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Thread: tire set up

  1. #1
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    tire set up

    looking through the brammo manual it had a set up of 18 psi and 20 psi f/r for the advan tires.

    I replaced them with proxes r888r. the manufacturer literature says hot tire pressure of 32 to 38 psi.

    that seems awfully high for a car of this weight no?

    whats your tire set up and what pressures are you starting out cold and aiming for hot?

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    Lepton cvjoint's Avatar
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    Quote Originally Posted by fergustsi View Post
    looking through the brammo manual it had a set up of 18 psi and 20 psi f/r for the advan tires.

    I replaced them with proxes r888r. the manufacturer literature says hot tire pressure of 32 to 38 psi.

    that seems awfully high for a car of this weight no?

    whats your tire set up and what pressures are you starting out cold and aiming for hot?
    Optimal tire pressure is a bit of a complicated science. In my view, the r888 is not really a good tire for this car. You will basically never get that tire hot enough to get peak grip, not even close. That means you are at a boundry condition. It may help to run really low pressures to get the sidewall to flex and build some heat, probably as low as you can without getting the tire to slip off the wheel. Toyo seems to have designed the new tire for heavier cars, gave it a compound optimized for higher temps and a stiffer sidewall. It's not going to work on the Atom as well as the old one.

    I only use my Atom on track. My tires are meant for formula cars, I start them at 16psi and get them to 19-20psi where they are meant to operate. Except for really cold days in the winter I always reach optimal temps and pressures.

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    Quote Originally Posted by fergustsi View Post
    looking through the brammo manual it had a set up of 18 psi and 20 psi f/r for the advan tires.

    I replaced them with proxes r888r. the manufacturer literature says hot tire pressure of 32 to 38 psi.

    that seems awfully high for a car of this weight no?

    whats your tire set up and what pressures are you starting out cold and aiming for hot?
    32-38 psi is for a 3,000 lb. car. You want to run closer to 15 psi front and 20 psi rear.

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    Toyo says optimal tire temp is between 160-220. You don’t think they’ll get that? I mean I know it’s a light car, but ambient temp in Texas is like 100 in summer. What sort of tire non slick is recommended then? Or should I only be running slicks?

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    Quote Originally Posted by fergustsi View Post
    Toyo says optimal tire temp is between 160-220. You don’t think they’ll get that? I mean I know it’s a light car, but ambient temp in Texas is like 100 in summer. What sort of tire non slick is recommended then? Or should I only be running slicks?
    To give you an idea, pounding the car 20 minutes on track the most I ever got was 170* in the 225 section rears in 103* ambient. There is no street I could drive the Atom that hard for 20 minutes due to debris on the road, uneven pavement surface, traffic, and general risk to other motorists.

    Amazon sells a nice $100 pyrometer. It's probably the most useful tool to figure out this car. Optimizing tire choice is where the bulk of the performance can be unlocked.

    Look for autocross grade tires, especially the ones that cheat heavily on their thread rating. You want the softest compound with the lowest operating heat range, something like 110* to 130*. If you see autocrossers spray them once they get over 130*, that's your tire.

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    So I’m only going to be tracking the car for now, no street use. Would a c temp rating help? I can’t seem to find too much specific info on temp operating ranges really. Any specific tire recs?
    im certainly not anywhere near a pro at all, been tracking my m6 and just made the switch and finally took my atom out for the first time yesterday. We ran pressures of 25,spun twice. Have a pyrometers from joes garage brand, intend to take good measurements and adjust etc with y’alls help of course. Had a blast my first time out.

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    Lepton cvjoint's Avatar
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    Quote Originally Posted by fergustsi View Post
    So Iím only going to be tracking the car for now, no street use. Would a c temp rating help? I canít seem to find too much specific info on temp operating ranges really. Any specific tire recs?
    im certainly not anywhere near a pro at all, been tracking my m6 and just made the switch and finally took my atom out for the first time yesterday. We ran pressures of 25,spun twice. Have a pyrometers from joes garage brand, intend to take good measurements and adjust etc with yíalls help of course. Had a blast my first time out.
    I'm not sure how the temp ratings work on street tires. The manufacturer will at times respond to inquiries, so I would start there. Hoosier definitely responded to my questions. Usually if the tire is not marketed for autocross or with the term soft, it's likely too hard and needs too much heat.

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    For a track only Atom you really need to get R-comps or slicks. For R-comps - Hoosier R7 or A7 as well as BFG R1 or R1S all work well. CVJOINT uses slicks (like Hoosier RB25) and he seems to really like them but they come in odd sizes and you have to have the right rims for them. Not sure what size rims you have but on the SRAs - stock they came with 15x7 all around and Hoosier R7s. F: 205/50 R: 225/50.

    Spinning an Atom the first time out is kind of like a right of passage (been there, done that). I've been doing track days for over a decade and have driven a wide variety of cars but most of my time was spent in Vette's, Miata's and Mustang. Going to the Atom was a whole new experience and it took me a good 6-7 days before I felt really comfortable in the car. Still got lots to learn (like braking later) but the loose rear end no longer bothers me.

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    This is a car I really like with a tad bit of understeer at the limit. To get that I would say stagger the tires as much as you can, best to keep the front sized about the same (to get enough heat into them) but go significantly wider rear. This will allow you to steer the car on throttle without the back end coming around too easily. It's most important in high speed turns where I really shy away if the car is nervous under me. You can always trail brake to get it to rotate but if it's tuned for no understeer or oversteer it will dance under breaking and give you some scary times in high speed turns.

    Naturally, this is how most 911s are shod, highly staggered, and our weight distribution is even a bit more rear biased.

    I've been trying to understand why Ariel sized the tires 205/225 on this car when something more like 185/255 would have worked a lot better.

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    If im going to go the slick route like a7, do I have to upgrade the upright? Are there any other options besides the palatov?

    i has several sessions yesterday got he rear tires up to 145 or so, front 130s on roughly 18/20 cold pressures.
    Those temps are in optimum range for the a7s.

    Ive heard putting slicks can cause catastropphic failure though (atom 2 here).

    thoughts?




    Quote Originally Posted by cvjoint View Post
    This is a car I really like with a tad bit of understeer at the limit. To get that I would say stagger the tires as much as you can, best to keep the front sized about the same (to get enough heat into them) but go significantly wider rear. This will allow you to steer the car on throttle without the back end coming around too easily. It's most important in high speed turns where I really shy away if the car is nervous under me. You can always trail brake to get it to rotate but if it's tuned for no understeer or oversteer it will dance under breaking and give you some scary times in high speed turns.

    Naturally, this is how most 911s are shod, highly staggered, and our weight distribution is even a bit more rear biased.

    I've been trying to understand why Ariel sized the tires 205/225 on this car when something more like 185/255 would have worked a lot better.

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