIS POST HERE, IF YOU DON'T LIKE NUMBERS!



For example, if a car has tyre pressures of 35psi front and 32psi rear with 175/60R15 tyres, you will only need 29psi front and 26psi rear with 195/60R15 tyres.

Here are the workings:

35psi x 0.825 = 28.875psi (or 29psi rounded to the nearest 1psi)

32psi x 0.825 = 26.4psi (or 26psi rounded to the nearest 1psi)

Note that there is an inverse proportion between the load index and the tyre pressure, ie. as the load index goes up, the tyre pressure goes down. This is because a higher load index tyre can support the same weight at a lower tyre pressure, or put another way, the higher the load index the more weight a tyre can support at the same tyre pressure. Also note that the weight a tyre can support has a direct relationship with the air pressure. For example, doubling the air pressure doubles the weight that a tyre can support and halving the tyre pressure halves the weight that a tyre can support. The original VW Beetle only used 16psi (1.1 Bar) in its front tyres (165/80R15) as the tyres had a high load index relative to the weight of the front of that car (its engine was in the back).

165/80R15 tyres have a load index of 87 (545kg) which means that when this tyre size is inflated to 3 Bar (44psi) it can support a weight of 545kg. As the original VW Beetle used 16psi (1.1 Bar) in its front tyres, its front tyres could support 200kg (1.1 / 3 x 545kg). If you pumped the rear tyres up to 24psi (1.65 Bar), the rear tyres could support 300kg. So both front tyres could support 400kg (2 x 200kg) and both rear tyres could support 600kg (2 x 300kg), and all four tyres could support 1,000kg (1 metric tonne). Assuming the tyres were supporting the full 400kg front weight and 600kg rear weight, this would give a 60:40 rear:front weight distribution. This means that the rear tyres would be supporting 50% more weight than the front tyres.
 
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There are pressures listed in the flap for a reason. There are recommendations on the forum from those who have driven the car for many thousands of miles and have had experience.

1.9 is low, very low. I haven't glanced at my pressures for a long time, but I'm sure nothing is below 2 on that flap.

@carlston - why are tyres your specialist subject?

- Bret
 
.. and? we're talking about A2s. 2000 onward. The Beetle - with its crossply tyres - has nothing to contribute to this discussion.

- Bret
 
bretti_kivi said:
The Beetle - with its crossply tyres - has nothing to contribute to this discussion.
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Owners nowadays tend to fit modern radial tyres.

Back to the A2, if you are talking about standard tyres then yes, with their low load index tyres. 81 in the case of 175/60R15 and 185/50R16, you will need relatively high tyre pressures.

However, if you fit tyres with a higher load index, there is no need to maintain such high tyre pressures. You can if you want to, but you will lose ride comfort if you do. The same logic applies if you fit tyres with a smaller load index. For example, if you fitted 175/55R15 tyres you would need to increase your tyres pressures compared to 175/60R15 tyres (about 4psi more). 175/55R15 tyres have a load index of 77 (412kg).
 
Why are you insisting that a size of tyre has a load index? I can find 185/55R15 with 82H or V or an 86 XL in the same size without looking hard.

86s are irrelevant when the max gross weight of the vehicle is around 1500kg. What's the point here?

- Bret
 
bretti_kivi said:
Why are you insisting that a size of tyre has a load index? I can find 185/55R15 with 82H or V or an 86 XL in the same size without looking hard.

86s are irrelevant when the max gross weight of the vehicle is around 1500kg. What's the point here?
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Some car tyres are XL (Extra Load). This means that they can be inflated to 3.5 Bar (51psi) instead of the standard 3 Bar (44psi).

A 185/55R15 82H tyre has a load index of 82 (475kg) whereas a 185/55R15 86H tyre has a load index of 86 (530kg). However, for all tyre pressures up to 3 Bar (44psi) both tyres can support the same weight. The XL tyre can only support more than the non-XL tyre when it is pumped up to more than 3 Bar (44psi).

For the purposes of calculating tyre pressures you need to compare load indexes at the same pressure. So even if you want to fit an XL tyre, you need to use the load index at 3 Bar (44psi) not 3.5 Bar (51psi). So for the 185/55R15 you would use 82 (475kg) not 86 (530kg).

If you didn't do this, you might think that a 175/55R15 81H XL tyre can use the same tyre pressure as a 175/60R15 81H tyre. Of course it can't, because the load index of the non-XL 175/55R15 tyre is 77 (412kg). The 175/55R15 81H tyre only gets its 81 (462kg) load index when inflated to 3.5 Bar (51psi), whereas the 175/60R15 81H tyre gets its load index of 81 (462kg) at a lower 3 Bar (44psi).

What you are doing with the load indexes is finding the multiplier that you need to use to calculate your new tyre's air pressure. To keep the maths simple, imagine two tyres...one has a load index of 400kg at 3 Bar and another has a load index of 800kg at 3 Bar. Let's say the 400kg tyre is standard and has a known tyre air pressure of 2.2 Bar (32psi). The multiplier that you need to adjust this standard air pressure is 400/800 = 0.5

So now you multiply 2.2 Bar (32psi) by this multiplier which is 0.5

This gives you a new tyre pressure of 1.1 Bar (16psi) for the tyre with the 800kg load index.

However, a more realistic example for the A2 is to use the load index of 81 (462kg) and 88 (560kg). You would then get a multiplier of 462/560 = 0.825
 
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Wow.

I have no idea where you have this from, but I'd like to hear the source.

Some of us *have* to have the specifics from the tyre - like an H or a V rating or a load rating - correct. Or we don't get insurance, through tech inspections and the like. The tyre pressures have absolutely nothing - and I mean nothing - to do with the load rating.

I'm intrigued as to why you think pressure is relevant for load. This doesn't mention it - https://www.ctyres.co.uk/general/load-index - nor does this - https://www.oponeo.ie/blog/tyre-load-index - nor do Blackcircles, one of the UK's biggest tyre retailers, here: https://www.blackcircles.com/helpcentre/tyres/what-is-load-rating

If none of them think pressure is relevant, why do you?

I know from experience that 0,2 bar can make a serious difference to driveability of the car, but the manufacturers also make recommendations, both of the car and the tyre and they may contradict. I also know about the difference low temperatures make and I'm not convinced lower temps mean lower load capability.

- Bret
 
Crikey this topics running on and on it’s getting very complicated ..well for me anyway ?..is this anything to do with short daylight hours in Finland this time of year ..??.. joke bretti.
 
bretti_kivi said:
I know about the difference low temperatures make and I'm not convinced lower temps mean lower load capability.
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Tyres are checked at 20 degrees C. If it gets cold, the pressure will drop. However, this isn't a problem because when the car is driven the air inside the tyre will warm up and therefore the pressure will get back to normal. Tyres fail when they get too hot. As the tyre pressure gets back to normal before the tyre gets too hot, the tyre won't fail.

Question for Bret:

Two of the standard tyre sizes that the A2 uses are 175/60R15 and 185/50R16. How does the contact patch with the road of these tyres vary? Which tyre has the biggest contact patch with the road in area?
 
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carlston said:
Tyres are checked at 20 degrees C. If it gets cold, the pressure will drop. However, this isn't a problem because when the car is driven the air inside the tyre will warm up and therefore the pressure will get back to normal. Tyres fail when they get too hot. As the tyre pressure gets back to normal before the tyre gets too hot, the tyre won't fail.

Question for Bret:

Two of the standard tyre sizes that the A2 uses is 175/60R15 and 185/50R16. How does the contact patch with the road of these tyres vary? Which tyre has the biggest contact patch with the road in area?
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Is this a trick question ..? as on the face of it I would say 185 50 16 ..
 
carlston said:
Tyres are checked at 20 degrees C. If it gets cold, the pressure will drop. However, this isn't a problem because when the car is driven the air inside the tyre will warm up and therefore the pressure will get back to normal. Tyres fail when they get too hot. As the tyre pressure gets back to normal before the tyre gets too hot, the tyre won't fail.

Question for Bret:

Two of the standard tyre sizes that the A2 uses are 175/60R15 and 185/50R16. How does the contact patch with the road of these tyres vary? Which tyre has the biggest contact patch with the road in area?
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Isn’t it generally lower profile have bigger contact patches? And higher profile more progressive


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the difference is minimal, that one's already been proven. The difference in pressure over the area of the contact patch makes any size difference pretty much moot, anyway, at least for damp or wet roads. Similar for snow, where the only (minimal) advantage of the narrower tyre is the marginally lower energy required to push it through freshly fallen stuff.

- Bret
 
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