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  1. #1
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    Suspension Tuning

    I'm having a hard time with this. My e-maxx came with what I believe to be the ultra shocks with progressive white springs. I don't know the spring rate range but I believe it to be a transition from 3 ppi to 7 ppi. When I use the preload spacers, it pretty much removes the lower spring rate range so my springs become 7 ppi. I'm trying to determine the spring rate needed for what I want to do.

    My desire is to go fast (as fast as possible) on non-smooth surfaces like a dirt road that I would normally ride atv's on or something. So basically there will be a small bump here and there. My theory is, the faster I go, the harder I will hit those small bumps and the faster I will need the shock to recover, so in turn I would need a higher spring rate. How much, I do not know yet. I was going to go to the hobby store to buy another set of springs stiffer than 7 ppi just to try it out. They didn't have any.

    My dilemma is that at such a high spring rate, it puts my ride height up there, not max, but very close to max. I want my arms to be able to travel both up and down so I really want to lower my ride height some from where it's at but I can't do that unless I get shorter shocks... Currently, I'm on the far inside on the shock tower and the far outside on the A-arms.

    What are yall's experiences for going fast on surfaces that are not paved? Please don't answer if all you do is drive on concrete.

    edit: Also, don't come back and say "I use the green ones here and the blue ones here". I'm an engineer, I want technical data. Give me numbers with units please. Thanks.
    Last edited by jmwman; 05-18-2015 at 05:00 PM.

  2. #2
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    So I am not an engineer and can not give you numbers and hard technical data. What I do know is you want your bottom A-Arms to run parallel to the ground, Shorter shocks will not increase your travel, and stiffer springs will make your truck run much like a rock skipping across the water and not raise your ride height. I do own a set of 12ppi progressive springs that are horrible offroad but work fantastic on a well groomed track. For offroad and bump absorption the 3/7/3 progressive springs work quite well.

    You can further tune your shocks by using different weight silicone shock oil. Believe the stock shock oil weight is 35W. Some folks opt for 40-50W oil some go higher as much as 70W, To run the higher weight oil 50-70+ it is recommended to install aluminum shock caps. You can also change your shock pistons you should have the two hole pistons installed from the factory. You can change those out for 1, 2, 3,or 4 hole pistons, slower(less holes) or faster(more holes). You can also modify the holes by enlarging them slightly for faster oil transfer.

    You can also go to aftermarket shocks some prefer the Ofna 1/8 scale Hyper 7 front buggy shocks, others prefer the Proline Powerstroke shocks, while some swear by the Traxxas big bore shocks. There are so many combinations and manufactures it would be hard to list them all.

    Suspension tuning is a black art that is mostly trial and error, what works for me might not work for the other guy. It's all about personal preference, driving style, and terrain.
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  3. #3
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    12 ppi is 71% more than 7 ppi. I'm interested in trying out 8-10 ppi...

  4. #4
    RC Turnbuckle Jr. Wildman4910's Avatar
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    Have a look at the AE MGT springs, they come in rates 4.40, 5.10, 5.95, 6.90lbs.

    If you decide you want to limit the shock travel, you can put nylon spacers on the shock shaft under the piston.
    This will shorten the overall length of the shock and the travel.
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  5. #5
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    I installed 1/8 scale Mugen MBX6T rear shocks (used FLM towers) at all four corners (one shock per wheel). You have to use steel CVD shafts to make the needed clearance but otherwise they install directly using the highest position on the towers. the only change I made with the shocks was to install some stiffer springs. With both batteries installed and otherwise ready to run, the truck sits on the ground with the A-arms slightly above horizontal. Pick the truck up and the arms will droop all the way down. Full up travel is also present. I still need to experiment with the oil weight but I am very happy with the results. Handle is 100% improved over extremely rough surfaces (the local track is very eroded) and it handles the biggest jumps with ease. I know some folks use front truggy shocks but the rears are working great for me.
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  6. #6
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    Quote Originally Posted by rock-rod View Post
    I installed 1/8 scale Mugen MBX6T rear shocks (used FLM towers) at all four corners (one shock per wheel). You have to use steel CVD shafts to make the needed clearance but otherwise they install directly using the highest position on the towers. the only change I made with the shocks was to install some stiffer springs. With both batteries installed and otherwise ready to run, the truck sits on the ground with the A-arms slightly above horizontal. Pick the truck up and the arms will droop all the way down. Full up travel is also present. I still need to experiment with the oil weight but I am very happy with the results. Handle is 100% improved over extremely rough surfaces (the local track is very eroded) and it handles the biggest jumps with ease. I know some folks use front truggy shocks but the rears are working great for me.
    I like the adjust-ability of the FLM shock towers... I bought one RPM shock tower already and it has one shock mounting position. I might choose one for front and the other for the back. I hate the price tag of the FLM tower... You mentioned you installed stiffer springs, do you recall the spring rate? This is really key info as it ties in with vehicle weight, speed, impact against surfaces, rate of responsiveness to rate of surface changes, etc, etc.

  7. #7
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    I am currently experimenting with the Mugen 1.6/9.75 springs at all four corners and using the threaded adjusters to tune it.
    Mugen rates the springs on wire thickness and coil wraps. 1.6 is the wire thickness and 9.75 is the number of coils. the wire thickness comes in two styles identified by color (silver and black). the 1.6 are the black springs and is the thicker wire. the lower the number for coil wraps, the stiffer the spring. The 9.75 is consider 'very hard'.

    here's my thread on the chassis swap. you can see the shocks in some of the pics.

    https://traxxas.com/forums/showthrea...-Chassis-Build

    the trick with using these shocks is to also use the mugen shock standoffs. The FLM ones don't work very well and were constantly coming loose.
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  8. #8
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    What I really want is to have really stiff springs, and my shocks not fully extended when my truck is just sitting there. So far the only sure way of doing that is by increasing the weight of the truck. Has anybody ever looked into increasing the weight? Did they notice any performance changes?

  9. #9
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    I took the e-maxx down to my folks place where there's a lot of rugged terrain. As soon as I started driving around I immediately needed to take all my preloads off. Remember, I have the ultra shocks with the 3-7 progressive springs. I had preloads on all 8 shocks and that essentially removed a portion of the bottom end of the spring rate so I might effectively had maybe a spring rate of 5-7 or even 6-7 ppi. This was too stiff for as lightweight the truck is and as I was impacting each change in contour of the trail I was running on the shocks had trouble compressing. Unfortunately, I didn't get to spend a lot of time testing, maybe 15 minutes of my Memorial Day weekend. So in conclusion, I "might" need really stiff springs for high jumps and hard landings, but I definitely don't need stiff springs even when running 45-50 mph on caliche with several washouts.

  10. #10
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    I did a little suspension test. I had a bunch of zip ties lying around so I grabbed two of them and I looped each one of them around the middle portion of each front upper arm and then around the closest shock tower. I snugged it down, not sure how much by, this is up to yall as far as how much, obviously the more you snug it down the more you limit your travel. Anyways, I only did the front for 1 reason, when you accelerate the rear of the vehicle already sits and the front raises up, I wanted to try limiting how much the front raises by. Well, when I accelerate the car still pops wheelies fairly easily, so it didn't have the effect I was hoping for. However, I noticed a huge amount of difference in the high speed turns. The truck simply did not want to roll over when I went into turns at a high rate of speed. Obviously, if I try and little harder then I might be able to do it, my goal of course is not to do it but come close to doing it, basically push the truck to its limits.

    Another thing that the truck does that contributes to the chances of a wheelie is the ballooning of the tires. Are there tires out there that don't balloon up?

  11. #11
    RC Turnbuckle Jr. Wildman4910's Avatar
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    Not really, to help prevent ballooning you need to tape and balance the tires.

    You can also limit the shock travel by putting some nylon spacers under the shock piston.
    Look out for the tree/crunch!

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  12. #12
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    Yea, I've seen posts and videos where people mentioned the nylon spacer trick. Just seems like a more permanent solution. Also, there's no adjustability, I wish I could find a way where you can limit shock travel "on the fly" meaning you can quickly make adjustments depending on the terrain you are about to drive on. Has anyone ever seen anything like this? Sorta like the preloads which allow you to quickly stiffen the springs on the fly.

    As far as the nylon spacers, have a lot of people done this and if so, is there a preferred spacer length that's worked for most people?

  13. #13
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    Well, I took my e-maxx out to a large parking lot today. I now need a new body... It doesn't matter how slow I accelerate, the truck lifts off everytime. Is this normal when driving on concrete? It doesn't even wheelie, the wheelie bar never even makes contact with the concrete. Then when I get on the grass it's easier to keep all four tires on the ground..... Any input would be much appreciated.

  14. #14
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    Did you try adding some punch control or changing the throttle curve? You could also try a center diff or perhaps adding weight to the front.
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  15. #15
    RC Turnbuckle Jr. Wildman4910's Avatar
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    You just have to try it out different lengths till you find the ride height you want.
    It is a pain but once done your good to go for that setup.
    If your running stock ultra shocks, get a spare set off ebay, have one set for the street and one set setup for off road.
    Look out for the tree/crunch!

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  16. #16
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    Quote Originally Posted by grumpy42 View Post
    Did you try adding some punch control or changing the throttle curve? You could also try a center diff or perhaps adding weight to the front.
    I'm assuming you are referring to going to the Traxxas link app and increasing the throttle sensitivity right? Yes, right now I'm at the default 0.0% throttle sensitivity, BUT, I am still accelerating super slow so I have a hard time believing that by increasing this sensitivity the truck will do any better. I'll try it out though. Question: you mentioned punch control and throttle curve, are these the same thing or two separate things? Which is which, can you explain each one?

    I have mixed feelings about changing weight around the vehicle. Coming from my background, it will make certain design decisions of the stock vehicle unusable. It's kind of like a domino effect, you change one thing and it has its repercussions on something else.

  17. #17
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    Quote Originally Posted by Wildman4910 View Post
    You just have to try it out different lengths till you find the ride height you want.
    It is a pain but once done your good to go for that setup.
    If your running stock ultra shocks, get a spare set off ebay, have one set for the street and one set setup for off road.
    Change out shocks when you change terrains, boy that's a pain in the butt, lol. They need to come out with quick disconnect options, maybe something that snaps on and off, that would be awesome.

    I don't really like street driving, off road is way more fun, but I don't really know of any place to take it to that isn't a super far drive. Wish there was something within just a few miles that I could go to. Like a construction site or something that has a big ol pile of dirt, lol.

    As far as street driving is concerned though, I've seen in a few Youtube videos where people use lower profile tires for street driving. Are there any low profile tire options that have the same diameter as the 6.3" stock tire? I kind of feel like the stock tires are part of the problem, when you get up there in speed the tires become so big and lifts the truck so high up off the ground.

    Changing tires would be easier than changing shocks. If I did change the shocks, what shock setups (oil weight and spring rate) do you recommend for off and on road?

    Oh, back to grumpy, as for adding weight to the front, I could technically shift the weight forward on the truck slightly because the battery is smaller than the compartment. My problem is the battery I'm using is the Onyx 3S 5000 mAh and it doesn't really fit in the compartment height wise even if I use the 28 mm battery retainer clips. I have to force the battery to fit by centering it in the middle of the compartment and forcing the battery clips (slight gradual bend over the battery) to clip on. Are there battery retainer clips that are taller than the 28 mm clips?

  18. #18
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    easy way to limit travel:

    http://maxxparts.forumactif.org/t18-suspension-limiters

    Just adjust the cable length as needed. the mugen shocks I am using have a ridiculous about of wheel travel so if I am going to be running on the street, i snug them down to reduce the amount of droop and effective lower the chassis down. much easier than swapping to shorter shocks.
    I have an RC problem...

  19. #19
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    Oh, real quick, where can I get a new body? While I would love to replace my destroyed stock body with an identical one, I can't warrant the $35 for a replacement to be a good deal.

  20. #20
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    Quote Originally Posted by jmwman View Post
    I'm assuming you are referring to going to the Traxxas link app and increasing the throttle sensitivity right? Yes, right now I'm at the default 0.0% throttle sensitivity, BUT, I am still accelerating super slow so I have a hard time believing that by increasing this sensitivity the truck will do any better. I'll try it out though. Question: you mentioned punch control and throttle curve, are these the same thing or two separate things? Which is which, can you explain each one?
    I was actually referring to ESC setting (via Castle Link). Punch control essentially controls the power that the motor can draw limiting the acceleration. So, with 0% punch control, standing backflips are easy, but with 100% punch control it is unlikely you'd be able to pop a wheelie even if you wanted to.

    I am not that familiar with the Traxxas link app, but 0.0% sensitivity probably represents a linear throttle curve. Increasing/decreasing the sensitivity (positive/negative percentages) will increase/decreasing the sensitivity of the throttle near neutral. So, with a linear curve 50%thr=50%pwr but a reduced sensitivity curve may result in 50%thr=25%pwr.
    Here is throttle curve meant to reduce throttle sensitivity (from Castle Link)



    If your ultimate goal is to keep the wheels on the ground during hard acceleration, your best bet may be a center diff. I have not used it but the 5614 center diff is a direct drop in.
    http://www.amazon.com/Traxxas-Center...&keywords=5614

    Quote Originally Posted by jmwman View Post
    Oh, real quick, where can I get a new body? While I would love to replace my destroyed stock body with an identical one, I can't warrant the $35 for a replacement to be a good deal.
    I think that the only places to get the stock body from are those that part out retail vehicles.
    http://www.dollarhobbyz.com/catalog/...black-red-body
    http://www.dollarhobbyz.com/catalog/...lue-black-body
    http://www.dollarhobbyz.com/catalog/...hless-red-body
    Proud member of the red card club.

  21. #21
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    So far, it seems from my experience that a 50% sensitivity would probably be linear. 0.0% which is default seems like it hits 100% pwr at maybe 10% throttle and then when I put it on 100% sensitivity it doesn't get to 100% power until I give it 100% throttle.

    Basically, the 100% sensitivity setting looks a lot like the graph depicted in your post. I'll have to try out the 50% sensitivity setting to see how that feels. 100% is too much that I would just prefer to stay at 0%.

    Oh, and the bodies, looks like they are on sale and they increased the price to more than what Traxxas sells them for, lol.

  22. #22
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    I took my EMBE out to a local construction site. The terrain is nothing like the farm/ranch. Definitely cannot go even half speed. The clumps are huge. Of course, I made the mistake of not making adjustments to my suspension before going out there. I still had the shocks on the outer position on the arms and preloaded for backyard driving.

    I'm curious, when you guys head out to the construction yards (if you do), what position do you put the shocks at on the shock tower and arms?

  23. #23
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    Quote Originally Posted by grumpy42 View Post
    If your ultimate goal is to keep the wheels on the ground during hard acceleration, your best bet may be a center diff. I have not used it but the 5614 center diff is a direct drop in.
    http://www.amazon.com/Traxxas-Center...&keywords=5614

    So, if I understand this correctly, the way the center differential works is, if the front tires leave the ground, the back tires lose power and all power is transferred to the front until it remakes contact with the ground. Is that correct? Basically in similar fashion that the rear or front tires work in pairs, if the left leaves the ground, the opposite side slips and all power is transferred the the tire that's in the air.

    As long as all four tires are on the ground, you don't lose power at all, but if you try to drive aggressively and any tires attempts to leave the ground, then you will lose some performance. Interesting.

  24. #24
    RC Qualifier ausprime's Avatar
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    You need a set of "discontinued" powerstrokes!
    I can set them up so the top spring is really soft, while the bottom spring is really stiff.
    This will make the weight of your truck, lower the top spring. And the bottom spring will absorb the big hits
    And when you hit the little bumps at high speed, the top spring will do all the work.
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  25. #25
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    If they were discontinued and I can't get a set, is something else that's similar available out there?

    I just got back from the construction site again. This time I took my 3906 e-maxx fully stock with the shock positions setup for maximum travel and softness (in on arm and out on tower). I have it setup that way already mainly because I was interested in seeing it drive around a little bit on some rocks in my backyard the other day and found it's quite fun to drive with that plush suspension. Anyways, I did notice a boost in performance when driving over this one area at the construction site where it's super rugged and the dirt is super clumpy. Some of the clods are as big as my foot but most are as big as my fist. Still can't drive through that at full speed of course, but with the 3906 using a 2S Lipo and in low gear it goes quite well at half speed. Those old chevron tires seem to be a bit too hard for that kind of terrain, I feel like I need the soft 3908 stock tires on there. I guess if I ever upgrade the 3908 tires to proline then I'll switch the old stock ones to the 3906 along with the 17 mm hubs.

    I don't like the idea of having to change the shock positions everytime I go to a new place. Since the screws screw in directly to the plastic holes in the tower and the arms, I feel like each time you unscrew and screw it in again the hole will just get bigger and bigger each time.

    Hey, on those shocks above, can you adjust the top and bottom springs "individually" or is it a combined adjustment?

  26. #26
    RC Qualifier ausprime's Avatar
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    Combined.
    The bottom spring shouldn't engage, until the top spring has fully compressed.
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  27. #27
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    Quote Originally Posted by ausprime View Post
    Combined.
    The bottom spring shouldn't engage, until the top spring has fully compressed.
    So, in other words, if you preload, it removes the top spring. That's similar to the progressive white springs on my 3908. The difference is that the progressive rate springs are a "range" of spring rates and the power stroke are dual spring rate. I will have to try out my progressive rate springs out there with the preloads completely removed. I should have done it the first time but I just didn't think about it.

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