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Pre-runner type suspension stuff

Goatman

NAXJA Forum User
NAXJA Member
Location
Bakersfield, CA
I'm interested in a discussion about go fast driving and suspensions. I wonder what you guys who have been involved in desert or rally style racing can add from your experinces. I think I have a basic grasp of the subject, but I'm interested in what specifics could be shared about it.

I'm currently reworking my suspension towards pre-running. Not that I have any pre-running to do, but we've gotten in the habit of racing each other (sort of) to and from the trails when in the desert, and I'd like to go watch some Jeepspeed races and it could be fun to follow along to watch.

I'm working on overall travel, shock type and dampening, and bumpstops. I'm also interested in spring rates (which we've been talking about), though I think my current springs aren't too bad. I also wonder how reliable leaf springs, control arms, mounts, bumpstops, and stuff are with the pounding they would take in pre-runner style driving. I love rock crawling, and I like pretty trails and camping, but I'm getting more interested in hauling ass at times. :D

So, what does it take to make an XJ able to run close to a Jeepspeed rig and hold together?
 
reinforce the entire unibody, full interior cage that ties into all suspension points on the unibody. if you dont want to do too much cutting you can relocate the front lower shock mount to the control arm mounts, however i suggest making your lower control arm mounts out of 1/4" steel and run a double shear on the longer bolt you woudl use. YOu can also run a hydraulic bump stop inside your coils. a good long arm setup or some beefed up drop brackets are a good idea. In the rear you cannot use the stock upper shock mounts since the cross member will just rip ou, so run the shock up into the cab. as far as shocks i recommend the bilstein 7100's 12" short body valved 255/100 for the front if your running about a 5" lift and you dropped the shock mounts to the lower control arm mount. Inthe rear you can run a 16" travel shock with shock hoops but you will need some very flexy springs, some leaf packs from deaver spring or nationals are good. anythign with alot of thin leafs. the one other thign you need is $$,$$$ going fast you break about 3 times as many parts, bend axle tubes ect. I can discuss this forever almost.
 
Hey Richard-

i really like the fact that you have become more interested in desert speed type offroading. I love this forum and this group and have considered joining many times except that 99% of the people here are into slow rockcrawling type offroading, and I love flying through the desert. I would love to see some people from here show up at a jeepspeed race and prerun a little. We usually prerun one lap the day before the race and then just camp out, cook, talk, and watch the cars fly by the next day.

I have broken something on all but one prerun, so I have learned a little. Reinforcing is the main thing here. I know you have done a lot, but for the sake of others, make sure you do something with the LCA axle mounts and the UCA pass. side axle mount (although axles with the auto disconnect have a strong pass. mount). Strengthening your steering box is a good idea, people usually plate it. Running a brace to your trackbar mount is a good idea. Motor mounts will break eventually. The problem though is not just the A-shaped mount with the bushing but the bracket on the motor as well. To hard of a hit will crack the block when the motor mount bracket breaks off. You have to use some of the extra holes on the side of the block for extra strength. Stock control arms don't last long. Bushings however haven't been a problem with me. I run skyjacker mid length arms in the front (21") with a heim at the axle and a bushing at the body and it has been fine for about 1.5 years now. I also run bushings on the rear shock lower mount and they have been fine too. If you race they won't last long, but with prerunning-type driving occasionally they should be fine.

Depending on how far you run, resevoir shocks may be required (I know that you have been looking at some Richard). Within a few miles of desert speed, normal shock will get hot enough to blow. When we prerun or just go camping in the desert and speed for a while, my light cherokee (only extra weight is suspension parts and a roof rack) will heat my 7100's up enough in a few miles that I can't touch them. We usually run one lap which takes 1.5 hours and is typically 40-60 miles. I'm working on new plans with either more shocks or bigger shocks.

There are different theory's just like in rockcrawling, but in general, the spring rates are stiffer than yours. Though some racers run skyjacker and rubicon springs, many will run Currie and Deaver coils.

http://www.offroadjeepparts.com/purchase/inventory.asp?uid=26014992&group=22&cat=222

The front racing springs are a progressive 250/300 lbs rate, which is stiffer than most springs. You will notice that while the rear "sport" leaf is 165lbs/", the rear "race" leaf (or is it leaves?) is only 150 lbs. I agree with many racers who say that a stiffer front and softer rear spring is the best set up. The idea is that it keeps the front of the jeep up and the back down when coming off a jump. If it is a drop off, it doesn't matter, but a jump that rises first will compress the suspension before the jeep launches. The suspension will start to rebound as you launch off the lip and if the rear rebounds faster than the front it can kick up causing a nose dive. This is also true in the whoops. Cherokees will have to deal with this more than a truck because of the short wheelbase. Racing shock valving for the bilstein 9100 people use is 360/115 for the front and something close in the rear, some thing like 315-360/100-115. I run 255/100 front and 255/70 rear. I mainly want more jounce dampening for both ends.

The last thing I would say is cycle everything and make sure you have clearance. You WILL use all of your travel. Shocks as bumpstops won't last, and I've seen people tear out important parts off their jeep using the shock as a bumpstop. Remember that if you hit both bumpstops at the same time and your shock is almost bottomed, then if only one side gets stuffed the shock will compress more. This is if your shocks are still in the stock position which is more towards the outside of the axle than the bumpstop. I was confused at first how I was bottoming my shocks and never thought that the shock be BARELY outside of the bumpstop would matter, but it does. Oh ya, stock front bumpstops will compress all the way to the metal, and rears will compress about 2-2.5" when hit hard. If your shock and bumpstops have 7" of bump-travel and your tire is 6" from your fender, watch out.

Well, i've typed more than I should have. Hope this helps a little. I still have a very hard time keeping up with the Jeepspeed guys. While you're probably a better driver than I am in all situations, I think just the side and weight of your jeep will make it hard for you also... but it sure is fun to try.

marcus
 
I'm glad someone posted about this because I like going fast in the desert and dirt roads also. What do you do about your front sway bar endlinks? The two times I have lead footed it through the desert or sand dunes I bent the crap out of the end stock type end links as well as some disconnect styles. This usuallyoccurs when one front wheel hits a high or low spot and the other doesn't at a high rate of speed.
 
I have the JKS links and they have been fine so far. I wish I had enough shock under the front to get ride of the anti-sway bar, but it is to tippy for me right now. Only problem I've had is the axle end mount for the link gets loose because of the stress. Last time I went to the desert, the bolt loosened and lower mount just fell off. The stock links will never last because of the stupid upper mount.

Marcus
 
Marcus, very good info...EXACTLY the info I was looking for. What have you broken on pre-runs? I don't like to break, so pretty much everything on my rig is beefed up. I wouldn't come close to qualify this rig for Jeepspeed because my whole front suspension is redesigned and all the mounts are both moved and beefed up. The only part of my suspension that is still stock is the rear spring shackle mount at the frame, the shackle box, and it gets rebuilt tomorrow since I have ripped the captive nut out of the frame on both sides. The front leaf spring mount is one from a circle track car, mounted horizontal rather than vertical like they do (so they can adjust anti-squat).

Do you run stock bumpstops? I'm real interested in bumpstops. I'm surprised to hear you say that the front bumpstop will collapse clear to the metal. I have a Daystar poly bumpstop on top with hocky pucs bolted through on the bottom, and they touch with about 1.5" of shock travel left. The poly bumpstop seemed really stiff, so I cross drilled two sets of holes so it had more give. I have no idea how they will hold up in hard use.....we'll see. My suspension has been cycled and checked extensively, and I have the needed clearance when articulated, but it's good to know how much the bumpstop is likely to compress. I'm considering adding poly bumpstops to the shaft of my shocks as an added precaution.....maybe that's a good idea. What do the Jeepspeed guys run for bumpstops (the ones who don't have air bumps)? In the rear I also have Daystar XJ extended poly bumpstops, and I really like them at first. I almost couldn't feel the rear bottoming out, but they didn't hold up. They have a gap in the bottom, and the bottom piece of poly has already broken. I'm curious how much they will compress, after I remove the broken piece and eliminate the gap.

My shocks are remote resevoir SAW's, but the valving is too soft so far. I think they built them more for crawling than going fast, and the presure in the shocks is very low (150 psi front/100 psi rear). I'm going to try them at a higher presure first, then see about adjusting the valving. I haven't actually run them yet, but Mark has and he said they were too soft, I'm going to bump up the presure and see what they do. I prefer a stiffer shock for more control, but it's hard to guess how crawling will be effected by a shock stiff enough for near race conditions......why I'm interested in others experinces. Now, if I had the dough for air bumps and/or bypass shocks it might be easier to reach a compromose.

Well, I'll stop for now, or no one will read it all. :)
 
marcusguy said:
I have the JKS links and they have been fine so far. I wish I had enough shock under the front to get ride of the anti-sway bar, but it is to tippy for me right now. Only problem I've had is the axle end mount for the link gets loose because of the stress. Last time I went to the desert, the bolt loosened and lower mount just fell off. The stock links will never last because of the stupid upper mount.

Marcus

I have quit running the sway bar, but I've wondered if it would be beneficial for pre-running. Since the last time I rebuilt my rear leaves (MJ length, 5" longer), if I keep my Rancho 9000's on 4 or 5, it handles fine without the sway bar (RE 4.5" ZJ coils). However, while I have more control, the rear is a little stiff with the shock at that setting. It's more comfortable set at 3, but less stable and would likely bottom out more easily. It was very stable and comfortable to drive with the sway bar on and the rear shocks set at 3. I don't know yet how stable it will be with the SAW's, I'll see soon. I don't have a problem with my sway bar links, since they are 1/2" heims on both ends with 1/2" all thread in between. The axle mounts are 1/2" pins in double shear, and the tops are bolted in double shear and bolted to the sway bar with no bushings.

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I used to regularly bend the tops of my links, which is why I put a joint at the top and bolted them to the sway bar. I think the JKS links have a joint at both ends, don't they?
 
marcusguy said:
Hey Richard-
I still have a very hard time keeping up with the Jeepspeed guys. While you're probably a better driver than I am in all situations, I think just the side and weight of your jeep will make it hard for you also... but it sure is fun to try.

marcus

So you're saying lighter is better, I better do some more cutting :D

You jeepspeed guys should post-up more. It's interesting to hear how the different demands we place on our XJ's take their toll, & maybe find some tricks that we can incorporate.

I can't wait to see what a Summer of building for go fast is going to bring to JV next season.

Paul
 
Richard Paul and I will still beat you back to camp!

:D

Oh, I should have those air bumps I got on mine by next JV season! :D

hinkley
 
What have you broken on pre-runs?

Um... Tore off my LCA axle mount and LCA, UCA mount on the axle, numerous shock mounts front and rear upper and lowers (rear upper broke and then came on up into the jeep to say HI), swaybar links (before JKS), and every shock that has ever been on my jeep except the 7100s, usually melted them and had the insides fall out although some snapped shafts and eyes off also. Broke stock motor mount. Tweeked my pass-side knuckle where the drag link attaches on one hard hit. My exhaust welds suck enough that they keep snapping on big hits. The amazing thing is that after about 2 years of prerunning, chasing, and just screwing around and driving way to fast when camping, and after all of the other damage, I've never blown a tire. BFGs seem favored in the desert and my A/Ts have been amazing. Before them I had Dueler A/Ts and went through 6 of those in one year with easier driving (only paid for balancing thanks to road hazard). My typical approach is to reinforce before something breaks. It's a lot easier to reinforce something still on the jeep than to pick it up off the ground pound it straight weld it back on and then reinforce it. The only thing I haven't beefed yet is the rear suspension mounts and I need to get on that before they go. I've seen jeepspeeds whose leaf spring mounts bust and the end of the spring usually tears a large hole in the floor.

Do you run stock bumpstops?
I do. I swapped the rears out for a while but went back to the stock ones because they work well enough and gave me more bump travel. Like you, I didn't think they would compress that much. When I was cycling my front end after putting some new shock mounts on, I bottomed out the front and with just the weight of the car resting on the front stops they were almost compressed to the metal. Maybe had a 1/4", at the most. I figure if just the weight would do that, any hit off road would probably compress them that last little bit. I am running the stock stops up front... till someone buys me hydraulic ones. I think that if I had the money (about $1000 for T&J's in SoCal to set you up), I would really think about a nice set of bypass shocks instead. Guys who don't run hydraulic will usually run something like the ACOS (sp?) up front with a stiffer, but as low-profile as possible stop, and a thinner hard poly stop in the rear. I think this is mainly because their suspension travel limits are measured from metal to metal and so the thicker the stop, the more travel you give up. Many of the prerunners and play/chase vehicles run the daystar or something similar.

I saw the picture of the sway bar links and thought of something else. I run the JKS now (RE drove me nuts and then gave up the ghost), and yes, they have a rubber spherical joint at both ends. I have the 4-6" lift version setup as short as I can and 2" of front bumpstop extension. When I bottomed out, the nut on the top of the top of the links dented and eventually punched holes on the inside of the wheel well. I saw it as my jeep doing a little self-clearance. If yours are much longer, you will have to watch for this. I doubt your axle will travel as far up as mine since you have much larger tires (37"s right?), but just though you should know.

I've been thinking about swapping my steering over like many of you guys, and moving my trackbar accordingly, but I have had time to see if it comes to close to the oil pan or not when bottomed out. Again though, you probably have more than 2" of bumpstop spacers in, but it's something to think about.

Are you running your rear shocks up through your bed? The motion ratio would be so much better. Once I have enough guts to start cutting holes in my 99 I will cage it and run some 16-18" sway-a-ways though the floor. Luckily the rear doesn't carry the weight the front does so even with my shocks laid down under the floor and stiffened up from the original 255/70, they still don't get as and fade like the fronts to.

With my set up, I have about 12" of travel up front (7up 5down), and a little over 14" in the rear (about 8.5up and 6down... oh ya, I'm running a full s-10 blazer leaf pack that measures about 57" eye-eye). It RARELY bottoms hard enough that I feel it, but I always have to drive home and prerun accordingly.

Anyways, I'm sure everyone else is bored.

Marcus
 
Not meaning to hijack your thread, but I've been watching this discussion with some interest. I have almost the same questions, but the vehicle is a short bed Comanche. Do your suggested spring rate/shock valving combos apply equally to this longer wheelbase vehicle? I'll assume some things are a bit different...
 
the Comanche is much lighter in the rear, especially if you take off the bed and just have fiberglass bed-sides like most pre-runner guys, therefore your valving is going to need to be different



and you guys really need to stop talking about all this; it's makeing me want to spend more money ;)
 
yea...so there is there any benefit to running spring under axle rather than spring over besides the additional axle wrap control? i see a lot of toyota prerunners running this setup so it got me thinkin. any thoughts?
 
My MJ will retain the stock bed, but your point is well taken on the shocks. I just want to be certain the rear end doesn't want to kick up on me after hitting a large bump. :eek:
 
We need more Jeepspeed guys here, I realy think we can share lot of stuff. I'm getting ready to buy a 2wd 2.5 MJ that is just beggin for some preruner treatment although here in VA there isn't much to play with but it could still be fun "speed bumps? what speed bumps?"I like the look of some of the glass front fenders and would want to put a set on. I like the fact that Jeepspeed has to keep factory mount locations so that its simple and It must work out because those guys seem to do realy well.
 
pro-rallye said:
yea...so there is there any benefit to running spring under axle rather than spring over besides the additional axle wrap control? i see a lot of toyota prerunners running this setup so it got me thinkin. any thoughts?
spring under also allows for lots of up-travel without putting the spring into a negative arch.
 
marcusguy said:
I'm running a full s-10 blazer leaf pack that measures about 57" eye-eye). It RARELY bottoms hard enough that I feel it.

Interesting. Did the s-Blazer leaf pack move your axle aft? Or are the s-10 & S-blazer springs different lengths?

Thx,
Mark
 
Hey Mark,

I don't know if the Blazer and the truck have different lengths or not. My plan was to chuck the main leaf and put the others with my XJ main. But when I started measuring, and looking at my W-shaped xj pack, I decided to go for it. I had to redrill the blazer main leaf and I did go ahead and extend my wheelbase a little at the same time (without redrilling it would have moved my axle back like 5-6"). You wouldn't really know from looking because its only about 2.5". Reason I did it was for a little better stability when hauling in the desert, and because when bottomed, my rear tires hit the front of the rear fender (because the negative arch of the spring would pull them back towards the front). Now they are much more centered when stuffed.
 
Marcus, talking about the shocks. The SAW's I got have bushings, not heim joints. Is this a potential problem for occasional prerunning? Unless I get out to a Jeepspeed race where I can run along with you guys, my quick runs will be much shorter.

From your shock specs, and those of the racers, it looks like you guys are running more compression dampening than the normal shocks come with.....100 to 115 in a Bilstein. What does this do to the ride, is it harsh at all when not running fast? I wonder how that stiff a shock rate would work in the rocks.

The rear of my rig, with the Rancho 9000's in back, was bucking in the whoops. Hopefully, the new shocks will damp more than the 9000's and eliminate that. Can that be controlled with shocks or is it mostly from springs that are too stiff? My rear springs, while able to carry a load, are pretty flexy and ride well. I use an MJ main leaf which is 5" longer than normal XJ leaves ( I forget how long that is).

I've already poked holes in the inner fender well on both sides from my sway bar links. My front bumpstops are lowered about 3.5", and I have 4.5" of up travel before the bumpstops hit, plus however much the bumpstops will compress. You have much more up travel than I do. With my tire size I would need to lift it more to get more up travel, and I'm not willing to do that. I wonder how much different it will work with a few inches less up travel.

My rear shocks upper mounts are in the stock location. I've looked at what it would take to run them up inside, but things are in the way, so it wouldn't be simple. I have 12" travel shocks in front and 10" in the rear. I get a little more than 10" of rear travel since the shocks are at a slight angle.

BTW, I'm almost finished rebuilding my rear shckle boxes. The captive nuts on both sides where completely ripped out and had been banging around for a good while from the looks of it. The compression of the bolt against the outside of the shackle box is what was holding it together. There were many cracks in both boxes that had to be welded up, then I boxed them in. I also welded the nuts to the back of a new plate and welded it into the inside of the box, against the frame (actually against the protrusion from the previously captured nuts). Inside plate is 3/16 and outside boxing is 1/4, so it shouldn't go anywhere now.
 
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