Wheel and tire advice

ccgillett

Well-Known Member
I'm considering stealing Jason Backs (@JBINTX ) track setup for dry conditions. If you've seen his videos you know how fast he is. Note this setup, copied/pasted/linked below, uses slick tires. I'm doing open track days and lapping days, not every club permits slicks. I've also got tire warmers which will help with warm up.

Track tires 15x10 American Racer 23.5/10.0-15s (131 compound)
Track wheels Aero Race wheel 50 Series 50-104550 15x10 with 5" back space (these clear the calipers on the 09 tc SS model), Day motor sports 800-543-6238)
Track wheel spacer/adapter - 1" to get from the 5x110 to 5 on 4.5"
Track tire and wheel weight 43 lbs


Here are some useful links if you're interested in this approach:
https://americanraceronline.com/tires/modified-sprint-asphalt/
https://www.vividracing.com/-p-153405977.html
https://www.daymotorsports.com/shop-by/product/wheels-and-tires/aero-50-series-roll-formed-wheel-15-inch-by-7-8-10-and-12-inch-wide/50-SERIES
 

JBINTX

Goblin Guru
I'm considering stealing Jason Backs (@JBINTX ) track setup for dry conditions. If you've seen his videos you know how fast he is. Note this setup, copied/pasted/linked below, uses slick tires. I'm doing open track days and lapping days, not every club permits slicks. I've also got tire warmers which will help with warm up.

Track tires 15x10 American Racer 23.5/10.0-15s (131 compound)
Track wheels Aero Race wheel 50 Series 50-104550 15x10 with 5" back space (these clear the calipers on the 09 tc SS model), Day motor sports 800-543-6238)
Track wheel spacer/adapter - 1" to get from the 5x110 to 5 on 4.5"
Track tire and wheel weight 43 lbs


Here are some useful links if you're interested in this approach:
https://americanraceronline.com/tires/modified-sprint-asphalt/
https://www.vividracing.com/-p-153405977.html
https://www.daymotorsports.com/shop-by/product/wheels-and-tires/aero-50-series-roll-formed-wheel-15-inch-by-7-8-10-and-12-inch-wide/50-SERIES
Only good reason to go with a square setup on the Goblin is so you can rotate them - frugality.
I need to play with pressures more after reading the above article. Last time out I was around 20 psi rear and 15 front.
Overall, this setup seems to be a really good choice. One of a million out there….
 

Chris_WNC

Well-Known Member
I haven't built yet but ended up buying a higher TW all season tire. Square setup. I was worried about the cooler temps here in WNC in the fall and winter. I may run them during the build and switch to some #barelySTREETlegal lower TW tires in spring and summer.

CHRIS
 

Jm12

Active Member
@JBINTX What are your thoughts on running the spacers/adapters? I was going to get my hubs re-drilled and adapters did not even cross my mind until I saw someone in the FB groups mention running them. Also, which ones are you running? I'm looking for some that are hub centric.
 

JBINTX

Goblin Guru
Best thought is if a hub goes bad, it is easily sourced with a stock replacement.

Wheel choices are limited with the stock lug pattern.

Depending on the wheel, you may not have much of a choice on the back spacing. With a steel wheel like I have, they offer several options - they just weld the face in more or out more on the wheel to change the backspacing.

I chose to set the wheels outboard just a little to ensure clearances. Also give it a “wide” athletic stance…. ;)
although the extra cantilever with the sticky tire did find the failure point of the stock suspension bracket. :(

uswheeladapters.com
1” thick
5x110 to 5x114.3
 

Jm12

Active Member
Regarding the Lotus article around tire choices width vs weight and the relationship to heat + grip specifically, I think there are some variables that are being left out there. Tire choice, application, and ambient temperatures are all important factors. On a midsummer day at an autocross course, a Goblin running A7s in 275 width is going to need its tires sprayed down after the second or third run just like everyone else's. I have seen cars very similar to ours with approximately the same setup I just mentioned struggle to bring their tires up to temp in morning run groups early in the season, but that's not unique to them- I've been the same run groups and never gotten my tires up to optimal operating temperatures on a 3500 lb vehicle running 245s. Talking about a different performance application, I can imagine that even at a track, really wide R7s on a Goblin could be difficult to bring up the temp on a cool day or without front and rear aero, but that's a tire and application that I have no experience with so far, so it's conjecture.

Higher tread wear, less performance oriented tires when you're not pushing it are going to be a different story, but if you're not pushing it, optimal operating temps aren't as important. Additionally, I think the consensus in the DFG community is that anything above 200TW isn't really optimal for these cars.

I think realizing that when you turn one dial it's affecting the others is the most important part of picking a tire and wheel setup that works for you.
 

ccannx

Goblin Guru
When picking wheels it is very important to figure out what your backspace is. Backspace is the distance you have from your hubface or the surface that your rim will attach to on the brake rotor hat back to where your rim will contact suspension or body components. You can measure this by using flat metal or bar stock layed across your hub surface and measure back to your struts. On the front I believe it would also work to turn your wheels left and right to measure how much distance you have to your control arms(top and bottom) at the desired wheel radius. Its important to subtract clearance for wheel/tire flex under load to your desired backspace availability.

Using a suspension calculator you can find your desired wheel offsett using your desired backspace and wheel width. Offsett is usually measured in distance by mm from the centerline of the wheel.
 

Ross

Goblin Guru
I've been learning so much about tires! But still need to know more...
Regarding the Lotus article around tire choices width vs weight and the relationship to heat + grip specifically, I think there are some variables that are being left out there. Tire choice, application, and ambient temperatures are all important factors. On a midsummer day at an autocross course, a Goblin running A7s in 275 width is going to need its tires sprayed down after the second or third run just like everyone else's. ...
I've never seen people spraying down tires at autocross. Just using water in a garden sprayer?

Anybody have recommendations on a tire thermometer/pyrometer to purchase?

Why did Jermey wrap his tires? Does it somehow make them last longer?
27379
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Dale E

Well-Known Member
I use an infa red pointer type like for exhaust and radiator temperature taking. Any will do like one from Lowes. I have a small key ring pocket one also.
We used a garden sprayer with water at autocross like most others do. And a lot of folks wrap their tires after a run to keep heat. You can make some out of that silver rolled up insulation stuff from the hardware stores.
Jeremy probably wrapped his tires due to traveling to a car show and he doesn't want the tires picking up dirt and gravel bits that he would have to clean off before the show. Same with the F1 folks and other racers that roll their cars around the garage and paddock area -- take off wraps and the tires are clean to go on track.

A normally street driving Goblin needs no more than a 225 or 245 width tire. Anything wider is overkill and expense. My personal take is the 18 and 19 inch rims are too big and out of proportion for the Goblin and anything wider than 245. My opinion only!!

For racing then you need the wider tires, but to a point of article wider tires also take more time to heat up, so perhaps not even wider for racing. We were FTD at autocross in our Stalker on 225 & 245 x 15's than the Zo6 and EVO 4x4. They were on slicks. The cars that were faster were the shifter kart and the WSU FSAE formula.

Dale
 

Brocker

Member
Thanks to everyone who has contributed to this thread. However, I'm still frustrated. After reading Lonnie's articles regarding the Lotus I tried to track down what they use in the staggered set up. When using the nice link to the tire calculator it was difficult if not impossible to find tires that match tires those wheels from Tire Rack. This is frustrating.

I know all of you mean well and I thank you for the input.

However, what I really need is: 1. what wheels you bought (manufacturer, size, offset, part number if you have them) and 2. what tires you have used (size details). Spacer details if used. I don't mind buying a couple sets of wheels and tires.

I have the upgraded 5 X 114.3 hubs. Thank you.
 
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Jm12

Active Member
@Ross yes, just a pump garden sprayer. In warmer climates a lot of 200TW and softer tires will overheat quickly when pushed hard and start to lose grip. Spraying them down between runs helps to mitigate that.

Regarding a pyrometer I have no recommendations, but don't get a laser touchless thermometer for tires. I made that mistake and they are completely worthless for that application.

Tires are wrapped to make them last, either to prevent oxidation or because they're prepped.
 

Desert Sasqwatch

Goblin Guru
Thanks to everyone who has contributed to this thread. However, I'm still frustrated. After reading Lonnie's articles regarding the Lotus I tried to track down what they use in the staggered set up. When using the nice link to the tire calculator it was difficult if not impossible to find tires that match tires those wheels from Tire Rack. This is frustrating.

I know all of you mean well and I thank you for the input.

However, what I really need is: 1. what wheels you bought (manufacturer, size, offset, part number if you have them) and 2. what tires you have used (size details). I don't mind buying a couple sets of wheels and tires. Thank you.
Has no one sent this link or have you not found it?


Personally, I'm going conservative on the tire sizing with a 225-45-17 on a 17x8 front and 255-40-17 on a 17x9 rear staggered set up. These tires are stock diameter at 25 inches. They are, however, less than 200TW so will provide the needed traction for street driving. Hope this helps.
 

Waterdriver

Goblin Guru
@Ross yes, just a pump garden sprayer. In warmer climates a lot of 200TW and softer tires will overheat quickly when pushed hard and start to lose grip. Spraying them down between runs helps to mitigate that.

Regarding a pyrometer I have no recommendations, but don't get a laser touchless thermometer for tires. I made that mistake and they are completely worthless for that application.

Tires are wrapped to make them last, either to prevent oxidation or because they're prepped.
For autocrossing a Goblin or other open wheeled cars, a sprayer is not needed. The tires, wheels and brakes cool down quickly without anything around them trapping heat in and preventing cooler air to get to them.

The only time I've been able to get my tires (R888R) up to temp and start to really gum up when autocrossing is on 85-100 degree days, and not until the 4th or 5th runs. Adding more air pressure would help bring them up to temp quicker, but there's just no grip until then. This is with about 10 minutes between runs.

Even the tires on our race kart tires dont get up to temp during a run. I run the kart tires about 5-10 psi higher for autocross to help stiffen the tire, decrease rolling resistance and build heat quicker. Typical to qualifying.
 

Jm12

Active Member
@Waterdriver I've not run that tire but I've heard that it's not a stellar pick for AutoX and I believe this is one of the reasons, ie takes a while to come up to temp. That, and it's out of the 200tw category so it's in a domain where Hoosiers tend to dominate (if money is no object). This is kind of what I was getting at earlier- different applications will dictate what is or isn't a good wheel and tire setup. Cruising, spirited driving, autox, track are all going to have different ideal setups, and while there's overlap there's no one ring to rule them all.
 

Brocker

Member
Yes
Has no one sent this link or have you not found it?


Personally, I'm going conservative on the tire sizing with a 225-45-17 on a 17x8 front and 255-40-17 on a 17x9 rear staggered set up. These tires are stock diameter at 25 inches. They are, however, less than 200TW so will provide the needed traction for street driving. Hope this helps.
Sure have seen it and tried to order the wheels on page two of that post. Not available in the sizes shown until Dec 31.
 

ccannx

Goblin Guru
In case anyone missed it Andy Hollis did a good scientific 200 treadwear tire test and tested the "top dog" track and autocross tires in their respective settings. Since then the RT660 is a new contender but it is mostly used in the spec class and does not heat up as fast as the yokohama a052, this may make it better for 2 driver cars. Unfortunately we are at the mercy of our wheel size as far as tire selection.

On the c5 corvette I spray the yokes every run, they love to be cool at least that seems when they are at their best for me. Since the Goblin runs in E-Mod I would only recommend autocrossing it on A7's , r25b or avon slicks but that's a lot of work unless you tow the car to the site.

Saran wrap on the tires would help keep from picking up every rock in the parking lot or driveway. When those tires get hot they turn into a balls of glue and the rocks will try to embed and freeze into place when they cool down. I have pulled sharp rocks out that seemed to be all the way into the cords. I used to take my Hoosier off after every event to clean the opr /rocks then bag them in thick black garbage bags to keep the UV rays and ozone away from them.

200tw Tire Test: Valino and Yokohama Take on Favorites | Articles | Grassroots Motorsports
 
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JERMzSS

Well-Known Member
It looks like Hoosier A7s are very good racing tires. If you decide to get a set, they have a few recommendations for getting them ready for racing.

A7/R7 Care and Safety Guidelines
The R7 and A7 have been developed to improve wear and consistency without any sacrifice of performance. In many cases, the performance will even improve over previous models. The new tire models are an evolution in the continuing effort to provide the best tire for racers.

TIRE BREAK-IN PROCEDURE
Proper break-in will not affect initial performance but will increase the competitive life of the tire. The procedure can be broken down into phases.
1st phase: The initial run
2nd phase: The length of the time the tire is allowed to “cure”
THE INITIAL RUN HEAT CYCLE
A7/R7 Roadrace The first laps for the tire are critical for setting up the durability and competitive life. The first session should consist of no more than 10-15 minutes of running. The early part of the session should be run at an easy pace, with the speed gradually increased until the end of the session. The final lap should be run at the fastest possible speed. The intent is to achieve maximum tire temp on the last lap. At this point the car should be brought in and the tires allowed to cool at a normal rate. During the initial run-in process, the inflation pressure should be 3-5 psi higher than you would normally use. The best progression would have the driver taking 4-7 laps to accomplish this break-in. Each lap should be approximately 7-10 seconds a lap faster than the previous lap. The goal is to have the tire temp as high as possible on the last lap without “shocking” the tire during the warm up laps. In essence, no wheelspin, late braking, or sliding. The last lap should be at, or very close, the maximum possible.
A7 Autocross
For autocrossing, the A7 does not need the same break in procedure as the R7. The A7 needs a minimal scuff-in session before the first autocross run. This “session” can comprise of simply driving around the event site at minimal speeds on the A7 set of tires. By scrubbing off the newness of the tread (no or minimal shininess remaining) prior to your first competitive run, the A7 tires will be more consistent in handling, grip and responsiveness on the first run. If this is not completed, running on un-scuffed A7 tires on your first run may result in the tires not gripping properly, or feeling like they “skate” over the course surface. You are welcome to run 3 - 5 psi higher when scuffing in a new set of A7’s, but be sure to reset them to the correct operating pressures before your first autocross run. As you compile autocross runs on your new A7’s, they should become more consistent in run times.
“Cure” Time
After completing the initial run phase, the length of time the tire is allowed to set is possibly more important. The barest minimum for this process to be beneficial is 24 hours. (Not “the next day”). Any less than this is a waste of time. The best situation would allow a week before using the tire again. Proper tire management is a difficult process. To accomplish this almost always requires a second set of wheels. The payoff is greatly increased competitive tire life. Following the recommended break-in procedure will require a lot of planning to make it work. The benefits to doing it right include greatly increased tire life as well as consistent performance and durability under stress. Please make an effort to educate your team on the importance of this. It can save you a lot of money.
Tire Temperature Recommendations
For best performance the expected temperature range will vary from track to track. Generally, optimum traction will be generated when the pit lane temps show 180-200 degrees for the R7 in Roadrace applications, and 110-140 degrees for the A7 in an Autocross application. To get accurate hot tire temperatures, you should use a needle probe. An IR sensor surface temperature device will read cold and this may cause you to miss your hot target temperatures.
Chassis Setup Recommendations
For optimum performance the Hoosier P-Metric radial tires require about 3 degrees of negative camber. There will be a trade off in maximum performance to maximize wear. Generally, 1/2 degrees less than optimum will result in the best compromise for wear and speed. Less than 2.5 degrees negative can result in excessive wear on the outer shoulder junction. Higher pressures are needed when the vehicle has limited negative camber. The Hoosier tires typically offer better performance with spring/shock rates higher than previous brands you may have run.
TIRE PRESSURE RECOMMENDATIONS FOR COMPETITION
Traditionally, Hoosier tires have often required higher pressures than other brands. Hoosier recommends a starting minimum cold pressure of 26 psi on all DOT radials.
Roadrace/Track Applications

VEHICLE SIZERECOMMENDED HOT PRESSURECOLD PRESSURE
1800-2200 LBS.32-34+26-28
2200-2600 LBS.34-36+26-28
2600-3000 LBS.36-40+26-30
OVER 3000 LBS.40-42+30-34
Please contact a Hoosier Tire representative for cold pressure settings for vehicles over 3000 LBS.
+Higher pressures will improve the performance capability but will require a more sensitive feel to take advantage of the increase.

Air Pressures
One characteristic of new tires is the feeling of lower traction initially (when inflation pressures are correct). It is important to resist lowering the pressure to attempt to eliminate this feeling. Dropping the pressure too far may improve the “feel” of the tire however it will also lower the performance and increase the wear rate. Never drop hot tire pressures back down to cold pressure set points. Tires will be severely under inflated as a result of dropping hot pressures to cold pressure set points which will lead to increased tread wear and possible tire separation. Hot pressures will gradually return to the cold starting pressure as the tires cool off. For every 10 degrees F increase in air temperature, the tire pressure will gain approximately .7 psi. As Air Temperatures increase throughout the day, so will the Air Pressures in your tires. It is critical to maintain or manage your HOT air pressures throughout the day. Also, keeping the tires in the shade or out of direct sunlight will assist with consistent air pressure settings. Keep in mind that using compressed air (with moisture) and nitrogen (little to no moisture), will offer quite different air pressure increases. Compressed air will cause a faster increase of HOT air pressures while Nitrogen air pressure will cause a slower increase of operating HOT pressures. Using Nitrogen, cold air pressure settings need to be started at 2-3 psi higher compared to compressed air pressure settings. Also, depending on the morning air temperatures (50-60 degrees), both compressed air and Nitrogen require higher cold pressure settings to achieve the HOT pressures sooner. Using Nitrogen will offer more consistent air pressure readings, repeatable tire performance and improved overall results.
Banked Oval / Road Courses
Hoosier DOT radials are not intended for high banked super speedway or high speed and banked tracks like Watkins Glen International, however on these type of course configurations with the proper settings the tires can be used. In these situations, the loaded side tires should be elevated five (5) psi cold and hot above the normal road course pressure recommendations. Camber settings should be reduced to or below -2.0 degrees.
Autocross Applications
For autocross applications, your starting pressure for the first run should be within 1-2 psi of the recommended hot pressures shown above. After the first run and each subsequent run, keep resetting the pressures back to your target hot pressures before taking the next run. This way your tires are at the proper pressure during the bulk of every run you take. The above chart is a general recommendation which is intended for a standard configuration vehicle (i.e. front engine, rear wheel drive). Factors which can radically affect your pressure set up would include front wheel drive, independent rear suspension, rear engine, McPherson vs. control arm front suspension.
Front Wheel Drive
Vehicles configured with FWD are probably the most difficult application for a tire setup. The combination of steering, braking and accelerating on the front tires, combined with higher corner weights for the front positions produce a harsh environment for the tire. These vehicles will typically have a strut type of suspension which limits camber gain. All these factors result in conditions which require the tire do more work than a simple chart for pressures can accommodate. In severe cases front tire pressures for FWD vehicles can run in the 48-52 psi (hot) range. In cases where the tire size is limited to a relatively small tire, the required pressure can run even higher. The front to rear pressure differential on FWD cars can have extreme ranges of inflation, depending on the driver preference, suspension tuning, and track configuration
Rear Engine Vehicles
When matching a race tire to your rear engine vehicle, it is very critical in matching the OE (Original Equipment) rear tire diameter or size to the race tire. Having the same diameter or greater race tire will offer a higher load carrying capacity. If a shorter diameter tire is used, the race tire will overheat, overload and eventually fail. The same or taller diameter race tire will also offer a higher spring rated tire which will help absorb the shock of forward acceleration, provide higher cornering grip and less wheel spin during corner exit under power. More air pressure (2-3 psi) should also be used in the rear tires with this vehicle configuration.
Aero Package
Cold starting pressure needs to be considered setting at a higher pressure when using an aftermarket aero package. An aero package will produce more down force and will damage race tires if air pressure is not increased.
Independent Rear Suspension
With IRS and proper geometry up front, tire pressures can be reduced from the recommendations listed above. When there is adequate camber gain and good roll control, the Hoosier radial tire will perform very well at the reduced air pressure. This results in a bigger “sweet spot” and easier control at the limit. When tuning at reduced pressures use the following formula to determine the minimum safe pressure: Divide the total vehicle weight, including fuel and driver, by 100 to arrive at the minimum safe pressure. Example: Your car weighs 2750 lbs. as raced. The minimum safe (cold) pressure is 27.5 psi. Extreme care should be taken when tuning at reduced pressure. Tire damage can occur that is not visible to external inspection. Vehicles equipped with independent rear suspension (IRS) have a distinct advantage over non-IRS cars when using radial tires. This is true for two reasons. First, it is possible to setup some amount of static negative camber on IRS suspensions, if needed. Second, the IRS geometry can provide the proper camber gain to achieve the dynamic camber needed for a radial tire. This is a great benefit because it then becomes possible to better address front tire grip when the rear of the car can be optimized closer to the tire’s potential.
Considerations
These tires are molded to their designed tread depth. They do not require shaving to be prepared for competition use. Due to extremely light construction, Hoosier tires have a much lower polar moment of inertia than other radial tires. This translates to a very low rotational mass, which is a good thing for performance applications. The downside to this feature is that the tires do not resist “spikes” in braking force as well as a heavier tire might. As a result, there is a tendency for drivers to “flat spot” a tire the first time really getting to the limit. Vehicles equipped with ABS will benefit from its use. If you do not use ABS it is recommended that you make an effort to minimize stabbing the brakes until you have some experience with the feel of the tire under hard braking. The light construction also provides less protection from impact damage and punctures. Off course excursions or running over debris on the track will likely result in tire damage. Once some wear has occurred it may be desirable to flip the tire on the wheel in order to even out the wear and maximize tire life.
Wheel Widths
Wheel width dramatically affects the wear and performance of the Hoosier P-Metric radial tires. There is about a one inch window of optimum width. The trick is to figure out that window. A good rule of thumb to use for determining proper width is to use the tread width of the tire. Measure the tread width. Plus or minus 1/2 inch from the tread dimension will indicate the proper rim sizing. It is possible to use narrower wheels, but at a sacrifice to shoulder wear and cornering power.
“Measured” rim vs. “Recommended” rim
On our website tire specifications, you will see two columns of information regarding rim dimensions. In most cases, the “measured rim” and the “recommended rim” will be the same. However, in the case of DOT tires, the information may appear contradictory. The reason for the differences lies in the Department of Transportation requirements for publishing tire dimensions on any tire that carries a DOT certification. Each tire size has a specific rim that must be used when taking measurements for tire comparison. This is intended to allow consumers a consistent way to compare tire sizes between brands. With respect to the Hoosier P-Metric line, the recommended rim size will typically be wider than the DOT standardized wheel. The fact that a tire will “fit” on a rim is not an indication that it will work effectively in that condition. Radial tires are extremely sensitive to wheel widths. The performance characteristics of the tire can change significantly within the recommended range of application. Mounting a tire on a rim that is outside of the recommendation is not a good idea.
Driving Style/Braking
Driving style has also shown to significantly effect tire wear. Drivers who achieve their speed by “tossing” the car run the risk of increased tire wear. Radial tires develop their highest cornering power at relatively low slip angles. Smooth driving yields faster lap times and better tire wear. Drivers need to develop a sensitivity for the limits under braking. This takes time and practice. Failure to apply this will result in flatspotted tires. Particular care needs to be taken when selecting brake pad compounds. It is possible to have a pad that is too aggressive. This will make it very difficult to develop good braking feel for threshold braking.
Rain Tires
The Hoosier D.O.T. Radial tires are extremely good in dry conditions, however they do not make very good wet weather tires. Having dedicated rain tires available will be necessary for your team to be properly prepared. Hoosier Racing Tire also offers a D.O.T. Radial Wet tire. This tire has a molded tread of symmetrical design. Check the product catalog for the available sizes. The compound for these tires is intended for wet weather use only. When using rain tires, always increase your starting cold air pressure 2-4 psi over your dry tire starting pressures.
Speed Rating
The A7/R7 tire model carries a W Speed Rating of 168 mph.
SERVICE LIFE
Service Life for Race Tires: Old tires can fail in use, causing loss of vehicle control and personal injury. Environmental conditions like temperature extremes, exposure to sunlight, electric arc, solvents, automotive fluids, and atmospheric pollutants accelerate the aging process. Hoosier Racing Tire strongly recommends that new (sticker) tires should be put in service within 2 years of date of purchase. Used (scuffed) tires have a shorter service life than new (sticker) tires. Poor storage and infrequent use accelerate the aging process.
Did it mention a neck brace??? Cause you will need that too with A7s lol
 
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