Tire Test: Is the value-priced X Comp H/P a 200tw contender?

What happens when you own a tire company and want some appropriate rubber for your own sports cars? You get it done. 

Since 1982, X Comp and its associated brands have been successfully building a variety of tires for a wide range of markets: tractor-trailers and golf carts, ATVs and off-road trucks. In 2016, the company entered the off-road motorsports …

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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 GAM :

Take some air out of the tire