996 GT3 floaty/unstable feeling

996 GT3 floaty/unstable feeling

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911p

Original Poster:

2,298 posts

139 months

Tuesday 11th March 2014
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That's the problem, it's not primarily a track car and full on semi-slicks bring many compromises.

AD08Rs are very highly praised for 996 GT3s on US forums like Rennlist. I always agree with 'you get what you pay for' - these are more expensive than the MPS2s which come standard on the car!

I don't believe that 3mm of extra tread was cause this much trouble, especially taking into account the tread pattern these tyres have smile

911p

Original Poster:

2,298 posts

139 months

Wednesday 12th March 2014
quotequote all
Definitely smile

We trust Chris will find all of the causes anyway (if it is more than just the dampers), he'll be able to feel what it's doing on those test drives he does!

Orangecurry

6,466 posts

165 months

Wednesday 12th March 2014
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Without even having seen the car, I would still say that the dampers, although critical, do not work as hard on the very-smooth track, and unless they all failed wouldn't cause a general 'floaty' feeling.

911p said:
I don't believe that 3mm of extra tread was cause this much trouble, especially taking into account the tread pattern these tyres have smile
But it's amazing how much extra heat will be generated in that extra 3mm, no matter how few 'blocks' there are in the tread pattern - heat = expansion = floaty.

All from the comfort of my armchair. hehe

At Goodwood last year I treated my Vredesteins (road-biased) like I treated my Bridgestones (track-biased) the time before. With similar pressures, once fully warmed I had bad vibration with the Vreds to the level that I thought one of the wheels was about to fall off.

Dropping the pressures lower than I usually do fixed the problem completely.

Tyres eh? Can't live with 'em and you can't live without 'em.

james S

1,613 posts

204 months

Wednesday 12th March 2014
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What a pain, it must have spoiled your day.

It may well be the shocks, but in my experience the car drives shockingly on the road when the shocks are giving up. It can fear dangerous even at modest speed on all but the smoothest surface and particularly so in a dip. My fronts were were than my backs, but at Brands I would have felt it the most exiting Paddock as the front would have been bouncing around all over the place - like a clown car!

How any miles has it done since visiting CoG? If its only a few miles ago, its hard to imagine they would have completed all their detailed work if the rears were just about to give up the ghost

However tracking a car on newish types with deep tread blocks squirming about can be a very unsettling experience indeed. More so than you might imagine if you haven't experienced it before.

As this is the only thing that's changed, it would be my umber one suspect. But as ever, best to let the experts sort it


nsm3

2,831 posts

155 months

Wednesday 12th March 2014
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When I swapped my Exige Yokohama track tyres for some Toyo road tyres, you would have thought the steering and suspension had somehow become disconnected, the extra wallowing was extremely marked, especially in fast sweeping corners and hard on the brakes.

However, I soon got used to it and enjoyed the extra wet weather grip, back end out-ability, ride compliance and £300 all corners replacement costs smile

911p

Original Poster:

2,298 posts

139 months

Wednesday 12th March 2014
quotequote all
Orangecurry said:
Without even having seen the car, I would still say that the dampers, although critical, do not work as hard on the very-smooth track, and unless they all failed wouldn't cause a general 'floaty' feeling.
Have you driven Brands? The straight and the corner that leads onto it pitch and dip quite a lot!

Orangecurry said:
But it's amazing how much extra heat will be generated in that extra 3mm, no matter how few 'blocks' there are in the tread pattern - heat = expansion = floaty.
I do hear what you're saying smile

But then I'd question why nobody else has ever mentioned problems like these, with these tyres or other with the same tread depth such as MPS2 or MPSS.

As you can see I'd like to believe it's not the tyres that just cost £1k causing all the problems hehe Do appreciate the responses though.

Orangecurry

6,466 posts

165 months

Wednesday 12th March 2014
quotequote all
I absolutely hear what you are saying, but pulling the car apart again after a short period since CoG gave them the green light would not be the NEXT step for me. Run the Yokos, experiment with pressure.

Personally I'd source another wheel set, and have dedicated tyres for both purposes.




911p

Original Poster:

2,298 posts

139 months

Wednesday 12th March 2014
quotequote all
If you are correct though, I'm still questioning why there's absolutely nothing else to be found online about the feel of any car being adversely affected by these tyres.

It certainly is a strange one!

james S

1,613 posts

204 months

Wednesday 12th March 2014
quotequote all
There may be nothing about the brand of tyres, but the problems of deep tread on track is very well recorded. What depth of tread did you have, and did it get better as the tread wore down, which is does rapidly on deep treads.

Overall though internet speculation probably isn't the best here

911p

Original Poster:

2,298 posts

139 months

Wednesday 12th March 2014
quotequote all
They would have had near enough the full 8mm of tread at the start of the day, as I say they only had a few hundred miles on them so were pretty much new. I don't think it really improved throughout the day, although I don't think they would have worn down much over the course of the day.

boxsey

3,481 posts

169 months

Wednesday 12th March 2014
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911p said:
If you are correct though, I'm still questioning why there's absolutely nothing else to be found online about the feel of any car being adversely affected by these tyres.

It certainly is a strange one!
Going on the responses so far, that's probably because there doesn't seem to be any UK GT3 track day regulars using these tyres. I believe you've found them to be very good on your MX5 and that was a main reason for trying them on the GT3. With such big differences between the two cars it was never going to be a certainty that the tyres would behave in the same way. The MPS2 and now the supersports, are used by many 911 owners that want something that is capable to do the odd track day i.e. they're a tried and tested option where as there's not much info about how the Yoko AD08 performs for track work with a GT3.

LaSource

2,469 posts

167 months

Wednesday 12th March 2014
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I agree with the OP. Plenty of examples of AD08s on GT3s. No adverse reports.
Interestingly the AD08r is relatively new. Though it is mainly a compound change. Perhaps the AD08r is softer compound and hence more movement when new?

Calling NXI20 shout


LaSource

2,469 posts

167 months

Wednesday 12th March 2014
quotequote all
I agree with the OP. Plenty of examples of AD08s on GT3s. No adverse reports.
Interestingly the AD08r is relatively new. Though it is mainly a compound change. Perhaps the AD08r is softer compound and hence more movement when new?

Calling NXI20 shout


911p

Original Poster:

2,298 posts

139 months

Wednesday 12th March 2014
quotequote all
This is why I'm stumped. Plenty in the US using AD08s on their GT3s without any issues.

Rennlist - Yokohama AD-08 R
Rennlist - Texas World Speedway Sept 29th

Orangecurry

6,466 posts

165 months

Wednesday 12th March 2014
quotequote all
Ask them what pressures they run when they go round their ovals.

911p

Original Poster:

2,298 posts

139 months

Wednesday 12th March 2014
quotequote all
Orangecurry said:
Ask them what pressures they run when they go round their ovals.
hehe

nxi20

743 posts

164 months

Wednesday 12th March 2014
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I've used AD08 (not the R) as a wet tyre & also done Spa & the 'ring in the dry on them in my GT3. While not being anywhere close to Cups in the performance stakes, they do have benefits over, say, PS2s. They can handle cold & water reasonably well & they are more heat stable than PS2s. I run them as road tyres on my GT2 rep & they are absolutely fine in that role too. They are quite a hard compound though so you need to get a fair bit of heat in them to make them grip. It's a job getting slicks up to temp in the current conditions so that might be a factor too.

Without driving the car it's incredibly difficult to diagnose the behaviour at a distance. Is this the first time that you have changed brand of tyres since you've had the car? All tyres have characteristics unique to each. I can't remember too well at this distance what the AD08 was like on track but I'm wondering if you are simply feeling the tyre move about under load & you're not used to it? 32/35 hot is definitely in the right zone pressure-wise. All inflating to 39 will do is reduce the contact patch which might make it feel like the tyre is moving less. I establish my base pressures by probe pyrometer which is the only real way of optimising them scientifically - sometimes using a different pressure can "feel" better but you will be compromising wear & grip.

911p

Original Poster:

2,298 posts

139 months

Wednesday 12th March 2014
quotequote all
It is the first time we've moved away from PS2s. I must emphasise that all of these feelings were only apparent over the bumpy parts of the track, on the smooth parts the car felt fine other than being a little more unstable than usual under braking.

Dave Thornton

206 posts

108 months

Thursday 13th March 2014
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Something I've found recently (not on a 911) was a tyre going 'out of round'. Not detectable with the eye when the car is stationary, but mount a camera on the car and film the wheel at 30mph and you can see if it's completely true - do this for both sides and compare and you might just find something not right.

nxi20

743 posts

164 months

Thursday 13th March 2014
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911p said:
It is the first time we've moved away from PS2s. I must emphasise that all of these feelings were only apparent over the bumpy parts of the track, on the smooth parts the car felt fine other than being a little more unstable than usual under braking.
So probably down to the differences in tyre construction. A GT3 driven hard on a bumpy track should move around under you; that's not a bad thing! It's unrealistic to expect a magic carpet ride from tyres with a stiff sidewall & relatively tall tread blocks. The feel will improve when the track temps come up & you can get the tyre temps closer to 60+ degrees.