Toyo R888 on wide tracked 98 Van Diement RF98K

[Hardingfv32]

I think the load deflection curves are just another way to present the tire spring rate numbers. Missing is the lateral force vs slip angle data which is one of the most common forms of tire test data.

Without knowing the tire spring rate of your old tires and the R888 I am not sure how your make a beneficial wheel rate change. Note that tire spring rate measurements can be done statically or dynamically on a rolling road.

What is considered the major contribution of the wheel rates to car performance: contact patch compliance or tire temperatures?

Brian

[Brian C in Az]

Per the information in the SCCA link, comparing tire temperature readings across the tire is not critical nor absolute. They state that variations of 25 degrees across the tire are not uncommon and are not important.

See page 13 of that .pdf

[Tom Duncan]

Brian I remember reading about the FF1600/Toyo temps but don't remember where it was...can you provide a link?

Thanks

Tom

[Brian C in Az]

Editted my post because I referencd the F1600 link, but the info I was recalling was on page 13 of the SCCA .pdf under the Spec Miata Set Up

[Brian C in Az]

Did you read this thread regarding tire temps?

http://www.apexspeed.com/forums/showthread.php?t=59908

By the time most cars reach a stop in the paddock, the tire temps have reduced and stabilized across the tire, meaning the hottest spots are cooler and the coolest spots are actually warmer than they were on the track.

[Tom Duncan]

Thanks for the link, I had not seen that thread though I had seen the F1 footage.

Agreed testing temps in the pits is not entirely accurate compared to those generated in a corner but I don't think they are entirely useless. Being quick into the pitlane and quick to take the temps helps.

In my particular case I ran a set of Hoosier R60a's on the car in an earlier session and got what I normally do, the center about 10 degrees cooler than the inside edge and the outer edge another 10 degrees cooler. The car handled great, was as quick as I expected and the tread surface showed good utillization all the way across.

What I saw with the Toyos with increased camber was the center of the tread being higher than the outside edge and the inside edge being the coolest...completely wrong and the handling of the tail of the car agreed. The tread surface indicated the inside edge of the tread was hardly doing anything at all.

Tom

[Hardingfv32]

I wish I had better data but it was the first time we had used IR sensors. FV, R55 Hoosier with 75° ambient at Buttonwillow (clockwise) Apr 2014. Just two sensors per tire. Going back and looking at the data on the last lap and pit entry of a test session, the temps went from a peak of 210° at Mazda corner to 140° upon arriving on pit lane. This is over about a 20 sec time period. Thus 140° temp is constant for over a minute before the system is turned off. It would seem that the 140° surface temp is maintained by the tires core temperatures. Do to setup issues I can not say anything about the tire's surface inside vs outside temps.

Food for thought.

Brian

[Raceworks]

I generally only use a pyrometer for anything other than getting an idea of whether or not the tire is getting heated to temperature. I've screwed up set-ups royally chasing tire temps from pit-lane readings. The temps are way too heavily influenced by whatever happened right before the car entered pit lane, how the driver entered the pits, how you stick the probe in, how much pickup the tires got before it stopped, how quickly you jumped over the wall, ambient air temperature, wind velocity, etc.

Instead I mainly look at tire pressures (they stay stable for longer) and the wear indicators on the tire. That plus driver input is how I tune.

Plus, another thing to consider with the R888 is that it IS going to feel less grippy no matter what you do, that's kind of the overall point. Even the pro guys are several seconds slower than the bias-ply slicks.

Every tire design by definition has to be a compromise (much like designing anything else).

Write down:

• Low Cost
• High Durability
• High Consistency
• High Grip
• Low Weight

You get to pick three of those.

[Tom Duncan]

I too generally go by three factors, each of which has limitations: Driver feel/on track performance, tread appearance and temps. The temps are the least direct of the bunch due to all the reasons Sam outlines above but they can have relevance in combination with the other two and with a full understanding of the limitations.

Below is a photo of my tread pattern, in this case the right front because it was lit best in my garage. Double click on it to enlarge. Ignore the pickup on the left. The pattern is the same for all four tires, varying just a bit, heavy use on the outside edge and center, almost none left of center. It's like the camber thrust is forcing the tire to fold over, and this at 2.75 degrees of camber on the shown tire and 3.25 degrees at the back which looks the same.

Tom

[John LaRue]

The R888 can also be shaved for an increase in performance, but less remaining tread means less usable life.

???

[Gary_T]

???

That's referencing spec miata. The FF guys are saying (as far as I can tell) shaving makes no appreciable performance improvement.

[Tom Duncan]

Agreed, everyone I've talked to about using the R888 on an FF says shaving doesn't make enough difference to make it worthwhile. While the Miata at something like double the weight of an FF can make a fresh tire tread squirm, overheat and lose traction an FF isn't and can't to any appreciable degree. On the other hand I have heard of those saying they got their best laps near the end of the tires tread depth life but those same folks never suggested shaving the tire to get to that tread depth would be worth doing.

Tom Duncan

[Tom Duncan]

Found the handling problem...all the wheels were loose, the RR rattling on the hub. Small wonder it was squirrely in a straight line! Apparently there is some incompatibility between the Panasport wheels and the VD hubs. I know I torqued the wheels when we put them on, we have a fairly foolproof procedure and I’m the only one that does the actual torquing. I have not used these wheels on the VD before. They are designed for center lock use.

I’ve never had a loose wheel or wheels on my race car before so I didn’t recognize what was happening. We’re pretty rabid about checking wheel nut torque when switching tires/wheels around but as we left each tire in the same place and I’ve never had a loose wheel before we didn’t think about it. I would like to get these wheels to work on the VD but I have other sets I know are compatible so its an easy fix.

I also found a 4.5” difference in track between the front and rear (center of tread to center of tread) so I’m going to be looking at wheel offset/spacers and see if I can even that out a bit.

So things should be better next time!

Tom

[TimH]

Found the handling problem...all the wheels were loose, the RR rattling on the hub. Small wonder it was squirrely in a straight line!

Here's to a better experience next time.

[Brian C in Az]

It's like the camber thrust is forcing the tire to fold over, and this at 2.75 degrees of camber on the shown tire and 3.25 degrees at the back which looks the same.

Most guys are having better results running a little less camber in the rear.

[marshall9]

What a waste of time this thread was..................

Really Tom? You know better. Folks are taking notes of what happens on these tires, and gathering ideas based on real world data. The Toyos are a solution to a financial issue that is prohibitive to class recovery/growth in FF. This turned out to be a bush league prep list solution to a problem that you asked major league competitors.

[marshall9]

I too generally go by three factors, each of which has limitations: Driver feel/on track performance, tread appearance and temps. The temps are the least direct of the bunch due to all the reasons Sam outlines above but they can have relevance in combination with the other two and with a full understanding of the limitations.

Below is a photo of my tread pattern, in this case the right front because it was lit best in my garage. Double click on it to enlarge. Ignore the pickup on the left. The pattern is the same for all four tires, varying just a bit, heavy use on the outside edge and center, almost none left of center. It's like the camber thrust is forcing the tire to fold over, and this at 2.75 degrees of camber on the shown tire and 3.25 degrees at the back which looks the same.

Tom

That looks like a tire with maybe a lap or two on it that may have picked up some rubber on the way into the pit lane. Slide the car, and heat them up !

[DaveW]

Found the handling problem...all the wheels were loose, the RR rattling on the hub. Small wonder it was squirrely in a straight line! Apparently there is some incompatibility between the Panasport wheels and the VD hubs. I know I torqued the wheels when we put them on, we have a fairly foolproof procedure and I’m the only one that does the actual torquing. I have not used these wheels on the VD before. They are designed for center lock use.

I’ve never had a loose wheel or wheels on my race car before so I didn’t recognize what was happening. We’re pretty rabid about checking wheel nut torque when switching tires/wheels around but as we left each tire in the same place and I’ve never had a loose wheel before we didn’t think about it. I would like to get these wheels to work on the VD but I have other sets I know are compatible so its an easy fix.

I also found a 4.5” difference in track between the front and rear (center of tread to center of tread) so I’m going to be looking at wheel offset/spacers and see if I can even that out a bit.

So things should be better next time!

Tom

The few times I've had a wheel come loose, it turned out to be a case of the chamfer on the inside edge of the wheel center hole being too small to clear the radius on the hub. It would torque up fine, but would work loose within a few laps. This is especially relevant since that was the 1st time you used those wheels.

The other issue I've seen, but never caused me a to have a loose wheel, is the drive pins being either slightly too large for the holes, or slightly out of alignment with them.

[Tom Duncan]

Dave, I think you're on the right track with the mis-matched chamfers. I had to shave down the chamger on the wheel rims to get the wheel to seat fully to the hub but I am thinking I didn't go far enough. Though the rim finally seemed to fit flat easily against the rim perhaps the heat from the brakes caused the tolerance to shrink or some such. I am pretty sure the drive pin/wheel hole fitment is correct as they just barely slide on but I will check that because as you pointed out if there was any slop it could move back and forth along the pin/hole circle and encourage the center nut to loosen.

Marshall, have the courtesy to look at the image of the tire surface closely and understand what you are seeing before you make conclusions.

As to "This turned out to be a bush league prep list solution to a problem that you asked major league competitors" you are mostly correct.

Tom

[DaveW]

...I am pretty sure the drive pin/wheel hole fitment is correct as they just barely slide on but I will check that because as you pointed out if there was any slop it could move back and forth along the pin/hole circle and encourage the center nut to loosen...

Actually, if there is enough clearance hole-pin to get the wheel to seat properly, there is also enough clearance to allow loosening if the retaining nut tension is not high enough to let friction keep the wheel from working back and forth. With proper fit, what normally happens in use is the wheel finds a limit position against the pins and hub based on the direction of maximum axle torque, bump impact loads, etc., and the friction then holds it there.

If the pins were so tight as to hold the wheel from rotating w/o needing the friction, you would not be able to assemble the wheel to the hub properly, leading to accidental loosening, similar to the case with mismatched chamfers. So, too tight or misaligned pins also cause issues, and a slightly loose pin fit is what you want.

Note that with machining tolerances, some clearance in the fit is always needed. There is no such thing as perfect pin fit/alignment in this type of situation.

[DaveW]

...If the pins were so tight as to hold the wheel from rotating w/o needing the friction, you would not be able to assemble the wheel to the hub properly, leading to accidental loosening, similar to the case with mismatched chamfers. So, too tight or misaligned pins also cause issues, and a slightly loose pin fit is what you want.

Note that with machining tolerances, some clearance in the fit is always needed. There is no such thing as perfect pin fit/alignment in this type of situation.

Another thing to remember is that even if you managed to achieve a perfect fit of one wheel in one position on one hub, as soon as you changed wheels, or rotated a wheel on the same hub, the fit would be off again. So some clearance is always necessary.

[old 59]

I have also seen drive pins that are just a smidge too long and bottom out in the pin holes, if they are blind holes. Torquing up the wheel feels fine at rest, then as the car is driven for a short time the wheel rattles itself loose as the pins bury themselves into the wheel and release the wheel nut torque.

[problemchild]

That looks like a tire with maybe a lap or two on it that may have picked up some rubber on the way into the pit lane. Slide the car, and heat them up !

That pic looks like a nice scrubbed tire. We run 3 or 4 easy laps on them to get rid of the sticker glue and mold nibs. Next time out, they are ready to go.

Hey everybody! Make sure you read post # 59. Like any erroneous headline, only a portion of readers catch the later retraction, buried on page 2.

[Tom Duncan]

Dave, you make a good point about moving the wheels around to different positions, requiring all the wheels to fit on the hub with the least tolerance.

I have another set of wheels that work fine on the VD, I think I'll just put the Toyos on them and abandon the idea of running them on the Panasports. I initially did this because I have a Club Ford which the Panasports were used on and was hoping to use the Toyos as rain tires when I ran it.

Turns out it gets worse, in the course of inspecting the RR upright assembly I found two of the six long bolts that hold the outer hub to the inner were broken, and one more on the way. In addition the stub axle (what I'm calling the part with the threads to screw the wheel nut onto) is slightly loose. Hard to say which came first, the hub being rattled to death by the loose wheel or the broken bolts and loose axle contributing to the loose wheel, though if I had to vote I would say the former.

Stephen, in this case the holes for the pins go all the way through the rim so bottoming isn't an issue but if anyone is reading this thread in regards to loose wheels (I changed the title and intro of the original post) that might be their solution.



Tom

[Steve Bamford]

Thank you Tom for revising your first post.

[Dick R.]

Now that the cause has been determined, lots of facts about the Toyo's shared, etc. I cannot get "Its a fine time to leave me Lucille and the many "loose wheel" parodies out of my mind. For example: https://www.youtube.com/watch?v=YKaw0t3LqX0

FYI many years ago when running an SCCA drivers school in my new to me 85 VD FF at Charlotte on the combination road course and oval track the car started feeling strange (to even me a rookie) in the braking zone for the infield after going through Nascar 3-4 at about 130 mph max. When the session was over we found the problem. Right rear camber adjuster jam nut was at least 1/8 inch loose. Oops!

[Garey Guzman]

Tom,
If the wheel is just touching the chamfer, a simple solution is to make an aluminum spacer, maybe .100-.125" thick. I've used them with no issues.

[marshall9]

Now that the cause has been determined, lots of facts about the Toyo's shared, etc. I cannot get "Its a fine time to leave me Lucille and the many "loose wheel" parodies out of my mind. For example: https://www.youtube.com/watch?v=YKaw0t3LqX0

FYI many years ago when running an SCCA drivers school in my new to me 85 VD FF at Charlotte on the combination road course and oval track the car started feeling strange (to even me a rookie) in the braking zone for the infield after going through Nascar 3-4 at about 130 mph max. When the session was over we found the problem. Right rear camber adjuster jam nut was at least 1/8 inch loose. Oops!

four hungry children and a crop in the field...........ya HAD to go there?

[TimH]

Too bad we can't change the topic header on this thread, because there's been some useful information along the way.