Otis

Moderators please feel free to move this to the Tyres and Brakes section. I just thought that if the advice I have been given is correct it perhaps warranted posting in here.

Anyway, I have been speaking to a mate who is the manager at a tyre and exhaust centre regarding new tyres for my MY00 which has P1 wheels and 205x45x17 P-Zeros. What he is saying is that the Impreza should run on reinforced tyres that have a 'Load Index' of 87 or 88. I was quite taken a back by this as this ruled out most of the 215x40x17 options, including Toyo Proxes and Bridgestone SO3.

While I was there he rang the buyer of their import division and without hesitation he also confirmed what my mate was saying. He went on to say that he had read quite a bit about this issue and the Impreza in the trade circulars and publications that cross his desk. He has had a couple of Cossies himself so, although not quite one of us, he knew where we were coming from.

I have therefore done a bit of research and it would appear Imprezas come from the factory with an 87 Load Index tyre. So I took this up with the Technical Dept at International Motors today and sure enough they confirmed tyres with a Load Index lower than 87 are not recommended. They said that at the UK speed limit of 70mph the risk is not as high as say on the the German Autobahns, where prolonged high speed driving can lead to tyre wall failure. Now they were clearly towing the party line by stating the 'no risk at 70mph', but let's be honest we do subject these cars to little more stress than a steady 70mph cruise, be it on road or even more significantly on track.

So there it is. What do we all think? If I go for 215x40x17 I will end up with a load index of 83. If I stay with P-Zeros my tyres may be okay but I don't think my nerves could cope with it . The other solution is 215x45x17 where the Toyo and Bridgestone load index figures shoot up to.....yes you guessed it.....87.

Hopefully someone will prove this to be a load of *****, however on the back of my Subaru UK converstaion alone, I somehow doubt it is. Either way don't shoot the messenger .


Otis.

chrisp

I thought it depended on rating for speeds ie Z rated tyres are rated upto 150mph

DemonDave

iTrader: (13)

Load index is the maximum weight carried at that speed

http://www.tyremaster.com.au/fitment...m?ct=13&pg=709

http://www.toyo.co.uk/pages/loadindex.html

[Edited by DemonDave - 10/14/2002 8:39:48 PM]

stef555

And how many accidents have happend b'cause of the toyo's etc.? never heard of one, do you?

Grts. Stefan

p.s. driving on toyo's 215-40-17

DemonDave

iTrader: (13)

83 = 487kg *4 = 1948kg

4dr figures

Gross scooby weight = 1750kg

Kerb Scooby weight = 1235kg

And the load index is at the high speed rating

So an 83 should be ok.

[Edited by DemonDave - 10/14/2002 8:46:14 PM]

DemonDave

iTrader: (13)

Gross Vehicle Weight (GVW) = Maximum Permitted weight (MPW)

Q I am confused about my car’s kerb weight as the handbook says that it includes the driver. Is this correct?

A The usual definition of kerb weight is a vehicle in its ready to use condition with all tools, spare wheel etc. and a full tank of fuel. Many vehicle manufacturers are, however, now following European Directive 95/48/EC which specifies the kerb weight as a car in ready to drive condition with the fuel tank 90% full, a driver on board weighing 68 kg and luggage of 7 kg. Any extras or accessories fitted after purchase will increase the weight and reduce both payload capacity and hence the towing limit. When looking at a car’s specification in a brochure please check the method of determining the kerb weight. If it is to the EC Directive you must allow for the weight of any other passengers and luggage and deduct that weight from the towing limit accordingly.

DemonDave

iTrader: (13)

Sorry bored ......

Otis

It must be oversight on Subaru's part. I'll ring Japan tomorrow and tell them .

Otis.
Not running 215x40x17 .

P1Fanatic

Well Ive just moved from Pirelli 205/45/17's to Toyo 215/40/17 after many a recommendation from other Scoobynetters and have never heard this before. Only time will tell but surely if it was such a major problem/fault then more people on here would have been affected?

Simon.

ed_the_duck

ok....looks like i got what im looking for!!!............I fitted a set of 215-40-17's g/year f1's (the newer o3's) and i completely wrecked n/s/f &n/s/r (not as bad as the front mind) within 250 miles from new. and all i did was hammer it round a roundabout a few time to do the bulk of damage......wonder what the load rating is on these, the walls look like they was run flat (was actually at 32/3 psi) and the tread it was ripped away........any thoughts on what was wrong....running a standard my00 with 17's?????

BruceWarne

What's a scooby's effective weight at say 120 mph...What's the nett influence of all the wings and spoilers at those speeds?

mutant_matt

Bruce,

Most of the spoilers out there apparently reduce lift but don't elimiante lift. That would imply that the car is lighter, the faster you go.

However, some spoilers/wings create downforce (but I don't think that many actually do) in which case, the car should get heavier at speed. I'm pretty certain that the UK300 front and rear spoilers create some downforce as opposed to reducing lift.

Matt

Neil Smalley

Matt et al Reproduced below is part of an email I had from Mike Wood(from Prodrive) ages ago
Both the UK300 aero package (rear spoiler and front bib) as well as
the STi Prodrive Style have noticeable benefits to high speed
stability. If you look closely at the STi spoiler it has a negative
approach angle to the upper element (when compared to the ground, not
the airflow over the car) as the lower part on the boot lid also gives
some aero load. If we hadn't done this the car would have downforce
which is very bad on a road car as you need to support the extra load
at speed.
Every other spoiler I have seen that has 2 elements similar to this
has a much higher angle of attack to the upper element which will give
too much downforce and hence high speed instability or understeer. I
don't think anyone else has bothered putting the car in a wind tunnel
so they will never really know anyway.

MikeWood

This is why all the tyres that we recommend have a load rating that is is at least as high as the OE tyre. It isn't just about the total vehicle weight but the max load rating on each axle.

As an example, in the 225/40zr18 size we use on WRX and STi there are lots of tyres available in a 88 load rating. These are generally Porsche developed tyres which are used on the relatively unloaded front axle. These would be perfectly legal to use on a WRX which has an OE tyre load rating of 87 but not on an STi where it's 91. When you think about it, would you want to use a tyre on the front of your Impreza that been developed for the front of a car that is much lighter and only steers not drives (on most models) All the tyres we supply for WRX & STi are 92 load rating.

Would you really want someone to look closely at your tyres following an incident and find that you have the wrong load rating fitted? I know I wouldn't, even if they weren't at fault.

Regards

Mike

Flyboy-F33

I came accros a similar issue recently when fitting tyres to my last 911 (964) The manager of the tyre supplier said that if I used the wrong load rating and was involved in an accident, the insurance company probably wouldn't pay out. Obviously there was a wide range of tyres of the correct profile and size, but only one or two had the required load rating.....you guessed...thge most expensive ones. Be warned.!

SimonH

So the PZeros fitted to my P1 that have the wet weather grip of a cat on ice are okay with regards to load rating but a lot of the others aren't?
What 17" tyres can I fit to my P1 that will allow to me to go round a roundabout in the wet without either a) me being overtaken by old men on bicycles or b) me ploughing straight on into the kerb???

PS. bit miffed because I went out in my "new" P1 in the wet for the first time on Sunday...deeply unimpressed with the PZeros compared to the Toyos on my old turbo

Neil Smalley

Just checked my manual. Nowhere can I see about the load rating of the tyres needing to be 87 or 91. It says they need to be the same, not over a certain number(if i've missed it can someone point it out to me)

If this is as big an issue as is being made out Subaru need to issue an addendum ASAP, because by not telling people they could be liable for any accidents that result of an incorrect load rated tire being fitted.

TonyBurns

iTrader: (3)

Mike,
I take it the P Zero's make the mark for 215/40/17? but as most people (me included) run tyres like Bridgestone SO2 PP's on the same size (83 rated on a MY00 turbo) would there be any adverse affects (taking into account that i find these tyres to be rather excellent in both wet and dry conditions and these are my second set ive fitted) also that i never run a fully loaded car etc?
Also what tyres do Prodrive actually reccommend in the sizes 205/45/17 and 215/40/17?

Cheers!
Tony

Dan B

Is this the same manual that recommends we all run around with 0W30 oil? Pinch of salt peeps??? If they're more expensive of course they are better!! Every salesman knows that.

I run with Toyos, and they seem to be alot better than what others are running, and better than my last lot. I've done 8K on them and they've still got 6mm of tread on them. I'm very happy (haven't been ***** footing around either, )

[Edited by Dan B - 10/15/2002 12:37:59 PM]

johnfelstead

Interesting discusion, not something i have seen on this BBS before.

I run my STi on 215/40x17 SO2 PP, like a large number of people. I take it to 150MPH regularly and put it under extreme loads on track.

I have never been informed by any tyre supplier that the load rating was unsuitable so i will have a look into this.

I would say however, that the SO2 PP is one of the safest tyres you can buy, it is designed with some run flat capability to give you a fighting chance if you have a puncture at speed. That was one of the factors in me choosing to use it. The other main factor was that as an alround performer, it's unmatched IMHO, working extremely well in all weather conditions.

Jeff Wiltshire

Interestingly there are N0, N1 & N2 variants of most high-performance tyres (including SO2/3) specifically for Porsche. I had always assumed it has to do with the load index.


Jeff

speedking

DemonDave: Don't forget about weight transfer. Your simple sum may be valid on a stable flat surface at constant speed, but

1) On a motorway, if you go over a crest and then into a depression then the total weight of the car will increase significantly.

2) When cornering the outer wheels will become more loaded than the inner, in extremis the inner tyre of a 205 will lift off the surface, so the outer tyre is carrying twice the load

3) Cornering introduces lateral loads that are flexing the sidewall and reducing the capacity to carry vertical load.

On a MY02 the tyres have a load index of 87 = 545kg. This only allows 25% margin over your quoted weight. (Admittedly at 149mph)

This appears quite reasonable, and I for one will be looking out for this in the future.

johnfelstead

Tyre presure has a lot of input on the real world effects of this too. When i first installed SO2's on my Sport the car definately moved more on its tyre sidewall than with the RE010, so i ran more presure to compensate.

I use 40PSI on track, 34PSI on the road, going up to 40PSI makes a big diference to the way the tyre can support the load in high G corners.

Squizz

I used to have TOYO T1-S on my Impreza MY99. I went over a piece of board left on the M5 at about 90...erm...kph? And there was an almighty noise.

No problem with steerage, and I slowed a great deal to check the feel of the car. No problems so picked up my rate again and carried on.

Got to the car-park and could hear a slight rattling noise. Got out to find rear passenger tyre totally deflated, and a rather large gash in the sidewall!!! [img]images/smilies/mad.gif[/img]

Now, I've had flat tyres before now and I simply couldn't tell. So full marks to the Impreza running-gear and I'm sure the TOYO construction helped out. besides, they're the best thing in the wet I've ever driven on...

Load Index? Since when...

TaviaRS

DemonDave, what you say is correct, your Scoob does weigh less than the load rating of the tyre, however you need to reduce the max weight permitted on the tyre in accordance with the speed of the tyre (if that makes sense).

Tyres marked V in conjunction with a load index eg 93V are suitable for speeds in excess of 210km/h and up to 240km/h. The load index relates to 210 km/h and must be reduced by 3% for every 10km/h up to 240km/h.

Tyres marked W in conjunction with a load index eg 83W are suitable for speeds in excess of 240km/h and up to 270km/h. The load index relates to 240 km/h and must be reduced by 5% for every 10km/h up to 270km/h.

Tyre marked VR within the size designation are designed for speeds in excess of 210km/h

Tyres marked ZR within the size designation are designed for speeds in excess of 240km/h


210 km/h = 131 miles/h
240 km/h = 150 miles/h

Does that make any sense? Me I run 91W on mine and very nice they are too

gregh

IMHO Looks like this is true taking into account what was origionally posted and then reading what Mike Wood writes about why they only use certain tyres.

For those of you running tyres with less than the recommended load index I would be very concerned about taking your car on track/autobahns.

Regards,

Greg

[Edited by gregh - 10/15/2002 9:26:59 PM]

wacky.banana

I assume Mike Wood needs to tread carefully (no pun intended) on what he says BUT:

How much of an issue is this? If its serious why is there nothing in the manuals about this? We all swap tyres for different types for a whole host of reasons and tend to make damned sure that the specification, in terms of rating and size,are comparable/identical (take your pick).

If load bearing is another factor in the equation then in the interests of road safety can we be told this categorically, and told this now please?

I could not forgive myslf if after fitting replacements in good faith it was proved that I, say, inadvertently caused a death due to a tyre going caput because it had the incorrect load bearing for the car.

Mike, I have just tried to email you to take this issue offline to protect you (if that's what is required to get a definitive answer on this one). However there is no email address in your profile.

This seems too serious an issue to drop in a couple of lines and then go quiet.

Maybe you could drop an email to one of the mods on a non-attributable basis so we can at least have some concrete info to go on?

If you can't do this could you at least persuade someone from IM to do so?

WB

Otis

Well for me the solution is going to be 215x45x17. The Toyo and SO3 are both 87 in that size and it will make my speedo underead by 0.9mph - I think I can live with that. I'm actually going for the Goodyear F1 subject to my 'tyre mate' confirming the Load Index tomorrow morning.

Don't get me wrong guys. I'm not a scaremonger(sp?) by nature. I'm on my 5th Scoob now and you never stop learning with these cars. The best thing about this BBS is the opportunity it provides to share info and kick it about a bit. I just thought I should run this issue up the flag pole and see who saluted. I don't think we need to panic or bombard Subaru or Mike Wood with demands for action and information. Just go away, ask about a bit, come back and report, and let's take it from there. Then perhaps we could make a singular formal approach as Scoobynet (perhaps by Mr Felstead as one of our respected technical moderators) to Subaru UK requesting a little clarity on the matter. I think we'll get a more focused response.

Anyhoo, time for bed.


Otis

ed_the_duck

be interested in the load rating on the new f1........as i said i messed them up ans it looks like they were run flat and that was @33 psi on a roundabout they are zr rated 215 15 17's...looks like they got too hot and lumps went missing on the tread and most of the info on the walls was gone!....need a new set now and not sure what to get...if anyone has any suggestions

johnfelstead

You saying you chunked the tread and wiped the sidewall out on one roundabout? To chunk the tread you have to get the tyre temp very very high, to wipe the lettering off the side takes a fair amount of time on very high loading. Neither of those two is going to happen on one roundabout no matter how crap the tyre is for the aplication.