Tire Pressures

ncgoblin

Well-Known Member
I am currently running 14psi rear and 12 in the front 235x15 front 275x16 rear do you guys feel this is to low? I do plan to autocross monthly.
 

Christopher Sanchez

Well-Known Member
According to what ive found online the Ariel Atom 3 runs 20 in the Rear and 18 up front. 190/50/15 I figure 20 on all 4 sounds good 235 17R
 

Waterdriver

Well-Known Member
I am currently running 14psi rear and 12 in the front 235x15 front 275x16 rear do you guys feel this is to low? I do plan to autocross monthly.
It sounds like your right in the range already, for a hot tire pressure reading.
To aid in tire pressure tuning, I've been using a Harbor Frieght temp gun with laser pointer to get tire temp readings. This will help give some feedback if your pressure is too high or low or camber changes are needed. Used not so much for the actual tire temp, but temp differential across the surface of the tire. (Best to check immediately after you pull in from a run)
You'll want the temp from inside, middle and the outside tread surface roughly all the same temp.
Example. If the middle of the tire temp is high and the inside and outside temps are the same but lower, drop your tire pressure.
If the opposite tire temps are observed, raise the tire pressure.
As to the amount of pressure to change by depends on what you start with but if your starting with 12F/14R, adjust in 1psi increments.

You'll also want to check that you using the whole tires surface. Meaning the tire, while cornering, should roll over onto or to the outside edge of the shoulder. An easy way to see this is make a mark on the outside tread shoulder area, in two spots on each tire, with a tire crayon or shoe polish each run to see where its wearing to.
This too will aid in finding the right air pressure and also too much or too little negative camber.

Sorry if I rambled. There is lots of info out there on the Internet regarding this to research. As well as talking to some of the veteran autocrosser's when your at an event.

Have fun and Good Luck!
 

ncgoblin

Well-Known Member
It sounds like your right in the range already, for a hot tire pressure reading.
To aid in tire pressure tuning, I've been using a Harbor Frieght temp gun with laser pointer to get tire temp readings. This will help give some feedback if your pressure is too high or low or camber changes are needed. Used not so much for the actual tire temp, but temp differential across the surface of the tire. (Best to check immediately after you pull in from a run)
You'll want the temp from inside, middle and the outside tread surface roughly all the same temp.
Example. If the middle of the tire temp is high and the inside and outside temps are the same but lower, drop your tire pressure.
If the opposite tire temps are observed, raise the tire pressure.
As to the amount of pressure to change by depends on what you start with but if your starting with 12F/14R, adjust in 1psi increments.

You'll also want to check that you using the whole tires surface. Meaning the tire, while cornering, should roll over onto or to the outside edge of the shoulder. An easy way to see this is make a mark on the outside tread shoulder area, in two spots on each tire, with a tire crayon or shoe polish each run to see where its wearing to.
This too will aid in finding the right air pressure and also too much or too little negative camber.

Sorry if I rambled. There is lots of info out there on the Internet regarding this to research. As well as talking to some of the veteran autocrosser's when your at an event.

Have fun and Good Luck!
Well I ran my first auto cross today lots of fun. I had 20 psi all around and that was very challenging keeping it together. I ended up lowering to 12 in front 14 rear and what a massive difference. I also obviously was getting more comfortable with the car too but I noticed even when I made mistakes it was easier to recover. At 20 psi I spun out on my final turn and learned this car does not let you know like when I had an s2000 it’s very quick loss of control.

Also I enjoyed riding a long in a GT350R which was amazing with an experienced driver.

Anyways that’s my 2 cents.

Thanks
 

DCMoney

Well-Known Member
Well I ran my first auto cross today lots of fun. I had 20 psi all around and that was very challenging keeping it together. I ended up lowering to 12 in front 14 rear and what a massive difference. I also obviously was getting more comfortable with the car too but I noticed even when I made mistakes it was easier to recover. At 20 psi I spun out on my final turn and learned this car does not let you know like when I had an s2000 it’s very quick loss of control.

Also I enjoyed riding a long in a GT350R which was amazing with an experienced driver.

Anyways that’s my 2 cents.

Thanks
Are those PSI's at hot or cold tire temps?
 

ctuinstra

Well-Known Member
We ran with much less in the rear (I can't remember exactly now, 15-16psi) and I hated the feel. It felt like the rear would constantly slip from side to side about an inch or two before it would hook, and this is just everyday driving. It was a really weird feeling. Pumped them back up to around 20 took care of that but for overall traction and wear, it should probably be less than 20. I think with the lightness and the width of these tires, the exact amount will be very critical and will change depending on many factors (temps, driving, wear, etc).
 

Waterdriver

Well-Known Member
Well I ran my first auto cross today lots of fun. I had 20 psi all around and that was very challenging keeping it together. I ended up lowering to 12 in front 14 rear and what a massive difference. I also obviously was getting more comfortable with the car too but I noticed even when I made mistakes it was easier to recover. At 20 psi I spun out on my final turn and learned this car does not let you know like when I had an s2000 it’s very quick loss of control.

Also I enjoyed riding a long in a GT350R which was amazing with an experienced driver.

Anyways that’s my 2 cents.

Thanks
Glad to hear that you had a good time and lower tire pressure helped out!

With the higher tire pressure, I agree, the car is a handful and not in a good way.
 
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