Oversized tires on stock suspension = better grip and acceleration?

[m_kluch]

Lately been thinking about how to improve straight line grip/acceleration. Currently on 19” wheels with 245/35 tires and spoon springs. I have this idea of going back to stock springs and getting a set of 275/35r19 tires. I feel like there are a lot of upsides of doing this. The taller tires will fill the gap back up to how it is with the spoon springs so it’ll still look good. Also this will provide:
more ground clearance
better straight line grip due to wider tire as well as larger sidewall
More mph in each gear leading to possibly less shifting

I feel like the taller gear ratios will be a big benefit. Doing datalogs with my Racebox really shows how turbo lag on each shift slows us down. Here’s a log of my Type-R vs my brothers N/A Cadillac. You can see how much ground I lose each time I shift due to turbo lag compared to him. Also my 60-130 times are faster if I start in 4th gear even though third gear goes up to 85mph. This is due to the eliminated shift. Anyone go this route? What are your thoughts?

60-130 starting in 3rd vs 4th gear. 4th gear start is 1 second quicker!

me (blue line) vs my brothers 60-130. See how much ground I lose on shifts compared to him due to turbo spool. His N/A shifts barely affect him.

Another option I thought about is getting longer gearing by switching to the FL5 final drive but a tire change seems like a much easier and beneficial way to do it.
I understand that this is all about straight line performance and cornering will suffer a bit due to the taller ride height and softer springs.

 

[gtman]

Taller gearing will give you more top end but slower acceleration. A 275/35-19 tire will be quite heavy. Unsprung weight is the enemy of acceleration. You'll also need a 10" wide wheel IMO.

 

[Hondanickx]

Your alignment is what would help increase grip now.
275 tires and stock suspension gives you a boat .Keeps current tires and springs ,install a caster increasing kit with front bushings (Whiteline,others...)
And adjust your alignment.

 

[MadMage]

better straight line grip due to wider tire as well as larger sidewall

No, wrong assumption.

Wider tires have a larger contact patch, which means less weight per contact area (pressure) which means less traction per area.
If you look at the general traction/friction equation, Force=k(coefficient of friction)N(mass) it shows you that for a given coefficient, the only thing that matters is the mass/weight you put on that wheel.

The coefficient is mostly the tire compound but it does have some other factors, such as road surface and can be impacted by contact area. But it's minimal and probably not measurable. And as others have mentioned, the additional rotational mass is going to screw you over in measurable ways.

The reason you run wider tires on the track is more for heat management, wear, and for surface irregularities. (i.e. more predictable grip). The reason dragsters run wider tires is about managing wheel spin tire dynamics at time of launch and simple not to come apart due to force, and do almost nothing once traction is obtained.

 

[m_kluch]

No, wrong assumption.

Wider tires have a larger contact patch, which means less weight per contact area (pressure) which means less traction per area.
If you look at the general traction/friction equation, Force=k(coefficient of friction)N(mass) it shows you that for a given coefficient, the only thing that matters is the mass/weight you put on that wheel.

The coefficient is mostly the tire compound but it does have some other factors, such as road surface and can be impacted by contact area. But it's minimal and probably not measurable. And as others have mentioned, the additional rotational mass is going to screw you over in measurable ways.

The reason you run wider tires on the track is more for heat management, wear, and for surface irregularities. (i.e. more predictable grip). The reason dragsters run wider tires is about managing wheel spin tire dynamics at time of launch and simple not to come apart due to force, and do almost nothing once traction is obtained.

Thanks for that. I’ll have to do some research on that.

 

[m_kluch]

Taller gearing will give you more top end but slower acceleration. A 275/35-19 tire will be quite heavy. Unsprung weight is the enemy of acceleration. You'll also need a 10" wide wheel IMO.

My 60-130 runs show that slower acceleration is faster than having to shift one extra time so I’m fine with that. I think that for a turbo car with lots of mid range and top end power it’s more about staying in boost longer. But yeah a larger tire will add more mass so that’s a negative….

 

[MadMage]

Thanks for that. I’ll have to do some research on that.

Yea, I (and very few can) can't predict exactly what the end result of a wider tire may be. It's going to depend on your use case and a hundred other variables. If you can afford it, or willing to make a wrong choice and live with it, it's probably worth trying wider tires. I would just try to keep as many variables the same when you change the tire width.

 

[Dave B]

For drag racing, you want a longer contact patch, not a wider one. For those of us who turn corners, a wider patch is better. Ever notice how in top fuel drag cars, as they start off, the soft wide tire becomes taller leaving a much longer contact patch? Unfortunately with a front drive car, as the weight transfers to the rear on launch there is less weight to provide traction for the front tires. Not sure what the correct balance between weight, contact patch shape and size is for your situation and this is no doubt somewhat related to your total HP and torque.

 

[m_kluch]

It seems that a wider tire may not help after all but the taller sidewall and consequently taller gearing would. I have read a lot of testimonials about a taller sidewall helping greatly for a faster 60’. Also I’m trapping at the 1/4 mile right at the rev limit of 4th gear currently so it would be nice to get 5 more mph out of her in 4th.
However, this thread isn’t all about tire grip. I wanted to show some data to us Honda people about how much shifting slows this car down. I know many of us come from older N/A Hondas that needed to start at the lowest gear possible during a roll race. This is not the case for the FK8 and in fact can be detrimental as can be seen from my 60-130 runs. I’ve seen YouTube videos of FK8s roll racing and some of them downshift to the lowest gear possible even if they’re only going to be in it for one second. Old Honda thinking I guess.

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