Hey hosers and hossettes.
For all you RC Gen 8/Axe owners out there, who notice steering issues, and have found various semi fixes to the steering problems as well as the bump steer issues these rigs see, along with the front axle shift as the suspension compresses (limited improvements here due to layout and geometry which will take more attention to correct or improve) they also have, this thread should help you know whats a required solution, and what only seems like a solution.
For those that know me from days gone past, this won't be much new, but for those that have come since I got out nearly a decade ago, you may find this interesting, lol or not.
So. out of the box the front end works. Not great, but it does what it should, just not HOW it should. lol The bump steer was fairly significant, and some of the 'fixes' offered are good in that they address the correct issue, instead of something that doesn't but tries something to change the setup to work better, in some ways, tackling a minor issue, and in other masking or making the main issue worse.
I had a f-it night, and pulled out the Axe around 1:30 am and finally crashed about 6ish as the Sun was coming up.
First I'll address the axle shift.
If you look, as the front suspension compresses, the axle starts to shift to the right side (passenger). The more compression of the right shock the more shift introduced. However, the left side (Drivers) can compress fully up front, and it induces zero axle shift from what I could see. I studied the front end as it moved through its stages noting what/where/why was going on.
The simple answer is the pan hard setup. Ignoring the plastic axle panhard mount that flexes a bit, and needs to be addressed with an aluminum mount (a few options are out there, RedCats own link mounts, SSD's sets, & Chy-Na specials. I have the SSD in my cart atm), the design/layout/set-up of the pan hard introduces the shift. The reason its only the right side that does it is the pan hard mounts on the right side of the axle. If it was opposite and mounted on the left, then that side would be introducing the shift with the current setup.
Ealier, a month or so back, I posted about this, and to address it I started shortening the pan hard link ends. The problem is as the right side suspension compresses, the pan hard bar starts pushing the axle outward (passenger side) because of its length and position of the mounts.
By shortening the link ends a bit, it shortened the overall length of the panhard so when the left side compresses, the pan hard didn't shift the axle as much as it was a few mm shorter (about 5-6mm total, 3mm from each link end).
This helped, but the amount of shift was still quite long. I went ahead and tried to shorten some link ends further. But it didn't take long before the axle when unsprung started to pull on the left side, shifting the axle again. This is because I made the bar too short with the shortened ends. So there is a Sweet Spot on these rigs, and with its current setup, the best you can hope to improve. I'll get it sorted and post back how long each rod end is. Will also get a few angled rod ends just to see if they'll help any.
I am thinking a well formed S bend pan hard bar, and an angled end on the axle side may help more, but even then, without fully redesigning the mount locations, angles, pan hard bar, link end geometry, the best we are going to end up with is zero axle shift under left side compression, and some (a bit less than 1/4 inch maybe) shift under full right side suspension compression.
I'll grab some pics and detail what I did in the next post to improve the axle shift as best as it can be.
On to the steering issue and bump steer problem.
First the steering issue. This is a bit of a geometry/layout issue but is correctable without the need for spending too much money to fix it.
After a few hours last night, of studying, then fingering everything as it moved, the issues were pretty direct. As others noted, getting the drag link angle matched or as close to matched as the pan hard bar angle is key here.
This wasn't too hard. The generally advertised and accepted method of achieving this is to move the steering cross-link bar to the bottom of the Knuckle arm mounts.
So you are probably saying, wait a minute Tim, isn't the drag link mounted to the cross-link? Yup. it is. You need to remove it from the cross-link, and this is where you will need to drop some pennies because you'll want to get some longer (bent ends preferred) rod ends so you can make the drag link longer so it can reach the knuckle arm mount spot. The bent ends on the drag link will help a lot here as it reduced the angle of the drag link mounts. Once you lower the drag link to the top of the arm, the angle increases and this will start to bind the link ends and the balls. So the bent ends will address the bad angle and eliminate any binding by removing the stress from the greater angle, and get rid of any binding at the link ends and balls.
This opens the top of the knuckle arm area to move the drag link too. When you add longer drag link ends to extend its length to get it to mount on the top of the knuckle area, it makes the drag link angle very close to the pan hard angle. This is a great fix and only requires you to move the links around and a few longer rod ends. Same bolt and nut should work on both sides of the knuckles.
Many are putting the bolts in upside down (from the bottom up) so the pan head of the bolt is on the bottom. This will add clearance and reduce some hangup spots under the axle. I just mounted mine normally for now (nut on the bottom). Depending on rod end length, the end of the drag bar should be pretty close to 90* out from the servo horn gear. The closer to 90* you can get the link mount to the servo arm gear, the better performance you'll achieve here. So pay with some rod end lengths and try to make the drag link the right length, or within a few mm as much as possible.
There is another option for drag-link bars here. Use another brand's link.
I have these SSD kits here and one is a leafer now, so I used the s curved Panhard link, as the steering link was used on the leafer build. So I thought about trying it as a pan hard link on the Axe, but decided to use is as my drag link from the servo to the axle top. The S curve on the SSD introduces a much better link geometry. Added a long end and a short end (straights and stock) to the SSD link and installed it. This allows the steering to move fully from bind point of CVD to bind point of CVD and do it without much issue. Installing a metal Pan Hard mount on the axle will also help keep the front suspension more rigid, which will only add to the steering improvements as they won't flex under stress/tension, which always shows in steering radius as the suspension flexes.
After swapping to the SSD link (which is smaller diameter than the stock Axe link, but is Titanium, opposed to the aluminum, and about 10mm longer than the stock drag link) and getting the right link ends on the correct end of the link (lol say that 4 times fast) so it wasn't too short or too long, it installed on the servo horn where the horn was at almost 90* to the servo gear. This really helped remove any of the remaining bump steer throughout the travel.
You can compress either side of the front suspension, separately, equally, or other, and the only remaining bump steer I see is at full compression of the right side, as the axle shift is introduced, and the servo position doesn't change, they will fight against each other a bit.
So while I was not able to get rid of al the axle shift, it is minimized as much as it can be without a full redesign of the pan hard mounts, link and mounting positions. I'm happy with the end result of minimal axle shift it has now. And after the changes to the steering, getting the drag link angle basically matched with the SSD Link I used, I am very happy with almost no bump steer.
If you notice, the only thing I said you may need to get is a few bent rod ends, not angled, but 2 angled rod ends on the pan hard bar itself may help a little, as using them will add some length and needed end angle to reduce the bind on the link balls. An S curved pan hard with the right Geometry to clear the axle at full compression may really help. I didn't try my SSD Pan hard bar before Using it as the Steering drag link, but i may try it to see how it works out, and if it does improve the axle shift, buy one. Or maybe I'll just take some links that I have or some brake line and try to bend up a properly configured S curved Pan Hard bar if it proves to help reduce/eliminate the Axle shift.
Things of note...
Don't Shorten the Pan Hard ends too much. You'll need to find a happy medium between how much the axle is shifted while the right side is under full compression, and how much it pulls the axle when the suspension is fully unsprung.
I mentioned I originally removed about 3mm per side on the pan hard links.
last night I keep going until I went too far. Which I put on a different end that was slightly longer again, and that is where it is atm. I think I want to add a few mm back, so I need to put another link end on that is just a few mm longer than the one mounted at the axle right now.
BUT, I will wait to do that until I have received and installed the SSD Link Mounts. That flexing pan hard mount on the shock mount doesn't help either the axle shift or the steering issue at all. It probably even has a bit of an effect on the remaining bump steer it has. So once I get them and on, then I'll check it all out again, and see if a longer link end will still be needed.
I think it will, but its 'good enough for this redneck' for now. lol
Again, I'll get pics and take some vid of the changes with in a day or two. May be later this evening yet, but most likely tomorrow after I get back home.
So to fast summerize.
Yes, you can almost eliminate all the bump steer, but there will be some due to the pan hard design.
No you can not get rid of the axle shift without a big redesign. But you can make it livable and remove a fair bit of it, making it much better to drive.
I suspect once I have the SSD link/panhard mount installed, it will be better yet, Not totally gone, but fully livable and not that intrusive on the rocks.
I spent about 45 minutes today on the rocks. It held the lines much better. The nearly gone bump steer didn't get in the way or cause any problems.
The improved steering and turning was great, and will get better with the Solid pan hard mount on the axle.
So for the cost of a few short rod ends, or make your own, you can reduce and make bearable the axle shift. For the cost of a few bent rod ends, you can very much improve the bump steer and some of the overall steering issues by dropping the cross link to the bottom of the knuckle arm, and putting the drag link on the top of the link arm with a few longer link ends.
For all you RC Gen 8/Axe owners out there, who notice steering issues, and have found various semi fixes to the steering problems as well as the bump steer issues these rigs see, along with the front axle shift as the suspension compresses (limited improvements here due to layout and geometry which will take more attention to correct or improve) they also have, this thread should help you know whats a required solution, and what only seems like a solution.
For those that know me from days gone past, this won't be much new, but for those that have come since I got out nearly a decade ago, you may find this interesting, lol or not.
So. out of the box the front end works. Not great, but it does what it should, just not HOW it should. lol The bump steer was fairly significant, and some of the 'fixes' offered are good in that they address the correct issue, instead of something that doesn't but tries something to change the setup to work better, in some ways, tackling a minor issue, and in other masking or making the main issue worse.
I had a f-it night, and pulled out the Axe around 1:30 am and finally crashed about 6ish as the Sun was coming up.
First I'll address the axle shift.
If you look, as the front suspension compresses, the axle starts to shift to the right side (passenger). The more compression of the right shock the more shift introduced. However, the left side (Drivers) can compress fully up front, and it induces zero axle shift from what I could see. I studied the front end as it moved through its stages noting what/where/why was going on.
The simple answer is the pan hard setup. Ignoring the plastic axle panhard mount that flexes a bit, and needs to be addressed with an aluminum mount (a few options are out there, RedCats own link mounts, SSD's sets, & Chy-Na specials. I have the SSD in my cart atm), the design/layout/set-up of the pan hard introduces the shift. The reason its only the right side that does it is the pan hard mounts on the right side of the axle. If it was opposite and mounted on the left, then that side would be introducing the shift with the current setup.
Ealier, a month or so back, I posted about this, and to address it I started shortening the pan hard link ends. The problem is as the right side suspension compresses, the pan hard bar starts pushing the axle outward (passenger side) because of its length and position of the mounts.
By shortening the link ends a bit, it shortened the overall length of the panhard so when the left side compresses, the pan hard didn't shift the axle as much as it was a few mm shorter (about 5-6mm total, 3mm from each link end).
This helped, but the amount of shift was still quite long. I went ahead and tried to shorten some link ends further. But it didn't take long before the axle when unsprung started to pull on the left side, shifting the axle again. This is because I made the bar too short with the shortened ends. So there is a Sweet Spot on these rigs, and with its current setup, the best you can hope to improve. I'll get it sorted and post back how long each rod end is. Will also get a few angled rod ends just to see if they'll help any.
I am thinking a well formed S bend pan hard bar, and an angled end on the axle side may help more, but even then, without fully redesigning the mount locations, angles, pan hard bar, link end geometry, the best we are going to end up with is zero axle shift under left side compression, and some (a bit less than 1/4 inch maybe) shift under full right side suspension compression.
I'll grab some pics and detail what I did in the next post to improve the axle shift as best as it can be.
On to the steering issue and bump steer problem.
First the steering issue. This is a bit of a geometry/layout issue but is correctable without the need for spending too much money to fix it.
After a few hours last night, of studying, then fingering everything as it moved, the issues were pretty direct. As others noted, getting the drag link angle matched or as close to matched as the pan hard bar angle is key here.
This wasn't too hard. The generally advertised and accepted method of achieving this is to move the steering cross-link bar to the bottom of the Knuckle arm mounts.
So you are probably saying, wait a minute Tim, isn't the drag link mounted to the cross-link? Yup. it is. You need to remove it from the cross-link, and this is where you will need to drop some pennies because you'll want to get some longer (bent ends preferred) rod ends so you can make the drag link longer so it can reach the knuckle arm mount spot. The bent ends on the drag link will help a lot here as it reduced the angle of the drag link mounts. Once you lower the drag link to the top of the arm, the angle increases and this will start to bind the link ends and the balls. So the bent ends will address the bad angle and eliminate any binding by removing the stress from the greater angle, and get rid of any binding at the link ends and balls.
This opens the top of the knuckle arm area to move the drag link too. When you add longer drag link ends to extend its length to get it to mount on the top of the knuckle area, it makes the drag link angle very close to the pan hard angle. This is a great fix and only requires you to move the links around and a few longer rod ends. Same bolt and nut should work on both sides of the knuckles.
Many are putting the bolts in upside down (from the bottom up) so the pan head of the bolt is on the bottom. This will add clearance and reduce some hangup spots under the axle. I just mounted mine normally for now (nut on the bottom). Depending on rod end length, the end of the drag bar should be pretty close to 90* out from the servo horn gear. The closer to 90* you can get the link mount to the servo arm gear, the better performance you'll achieve here. So pay with some rod end lengths and try to make the drag link the right length, or within a few mm as much as possible.
There is another option for drag-link bars here. Use another brand's link.
I have these SSD kits here and one is a leafer now, so I used the s curved Panhard link, as the steering link was used on the leafer build. So I thought about trying it as a pan hard link on the Axe, but decided to use is as my drag link from the servo to the axle top. The S curve on the SSD introduces a much better link geometry. Added a long end and a short end (straights and stock) to the SSD link and installed it. This allows the steering to move fully from bind point of CVD to bind point of CVD and do it without much issue. Installing a metal Pan Hard mount on the axle will also help keep the front suspension more rigid, which will only add to the steering improvements as they won't flex under stress/tension, which always shows in steering radius as the suspension flexes.
After swapping to the SSD link (which is smaller diameter than the stock Axe link, but is Titanium, opposed to the aluminum, and about 10mm longer than the stock drag link) and getting the right link ends on the correct end of the link (lol say that 4 times fast) so it wasn't too short or too long, it installed on the servo horn where the horn was at almost 90* to the servo gear. This really helped remove any of the remaining bump steer throughout the travel.
You can compress either side of the front suspension, separately, equally, or other, and the only remaining bump steer I see is at full compression of the right side, as the axle shift is introduced, and the servo position doesn't change, they will fight against each other a bit.
So while I was not able to get rid of al the axle shift, it is minimized as much as it can be without a full redesign of the pan hard mounts, link and mounting positions. I'm happy with the end result of minimal axle shift it has now. And after the changes to the steering, getting the drag link angle basically matched with the SSD Link I used, I am very happy with almost no bump steer.
If you notice, the only thing I said you may need to get is a few bent rod ends, not angled, but 2 angled rod ends on the pan hard bar itself may help a little, as using them will add some length and needed end angle to reduce the bind on the link balls. An S curved pan hard with the right Geometry to clear the axle at full compression may really help. I didn't try my SSD Pan hard bar before Using it as the Steering drag link, but i may try it to see how it works out, and if it does improve the axle shift, buy one. Or maybe I'll just take some links that I have or some brake line and try to bend up a properly configured S curved Pan Hard bar if it proves to help reduce/eliminate the Axle shift.
Things of note...
Don't Shorten the Pan Hard ends too much. You'll need to find a happy medium between how much the axle is shifted while the right side is under full compression, and how much it pulls the axle when the suspension is fully unsprung.
I mentioned I originally removed about 3mm per side on the pan hard links.
last night I keep going until I went too far. Which I put on a different end that was slightly longer again, and that is where it is atm. I think I want to add a few mm back, so I need to put another link end on that is just a few mm longer than the one mounted at the axle right now.
BUT, I will wait to do that until I have received and installed the SSD Link Mounts. That flexing pan hard mount on the shock mount doesn't help either the axle shift or the steering issue at all. It probably even has a bit of an effect on the remaining bump steer it has. So once I get them and on, then I'll check it all out again, and see if a longer link end will still be needed.
I think it will, but its 'good enough for this redneck' for now. lol
Again, I'll get pics and take some vid of the changes with in a day or two. May be later this evening yet, but most likely tomorrow after I get back home.
So to fast summerize.
Yes, you can almost eliminate all the bump steer, but there will be some due to the pan hard design.
No you can not get rid of the axle shift without a big redesign. But you can make it livable and remove a fair bit of it, making it much better to drive.
I suspect once I have the SSD link/panhard mount installed, it will be better yet, Not totally gone, but fully livable and not that intrusive on the rocks.
I spent about 45 minutes today on the rocks. It held the lines much better. The nearly gone bump steer didn't get in the way or cause any problems.
The improved steering and turning was great, and will get better with the Solid pan hard mount on the axle.
So for the cost of a few short rod ends, or make your own, you can reduce and make bearable the axle shift. For the cost of a few bent rod ends, you can very much improve the bump steer and some of the overall steering issues by dropping the cross link to the bottom of the knuckle arm, and putting the drag link on the top of the link arm with a few longer link ends.
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