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[2woody]

]

more width = more grip (dry,wet)
[/quote]

more width usually = more grip in the dry

more width doesn't necessarily mean more grip in the wet

[cem_devecioglu]

]

more width = more grip (dry,wet)

more width usually = more grip in the dry

more width doesn't necessarily mean more grip in the wet

 
if water drain channels correctly designed it will.. however, its also dependant on water depth and your speed and weight of course..

[feeutfo]

what size do you actually have fitted at the moment ?

I am almost one million % certain it's not to do with width. Eg

245 x 45 x 18 sc3 mo (Mercedes variant) firmer by feel, harsher ride when cold, accepatble compliant ride when warm, run at 28psi to get heat into them and soften the ride, no tram lining at all. Absolutely rock solid. Even with both edges of the fronts worn away.


Currently fitted.
235 x 40 x 18 sc3 a01 (Audi variant) softer side wall, compliant ride, 32 psi is fine, increasing pressure just worsens the ride for no reduction in tram lining, these tram line quite badly (but not as badly as Falkens).

Rears are SC3 265 35 18 95y(?) in MO again. The rear is fine, and was the same tyre fitted while both Audi and Mercedes sc3 variants where on the car.
This isolates the problem to the Audi construction tyre IMO.

The tread pattern is exactly the same, with no exception. The best handling tire for tram lining of the 2 was the wider MO version, with an apparently stiffer side wall, assuming two plyes in the side wall is stiffer. But I don't know if two plyes of one material would naturally be stiffer, than one plye of another. That would depend on the material, something I am not familiar with, obviously.

Hence this thread.


Basically just trying to understand tyre construction and why they choose the construction combinations they do.

But as you say, I don't think we will come up with any usable info this way.

I would be interested to see how the Dunlop tt are made though. The sport maxx and sport maxx tt give an exceptionally planted feel to the car. Tt now replaced by the RT.



But my over riding confusion is, the narrower, softer(?) sidewall variant of sc3 handles worse re tram lining. Me no undystandy. Other than they are clearly designed for different cars.

Moral of the story, if you find a tyre that works for you, stick with the bloody thing, and don't let the tyre shop sell you the next best thing. As it ain't the same.


(main reason for sticking with sc3 is for mileage, which the Dunlop lacks, otherwise it would be Dunlops, no problem at all)

[feeutfo]

@ TheBoy, your previous TT have huge levels of grip in they're 10k life.

ANYTHING you fit that's a road summer tyre will have less grip. Sc3 / 5 included.

[YZ250]

what size do you actually have fitted at the moment ?

I am almost one million % certain it's not to do with width. Eg

245 x 45 x 18 sc3 mo (Mercedes variant) firmer by feel, harsher ride when cold, accepatble compliant ride when warm, run at 28psi to get heat into them and soften the ride, no tram lining at all. Absolutely rock solid. Even with both edges of the fronts worn away...................

I used to think that wide low profile tyres would always tramline but how do I explain why 235/45/17 on the Omega tramline badly but 255/30/19 on the bimmer don't. I would love to swap the wheels from the Omega to the bimmer and vise-versa to prove a point but pcd is different so I can't.

Edit:
When I say to prove a point, I mean that I believe the Omega is more susceptible to tramlining due to other geometries. 

[2woody]

I think I've got some sort of answer - are you sure that the two fronts you've had are 245/45 x 18 and 235/40 x 18 ?

As you know, the Omega B suspension is designed around tyres with 11.8 inches hub height. so that means that the roll centre and ground-level offset will be correct as long as you maintain this dimension. Happy handling territory.

Your 245/45s are quite a long way from this - half an inch height-wise to be precise, which is as good as a mile in suspension terms. They are also almost five percent bigger in rolling radius, too - this will certainly increase your braking distances as it'll confuse the ABS.

My considered opinion would be that its very difficult to find a 235 tyre of the appropriate size which won't tramline. And that your inappropriate ( sorry Chris ) size mitigates the tramlining, possibly by extending the ground-level offset and thereby giving more self-correcting torque.

Don't forget that the Omega B front suspension is almost identical to Omega A - so the tyre that they had in mind when they designed it was a 165 x 14.

245/45 x 18 = 780 wrpm & 12.3 inch hub height
235/40 x 18 = 820 wrpm & 11.8 inch hub height

265/35 x 18 = 823 wrpm

Also, the less height (in mm) in the sidewall means a stiffer tyre

[2woody]

I used to think that wide low profile tyres would always tramline but how do I explain why 235/45/17 on the Omega tramline badly but 255/30/19 on the bimmer don't. I would love to swap the wheels from the Omega to the bimmer and vise-versa to prove a point but pcd is different so I can't.

Edit:
When I say to prove a point, I mean that I believe the Omega is more susceptible to tramlining due to other geometries. 

that's easy - the BMW suspension is a far, far more sophisticated design. Key in that is the rack mounted in front of the suspension, which makes it all so much easier.....

[feeutfo]

I think I've got some sort of answer - are you sure that the two fronts you've had are 245/45 x 18 and 235/40 x 18 ?

As you know, the Omega B suspension is designed around tyres with 11.8 inches hub height. so that means that the roll centre and ground-level offset will be correct as long as you maintain this dimension. Happy handling territory.

Your 245/45s are quite a long way from this - half an inch height-wise to be precise, which is as good as a mile in suspension terms. They are also almost five percent bigger in rolling radius, too - this will certainly increase your braking distances as it'll confuse the ABS.

My considered opinion would be that its very difficult to find a 235 tyre of the appropriate size which won't tramline. And that your inappropriate ( sorry Chris ) size mitigates the tramlining, possibly by extending the ground-level offset and thereby giving more self-correcting torque.

Don't forget that the Omega B front suspension is almost identical to Omega A - so the tyre that they had in mind when they designed it was a 165 x 14.

245/45 x 18 = 780 wrpm & 12.3 inch hub height
235/40 x 18 = 820 wrpm & 11.8 inch hub height

265/35 x 18 = 823 wrpm

Also, the less height (in mm) in the sidewall means a stiffer tyre

lost me half way through from mitigates.

Just to confirm, the best handling tyre was the mo 245 45 18, then Audi 234 40 18 was next best. The worst ever was a Falken 912 in standard size. (replaced by sc3 generic which where good, but not as good as the biggest size of the mo, which is best.)

So on that evidence, the best handling was furthest from standard, the worst was the Falken on standard rims and sizes. 235 35 17 is it? 

I'd concede the biggest tyre size might well have failings in lateral grip or some other area related to geometry and roll centres, but the plain fact is IME.. The biggest tyre of the lot tram lined the least.

[feeutfo]

Also,I am unable to detect any difference in the abs trigger point between the two sizes.

I think this may be down to a lack of rebound in the b4 shocks. It triggers early it seems.

But we are getting off topic now.

[2woody]

tyres are just like that I'm afraid - that's what I mean about even tyre companies not knowing.

The Omega B facelift design team will have spent a great deal of time auditioning tyres from different manufacturers until they got one that tramlined the least. An OE fitment tyre that you just can't buy. Couldn't ever buy, probably.

So, you're back to auditioning different makes and tread patterns until you find one that suits.

the larger tyre is way too big - I'd be worried about the braking issues primarily.

just out of interest, what offset are the front wheels ?

[2woody]

how did you get 245/45 x 18 inside the standard strut - I tried that on the race car ( mainly because I had several sets of free tyres ) but couldn't get them to fit.

[2woody]

Also,I am unable to detect any difference in the abs trigger point between the two sizes.

I think this may be down to a lack of rebound in the b4 shocks. It triggers early it seems.

might be something to do with the 265s on the rear.

[feeutfo]

tyres are just like that I'm afraid - that's what I mean about even tyre companies not knowing.

The Omega B facelift design team will have spent a great deal of time auditioning tyres from different manufacturers until they got one that tramlined the least. An OE fitment tyre that you just can't buy. Couldn't ever buy, probably.

So, you're back to auditioning different makes and tread patterns until you find one that suits.

the larger tyre is way too big - I'd be worried about the braking issues primarily.

just out of interest, what offset are the front wheels ?

Et30 they are omega sport stars. Again, I was unable to find any fault with these, or with the previous sport stars that where the vectra offset, Et39 is it?, with the exact same tyres fitted. IMO the offset made absolutely no difference at all, other than the vectra et39(?) sat too close the strut, ,earning tyres with rim protection rubbed slightly.

The handling(tram lining) was not an issue with either offset.


I remain convinced its a tyre construction Issue tbh.



Re reading my posts, I'm coming accross a bit abrupt, Appologies if so, just trying to keep it factual.

[feeutfo]

how did you get 245/45 x 18 inside the standard strut - I tried that on the race car ( mainly because I had several sets of free tyres ) but couldn't get them to fit.

There's loads of room on et30. Et39(?) is too tight. Can't remember the standard 17" offset.

[feeutfo]

Also,I am unable to detect any difference in the abs trigger point between the two sizes.

I think this may be down to a lack of rebound in the b4 shocks. It triggers early it seems.

might be something to do with the 265s on the rear.

no the rears where fitted when I had both mo and Audi variants on the car. Plus driving it, it's defo the front.

Only issue at the back is the slop in the void holes in the rear donuts. Soon to be fixed with poly.