What were your findings on the Yokohama A048's for track use?

Anybody else know?

Thanks,

KT

It's almost tire time again.
I have a pair of these in size 225 with two hours on them...I'll buy a pair of 205's for the front to go along.
Or I can get more 710's. 205 with 225's this time.


KT

You'd think after 7 hours I'd more than just 90 looks without a single peep...This is new.

Not even a passing mock


KT

what are you doing to fight the added rear grip (leads to understeer no?)

bigger rear springs?
Less Sway bar stiff?

I'm not sure about that yokohama tire, but I would highly suggest Toyo Proxes RA1s for track use.

I agree with Aaron on this Trekkor.

either go with 225s at all 4 corners or 205s

with 205s up front and 225s in the rear you will induce some understeer you have not had up until now. You will need to soften up your front bar and or soften the Konis, if you havent already.


I would try to go 225s all the way around.

I ran my 914-6 with 205s all around for a year and then tried the 205/225 deal. found that I go too much push on the track so I went back to 205s all around and liked the balance of the car much better. Never tried 225s all around because I only had 2, 7" Fuchs at the time.
If I had it to do over I would opt for the 225s all around on 7s.
My poor input to your dilema.
since you already have 2 Yokos get two more...what the heck...how bad can they be?

OK.

This helps. I was talking to someone yesterday and they suggested the same ( all 225's )

I guess I don't quite get it.

Why will it push? Nathan thought it would oversteer. That I could handle.

I set the Koni's on full soft while on track...Full firm at the a/x.

Will 225's rub in the front fender wells?
Will it be harder to steer with bigger fronts?


KT

the theory is this.

With a larger rear contact patch. ...the rear will stay more planted than it does currently...this will cause the front to push more. this assumes you run 205s front and 225s rear.
If you go 225s all around you maintain the same balance you currently have and your suspension settings should work.
With the 205/225 set up you will need to soften the front end or stiffen the rear end.
If your shocks are already set at full soft, your only choice will be to soften the front bar...since you run a huge bar with stock torsion bars, softening the bar will give you less front roll resistance...more weight transfer side to side.
I am probably not explaining this very well....but that is the general idea.


This is why the factory put 205s on the front of Carreras with 245 or larger on the rear. Helped induce understeer to counteract the tendency of taildraggers to oversteer.

Still holds true on stock Boxsters and 911s. Much larger rears than fronts to quell the dreaded oversteer.
When I tracked my Boxster I ran 225s and 245s to help cut down on the understeer. (stock is 205/255)

Thanks.

My front bar is currently set at 2/3rd's toward full firm.
I do have a lot of room to back off.

Will I need to mod the front to accept the bigger skins?


KT

As long as your fenders are already rolled you shouldn't have any problems...
Others may chime in here...

Possibly at full lock?

good basic stuff

My front fenders are stock, only the rears are pulled.


KT

QUOTE (trekkor @ Apr 4 2006, 09:23 PM)

Or I can get more 710's. 205 with 225's this time.

For the love of god, Kumho 710s are NOT track tires. Neither are falken azines. Theres a reason they're half the price of the real tires (RA1s, yokoyomamas, hoosiers, etc.).

trekkster....

my car had 205's on 7" cookies for a while. very nimble and neutral...

now for the street i went to 7"/205 and 8" 225.... with same sway bar settings AND 225 lb springs... still pushes. i need to back off on the tarett bar... (and wish i could tighten up a stock rear bar)

and my situation is even worse... i also have 22mm t bars now...

so... like dan said, more rear contact, means the rear has to FIGHT harder to break loose.... thus making it "push".....

maybe try 205's on a 7" with a spacer? and tune from there? same grip just more track???

QUOTE

Kumho 710s are NOT track tires.

Why would you say that?



KT

trekkor..i run 225s x 50 on the front with only a little scrubbing with the steering wheel all the around to lock, bothers me none.. they fit nice they are on 16x7s fuchs

QUOTE

Theres a reason they're half the price of the real tires

Not true, sir.

Shaved RA1's are less than 710's.

710's are about $30 less than Hoosier's or Yok's.

Brad told me they are not track tires, too.
I don't agree on our light cars. They don't break loose or get greasy during a 30 minute session.
When I drive them to the limit, we'll see.


KT

not here to argue on tires where i have no experience....

anyway. re: 225's up front...

i balked on doing that with the tires i had. they have stepped sidewalls thuse UBER large contact patch.... i test fitted it to the front... on a cookie or a 7" fuch it would rub at anything over -1.5 deg camber.... and hits on full lock. i chose NOT to roll the front fenders.....

AA

QUOTE (trekkor @ Apr 4 2006, 10:28 PM)

QUOTE Kumho 710s are NOT track tires. Why would you say that? KT

I've heard that from 3 sources. I dont know much, but I know who to listen to.

I have mounted a set for our BSR car, and the sidewalls flex like truck tires.

QUOTE (trekkor @ Apr 4 2006, 10:34 PM)

Brad told me they are not track tires, too. I don't agree on our light cars. They don't break loose or get greasy during a 30 minute session. When I drive them to the limit, we'll see. KT

I dont know your background, but Brad knows way more then me. I'd be inclined to listen to someone that's been through that much.

I didnt know he doesnt like 710s. That makes 4 independent sources whose knowledge I hold very valuable that dont like the tire.

But who knows, they could all be wrong

On heavy big powered cars these may be a/x only tires.

On a 914 I'm hearing and experiencing nothing but good in dry conditions.

I have 14 hours of track time on this set. Still above the wear bars.

They are rated to run between 210-240 degrees, which I have come nowhere near.

If someone has had bad experiences with these on a 914, I will listen.

QUOTE

sidewalls flex like truck tires.

Not on a 205/50/15. No way. What are you talking about?

KT

watchu talkin bout matt?

QUOTE

special brake duct

My calipers stay under 300 degrees, so I think congratulations are in order.


Like I said, if you have tracked a 914 with 710's, I'm listening.


KT

QUOTE (trekkor @ Apr 4 2006, 10:54 PM)

QUOTE (MattR) sidewalls flex like truck tires. Not on a 205/50/15. No way. What are you talking about? KT

The 710s have way more sidewall flex then an RA1, yok, or hoosier of the same size. Ask the guy who mounts your tires... I've done a few sets, and I can say for certain they are really weak sidewalls. Thats the only first hand experience I have with 710s. Everything else is from other people who have raced them.

Again, this is track only. For the street, 710s can be fine.

QUOTE

sidewall flex

Where?


KT

edited

QUOTE (trekkor @ Apr 4 2006, 11:06 PM)

QUOTE sidewall flex Where? KT

sidewall flex isnt really a visual thing...

This is my last post on this thread. I suggest RA1s. If you think I'm wrong, cool... more RA1s for me.

rh, lh. What's the difference?

That's a fast exit at Laguna, down hill.

Here's a hard right hand at an a/x at about 45-50 mph.
Right inside front lifting.

KT

Crap... And I was just starting to enjoy the thread......



Twystd1

Turn 11 at Sears.

I like the tires, OK?


KT

I agree with Matt, if not just to get another cool picture of your car.



Looks great! Looks like it's driving fine too! DO you have any bad driving pictures?


M

Bout the only thing I can tell you is that 225's are fine once you start rolling just a tad.

In parking while the vehicle is stopped, you might find it slightly difficult to move the wheel.

That being said, I'll be running 255's up front, and im not worried.

Andrew

QUOTE (trekkor @ Apr 4 2006, 11:01 PM)

Thanks. My front bar is currently set at 2/3rd's toward full firm. I do have a lot of room to back off. Will I need to mod the front to accept the bigger skins? KT

Everthing Dan has told you is right on. But the fact that your front bar is set at 2/3 firm says your leaning toward oversteer now. If you up the size of your front tires you may run out of front sway bar. I changing my front torsion bars from 22mm to 23mm because I have the same scenario as you: after moving up to 225's on front my bar is 3/4 firm and I'm still fighting oversteer so I'm moving up the torsion bars to get a more neutral position on the sway bar.

Trekkor,

You can fit 225's up front if you have the right wheel without rolling the fender. I can fit 'em in there on an 8" rim with 5" backspace. Rears are pulled out, but the front fenders are stock.

Matt,

Are you sure you're talkin' about the 710's and not the Ecsta 700's or the Ecsta MX's? Now -those- (the MX) have super soft 'n squishy sidewalls. I've not driven the new Kumho 710's but I'd be surprised if they are as bad as you describe.

-Josh2

My wheels are 7" wide with 5" backspace.
I like the balance of the car now very much. More grip would be nice.


I don't want to buy a pair of the 048's just to find out that the 710's I have in 205 size are grippier.


KT

I have been very surprised at how little my 914 plows with 225 in front and 265 in rear. Granted I have been driving mountain roads, hardly comparison to AX or track. It maybe because of the soft bar I'm running up front. Maybe its the 1 inch spacers I'm using to widen the front track? I know I'm wide in the front because my tires rub slightly on my flares in slow turns.

I too like Dan had a Boxster and ran 225 in front and 255 in the rear. Understeer was more of a component of my driving style with that car. If I drove poorly the car would plow, If I did everything right it had great turn in and I could invoke oversteer. Just increase entry speed a little and lift slightly as you approach the apex then back on power. Car rotated fine for me. Did the same with the 914 when it wasnt turning. Guess driving FWD cars in AX has helped me.

I guess its always better to have a little oversteer, but its not the end of the world to have a car that mildly understeers.

No one talks much about the advantage of being able to ge on full power more quickly when the car does turn with larger rear tires.

I guess sidewall flex must be good for AX . More national championships were won on 710's last year than any other R-compound (including hoosier).

The only problem I would see with them on the track vs. an AX is heat from being worked on the track for a lot more than 1 min at a time. It could be a lot more of a problem on a heavier car but Trek seems to be doing well with them on a 914.

QUOTE

sidewall flex

So, If I were to try 225's in the rear and the car started to understeer ( push ). I would add rear spring or loosen front bar. Is that right?

I'd like to have a second set of 7" rims, mount the Yoks 205/225 and compare the handling/times at the track on the same day.


KT

QUOTE (trekkor @ Apr 5 2006, 02:46 PM)

So, If I were to try 225's in the rear and the car started to understeer ( push ). I would add rear spring or loosen front bar. Is that right? I'd like to have a second set of 7" rims, mount the Yoks 205/225 and compare the handling/times at the track on the same day. KT

Yes

I find this discussion about 710s to be very interesting.

I know of at least of couple of folks that have them on 914-4s on the track and have had no issues...they all rave about the grip and the good wear.
I wonder why?

Maybe as Trekkor is saying, we are talking about 914s that are extremely light when compared even to a Miata.

Not saying anyone is wrong on this topic. Maybe we are talking apples and oranges? _
It might get to be a different story at TH or BW in July with ambient temps in the 110s+.
I guess the answer is if they don't work some folks will speak up with direct knowledge and then none of us will consider them for track tires again.

I think the 710's got a bad rap when they first appeared on the market. The "cap" on the tire would seperate, and the tire would chunk if the tire wasnt broken in well.

Broken in means not so much heat cycling.. but tread depth in this case. The 710s come shaved now ( i think) and seem to work well..though Im not sure how they survive heavy cars like a 996 or 993..

FWIW on my car I have 225 & 245's push is negligable, and the car rotates with loud pedal application nicely.. I may have just hit a sweet spot in the chassis set up, but I wouldnt worry about having narrower rubber up front

It'll be a fun season of tire testing for me.

Thanks for your replies ( even MattR's )


KT

Here's what they look like now.
The wear dimples and bars are clearly still visable.


KT

Here's what the Yok 032R's look like

KT

Oops...what is that big whitish spot on the bottome Yoko?
I think the yokos are toast...

My experience with Hoosiers is they are worn out long before they look worn out. Those Yokos look like they'd make better planters than track tires.

QUOTE (Dan (Almaden Valley) @ Apr 5 2006, 05:45 PM)

Oops...what is that big whitish spot on the bottome Yoko? I think the yokos are toast...

That was from when Trekkor was "testing" his Porterfield pads.

Here is a quick pic of what I got today.
Set of Kumho Vics.

They are only slightly used. All 4 still have the wear dimples in clear view.

Price was right

QUOTE (Dan (Almaden Valley) @ Apr 5 2006, 06:08 PM)

Here is a quick pic of what I got today. Set of Kumho Vics. They are only slightly used.  All 4 still have the wear dimples in clear view. Price was right

I have the same Victoracers on my car although mine are a wee bit wider - couldnt beat the price as well. They dont stick as well in AX as the Hoosiers or 710s, but from everyone I have spoken to they last and last and still stick well on the track once they are warm.

I am however considering 710's for my car as well once I wear through the Victoracers.

Trekkor, I'm a driver who still buys whatever is on sale but I'll add my dos pesos. In the bicycle world of racing Tubulars are still the rage because of the high PSI you can run. High PSI (180-200) is great for less rolling resistance but bad for traction because of the stiffer sidewall flex (or lack of). Not as you would expect (side to side) but up and down (like a damper). In other words, maybe MattR was referring to sidewall flex in this light. Another example of sidewall flex is the Michelin Airless tire photos, notice the up and down flex and not the side to side. Bike racers may say I'm wrong and auto racers may say this doesn't apply.....