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Skulptorchaz
Samba Member
Joined: June 11, 2013
Posts: 839
Location: S.E. Indiana
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 Posted: Tue Jun 27, 2017 1:40 pm Post subject: Tire pressure for Autocross? |
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Just curious guys.
I want to eventually run a little AC, altho my buggy isn't set up perfectly for it. (Too wide of front tires, stock suspension, etc.) But just for the heck of it, I was wondering what pressures you ran and I was going to just go out and play a little to see how it handled. I'm not so competitive as to spend the bucks to truly "compete" but, I would like to set it up with what I have for the most fun/speed possible. 
I usually run 20# but I dropped it to 17 this weekend. I could feel a noticeable difference. BTW, I run BFG T/A's.
I went to a VW drag race, swap meet and car show this weekend and I think it would be a great place, and event, for an AC race. I fired it past one of the sponsors and he said they had talked about it. I don't know of any AC races around the Cincinnati area.
Thanks!! |
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Dale M.
Samba Member
Joined: April 12, 2006
Posts: 20380
Location: Just a tiny bit west of Yosemite Valley
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| Posted: Tue Jun 27, 2017 7:27 pm Post subject: Re: Tire pressure for Autocross? |
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The best answer will be you have to try it your self, car weight, balance your horse power driving style all have effect...
Best solution is get in-fired thermometer and do a lap and then take readings, What you are looking for is same temperature across width of tire... If outer edges are warmer than center tire is under inflated, if center is warmed than outer edges tire is over inflated...
You need to get tire temperature chart and keep record if serious, if play thing just use normal every day street pressures...
Be creative make your own chart(s) similar to above... Might also want to have line for date, air temp, pavement type and temperature...
https://nasaspeed.news/tech/wheels-tires/tuning-ti...racetrack/
http://www.fluke.com/fluke/uses/comunidad/fluke-news-plus/articlecategories/automotive/racetracktemp
Dale
_________________
“Fear The Government That Wants To Take Your Guns" - Thomas Jefferson.
"Kellison Sand Piper Roadster" For Street & Show.
"Joe Pody Sandrover" Buggy with 2180 for Autocross (Sold)
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All suggestions and advice are purely my own opinion. You are free to ignore them if you wish ... |
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Skulptorchaz
Samba Member
Joined: June 11, 2013
Posts: 839
Location: S.E. Indiana
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| Posted: Wed Jun 28, 2017 6:08 am Post subject: Re: Tire pressure for Autocross? |
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Cool. Thanks Dale. I did not know any of that. I have an infrared therm and can do that.
Tis true, I am just playing with what I have but, I'd like to set up what I have to perform the best it can. That part to me is fun. Dropping the big bucks for just a little more performance is hard for me to swallow.
Thanks again buddy!!! |
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Dale M.
Samba Member
Joined: April 12, 2006
Posts: 20380
Location: Just a tiny bit west of Yosemite Valley
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| Posted: Wed Jun 28, 2017 6:26 am Post subject: Re: Tire pressure for Autocross? |
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This car was built for auto cross only... Tires are "Formula Ford" and are on custom 13 inch wheels...
Fronts tire are 20.0/6.0 X 13 and rears are 22.5/7.6 X 13 on rears... Really soft compounds... As will almost peel off rubber on really hot days and so soft rocks will actually stick to flat surface of tire... IF serious auto crosser (maybe in future if the "bug" really bites you) this is where you may want to go...
Dale
_________________
“Fear The Government That Wants To Take Your Guns" - Thomas Jefferson.
"Kellison Sand Piper Roadster" For Street & Show.
"Joe Pody Sandrover" Buggy with 2180 for Autocross (Sold)
============================================================
All suggestions and advice are purely my own opinion. You are free to ignore them if you wish ...
Last edited by Dale M. on Sat Jul 01, 2017 8:41 am; edited 1 time in total |
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Skulptorchaz
Samba Member
Joined: June 11, 2013
Posts: 839
Location: S.E. Indiana
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| Posted: Wed Jun 28, 2017 7:09 am Post subject: Re: Tire pressure for Autocross? |
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Thanks Dale. The bug may bite but the wallet says "tough".
Is there a "ball park" pressure to start with? Just a starting point? |
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slalombuggy
Samba Member
Joined: July 17, 2010
Posts: 9147
Location: Canada
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| Posted: Wed Jun 28, 2017 9:34 am Post subject: Re: Tire pressure for Autocross? |
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It's going to take some playing around as Dale said but on a relatively tall street tire you will want to start out around 20psi maybe a bit higher in the rear. Besides temps across the tread you will also want to study the sidewalls for evidence of the tires rolling over if the pressure is too low.
Besides the cost of slicks, the actual cost of setting up the suspension with some trick parts is relatively low. But once you go to slicks yu'll never go back. I ran 20.5x7 and 22x9 slicks on my buggy and had a huge $#!^ eating grin on my face every time I ran. It was so hard to go back to "R" compound tires once I fit disk brakes on the car and 13" wheels wouldn't fit.
brad |
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Dale M.
Samba Member
Joined: April 12, 2006
Posts: 20380
Location: Just a tiny bit west of Yosemite Valley
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| Posted: Fri Jun 30, 2017 3:06 pm Post subject: Re: Tire pressure for Autocross? |
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A 1360 pound car (empty weight) with "setup suspension" and wheels and tire with about 120 HP at the rear wheels is like "Mr Toads Wild Ride" you will want to do it forever...
Dale
_________________
“Fear The Government That Wants To Take Your Guns" - Thomas Jefferson.
"Kellison Sand Piper Roadster" For Street & Show.
"Joe Pody Sandrover" Buggy with 2180 for Autocross (Sold)
============================================================
All suggestions and advice are purely my own opinion. You are free to ignore them if you wish ... |
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hillmotorsports
Samba Member
Joined: December 27, 2014
Posts: 432
Location: Morrisburg, Ontario, Canada
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| Posted: Sat Jul 01, 2017 4:40 am Post subject: Re: Tire pressure for Autocross? |
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Dale
What engine were you using for your 120hp smile machine? 
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Rosemarie and Paul Hill
Morrisburg, Ontario
(With way more projects than spare time!) |
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Dale M.
Samba Member
Joined: April 12, 2006
Posts: 20380
Location: Just a tiny bit west of Yosemite Valley
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| Posted: Sat Jul 01, 2017 8:40 am Post subject: Re: Tire pressure for Autocross? |
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| hillmotorsports wrote: |
Dale
What engine were you using for your 120hp smile machine? |
2180 at about 9.5:1 CR (maybe a bit more) with medium cam good for all RPM ranges and dual Weber 44 IDF's...
I never dynoed motor when I owned car, new owner put it on dyno a few day after buying car and emailed me that it was 120 HP at the wheels... So at crank, maybe 150 HP...
Dale
_________________
“Fear The Government That Wants To Take Your Guns" - Thomas Jefferson.
"Kellison Sand Piper Roadster" For Street & Show.
"Joe Pody Sandrover" Buggy with 2180 for Autocross (Sold)
============================================================
All suggestions and advice are purely my own opinion. You are free to ignore them if you wish ... |
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hillmotorsports
Samba Member
Joined: December 27, 2014
Posts: 432
Location: Morrisburg, Ontario, Canada
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| Posted: Sat Jul 01, 2017 10:15 am Post subject: Re: Tire pressure for Autocross? |
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Now that's about right for a buggy isn't it...
As they say...no such thing as too much power.
I sense more than a few jealous readers!
Paul
_________________
Rosemarie and Paul Hill
Morrisburg, Ontario
(With way more projects than spare time!) |
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Skulptorchaz
Samba Member
Joined: June 11, 2013
Posts: 839
Location: S.E. Indiana
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| Posted: Mon Jul 03, 2017 9:31 am Post subject: Re: Tire pressure for Autocross? |
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| That would be me. |
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Dale M.
Samba Member
Joined: April 12, 2006
Posts: 20380
Location: Just a tiny bit west of Yosemite Valley
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| Posted: Mon Jul 03, 2017 9:56 am Post subject: Re: Tire pressure for Autocross? |
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| hillmotorsports wrote: |
Now that's about right for a buggy isn't it...
As they say...no such thing as too much power.
I sense more than a few jealous readers!
Paul |
My street buggy is 2084 and is only estimated at 100hp at wheels.... It's enough to make most tuner and a few "hot dogs" look bad...
Dale
_________________
“Fear The Government That Wants To Take Your Guns" - Thomas Jefferson.
"Kellison Sand Piper Roadster" For Street & Show.
"Joe Pody Sandrover" Buggy with 2180 for Autocross (Sold)
============================================================
All suggestions and advice are purely my own opinion. You are free to ignore them if you wish ... |
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Skulptorchaz
Samba Member
Joined: June 11, 2013
Posts: 839
Location: S.E. Indiana
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| Posted: Mon Jul 03, 2017 10:02 am Post subject: Re: Tire pressure for Autocross? |
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| Always a good thing. |
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