RX7Club.com - Mazda RX7 Forum

RX7Club.com - Mazda RX7 Forum (https://www.rx7club.com/)
-   Suspension/Wheels/Tires/Brakes (https://www.rx7club.com/suspension-wheels-tires-brakes-20/)
-   -   Maximum Wheel and Tire Width Fitment Guide for the FD (https://www.rx7club.com/suspension-wheels-tires-brakes-20/maximum-wheel-tire-width-fitment-guide-fd-892901/)

BLUE TII 02-10-15 05:36 PM

In 2014 I won the Atlantic Regional Time Attack Championship with my 93 FD stock drive train and 245/45/16 on 8.5 wheels.

This year our track is hosting the National Competition and I wouldn't mind owning that title as well. I have the home court advantage on a very technical 1.6 mile 11 turn short track with many elevation changes and a top speed of about 110 MPH.

I think going to a wider tire would help my chances significantly. The track is not the smoothest and I think a skinny 18 inch would do more harm than good. I have been toying with the idea of a 295/35/17.

The front and rear fenders are rolled and beat out with a BFH so that is not a concern. I am concerned with rubbing on control arms, and when turning, along with not altering the scrub radius so that it changes the turn in of the car more than my current wheels (16x8.5+40 F / 16x8+30 R. Does anyone have a track setup that they have tried. or could provide some insight; it would be appreciated.


I race 18x11 +45 on 295/30-18 Ventus TDs Front and Rear on my stock body FD.

That wheel width is the recommended "optimum" by Hankook looking at their new tire spec chart.

I have rolled/slightly pulled front fenders, rolled rear, Ohlins coilovers, Tripoint swaybar shortened 2" for full steering lock, -2.4deg Front, -1.2deg Rear camber.

If you are the type of driver that drives up the limits and then backs off a hair you will be WAAAAAAAAAAAy faster with this set-up.

If your fenders are as super rolled as you say, I personally would run 18x11.5 +38 with the 295/30-18 Ventus TD as I prefer these soft sidewall tires with a tiny bit of stretch (my 265 TDs on 10.5 wheel felt a little better).

I used Forgestar F14 and they are 22lbs in 18x11 +45 and ~ $1,500 as set.

lOOkatme 02-10-15 05:40 PM


Originally Posted by sip (Post 11868714)
In 2014 I won the Atlantic Regional Time Attack Championship with my 93 FD stock drive train and 245/45/16 on 8.5 wheels.

This year our track is hosting the National Competition and I wouldn't mind owning that title as well. I have the home court advantage on a very technical 1.6 mile 11 turn short track with many elevation changes and a top speed of about 110 MPH.

I think going to a wider tire would help my chances significantly. The track is not the smoothest and I think a skinny 18 inch would do more harm than good. I have been toying with the idea of a 295/35/17.

The front and rear fenders are rolled and beat out with a BFH so that is not a concern. I am concerned with rubbing on control arms, and when turning, along with not altering the scrub radius so that it changes the turn in of the car more than my current wheels (16x8.5+40 F / 16x8+30 R. Does anyone have a track setup that they have tried. or could provide some insight; it would be appreciated.

If you want max performance, my experience and research lends itself to run the widest wheel as possible that can fit and fit a tire to the wheel with a slight stretch (the tire beads are outside of the tread width of the tire.

if you can fit an 11" wide wheel, I would find a tire tread width around 10.5-10.9" wide. this will give you the trapezoidal shape that you want with the tire. when you think about turning, the tires sidewall is already stretched into position and holds the tread in place better than a tread width wider than the tire beads, which can lead to the tires sidewall flexing under load and possibly leading to unpredictable let go of the tire (it just let go).

find a race car that has tread widths wider than wheel widths in racing.

This is for performance, more comfort can be had with wider tires than wheel width as the sidewalls flex over bumps more. its not a huge difference but a difference.

stealthrt 02-10-15 05:46 PM


Originally Posted by lOOkatme (Post 11868794)
What tires are you running? make/model right now?

traction going forward is different than turning traction.


My philosophy when it comes to handling (turning) is to maximize grip and confidence/predictability. This lends itself to a smaller tire sidewall and slightly stretched sidewalls. this holds the tread in place when turning. the width gains traction as long as you can get it to temp.

straight line traction is about going to a taller tire on a small diameter wheel and lowering the PSI to elongate the contact patch in the forward direction. you run as wide as you can get to temp and gain traction. the more WHP, the wider the tire.

if you are just spinning tires, perhaps your tires aren't to temp? the tires are not a sticky tire, or your tires aren't wide enough and overheat.

its normal for cold tires on cold surfaces to have poor traction. this will be the case with any tire you choose.

I will have to look when I get home, but they are not top of the lines tires by any means. I am also putting down ~550 RWHP, which doesn't help traction whatsoever.

I am looking to maximize straight line traction while being able to maintain turning traction. Straight line traction is more important than turning traction for street use for me, and this car will only see a track on rare occasion.

Being a street car, it is rare that any tires I put on will get up to proper temps for great traction. So I guess I am looking more for the best cold traction I can find.

silverTRD 02-10-15 06:56 PM

So for a street car would it make sense to get max performance all season tires over max performance summer sires?

lOOkatme 02-10-15 09:04 PM


Originally Posted by silverTRD (Post 11868832)
So for a street car would it make sense to get max performance all season tires over max performance summer sires?

I don't have all the answers, but I drive my car only in the summer and like the soft grippy tires. this is probably why I don't spin my tires often and get really good grip.

You will always be faced with trade offs. the trade off being longevity vrs. performance (grip). I don't know of a tire that is going to last 50K miles and grip like a beast.

I will only run extreme sports tires on my 7, because I spent a lot on the car, and tires are what makes everything happen between the car and the road. Why would I spend tens of thousands on the car and skimp on the most important mod? that is just me.


If you really look around you can find deals on good tires. I purchased my Kumho XS 265/35/18 new for 600 shipped.

silverTRD 02-10-15 11:21 PM

I was more getting at if a all season performance tire will perform better If not driven at the limit? Because of the tires temp. Perhaps a better question would be will an all season tire perform better at a lower temp? I suppose it doesn't matter as I'm in So. cal lol but still an interesting question and it's nice I don't have to store my car for the winter. That must suck.

lOOkatme 02-11-15 08:04 AM


Originally Posted by silverTRD (Post 11868957)
I was more getting at if a all season performance tire will perform better If not driven at the limit? Because of the tires temp. Perhaps a better question would be will an all season tire perform better at a lower temp? I suppose it doesn't matter as I'm in So. cal lol but still an interesting question and it's nice I don't have to store my car for the winter. That must suck.

I would think the all season tires might be better in very cold temps, like 0-20 degrees, and perhaps more equal around 30, and the extreme tires are better in 40+ temps.

some of the extreme sports tires say on the tire not to operate in very cold temps as in 30 and below. When the extreme sport tires are in their operating range, the grip difference is gigantic between the two. It could be a .4G difference in grip which is miles apart.

I know the tests with a Toyo R1R on a miata without sway bars they were peaking at 1.3G, with the sway bars connected he peaked around 1.1G, and I would imagine a all season peaking around .85G or something.

silverTRD 02-11-15 08:27 AM

That is very helpful. Thank you.

ZDan 02-12-15 09:00 AM

The Max Performance Michelin Pilot SuperSport (Max Performance Summer) tires on my FD have less grip than the General GMax AS-03 on wife's Mazda3 in even 50F temps. Part of the issue is size. I'm on 275 rears on the FD, they don't really warm up in normal usage.

In normal conditions, the best UHP all-seasons are capable of within 0.05 g of the best Extreme performance tires. (Tire Rack's best average g's for Extreme Perf = 0.97 for ZII Star Spec, UHP all-season best = 0.93 for Pilot Sport A/S3

At 50F or cooler, on the street in normal usage, my money's on the best all-seasons for grip over the best Extreme perf tire.

nemix 02-12-15 04:51 PM

255/35/18 tire on a 18x9.5?

silverTRD 02-15-15 02:40 PM

Im looking into the Federal rsr's that BlueTII runs and they are at an attractive price. THe tread width is only 9.1" for a 255 however. Is that too much of a stretch for a 10" wide wheel? I also like the Dunlop star specs which are at 9.6" tread width but about 300 bucks more a set. decisions, decisions

BLUE TII 02-15-15 02:52 PM

Federal Tyres - UHP - 595RS-R

Right there-
Federal recommends the use of the 255/40-17 RS-R on an 8.5" to 10" wide wheel.

BLUE TII 02-15-15 02:55 PM

The Dunlops are a slightly more refined tire.

The 595RS-R are best bang for buck.

nemix 02-15-15 03:02 PM

Picked up some enkei nt03s 17x9.5 +44. Was thinking +40 for concave but couldn't pass up the deal on these. $800 used but literally brand new. No chips or scratches. Will post some pics after the install. Want to put a small spacer on the back but can't find any hubcentric ones available for the rx7 under 10mm

silverTRD 02-15-15 04:32 PM


Originally Posted by BLUE TII (Post 11871144)
Federal Tyres - UHP - 595RS-R

Right there-
Federal recommends the use of the 255/40-17 RS-R on an 8.5" to 10" wide wheel.

Yes I saw that thank you. I should have been more specific. Will it look hella stretched? I'm just being paranoid lol

BLUE TII 02-15-15 06:24 PM

No, it will look like proper tire and wheel fitment because it is.

ZDan 02-15-15 09:25 PM


Originally Posted by silverTRD (Post 11871189)
Yes I saw that thank you. I should have been more specific. Will it look hella stretched? I'm just being paranoid lol

Well, the section width of the 255/40-17 RSR is 10.2", only slightly wider than your wheel's 10" inside lip to inside lip width dimension. The outside to outside wheel width is 11", so you'll have 1/2" of wheel lip sticking out beyond the tire sidewall. That might look a bit "stretched", but whether it's too much or not is subjective. For sure there will be zero forgiveness if you run close to a curb, the tire will not protect the wheel.

Personally, for street usage I like for the tire to come closer to covering the total outside wheel width to protect the wheels. I'm running 275/35-18 on 18x9.5 wheels and to me it looks about right. I have to think that 255/40-17 on 17x10 would look a bit stretched, *to me*.

nemix 03-04-15 02:17 PM

2 Attachment(s)
Here are the 17x9.5 +44 with 255/40s. Running about a 26.25" height, want to drop the front down just a tad more, 1/2" or so in the front.

One problem I have is the fender line rubbing on full turns. I ordered new fender liners because mine were torn apart when I bought the car and they may be slightly sagging from not being fully mounted anymore. I'm hoping I can mount the new ones higher. If anyone has suggestions on avoiding fender line rubbing I'm all ears.

Attachment 554272

stealthrt 03-04-15 02:47 PM

3 Attachment(s)
I thought I would update.. Ray gramlights 57xtreme
18x9.5 +40 Fronts with 255/35/18
18x10.5 +40 Rears with 285/30/18

Fenders rolled, lowered on Tein HA's

Attachment 754147
Attachment 754148
Attachment 754149

nemix 03-04-15 04:07 PM


Originally Posted by stealthrt (Post 11879703)
I thought I would update.. Ray gramlights 57xtreme
18x9.5 +40 Fronts with 255/35/18
18x10.5 +40 Rears with 285/30/18

Fenders rolled, lowered on Tein HA's

Hey, look, someone else with 9.5s up front lol. With your size tire I think we'd be at the same diameter. Do you have fender liners? If so, are you running on those at all. Look good, wish I could have found 18s at a good price.

stealthrt 03-04-15 06:10 PM


Originally Posted by nemix (Post 11879731)
Hey, look, someone else with 9.5s up front lol. With your size tire I think we'd be at the same diameter. Do you have fender liners? If so, are you running on those at all. Look good, wish I could have found 18s at a good price.

Yea, we should be at nearly identical diameters. I got the rears for a great price, but just a decent price on the fronts.

The only fender liner I have is what covers about midpoint at the top to the rear of the wheel. Not the front liner. Mine were actually ripped to shreds when i bought the car so I just removed them.

GoodfellaFD3S 03-04-15 08:10 PM


Originally Posted by silverTRD (Post 11871189)
Yes I saw that thank you. I should have been more specific. Will it look hella stretched? I'm just being paranoid lol

It comes down to personal preference.

I know from experience I prefer a 255mm tire on a 9.5" front rim and a 265mm tire on a 10" rear rim.

So in my opinion a 255mm is too much of a stretch on a 10. Not a fan. However, my homie (and tuner) John Renna runs that size front and back (with staggered offsets) on his FD Blueberry Farms and he tracks with no safety issues etc.

We actually just spoke about it tonight and he said it's a bit too much stretch for him..... he did it because he had to. He runs +36 offset front and +20 rear and needed the stretch on stock rolled (heavily rolled out back he tells me) fenders.

stealthrt 03-05-15 07:29 AM


Originally Posted by GoodfellaFD3S (Post 11879837)
It comes down to personal preference.

I know from experience I prefer a 255mm tire on a 9.5" front rim and a 265mm tire on a 10" rear rim.

So in my opinion a 255mm is too much of a stretch on a 10. Not a fan. However, my homie (and tuner) John Renna runs that size front and back (with staggered offsets) on his FD Blueberry Farms and he tracks with no safety issues etc.

We actually just spoke about it tonight and he said it's a bit too much stretch for him..... he did it because he had to. He runs +36 offset front and +20 rear and needed the stretch on stock rolled (heavily rolled out back he tells me) fenders.

I run 255's on my 9.5's and I think they are stretched too much, and I wish I got some 265's although I may have had rubbing problems on +40's. They leave the wheel very exposed to curbs and other dangers.. not my style at all

lOOkatme 03-05-15 08:18 AM

widths vary greatly from tire manufacturer to tire manufacturer and from model of tire to model of tire.

One needs to look at the tread width and section widths of tires to gain a good understanding of just how wide the tire is.

for instance a 255/35/18 RE760 sport tire has a tread width of 9.3", yet a yoko AD08R tire has a tread width of 9.9".

.7" difference or 18mm difference.

1SikFDRx7 03-12-15 10:27 PM

18 x 9.5 f with +15 on a 235 35 tire and a rear 18 x 10.5 + 15 on a 245 35 tire with a fender roll fits perfect.


All times are GMT -5. The time now is 12:21 PM.


© 2024 MH Sub I, LLC dba Internet Brands