Sand rail autocross/skid pad build (or, why my wife hates me)

Yeah, getting the spacer isnt a problem, a 2 - 2.5 inch spacer would work and they are all over the place. Just for the cost and for the fact I'd really like a square set then if I'm attacking it at that angle I'll just get the new wheels with a 2-3 inch backspace.

Before I continue I want to stop to thank everyone for their ideas. I have been told that my responses when people offer ideas can sound dismissive and that is not my intent. For every solution offered my immediate response is to question the issues it may cause so when I respond with the "yes but...." its just me trying to delve further into the idea. Everyone here has had great ideas, and all of them would probably work with some time/money/additional thought or some combination thereof. I just need to balance all of those things as I have limits on all of them (especially the additional thought)

Ok so some more data points to play with. I started toying with what putting the shock at an angle to the inside of the frame would look like.

Full drop

Full compression (might get some spring bind here

Approximate ride height with spring installed for clearance check

Wouldn't that make the coil over package all but innefective? I remember something about motion ratios affecting spring and val ving rates.

Dusterbd13 wrote: Wouldn't that make the coil over package all but innefective? I remember something about motion ratios affecting spring and val ving rates.

Yep, I was posting it for everyone who suggested going to the inside, the angles are just too steep I think. But I wanted to throw the visuals out there in case it freed up any other ideas :)

Not trivial, but because of how the trailing arm pivots, you could build a lever off the pivot point. It would have to be perpendicular to the pivot axis and would take a bit of thought to make strong, but it would allow you to get the wheel rate back to something reasonable.

On of my FB peeps pointed out an area on the control arm strong enough to take the mount but further inboard than where I have it. This was his suggestion:

And here's what it gives us. Better, maybe even workable with the right tire. But 1/4 inch for tire bulge is probably unrealistic. I could shim it maybe another 1/8 inch closer to the tube that that's really pushing it. This is interesting enough to think on a bit more and maybe wait until I can mount a tire on the wheels to check. At worst we're now in 1" spacer territory instead of 2-3" spacer territory.

I feel like new wheels is the easiest (and reasonably cheap after selling the ones that don't fit) to implement solution here. Rather than mucking about with massive geometry changes, suspension modification, giant spacers or some combination of all of that.

How about instead of in front of this plate:

you put it behind. Then possibly bend the ears the lower shock mount bolts between to be in line with the shock lean. I don't think it will get you all of the way there, but it should help.

MrJoshua wrote: How about instead of in front of this plate: you put it behind. Then possibly bend the ears the lower shock mount bolts between to be in line with the shock lean. I don't think it will get you all of the way there, but it should help.

Unfortunately its a lot further off than that, remember we aren't just talking the distance of the tube you have the coil spring in the way too. From the back of that plate if you angle the shock as close to the tubing as you can aiming for the lower pick up point, the best you will do is end up in the middle of the CV joint. Same issue moving forward, the lower bars just get in the way on the back side.

Kenny_McCormic wrote: I feel like new wheels is the easiest (and reasonably cheap after selling the ones that don't fit) to implement solution here. Rather than mucking about with massive geometry changes, suspension modification, giant spacers or some combination of all of that.

I feel much the same way, this is mostly a thought exercise to make sure I didn't miss anything. Upon looking at it the other wheels should actually fit on the front so I can have a 15x10 square setup with the goodyears and keep Nittos on the 15x8s and just swap the rear sets of tires on rims when I want to use the autox setup or experiment between nittos and goodyear slicks. The new wheels are like $85-90 from Diamond, in the grand scheme of things that's not a lot of money.

Sorry I am not good at putting pictures on here,but, our trailing arms were stock sized, as per class rules, but we were allowed to reinforce them. We had round tubing coming from the outer end of the trailing arm that triangulated to the inner pivot point of the trailing arm. We had a piece attached straight down roughly from the upper mount where the bottom of the shock attached. The top mount was built to "stick in" not "stick out" so the top of the shock was inside the chassis. Your trailing arms look stock. I believe they sell "boxed" trailing arms but I know you are trying to do this inexpensively. I will see if I can figure out how to transfer some old photos to the Internet so I can show you. This is a cool project and I have often wished I still had our old racer, it would be fun to autocross it.

Something like this perhaps?

I took those off the car. The theory is sound but these ones were hack jobs and had been bent at one point so I replaced them with stock.

Yes, the trailing arm could be reinforced to move the shock mount anywhere, I agree. Like most of the solutions mentioned here it is another viable alternative. It's just one from a time/cost perspective I probably don't have the time for. Moving the shocks inboard of the tube requires, as noted, reinforcing the control arms, then creating proper mounts on the inside of the frame structure as well. Realistically a full weekend worth of dis-assembly, fabrication, and reassembly. Once I return from my business trip I will have 5 weeks to be ready for the first autox of the season which will be the only one I will have before the skid pad challenge so I really need it for test and tune.

Just trying to paint the time picture so people realize why I'm taking the "easy" way with ordering new wheels. If time and money were unlimited I'd do a lot of things differently. But with limited time and budget things get done, just not ideally. Prime example, the $2010 challenge Wartburg (holy crap has it been 5 years?) was finished in 9 months because it had to be, but everything was a compromise. I vowed to tear it down and do it right and here we are 5 years later and I have a garage full of parts of what used to be a car as I work out what (to me) is doing it right.

It has often been said that perfect is the enemy of good enough. This is a job for good enough

I'm really thinking that new wheels or some spacers are the way to go, especially as that allows you to keep a decent motion ration and angle for the shocks. It seems the easiest, neatest AND best solution here. Can't beat 3 out of 3!

Questions regarding going to extreme offsets on the wheels:

1.) As it sits now is the track width the same f/r?

2.) If so, will you be able to steer the car with that much rubber to the outside of your steering axis?

3.) If the rear track is wider(or will end up effectively being wider) after you space the wheels out, won't the car tend to push pretty bad?

I just got caught up on this situation and while it does suck to figure it out at this point I think that you have a good handle on how to deal with it in the short term. I completely agree that some new wheels with proper spacing is the best solution to keep things moving forward against temporal and monetary constraints.

JThw8 wrote: It has often been said that perfect is the enemy of good...

^ This, always this! Kind of a mantra in my life and something that needs to be remembered at all times.

Trying to get to AC on April 12? I am shooting for that AutoX as my test session for all of my new changes. I should be at 100% by then... well everything except paint! Good Luck!

petegossett wrote: Questions regarding going to extreme offsets on the wheels: 1.) As it sits now is the track width the same f/r? 2.) If so, will you be able to steer the car with that much rubber to the outside of your steering axis? 3.) If the rear track is wider(or will end up effectively being wider) after you space the wheels out, won't the car tend to push pretty bad?

1. Yes, except for the wheel differences
2. No idea, never drove one like this ;) But the front wheels will have a 0 offset whichever set I use so its not as bad as what will be going on in the rear
3. Probably. It's already going to push pretty bad. A rear engined car that pushes means learning to throttle steer more effectively :)

I hope I haven't given anyone the impression I have any clue what I'm doing. I slap stuff together then trial and adjust. Almost completely irrelevant but back in the day when I raced RC cars I had no money and pieced together cars out of spare parts. I raced at a local dirt oval and due to my junk parts availability I had a narrow front track and wide rear track. This was not a special design just working with what I have. For reasons I still don't understand it ruled its class and for awhile after that a lot of the local guys were trying narrow fronts with wide rears to see if they could replicate my results.

tb wrote: Trying to get to AC on April 12? I am shooting for that AutoX as my test session for all of my new changes.

Yeah, that's the aim for test and tune. There's also a Delaware group event that Duke here is in the know about on the 11th. Trying to get more info, might try to hit both so I can make adjustments from Saturday and test again Sunday.

If we both make it out you are welcome to take the Lizard for a run to weigh in on things. I plan to let a few people drive and theorize as long as the SJR guys indulge me (they are usually pretty good to me)

In reply to JThw8:

Cool. Duke is a really good guy but I only have the time / energy for 1 event per weekend so I will stick with SJR. I have never been there but I hear good things and really like airport courses... plus my parents live 10 mins away so I can crash there and not have to get up too early. They have enough room for extra cars / trailers if the need ever arises for you so keep that in mind.

I would be thrilled to get in it and try to provide to feedback if circumstances permit. Currently I am a couple weeks behind due to some tuning issues but my overall list is short and manageable. I will not be pushing it hard in my car, just making sure nothing breaks too easily on its first outing on hoosiers. Of course, if I do not totally lunch the engine or something, you are always welcome to beat on my ride a bit and tell me about what I need to fix!

Traveling so no progress updates but the whole wheel and tire debate is put to rest now. The set I got cheap on ebay got into major shipping issues when the seller was quoted $75 (and the UPS store accepted the shipment) but after being "lost" for a few days UPS posted it as an weight limit exception and wouldn't move them. Seller finally got them to agree to freight but at a $300 price increase which made no sense for me to pursue since they really weren't right anyway.

VWGuyBruce has a pair of 15x8s that he is sending me for a very GRM friendly price and I'll go buy another set.

Debating if I just get another set of 15x8 or go with 15x10. Keeping everything square appeals to me. But the tires are 27x10x15s

In reply to JThw8:

That things going to look like a life-size RC car with those tires on it!

petegossett wrote: In reply to JThw8: That things going to look like a life-size RC car with those tires on it!

It's a big kid's go kart. I think once I get the wiring harness from the Wartburg pared down to a much simpler stand alone for the engine I'm going to put the subie motor in this while the Wartburg get's rebuilt. Should be plenty stupid with that power.

Have you thought of going the push rod route similar to modern day formula cars? This would allow you to get the maximum benefit from your shock, provide clearance for your tires and potentially move the shock out of the primary dirt environment (prolonging shock life). In theory you would have a push rod mounted to your upright/spindle going diagonally up to your frame where you would mount a rocker arm that the shock would attach to. If you mount the shock at an angle significantly different then the arc of the suspension you reduce it's effectiveness and increase the side load to the shock shaft (looking at some of your previous posts and angles you showed your shock). The ratio of the rocker arm could also increase shock travel.

Here is an example but I would have yours going up over the upper bar:

http://s103.photobucket.com/user/JJLudemann/media/Formula%201000/Formula%201000%20Race%20Car%20Design/cartop005-1.jpg.html

Thought about it but that's not the point of this build. This is simple and quick. Since the original wheel package is not going to be used it's much easier to solve the issue with a proper wheel choice than fully re-engineering a functional suspension.

Back home for some unknown reason, 77 degrees when I left Vegas, 7 when I arrived in NJ...poor life choice. This is the kinda cold that my little shop heater doesnt overcome so today's post is brought to you courtesy of the local machine shop who took my flyweel which had seen better days

And made it ready for use, including a pilot bearing to use with a bug transmission. Nice work.

Been having trouble getting motivated since returning from travel. But I finally got the shifter and seats mounted (pedals are still just sitting there) Seems like a minor task but the seats have 6 mounting holes, aligning those through 6 holes in the floor to 6 holes in the mounts under the floor was a bit of a task.

I also have some wheels on order finally and the tie rods came in. Of course I had brand new tie rod ends on the shelf but they turned out to be inners (RH thread) and I needed outers (LH thread) so I have to wait on those as well.

It's assembled enough you can sit in it and make engine noises, should go quick now.