why run 15X9 wheels and only use a 225 tire? - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


Wheels and Tires All things related to Miata Wheels and Tires.
Sponsored by:
Sponsored by:

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 07-22-2010, 02:08 PM   #21
Elite Member
 
Join Date: Jul 2005
Location: Anacortes, WA
Posts: 2,476
Total Cats: 114
Default

Quote:
Originally Posted by owengt View Post
My suspension is set up where I use 100% of the bump travel available before the tire hits metal on the inner fender both front and rear using 225/45/15. I can squeak by with a 225/50/15 if I accept a bit of rubbing. a 235/50/15 aunt going to work right without some more modifications like limiting bump travel or tubbing out the fender wells.

I have my car setup and run 275/35/15’s for autocross with a slight bit of rubbing on the inboard side so I can make big width fit but the big thing is diameter needs to be really close to stock to work on a properly set up Miata that retains original sheet metal inner fender. This narrows the tire selection pool a lot. Need like a 40 aspect ratio or less to go wider.

Bob
bbundy is offline   Reply With Quote
Old 07-22-2010, 02:11 PM   #22
Elite Member
 
Join Date: Jul 2005
Location: Anacortes, WA
Posts: 2,476
Total Cats: 114
Default

Quote:
Originally Posted by jawd75 View Post
2. 15x9s with 225s are faster than 15x8s with 225s, end of story

Does anyone else agree with this? seems that a 15X8 with a 225 would be a better choice and a lighter set up as well. I was also just concerned with street tires. So I guess I was just trying to find out if there was any real benefit from the 15X9. Thanks for all the input.
Tested myself Back to Back with the same tires mounted on a track. Better feel at the limit and more grip mounted on the 9", dropped a tad over a second.

Now if your only conscerned about the street, the lightest wheels you can get makes the car feel zippy and the narrower rims give a smoother ride.

Bob

Last edited by bbundy; 07-22-2010 at 04:59 PM.
bbundy is offline   Reply With Quote
Old 07-22-2010, 03:04 PM   #23
Supporting Vendor
iTrader: (31)
 
Savington's Avatar
 
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 14,362
Total Cats: 1,323
Default

Quote:
Originally Posted by jawd75 View Post
Does anyone else agree with this? seems that a 15X8 with a 225 would be a better choice and a lighter set up as well. I was also just concerned with street tires. So I guess I was just trying to find out if there was any real benefit from the 15X9. Thanks for all the input.
Stopwatches don't lie, dude.
Savington is offline   Reply With Quote
Old 07-22-2010, 07:43 PM   #24
Tour de Franzia
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

I've driven a 225 and a 205 on an 8 and the 205 felt much better. The slight stretch is how its supposed to be done and you can see that executed on any and every big-budget racecar. The 225 on the 9 feels incredible and makes the car feel precise.
hustler is offline   Reply With Quote
Old 07-22-2010, 07:53 PM   #25
Senior Member
iTrader: (22)
 
Join Date: Oct 2007
Location: bay area, ca
Posts: 551
Total Cats: 19
Default

I went from low tread (but still fast) ra1s on 15x8s to new nt01s on 15x9s. The 9s were noticeably grippier. Not the most controlled experiment, but enough to convince me that 9s are faster and now I don't bother using the 8s on the track anymore.
orion4096 is offline   Reply With Quote
Old 07-23-2010, 06:00 PM   #26
Junior Member
iTrader: (1)
 
Join Date: Jan 2008
Location: Oahu, Hawaii
Posts: 87
Total Cats: 1
Default

Same here. I switched from 15x8 to 15x9 this season and they are much nicer, faster turn-in and more grip.
EvoRoadster is offline   Reply With Quote
Old 07-24-2010, 10:16 AM   #27
Supporting Vendor
iTrader: (31)
 
Savington's Avatar
 
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 14,362
Total Cats: 1,323
Default

The biggest thing I noticed was turn-in crispness. The 9s have so much more feel and feedback than the 8s did.
Savington is offline   Reply With Quote
Old 07-24-2010, 10:56 AM   #28
Cpt. Slow
iTrader: (25)
 
curly's Avatar
 
Join Date: Oct 2005
Location: Oregon City, OR
Posts: 12,105
Total Cats: 518
Default

I feel like the guy with a small ***** in a gang bang scene.

225 on my 7" wheels were much gripper than the 185 stock tires obviously, but it was noticeably squishier, if that makes sense. It lost some of it's immediate turn in crispness.
curly is offline   Reply With Quote
Old 07-24-2010, 11:37 AM   #29
Supporting Vendor
iTrader: (31)
 
Savington's Avatar
 
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 14,362
Total Cats: 1,323
Default

I codrove a big-boost M45 at an autocross like 3 weeks ago, and since I'm an elitist ***** we swapped his 205/55-14 NT-01s on 14x6s for a set of 9s and 225s. His comment after his first run was just "wow".
Savington is offline   Reply With Quote
Old 07-24-2010, 12:08 PM   #30
Tour de Franzia
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

Back when i ran 99 wheels with 205 NT-01's it was pretty easy to put that tire on the dime. I had a revellation after about 4-track days on the 9's....I wasn't using the tire. The limit on 9's compared to skinnies is so far out that I couldn't really comprehend the limit. You I have to really scare the **** out of myself to "use" the 9's.
hustler is offline   Reply With Quote
Old 07-26-2010, 02:38 PM   #31
Elite Member
 
Join Date: Jul 2005
Location: Anacortes, WA
Posts: 2,476
Total Cats: 114
Default

The big difference that I notice between an 8” and a 9” with the 225’s is like in say a 90mph sweeping turn. Where your sphincter is puckered to begin with. Even worse on a 7”. I think 205 is as wide as should be mounted on a 7”.

With the narrower wheel you feel the tires outer edge kind of roll under and dig in with the slip angle changing less with cornering force changes as you near the traction limit then as you go over the limit it kind of pops loose and when you bring it back in it snaps back. The behavior is more non linear. With the wider wheels the slip angle to cornering force relationship near the traction is much more linear and you can drive more smoothly at and even slightly over the limit. The increase in ability to get everything out of the tire is as much to do with the lower lap times as the increase in grip levels.

Bob
bbundy is offline   Reply With Quote
Old 07-26-2010, 03:02 PM   #32
Elite Member
iTrader: (12)
 
Join Date: Sep 2007
Location: Charlotte, NC
Posts: 6,868
Total Cats: 66
Default

Got sidewall stability?
I'd imagine it's the same difference I felt between a 235/40 and 215-40 tires on a 17x7.5 wheel. Though the 235 felt like it had more available grip, steering input and at the limit driving felt a bit more muted.
Doppelgänger is offline   Reply With Quote
Old 07-26-2010, 07:37 PM   #33
Elite Member
 
Join Date: Jul 2005
Location: Anacortes, WA
Posts: 2,476
Total Cats: 114
Default

Quote:
Originally Posted by Doppelgänger View Post
Got sidewall stability?
I'd imagine it's the same difference I felt between a 235/40 and 215-40 tires on a 17x7.5 wheel. Though the 235 felt like it had more available grip, steering input and at the limit driving felt a bit more muted.
My suspension setup won't work with tires that big of diameter. Id have to remove at least 1/2" of bump travel probably 3/4".

Bob
bbundy is offline   Reply With Quote
Old 08-07-2013, 10:26 PM   #34
Junior Member
 
Join Date: Apr 2013
Location: toronto
Posts: 124
Total Cats: 7
Default

on a 85 sec race track, gained a consistent 1.5-2 sec going from a 15x7 to 15X9. everything else constant. 225 R888's.
endura is online now   Reply With Quote
Old 08-08-2013, 12:28 AM   #35
Elite Member
iTrader: (1)
 
cordycord's Avatar
 
Join Date: Dec 2011
Location: SoCal
Posts: 1,775
Total Cats: 148
Default

That's one of the nice things about setting up the Catfish; our "stock" setup is 245/35's on 17x9's. Although there's limited rubber at that size (Toyo R1R), the word that does come to mind is "wow" after you've had a chance to sample the cornering grip. Tires are at 20psi.
cordycord is offline   Reply With Quote
Old 08-08-2013, 03:37 PM   #36
Junior Member
 
Join Date: Apr 2013
Location: toronto
Posts: 124
Total Cats: 7
Default

Quote:
Originally Posted by cordycord View Post
That's one of the nice things about setting up the Catfish; our "stock" setup is 245/35's on 17x9's. Although there's limited rubber at that size (Toyo R1R), the word that does come to mind is "wow" after you've had a chance to sample the cornering grip. Tires are at 20psi.
20psi hot? car weight?
endura is online now   Reply With Quote
Old 08-08-2013, 04:37 PM   #37
Elite Member
iTrader: (1)
 
cordycord's Avatar
 
Join Date: Dec 2011
Location: SoCal
Posts: 1,775
Total Cats: 148
Default

Quote:
Originally Posted by endura View Post
20psi hot? car weight?
20psi cold with a 1,550lb car. I'm pretty confident 18-19psi would be even better for track days.

The Thunderhill car weighed more than this with a full cage and started at 26psi. They quickly found out that the car was using only a fraction of its tire. I think they carefully dropped 5-6psi by the end of the race, which is a huge margin.

We ran the car with a naked frame through an autocross course with some 949 15x9's, and the tire tread did not start to roll to the edge until 21psi, with national champion auto crossers driving. The vid is on the website.

It's takes some talent and patience to be able to make suspension, spring rates, camber, sway bars and tire pressure all work together.
cordycord is offline   Reply With Quote
Old 08-08-2013, 04:37 PM   #38
Tour de Franzia
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

We do this thread every six months. You want a slight stretch, makes the car feel great and handle sharply. There is a reason this is done on real racecars.
hustler is offline   Reply With Quote
Old 08-08-2013, 06:14 PM   #39
Senior Member
iTrader: (1)
 
Join Date: Dec 2010
Location: Farmington Hills, MI
Posts: 873
Total Cats: 93
Default

All I've heard so far is, wider wheels are faster! Well, they are. The slight stretch increases cornering stiffness of the tire. If you look at the tire slip angle curve below (slip angle on x-axis, lateral force on y-axis), there is the region that is linear (from 0 to a some small slip angle). Being able to see the values on the graph doesn't matter, because depending on the tire size/compound/etc could range from 2 degrees to 13. Cornering stiffness measures the slope of that linear portion as it crosses the graphs origin. Increasing cornering stiffness may not increase peak force (though sometimes it does!), but more importantly it makes the tire build force faster (increasing response), and overall nets a greater area under the curve.

Attached Thumbnails
why run 15X9 wheels and only use a 225 tire?-tire_slip_angles.jpg  
acedeuce802 is offline   Reply With Quote
Old 08-09-2013, 07:10 PM   #40
Junior Member
iTrader: (2)
 
Join Date: Mar 2008
Location: Irvine, Ca
Posts: 277
Total Cats: 23
Default

Quote:
Originally Posted by Savington View Post
I codrove a big-boost M45 at an autocross like 3 weeks ago, and since I'm an elitist ***** we swapped his 205/55-14 NT-01s on 14x6s for a set of 9s and 225s. His comment after his first run was just "wow".
Wow
cjsafski is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
3rd Time's a Charm...hopefully. zephyrusaurai Meet and Greet 2 09-28-2015 11:59 PM
wiring wideband ground to battery terminal btabor ECUs and Tuning 10 09-28-2015 06:33 PM
Another Alternator thread ihiryu General Miata Chat 9 09-28-2015 11:22 AM
BP-6D on CAS only aidandj MEGAsquirt 14 09-25-2015 06:26 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 11:15 AM.