More grip than Dunlop RT

[chrisgixer]

Why does a tyre become sufficient for a certain car/bhp or brake package though? We are taking lateral load after all.

 

Description might suggest a differant driving style, more aligned with power and brakes, rather than corner speed. You guys appear to be talkng about throttle and brakes alone and being happy with tyres that suit those two directional forces, and those alone. To a certain extent.

 

There is, dare I say, I third axis to consider when buying tyres. Imo ate least. Is that fair to say?

 

 

For example.....Can you tell me if the front or rear lets go in a corner (mid corner) first, or both together?

 

 

Omega has;

Front. 30mm drop Irmscher springs, Bilstein b4 shocks. Poly front bushes. Oe rubber rearward bushes, as no poly exist for these. Heavy duty top mounts. Poly roll bar bushes.All less than two years old.

 

Rear 15mm drop mv6 rear springs. (More than 20mm and settings not achievable)

Bilstein b4 shocks. Poly rear subframe bushes. LSD.

 

That's not say there aren't improvements to be had somewhere though.

[liner33]

No updated arbs? What are the spring rates stock and now

 

If you can't keep the tyre planted then you can't utilise the tread width meaning you get a diminishing return by fitting wider tyres

 

Accurate static geometry settings will mean little if the dynamic settings go all awry

[chrisgixer]

No, arb's are stock. I see no need to upgrade these, given gm use the same part accross the range from soggy soft Elites, through standard suspension on cd and cdx up to the much firmer sprung mv6. Same arb on all models. Body roll is much improved with firmer suspension.

 

Further. TheBoy, who posted earlier, has no such under steer issues on his omega. Very similar suspension set up. Same polys, springs, and front wheels. Wim set up. His wheels are the same width front and back. Same tyres front and back.

 

So why no under sterring on his?

[Tony]

Tyre coefficient saturation limits has many factors including factors like weight transfer, polar moments and with the Omega moment of inertia which is very similar to the Honda S2000. Understeer corner in would suggest moment of inertia, corner on weight transfer, corner out polar moment.... The driven solution is corner in ( slow down ) corner on ( change the tyre pressures/ coils ) corner out ( don't power on to soon )  One factor you miss between TheBoy and yourself is the driver, as far as we know he might drive like grandma and you drive like you stole it so it's hard to compare.

[TheBoy]

One factor you miss between TheBoy and yourself is the driver, as far as we know he might drive like grandma and you drive like you stole it so it's hard to compare.

 

Thats me. A model driver. Miss Daisy  .  Thats the nicest, kindest thing you've ever said about me Tony

 

 

For the benefit of others contributing on this thread, whilst I'd like to claim I'm a bit steady, I'm afraid that might not be the truth.  I usually get around 10k from a set of tyres, and about 5k from front pads. Not something I'm proud of, but thats reality.

 

Having been in the car with the OP, I'd suggest our styles are not a million miles apart

[TheBoy]

I would add, IMHO, the Omega in standard form does have a natural tendency towards high speed understeer, and with chrisgixer fitting 265's at the rear, thats only going to highlight that further, as he will be able to get the power down earlier and harder due to better traction, and the rear will hold on better in a bend, where my 235's will start to break away at the back (and front at same time, as both of mine are pretty well balanced, thanks to Tony's hard work all those years ago).

[parthiban]

I would add, IMHO, the Omega in standard form does have a natural tendency towards high speed understeer, and with chrisgixer fitting 265's at the rear, thats only going to highlight that further, as he will be able to get the power down earlier and harder due to better traction, and the rear will hold on better in a bend, where my 235's will start to break away at the back (and front at same time, as both of mine are pretty well balanced, thanks to Tony's hard work all those years ago).

 

This seems sensible, it looks as though the better rear grip is highlighting the Omega's chassis deficiencies as the rear is allowing you to put more power down which is overwhelming the front.

[Tony]

"Thats the nicest, kindest thing you've ever said about me Tony" ..... Wider tyres does not mean better grip though that's a myth. All that changes is the type of footprint not the size of the footprint

 

 

Weight distribution in the wet works much better with narrow tyres that concentrate the contact patch, look at ice racing for example their tyres are like bike tyres.

[parthiban]

Surely that's not true Tony? Assuming the same profile a wider contact patch means a larger overall contact patch?

[Tony]

No it's wider but more narrow, agreed this is good for grip during cornering ( lateral traction ) but the braking and thrust is impaired.

[parthiban]

No it's wider but more narrow, agreed this is good for grip during cornering ( lateral traction ) but the braking and thrust is impaired.

 

What do you mean wider but more narrow? 

[Tony]

As shown in the image....A wider tyre adds lateral grip in the dry but not longitudinal grip.... Some might say well hang about a drag car has super wide tyres and they go 300mph, well yes but centrifugal force reduces the tyres contact patch hence the static width.

[chrisgixer]

Undoubtedly though, the single most obvious differance between mine, and TheBoys, is the wider rear.

 

The single most obvious differance in the way the cars drive, is understear on the limit. And the limit is prety much in the same place on both cars, as he looses traction at a similar place in the same corner, yet I'm able to get on the power a bit earlier. ....And my rears don't let go.

 

Same set up target settings. Very similar suspension components. Same model, engine, and year. Etc etc....

 

 

 

I see what Tony is saying re width and actual size/area of contact patch, given the same weight. Taking the equation away from my particular car for a minute. Would that imply a lower tyre pressure would work, generally speaking, given the same weight?

Edit to add;

Lateral grip is indeed enhanced I think it's fair to say. Grip on the power might be compromised but there is room for leeway there's as its only 218bhp. ....so far looking to at least double that with the v8.

[Tony]

I think pressure manipulation + - a few PSI is a wise starting point..... Down on the front to oversteer or up at the rear and -V- for understeer. At the end of the day the tyres get final contact so manipulation of the patch is a great tool but within reason.

[chrisgixer]

 

No it's wider but more narrow, agreed this is good for grip during cornering ( lateral traction ) but the braking and thrust is impaired.

 

 

What do you mean wider but more narrow? 

Take a car of a given weight. Remove the wheels and fit say, a shopping trolly wheel. Much smaller area. Car will sink into Tarmac much more on a hot day than a much the much bigger road tyre. Much like quick sand. Stand up in quick sand, you sink. Spread your weight, lie down, and spreade your arms and legs, you stop sinking.

 

Now fit the same wider tyre I have on mine. Wider area, BUT to compress the wider tyre to give the same for and aft contact patch as the narrower tyre, due to the way the tyre is constructed, you need to either increase the weight, or as my question, decrease the pressure. ....?

[chrisgixer]

I think pressure manipulation + - a few PSI is a wise starting point..... Down on the front to oversteer or up at the rear and -V- for understeer. At the end of the day the tyres get final contact so manipulation of the patch is a great tool but within reason.

Currenty running 33psi rear. Wear is possibly more concentrated in the middle. Trailing arm rear suspension

 

31psi front. Wear is more concentrated in the edges. But then it's mcphurson strut suspension with a wider fitment.

 

These omegas are known for more camber deflection on the front, (as I'm sure I don't need to explain to Tony) as I understand it, so "normal wear" tends to give flat in the middle rears, and rounded fronts with all the wear on the edges, with very minimal wear in the middle of the front tread. I think it's accepted that if you can keep the front wear even throughout the tyres life, with a fraction more in the inner edge, then you have the set up at the best compromise.

 

It can take a set of front tyres to see how well your doing, re driver style etc v camber setting to find the wear level required. I must admit I haven't checked the tyre wear for a month ish, but last I looked it seemed " normal " given the above.

[Tony]

Grip is like a budget, you use what you have given the situation. A narrow tyre in the hot dry weather is not efficient and will obviously saturate faster than a wider ( narrower ) footprint of a wider tyre, whereas when grip is diminished in the likes of snow and ice then the concentration becomes much more intense on the narrow tyre rather than distribute the weight over a wider area.

 

Tyre pressure distorts the footprint, low offers a more oval contact patch and high a more linear patch. One of the problems i/ we have with the Omega is the front suspension is so fluid? The suspension stroke on lock during weight transfer moves the tyres contact patch so extremely it's hard to maintain a decent level of grip. Agreed changes in the geometric positions would help but in truth they would be sacrificial to the tyres meaning i could make the car stick like s**t but your tyres would be a distant memory.

[chrisgixer]

Or.... Fit a softer tyre with more grip.

[Tony]

Simple solution but mileage would be an issue which is not end of days providing the cost reflects that. Point to note on the softer compound is the Omega's weight? Lateral forces in hot weather can make the tread laminate, a condition in F1 they call marbling.

[chrisgixer]

I'd look to control that with pressure to an extent. If that's reasonable, to a point...? Although I'd not expect go see that's sort of sustained side load on the road. Track yes.

 

I do adjust psi several times through out the year to allow for ambient temp. And ride quality. The ride gets noticeably firmer as the temp drops. The noticeable change level seems to be 20c. Above that the ride is supple and compliant with good grip and the car tracks well. Below that, have to drop the pressures to achieve the same.

 

Below 8c it's all out of range no matter what. It feels a bit harsh and comparatively scitish this time of year. I'm still love driving it though, dont get me wrong. But the effect is noticeable.

 

 

Should add, the ride quality v temp equation is more noticeable since fitting poly bushes. Which isn't altogether surprising given its pored into a mould hot at manufacture, and can be frozen in a household freezer to briefly to allow machining.

[chrisgixer]

Another thought occurs (and the initial question was so simple, lol) with the omega v8 project in mind, the car will not be dissimilar in set up to a vxr8 although that has a two inch wider body and presumably that applies to the track as well. Vxr8 apparently uses a much more upright front camber than omega.

 

Although I dont have a precise figure.

[Tony]

Poly bushes belay compliance which is a good and bad thing, good geometrically bad for harshness. As we know the Omega's weight needs much dampening hence the huge wishbone bushings and suspension stroke which is all well and good but by the time you factor in wear and tare any given geometric target is a bugger to conclude.

[chrisgixer]

Michelin pilot super sports 245 40 18 mo fitted to the front. Over steer returns.

 

 

But the rear sc3 are now due for replacement. So we'll see.

 

Very impressed with Mpss so far. Stable, quieter, more grip, minimal unwanted feedback, more grip, compliant, more grip, and reasonably priced.

 

Oh and did I mention, more grip? Even more than a Falken.

[Tony]

What are they like for noise?

[chrisgixer]

Better than sports contact 3. Which I think are 72db on the label.

 

Mpss are 70/71db iirc without looking. On a par with Dunlop RT.

 

So as the label really. Not brilliantly quiet, but better than some. And better for me given the old ones.

 

Still well happy. Just not sure how well they will last, can't give great mileage with this grip level... Can they?