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Hello guys. Tire Rack website shows 8.5 inches tread width for the Bridgestone Potenza RE71RS and I see that you have 9.8 inches tread width here. What's going on?
Yep, 9.8 is Section Width for each tire, not tread width. Good eye!
Missed that in the proofing process. That chart was created after the story left my hands and the mistake wasn't caught on review.
Sigh...
I like these tires, but m y Golf-R understeers bad. Despite the -3.5° camber and 38 PSi hot (these values are from the front tires) it understeers bad. The RE71RS over heat quickly, and the "V" markers on the front tires are trespassed. I got the thickest anti-roll bars front and rear, they are 25.6mm in the rear and up front too.
What can I do ?
Gerhard
In reply to GAM :
I haven't owned a FWD in 20 years now, so this may not work the way I think it should, but try disconnecting your rear sway bar. My Miata would not turn in to save its life, due to really limited camber. Popped the rear end links off the sway bar, and that helped turn in quite a bit.
In reply to GAM :
I would have left the rear bar bigger than the front. Have you tried messing with your toe settings?
Fcyaa said:Hello guys. Tire Rack website shows 8.5 inches tread width for the Bridgestone Potenza RE71RS and I see that you have 9.8 inches tread width here. What's going on?
Yes, thanks for catching that. I've adjusted the chart in the story.
In reply to GAM :
Understeers bad could also be overdriving a corner; does the car swap ends quickly, or does it only plow all the time?
Also, more rear stiffness (generally) will let the back end come around easier. The faster you go the more the car turns from responsive to squirrelly as you up rear stiffness, though.
Let's talk about rear stiffness and FWD for a moment.
It doesn't work the same as on the typical well-balanced (50/50) RWD platform like a Miata or BMW. In those cases, altering relative roll stiffness front-to-rear will affect the car through out the entire cornering phase -- entry, mid, and exit. It does this by altering how much weight is transferred at each end.
With the typical nose-heavy FWD car, it's pretty easy to transfer *all* of the weight at the rear of the car in a corner. That's what causes the rear to top-out the suspension and come off the ground. Once you have enough rear roll stiffness for this to happen, either through anti-roll bar or springs, you cannot further alter the balance of the car. You *can* alter when this happens in a turn, however. Stiffen the rear enough and it begins rotation super-early in the corner, understeers in the middle and then allows for earlier throttle application on exit to balance the tendency for oversteer.
This is commonly called setting the car up just this side of "killing you on entry" so you can get early drive off the corner. Go too far, however, and you're that "tank slapper guy". We've all seen that guy.
Hmmm,..I sense a tech story here....
Andy Hollis said:Hmmm,..I sense a tech story here....
In reply to Andy Hollis :
Great stuff, what I've experienced in my Mini, though if you drive in the rain with the car set up to "kill you on entry" it just might.
gbuff said:In reply to Andy Hollis :
Great stuff, what I've experienced in my Mini, though if you drive in the rain with the car set up to "kill you on entry" it just might.
This is where having a big rear that can be easily disconnected comes into play. Adjustable dampers, roo.
When grip is low, you can't transfer all the weight off the rear in a turn. So what was the corner entry phase only in the dry is the entire cornering phase in the wet.
GAM said:I like these tires, but m y Golf-R understeers bad. Despite the -3.5° camber and 38 PSi hot (these values are from the front tires) it understeers bad. The RE71RS over heat quickly, and the "V" markers on the front tires are trespassed. I got the thickest anti-roll bars front and rear, they are 25.6mm in the rear and up front too.
What can I do ?
Gerhard
If the understeer is on entry,
You need a softer front sway bar and a stiffer rear sway bar.
More caster can help you get more dynamic camber in corners.
Soften the front and stiffen the rear if you have adjustable shocks.
Increase tow out in the front and rear.
Lift off the throttle to transfer weight the front and induce the rear to rotate.
In reply to GAM :
I run an Audi TT with about -4 degrees of camber. I have a very stiff suspension and I actually disconnected my front bar and have removed the rear big bar I had and modified my OEM bar to make it slightly stiffer than stock. Understeer is very good. Although I do also run Hoosier 275/35/17 and about 32psi up front.
In reply to Andy Hollis : have an srt-4 that was once described as "the only car on the field with snap over and under steer" lol
Front wheel drive formula:
Big rear bar and higher rear tire pressure to loosen the rear and help with rotation. I leave the shocks soft in front, firm in back. Fine tune with the tire pressures.
Floating Doc (Forum Supporter) said:Front wheel drive formula:
Big rear bar and higher rear tire pressure to loosen the rear and help with rotation. I leave the shocks soft in front, firm in back. Fine tune with the tire pressures.
That car will be faster with a big front bar added.
The big rear bar loses all effectiveness as soon as all the weight comes off the inside rear tire, which appears to be happening very early in the turn.
A larger front bar will help overall body roll which is killing your dynamic camber, reducing front grip. More front grip will reduce understeer.
Rear toe out will also help, by adding rear slip angle compared to the front.
Oh wait...I already said all that. But it bears repeating.
In reply to Andy Hollis :
Totally in lock-step on what Andy is saying for setup on an FWD car.
With the add of watch out for Sway-bar binding at the end links. If the bar binds in flex it will lockup the front suspension causing understeer.
Watch out for strut bottoming out and causing understeer also. The Large front sway bar can keep the strut from bottoming.
In reply to GAM :
Step one: Add a lot of air to the front tires... Maybe +10 psi. See what this changes. Check tire temp across the surface.
Step two: Reduce the front tires to 1/2 of what you added... +5psi. See what happens. Check tire temp across the surface.
Step three: Now test to 1/2 of the upper (+7.5)psi and lower (+2.5)psi... This will zone you in on the best pressure.
This should get the front tire pressure set.
Repeat this for the rear. ... You may have to bump rear pressures significantly higher. Back in the day I was 10psi higher in the rear to get consistent rotation ... This is the "Trying to kill you" set up that is REALLY fast when mastered.
In the rain, I would just drop the rear pressure by down to the same as the front and soften shocks at both ends to get a more stable car.
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