• Sign Up! To view all forums and unlock additional cool features

    Welcome to the #1 Fiesta ST Forum and Fiesta ST community dedicated to Fiesta ST owners and enthusiasts. Register for an account, it's free and it's easy, so don't hesitate to join the Fiesta ST Forum today!


Tire and suspension data

Messages
107
Likes
65
Location
Carnegie, PA, USA
#1
Sharing my experiences and adding some data to the conversation. This year I went to a coil-over setup from Silvers. I wanted to be able to try out some tire options. I have 16” lightweight wheels for autocross (RFP1) so that was my hard point. I wanted to go as wide as I could, so I went with a 225/50-16 RE71r.

I chose this because it was ½ the price of the Yokohama and I like the Bridgestones. With -3 degrees camber up front and some adjustments to the coil-overs, I made them fit, but it looked like a monster truck. Under hard cornering, they actually rub at the back corner of the wheel arch opening. Right on the extra piece of plastic that is added for the ST, DOH!

C420DF8D-33FB-43D9-8BE6-FB6758843F31.jpeg
2A661E81-7714-447B-93B4-C3584CEA0A8F.jpeg
Look at the gap under the sills! That is as low as it will go on a 25" diameter tire. Transitional response was pretty poor and the ultimate grip wasn’t really improved. The sidewall was just too tall. They are on Craigslist now.

So I went to the other extreme, a 205/40-16 Falken RT660. Compared to the 215, the section width is the same so I went with the smaller width because it was less $. This is a 22.5" diameter tire, which allowed me to lower the car a lot. Turn in response is hugely improved, and the lower CG is helpful. Grip is great and the Falkens drive similar to the Bridgestones.

F475BDD9-EABF-45EF-8BB0-D32BA873D2D9.jpeg
F15390FC-A38A-4665-81D8-C5614BC33175.jpeg
So I think the lesson here is buy the 215/45-16 Yokos LOL. Or stay in HS and focus on driving not adjusting suspension!

That said, the car seems to be working great. With the increased torque and smaller wheels, 1st gear is almost useless. With the LSD and 2-point bar, it just rips out of corners. I took 1st in STH against some fully built WRXs on my first outing, hopefully I can repeat that again. I am as low as I can go without negatively affecting my roll center, and the fender gap is good with my 17" street tires. (Ill change wheel for the autocross, but not coil-over settings!)
 


Attachments

Last edited:
OP
pinchvalve
Messages
107
Likes
65
Location
Carnegie, PA, USA
Thread Starter #2
One question that comes up on the Falkens is wear on the center rib. You can see that the fronts show a little bit of wear on the center rib that the rears did not. I swap tires front and back for each event so it will even out, but it does seem to be a thing.

87AF6684-6D25-475B-93C9-A67E7FE800B0.jpeg AB6F4DD5-B90A-4C48-8A26-990F88683069.jpeg
 


M-Sport fan

9000 Post Club
Messages
14,000
Likes
6,697
Location
Princeton, N.J.
#3
Which Yoks were you referring to with the 215/45-16 size, as they not only don't make the A052 in that size, but none of their other 200 tread wear stickies either.[dunno]

On the other hand, IF one is willing to chance that center rib wear/separation, the RT 660s ARE made in that size, and with one of the very widest tread widths available for that size. [wink]

Yeah, I am expecting some rubbing with a 24" tall, 225/45-16 A052 (on Dekas), even on a factory ride height/suspension FiST, once I get them mounted and road force balanced. [:(]
So, yes, a 25" tall, 225/50 is way too tall, lowered or not.
 


Last edited:
Messages
314
Likes
267
Location
Portland, OR, USA
#5
After this weekends event, I am looking at tire options. The SSC guys are crushing it on the RT660s. Is the RT660 legal in all SCCA street class's? I wasnt sure if your running a non-scca club. Would the 225/50R16 fit on stock (Koni yellows, not coil overs) is what I am tempted to try out. I seem to always need a little more gear. I know general consensus is NO, but remember reading last week that someone did it and they fit.
 


M-Sport fan

9000 Post Club
Messages
14,000
Likes
6,697
Location
Princeton, N.J.
#6
The 225/45-16s are already a half inch or more taller than the factory/OEM size, so you already have 'more gear' with those over the 'usual', slightly shorter than factory, 205/45-16s everyone runs.

Yes, I know that size is not made in the 660s, but their 215/45-16 is also a bit taller than factory 205/40-17s as well, gaining some 'gear'.

I cannot imagine you not leaning over enough in sharp, autocross tight turns, even with the Konis cranked up to max, and an aftermarket swaybar, to not rub radically, and take CHUNKS out of a new set of 660s in a 25" TALL, 225/50-16 size.
 


Messages
314
Likes
267
Location
Portland, OR, USA
#7
The 225/45-16s are already a half inch or more taller than the factory/OEM size, so you already have 'more gear' with those over the 'usual', slightly shorter than factory, 205/45-16s everyone runs.

Yes, I know that size is not made in the 660s, but their 215/45-16 is also a bit taller than factory 205/40-17s as well, gaining some 'gear'.

I cannot imagine you not leaning over enough in sharp, autocross tight turns, even with the Konis cranked up to max, and an aftermarket swaybar, to not rub radically, and take CHUNKS out of a new set of 660s in a 25" TALL, 225/50-16 size.
I run 205/50R16, so am at 24.1" tall currently, you are correct, the 225/50R16 is 24.9" tall, so 0.4" closer to the fender.

Maybe the test comprimise is to run the 215/45R17 on my stock rims. Heavier setup, but could go back and forth between them and the RE-71s to compare feel... but then again they are still a 24.6" tire, so if that fits, what does 0.150" matter? ;-)
 


Messages
314
Likes
267
Location
Portland, OR, USA
#8
The 225/45-16s are already a half inch or more taller than the factory/OEM size, so you already have 'more gear' with those over the 'usual', slightly shorter than factory, 205/45-16s everyone runs.

Yes, I know that size is not made in the 660s, but their 215/45-16 is also a bit taller than factory 205/40-17s as well, gaining some 'gear'.

I cannot imagine you not leaning over enough in sharp, autocross tight turns, even with the Konis cranked up to max, and an aftermarket swaybar, to not rub radically, and take CHUNKS out of a new set of 660s in a 25" TALL, 225/50-16 size.
Measuring last night, the height combined with the width is definitely a concern. If it was just height, it would be tucked under far enough to likely not matter, but adding that extra ~1/2" outward would likely be a problem. I still may ask a local shop to bring in a set so I can test fit, after strapping the gopro onto the fender to try and get a sense of clearance during harder cornering.
 


M-Sport fan

9000 Post Club
Messages
14,000
Likes
6,697
Location
Princeton, N.J.
#9
My 24.2" tall 195/60-15 Artic Altimax 12s on a 15x7, 48ET wheel do not rub/scrape AT ALL, ANYWHERE.
Whereas my 24.0" tall 205/50-16 Neo Gens on the 40ET Dekas DO rub, so yeah, the width and offset matter more than the actual height (to a point). [wink]
 


kevinatfms

Senior Member
Messages
870
Likes
914
Location
Germantown
#10
You keep going to extremes on sidewall. Stick to a tire height of 23.0-23.7" height. I will attempt to run a 225/45R16 next year once i wear these Federal RS-Pro's out. Im hoping that they will just squeeze under the car without having to roll/BFH the liners. If Konig would make a flow formed wheel in 15x8 4x108 +35 they would sell like hotcakes. Id be in for at least 2 sets and run 225/45R15s on them.

205/50R15(my 15" wheel set runs these in RS-RR Feds. 8" tread width measured on a 7" wheel - they run wide) - They are right at 23" tall which leads to beating the rev limiter on a few sections of track. Not ideal but still fast.
225/45R15(this is the widest tire that works for us but we need 15"x8" wide wheels to maximize the tire tread width) - SOMEONE please make a 15x8 wheel in 4x108 +35 offset with a proper backspacing to allow for brake room.

205/45R16(my current tire - 7.8" tread width and 23.3" height) - About perfect if not stretched a little much on an 8" wheel. Id like an 8" tread width on an 8" wheel from my past experiences with the car.
215/45R16(mid ground tire but the Federal RS-Pro's are actually wider in a 205...) - I wish they were wider in this size but both the BFG Rival and RT660 come in UNDER a 205 Federal that i currently run which is embarrassing.
225/45R16(this is pushing it but would work sick on some Dekagrams - my next step up) - 8"+ tread width and right under 24" height. These might be the hot ticket to keep the gear ratio close to stock(a bit longer) and get as much rubber on the road with the current selection of OTS wheels(Konig's seem to be easy to get).

205/40R17(OG tire size)
215/40R17(works well on 17x8 wheels)
 


CSM

1000 Post Club
Messages
1,529
Likes
1,621
Location
Cleveland, OH, USA
#11
@kevinatfms I'll give you my experience running 16x8 dekagrams +40 w/ 225/45/16 ZIII tires - I have a few events on that setup now with Bilstein coilovers maxed out on ride height (about a 20mm drop all around if memory serves correct).

The setup is grippy as crap but rubs the fenders in the front pretty bad. I've rubbed the paint off the inside fender lip - its not noticeable but something to take into consideration. I think you are going to rub no matter what on lowered suspension unless you are running a lot of camber and/or roll fenders on 16x8 w/ 225/45/16

Fiesta is going to take a back seat to my Scion for the rest of the year for autocross - going to install LSD, clutch, flywheel, dial in more camber (2.5* hopefully), roll fenders switch to a coilover w/ a more modest drop, and see if that fixes the issue for next season. Will look to compete in XSA in Fiesta and SSC for Scion.

I too am considering 15x8 setup for next season - starting to keep an eye out for used TD 1.2s.

BTW, I have the RT660s on my Scion and THEY ARE AMAZING. I am consistently placing in the top 15% PAX Times with that car. Just a joy to drive.
 


M-Sport fan

9000 Post Club
Messages
14,000
Likes
6,697
Location
Princeton, N.J.
#12
Yeah I was going to bring up the impossibility of running the 225/45-16s (especially the A052s, which are the tallest and widest in tread width of the whole lot!) on anything lower than factory ride height, and possibly not even then.

WHY I am reluctant to even mount mine up onto the Dekas before I get some kind of upgraded, but factory ride height capable, or higher suspension under the car!
 


CSM

1000 Post Club
Messages
1,529
Likes
1,621
Location
Cleveland, OH, USA
#13
Yeah I was going to bring up the impossibility of running the 225/45-16s (especially the A052s, which are the tallest and widest in tread width of the whole lot!) on anything lower than factory ride height, and possibly not even then.

WHY I am reluctant to even mount mine up onto the Dekas before I get some kind of upgraded, but factory ride height capable, or higher suspension under the car!
I am going to try the KW V3, which report a .2" drop all around as being the most minimal setting, with more camber. Lets see if that works!
 


kevinatfms

Senior Member
Messages
870
Likes
914
Location
Germantown
#14
@kevinatfms I'll give you my experience running 16x8 dekagrams +40 w/ 225/45/16 ZIII tires - I have a few events on that setup now with Bilstein coilovers maxed out on ride height (about a 20mm drop all around if memory serves correct).

The setup is grippy as crap but rubs the fenders in the front pretty bad. I've rubbed the paint off the inside fender lip - its not noticeable but something to take into consideration. I think you are going to rub no matter what on lowered suspension unless you are running a lot of camber and/or roll fenders on 16x8 w/ 225/45/16

I too am considering 15x8 setup for next season - starting to keep an eye out for used TD 1.2s.

BTW, I have the RT660s on my Scion and THEY ARE AMAZING. I am consistently placing in the top 15% PAX Times with that car. Just a joy to drive.
That is unfortuneate to hear. Then ill stick with 205's and 215's on the 16" wheels until i plop the money down for some Braid 15x8 Ultralites. The 205 Federals is the widest 205/215 that i have found in 16" sizes.

So it looks like the only tire to run on our car without rubbing/hacking in a 225 is in a 15" size. 225/45R15 is 23" or so in diameter and most tires are well over 8" tread width. So its about the perfect size. Pair that with an 8" wide wheel.

Stupid that TD wheels are hard to get at this point. We need more options. Cant imagine why Konig cant do a run of 15x8's that they already make and just swap the bolt pattern(from 4x100 to 4x108). Even the 73.1 hub bore is fine with me. Just want that 15x8 +35.
 


CSM

1000 Post Club
Messages
1,529
Likes
1,621
Location
Cleveland, OH, USA
#15
Stupid that TD wheels are hard to get at this point. We need more options. Cant imagine why Konig cant do a run of 15x8's that they already make and just swap the bolt pattern(from 4x100 to 4x108). Even the 73.1 hub bore is fine with me. Just want that 15x8 +35.
I reached out to Konig and asked about what minimum qty commitment they would need. They produced the Dekagram and Dial-In for the miata crowd in 15x8 and 4x100 pattern, wondering if it would be relatively easy for a production run of 4x108
 


kevinatfms

Senior Member
Messages
870
Likes
914
Location
Germantown
#16
I reached out to Konig and asked about what minimum qty commitment they would need. They produced the Dekagram and Dial-In for the miata crowd in 15x8 and 4x100 pattern, wondering if it would be relatively easy for a production run of 4x108
There are a ton of Miata wheels right in that 15x8 +30-35 range. Im just surprised manufacturers arent seeing a market.

I feel like between B-spec racing and the Fiesta ST track crowd they have been selling enough for Konig to make them in 4x108 so why cant others follow suit.

Crossing my fingers someone comes through.
 


CSM

1000 Post Club
Messages
1,529
Likes
1,621
Location
Cleveland, OH, USA
#18
Talked w/ a Konig Rep about this - if there is enough interest, they will do it. But it has to be a specific run (e.g., diameter, width, offset, BP, design).

I may start a new thread to see how much interest in this forum community there is for a 15x8 offering from Konig. Would be roughly $600 for a set and 12 lb a wheel
 


kevinatfms

Senior Member
Messages
870
Likes
914
Location
Germantown
#19
Talked w/ a Konig Rep about this - if there is enough interest, they will do it. But it has to be a specific run (e.g., diameter, width, offset, BP, design).

I may start a new thread to see how much interest in this forum community there is for a 15x8 offering from Konig. Would be roughly $600 for a set and 12 lb a wheel
Count me in for (2) sets at 15x8 +35 4x108. Color doesnt matter to me as long as they are lightweight. They already have the Dekagrams in that size and offset, should be able to just swap the hub bore/bolt pattern mold.
 


Similar threads



Top