Front Wheel Hop Issue

[cody]

I'm having trouble putting down power, mainly when I shift into 1st as I apex and then roll on the throttle coming out of a sharp turn. Mike K and Sperry both said they saw my front wheel (I'm assuming the inside front wheel) hop. On Sunday, I combated the issue by simply not shifting down to 1st at all.

Now since the latest thing I've done is added a little power (mainly torque) and earlier spool and stiffer springs, I think the solution is better dampening struts. The KYB AGX's on full stiff don't seem to be dampening the springs enough. A set of Koni Inserts is my proposed solution, but I really don't want to spend the money if it's not necessary.

Alex suggested that perhaps replacing the front sway with a larger diameter bar might help. It's stock now but I do have Karboy endlinks already so this would be a cheap fix, but I have no idea if it's a smart move or not. My car is a little tail happy so it might not be a bad idea.

I've always wanted to keep the stock front sway, mainly just because I believe going thicker will make the car less drivable on uneven/slippery surfaces.

Thoughts?

[NevadaSTi]

Originally Posted by cody

I've always wanted to keep the stock front sway, mainly just because I believe going thicker will make the car less drivable on uneven/slippery surfaces.

Thoughts?

When I put on that big ass 32mm FSB on my car, I didn't notice a difference in its ability to handle slippery conditions. And I have 8 hours worth of driving over I80 during a snow storm with no problems what-so-ever to back it up.

[Dean]

Full stiff is likely the problem. It is likely over damping rebound and is preventing the tire from coming down as the body rolls. You could try turning that back down...

The success people have had with large front bars is proven, so get the largest wagon front bar you can, and if it really bothers you, swap back for the winter.

[cody]

I did try dialing it back to 3 (4 is stiffest) and it exaserbated the issue. Plus I never had this issue with the softer Eibach Springs... I guess I'll look at an adjustable front sway but I kinda doubt it will remedy this issue.

[sperry]

First thing to note: you don't have a front LSD like the STi folks, so keep that in mind when talking about loss of traction up front. The STi will just transfer power to the other wheel if there's a little front hop/loss of traction, so they may actually have the same issue with the suspension but no traction loss because of the LSD. i.e. What works on the STi may not work on the WRX, like going to that massive sway-bar... (though I think a stiffer FSW actually wouldn't hurt).

Now, with regards to the suspension... how stiff are your springs? I would agree it sounds like you're under-dampened. But the solution might not be more damper, but less spring. A general rule of thumb is that you want to add grip to fix handling issues, rather then remove grip. A softer front end, might actually solve the wheel hop problem *and* gain you turning/braking traction. But a soft front-end might make the car too tail-happy as well... how's the handling balance outside of the corner-exit wheel-hop?

If you want to try some Koni's, I've still got that set of Koni/GC coilovers, and a butt-load of springs. They might be a little stiff of a match to your rears, but if we slap 'em on w/ the softest springs I've got, you might be able to get a feeling for whether or not your issue is damping related or spring rate related. Either way, if you want to try 'em out, I'd be happy to let you borrow 'em (since no one seems interested in buying them).

Another idea: camber. Do you have camber plates? Too much or too little might reduce traction on the tire allowing it to spin... maybe the "hop" is actually a side effect of wheel spin, instead of the other way around.

Finally, it may just be the nature of putting that much power down through the WRX 5MT. That open diff sucks... you may just have to be "more educated" with your throttle application. You might be able to drive around the limitation, though it would be faster of course if you can figure out a mechanical fix and just stop on the throttle like usual.

[Nick Koan]

Like Brian, I didn't notice any less drivability on slippery conditions with a larger front sway bar. I think that's probably what you need.

Also, I would think you should be able to find an adjustable FSB where the lowest setting isn't higher than stock. That might be ideal for you.

[cody]

Originally Posted by sperry

First thing to note: you don't have a front LSD like the STi folks, so keep that in mind when talking about loss of traction up front. The STi will just transfer power to the other wheel if there's a little front hop/loss of traction, so they may actually have the same issue with the suspension but no traction loss because of the LSD. i.e. What works on the STi may not work on the WRX, like going to that massive sway-bar... (though I think a stiffer FSW actually wouldn't hurt).

Now, with regards to the suspension... how stiff are your springs?

Spring rate front: 257 lb/in

Spring rate rear: 217 lb/in

Drop front: 1.25" on WRX, 12.5 mm on STi

Drop Rear: 0.9" on WRX, 9.0 mm on STi.

"These are the same high performance spring rates as the highly-lauded and thoroughly-tested JDM STi "Pinks," but the Crucial springs have better materials quality, smoother progressive rates (plus are progressive both front and rear, while the JDM Pinks are only progressive on the rear, and linear front), offer slightly more drop up front for a nicer, more even stance (JDM Pinks are 1.0" both front and rear on WRX, 10mm front/rear on STi)"

I would agree it sounds like you're under-dampened. But the solution might not be more damper, but less spring. A general rule of thumb is that you want to add grip to fix handling issues, rather then remove grip. A softer front end, might actually solve the wheel hop problem *and* gain you turning/braking traction. But a soft front-end might make the car too tail-happy as well... how's the handling balance outside of the corner-exit wheel-hop?

It handles noticeably better since I upgraded the springs. I get less body roll and with my current alignment specs (2.2 neg. in the front, 2.0 in the rear) she's just slightly tail happy, but still easy to drive, aside from this wheel spin issue. Rusty was looking at my tire temps and the front is perfect while he actually wants to add a touch more neg. camber to the rear based on the temps.

If you want to try some Koni's, I've still got that set of Koni/GC coilovers, and a butt-load of springs. They might be a little stiff of a match to your rears, but if we slap 'em on w/ the softest springs I've got, you might be able to get a feeling for whether or not your issue is damping related or spring rate related. Either way, if you want to try 'em out, I'd be happy to let you borrow 'em (since no one seems interested in buying them).

Another idea: camber. Do you have camber plates? Too much or too little might reduce traction on the tire allowing it to spin... maybe the "hop" is actually a side effect of wheel spin, instead of the other way around.

See above...I don't think camber is an issue here...

Finally, it may just be the nature of putting that much power down through the WRX 5MT. That open diff sucks... you may just have to be "more educated" with your throttle application. You might be able to drive around the limitation, though it would be faster of course if you can figure out a mechanical fix and just stop on the throttle like usual.

Word, but I'm still wondering if adding more spring (which is what a front swaybar is) will actually exaserbate the issue. Sways actually load the outside wheel more so wouldn't the inside wheel be more apt to lift or no? Maybe keeping the front flatter will help this issue? I don't know.

[Dean]

Tire temps other than on a skidpad are largely misleading. -2 rear sounds too high with only 2.2 front. Delta front-rear typically optimal on WRXs is about 1 degree less in the rear.

On the WRX, front sways are largely about fixing a roll-camber issue especially when lowered which you are. Yes, they transfer weight, but keeping the front flat is more important, and will likely keep that wheel down enough to keep applying some power.

The problem with most 1 way shocks like the AGX is that bump and rebound are tied together. Higher rebound keeps the spring from putting the tire back on the ground in transitional movement which is common in autocross, especially all the Z turns we had this weekend. On smooth surfaces like Stead, you can tolerate more bump, but not the rebound that often comes with it.

Font bars are proven to improve Impreza handling by minimizing the roll-camber issue. I would start there before replacing shocks.

[sperry]

The FSW should help, since it will actually add spring to the outside wheel and *reduce* spring to the inside wheel.

Also note that perfectly even temps across the tire may indicate too little negative camber for ultimate cornering grip. Straight line braking will heat the inside of the tire more than the outside, and cornering will heat the outside more than the inside. You may be able to pick up more overall cornering at a slight expense to outright braking ability, and go faster over-all with hotter inside temps. The only real way to know is to have real-time telemetry of tire temps during the run and figure out where you're losing time, but sometimes if you play with it a bit, you'll be able to sort it out w/ trial and error. But if Rusty says "it looks good", it's probably pretty dialed, he did a pretty good job w/ my setup.

If you're going to add neg camber in the rear, you'll probably end up getting a little pushy, in which case going back to a softer front spring might be just what the doctor ordered. Keep in mind that stiffer can "feel" much better, but can actually be slower. On the other hand, you're running some relatively soft rates all around. Hell, I'm running like 670/560 rates on my car... (Which reminds me, your rear springs are much too soft to match up at all w/ any of the springs I've got for the Konis...)

[Dean]

Originally Posted by sperry

Also note that perfectly even temps across the tire may indicate too little negative camber for ultimate cornering grip. Straight line braking will heat the inside of the tire more than the outside, and cornering will heat the outside more than the inside. You may be able to pick up more overall cornering at a slight expense to outright braking ability, and go faster over-all with hotter inside temps. The only real way to know is to have real-time telemetry of tire temps during the run and figure out where you're losing time, but sometimes if you play with it a bit, you'll be able to sort it out w/ trial and error. But if Rusty says "it looks good", it's probably pretty dialed, he did a pretty good job w/ my setup.

Scott's initial comment is correct, but there is more to it, and I'm not sure real time data helps for initial setup.

In addition to braking, turning the other way also raises inside temps, so a skid pad is the only real way to get cornering contact patch related tire temp info. Cold tires, run 5-10 even no under-oversteer laps. Slow to a stop quickly but with minimal braking, Check temps accross outside tires. Let tires cool. change pressure, repeat.

Given this weekend's courses, I would expect about 10-20 degree hotter or maybe more inside temps in the front on a good clean minimal understeer run. Rear I don't care about much as they get adjusted to overall car feel rather than ultimate grip at that end in most cases. A straight progression is about right to me most of the time.

Outside = X, center = X+n, inside = X+2n where n is in the 5-10 maybe 15 range. It's actually a whole lot more complicated than that, but that is a good starting place for autocross at least.

[cody]

Cool. Thanks for the input guys.

[sperry]

Originally Posted by Dean

Scott's initial comment is correct, but there is more to it, and I'm not sure real time data helps for initial setup.

In addition to braking, turning the other way also raises inside temps, so a skid pad is the only real way to get cornering contact patch related tire temp info. Cold tires, run 5-10 even no under-oversteer laps. Slow to a stop quickly but with minimal braking, Check temps accross outside tires. Let tires cool. change pressure, repeat.

Given this weekend's courses, I would expect about 10-20 degree hotter or maybe more inside temps in the front on a good clean minimal understeer run. Rear I don't care about much as they get adjusted to overall car feel rather than ultimate grip at that end in most cases. A straight progression is about right to me most of the time.

Outside = X, center = X+n, inside = X+2n where n is in the 5-10 maybe 15 range. It's actually a whole lot more complicated than that, but that is a good starting place for autocross at least.

+1, this is well said. I've found on my car that when it's handling good, the temps are linear across the tire but not equal. However, at the track I try to get them as equal as possible since that's going to get me the most tire-life, and friggen race tires are expensive!

[cody]

I just picked this Whiteline adjustable front sway up for $115 shipped.

[cody]

Anyone know if I will need upgraded mount bushings for the front bar? Does the Whilteline bar come with them?

[M3n2c3]

I believe they include bushings when new.

[wrxkidid]

im pretty sure they come with bushings but not HD mounts.

[cody]

Woohoo, it came today and not only did it come with the bushings I was expecting, but it also came with some little yellow bushings with hose clamps around them. Guess I'll figure out what they're for when I go to install it.

[Dean]

Originally Posted by cody

Woohoo, it came today and not only did it come with the bushings I was expecting, but it also came with some little yellow bushings with hose clamps around them. Guess I'll figure out what they're for when I go to install it.

Those keep it from sliding sideways. Should go inside of main brackets.

[cody]

Cool, thanks. I'll just be using the 5 year old DIY on scoobymods...hopefully it all goes smooothly.

[A1337STI]

How does it feel with the new sway bar ? is it a 22-24 adjustable ?

[cody]

Yah, Whiteline only makes 22mm bars for Wagons and I set it at the stiffer setting. Works great. The car feels flatter in the corners but no noticeable increase in NVH. I haven't checked to see if I still have the wheel hop issue because I'm running all season tires and I'm having a boost leak issue or something so my car is currently detuned.

Details on this new issue: http://www.wrxfanatics.com/index.php...pic=51672&st=0

[M3n2c3]

Originally Posted by cody

I'm having a boost leak issue or something so my car is currently detuned.

Statements like that always make me momentarily glad that I just have an RS and can't really get myself in to trouble with it.




. . .sorry, I'll go now.

[cody]

Whatever you have to tell yourself.

[Jesubi11]

Originally Posted by cody

Whatever you have to tell yourself.

[M3n2c3]

Originally Posted by Jesubi11

Pipe down, Boy Racer.


Momentarily was the key word there. Then the stark reality sinks back in.




. . .