15" wheels vs 16" vs 17" Wheel for hpde/autocross/daily, which and why?

[Brick]

So eventually i'm going to switch from the stock wheel and tire combo to something else.

Currently i'm considering a 15x8 wheel (team dynamics I think is my only option other than 4x100 set up(sorry RAAMaudio ) because of:
1)cost
2) rubber is ridiculously cheap for this wheel size, and there are TON of choices for 205/50/15, and I can buy the best tires for dirt cheap. My previous vehicle, a set of 4 tires would be roughly 1100 bucks everytime because of how wide they were. 265 in front 305 in back. I get excited at the idea of REALLY nice rubber for 550 bucks or less.

Should I even consider 16x8? (I guess it would allow me to run HS in national autocross events if I stay stock, which I doubt I will do in the long run of the car.)


I currently doubt I will pony up 800-1000 dollars for a big brake kit as I find the stock brakes adequate for daily driving and hopefully up to snuff with some race pads for the occasional track day. Is that the only benefit to 16 or 17inch wheel.

I just cant think of a reason NOT to go to a 15 inch wheel and tire set up.


What's my car used for? Daily driving, spirited runs, occasional track and local autocross (in the long run I wont care about what class I am in as I see myself getting an intercooler and other things eventually.)

 

[Kip2MyLou]

Subbed for responses.

Personally I have 15x6.5 with 195/55s and love them. I'm only going up to 16s next year because I want a wider set up. I'm going 16x7 with 205/45 or 205/50s. I will never track this car so it's strictly daily driving for mine.

 

[Waterfan]

16" HS wheels would need to be 7" wide like stock I think, not 8

 

[kobushi]

I'm curious to see what people think about this article:

http://www.thetruthaboutcars.com/2015/07/barks-bites-fist-rollover-risk-people-dont-want-know/

that stickier tires on smaller rims make the st a rollover risk.

 

[RAAMaudio]

Depending on the class, mods, etc..........could be worse, could be better, can be perfectly fine.

Done wrong, more risk, done right, less risk....lower the CG, widen the track, do not lower the car to much which causes the roll center to change in a bad way putting all the weight on the outside tires, no worries.

I have jumped curbs on track hundreds of times and felt like I had 3 or more wheels off the ground a few times, purposely over driving the car on some sessions, it never came close to rolling over. I do have a very wide stance for a FiST though but want to make it wider if a real body kit every comes out, going from 15x9 to 15x11" wide wheels and 255 or 275 slicks.

 

[meFiSTo]

I'm curious to see what people think about this article:

http://www.thetruthaboutcars.com/2015/07/barks-bites-fist-rollover-risk-people-dont-want-know/

that stickier tires on smaller rims make the st a rollover risk.

The Fiesta ST is a tall, narrow car. The CoG is not exactly Porche-like. Putting sticky tires on smaller diameter tires with a stock suspension probably contributes to making it more prone to rollover, especially if those tires are not fully inflated (common at the start of an HPDE for example -- allows for air expansion when heated). An auto-cross application is probably a little more of a likely rollover situation than a normal HPDE/lapping situation (setting aside sudden emergency maneuvers) due to there often being more severe, and sudden changes of direction in auto-cross. Big course scenarios do have chicanes and such, but still the G-forces are probably not as severe (normally) compared to auto-cross.

Having said all that, I do have a BC coilover setup on my car that is slightly lower than stock and set significantly stiffer. I have a little bit of negative camber up front and have added a 4-point lower brace. I think that all reduces the tendency to roll over. I'm probably most susceptible to rollover at the start of a track day because I under-inflate my tires and warm them up during the first few laps, resulting in them building air pressure for the first 4 or 5 laps. I don't auto-cross.

Back to the original question:

I like the 15x7 wheels for the incredible options in 205/50-15.

I have one set of 15x7 TD PR 1.2s with RE11As (summer street/drive to track/wet track tires) and another set of the same wheels with Nitto NT01s (paddock bolt-ons). I have less than 3000 miles on my car. I received it May 2014.

However, if you're really nervous about the rollover deal, 17x7s with 205/40-17s will probably reduce that risk (or at least any risk associated with your tire/wheel combination).

 

[RAAMaudio]

Much better post than mine

BC "race spring setup reduces roll a great deal, I think I might want stiffer springs yet as it rides very nice on the race ones, far better than stock.

Better to reduce roll with springs and lower CG, move weight down low and to the rear adds to a better F/R balance, sway bars are the last item in setting up a car properly suspension wise.

Lower your seating position as low as you can still see well.

The stock chassis is very stiff, I do not believe it needs anything more than a 2 point front cross member brace but using more will add weight down low helping the CG but weight also slows you down in every other aspect.

Get rid of unneeded parts like the engine cover, every little bit helps and more so on a relatively low weight car as it is a bigger percentage.

Lower the side windows when you can.

 

[Brick]

I'm curious to see what people think about this article:

http://www.thetruthaboutcars.com/2015/07/barks-bites-fist-rollover-risk-people-dont-want-know/

that stickier tires on smaller rims make the st a rollover risk.

That was an interesting read, and so were the comments.


With that said, we have a lot of members on this forum who track and autocross their ride.... How many of them feel legitimately at risk of a roll over?

I've done an autocross in stock form and never felt at risk. I feel like autocross has much more aggressive steering inputs than track days... But with that said... I don't want to worry about going on two wheels versus spinning out. Kind of makes me wonder now to be honest.

15x8 with +35 offset and tires with a stiff sidewall should do the trick.

 

[Pete]

I personally run 16x7 all around currently. But that was because I went with the Wilwood big brake kit. I do love the braking performance but before I pulled the trigger I was debating on getting 15x7 for the car to reduce the wheel weight. At the time there were no stock front brake pads available for the Fiesta so my option was wait a month or go with the big brake kit. I would say if you do decide on the 15" rim to also invest in brake ducts as there will be less air moving around the rotor since the rim size will be 2 sizes smaller.

 

[RAAMaudio]

15x8 +35, 205 or 215 wide tire properly inflated, fast and fun and should be perfectly fine

I have a stock front sway bar with stiffer bushings and have a bit of body roll but not bad at all and really hardly notice it even when bouncing off the curbs can catching some air under a tire or two, maybe three or four.... I am on 15x9 +35 with a 2mm spacer with the race tires and 5mm with the Rival S as they have curb protectors on both sides(a bit odd on a directional tire)

 

[Phreak]

With that said, we have a lot of members on this forum who track and autocross their ride.... How many of them feel legitimately at risk of a roll over?

You could definitely roll the Fiesta, I've even been able to put mine on two wheels at one point

That said, anybody with any kind of driving experience knows to turn into it and get it back down onto 4 wheels and it therefore represents a near zero risk.

The real problem is with people who are inexperienced. You stick a 16 year old kid in a Fiesta with stickey tires who has been driving for just a few months, and there is certainly a risk of them putting the car on it's side.

At the end of the day, you can roll any car if you try hard enough

 

[scotman]

You could definitely roll the Fiesta, I've even been able to put mine on two wheels at one point

That said, anybody with any kind of driving experience knows to turn into it and get it back down onto 4 wheels and it therefore represents a near zero risk.

The real problem is with people who are inexperienced. You stick a 16 year old kid in a Fiesta with stickey tires who has been driving for just a few months, and there is certainly a risk of them putting the car on it's side.

At the end of the day, you can roll any car if you try hard enough

If a fiesta is lowered and has proper tires I really cant see a situation where it could be rolled in an autocross situation. On course, i spun mine hard and never felt like it might tip over. I spun it on asphalt and concrete. I never felt in peril.This decision by scca surprised me. They would have been smarter to just require that stability controls remain active to participate in HS. The fiesta is VERY much pinned down by its electronic nannies.

 

[Phreak]

^^ If you run wheels with a lower offset, (6mm wider) on the fiesta, I believe it actually meets the rollover requirement

I typically turn off the nannies as much as possible on dry weather conditions with my ST... most of the time if I spin, it just goes around. Only one spin out of an entire summer had me up on two wheels, and it was easy to pull out of it without risking a rollover.

This is a video that I showed one of my spins in right off the bat:

[video=youtube;YKt7jkHrGbE]https://www.youtube.com/watch?v=YKt7jkHrGbE[/video]

 

[mouse]

^^ If you run wheels with a lower offset, (6mm wider) on the fiesta, I believe it actually meets the rollover requirement

I typically turn off the nannies as much as possible on dry weather conditions with my ST... most of the time if I spin, it just goes around. Only one spin out of an entire summer had me up on two wheels, and it was easy to pull out of it without risking a rollover.

This is a video that I showed one of my spins in right off the bat:

[video=youtube;YKt7jkHrGbE]https://www.youtube.com/watch?v=YKt7jkHrGbE[/video]

On that spin you were going off course anyways(in the wrong direction of the directional cones)

If you look closely at the video in the truthaboutcars link, you can tell that right before he goes into that right hander, he goes through a part of the parking lot where the elevation dips and comes up again as he begins that quick left(which is in the middle of a dip) and right. That elevation could have easily caused this hoopla and I would argue the course design was the culprit....If I was a lawyer, but I'm not.

 

[RAAMaudio]

Just remember there is likely more room to pull out of a two wheel situation on an autocross course than on public roads or a road course if you are near or in traffic.

 

[SPDinNY]

so what size RE71R would you guys recommend for my Fiesta for autocross? I have 16X7" wheels on it and I am installing a set of BR Coilovers soon, will not be in HS probably in SPF??

 

[LT Berzerker]

Never had a problem with mine, that said, I'm running about 22.7mm further outboard then stock on a 17x8 on Cobb springs

I've lost control in a tight slalom and nearly spun the car with zero issue. Simple inexperience and had it shift weight back and forth to the point of sliding sideways.

Even at the road America go kart course (autox) never had an issue running curb... You'll be surpised by the level of grip and turn in you get out of the car.

Additionally, with bc's you could possibly get away with a 225 tires up front and you'll be able to get 215 out back before you get rubbing issues, that's very dependent on the tire tread/sectional width and height you have the car at.

If your worried keep the nannies on for a couple runs and then test the balance of the car with them off.

 

[SPDinNY]

maybe I will just go with 215s square for rotation and less chance of rubbing

 

[RAAMaudio]

Make sure to research the tires carefully if you want the best autocross tires it might be the Rival S as it was made for autocrossing.

DO NOT GO BY 205, 215, 225.... Please look at the real specks as those numbers can be very far off thus quite misleading and using some online calculator will not give you correct info either.

Most of the good tires are on listed on Tirerack with actual weight, sectional width, tread width, diameter and weight.

The testing they do is very helpful but not like an actual road race track, autocross, more a blend of them but still very good information to help us decide what to get.

For the Rival S you would want to run the 215/45/16 which is pretty close in specs to the tire below and a little heavier.

For the RE71R you would use the 205/45/16 as it is the only size that would work out decently.

I would have to research what the top autocross drivers are using on a similar car to make a final decision but you would be happy with either one, for now, RE71R seems the best.

 

[mercdank]

205-45-16 RE71R on my Sparcos working great for me. Definite upgrade over stock, it's absurd.