Ross's extended city, easy entry Goblin- 06 SS/SC, NW Arkansas

[Ross]

- yes both front wheels hop.
- yes they appear to be equal
- the steering seems unaffected by the bouncing. (Well, now that I have a good wheel alignment, the steering is unaffected.)
- No, I haven't tried new rotors. Dale & I pulled the front rotors off the front of my 2nd donor, planning on testing the rotors, but they were too big. so we only tested the front pads. Are the rear rotors the right size on an 06 SS SC?
- I have tried new hubs. That was the first thing Jermey suspected, so I put new Moog hubs on. The 2nd donor has some hubs too, that I haven't tried.
- Yes, I have bled the brakes every winter, when I pull the engine. I haven't tried a new master cylinder, but the 2nd donor has one I can try.
- I agree. Thanks for the suggestions. I will continue swapping parts. I hadn't thought about swapping master cylinders.

 

[ccannx]

Could it be in the steering rack ? Never-mind I see you said the steering is not the issue. Just sorta reminds me of speed wobbles.

 

[DCMoney]

Can you put your brakes back to "stock", no vacuum regulator, brake bias control etc? Remove any doubt something you've added is causing this. I understand this has always happened but I'd try to get your brakes down to the simplest form.

 

[Ross]

Can you put your brakes back to "stock", no vacuum regulator, brake bias control etc? Remove any doubt something you've added is causing this. I understand this has always happened but I'd try to get your brakes down to the simplest form.

Yes, when I replace the master cylinder, I can easily remove the brake bias & vacuum regulator.

 

[Waterdriver]

Are you running centering rings for the wheels?

 

[Dale E]

It was AWESOME!!!!!!! Those wheels hopped like they were basketballs and I was dribbling down the court for a score!!!!! I think I made 6 points in one shot!!!! Okay, yes this is joking - or attempt at dry humor!!

Is this what a very first ride in a Goblin is supposed to be like?? Is this how you experience your very first time driving a Goblin?? Well, naturally not!!

Now, historically speaking. As any good doctor would do a good and accurate history of problem is necessary. So, Ross's problem was before his autocross gardening experience - in fact, the autocross incident was caused by the wheel hop!! This would appear to me to indicate there was no modifications from stock/standard build.

I broke my own rule of changing only one thing at a time -- but there were so many things off I figured to just fix this and that.. Naturally, as Ross found out, my measurements are visual, then measure. Ross was gracious and went along with changes.

Since it was not my car, I was unfamiliar with its nuances.

When I drove it wouldn't hop if I braked normal (as I do) but on a jam bam panic stomp I made it hop, but my hops were little hills. Ross's hops were mountains. Well, you get the idea I hope. Doesn't make any difference the outcome was the same -- hop, hop, hop!!

Different alignment, different ride height, different shock settings (clicks soft to hard), different tires (skinny, medium, fatty), different tire pressures, one person in car or two, different brake bias setting and different booster pressure (since Ross added those in system), adding structural rigidity and other things has not mitigated the hopping problem.

Someone suggested changing parts from a known good Goblin? How much time do you have? Do you just change one side or both to test? With each part changed comes new alignment settings, time and tools (each car). Then changing back to original cars, do it again. Do you change one part at a time? Or change in pairs (LCA/UCA with heims, include uprights, rotors, brakes, wheels, wheel spacers?

I only had a day with Ross, so you builders having a week to a year or more with your own builds hopefully understand the frustrations Ross is having. This very forum is testimony to all the problems, questions poised, and help you each received. Please continue to support each other along your journey.

Above - just questions - remember - history, diagnosis,, plan of treatment/action! Continued therapy/maintenance!

Okay, now all of you Goblin folks come to the table and consult. History checked off. In diagnostic stage - incomplete to date.

My treatment/action plan at this stage is -- rebirth -- new parts, review build guide, and transplant a new front suspension, brake master cylinder, other things to get back to stock build state, then one at a time add back in the booster control, brake proportioning and other accessory hardware, parts.

And, as always, my observations/opinions!!

Dale

 

[k.rollin]

You say the magnitude of the wheel hop was different between drivers; perhaps a change in driving technique would help to mitigate the issue? It treats the symptom rather than the cause sure, but may also explain why none of the other builders here have experienced the issue. Just a thought...

 

[Gtstorey]

Someone suggested changing parts from a known good Goblin? How much time do you have? Do you just change one side or both to test? With each part changed comes new alignment settings, time and tools (each car). Then changing back to original cars, do it again. Do you change one part at a time? Or change in pairs (LCA/UCA with heims, include uprights, rotors, brakes, wheels, wheel spacers?

I would probably start by moving the entire front suspension over, from A arms out. If the cars are supposed to be identical both sides at once (assuming the problem exist on both wheels). If the problem is still there you work you way inward to steering rack, master cylinder etc. If the problem is gone, put the "Ross" parts on the other Goblin. If they follow the parts, then start working your way back through the suspension and brakes. A lot of work, yes, but at some point you are narrowing it down to certain subassemblies, instead of swapping random parts.

Actually start with swapping tires/wheels.

 

[Ross]

You say the magnitude of the wheel hop was different between drivers; perhaps a change in driving technique would help to mitigate the issue? It treats the symptom rather than the cause sure, but may also explain why none of the other builders here have experienced the issue. Just a thought...

Yes, a change in driving technique does completely fix this issue. When I drive normally, wheel hop isn't an issue. It is aggressive driving with big tires that gets it hopping. I have a lot more seat time in my goblin, so I am comfortable jamming down the brake pedal. Dale was learning my goblin, and it takes time to know how a car will react to aggressive maneuvers.

 

[Ross]

Are you running centering rings for the wheels?

Yes, kind of. The spacers I have for the big tires are hub centric and wheel centric, allowing the wheel to be centered independently from the lug nuts. When I tested for wheel hop with the cobalt wheels and tires, I am not using the spacers... so I have mentally eliminated the spacers as a possible issue.

 

[k.rollin]

Have you been able to swap cars at a meet up and drive someone else's build as you do yours? I only have a vacuum regulator fitted to mine but if I hammer the brake pedal, my fronts just lock and skid.

 

[Ross]

Have you been able to swap cars at a meet up and drive someone else's build as you do yours? I only have a vacuum regulator fitted to mine but if I hammer the brake pedal, my fronts just lock and skid.

I usually have more respect for other people's cars than to drive it like it was mine.
I expect my race motorcycles to perform correctly at their limit, and I want the same for my goblin.
I have rode passenger in Jermey's goblin, and his tires have a lot more grip than mine, so I know the goblin can handle the higher limits than what my 275 proxes tires are capable of. I have drove one other goblin, but not aggressively.

 

[JBINTX]

I usually have more respect for other people's cars than to drive it like it was mine.
I expect my race motorcycles to perform correctly at their limit, and I want the same for my goblin.
I have rode passenger in Jermey's goblin, and his tires have a lot more grip than mine, so I know the goblin can handle the higher limits than what my 275 proxes tires are capable of. I have drove one other goblin, but not aggressively.

I know it is not a lot of help, but another data point is that I run the same tire and same size in autoX as well. No hop. So your tires are not some odd ball with weird dynamics.

 

[k.rollin]

I know a lot of us are running a decent section width, 200 AA A tire without issue. I'm just wondering how to induce the wheel hop in a different car as an experiment, because I would expect the fronts to lock up and skid.

 

[TheNuker]

@Ross Just wondering, as i'm sorting through wheel/tire choices for this built. Do you think the 315s actually get up to temp well on the goblin?

Thanks,
Nuker-

 

[Ross]

@Ross Just wondering, as i'm sorting through wheel/tire choices for this built. Do you think the 315s actually get up to temp well on the goblin?

Thanks,
Nuker-

Probably not. I think autocross is pretty much a cold tire event. 1 minutes of play time, 20 minutes of cool down.

 

[Fozda]

Is it possible that everybody else could have the same issue if we were able to get that much traction under braking and braked as hard as you do? I know i've jammed her down good but the tires just lock up. I'm just wondering if it seems like an isolated incident because nobody else has been able to achieve your level of braking ability yet.

 

[Ross]

I wish. Jermey's hoosier slicks have a way more traction than my proxes tires. So I am not achieving new limits here.
Lonny reached out to me yesterday, and offered to swap out parts until we identify which part is the issue. Very nice offer.
I am going to swap out front brake rotors, master brake cylinder, maybe a heim joint. If that fixes it, great. Otherwise, I am travelling to DFW area, and taking Lonny up on his offer.

 

[Ross]

Anybody know what rotors to buy for our front wheels? It is smaller than my SS donor's rotors.

 

[r3drckt]

Not off hand. I'd have to check the part number when I get home, unless someone else get to it before me