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Minimum tread depth for R-comps?

Old 07-05-16, 06:39 AM
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Minimum tread depth for R-comps?

So today I tracked my FD for the first time. The track was full wet with some standing water.

I had....problems...putting the power down and stopping the car. Not a good day to take out a single turbo FD for the first time.

Generally speaking, what's the minimum tread depth one should use on R-comps? What about in the wet?

My rears are basically at (or past) the indicators, which I assume is a no-no in the wet, and may or may not be OK in the dry as long as it hooks up.

The tires in this case are ADVAN A050s.

What about street tires? Do you need more tread?
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Old 07-05-16, 12:30 PM
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It depends on how wet the track is (how deep the standing water) and where it is wet.

If it is full monsoon conditions with standing water everywhere and more rain coming down then teams use rain race tires at full tread depth as there will be enough water to cool the tire down so it doesn't chunk out.

If it is wet all over, but the depth of water isn't so bad the cars are hydroplaning teams would use a shaved rain tire or an intermediate. Or, if there is a racing line of dried pavement to follow they might even go back to full slicks.

You have to separate the tire temperatures from the water evacuation properties of the tires. Two different things.

If you can keep a full slick up to temp in the wet and avoid hydroplaning it is going to be the fastest tire.

As a learning driver, you probably aren't able to push tires safely to keep them up to operating temps when the water is actively cooling them, so a street tire that works very well at low temps would be a good thing for you.

So, lack of traction from cold tires was not a tread depth issue.

If you were actually hydroplaning, that was a driving line or tread depth issue.
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Old 07-05-16, 06:21 PM
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I suppose that depends on what you mean by up to temp... They were hot enough to be physically sticky, but definitely not the usual hot pizza temperatures you'd expect in the dry.

My biggest problem was that the tires would spin or break lose suddenly and without warning.

I suspect I may have hydroplaned right off the track... doh. Either that, or the track had too much rubber on the line I took.

Shaved is one thing, but would teams run tires past the legal limit?

In my experience, street radials don't grip worth a damn when they're that low.
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Old 07-05-16, 06:53 PM
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No one's mentioned age? A tyre's grip goes downhill fast after X amount of heat cycles and just age - they go off just sitting on the shelf. If they are 2nd hand tyres dont expect too much from them - check the manufacture date on the sidewall.
As mentioned, tread depth is more a function of aquaplaning than anything else.
Congrats on getting the car going too btw.
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Old 07-05-16, 06:56 PM
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They're take-offs (from a big-turbo FC race car, lol) and about a year old I think. They stuck well in the dry before (much better than my street tires) but I've still never tried fresh R-comps...haha.

Still have to get a new seat, belts, and fix whatever is clunking in the rear...

Also need to fix the underpanel I JUST had made. LOL. At least it didn't break my new aero bumper.
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Old 07-05-16, 06:58 PM
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For the record, I suspect I could have gotten away with these tires if I had a proper locking rear diff.
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Old 07-05-16, 10:32 PM
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Originally Posted by Valkyrie View Post
I suppose that depends on what you mean by up to temp... They were hot enough to be physically sticky, but definitely not the usual hot pizza temperatures you'd expect in the dry.

My biggest problem was that the tires would spin or break lose suddenly and without warning.

I suspect I may have hydroplaned right off the track... doh. Either that, or the track had too much rubber on the line I took.

Shaved is one thing, but would teams run tires past the legal limit?

In my experience, street radials don't grip worth a damn when they're that low.
not that it rains a lot here, but it needs to be WET for us to switch to rains, like small rivers wet.

that being said, usually a tire ages out before it wears out, so if its down to the wear bars its usually past it.

and of course, crossing the racing line can be "interesting"

probably a combination of all three
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Old 07-06-16, 12:02 PM
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Valkyrie

I suppose that depends on what you mean by up to temp... They were hot enough to be physically sticky, but definitely not the usual hot pizza temperatures you'd expect in the dry.

My biggest problem was that the tires would spin or break lose suddenly and without warning.

I suspect I may have hydroplaned right off the track... doh. Either that, or the track had too much rubber on the line I took.

Shaved is one thing, but would teams run tires past the legal limit?

In my experience, street radials don't grip worth a damn when they're that low.


I have had the opposite experience.

I find when tires are low on tread, but not heat cycled out they have the most traction.

However, it is harder to exploit this traction.
Because the tire is lighter, shorter and has less of that wobbly tread to absorb rough inputs the tire low on tread requires smoother inputs to keep it gripping.

This is especially true on low grip surfaces (like wet).

DOT Rs are typically shaved to 4/32" and run to cords if they are the type with tread depth in the street tire range (7-9/32").

If they are low void tread type or full slick they are good to go from brand new to cords. These are typically molded with only 4-6/32" tread depth.


For now, just focus on setting up the car so it is most comfortable/safe to you. You will change it all up several times as you progress.
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Old 07-06-16, 07:37 PM
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I suspect any street tire that isn't shaved is going to be well past it's expiration date by the time you get down to 4/32s.

Yeah, I know what you mean about needing smoother inputs. At that point it's effectively a slick tire. But I would be willing to bet money that fresh full-depth tires had far more absolute traction than when they had worn down. My MR2 wouldn't stop or turn without a decent amount of tread on the front or rear respectively.

The car will probably be fine in the dry once I get a comfortable driving position (going to need a different seat and possibly floor modification) and eliminate any slop in the suspension (could be a bad stabilizer link?). Well, that and get some heat in the tires.

A 2-way LSD will also go a long way to preventing wheelspin and help put the power down.

I think I might just buy some Dunlop street tires and save R-comps until after I can set a baseline lap time at my favorite course (Sugo).

The last corner will be a little hairy without a rear wing of some sort, though.
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Old 07-07-16, 09:47 PM
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Was this your first time tracking the FD, or first time tracking in general?
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Old 07-07-16, 10:23 PM
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First time with the FD. Do you really think a complete newbie would be able to track a 2400-pound single-turbo FD they'd barely ever driven (because it's not street legal) in the wet? lol.

According to someone else, there were about four little rivers on the track. Also, my transmission and I think my diff are leaking a bit (need to reseal the oil pan), so I may have been driving on top of an oil slick of my own creation.

My lap times were about 3-4 seconds off pace, fwiw. In the dry, that's a big difference on this track. But what can I say.... it was just a shakedown.
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Old 07-10-16, 06:19 AM
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Just measured the tread depth on my rears. 1.8 to 2 mm... I'm thinking that's a wee bit thin for racing in the rain.

BTW, do oil leaks actually affect traction in the rain?
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Old 07-10-16, 10:40 AM
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Originally Posted by Valkyrie View Post
Just measured the tread depth on my rears. 1.8 to 2 mm... I'm thinking that's a wee bit thin for racing in the rain.
if there is standing water, yes. if there is no standing water, then no not really.

BTW, do oil leaks actually affect traction in the rain?
to really effect traction you would need to get a good coating of oil on the tires and keep it there, so it would have to be a pretty big leak
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Old 07-11-16, 11:59 AM
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Originally Posted by Valkyrie View Post
First time with the FD. Do you really think a complete newbie would be able to track a 2400-pound single-turbo FD they'd barely ever driven (because it's not street legal) in the wet? lol.
True....

I have seen newbies run setups like that before, but usually they shy away from the rain.

Even as less of a newb I still haven't done much rain running. My Comp school was 3 days of wet running at mid-ohio though....so i am much less scared of it!
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