Excessive Tyre Wear

[pdsman53]

Hi Guys,
I have an NA '94 MX5...for Track Days only (Wakefield/SMSP/Marulan/Luddenham).
The $'s are somewhat limited.
Pretty much, a stock 1.8 BP...(but, future plans for extra ponies)
Suspension has aftermarket Swaybars (Front 29mm-Stiff, rear 14mm-Soft) and Coilovers (hard setting).
I put Extended Lower Ball Joints on, to maximise Camber (grip).
Current Wheel Alignment
...front 4 deg camber, 1.5mm...total ToeOut
...rear 3 deg camber, 2.5mm...total ToeIn
205_45_16 Federals... pressures...28 psi cold (get to 35/36 and back off to 33)
My question is:
Grip is OK and times very consistent, until the laps start piling up (up to 125 laps in the day)...(gotta love MX5s).
But the Tyres are getting ripped on the 'inside'...too much Camber???
...OR....is it not properly utilising the camber???
Should I try softening the suspension, to get better utilisation of the Max Camber???...ie..Coilovers??, OEM Swaybars??
Your thoughts would be appreciated.
pdsman53.

[bruce]

125 laps! It's a wonder they're not bald.

[Magpie]

Toe is also excessive, why so much?

How are they ripped on the 'inside'?

[pdsman53]

Hi Magpie,
the last 2x track days, were at Luddenham...as you probably know, it's only 1.4km...tight and tough on tyres.
It's as if...the suspension is so stiff, that there's not enough weight transfer to get up on the tyre.
The tyres look like they have been running around the circuit on the inside of each tyre...only.
Sorry...wheels/tyres are elsewhere, so can't attach a photo.
Cheers,
pdsman53

[Magpie]

Inside suggests too much camber. Large camber on the track OK, but going in a straight line on the road is an issue, as is that much toe.

[pdsman53]

Thanks Magpie,
That's partly what I was expecting....re: camber.
So what do you recommend for toe settings, going forward....given that the budget is a compromise, on wheel alignment has to cover the 4x circuits.

For the next track day, I'll swap the tyres on the rims...just to get reasonable value out of them...I can do a reasonably accurate Toe alignment (String method).

I have access to some 15x6 ROH mags...which I'm considering swapping to, with a new set of 195/50/15 Hankook RS4s and the wheel alignment change.
They are heavier than the current 16x7 mags...that's my only worry...but is that a problem, if 3 out of 4 track days are on the tighter circuits.

What do you think.
Cheers,
pdsman53

P.S. Regardless, still having fun...but like everyone out there, just looking to get a little quicker...while utilising the bits underneath, to somewhere near their potential.

[The American]

Camber needs to be somewhat balanced with the roll stiffness (coming from both springs and anti roll bars) and the stickiness of the tyres used.

If you’re wearing the insides with heavy track use, perhaps something is preventing the car from ‘rolling on to’ the face of the tyre as the suspension loads: too much roll stiffness, or tyres not sticky enough.

Anytime I have seen Federal ‘semi slicks’ on a track car, they have been feathered/worn like a road tyre. I don’t think they generate enough grip to use high camber settings and stiffer suspension set up.

The toe settings at the front look odd to me

[Magpie]

Forgot to ask what tyre pressures? Any tyre temp informations?

[pdsman53]

I haven't got details for the last 2x outings a Luddenham, but have details for just after the ELBJs went on and the Wheel Alignment...for Wakefield, (which as you prabably know is more flowing (clockwise).

1st session...Tyre Pressures...29 (cold)
Tyre Temps...(3x across tyres).....(outside to inside).
LF....34,38,41 (36PSI) RF....41,37,31 (35PSI)
LR...41,45,49 (36PSI) RR....45,41,37 (36PSI)
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dropped pressure to 33 PSI
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2nd session
LF....40,47,50 (33) RF....41,40,34 (33)
LR...47,55,55 (33) RR...51,45,39 (33)
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a little bit too much Tail - so changed Front Sway Bar.....from Soft to Stiff
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3rd session.
LF...40,44,48 (33) RF...49,41,33 (33)
LR...46,50,53 (33) RR...48,44,38 (33)
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Still slightly taily, in a couple of corners - so changed Rear Sway Bar....from Middle to Soft
-----------------------------------------------------------------
4th session
LF...42,46,46 (33) RF...46,40,35 (32.5)
LR...52,54,52 (33) RR...47,47,41 (34)
-----------------------------------------------------------------
5th session
LF...40,49,51 (N/A) RF...47,42,34 (N/A)
LR...47,53,56 (N/A) RR...51,47,40 (N/A)
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Ambient temp, cooling right off..upped Front tyres (only) to 34 PSI
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6th session...upped Front tyres (only) to 34 PSI
LF...41,44,47 (34.5) RF...46,41,34 (34.5)
LR...41,47,50 (33) RR...47,44,40 (33)
================================================
Both changes felt like a slight improvement, with marginal time difference...but more consistent.

As you can see, the "inside" of each tyre, is getting a good seeing to....but at least after the 4th session the 'left' rear was getting closer.

The last couple of track days at Luddenham, were just 'fun' days (a couple of newby's on the last day)...so no data, I'm afraid....which is a pity

What do you advise...
pdsman53

[pdsman53]

Sorry,
I went back to my notes to check the timing of when the ELBJs/Coilovers went on the car.
In the last reply: at Wakefield, my notes tell me:-

I had Bilstein Shocks with Lowered Stiff springs...(they were on the car, when I bought it a few years back).
I'd fitted the ELBJs, new Federal RSRs, the wheel alignment (per earlier info), for that Wakefield meeting.
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It was after the Wakefield....I removed the Bilsteins/Springs and fitted the Coilovers....($$$ compromise...Green "HSD" coilovers).
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Since then....I've had 1x SMSP (anti-clock)....during which I had to raise the front Coilovers, due to lack of Wheel Arch clearance....(ie...possibly Rake.. 3mm higher at front now).
then, 2x Luddenham (clock)....obviously both slower/tighter circuits than Wakefield.
Coilovers....Setting....fully stiff.
No Data.....SMSP (in the ether somewhere), and I didn't get any for 2x Luddenham.

So, since the Coilovers went on.....I've seen the worst of the "inside" tyre wear....on the "tighter/slower circuits".
The Federals have now done 4x meetings...the last 2x at Luddenham (225 laps).
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For the next meeting (SMSP)....I was going to swap the tyres on the rims, just to get the last out of the tyres...maybe soften the coilovers.
Do a basic "string" change on the "front" Toe...back to "zero"
Do you recommend trying anything else??
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As I said earlier...I can get some free ROH 15x6JJ mags, I was going to put some new (195-50-15) Hankook RS4s on them and get a new less aggressive Camber alignment...for the following meeting.
They are a little heavier than the current 16x7's (205-45-16)....but the 15's will give a little more Wheel arch clearance (I can then get "rake" back).
The 15" will probably suit the shorter (SMSP/Luddenham/Marulan) circuits, but may suffer on Wakefields longer straights.
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Your thoughts please.
Thanks,
pdsman53

[1600Dave]

I think you're a little fixated on maximum camber being the solution to everything. You seem to have tried many different things with changing sway bars, suspension, etc but have kept the one thing constant (lots of camber) that I would have thought was the first thing to alter given your tyre temps / tyre wear.

Maybe try dialling a little camber and toe out of it and seeing what happens with the handling / wear compromise ?

[Magpie]

------------------------------------------------------------------
6th session...upped Front tyres (only) to 34 PSI
LF...41,44,47 (34.5) RF...46,41,34 (34.5)
LR...41,47,50 (33) RR...47,44,40 (33)
================================================

My thoughts:
LF - Pressure OK
RF - very slightly over pressure
LR - very slightly over pressure
RR - Pressure OK

You are slightly overworking the rears, possibly corner exit spinning the tyres or hard acceleration in places on the cool down lap.
You are overworking the left hand side, this could suggest roll issues or there were a lot of right hand corners on the cool down lap.

Most of the wear you are indicating could be caused not by the track but by the drive to and from. Take the car for a normal drive and take the temps/pressures then and see what they say. I guess the inside will be way hotter because of the excessive camber and toe.

By the way for your 3rd session the tyre temps support that the rear was being overworked. However you would need to understand the where and why. If on corner exit is it because getting on the power too early and causing the rears to work a lot harder (spinning) or because of a setup issue. Yes you made a setup change and there was a slight improvement but was the change to cover a driver error and the driver just kept doing what he was previously doing...

[pdsman53]

Thanks for your points of view guys.
Going forward, I will do the following:-
1...just to get the best out of what is left of the current set of worn tyres....swap on the rims (and balanced)...."zero" front Toe (with String line).
2...get the freeby (old ROHs) set of 15" wheels (cheaper) and (better clearance, to get back the Rake angle)
3...fit new Hankook HS4s (on 15").
4...Wheel Alignment, reduce neg. Camber/Toe (F) 3 deg/Toe-0/Max Castor...(R) 2.5deg/minimum Toe-In....1/4" Rake
5...1st track day.....data and more data collection.
6...review the data
7...2nd track day....maybe some coil-over adjustments....more data collection.
8...review data

Go to another circuit....repeat the above.
Go to another circuit....repeat the above.
Go to another circuit....repeat the above.

Hopefully get enough Data...to settle on a basic setup for each circuit.

Get a new car....start all over again.

Feel free, to continue to add your comments....I will update the results, after each of the above changes.

How good is motor racing???
Cheers,
pdsmanb53

[rob_hun7]

I have a NB with Coilovers and elbj's installed running 3.5 degrees front camber and 3.0 rear camber but I'm running no toe at all. My tire wear has been completely even. From my experience with the MX5 and other cars when it comes to suspension set up, Camber will have a slight effect on wear but it's toe that will do the most damage.

Sent from my SM-N950F using Tapatalk

[pdsman53]

thanks Rob....
not, 'back to the future'...it's, "back to zero" (Toe).
Cheers,
pdsman53