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

Goblin Guru
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

Goblin Guru
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

Goblin Guru
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.
 

JBINTX

Goblin Guru
I thought I would re-visit this thread. We have a few new members here since last post one year ago.

I have started putting some miles on my Goblin. Mostly test runs and a little fun since I cannot register it in Texas for another 5 weeks. I have not gotten to a track yet either, since they have been closed until recently.

I started out at 22 psi in front and rear. I set up my alignment fairly close to the DIY recommendations from Lonny.

I have already noticed visual wear (very little) on the inside of all four versus the outside part of the tire. Of course, I have not taken many turns very hard.

I found the load chart for my specific tires - Proxes R1R 275/40/R17. Square setup. Of course the loads are way more than we have on the Goblin. Since I have not scaled my Goblin yet, I took some other's weight info and extrapolated the tire load inflation table. I assume that a straight line extrapolation is breaking down at the lower load weights - otherwise the numbers say to run 6 psi rear and 1 psi front. I know that is not correct. Track intensive guys above are talking 14-16 psi.

So, some input / thoughts, please!

GOBLINTOTAL LBS
1800​
(WITH 200 LB DRIVER)
Tire SizeREAR (EA)
540​
60%​
275/40R17FRONT (EA)
360​
40%​
PROXES R1R
EXTRAPOLATED DATAPUBLISHED DATA
PSI
1​
6​
13​
26​
29​
32​
35​
LOAD (LB)
360​
540​
800​
1268​
1378​
1488​
1598​
36.7​
36.7​
36.7​
LB/PSI
 

ctuinstra

Goblin Guru
I agree, you can't run them flat. I'm sure that doesn't scale in a linear fashion.

We run 12-18 area. You are never going to get a lot of miles out of the very soft compound tires. Our first set lasted 4K (1 year) and they were bald pretty much all the way around. This set we went to the R1R and they have the same treadwear but are doing much better but still wearing.
 

Indy Lonnie

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).
Thanks for your input. I have been experiencing the same sketchy side to side slippage. I just checked and I was at 17psi in the rear. I just aired them up to 20. Hopefully that feeling will go away as yours did.
Again - thanks for input. I was about to drop more $ on wider tires. Hopefully this will help with the problem.
 

Briann1177

Goblin Guru
I run 20 PSI all around. I currently have about 6000 miles on my RE-71Rs. They are wearing very well in the rear. I anticipate getting at least 12-15k out of them and hopefully maybe closer to 20k.

My fronts are a different story. They were put on at the same time as the rears and the belts are showing on the inside. I'm going on my third set of front tires in 12k miles of driving.
 

JBINTX

Goblin Guru
I run 20 PSI all around. I currently have about 6000 miles on my RE-71Rs. They are wearing very well in the rear. I anticipate getting at least 12-15k out of them and hopefully maybe closer to 20k.

My fronts are a different story. They were put on at the same time as the rears and the belts are showing on the inside. I'm going on my third set of front tires in 12k miles of driving.
12k!!!!!!!!!
We need to start a new thread with ongoing updates on how many miles logged on their Goblin.
Or, number of track days.
Or, number of auto-X's.
:)
 

Indy Lonnie

Well-Known Member
I just got back from trying 20 psi in the rear of my RE-71Rs. So much better. They are clawing now instead of the side to side weirdness... They are still hazing a lot through second and third, but 100% improvement.
Thanks for everyone's input.
 
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