Hopping on corner exit
May 13, 2019, 09:52 AM
#31
Evolving Member
I think a simple test for some of these cars is to just unhook the bars on the car and see if the problem goes away.
The problem was worse for us with the TRE diff, which makes sense if you think about the bind it is causing. However we changed too many things at once to know if this was the problem.
Our car has no hop at all anymore, but it isn't much like an evo anymore either....
Zack
The problem was worse for us with the TRE diff, which makes sense if you think about the bind it is causing. However we changed too many things at once to know if this was the problem.
Our car has no hop at all anymore, but it isn't much like an evo anymore either....
Zack
May 13, 2019, 11:27 AM
#32
EvoM Guru
honestly, diffs are not related to sway bars directly. What you are feeling however is the changing drive characteristics in your rear end caused by a tighter diff and/or lsd effect and therefore u feel a need to change the torsional stiffness created by a swaybar.
Swaybars control bodyroll and torsional stiffness front to rear and primary function is to increase or decrease understeer or oversteer. Spring rate and shocks are independant of this and control the individual wheel and its relationship with the tarmac.
Using stiffer springs will not remove the requirement for an anti rollbar as such because u need that torsional stiffness linking the corners to control bodyroll.
Buuuuttt they are all related to each other and u change one thing and it will affect everything else haha so thats where it gets muddy and where u need to go away and read numerous really thick books so u still have no idea how it all really works as is my case hahaha.
Swaybars control bodyroll and torsional stiffness front to rear and primary function is to increase or decrease understeer or oversteer. Spring rate and shocks are independant of this and control the individual wheel and its relationship with the tarmac.
Using stiffer springs will not remove the requirement for an anti rollbar as such because u need that torsional stiffness linking the corners to control bodyroll.
Buuuuttt they are all related to each other and u change one thing and it will affect everything else haha so thats where it gets muddy and where u need to go away and read numerous really thick books so u still have no idea how it all really works as is my case hahaha.
May 14, 2019, 07:24 AM
#33
I put in my first events on the new coilovers and Cusco rear diff. HOP CITY. Enough so that I saw pictures of my car where both passenger size tires were in the air.
I believe MOST of my issue is I'm overly sprung for a lot that is far from smooth in areas. But I also believe that the rear diff could be attributing to some of the hop? Is that possible? I mean logically speaking if you are taking a sweeper and on the throttle slightly, the outter wheel is naturally going to want to spin faster than the inner, thus loading up that outter rear corner?! Tell me if I'm off here....... If so, throw in some friction modifier to see if that tames things down a bit? Thoughts?!
I will say, this Cusco rear diff WORKS. I previously was running on the Weir 12 plate "upgrade" which to me, almost made no difference. With the Cusco, in the rain or the dry, my under-steer issues are no longer prevalent. But the hopping is extremely concerning. I will probably have to drop my rates back down to something more manageable for this local lot, but throw on the stiffer rear springs for Lincoln. Compromises....
I'm entered in Spring Nationals in a couple weeks in Lincoln. Us ASP guys are bumping up to SM so it'll be a good test to see how she handles things there. I'm going to leave the spring rates alone and see how it performs. But I'm going to bring a set of softer rears to swap in if it's still bad........The joys of getting the car set up correctly again.
I believe MOST of my issue is I'm overly sprung for a lot that is far from smooth in areas. But I also believe that the rear diff could be attributing to some of the hop? Is that possible? I mean logically speaking if you are taking a sweeper and on the throttle slightly, the outter wheel is naturally going to want to spin faster than the inner, thus loading up that outter rear corner?! Tell me if I'm off here....... If so, throw in some friction modifier to see if that tames things down a bit? Thoughts?!
I will say, this Cusco rear diff WORKS. I previously was running on the Weir 12 plate "upgrade" which to me, almost made no difference. With the Cusco, in the rain or the dry, my under-steer issues are no longer prevalent. But the hopping is extremely concerning. I will probably have to drop my rates back down to something more manageable for this local lot, but throw on the stiffer rear springs for Lincoln. Compromises....
I'm entered in Spring Nationals in a couple weeks in Lincoln. Us ASP guys are bumping up to SM so it'll be a good test to see how she handles things there. I'm going to leave the spring rates alone and see how it performs. But I'm going to bring a set of softer rears to swap in if it's still bad........The joys of getting the car set up correctly again.
May 14, 2019, 07:30 AM
#34
I think a simple test for some of these cars is to just unhook the bars on the car and see if the problem goes away.
The problem was worse for us with the TRE diff, which makes sense if you think about the bind it is causing. However we changed too many things at once to know if this was the problem.
Our car has no hop at all anymore, but it isn't much like an evo anymore either....
Zack
The problem was worse for us with the TRE diff, which makes sense if you think about the bind it is causing. However we changed too many things at once to know if this was the problem.
Our car has no hop at all anymore, but it isn't much like an evo anymore either....
Zack
I just saw this, so my thoughts must inline.
I did put my rear bar on full soft (it was on 2nd to highest stiffness rating). That didn't seem to change things much though.
May 14, 2019, 07:48 AM
#35
I put in my first events on the new coilovers and Cusco rear diff. HOP CITY. Enough so that I saw pictures of my car where both passenger size tires were in the air.
I believe MOST of my issue is I'm overly sprung for a lot that is far from smooth in areas. But I also believe that the rear diff could be attributing to some of the hop? Is that possible? I mean logically speaking if you are taking a sweeper and on the throttle slightly, the outter wheel is naturally going to want to spin faster than the inner, thus loading up that outter rear corner?! Tell me if I'm off here....... If so, throw in some friction modifier to see if that tames things down a bit? Thoughts?!
I will say, this Cusco rear diff WORKS. I previously was running on the Weir 12 plate "upgrade" which to me, almost made no difference. With the Cusco, in the rain or the dry, my under-steer issues are no longer prevalent. But the hopping is extremely concerning. I will probably have to drop my rates back down to something more manageable for this local lot, but throw on the stiffer rear springs for Lincoln. Compromises....
I'm entered in Spring Nationals in a couple weeks in Lincoln. Us ASP guys are bumping up to SM so it'll be a good test to see how she handles things there. I'm going to leave the spring rates alone and see how it performs. But I'm going to bring a set of softer rears to swap in if it's still bad........The joys of getting the car set up correctly again.
I believe MOST of my issue is I'm overly sprung for a lot that is far from smooth in areas. But I also believe that the rear diff could be attributing to some of the hop? Is that possible? I mean logically speaking if you are taking a sweeper and on the throttle slightly, the outter wheel is naturally going to want to spin faster than the inner, thus loading up that outter rear corner?! Tell me if I'm off here....... If so, throw in some friction modifier to see if that tames things down a bit? Thoughts?!
I will say, this Cusco rear diff WORKS. I previously was running on the Weir 12 plate "upgrade" which to me, almost made no difference. With the Cusco, in the rain or the dry, my under-steer issues are no longer prevalent. But the hopping is extremely concerning. I will probably have to drop my rates back down to something more manageable for this local lot, but throw on the stiffer rear springs for Lincoln. Compromises....
I'm entered in Spring Nationals in a couple weeks in Lincoln. Us ASP guys are bumping up to SM so it'll be a good test to see how she handles things there. I'm going to leave the spring rates alone and see how it performs. But I'm going to bring a set of softer rears to swap in if it's still bad........The joys of getting the car set up correctly again.
Cliffs on how Ive fixed it, More rear spring, less rear bar, raise front RC (via RC correction or raise the front of the car). More rear camber helps a bit too.
How much pressure are you running in the A7s? If you down in the low 30s then that can cause it too. Should be in the upper 30s on the standard ASP tire (285 or 295)
May 14, 2019, 08:10 AM
#36
The Cusco will definitely being doing better than the weir which is notorious for being crap and wearing out prematurely. So remember, every time you make the car turn better it will be more likely to hop. Have the car just right on asphalt? Go to concrete and back to hop-city. Read by through my notes because Ive gone through hop, no-hop, hop, no-hop, hop, very-little-hop... Basicall everytime the car gets more grip, I get to chase it again.
Cliffs on how Ive fixed it, More rear spring, less rear bar, raise front RC (via RC correction or raise the front of the car). More rear camber helps a bit too.
How much pressure are you running in the A7s? If you down in the low 30s then that can cause it too. Should be in the upper 30s on the standard ASP tire (285 or 295)
Cliffs on how Ive fixed it, More rear spring, less rear bar, raise front RC (via RC correction or raise the front of the car). More rear camber helps a bit too.
How much pressure are you running in the A7s? If you down in the low 30s then that can cause it too. Should be in the upper 30s on the standard ASP tire (285 or 295)
I appreciate the insight, Dallas!
Lots to think about here. The dilemma I have is locally the lot is rough. There's no way I can go higher in the rear (1000lb +/- currently) without making it worse, because of how rough this lot is. So locally here, I just run on RE71R's in a 285/30/18. A7's are known to cord within about 6 events here, as the lot is by far, the most abrasive asphalt I've been on. I was running pretty low pressures on the RE71's this weekend, around 34 front/rear. I will try bumping up the rear possibly to see if that helps.
I am going to try raising the front as it's currently around 25.5", which is much lower than I was running last year. The rear is set to 25.0". I can't legally run the roll correction in ASP so I'll try raising it up a bit more.
Battle plan for now then: 1) raise front ride height to 26.0 - 26.5" 2) dial in more neg camber out back if possible (I think I'm around -2.0, I'd have to double check.) 3) Up the rear tire pressure
In regards to when I ran on the A7's, I believe I was in the mid 30's up front and then low 40's out back to TRY and get rotation. When I go to Lincoln for Spring Nats, Nats and regular points events, I will be on my A7's.
Last edited by LV///R; May 14, 2019 at 08:29 AM.
May 14, 2019, 08:33 AM
#37
At some point you do have to decide does it matter if the car is right at national sites or local sites. Trying to sit in the middle of both really just makes it not great either place. I gave up on caring too much about local points and just use it as an opportunity to try different things. Since really all that matters are national level events anymore, thats all we worry about for setup direction.
I think you're on the right track though. 1000 front would probably make me want something like a 24mm rear bar max and 700lb front spring with stock front bar + adj bracket. Raising front to 26.25-26.5 would be my suggestion. Dont make a small change expecting a major difference, Something like 26.5 front and 25.75 rear would be a good start.
I think you're on the right track though. 1000 front would probably make me want something like a 24mm rear bar max and 700lb front spring with stock front bar + adj bracket. Raising front to 26.25-26.5 would be my suggestion. Dont make a small change expecting a major difference, Something like 26.5 front and 25.75 rear would be a good start.
May 14, 2019, 08:44 AM
#38
At some point you do have to decide does it matter if the car is right at national sites or local sites. Trying to sit in the middle of both really just makes it not great either place. I gave up on caring too much about local points and just use it as an opportunity to try different things. Since really all that matters are national level events anymore, thats all we worry about for setup direction.
I think you're on the right track though. 1000 front would probably make me want something like a 24mm rear bar max and 700lb front spring with stock front bar + adj bracket. Raising front to 26.25-26.5 would be my suggestion. Dont make a small change expecting a major difference, Something like 26.5 front and 25.75 rear would be a good start.
I think you're on the right track though. 1000 front would probably make me want something like a 24mm rear bar max and 700lb front spring with stock front bar + adj bracket. Raising front to 26.25-26.5 would be my suggestion. Dont make a small change expecting a major difference, Something like 26.5 front and 25.75 rear would be a good start.
I agree. That thought has crossed my mind plenty of times. Much more so after this weekends festivities. (Still pulled FTD both days, even with the nasty bouncing)
To have this car set up to be even at all competitive at National events, will mean it will be an absolute **** show locally with how rough the lot is getting. My car was a compromise last year and was mainly to dip my feet into Nationals to see what it was all about. Now I'm hooked and that truly is my main focus. The plan this year was to attend as many events in Lincoln as I could (3.5 hour drive - car would be driven there) and run on the A7's there. Then just simply run locally on the RE71's. I think I was being optimistic that would work....haha.
However, I'll try your suggestions and play with the ride height initially. I'm on 800lb Front and 1000lb Rears with just a 24mm adjustable rear bar.
As always, your help is MUCH appreciated.
May 14, 2019, 11:14 AM
#39
EvoM Guru
the hopping when u install a better rear diff isnt caused by the diff itself. its come from the better performance as a result of installing the rear diff. it has nothing to do with the actual diff
Remember with suspension and alignment its all related, u make one change and its going to affect 10 other things. You change ur spring rates and you may need to re valve your shocks to suit, you change bars u may need to up or lower spring rates so they work together etc. its all a big dance where everything needs to work together. Follow dallas' advice. try softening rear bar to keep inside wheel on the ground. or raise the front rollcenter so its not diving too hard on the outside front etc...
Remember with suspension and alignment its all related, u make one change and its going to affect 10 other things. You change ur spring rates and you may need to re valve your shocks to suit, you change bars u may need to up or lower spring rates so they work together etc. its all a big dance where everything needs to work together. Follow dallas' advice. try softening rear bar to keep inside wheel on the ground. or raise the front rollcenter so its not diving too hard on the outside front etc...
Jun 13, 2019, 08:15 PM
#40
Been meaning to post here for a while but keep forgetting. I got my car shaken down a couple weekends ago and the biggest issue by far right now is getting this corner exit hop sorted.
Here's my action plan to try and get this sorted:
- Bump up rebound on the rear shocks (they're actually really soft right now)
- Soften the rear swaybar (if that doesn't have a very measurable effect I'll try disconnecting it
- Add another 0.5° of camber in the rear
- New tires that aren't 5 year old RC1s
- Put stiffer springs in the rear (from 12k to 16k)
- Raise the front or lower the rear more (probably lower the rear)
I'll be sure to report back what works well and how easily I'm able to get this resolved.
Here's my action plan to try and get this sorted:
- Bump up rebound on the rear shocks (they're actually really soft right now)
- Soften the rear swaybar (if that doesn't have a very measurable effect I'll try disconnecting it
- Add another 0.5° of camber in the rear
- New tires that aren't 5 year old RC1s
- Put stiffer springs in the rear (from 12k to 16k)
- Raise the front or lower the rear more (probably lower the rear)
I'll be sure to report back what works well and how easily I'm able to get this resolved.
Jun 14, 2019, 11:03 AM
#42
Been meaning to post here for a while but keep forgetting. I got my car shaken down a couple weekends ago and the biggest issue by far right now is getting this corner exit hop sorted.
Here's my action plan to try and get this sorted:
- Bump up rebound on the rear shocks (they're actually really soft right now)
- Soften the rear swaybar (if that doesn't have a very measurable effect I'll try disconnecting it
- Add another 0.5° of camber in the rear
- New tires that aren't 5 year old RC1s
- Put stiffer springs in the rear (from 12k to 16k)
- Raise the front or lower the rear more (probably lower the rear)
I'll be sure to report back what works well and how easily I'm able to get this resolved.
Here's my action plan to try and get this sorted:
- Bump up rebound on the rear shocks (they're actually really soft right now)
- Soften the rear swaybar (if that doesn't have a very measurable effect I'll try disconnecting it
- Add another 0.5° of camber in the rear
- New tires that aren't 5 year old RC1s
- Put stiffer springs in the rear (from 12k to 16k)
- Raise the front or lower the rear more (probably lower the rear)
I'll be sure to report back what works well and how easily I'm able to get this resolved.
Jun 14, 2019, 12:35 PM
#43
I had mild hopping on my rear corner on some exits at autocross. Once I got TRE's rear diff, it made it a lot worse. Noting that my tires were pretty heat cycled out, from daily driving/autocross. Now since I got new tires, the hopping was reduced a ton. I think it has something to do with the rear corner trying to put power down so it squats, losses grip so it stops transferring power(maybe that how it works?) stops squatting, tries to put power down again, squats and rinse and repeats during that corner exit.
I think I'll reduce the rear sway bar a bit and see what happens.
Last edited by kaj; Jun 14, 2019 at 04:47 PM.
Jun 14, 2019, 01:38 PM
#45
Theoretically increasing rebound would help because the shock will help push the tire back to the ground and minimize that loss of contact time.