Handling/Ride: +Rubber/-Unsprung weight?

I'm already excited about the prospect of new alloys that will shave
seven pounds off the corners, or a pound or two less depending on the
plus sizing factor.

Now I'm seeking advice about diminishing marginal returns as regards
more rubber on the road versus further reducing unsprung weight.

My '05 Accord LX 4Cyl 5M came with Michelin's "CAFE" tires, good for
fuel economy but not much else, scoring in the bottom half of most
everything in Performance All-Season category. But they are already
fairly light for 205/65 HR15 92H tires, at 21 pounds each.

My challenge is to find the best weight to performace ratio for the
tire. Less unsprung weight means the suspension works better at what
it does, including keeping that tire on the pavement where it can do
some good.

Goodyear TripleTreds score very high marks for ride and noise comfort,
but do they score so well _because_ they're 5# heavier per tire? I
probably wouldn't pay that price if I could have a pretty good ride in
a less beefy tire.

It's easy enough to improve the wet and dry traction with better
compounds. Improving handling and steering response can be done by
brand selection, but sometimes it means reducing the aspect ratio.

One challenge I face is figuring out how much of (handling/ride) to buy
just by switching tire makers at the same size. Some tire makers score
dramatically better than others in Tire Rack's ratings, such that just
by switching makers, you gain improvements in both areas at the same
time. (But switching to the top rated Turanza tire in the same
category adds four pounds!)

Then again it's possible to make improvements in one area by trading
off against another. The examples below adjust unsprung weight changes
for plus sizing.

With example (2) below (Kumho ECSTA HP4 716s), I can get 8/10" more
rubber at the OE TIRE weight, while cutting the sidewall by 6/10".

Matching the stock tire exactly with option (1) would mean giving back
two pounds in exchange for across the board preformance by changing
brands.

With option (3) you drop one more NET pound, putting you eight pounds
lighter overall

22# Steelies + 21# OE Tire = 43# W+Tire

------------------->S+W/DIFF/Sect Width
1) 205/65 HR15 92H---38--5---8.1"
2) 215/55 HR16 91H---36--7---8.9"
3) 205/55 HR16 89H---35--8---8.4"
4) 205/60 HR16 91H---36--7---8.2"

(16x7 alloys are a pound heavier than 15x7)

If they all satisfied your +/- 3% speedo, and the speed rating was OK
and the load rating didn't matter, which would you pick for:

Steering response / Handling / Turn-in?
Ride comfort?
Throttle response / acceleration?
Fuel economy?

Seems to me that the 19#/8.4" section width might be the sweet spot --
but that depends on the diminishing returns theory of rubber on the
road vs unsprung weight! (The 65/60/55 differences are probably mild
enough to be inoffensive.)

Thanks for your thoughts on this.

-- CL.

+-----------------------------------------+
| Charles Lasitter | Mailing / Shipping |
| 401/728-1987 | 14 Cooke St |
| cl+at+ncdm+dot+com | Pawtucket RI 02860 |
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What for? Are you after good handling while going sideways through
corners on bumpy roads? Unsprung weight is important if you're racing
on bumpy tracks or rallying in the boondocks. Otherwise chasing after
every last pound is hardly worth it.

Anyhow, if minimum unsprung weight is a real necessity, go find some
magnesium wheels and never mind the tires.

 

In Providence, Rhode Island, it's the interstates at 70mph ...

Is that why Honda did backflips to reduce rotational mass everywhere
it could in the S2000?

I've read elsewhere that reductions in rotational mass play out as
more "apparent" horsepower. I don't pretend to know myself, that's
why I ask here, politely.

I understand that you should be ready to clean and polish them every
day, too.

I'd ask you again to FOCUS ON THE QUESTION: Diminishing returns in
unsprung weight, rotational mass, ride and handling.

The question is one of where and when additional investments in one
area don't generate payoffs that would be more easily attained
elsewhere.

-- CL.

+-----------------------------------------+
| Charles Lasitter | Mailing / Shipping |
| 401/728-1987 | 14 Cooke St |
| Pawtucket RI 02860 | cl+at+ncdm+dot+com |
+-----------------------------------------+

 

Unless you're cornering hard at that speed, unsprung weight won't
count for much.

Sure, but they can actually make really significant reductions. Not
just a pound or so, but real weight reduction that only a factory can
manage by careful design.

Yes, that's true, but again, you're not going to notice a pound less.

Yes, real mag wheels are a race track thing. They can't stand up to
road salt at all for instance.

You're way out on the tapering end of that diminishing return.

That's precisely where you're at.

 

I think that seven pounds per corner tire+wheel is REAL weight
reduction. Nine pounds would be even more real. My only real
question is whether that last two pounds might be better invested in
+1 wheels and more rubber on the road.

Not noticing a an additional pound at the margin tells me something.
Not noticing an extra two pounds at the margin tells me something.

I've observed up to five pounds difference in tires of the same size
spec. I don't think that's nothing. I think I might notice.

Thank you. This is what I suspected, and needed to know.

Again, thank you very much for your input.



--
-- CL.

+-----------------------------------------+
| Charles Lasitter | Mailing / Shipping |
| 401/728-1987 | 14 Cooke St |
| cl+at+ncdm+dot+com | Pawtucket RI 02860 |
+-----------------------------------------+

 

I am curios as to how YOU are going to notice any difference of even 7 lbs
per wheel in a god damned stock Honda Accord with a 4 cyl motor.

If you were geuinely concerned about performance then you wouldn't have
bought a family sedan. Go go a real sports car if that is what your
interested in.

 

Please explain how the number of cylinders matter.

 

This rotational mass / moment of inertial is not something I dreamed
up. It's a performance issue of which Honda itself is keenly aware:

http://tinyurl.com/4vjgp

"... Honda engineers wanted to keep the S2000 powertrain's entire
rotational mass to a minimum, thereby minimizing inertia, and the
response time between driver input and vehicle reaction."

http://tinyurl.com/4mzwo

"As an added benefit, putting lighter wheels on the car can increase
your engine's apparent power. Why? Well the engine has to turn the
gearbox and driveshafts, and at the end of that, the wheels and tyres.
Heavier wheels and tyres require more torque to get turning, which saps
engine power. Lighter wheels and tyres allow more of the engine's
torque to go into getting you going than spinning the wheels. That's
why sports cars have carbon fibre driveshafts and ultra light alloy
wheels.

I'm very pleased with my purchase. It's a fine car that can
comfortably seat adults, offering a sportier ride than a Toyota Camry,
and I plan to enhance the vehicle's strong points and enjoy owning it
for a very long time.

And so you are ... Honda's good will ambassador to first time Honda
buyers?

I put a lot of time and effort into composing questions as thoughtfully
as possible, and then posting them in forums where they are most
relevant, and the worst part of process is not the well intentioned
mis-information that is all to common on the internet.

It's jerks like you, who show their ass while offering nothing of
value, not even a meaningful critique of the questions posed that helps
bring relevant issues more clearly into focus.

-- CL.

+-----------------------------------------+
| Charles Lasitter | Mailing / Shipping |
| 401/728-1987 | 14 Cooke St |
| cl+at+ncdm+dot+com | Pawtucket RI 02860 |
+-----------------------------------------+

 

It's really about torque. Other things being equal, more cylinders
and more displacement = more torque.

http://tinyurl.com/4mzwo

"As an added benefit, putting lighter wheels on the car can increase
your engine's apparent power. Why? Well the engine has to turn the
gearbox and driveshafts, and at the end of that, the wheels and
tyres.

"Heavier wheels and tyres require more torque to get turning, which
saps engine power. Lighter wheels and tyres allow more of the
engine's torque to go into getting you going than spinning the
wheels. That's why sports cars have carbon fibre driveshafts and
ultra light alloy wheels."

I make no pretense of being any kind of expert, but I've recently
read a lot of information from people that consider themselves to be
experts, and I'm just looking for feedback from this group as to how
things might apply that I've read elsewhere.

-- CL.

+-----------------------------------------+
| Charles Lasitter | Mailing / Shipping |
| 401/728-1987 | 14 Cooke St |
| cl+at+ncdm+dot+com | Pawtucket RI 02860 |
+-----------------------------------------+

 

eh, youre doing good. i dont think many of us have really thought about
the weight of tire/wheel combos too much, pertaining to how much extra
power is given and the effects on speedometer readings, etc. you must
work in a technical field, right?

people with civics know if they want a light factory wheel/tire setup,
to get the wheels off an HX. theres no similar "economy" accord, unless
you count the hybrid... does that use the same wheels/tires?

 

Yup.
I just wanted to see if halo had anymore clever responses.

 

What I have found on the Tire Rack is 15x6.5" alloys that weigh in at
only 15 pounds for around $75, versus the current steel wheels. This
seems like a good idea if I do nothing else. And the Kumho tires have
also gotten favorable mention here in terms of being a good "bang for
the buck".

Thanks.

-- CL.

+-----------------------------------------+
| Charles Lasitter | Mailing / Shipping |
| 401/728-1987 | 14 Cooke St |
| cl+at+ncdm+dot+com | Pawtucket RI 02860 |
+-----------------------------------------+