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[feeutfo]

So According to this load rating chart
http://www.tesco-tyres.com/help/load-rating
A load rating of 87 would cover the front axle at 545 a tyre. 1090kg total
A load rating of 89 would cover the rear  axle at 580 a tyre. 1160kg total
That gives a total load rating covered weight of.        ..........2250kg gross


Ok not much room for error there, but why do we need a load rating of 94 on the front axle? Giving 1340kg load rating at 670kg a tyre. That's 260kg more load rating than required JUST on the front axle.(working worst way admittedly)

What am I missing?

[feeutfo]

Wikipedia gives omega curb side weight of 1530kg, although I'm not sure how accurate that is as it covers all the facelift options.

If accurate that gives the omega a load carrying capacity of 670kg, up to 2200kg

[feeutfo]

What am I missing?

...and don't say custard.

[feeutfo]

Parkers give 1700kg for the 3.2 saloon.
http://www.parkers.co.uk/cars/reviews/facts-and-figures/vauxhall/omega/saloon-1994/20769/

[05omegav6]

I would suggest that the extra 20-25% load ability is there to allow for lateral forces acting on each wheel as the car is driven, plus a safe margin. I doubt it would be possible to reach 1.5g in an Omega without dying un the process

A simple way of proving this would be to buy some tyres with the lower ratings and drive it as normal. I doubt that they would last long and the car would become a wallowing jelly

For what they cost, get a pair of Runways, and try them for a comparison. If you don't get on with them then I'll have them off you

[feeutfo]

I could understand it on the rear, but on the front?

Seems to me irmschers load rating of 91 on the front and 93 on the rear is nearer the mark.

[05omegav6]

Braking hard into a corner and you've got the 500+ kgs of one front corner of the car plus the weight transfer from the other three quarters all being loaded onto the outer front wheel. The momentary loading on that one corner could easily exceed a ton

[feeutfo]

Ok so going back to 2woody's post about a tyre completing a tyre test, is it fair to say that Irmscher have tested those load ratings, given the tuv certificate?

And would less sidewall(ie a lower profile) be a stronger sidewall for instance. And therefor a lower profile would cope better and allow a lower load rating?


Especially given the only difference between the tram lining o1 sc3 and the approved sizes in the tuv cirt is that my o1 sc3 have extra load stamped on them.

[05omegav6]

Perhaps but as 2woody mentioned earlier the number of plies in the sidewall are irrelevant... Would a single ply sidewall of 6mm be weaker than a two ply one made up of two three mm plies okay a simplified idea, but...

There is obviously a significant difference in the construction of the tyres which is causing the problem, something only the tyre manufacturer can answer.

Lower profile tyres will always flex less as there is simply less vertical give in the sidewalls.
Whether they actually allow a lower load rating depends entirely on the construction of the tyres including the number of plies and also how they are actually made

[TheBoy]

I could understand it on the rear, but on the front?

Seems to me irmschers load rating of 91 on the front and 93 on the rear is nearer the mark.

Who would you tend to believe, GM who spent milliions developoing the car, or some tinpot styling company who can't even make the bodykits fit properly

Of course, GM may have picked higher rated tyres for other reasons, based upon their findings when they were testing.


The little Rover, for eg, had a top speed of 110, maybe 115mph. Yet came with V rated tyres.  Mine always had V rated tyres, as thats what Rover specced. Its handled like a dream - one of the best FWD cars I've driven for handling.  A college had a 1.4 one that had 14" rims, and had H rated tyres, that just understeered everywhere under power. So there is something different in the construction for speed ratings (both were P6000s).  I wonder if its similar for load ratings?  Probably not relevent, just thinking aloud really.

[feeutfo]

If gm had tested an 18" tyre, maybe.

The only evidence we have of a tested 18" tyre has not been taken into account by either of us.

By coincidence, the one I bought is the correct type, and behaves well.

The one you bought is not to spec and misbehaves.

[TheBoy]

If gm had tested an 18" tyre, maybe.

The only evidence we have of a tested 18" tyre has not been taken into account by either of us.

By coincidence, the one I bought is the correct type, and behaves well.

The one you bought is not to spec and misbehaves.

I had wondered if rim size would make a difference. But GM specifiy that for all the (standard - 15,16,17) sizes.

Irrespective of the rim size, if it is purely on weight and calculated forces, that will not vary with rim size.


I think you just happened to stumble upon a tyre that worked well on the car. Same as I did with the Rover...  ...I strayed to other brands, supposedly superior, only to end in a poorer tyre.

[feeutfo]

If gm had tested an 18" tyre, maybe.

The only evidence we have of a tested 18" tyre has not been taken into account by either of us.

By coincidence, the one I bought is the correct type, and behaves well.

The one you bought is not to spec and misbehaves.

I had wondered if rim size would make a difference. But GM specifiy that for all the (standard - 15,16,17) sizes.

Irrespective of the rim size, if it is purely on weight and calculated forces, that will not vary with rim size.


I think you just happened to stumble upon a tyre that worked well on the car. Same as I did with the Rover...  ...I strayed to other brands, supposedly superior, only to end in a poorer tyre.

I'm sure somebody said that earlier, let me check... Oh yes, it was me. happened to be the correct one too.

[TheBoy]

If gm had tested an 18" tyre, maybe.

The only evidence we have of a tested 18" tyre has not been taken into account by either of us.

By coincidence, the one I bought is the correct type, and behaves well.

The one you bought is not to spec and misbehaves.

I had wondered if rim size would make a difference. But GM specifiy that for all the (standard - 15,16,17) sizes.

Irrespective of the rim size, if it is purely on weight and calculated forces, that will not vary with rim size.


I think you just happened to stumble upon a tyre that worked well on the car. Same as I did with the Rover...  ...I strayed to other brands, supposedly superior, only to end in a poorer tyre.

I'm sure somebody said that earlier, let me check... Oh yes, it was me. happened to be the correct one too.

I do fail to see how Irmscher feel they can specify a tyre that doesn't meet GM's spec. But then, our experience of Irmscher's engineering.....

[feeutfo]

If gm had tested an 18" tyre, maybe.

The only evidence we have of a tested 18" tyre has not been taken into account by either of us.

By coincidence, the one I bought is the correct type, and behaves well.

The one you bought is not to spec and misbehaves.

I had wondered if rim size would make a difference. But GM specifiy that for all the (standard - 15,16,17) sizes.

Irrespective of the rim size, if it is purely on weight and calculated forces, that will not vary with rim size.


I think you just happened to stumble upon a tyre that worked well on the car. Same as I did with the Rover...  ...I strayed to other brands, supposedly superior, only to end in a poorer tyre.

I'm sure somebody said that earlier, let me check... Oh yes, it was me. happened to be the correct one too.

I do fail to see how Irmscher feel they can specify a tyre that doesn't meet GM's spec. But then, our experience of Irmscher's engineering.....

do gm produce an 18?