Tyre Dilemma!

FozzyMatt

FozzyMatt

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Joined
Jul 3, 2011
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176
Hey guys, I have an unfortunate feeling that I know what the answer to my following question is going to be but I thought I'd ask anyway!

So, I recently got a set of Cooper Discoverer tyres for a bargain price, which I was rather happy about. The problem before me is that the Cooper tires are 215/75 R15 whereas both my spares at 205/70 R15. Now, by some miracle is this size difference small enough not to matter or am I going to need to go out and buy two new spares?

Thanks in advance guys.
 
FozzyMatt said:
Hey guys, I have an unfortunate feeling that I know what the answer to my following question is going to be but I thought I'd ask anyway!

So, I recently got a set of Cooper Discoverer tyres for a bargain price, which I was rather happy about. The problem before me is that the Cooper tires are 215/75 R15 whereas both my spares at 205/70 R15. Now, by some miracle is this size difference small enough not to matter or am I going to need to go out and buy two new spares?

Thanks in advance guys.
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yes, I reckon it will make a difference.

I have one spare that is 215/75 R15 and another that is 205/70 R15. The difference in diameter would only be about 2cm I think.

I only intend to use the smaller if I am in an absolute pickle, and then would be aiming to get somewhere asap for repairs. My plan in that event is to slightly deflate the other three tyres so that they are all roughly the same diameter. I reckon that would work, but haven't tried it. Maybe I should.
 
Thanks for that.

Yeah I'd thought about deflating them, but I might do like you've said - I'll get another spare that is 215/75 and then have the smaller one as my emergency.
 
Are you nuts? that's over 4" difference in rolling diameter, I wouldn't even put that strain on the center diff in snow....DON'T USE THEM!!! "period" my mechanic ( before he up and died 10 days ago) would even go nuts if I had new tryes on the front and near bald on the back
Tire size calculator
One more thing, letting some air out if your tyres does not change the rolling diameter, it just flattens the bottom of the tyre, if you can't afford new ones go to a tyre shop go out the back and find a couple of bald ones & have them stuck on until you can get something decent.
 
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Ok. You guys reckon 10-14mm difference would matter much? I know if its on the back it wouldn't be so bad compared to on the front.
I wouldn't of thought the strain with a manual wouldn't be much as you have open diffs front and rear 9well I do) plus a very average centre lsd. I have had 1 wheel spin before so wouldn't it kind of act the same as that with a smaller tyre.
 
Nah the strain is being put through the whole drivetrain, center viscous cops the most if there is a wheel out of size, I wouldn't bother too much about 10-14mm but I'd be hesitant to go much more if you want things to last, spinning a wheel makes no difference. I'd think an auto would cope better as they can slip on the clutches.

I'm no expert but I listened to what the expert said, as far as him dying karma is a biach, when I was married over 20yrs ago there were two guys screwing my Mrs (that I know of lol) one of them being my mate whom she went and lived with for 8 yrs....not being one to hold grudges we became mates again but now they are both dead.........YA GET THAT!!!!
 
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Of course, with an auto you can put the odd tyre on the back and switch to FWD.
 
I still don't think that would be good for the rear diff though Kevin
 
Don't do it, ever...

Stay committed, you own a subaru, do the right thing...

Get the whole set shaved down if it's your only option. Rotate tyres often, otherwise in 10k you might need a whole new set.
 
Dulagarl said:
yes, I reckon it will make a difference.

I have one spare that is 215/75 R15 and another that is 205/70 R15. The difference in diameter would only be about 2cm I think.
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remembering that the "75" and "70" is a percentage of the tyres width ie 75% of 215mm and 70% of 205mm respectively and then add the rim size in inches (25.4mm/inch) somebody else do the math please :cool:

taza said:
Ok. You guys reckon 10-14mm difference would matter much? I know if its on the back it wouldn't be so bad compared to on the front.
I wouldn't of thought the strain with a manual wouldn't be much as you have open diffs front and rear 9well I do) plus a very average centre lsd. I have had 1 wheel spin before so wouldn't it kind of act the same as that with a smaller tyre.
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'dont do it , mechanical sympathy goes along way
d_generate said:
Nah the strain is being put through the whole drivetrain, center viscous cops the most if there is a wheel out of size, I wouldn't bother too much about 10-14mm but I'd be hesitant to go much more if you want things to last, spinning a wheel makes no difference. I'd think an auto would cope better as they can slip on the clutches.

I'm no expert but I listened to what the expert said, as far as him dying karma is a biach, when I was married over 20yrs ago there were two guys screwing my Mrs (that I know of lol) one of them being my mate whom she went and lived with for 8 yrs....not being one to hold grudges we became mates again but now they are both dead.........YA GET THAT!!!!
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if wife sleeps around the best revenge is for the "other fella" to be left with her
karma was extraordinarily nice to you though :iconwink:
Greentreefrog said:
agreed .. you want your diameters within millimeters not inches !

and sorry about your mechanic, he was wise
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maybe not so

Kevin said:
Of course, with an auto you can put the odd tyre on the back and switch to FWD.
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Rally said:
I still don't think that would be good for the rear diff though Kevin
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just dont do it
paffoh said:
Don't do it, ever...

Stay committed, you own a subaru, do the right thing...
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thats it guys simple

Mechanical sympathy is the key, most people on here understand how their car works, just work with what youve got , which is an exceptional performer in the right hands

cheers Andy
 
Well its too late now. I have 6 tyres/rims. 4 on the car which are Geolander AT-S in 215/70R15. I have 2 spares, 1 with a bent rim, both with A/T tyres but in stock 205/70R15 size.
Im going on a big trip up north for a week and towing a tinny boat. So if I do get a flat I don't have a choice. If I wanted to get the same size spare I would have to order it from Perth and I don't think it would get here the same day.

I do however have a puncture repair kit so if it a puncture I will fix it when I get the my destination.
 
Do it if you must but maybe put it on the left side and keep one side off the road as much as possible to allow a little slip till you can get it repaired/replaced or you could end up on a tow truck, got RAC cover??

Little trick if you roll a tyre off a rim, after cleaning .........
Everyone should watch this [ame="https://www.youtube.com/watch?v=rNVXHbja0cE"]How to inflate a tyre with a can of WD-40 - YouTube[/ame]
 
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taza said:
Does that trick actually work? Anyone on here tried it?

Thanks for the advice guys!
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You bet it does. l've done it once before to reseat a 38" Super Swamper with some friends. Just don't use a TON of it, otherwise you could blow yourself & the tire to smitherines ;) - as you can see from numerous & humerous youtube vids ;) . Just need a compressor handy right afterwards, otherwise the tire will deflate quickly & you'll have to do it again.
 
Rally said:
I still don't think that would be good for the rear diff though Kevin
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I've done it only once; a short distance around 3 klm with a pair of 15's (21575R15) on the back and a pair of 16's (21565R16) on the front.
 
Yeah, I'd imagine the diff could live with that
 
Well since the general opinion seems to be that it would be an awful idea, I'm sadly going to have to put my Dueller's back on for my trip over cup weekend and save the Coopers until I can get some appropriately sized spares. Better safe than sorry, even if it means driving on the lesser tyres.
 
I had to change the FLH wheel today as my tyre had a small nail in the tread area and was 1/2 flat. I didn't want to risk driving 3 kms to a servo to inflate it in case I fractured some of the steel belts.

I swapped it over for my spare wheel which had a brand new tyre on it, current set are on their last legs (nearly 60,000kms), and drove 3kms to Bob Jane Tyres for a repair, back home and then back down again to pick it up as they were flat stick this morning, they put my normal wheel back on for me when I picked it up.

I hope I haven't wrecked anything in the process.

:eek: :eek:
 
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