Going from 8.0" to 8.5" wide wheels- tires?

So, I've been looking for a way to pick up a bit more speed in my DC2 Integra GS-R. I'm running the car in autoX, in a local league where the classes are based on PWR. The class I'm in dictates that max tire width is 225 and treadwear is limited to 200tw. For reference, I'm in a lower power class, making around ~160whp. That power figure is actually corrected for altitude, so I'm making a good bit less (we're at ~5000 feet elevation, read: the car doesn't make enough power for acceleration traction to be an issue). 

I'm currently running a square setup: 15x8 +35 wheels and 205/50/15 RE71RS tires. This setup cleared the rear trailing arm by a few mm and required only a very minor roll in the rear (there was only a very slight rub in the rear right side- I didn't even have to roll the fenders flat). 

At the time I bought this setup, on an 8" wheel, the answer seemed obvious: the A052 and RE71RS both come in a 205/50/15, but neither of them came in a 225/45/15 (essentially same sized sidewall). On an 8" wheel, I've seen enough tests from Andy Hollis to know that 205's and 225's are essentially equals, so I went with the 205's. 

Fast forward and I'm rethinking my setup for next season. I'm thinking about switching up my wheels to a 15x8.5 +25 and running a set of 225/50/15's. I'm not thrilled about the idea of increased sidewall height/giving up gearing, but am wondering if the additional 0.5" wheel width would help give a 225 wide tire an actual advantage? 

As far as gearing goes, I have a CTR transmission, so at redline (8000rpm) in 2nd gear, with the 205's, the car should hit ~59mph. If I stepped it up to the taller sidewalled 225/50 tires, that would bump 2nd up to ~61mph, which might not be the worst thing on earth. 

I think I can get the 8.5's to fit with a flat fender roll and I don't think I'll need to pull them. I've considered going straight to a 9" wheel, which I'm sure will fit up front, but if I wanted to run them in the rear, I would either have to run a ~10mm spacer (based on wheel options) and pull the fenders a good bit, or I would need to notch the rear trailing arm (which I would like to avoid if possible). Hence my thoughts about running an 8.5" wheel. 

Assuming my driving is consistent, should I see a noticeable difference in times going from a 205/50 on an 8" wheel, to a 225/50 on an 8.5" wheel? Will the additional lateral grip make up for the increased sidewall height (slightly taller gearing)? 

Personally, I'd run the 225's on a 9" in the front and 205's on the 8" in the rear.

ross2004 said:

Personally, I'd run the 225's on a 9" in the front and 205's on the 8" in the rear.

I have considered it. My only real issue is that the car is very balanced right now, so I was worried about the car being too tail-happy running a staggered setup. Maybe my concerns are unfounded? 

I'd think notching the rear trailing arms to run 15x9s all-around would be worth it, it should be at least as quick as the staggered setup without the PITA factor. Can the arms be reinforced by adding metal elsewhere? On those 225/45R15s or 245/40R15s would work well.

If you do go ahead with the staggered setup it should only slightly shift the handling balance toward oversteer.

GameboyRMH said:

I'd think notching the rear trailing arms to run 15x9s all-around would be worth it, it should be at least as quick as the staggered setup without the PITA factor. Can the arms be reinforced by adding metal elsewhere? On those 225/45R15s or 245/40R15s would work well.

If you do go ahead with the staggered setup it should only slightly shift the handling balance toward oversteer.

Yes, they do make reinforcement plates that can be welded in. Unfortunately, I have no welding skills or equipment to speak of, so it becomes a pay-someone-else situation. Not the end of the world, but it ups the PITA factor. 

https://honeddevelopments.com/product/trailing-arm-gusset-plate-honda/

15x8, 8.5, or 9 with all the rubber you can run upfront. 

15x7 205/50R15 rears. DO NOT modify the trailing arms 

The front 1/3 of the car matters, the middle 1/3 is where you sit, the rear 1/3 is a trailer that the rules force you to tow through the course. Spring the car as such (most Honda set ups have WAY too much rear spring in an attempt to get them to drive like a RWD car)  keep the tires on the ground, focus on finding speed doing what the car is good at. 

A properly set up FWD car is going to struggle to get heat in the rear tires, often a staggered setup will reduce snap/surprise oversteer while making the car as a whole more neutral. 

Byrneon27 said:

15x8, 8.5, or 9 with all the rubber you can run upfront. 

15x7 205/50R15 rears. DO NOT modify the trailing arms 

The front 1/3 of the car matters, the middle 1/3 is where you sit, the rear 1/3 is a trailer that the rules force you to tow through the course. Spring the car as such (most Honda set ups have WAY too much rear spring in an attempt to get them to drive like a RWD car)  keep the tires on the ground, focus on finding speed doing what the car is good at. 

 

A properly set up FWD car is going to struggle to get heat in the rear tires, often a staggered setup will reduce snap/surprise oversteer while making the car as a whole more neutral. 

Thank you for the info! 

If I'm being honest, I think bad previous experiences with my old CRX have left me wary to wander too far into tail-happy FWD car land. On that car, I was actually running square RT660's, and if they were cold, the car corner-entry oversteered quickly and was hard to catch. Admittedly, I was also running a large splined rear sway bar (ASR, 32mm IIRC) and in hindsight, I think the poly RTA bushings were binding as well (I learned my lesson and will only use rubber or spherical RTA bushings going forward- currently running Hardrace hardened rubber), which didn't help. I also think my spring rates were just a bit too high (13k/9k) for the tracks I was running on. If I had to set that car up again, for my local tracks (which are a bit bumpy), I would likely dial it down to 11k/7k (same rates that Andy Hollis runs on this One Lap CRX). 

I didn't consider a staggered setup reducing snap oversteer based on tire temps, but I suppose that stands to reason. 

On a 15x9 setup up front, any idea if I'll need to do any pulling of the fenders? My current 15x8 setup needed nothing at all. 

I have 15x8s on the front of my GSR that's probably as wide as I'd go. My fenders are pulled already from its previous life as a stance-mobile and they're close. 

CRX handling is a little how might you say unique because the track width is within 30" of the wheelbase and they want to rotate around the center of the car. Overly stiff or binding trailing arm bushings add a ton of wheel rate in a very unpredictable fashion. I used to use Mugen when they were easy to get ahold of I now use Whiteline. Cant say I see much of a reason for bearings back there. 

Start by keeping the tires on the ground and checking tire temps that will suggest what you should do. 

My GSR is setup as follows and it a pretty quick hoot.

Koni SPSS 500F/400R springs

Poly bushings including steering rack. Whiteline Trailing arm bushings

Smallest EG front bar

24mm Chinese rear bar

Full compliment of subframe braces and tower bars

SPG camber adjusters

-2.5 camber 0 toe front

-2.0 camber 1/16" toe in rear

Staggered rt660s 225/45R15 front on an 8" wheel 205/50R15 on a 7" wheel rear 

Isn't the CRX going to be a lot more edgier at the limit vs the integra due to the shorter wheelbase? 

I think doing the 15x9 up front and 15x8 would be worth doing. Didn't Hollis run 15x9 on  the A052 on the CRX? 

My integra has the Spoon rear trailing arm bushing, which seems to be harden rubber and looks different from the Mugen/OEM one with less voids. Cost was fairly affordable as well. 

Option 1: buy two of the 8.5's and put your current front 205's on them.  You will likely be quicker. You'll know if you are getting more front grip if the car balance changes. 

option 2: buy 9's for the front and mount 225's.  The extra OD may cause issues with upper inner fender clearance and will also change your rake (less)

Don't be afraid of more front grip.  Easy to fix the balance. 

15x9s up front of you can..

I was running the exact same setup as you with my DC2. 15x8s with 205- 71RS all around.

Just recently switched to 15x9s up front(still 15x8s rear). With 225 RC1s on all 4. Might try and run 205s in the future for the rear, but the 225s were actually cheaper at the time.

Slower tires, but I picked up close to half a second with no other changes. And a longer lasting tire, with contingency for NASA.

I'm already wanting to space my fenders and try and get a 17x10 or 17x9.5 up front, but more front grip on these cars is addicting, makes all the difference.

aw614 said:

Isn't the CRX going to be a lot more edgier at the limit vs the integra due to the shorter wheelbase? 

I think doing the 15x9 up front and 15x8 would be worth doing. Didn't Hollis run 15x9 on  the A052 on the CRX? 

 

My integra has the Spoon rear trailing arm bushing, which seems to be harden rubber and looks different from the Mugen/OEM one with less voids. Cost was fairly affordable as well. 

Yeah, I think the CRX wheelbase is about ~11 inches shorter than the Integra's. I suppose that car just left an impression on me and I ended up selling it before everything was dialed in. 

I'm running Hardrace rubber in pretty much all locations on my Integra and have yet to experience a problem. It's very balanced and easy to drive as it sits. 

Andy Hollis said:

Option 1: buy two of the 8.5's and put your current front 205's on them.  You will likely be quicker. You'll know if you are getting more front grip if the car balance changes. 

option 2: buy 9's for the front and mount 225's.  The extra OD may cause issues with upper inner fender clearance and will also change your rake (less)

Don't be afraid of more front grip.  Easy to fix the balance. 

 

Thank you Andy! I think I've been swayed and am now looking at 15x9 options for the front. What offset would you recommend on a DC2? 

Blackhalo said:

15x9s up front of you can..

 

I was running the exact same setup as you with my DC2. 15x8s with 205- 71RS all around.

Just recently switched to 15x9s up front(still 15x8s rear). With 225 RC1s on all 4. Might try and run 205s in the future for the rear, but the 225s were actually cheaper at the time.

Slower tires, but I picked up close to half a second with no other changes. And a longer lasting tire, with contingency for NASA.

 

I'm already wanting to space my fenders and try and get a 17x10 or 17x9.5 up front, but more front grip on these cars is addicting, makes all the difference.

Oh wow, that's impressive! I'm sold. I've been scouring the web looking for 15x9 fitment up front. Any offset recommendations would be appreciated! 

If you picked up 17x10 or 17x9.5 wheels, do you know what size tires you would run? I'm not sure how much your car weighs, but would they be legal for your weight, presumably in NASA TT5? 

In reply to roninsoldier83 :

15x9 +35 Konigs. Mild roll, not sure how much it was needed, my car isn't very low.

Yeah, TT5. I'll have to read the rules and see if I can run wider. I get the modifier right now staying at 225 and under.

But it'd be worth the hit if I could run 255s up front. I'll have all winter to figure out that though, a long with starting to mod this 128 for TT5 too.

In reply to Blackhalo :

Did the 15x9 +35's need any sort of spacer? Trying to gauge how much room in between a 9" wheel and the knuckle. 

In reply to roninsoldier83 :

Nope. Not running a spacer or anything.

In reply to Blackhalo :

Beautiful DC2! Well built, sir! 

In reply to Blackhalo :

My DC2 isn't nearly as "racecar", but it's slowly getting there: 

https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/the-teg-a-dc2-road-to-all-the-hondas-story/258401/page1/

^^^after all these years on this forum, I finally started a build thread. 

In reply to roninsoldier83 :

Thanks man.

It's definitely not racecar yet, still have ac and full interior. Yours is clean!  K20a2 and aero along with the normal junk.

In reply to Blackhalo :

That's a clean, OEM+ looking wing! That car is beautiful! What wing is that? And is it adjustable? 

I think I'm going to run TT6 this next year in the DC2 and when I eventually get it sorted, a K-swap is likely in it's future. Like you, I would like to try and keep as much of the interior as possible, as well as A/C. 

Byrneon27 said:

The front 1/3 of the car matters, the middle 1/3 is where you sit, the rear 1/3 is a trailer that the rules force you to tow through the course. 

Quoted for truth.

In reply to roninsoldier83 :

Thanks man! 

That was the look I was going for. Yeah it's a nine lives element and custom stands a local racer made. 

Nine lives has a similar looking wing on their site now that a Gridlife GLTC guy is running. But the stands are kinda ugly. But he could cut you out some stands if you're ever interested.

TT6 with the B18C1 would be perfect. You won't be disappointed when you go K swap though.

I'm hoping to get out to High Plains next year, is that your local track? Looks amazing.

roninsoldier83 said:

In reply to Blackhalo :

My DC2 isn't nearly as "racecar", but it's slowly getting there: 

https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/the-teg-a-dc2-road-to-all-the-hondas-story/258401/page1/

^^^after all these years on this forum, I finally started a build thread. 

Looks like I'll need to view it on mobile, seems like images are blocked on my work PC. 

My Integra is currently dead, I dropped a valve...build thread is over on the ITR Expo forums.

Blackhalo said:

In reply to roninsoldier83 :

Thanks man! 

That was the look I was going for. Yeah it's a nine lives element and custom stands a local racer made. 

Nine lives has a similar looking wing on their site now that a Gridlife GLTC guy is running. But the stands are kinda ugly. But he could cut you out some stands if you're ever interested.

TT6 with the B18C1 would be perfect. You won't be disappointed when you go K swap though.

I'm hoping to get out to High Plains next year, is that your local track? Looks amazing.

Depending on where my PWR ends up, I might actually be interested! 

I've been looking for an excuse to go K24 for a while now... but I've made the B18C1 pretty interesting to drive, so I'd like to dial the car in and enjoy it before I swap it. 

Yes sir, High Plains Raceway is my local track! If you manage to make it out here, shoot me a line and I'll try to make it out to check out your DC2!