NA Tire Clearance - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


Race Prep Miata race-only chat.
Sponsored by:
Sponsored by:

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 08-29-2015, 08:56 PM   #1
Newb
Thread Starter
 
Join Date: Oct 2014
Posts: 25
Total Cats: -11
Default NA Tire Clearance

I have my fenders pulled to about max to clear 225 Hoosiers with 4" pinch height. Now I'm fitting 275's so it's cutting & flaring time.

Assume we measure clearance by the pipe or socket diameter that will pass between tread and fender (at any angle). Someone have an idea of how much clearance to shoot for? This with 800/500 track springing and the 4" pinch height with Xida struts.

I know there are also turning issues, but for now I just want to prep my fenders. Currently a 1" deep socket will pass between tires and all four fenders. When I jack a corner and set it back down on a 4x4, no hitting. But I don't know if that's a good enough test.
MX5JER is offline   Reply With Quote
Old 08-30-2015, 10:10 AM   #2
Senior Member
 
Join Date: Apr 2011
Location: Hollywood, FL
Posts: 523
Total Cats: 18
Default

There is no standard for measuring or cutting of fenders for a Miata that I know of. And if there were it wouldn't be universal because people have different set-ups plus production variances are impossible to take into account. So you have to cut and check, simple as that.

What I did was put the big tires on and visualized where it would rub for the top of the fender and turned the wheel for the lower parts of the fender and front bumper.

On the rear its actually easier. Touch the inner fender panel at the top. You need to cut from there all the way around to about the line that runs down the middle of the car.

I have no rubbing issues with A6's with the fenders. They also dont rub the rear lower portion of the front fenderwell area. Lots of people have rubbing issues here but thats because they have either lower caster numbers, less offset wheels or spacers, or a tweaked chassis.

Where I do rub is at parking speeds against the front sway bar. And at speed against the shock mount. I dont have such bad rubbing issues here that destroy tires in a quick amount of time. I get 60+ runs out of A6's without cording from rubbing there so I dont care to try to get rid of it. This is with regular poly bushings, 949 offset 10" wheels with no spacer and 3.3* of camber. Lots of people trying to get rid of the rubbing on the shock mount will go with spacers on the wheel but then end up having rubbing issues with the bumper and fender support struts and the back portion of the front fenderwell area.

BTW, Im at 4" height and have 800/400 springs.
hector is offline   Reply With Quote
Old 08-31-2015, 04:51 PM   #3
Moderator
iTrader: (11)
 
sixshooter's Avatar
 
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 15,630
Total Cats: 1,559
Default NA Tire Clearance

:shrug: Install the shock assemblies without springs and gently lower it to see where it touches at full travel.
sixshooter is online now   Reply With Quote
Old 08-31-2015, 05:08 PM   #4
Supporting Vendor
iTrader: (3)
 
Join Date: Jul 2006
Location: San Diego
Posts: 2,862
Total Cats: 484
Default

Quote:
Originally Posted by sixshooter View Post
:shrug: Install the shock assemblies without springs and gently lower it to see where it touches at full travel.
This. With springs removed you can simulate all possible shock travel with a jack. Cut accordingly. No guessing, except for allowing for a bit of wiggle room for tire and bushing deflection.

-Ryan
ThePass is offline   Reply With Quote
Old 08-31-2015, 11:15 PM   #5
Newb
Thread Starter
 
Join Date: Oct 2014
Posts: 25
Total Cats: -11
Default

Makes perfect sense -- But a lot of work. I'll bet I can get the same results by just screwing down the perches to the bottom of the strut tubes. I'll check it out.
MX5JER is offline   Reply With Quote
Old 08-31-2015, 11:42 PM   #6
Elite Member
iTrader: (1)
 
Leafy's Avatar
 
Join Date: Jun 2012
Location: NH
Posts: 9,091
Total Cats: 90
Default

No. ******* do it right. Learn from the pile of corded hoosiers I disposed of learning the hard way.
Leafy is offline   Reply With Quote
Old 09-01-2015, 01:19 AM   #7
Supporting Vendor
iTrader: (3)
 
Join Date: Jul 2006
Location: San Diego
Posts: 2,862
Total Cats: 484
Default

If a bit of simple suspension work is too much for you to be bothered with, 275 Hoosiers might not be the right tire for you.

-Ryan
ThePass is offline   Reply With Quote
Old 09-01-2015, 01:23 AM   #8
Supporting Vendor
iTrader: (3)
 
Join Date: Jul 2006
Location: San Diego
Posts: 2,862
Total Cats: 484
Default

On second thought, switching to 275's at specifically this time of year... prepping for Nationals?

There are guys still ordering engine parts right now for Nationals. As in, internal bits. Be grateful you just need to remove/install some springs and do some body work over the next week.

-Ryan
ThePass is offline   Reply With Quote
Old 09-01-2015, 08:37 PM   #9
Senior Member
 
Join Date: Apr 2011
Location: Hollywood, FL
Posts: 523
Total Cats: 18
Default

Leafy, what was so fucked up on your car that you had such a tough time?

Seriously, I don't know what's so difficult. I cut my front fenders once, the bumper once, and folded/rolled the rear part of the front fender. That's it. I re-did the rears as I didn't take out enough from the top. You have to take out all of it from the top until you come in contact with the inner fender metal.

The 949 wheels are the perfect offset to still keep the car as narrow as possible. Yes I got some rubbing with the spring and shock mount but nothing that destroyed tires. And that's with the bulky NA shock mount. I get the start of cord after 60 runs on the inside. Tires were flipped at least twice and were always new. The current set have 65 runs and just barely show cord so I'm using them for at least one more event.


Attached Thumbnails
NA Tire Clearance-oehx4ec.jpg   NA Tire Clearance-etgojmd.jpg  
hector is offline   Reply With Quote
Old 09-01-2015, 08:45 PM   #10
Elite Member
iTrader: (1)
 
Leafy's Avatar
 
Join Date: Jun 2012
Location: NH
Posts: 9,091
Total Cats: 90
Default

You see where that chunk of rubber is. My car would cord tires there until I got the bump stop lengths correct to prevent it from happening. And even with the current bump stops, 15x10 6uls would probably kill a set of tires in like 2 runs, they're setup for 245s. If you're using 15x10 6uls without a 6mm spacer and not cording the **** out of 275s you're either giving up 3/8ths of an inch of bump travel or driving like a *****.
Leafy is offline   Reply With Quote
Old 09-01-2015, 09:04 PM   #11
Senior Member
 
Join Date: Apr 2011
Location: Hollywood, FL
Posts: 523
Total Cats: 18
Default

I'm using 6ul's without spacers. Furthermore, I'm on NA suspension components, will be going with NB components as soon as I get the itch to install the parts I have in my garage. That should space the wheels out 5mm. UCA bushings are not offset, 3.3* of camber and 4.5* of caster.

The previous shocks were Koni's with 2.5" springs and NA shock mounts. They had unknown bumpstops that were cut in half. These are Penske's. There is no bumpstop. The top of the inner fender is the bumpstop.

And while I'm not at the top of my game anymore as a driver, I bet I could put two seconds on you in your SSM car with me in my CSP car.

Given the set of compromises we have to make to fit these tires on these cars, I'd say I have mine fairly well set-up. Your car might just be fucked up. Or your set-up is fucked up.
hector is offline   Reply With Quote
Old 09-01-2015, 09:07 PM   #12
Elite Member
iTrader: (1)
 
Leafy's Avatar
 
Join Date: Jun 2012
Location: NH
Posts: 9,091
Total Cats: 90
Default

Cool story bro. The local csp car here ran 6uls and penske's with their previous owner just fine, that lasted about 3 runs with the current owners before a scramble for spacers to save the tires. And thats an NB which does have more tire room.
Leafy is offline   Reply With Quote
Old 09-01-2015, 09:12 PM   #13
Senior Member
 
Join Date: Apr 2011
Location: Hollywood, FL
Posts: 523
Total Cats: 18
Default

Cool story bro, you have one local csp car. That's all the data I needed. Now I know I drive like a *****
hector is offline   Reply With Quote
Old 09-01-2015, 09:14 PM   #14
Elite Member
iTrader: (1)
 
Leafy's Avatar
 
Join Date: Jun 2012
Location: NH
Posts: 9,091
Total Cats: 90
Default

Well I mean, the rest of the CSP cars havent won a national championship, there's more, but they're not like the caliber of cars that set top pax at national events.
Leafy is offline   Reply With Quote
Old 09-01-2015, 09:18 PM   #15
Senior Member
 
Join Date: Apr 2011
Location: Hollywood, FL
Posts: 523
Total Cats: 18
Default

Again, one data point. I wonder if we could get Tom Kubo to chime in. His car won on 949 wheels. Maybe Emilio knows of they used spacers.

Just because you've experienced one thing you have completely discredited my reality.
hector is offline   Reply With Quote
Old 09-01-2015, 11:00 PM   #16
Elite Member
iTrader: (6)
 
Join Date: Feb 2013
Location: Staunton, Va
Posts: 2,398
Total Cats: 200
Default

Pax = bracket racing = give me a head start and I'll still say I won. It's like handicapped golf scores. Lame.
ryansmoneypit is offline   Reply With Quote
Old 09-01-2015, 11:04 PM   #17
Supporting Vendor
iTrader: (31)
 
Savington's Avatar
 
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 14,353
Total Cats: 1,319
Default

Quote:
Originally Posted by hector View Post
Given the set of compromises we have to make to fit these tires on these cars, I'd say I have mine fairly well set-up. Your car might just be fucked up. Or your set-up is fucked up.
Nope. His setup is correct. The 15x10 6UL was optimized for the 245/40 tires (Hoosier and Maxxis) that didn't yet exist when it was created. You can call Emilio, he will gladly confirm that for you. The guys who were putting 275s on them quickly figured out that 6-8mm of spacer was required in the front to keep the tire from excessively contacting the shock tower. The narrower 245/40 doesn't require this spacer. This was before all the competitive 275 guys went to 15x11s.

I know Tom Kubo's codriver, Scott Fraser. He does all my alignments and consults on car setup for me. There were spacers in the front of that car.
Savington is offline   Reply With Quote
Old 09-02-2015, 07:30 AM   #18
Senior Member
 
Join Date: Apr 2011
Location: Hollywood, FL
Posts: 523
Total Cats: 18
Default

Thanks for the input Andrew. BTW, we ran a set of 245 A6's and they still rubbed there.

Now from what Leafy was saying, the 6-8mm worth of spacers were the difference between tires lasting 3 runs or tires lasting long enough to be considered adequate. I doubt 6-8mm of spacers gits rid of all the rubbing.

Also he states that I was giving up bump travel or driving like a *****. Obviously by looking at the picture you can tell I was not giving up bump travel since the shock tower is all rubbed out. He states that he is now the one giving up bump travel so I imagine he also raised the car up a bit to compromise.

And as far as driving like a *****, I've seen his national results and he drives like a *****. So why is he destroying his tires on the shock tower? Of course he does have a splitter so maybe the extra downforce? Not enough spring? Or is his car tweaked?

I'm no demon behind the wheel myself. I would easily be 1.5 seconds behind the top csp car at nats. Most of that is driver, some of that is car. If I find that 1.5 seconds or put someone in the car that can, will the tires get destroyed in 3 runs? We may never know.

Oh I have a set of NOS Goodyear DOT R tires in autox compound going on after next event. Those were even wider than the A6's. And I'm trying to talk Darrin Disimo into driving the car at local events. So maybe we will know.
hector is offline   Reply With Quote
Old 09-02-2015, 11:30 AM   #19
Supporting Vendor
iTrader: (31)
 
Savington's Avatar
 
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 14,353
Total Cats: 1,319
Default

Everyone rubs tires there (even 205/50 SM6s on 9s will rub there a little) but the photo you posted shows a lot more rubbing than what I would consider to be acceptable. The smooth rubber smears are OK, the built-up rough slag is not. You are definitely giving up speed, because when the tire hits the shock tower that hard, the car slows down. Get the tire off the shock tower and you are able to effectively use more of the bump travel available.

I'm not interested in the pissing match. Just the facts.
Savington is offline   Reply With Quote
Old 09-02-2015, 12:03 PM   #20
Senior Member
 
Join Date: Apr 2011
Location: Hollywood, FL
Posts: 523
Total Cats: 18
Default

Agreed, tire rubbing is not ideal. So in your opinion at least a +12 offset for a NA with 10" wheels?
hector is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
15x10 - 15x11 6UL @ 949 Racing emilio700 Wheels and Tires 151 06-02-2017 03:36 PM
1994 Spec Miata Race Car SM/SM2/SSM For Sale Quinn Cars for sale/trade 6 10-23-2016 08:58 AM
Hey everyone another n00b here Big_gumby Meet and Greet 80 10-05-2015 05:06 PM
6ULs for Sale in Green Bay JStoops Miata parts for sale/trade 0 09-28-2015 06:35 PM
Recommended Tire Temp for best friction thumpetto007 Race Prep 4 09-27-2015 06:16 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 10:24 PM.