Author Topic: Tyres  (Read 13427 times)

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Offline BigMike

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Re: Tyres
« Reply #15 on: September 03, 2010, 07:11:20 AM »
Ok, sorry, they must be a 15x7 then. They are the wheels on Chee's car. He is getting new wheels and doesn't need his old ones anymore
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Offline Sirdeuce

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Re: Tyres
« Reply #16 on: September 03, 2010, 11:01:49 AM »
15x7 work fine!
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Offline Sirdeuce

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Re: Tyres
« Reply #17 on: October 08, 2010, 10:05:49 AM »
Put a set of Pirelli P-Zero Nero's on the Mazda. The car HATED these tires!! On stretches that we normally travel at 65 to 70 MPH here on the hill, and never invoke the interference of the stability control gods, the DSC was like a Christmas light in the dash! The gods of stability were verry angry! At 35 to 40 MPH on the same section of road the DSC would throw a fit and prevent any speed above 40 MPH. I thought the suspension was falling apart! Felt like the sway bars had magically disappeared! I took the car to Mazda to have it checked out. Yes the front struts are leaking, but that was not the problem. I put the tires we had on before, BFG G Force Super sport,  and the difference was night and day! The struts are on order, so they haven't been replaced. I drove the car home from Lithia and it actually drove right! I was able to drive my normal speed without any complaints from the car. I did push it through an 'S' turn to see if I could get the attention of the stability gods, and they let me know they were still there with a little bit of brake in the beginning of the S. I was traveling at a speed closer to stupid than safe, but it was just a little nudge from the DSC that I was looking for. Now we have 2 tire makes blackballed from the Speed 3 club, Yokohama and Pirelli. They may be good tires, but the little blue Mazda just doesn't like them at all. Two things on this planet you have to keep happy! Your woman and your car! Which one you put first is up to you, but always say the woman is first!
"I slept with faith and found a corpse in my arms on wakening; I drank and danced all night with doubt and found her a virgin in the morning."

Offline Sirdeuce

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Re: Tyres
« Reply #18 on: December 17, 2010, 09:55:37 PM »
I was looking at the Falken Azenis RT-615K tires. The 195 60 14 are 23.2" tall with 900 RPM, The 205 50 15 are 23.2" tall but have an RPM of 895. I don't think it's much of a difference, but................
I'll look around some more.
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Offline BryanH

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Re: Tyres
« Reply #19 on: December 18, 2010, 02:03:01 AM »
That aren't a significant difference.  We'll want the extra width not only for grip but for heat dissipation as well.

Offline Sirdeuce

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Re: Tyres
« Reply #20 on: December 18, 2010, 09:29:58 AM »
I'm not too concerned about speedo accuracy. We don't need to know the actual speed, just need a reference. I'm sure most of us can judge our entry by feel and sight. But when fatigued, you knoow judgement can get skewed. Really would like to get a 205 or 215 45 15 though. One problem we might have is in rim width. I prefer being a little wide over a little narrow. Going narrow allows more 'swing' , feels sloppy. the rims I have are 15X6.5 or 7. 6.5 is perfetct for a 205, ahair wide for 195 and just on the narrow end of what 215 fits.
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Offline Sirdeuce

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Re: Tyres
« Reply #21 on: December 18, 2010, 09:30:45 AM »
Bryan, how are your feelings on staggered fitment on the AW11?
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Offline BigMike

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Re: Tyres
« Reply #22 on: December 18, 2010, 11:40:11 AM »
Got a problem with our free 15" rims: They are gone. Chee sold his car and with it the rims we were gonna use (at no cost).

So we need to come up with another set of 15" rims -- and preferably two complete sets so we can have one set fully mounted on stand-by. Bill, we can borrow the 15" rims on my mother's Saturn for the weekend (but if we jack them up I'll have to replace them lol).

Bryan, how are your feelings on staggered fitment on the AW11?
Having a square setup will be good for rotation, but if we had a staggered arrangement, we could still rotate between two sets of tires :idea:

Sears Point is a higher average speed track than Buttonwillow, correct?
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Offline Sirdeuce

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Re: Tyres
« Reply #23 on: December 18, 2010, 12:03:02 PM »
The size of the rims on your mom's car are 15X6.5 I think. Could you double check  that? We could use mine,  but we need to make sure the sizes are the same. But for this race, at our level, may not be such an issue.
 
Infineon is faster, with a bit of elevation change. I think the biggest problem will be the long sweeping turns, the MR2 needs a constant speed through long sweeps to keep the weight balanced. Too slow it'll be in the way of faster cars, too fast and the weigh in the rear gets the best of it. At speed , letting off the throttle the rear will want to pass the front, getting into the throttle will make it push. Doing the old in and out on the throttle will be a lesson in ballet dancing. Top of the hill is a right hander that gets light. Little car will want to do a little break dancing there. Learn the breaking points well, and corner personalities and you could fly through it! Although the elevation change would be a bit easier to handle with shorter tires, or with more engine torque. Hmmmm, 7AGE?
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Offline BryanH

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Re: Tyres
« Reply #24 on: December 18, 2010, 12:15:30 PM »
IMO tire/wheel stagger isn't necessary on the AW11 until you start making a lot of power or torque.  A hint of stagger will work fine (10mm) at <150hp but more than that and the car will push too much. 


Offline BigMike

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Re: Tyres
« Reply #25 on: December 18, 2010, 02:37:44 PM »
Could you double check  that?

the MR2 needs a constant speed through long sweeps to keep the weight balanced. Too slow it'll be in the way of faster cars, too fast and the weigh in the rear gets the best of it.
I don't know if Bill & Kevin's old AE86 wasn't tuned properly, but I remember playing in the hills with Kevin and he said he couldn't compete with the high speed constant cornering of my MR2. I could take constant velocity corners at a higher speed than the FR Corolla could. However, when we ran Trimmer Springs from North-to-South, right before we dropped into the Trimmer Springs Forest Station, there are some very tight and slow twisty section that I couldn't keep up with Kevin for the life of me. I had plenty of power, but the faster I tried, the more the car pushed in the slow speed corners.

So my experience with the MR2 has been a very stable at high speed cornering and a big tendency to understeer at low speed corners.

Although the elevation change would be a bit easier to handle with shorter tires, or with more engine torque
Don't forget the 6 speed!!

Infineon is faster

A hint of stagger will work fine (10mm) at <150hp but more than that and the car will push too much.

The reason I asked if the track was fast was regarding understeer. To comment on Bryan, if we lack the torque to induce oversteer, what if we ran 205s in the front and 195s in the rear? I know, opposite for what you'd expect with a rear-heavy car, but I'm just thinking out loud.

I know the slanted radiator with air coming through the hood and over the car (instead of under) will help with down-force and consequently improved front traction at high speeds.

I also really want to make some simple front canards out of sheet metal. This will help immensely with front down force

Picture 1 & 2: Here is a canard example on an Elise

Picture 3: Here is a double canard example

Picture 4: Look at the canard on this BMW. This is what I had in mind for our car. What do you guys think?

Don't talk to me about how fragile the car will be and it will get damaged. If you saw the amount of plywood aerodynamics that we saw out there this is nothing.

Besides, the whole concept of building them as simple as possible out of sheet metal applies to us bringing a couple back-up sets that can be quickly swapped on.

Picture 5: This is how Lotus positions the radiator on the Elise. Completely flat to my surprise :o Not to say we need to do this, just food for thought
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Offline BryanH

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Re: Tyres
« Reply #26 on: December 18, 2010, 07:36:49 PM »
The reason I asked if the track was fast was regarding understeer. To comment on Bryan, if we lack the torque to induce oversteer, what if we ran 205s in the front and 195s in the rear? I know, opposite for what you'd expect with a rear-heavy car, but I'm just thinking out loud.
Worked a treat for my stock '87 NA on Konis and race tires at an autox.  With the higher speeds of a track, it's more than likely too much oversteer.  Especially if you guys double up the rear sway bar like we talked about a while back (remember my '87 had no rear bar). 

Speaking of sway bars, I actually liked the softer (stock) set up better on lowering springs and increased negative camber.  I had stiff sway bars on the car for a while and I don't think it was any faster.  The trouble was twofold - one, you had no idea which end of the car would grip and which end would slide when entering a corner.  And two, using the curbs on a track was more difficult because the car was upset more.  The sway bars reduced the independence of the independent suspension in other words.  I had an ST front bar (I forget the size now) and a prototype H&T rear bar (19mm solid -- waaaaay too stiff!).

We'll have to control roll somehow though.  Otherwise we can have tons of static negative camber turn into zero (or positive) camber on the outside wheels when loaded up in a corner.  I know a good budget track solution was ST springs years ago but they probably aren't in a LeMons budget anyhow. 

Offline BryanH

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Re: Tyres
« Reply #27 on: December 18, 2010, 07:42:49 PM »
To expand on sway bar experiences a bit, on the MK2 in Stock class autox the car gets faster the more front bar you put on it.  One theory is that the stiff front bar controls roll well enough to reduce the dynamic camber loss of the McPherson struts, and thus gives more front grip while also adding stability by planting the rear tires.  On paper it sounds like a recipe for huge push but it works extremely well.  Of course it helps to run zero rear toe (or even a bit of toe out) to get the car to rotate better off throttle. 

In general sway bars actually reduce grip, and are seen as more of a quick fine tuning device in racing where springs and dampers are very well developed.  This specific case is probably an exception.

Stability is good.  It keeps us consistent on track without having to work as hard in the cockpit.  The trick is to have a stable handling car without it being a push pig. :)

Offline BigMike

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Re: Tyres
« Reply #28 on: December 18, 2010, 10:31:15 PM »
Great discussion :thumbs:

We could just run the stock rear bar which is really small. I've got one on my 2 & I have no clue what it does or doesn't do for me :ha_ha: I should remove an end link for a couple of days just to see what the difference is.

Stability is good.  It keeps us consistent on track without having to work as hard in the cockpit.  The trick is to have a stable handling car without it being a push pig. :)
I completely agree with this. If we the drivers are having to concentrate to drive the car quick, and quick we may be, we'll fatigue out and then spin out :driving: :bricks:
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     My 1987 Supercharged 4A-powered 6-speed MR2