Shortened Wheelbase

[jimjam]

I just thought I'd share my wheelbase shortening experience.



Prior to doing this I couldn't find any description on how to do it or, how difficult it was. If it's out there I apologize for the duplication but I couldn't find it.

First off, it is quite a simple process with minimal permanent alteration. The only commitments you have to make is to the rear driveshaft and four (of eight total), four links. Both will have to be shortened. Both are no big deal to replace if you want to go back.

*Also, it should be noted that I am using short barrel springs - for the differences dimensionally, as result of the rear end sitting a little farther below, the chassis.

As you can see, I have moved the upper, rear spring/canti mount forward two holes in the chassis. This equals exactly 20mm (I believe, it's been a month since I did it).



There is a screw in the way that mounts the plastic bed (in between chassis) where you mount the electronics. Take that screw out (1 on each side) and I believe the screw in the spring/canti mount is long enough to go through canti mount to the nut already embedded in the plastic bed. The other two screws on the canti mount will use lock nuts and bolt directly to the chassis. It's pretty simple and clear once you begin to do it.

Now you'll have to shorten the four links. I went with 18mm for all four links, just to be cautious and it works perfect. I know 20mm on the canti mount, why 18 on the links. When I looked a how this length would leave the orientation of the bottom shock mount it looked nice and level so I went with it. I have also moved my link mounts all over the place from the original setup, more on that later. The best news here is that when you cut the links if, you will split the difference and cut on both ends (I did 9mm from both ends) you still have threads on either end for the ball connector theaded stud to go right back in w/o needing to find an itty bitty tap to replace the threads. I'm pretty sure the links are not threaded all the way through. DON'T CUT YOUR DRIVESHAFT YET!

Because moving the rear end up 20mm changes the drive shaft angle beyond usable, the motor/trans will need to be moved forward. Luckily, it seems that some parts where designed for alternate applications.



Plenty of options here (above). I moved it all up to the next set of holes (forward). All four holes line up just perfect. Of course, this will require a shorter front drive shaft. I believe, the rear shaft fits w/o modification. You can now, also shorten your rear shaft (which ever shaft you want to shorten). If I'm not mistaken, this also moves a little more weight toward the front which is good, right?

*Something to consider; the original drive shafts work just fine w/o binding in any position but, as I have learned my Junfac shafts will bind (on the pins) when the suspension is extended all the way. They won't bind in any position under crawling conditions except if say, the truck hangs on the motor plate leaving both front or rear wheels dangling, not touching anything. Since that is a condition that will occur I'll be continuing my search for a drive shaft that works, any ideas? I just wanted to share my experience in this area in case it helps.

The last part of the shortening you've certainly recognized by now. That outer arm (top shock mount) on the link shaft (canti) is bent inward, hitting the chassis. It's a simple as removing this arm, flip it, put back on, see below.



If needed, you can use a shim between the lower end of the shock and mount, below.



Also, in the above pic you can see that I've swapped the "ball connector nut" with the "ball collar" connector, originally mounted (as per instructions) on the servo bed. As by the instructions, you have a "nut" style ball connector at the center connection points. This position requires the link attach at a greater angle than the "nut" style connector freely gives. At least on mine there was no room for the links to move further in an outward direction. I don't think this thing was intentionally designed to control the suspension by slightly binding on the limits of the ball connectors where they mount in the center (motor/trans area). Also, the links, in front mainly, need more of a shim to keep them from hitting the sides as they exit their center mounts. This increases the problem from the limits of the ball connectors even more. Luckily, the "ball collar" connectors have a little more freedom of movement. The swap works fine because the ball connections on the servo bed and rearend don't require as much freedom to move. My suspension is more freely moving than before. Wherever you get them I would replace these inner ball connections with a free-er design and shim the inner link connection points so they clear obstructions.



The best result of all from the shorter wheelbase is a tighter steering radius. It is seriously more friendly to drive. I can actually drive the house without having to stop and back up to complete every turn. And, with shortened four links and all, I have lost zero travel in the rear suspension. In fact, I've actually gained a little, for other reasons. I'm really happy with it. This is my first experience in building r/c anything so, if I've confused anyone with bad terminology or anything just ask me!

Oh yeah, someone asked about my body mount setup. It's cheesy but, I'll put it up in a few days.

[rabfan]

Nice! I actually just did something similar to mine but used some shorter links I had laying around....mine are different lengths though which cause some changing axle angles during compression but seems to work well anyway. I like the look of the Landcruiser body way better with the shortened wheelbase.
I bought some key stock and plan to make a telescoping shortened rear driveshaft for mine. I'll let you know how it goes.
RJ

[jimjam]

Originally Posted by rabfan

Nice! I actually just did something similar to mine but used some shorter links I had laying around....mine are different lengths though which cause some changing axle angles during compression but seems to work well anyway. I like the look of the Landcruiser body way better with the shortened wheelbase.
I bought some key stock and plan to make a telescoping shortened rear driveshaft for mine. I'll let you know how it goes.
RJ

I'll probably experiment with different length links too. My suspension is maybe too smooth, idk. The travel is just so good as is.

[cydog510]

looks way better shorter with the fj body, good job.

[.bg.]

Is it noticeably less stable?
I know that's not a huge wb change, but it'd be interesting if you could tell any difference.

[jimjam]

Originally Posted by .bg.

Is it noticeably less stable?
I know that's not a huge wb change, but it'd be interesting if you could tell any difference.

I was expecting to but, I haven't really, yet. I have actually only been over one small, pile of rocks since the last reduction. Of course, the difference has been less dramatic since I shortened it 10cm at a time. My front wheels also wheigh in at 9.4oz. Turning radius alone makes it worth it!

[ugly duck]

Originally Posted by jimjam

the difference has been less dramatic since I shortened it 10cm at a time

I'd expect 10 cm to be a pretty severe change on a truck with a wheelbase of less than 30cm.

[jimjam]

Originally Posted by ugly duck

I'd expect 10 cm to be a pretty severe change on a truck with a wheelbase of less than 30cm.

I really haven't been on any terrain that pushed this aspect of performance. I had also just barely finished the original build (of my cr-01 and my only crawler and rc car for that matter(!)), before I began shortening. To me, it's an acceptable compromise for the appearance. I'd have been more concerned if it affected the suspension travel.

I wish I would've at least lifted the front end off the ground until it tipped and measured the height of say, the chassis (front end) before and after for comparison. I could measure the "tip" now if, anybody wanted to know. Of course it wouldn't be relevant with all the differences between vehicles.

[ugly duck]

I'm just sayin'... 10 cm is 4 inches. I don't think you shortened it that much.

[jimjam]

Originally Posted by ugly duck

I'm just sayin'... 10 cm is 4 inches. I don't think you shortened it that much.

Actually, I don't think I mentioned 10"cm" until you planted it in my brain.

[ugly duck]

LOL, okay, so where'd I get the original quote from?

Never mind, just picking on ya.

[jimjam]

Originally Posted by jimjam

I was expecting to but, I haven't really, yet. I have actually only been over one small, pile of rocks since the last reduction. Of course, the difference has been less dramatic since I shortened it 10cm at a time. My front wheels also wheigh in at 9.4oz. Turning radius alone makes it worth it!

OOPS!

[australiancrawler]

Originally Posted by ugly duck

LOL, okay, so where'd I get the original quote from?

Never mind, just picking on ya.

Obviously the dude meant 10mm not 10cm.

[ugly duck]

Obviously.

[jimjam]

[IMG][/IMG]


This pic would have given a better perspective if it was aligned with the rear of the truck.

Just an update on a couple of refinements to my wheelbase shortening efforts. The height adjustment on the back body post was a little high. It doesn't show well in my pics here (above) but, it looked a little jacked up and unnecessarily high. While at it I decided the front had room to give up with the wheel just hitting the body so, it was dropped 1 hole, the rear 2.

This had the additional element of highlighting the position of the rear wheel to the wheel well. So, it was shortened an additional 2mm. I am still satisfied with the climbing angle limits I get but, most of all, I swear I could actually notice even this minor improvement in the turning radius. That fact alone has made the effort totally worth it.

***Oh yeah, added the bent links. A definite increase in capability. They do look good enough I guess, to justify the slightly stupid expense. Fronts weren't altered at all. Rears worked out by taking from both ends of the link and the ball connectors on both ends. One more note, this 20mm is as much as the u-joints (stock, Traxxas metal) will give!

[DRW-FJ40]

Hey JimJam, don't know if you are still following this but I've always wanted to fix the wheelbase on my FJ Cr01 but out of lazyness, never have. Well, I got some RoK Lox on OEM steel wagon wheel beadlocks. They look great & perform well but the rear hit the body very easily because they are so much larger than the stock tires.

Anyway, I fell back on your thread for a description of the operation. I followed you up till you switched to bent links. How did you modify the bent links? they look cast in the pictures, do you cut 9mm off either end the same way you cut standard links? is it easier to use the bent or standard links with this mod?

Reason I ask is I bought a box of parts on ebay a while back & it had one set of bent links. I didn't give it much thought at the time & just threw them in a box somewhere. But if they will work better, I'll buy another set for the front & run with the bent links.

[DRW-FJ40]

I just googled a pic of the bent links & all makes a little more sense now. (I don't have the links in front of me & never really looked at them that close). It sounds like you removed some of the aluminum link end and some of the plastic ball joint link. I think I'll procede along those lines anyway. Wish me luck.

[jimjam]

Originally Posted by DRW-FJ40

Hey JimJam, don't know if you are still following this but I've always wanted to fix the wheelbase on my FJ Cr01 but out of lazyness, never have. Well, I got some RoK Lox on OEM steel wagon wheel beadlocks. They look great & perform well but the rear hit the body very easily because they are so much larger than the stock tires.

Anyway, I fell back on your thread for a description of the operation. I followed you up till you switched to bent links. How did you modify the bent links? they look cast in the pictures, do you cut 9mm off either end the same way you cut standard links? is it easier to use the bent or standard links with this mod?

Reason I ask is I bought a box of parts on ebay a while back & it had one set of bent links. I didn't give it much thought at the time & just threw them in a box somewhere. But if they will work better, I'll buy another set for the front & run with the bent links.

Hey, sorry I haven't checked in a while. I usually have any thread I'm involved in marked to send an email on any activity.

The bent links do not necessarily work better but they do have a noticible improvement in clearance and they look cool. I actually divided it all up between the links and ball ends (connectors). So, if I took 10mm from each end, I divided that at 5mm off for each link end and 5mm from the ball connector at each end. There just isn't enough meat on the links to take it all from the link itself but, the connectors can spare this amount and still retain the necessary strength.

Rather than an exact number (in mm) of material to remove for a particular distance of the overall wheelbase shortening, you can shorten the upper links, re-attach them and then determine how much to shorten the bottom (bent) links based on the angle you desire the yoke to exit from the rearend at. This way you can determine the how to get the best drive shaft angle for clearance and any binding issues in the u-joints.

I should also mention now (if I haven't already) that the skid plate/motor mount has provision to move the motor forward (I think about 20mm). this is necessary at this degree of shortening to accomodate a functional drive shaft angle (in the rear). This all works out very well. The stock length rear drive shaft now fits perfectly I believe, as the front shaft. The rear will have to be custom shortened. (By the way, don't try to cut down your pretty JunFac shaft for this as it will not work. The flat inner portion of the female shaft only occupies the first 5mm or so leaving you with a big round hole that won't turn against the male portion once shortened).

Take your time and consider what you'll get with slight differences of material removals from the links i.e.; check that your rear springs intersect the chassis at or as near to 90 degrees as you think will be best also, what length will require as much or as little movement within the drive shaft as you would like.

Yes, overall capability will be affected. Visually, the tipping point difference was little enough that I would have had to measure it before and after to tell for sure it had changed. I forget now exactly but, I also have about 9 oz. added (before any shortening) to the front wheels, like 5 oz. for the rear, it helps. Not being a competion vehicle (the CR-01) the slight difference isn't significant to me and it's still damn fun!

I've set this thread to notify me for sure, if you have any more questions (sorry I missed this when it was fresh). Good luck.

[DRW-FJ40]

Thanks for the response. I haven't gotten around to shortening it so I can still use your latest info. It will be a good winter project. I put 2.2 roklox on it & it's even more critical to shorten it now because the tires rub on the backs of the fender wells. I'll let you know if I get stuck.

[jimjam]

Originally Posted by DRW-FJ40

Thanks for the response. I haven't gotten around to shortening it so I can still use your latest info. It will be a good winter project. I put 2.2 roklox on it & it's even more critical to shorten it now because the tires rub on the backs of the fender wells. I'll let you know if I get stuck.

Let me know if I can help. In case I'm not notified by the forum: xcx989@gmail.com