Enlightening read on wheel offset and effects on suspension and steering

[RacingManiac]

only thing I care about offset wise is if they meet the +/- 7mm rules for SCCA Street class, which unfortunately really limits my options....

The Mita wheels mentioned here was interesting but I've never heard of them. Looks like gonna be priced similarly as the forged Apex option which was hinted they might have something in the range. Otherwise my only options looks to be the flow formed BMW spec Apex....

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[keller]

They still start with a factory civic body in white and use the dual axis strut setup and all factory mounting points.

The CTR TCR car doesn't have the dual axis strut design. It's a standard MacPherson strut.

 

[dng]

only thing I care about offset wise is if they meet the +/- 7mm rules for SCCA Street class, which unfortunately really limits my options....

The Mita wheels mentioned here was interesting but I've never heard of them. Looks like gonna be priced similarly as the forged Apex option which was hinted they might have something in the range. Otherwise my only options looks to be the flow formed BMW spec Apex....

hi RacingManiac, what are your thoughts about the flow formed BMW spec Apex? anything concern you besides the need for the centering rings?

 

[RacingManiac]

Apex is pretty well known, Camaro, BMW, etc runs them pretty often and they are pretty light so no issue functionally. I ran wheels with centering rings before for autoX so I've had no issue with that also. I just don't particularly like the style thats available to us here, and since they are BMW wheels they don't work with the factory center cap. I might still get a set though as street use wheels but I'd prefer something different looking....

 

[tezzasaurusrex]

Great thread, interesting to see everyone's take on this.

I'll throw in my 2c. There are valid points on either side of the coin, however I will come up with my conclusion at the end.

Firstly, I agree the comparison to TCR may not be the best one to make. As they do indeed run a completely different suspension set up, which is a traditional Macpherson instead of the OEM dual axis as @keller correctly pointed out. This would change everything in terms of the proposed scrub radius. Not assuming that scrub radius is the reason for the change, as it could be due to a whole other host of reasons relating to ease of track-side set up changes, increased set up window such as camber/caster angle and/or bump steer, running particular axle type etc etc. Additionally, a road car is trying to achieve different things to a race car. Overall comfort, NVH, steering feel and feedback, torque steer, etc can be sacrificed for outright speed on a race car – ultimately speed is what a race car is looking for, and this may not be what the greater public necessarily wants in a road car if its at the sacrifice of other aspects as listed above.

Secondly, I think most of the available aftermarket wheels on the market are not ultilizing the space available within the wheel well. The most common sizes are the 18x9.5 ET38~ET45 at the moment. This leaves a significant amount of room behind the wheel (between the rearmost side of the wheel and the strut/body). The more optimum sizing is 18x10.5-11 ET50~ET55. This would enable safe running of 295's on the stock guards (plenty of camber needed of course - somewhere in the vicinity of -3.5° to -4°) and also optimize the scrub radius aspect. 18x10.5 ET50 w/ 315 wide RT660 have been confirmed to work.

Ultimately, if speed/lap times is what you’re trying to achieve, then you may find sacrificing optimum steering geometry is necessary to achieve required camber angle and/or tyre sizing. As ultimate grip is generated through running the widest rubber possible with balanced and sufficient support from the wheel’s width, the ride frequency and damping rates, and from the chassis itself. There are some mods that people don’t think about that affect scrub radius such as running offset front ball joints (Hardrace, Whiteline etc all the same), which is changing scrub radius by up to 10mm on the most negative setting (since you have effectively moved the wheel centreline away from the steering axis) however, as the resultant camber and speed gain trumps the small sacrifice in steering geometry – it is a sacrifice many are willing to make. Most don’t even know they’ve made this sacrifice. There are many world stage level time attack vehicles running 30-50mm wide spacers simply to be able to maximize tyre width under wide guards – if you look at their resultant scrub radius and steering geometries you can clearly see where their priorities lie.

Personally, I like to strike a balance for my car since it’s a road car that also goes on track. So, while achieving fast laps is indeed important to me, I’d like to achieve it with respect to the OEM design to avoid putting the vehicle into a set up that’s too far away from Honda’s intention. I’m sure many of us have done this at one point in our lives which was to go too hard on the mods, changing the vehicle dynamics entirely to the point where it almost resembles nothing like the original car, and what ends up happening is we fall out of love with it cause it no longer feels like the original car which we initially enjoyed driving.
Thus, my modifications always take both sides into consideration. A better way to achieve camber is to use camber adjustable strut tops vs running the offset ball joints due to the effects on scrub radius using the latter method as mentioned earlier.

What’s my final take? It all comes down to you as the individual and what you want to achieve with your vehicle. Likely, we are not Max Verstappen and most of us won’t feel a 10-15mm difference in scrub radius let’s be honest, but say you are in that small population that do, then you can apply the above principles to effect. It would be erroneous to state that low offset wheels are a performance reducing mod, based on the fact that a car's overall performance cannot be judged on it's scrub radius numbers alone.

Apologies for the long post.

 

[dandaman15]

The CTR TCR car doesn't have the dual axis strut design. It's a standard MacPherson strut.

Got it. The way it was outlined here I thought it was based on the TC car and the only changes were the dampers listed in the far right column. I couldn't find a picture online to confirm until finding some obscure YouTube video of them working on it just now.

https://hpd.honda.com/Articles/Touring/TypeR

 

[keller]

Got it. The way it was outlined here I thought it was based on the TC car and the only changes were the dampers listed in the far right column. I couldn't find a picture online to confirm until finding some obscure YouTube video of them working on it just now.

https://hpd.honda.com/Articles/Touring/TypeR

Thanks for this drawing. This knuckle design is just crazy. I took a few pics of these cars last month:

https://www.civicx.com/forum/threads/fk8-and-fl5-tcr.85629/

 

[hammeredsole]

Great thread, interesting to see everyone's take on this.

I'll throw in my 2c. There are valid points on either side of the coin, however I will come up with my conclusion at the end.

Firstly, I agree the comparison to TCR may not be the best one to make. As they do indeed run a completely different suspension set up, which is a traditional Macpherson instead of the OEM dual axis as @keller correctly pointed out. This would change everything in terms of the proposed scrub radius. Not assuming that scrub radius is the reason for the change, as it could be due to a whole other host of reasons relating to ease of track-side set up changes, increased set up window such as camber/caster angle and/or bump steer, running particular axle type etc etc. Additionally, a road car is trying to achieve different things to a race car. Overall comfort, NVH, steering feel and feedback, torque steer, etc can be sacrificed for outright speed on a race car – ultimately speed is what a race car is looking for, and this may not be what the greater public necessarily wants in a road car if its at the sacrifice of other aspects as listed above.

Secondly, I think most of the available aftermarket wheels on the market are not ultilizing the space available within the wheel well. The most common sizes are the 18x9.5 ET38~ET45 at the moment. This leaves a significant amount of room behind the wheel (between the rearmost side of the wheel and the strut/body). The more optimum sizing is 18x10.5-11 ET50~ET55. This would enable safe running of 295's on the stock guards (plenty of camber needed of course - somewhere in the vicinity of -3.5° to -4°) and also optimize the scrub radius aspect. 18x10.5 ET50 w/ 315 wide RT660 have been confirmed to work.

Ultimately, if speed/lap times is what you’re trying to achieve, then you may find sacrificing optimum steering geometry is necessary to achieve required camber angle and/or tyre sizing. As ultimate grip is generated through running the widest rubber possible with balanced and sufficient support from the wheel’s width, the ride frequency and damping rates, and from the chassis itself. There are some mods that people don’t think about that affect scrub radius such as running offset front ball joints (Hardrace, Whiteline etc all the same), which is changing scrub radius by up to 5mm on the most negative setting (since you have effectively moved the wheel centreline away from the steering axis) however, as the resultant camber and speed gain trumps the small sacrifice in steering geometry – it is a sacrifice many are willing to make. Most don’t even know they’ve made this sacrifice. There are many world stage level time attack vehicles running 30-50mm wide spacers simply to be able to maximize tyre width under wide guards – if you look at their resultant scrub radius and steering geometries you can clearly see where their priorities lie.

Personally, I like to strike a balance for my car since it’s a road car that also goes on track. So, while achieving fast laps is indeed important to me, I’d like to achieve it with respect to the OEM design to avoid putting the vehicle into a set up that’s too far away from Honda’s intention. I’m sure many of us have done this at one point in our lives which was to go too hard on the mods, changing the vehicle dynamics entirely to the point where it almost resembles nothing like the original car, and what ends up happening is we fall out of love with it cause it no longer feels like the original car which we initially enjoyed driving.
Thus, my modifications always take both sides into consideration. A better way to achieve camber is to use camber adjustable strut tops vs running the offset ball joints due to the effects on scrub radius using the latter method as mentioned earlier.

What’s my final take? It all comes down to you as the individual and what you want to achieve with your vehicle. Likely, we are not Max Verstappen and most of us won’t feel a 10-15mm difference in scrub radius let’s be honest, but say you are in that small population that do, then you can apply the above principles to effect. It would be erroneous to state that low offset wheels are a performance reducing mod, based on the fact that a car's overall performance cannot be judged on it's scrub radius numbers alone.

Apologies for the long post.

I think that pretty much settles it, and I agree, my statement about performance reduction is erroneous. It might change driver interaction in a way which could be viewed as negative, but it won't actually hurt the performance by the numbers.

 

[1971Camaro]

Great thread, interesting to see everyone's take on this.
[ ... ]
What’s my final take? It all comes down to you as the individual and what you want to achieve with your vehicle. Likely, we are not Max Verstappen and most of us won’t feel a 10-15mm difference in scrub radius let’s be honest, but say you are in that small population that do, then you can apply the above principles to effect. It would be erroneous to state that low offset wheels are a performance reducing mod, based on the fact that a car's overall performance cannot be judged on it's scrub radius numbers alone.

Here's my dilemma....
I had gotten some good input here before re camber and options, along with any of the car internal system settings to compensate, and I did some more research. I had never bought wheels before and hadn't realized that the axle size was not standardized. Yet, most importantly, as you and everyone here have said, we cannot know the feel from just the numbers...and i don't want to make a $5k mistake. So, after fretting about it for weeks now, i ended up doing what many on this forum have done when faced with this level of investment choice: Nothing.

But, I use my FL5 as a "daily driver" and will need winter tires. Given I live in an area where potholes and heavy snowfall is common, I want to go with 18" wheels to get the extra tire sidewall. For my specific needs, this would be strictly for functionality -- not track, and not cosmetic. I love the feel and responsiveness of the factory wheels and tires, and I just want to maintain that as closely as possible. From having already driven in it, I concur with others that this car does amazingly well on sleet and slush even with factory PS4s, but I've had my share of pothole obstacle courses with a couple of "hits," plus, I will need to drive the car in heavy snows, so I want peace-of-mind.

We've already had measurable snowfall a couple of weeks ago, and i have to get my head out of the sand. Has anyone found an 18" setup that you feel handled reasonably similar to factory?

Thank you.

 

[tezzasaurusrex]

Here's my dilemma....
I had gotten some good input here before re camber and options, along with any of the car internal system settings to compensate, and I did some more research. I had never bought wheels before and hadn't realized that the axle size was not standardized. Yet, most importantly, as you and everyone here have said, we cannot know the feel from just the numbers...and i don't want to make a $5k mistake. So, after fretting about it for weeks now, i ended up doing what many on this forum have done when faced with this level of investment choice: Nothing.

But, I use my FL5 as a "daily driver" and will need winter tires. Given I live in an area where potholes and heavy snowfall is common, I want to go with 18" wheels to get the extra tire sidewall. For my specific needs, this would be strictly for functionality -- not track, and not cosmetic. I love the feel and responsiveness of the factory wheels and tires, and I just want to maintain that as closely as possible. From having already driven in it, I concur with others that this car does amazingly well on sleet and slush even with factory PS4s, but I've had my share of pothole obstacle courses with a couple of "hits," plus, I will need to drive the car in heavy snows, so I want peace-of-mind.

We've already had measurable snowfall a couple of weeks ago, and i have to get my head out of the sand. Has anyone found an 18" setup that you feel handled reasonably similar to factory?

Thank you.

Its a game of compromises.
You will always lose some degree of steering response when you go from a 30 to a 35 aspect ratio as there is an added moment and flex in the sidewall upon each steering input. There's no two ways about this. What you can do however is select a tyre that has a structurally stiffer sidewall, such as the Yokohama AD09, vs say a Pilot Sport 4 which is on the softer end. This will help to retain that level of steering response you're accustomed to on the OEM DT1 PS4S. What you gain in response however, you'll typically lose in comfort and vice versa.
I'm on 35 aspect ratio RE71RS and I agree that the immediacy of the steering has dulled down a touch from the 19" OEM wheels. But what I lose in steering response I have gained in unsprung mass (3kg saving per corner), ride compliance (I can bomb ripple strips on the 18's whereas the 19's would likely buckle the rim), and the far greater tyre choice is an easy win for the 18's for my style of usage.
You just have to decide for yourself what you're willing to give up.

 

[CTR]

I'm on 35 aspect ratio RE71RS and I agree that the immediacy of the steering has dulled down a touch from the 19" OEM wheels. But what I lose in steering response I have gained in unsprung mass (3kg saving per corner), ride compliance (I can bomb ripple strips on the 18's whereas the 19's would likely buckle the rim), and the far greater tyre choice is an easy win for the 18's for my style of usage.

I think this was my biggest mistake when downsizing to 18" wheels in the +45 offset. I should have used 200TW tires instead. If I would have went with more aggressive tires the effect would probably have been lessened. I guess that's still an option even if I don't really want to risk the dismount and remount on nearly new nice wheels...

 

[1971Camaro]

Its a game of compromises.
You will always lose some degree of steering response when you go from a 30 to a 35 aspect ratio as there is an added moment and flex in the sidewall upon each steering input. There's no two ways about this. What you can do however is select a tyre that has a structurally stiffer sidewall, such as the Yokohama AD09, vs say a Pilot Sport 4 which is on the softer end. This will help to retain that level of steering response you're accustomed to on the OEM DT1 PS4S. What you gain in response however, you'll typically lose in comfort and vice versa.
I'm on 35 aspect ratio RE71RS and I agree that the immediacy of the steering has dulled down a touch from the 19" OEM wheels. But what I lose in steering response I have gained in unsprung mass (3kg saving per corner), ride compliance (I can bomb ripple strips on the 18's whereas the 19's would likely buckle the rim), and the far greater tyre choice is an easy win for the 18's for my style of usage.
You just have to decide for yourself what you're willing to give up.

Fantastic! That helps a ton. I don't care about having a softer ride, but i do care about response. So, this helps me make an informed decision.

Love this forum!

 

[TypeRD]

@1971Camaro Snow tires use a MUUUUCH softer compound than summer tires. Even with the best possible setup, the softness and mushiness of snow tires is not going to match the OEM (summer) setup. It is what it is. Winter traction and maneuverability is an entirely different ballgame than summer traction and maneuverability. I know you know this. I just don’t want you to chase something that isn’t safely possible, i.e. summer style driving in the snow in Chicago.

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