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Thread: Suspension issue, rear turning when flexed out

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Old 11-02-2009, 10:08 PM   #1
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Default Suspension issue, rear turning when flexed out

So, what would make it so that if I flex the front one way, one of the rear tires travels forward an inh and a half? It seems like that is an excessive amount.

I was told if the upper and lower links were parallel, when lookig from the side, it would reduce it. I moved my upper links up a hole to make them more parallel. It didn't seem to do anything.

Then I removed the spacers from the axle mounts on the upper links to make it more triangular and that seemed to help more. What's the real scientific explanation? Thanks!
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Old 11-03-2009, 01:18 AM   #2
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Pics and rig info would help.
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Old 11-03-2009, 08:59 AM   #3
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yes...pics to understand fully....im confused.lol
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Old 11-03-2009, 10:27 AM   #4
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Here's some pics, it might be hard to tell still so I drew a quick top view.

Here is the car just sitting. You can see the angle of the uppers and lowers in relation to eachother. The red lines show the initial alignment of the axles, parallel to eachother.


Here it is when it flexes:


The yellow line shows the angle the axle started at, and the red line shows the angle it moved to when I flexed the front passenger tire up.

Here's the top view to further demonstrate. The rear effectively steers one way or the other when the car flexes:


I assume some of this is normal, but I don't remember my previous car doing it so much.

Here is a top view of where the links are:


The top view view makes the tires look like they're all towing out, but that's just the picture.
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Old 11-03-2009, 10:28 AM   #5
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Try making your uppers parallel with each other, when viewed from above.
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Old 11-03-2009, 10:31 AM   #6
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That was my initial thought! But the three guys I asked said to keep them all triangulated, actually the remove my upper link axle mount spacers to make them MORE than they were.

I will try it and report back.
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Old 11-03-2009, 10:33 AM   #7
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You will want to lower your roll center so that the lowers don't yank the axle when it articulates. If I recall correctly, putting more bias to the lower triangulation will do this.
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Old 11-03-2009, 10:42 AM   #8
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Yes, Move the lowers in on the chassis.
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Old 11-03-2009, 11:13 AM   #9
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Definitely helped. I spaced the uppers out at the axle and in on the chassis and the rear wheel movement was cut in half. Nice.

However, I don't know if I like so many spacers. Does it matter? Doesn't that put a lot of stress on the upper link axle mount?

I would rather inboard the lowers and remove some of the upper spacers, which I will probably try a little later. The only problem with that is the clearance of the gearbox/motors :-/

If I space out the lowers at the axle I can probably inboard them at the chassis. The main problem is that I already get tire rub in the front. I'll probably go a little wider with the hex hubs on the front anyways so it'll probably work out. I'll have a .25" wider in the front, and move the lower links, and the rub should work out to be about the same.

Thanks. Now at least I know how to fix it

Last edited by JTTG; 11-03-2009 at 11:20 AM.
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Old 11-03-2009, 12:07 PM   #10
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I am able to space out the lower links at the rear axle, then inboard them on the chassis. Everything barely clears.

I tried to do the same to the front, with the straight links, and it clears on the motor side, but not on the gearbox side. Is it bad to have the rear lowers inboarded and the front lowers outboarded at the chassis? Or would it be better to inboard them all, and space out the fronts at the axle even more?

With the bent lowers I can angle them out slightly to make them clear. It's within a few mm but it clears fine. It's just because the fronts are straight that makes them not work.
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Old 11-03-2009, 12:12 PM   #11
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Just drive it and see how you like it before imploding your head with thoughts

I wouldn't start messing with the lowers until you know how it handles with the uppers changed.
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Old 11-03-2009, 01:05 PM   #12
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Therein lies the problem...it's not even running yet lol. I've been waiting on the dig, that should arrive today finally, for 2 weeks.

I spaced out the front lowers a tiny bit more and it clears to inboard all the lower chassis mounts, which I think is the best starting point. I will leave it as is until it's running.

It's at just under 12" wheel base and 3 3/4" clearance so...that'll need to be changed for sure.
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Old 11-03-2009, 03:03 PM   #13
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Look at your links then look at the losi links, thats the way you want to make them you can parralell the uppers but you want the lowers triangulated as close as you can get them by the skid and as far apart at the axle as you can get them with everything wtill working and not binding.
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Old 11-03-2009, 03:23 PM   #14
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Yep! Thanks for the info everyone. Once I played around with it, especially after inboarding the lowers on the chassis, it was easy to see why the car did what it did. Learn something new every day.
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