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I was at the Seat Time event on Summit Point Shenandoah track this Saturday. Weather was perfect 75F and sunny with only 15 participants running on open track from 9am to 2pm.
Car ran great but I noticed slight vibration second to last session. I checked the car when I got back in and found that my front left tire had this small corded patch about 1 inch from the outer shoulder. This came as a surprise as tires are bout half worn on the outside and with plenty rubber remaining on the inside - I got them before the car was lowered and I couldn't get decent amount of camber. Car has anti lock brakes so tire couldn't have locked up and created flat spot leading to this weird corded patch.
Have you guys seen tire get corded spot like this before? Can I make case with Nitto that this is tire defect rather than normal wear and tear?
This also bring me to second question given that rest of the tires have plenty life left - can I mount just two new NT01s until I use up the older two and then change them as well? How much difference in grip would it create or would it be unsafe to it in the first place?
Here is the corded section:
Here is rest of the same tire, plenty of rubber left:
Last edited by Nadrealista; 08-26-2019 at 10:56 AM.
Does this track have hard right turns? My first thought was your toe alignment on that wheel is off, but left front outer wear is consistent with heavy load on the tire in a right turn, and insufficient camber to keep it flat on the ground. Perhaps insufficient tire pressure too, it looks like it rolled over.
Toe won’t enter into that situation. What size tire on what rim width? I’d generally expect that on a car that doesn’t have enough camber, but has the pressure raised to prevent rollover on the outer corner and perhaps a tire that’s on a wheel that’s narrow compared to it’s width. A pyrometer would have likely shown that section way hotter than any other.
This was on counterclockwise very technical circuit with 19 turns most of which are left handers. this makes it even more surprising that it would happen on the front left tire.
Another thing that is weird to me is that corded section is more than an inch from the tire shoulder and it is only small patch (1" x 2" approx in size and does not go whole circumference of the tire) while rest of the same tire in that section has plenty thread left as second picture shows with thread depth dimple. most corded tires I saw have corded section that goes whole circumference of the tire?
These tires are nitto NT01 255/40/17 on 9" rim. they started their life on car when it had stock suspension and only -1.1 camber available which created more wear on the outside shoulders. this spring I got coilovers installed which gave me -2.4 degrees of camber up front with 0 toe. I have tire pressure monitor and pressures were in 37-39psi range.
this is what I would expect corded tire to look like - NOT my tire:
Last edited by Nadrealista; 08-28-2019 at 08:16 AM.
Well it just depends. That’s on the inside and a result of different conditions, assuming you didn’t mount it in a flipped inside-out position (fyi, he changed the pic adter my reply, now showing outside wear). I generally wouldn’t consider 255 crowded on 9”, but they do appear to be on the wide side, which is not unusual for a track performance tire. I’m not really familiar with that particular tire, but with highish pressure, not enough camber, stiffish sidewall, but not so stiff tread carcass it would cause the treadface to bulge out some and without enough camber would wear down quicker further inboard like that. As the rim width decreases it creates a similar effect, as bending the sidewalls back tends to crown the treadface out toward the corners. You could try to contact Nitto motorsports and get their input.
Well it just depends. That’s on the inside and a result of different conditions, assuming you didn’t mount it in a flipped inside-out position. I generally wouldn’t consider 255 crowded on 9”, but they do appear to be on the wide side, which is not unusual for a track performance tire. I’m not really familiar with that particular tire, but with highish pressure, not enough camber, stiffish sidewall, but not so stiff tread carcass it would cause the treadface to bulge out some and without enough camber would wear down quicker further inboard like that. As the rim width decreases it creates a similar effect, as bending the sidewalls back tends to crown the treadface out toward the corners. You could try to contact Nitto motorsports and get their input.
would going with 235 instead of 255 on the 9" rim for the next set be beneficial?
also what are you thoughts about replacing just two tires since other 3 tires have several days left in them?
Look for a couple of used ones if you are going to swap out 2.
If you look at the profile of a new NT01 you will notice that you have worn off a lot of the outside block... that's the first area you will run into the cords. The last set I ran ended up similar to that with the wear in the same part of the tire... just on the inside not on the outside like that...
I think I will try to get 2 used 255 if I can find them, but for next set I will try 225/45/17 which will be 3 lb lighter per corner vs 255 with similar contact patch in addition to better wear characteristics on 9" wheel. Lot of miata folks do this with good results:
"1. Increased tension on sidewall reduces unwanted deflection and distortion.
a. Quicker steering response
b. Reduce camber loss from sidewall deflection
c. More linear steering response at max slip angle
2. Increased air volume
a. Lower pressures allow tread to conform to road surface better, improving grip.
b. Increased air volume temperature fluctuates less with thread heating/cooling.
3. Contact patch is increased by decreasing psi loading per unit area (lower air pressure and wider rim). Imagine pressing hard inflated basketball onto ground or mostly deflated basketball onto ground.
a. By lowering loading per unit area, total friction potential per unit area is increased.
b. Tire wear pattern is more even
c. Tire wear rate is improved
In general, a Spec Miata with 205/50 NT01's on 15x7's will run around 39psi hot. The same car with 225/45's on 15x9's will run around 30psi hot
and generate about .25g more lateral grip"
^^ aren't they comparing a 7" wheel to a 9" wheel? 2 of those points don't apply if you're going from 255 on a 9" to a 225".
I've settled on 235 as my weapon of choice, wouldn't go narrow than that personally. Our cars are heavier than spec Miatas.
But that aside, I'm with Team on this. The fundamental problem seems to be camber so see if you can get more. How much are you running now? And caster?
Well they were discussing the 225 on 8” vs 9” wide wheels and some of those things in your list were 205 vs. 225 in 15” diameters.. The MX5 is a bit lighter than an RX8 too. That said, I’d really rather see a 255 on a 10” -10.5” wheel for sustained high speed cornering on a track. For autox where transitional cornering is more important it can get away with 9” ok. After looking at the specs the 235 seems like a good choice for 9”.
^^ aren't they comparing a 7" wheel to a 9" wheel? 2 of those points don't apply if you're going from 255 on a 9" to a 225".
I've settled on 235 as my weapon of choice, wouldn't go narrow than that personally. Our cars are heavier than spec Miatas.
But that aside, I'm with Team on this. The fundamental problem seems to be camber so see if you can get more. How much are you running now? And caster?
my front camber is -2.4 now (but only since since may) and FL caster is 7.7 degrees, but these tires spent most of their life with only -1.1 of camber.
as far as weight is concerned 225/45 actually has higher load index than 235/40 tire so it can carry higher load
with NT01s I have following options in 17" size
225/45/17 24.80" diameter, 7.0-(7.5)-8.5 rim range, 23.57lb and 91W load index
235/40/17 24.40" diameter 8.0-(8.5)-9.5 rim range, 23.52lb and 90W load index
245/45/17 25.55" diameter 7.5-(8.0)-9.0 rim range, 27.03lb and 95W load index
255/40/17 24.92" diameter 8.5-(9.0)-10.0 rim range, 26.26lb and 94W load index
thanks for clarifying that you have no idea what you’re doing, I was thinking maybe you did for a moment there since you seemed to be taking advice rather than insisting on ill informed decisions
Maybe you can elaborate on why you believe that the load rating is the correct decision point factor? Or why you want to run the same width tire as a car that weighs 500+ lbs less when the next larger size tire is a perfect fit for your wheel width? Per your earlier MX5 reference thread, in 15” they can only choose between a 205 or 225 size; those are their only options in NT01.
Don’t just blindly play monkey see, monkey do. Try to think it through a bit more. Which your tire info post above left out the tire width data from the Nitto website
static tire width is not important as the size of the actual contact patch tire will generate and that is dictated by the weight of the car, tire pressure and wheel width (more shape of the patch than the size). what most people don't realize is that contact patch between 225 and 255 tire is probably same on the 9" wheel for a given tire load. 225 and 235 are much better matched to 9" wheel and difference between them will be a wash.
what I don't like about 235/40 is that my tire diameter will go down another .5 inches and I am already running out of gears in certain places requiring additional up-*****
You will have better acceleration though and more grip than the 225. There are always tradeoffs, but I wouldn’t choose the 225. It’s your decision. Good luck.
Car has anti lock brakes so tire couldn't have locked up and created flat spot leading to this weird corded patch. - that assumes the abs didn't momentarily cut out. It also assumes the abs doesn't allow the wheel to slow which it does, so if you use the abs a lot, it might have happened just with the small lock ups that the abs allows.
Have you guys seen tire get corded spot like this before? Can I make case with Nitto that this is tire defect rather than normal wear and tear? - You could try. It looks like wear related to me. It's possible the tire blistered. Not sure if that is counted as a defect.
This also bring me to second question given that rest of the tires have plenty life left - can I mount just two new NT01s until I use up the older two and then change them as well? How much difference in grip would it create or would it be unsafe to it in the first place?
- You can. There will be a slight grip difference between the different aged tires, and the ones with more tread will heat up a little quicker. Not really an issue as long as you keep them on the same axle. Just be aware of it when making adjustments to pressures and anything to affect handling balance. I would decide this based on the condition and age of the other tires (if you have more than 6 days on them I'd replace all 4).
The tread looks very thin around where it has corded.
Judging by the visible dimple (tire depth gauge), the 2nd pic seems to show more tread.
So is this same tire worn more on one side than the other?
If that is the case, then I would suspect a lock up caused it. Either a single event, or maybe from multiple abs engagements.
I don't think you'd feel vibration from that small amount of cording either, but you would feel it from a flat spot.
Too much roll (from soft suspension and high ride height) combined with too little camber would cause a wear patter around the outer 1/3 of the tire.
It's possible the tire blistered, or caught some debris as well, but it looks pretty worn around the area that is corded so I don't think that is the case.
255/40/17 will be faster (more grip) than 225/45/17 on the same size wheel.
Depending on the condition of the other tires, I would either get another pair of 255/40/17 tires and put those on the same axle, or get a set of 4.
I don't think tire size is your problem. You've already added camber, so you might not need to change anything other than getting new tires. I would look at it and investigate a possible lockup (e.g. Do you have wheel speed data logs from your Aim? If so, are there any drop outs?). I'm sure you could use even more camber as well.
Last edited by blu3dragon; 08-29-2019 at 03:01 PM.
I run 225 Nitto NT-01s on my Miata on 9" rims quite successfully. I think I pics on this forum of the contact patch width between those tires and a set of 255s on 9" rims that were on my RX-8. I'll see if I can find them again. The width was within 1/8" between the two. With the narrower section width, you get reduced rotational mass, increased sidewall stiffness, less lateral tire movement, lower cost. My next set of RX-8 tires were going to be either 225s or 235s.
IMHO, you do need more negative camber. I run -3.5 on the Miata in the front, and I need a little more to put the tires in their true happy places.
I am running 255s on my E46, but they are on 10.5" rims.
so I took tape measure to the garage this morning. looks like rim width dictates how wide tire section and thread width will actually be. put tire on wheel that is less than section/thread with you end up with narrower tire that its spec - mushroom effect. my guess is that my tire corded exactly in the spot where my 9" rim puts most of the load - which is at the end of the rim and not the tire edge.
this is probably turn that did the FL damage, you have to brake hard downhill and make hard right turn off camber all at the same time.
Rival S 245/40/18 on stock S2 8” wheel, specs are overall width 9.8" thread width 9.1", rim range 8.0-9.5:
Nt01 245/40/18 on stock S1 8” wheel, according to nitto this tire should have 9.72" overall width and 9.22 thread width (.5" less than overall), rim range 8.0-(8.5)-9.5. however on 8" wheel looks much more narrow:
Nt01 255/40 on 9” wheel, per nitto should have 10.35" overall width and 9.85" thread width, rim range 8.5-(9.0)-10.0:
Last edited by Nadrealista; 08-30-2019 at 12:19 PM.
08-26-2019, 10:03 AM
