Autox/Autocrossing a Mazda MX-6

[miatatude]

Sounds like your car is keeping you very busy! Those are great ideas we'll have to look into them in a season or two if my husband decides he's bored with the stock class.

Have any of you autoxers run on 14 inch wheels? A buddy has a set of 14 inch steel wheels he'd be happy to give us as a spare set and obviously rubber would be cheaper....

[ls six]

I've heard the supply of 14" performance rubber is drying up. With so much demand for 16" 17" and bigger tires the manufacturers have started to drop the smaller sizes. It should be cheaper though if you can find a tire you like.


Yeah it's keeping me pretty busy. I planned all kinds of projects over the winter but it was just to cold this year and it's still in pieces.

first things first I need to get it running reliably so I can sell my buick and buy another mazda.

[Pirate_d00d]

Ok I am rapidly gaining interest as well for autocrossing my 6. What size wheel and tire is too large? When does size cause a loss in handling/cornering performance?

[I4MX6]

Well 15 and 17 have a greater availability of tire choices for both sport tires and track tires. Although a lot of members here run FD's (16" rims), they are often run with too large a tire or tires that break most members budgets.

Personally, I would run 15's because of the available sizes. Something like a 225/50R15 for track would be my ideal choice for size and weight. But others prefer running 235/40R17 or 225/50R16 (too large compared to stock).

[ghostling]

Originally Posted by The_Evil_Demon

lol i should've had you install my k-sports then. Enough grease and oil and gunk to make anyone happy lol

u kidding right? it was so straight forward i can't imagine it being any simpler.
1. wheels off
2. undo bottom 2 large bolts, 1 small bolt.
3. undo top 3 bolts
4. take strut off
5. reverse steps with coil overs in place.
7. take it to the alignment shop.

[miatatude]

I haven't done mine yet, but I believe there will also be some drilling involved for the Koni adjustable knobs. Should be fun though.....

[defiler]

Yeeessss! Thank you! Is there an easy way to remove it? It's pretty stuck on there!

You can remove the DynaMat, but it sucks to do.

Personally, I would run 15's because of the available sizes. Something like a 225/50R15 for track would be my ideal choice for size and weight. But others prefer running 235/40R17 or 225/50R16 (too large compared to stock).

I'd run 15's because it's pretty cheap to find lightweight 15's, as compared to finding lightweight 17's or bigger... not to mention most of the time you can get a full set of good 15's for the price of 2 17's

[The_Evil_Demon]

Originally Posted by ghostling

u kidding right? it was so straight forward i can't imagine it being any simpler.
1. wheels off
2. undo bottom 2 large bolts, 1 small bolt.
3. undo top 3 bolts
4. take strut off
5. reverse steps with coil overs in place.
7. take it to the alignment shop.

keep in mind my car is a 95. so bolts were rusted to the point of welds. broke 1 socket wrench in the process. and had to buy a 4lb sledge to knock 1 of the bolts through on the rear lower connection of the strut. Nothing about the change was simple or easy. But i did get it done. lol

PS The rears had never been touched since it rolled off the assembly line

[miatatude]

Originally Posted by Pirate_d00d

Ok I am rapidly gaining interest as well for autocrossing my 6. What size wheel and tire is too large? When does size cause a loss in handling/cornering performance?

Are you new to autox? I have a 14 inch rim that I run on the miata, I used to run 16's and I feel like I get alot mroe feedback from the 14 inch, plus its /50/ so the larger width helps alot too!

For my budget, I have not found a better tire than the AVON t/a, my second fave would probably by the Kumho victoracer but I believe it requires shaving which adds to the expense. Keep in mind though, these applications are for a miata, not a '6, I'll have to let you know after the first event on the 20th about the "6!

[I4MX6]

^You do know that the middle number on the tire, such as the "50" you've indicated, represents the percentage of width that is in sidewall height, not the width itself right? The first number is the width and its measured in millimeters.

[miatatude]

Originally Posted by I4MX6

^You do know that the middle number on the tire, such as the "50" you've indicated, represents the percentage of width that is in sidewall height, not the width itself right? The first number is the width and its measured in millimeters.

Yes, of course I know that. You didn't realize that cornering in a low profile sidewall'ed tire is not good? The sidewalls are stiffer on a wider profile, which is best for autox.... thus will give the driver better feedback in the corners and less roll.

[gavin]

Originally Posted by Pirate_d00d

Ok I am rapidly gaining interest as well for autocrossing my 6. What size wheel and tire is too large? When does size cause a loss in handling/cornering performance?

It depends on the class that you plan to compete in as the answers are a bit different.

For a stock class you are only allowed to run wheels(aftermarket or not) that are the same dimensions as the stock item. Offset can be +-1/4"(@5-6mm) from stock. This is to allow aftermarket wheels that sometimes do not have the *exact* stock offset(sometimes the stock offset is just goofy).

With stock classes you have to use stock springs. The car will have a lot of motion because of this. Having the stock size tire will have a lot of weight transferred onto them and have them quickly overheat. Autocross is also about as much grip as one can afford. Because of these 2 factors, you will see aurocrossers stuff as much tire as can fit onto the stock dimension wheels. For the MX6 the stock wheel dimension is 15x6.5". The tire of choice for the car is a 225/45/15 R-compound tire. Its not unusual to see even more extreme tire combinations such as this (225/50/14 on 5" wide miata or civic wheels, 285/30/18 on RX8/nissan 350z 8" wide wheels). Yes, those fitments will have extreme camber to the sidewalls which will lead to sloppy handling. R-compound tires have very stiff sidewalls however and the "squirm" associated with these fitments can be minimized a bit.

Speaking of stiff sidewalls..your tire changing guys will not be none too pleased about doing this(some may even refuse). You might want to have a $20 bill to smooth things over after they do the work or they may come after you with tire irons.

In general the more tire the better, especially when it comes to heavier cars. There is a diminishing point of returns however where the tire is just too wide(or cant fit on the bead of the wheel). For example.while the RX8 and 350z can fit large rubber on the 8" wheels, the winning combo for the RX8 is actually a 245/40/18 tire. There have been tests with the 285/30 as well but it proves no faster(or a bit slower) and the extreme camber of the sidewalls dull the handling of the car. On the 350z however the added weight of the car makes the 285 a marginally better choice despite the steering feedback handicap.

In other classes that allow alternate wheel widths then the standard is to get the maximum wheel width that that class allows and then find the tire that will be mazes out on that wheel. For this you want the maximum tread width, the shortest aspect ratio and the most "square" sidewall shoulder to help with steering response.

Tire diameter is also another variable in both preparation classes. Its very common to use that to adjust the gearing of the car. Smaller diameter than stock will gibe a boost to available torque and lower the cars center of gravity without penalty to the suspension geometry. It will lower the cars terminal speed at a given RPM, but if the car as long leg (the KL is a revver), you can use that to gain back the loss of mph. If the cars gearing is such that you find yourself "between" gears you may have to do more shifting.

For my 1st gen GS car I used 225/50/15 and 225/45/15 r-compounds on 15x6" wheels. The shorter 225/45/15s (2" shorter than the stock 205/60/15 tires) were the faster tire even though I had to shift to 3rd to gain the speed back that I needed (2nd would top out at 53mph and I needed to target 60-62mph).

hope this helps

Gavin

[I4MX6]

Originally Posted by miatatude

Yes, of course I know that. You didn't realize that cornering in a low profile sidewall'ed tire is not good? The sidewalls are stiffer on a wider profile, which is best for autox.... thus will give the driver better feedback in the corners and less roll.

Yes, but you never specified width, you only implied that the value of "50" on your tires was the determinant for the width.

Some people like stiffer sides and others don't. I've played with slightly stretched tires and flat side tires, as well as various sidewall stiffnesses and have found that a sightly softer side allows for a better roll into a corner while keeping the tire planted and the car controlled. Too stiff a tire and it slides. But then again I don't race with r-comps...I race with soft street tires, so very different in the end.

[ls six]

Keep the good stuff comin I'm takin notes

[Pirate_d00d]

Originally Posted by miatatude

Are you new to autox? I have a 14 inch rim that I run on the miata, I used to run 16's and I feel like I get alot mroe feedback from the 14 inch, plus its /50/ so the larger width helps alot too!

For my budget, I have not found a better tire than the AVON t/a, my second fave would probably by the Kumho victoracer but I believe it requires shaving which adds to the expense. Keep in mind though, these applications are for a miata, not a '6, I'll have to let you know after the first event on the 20th about the "6!

Yeah I'm pretty much new to autox, I've never been to an event. I watched one of Piers' vids and got hooked, then transfered to this thread. I though autocross would be a good place for me to start. I've been wanting to get a new hobby, and autocross is becoming more and more appealing to me. I just have to work on maintenance issues and replacing parts that need to be replaced before I really push my 6. I have been wanting a new hobby for a LONG time

Gavin and I4MX6, thanks for the good info . As for what class I plan to compete in, more than likely not stock. I plan on doing some modifications and upgrades, so I won't be competing in stock class. This is all of course just looking into the future.