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V1 Front wheels shaking and hopping under hard braking (Now fixed!)
Ross
Goblin Professor
- Ross Goblin Professor
I think it is fixed now. Does this look like your Goblin under real hard braking?
70mph to 0 hard stop:
photos.app.goo.gl
Much better than before. Barely has any shaking/hoping just before the tires lock up.
Finally swapped the tie rod ends, and gave it a new 4 wheel alignment.
I might add more brake boost now that it is working correctly... I can run out of pedal!
Getting ready for Saturday's autocross with Reaction Motorsports.
This is my settings for the street, not a racing alignment. All set with the weight of 2 people in the car.
I'm playing with various settings trying to find the best mix for wide tires.
Rear: 1 degrees camber, 1/8" toe in. Bottom of the aluminum swing arm is horizontal.
Front: 1 degree camber, 1/8" toe in, 6.25 degrees caster,. Lower A arm is horizontal.
70mph to 0 hard stop:
New video by Ross Lawrence
photos.app.goo.gl
Much better than before. Barely has any shaking/hoping just before the tires lock up.
Finally swapped the tie rod ends, and gave it a new 4 wheel alignment.
I might add more brake boost now that it is working correctly... I can run out of pedal!
Getting ready for Saturday's autocross with Reaction Motorsports.
This is my settings for the street, not a racing alignment. All set with the weight of 2 people in the car.
I'm playing with various settings trying to find the best mix for wide tires.
Rear: 1 degrees camber, 1/8" toe in. Bottom of the aluminum swing arm is horizontal.
Front: 1 degree camber, 1/8" toe in, 6.25 degrees caster,. Lower A arm is horizontal.
Last edited:
Desert Sasqwatch
Bigfoot Goblin
- Desert Sasqwatch Bigfoot Goblin
Ross, did you shorten the a-arms? Change the steering settings? Change springs? Give us a good explanation of what was done and what you think finally fixed the problem. May come in handy down the road for a fellow builder. 
Ross
Goblin Professor
- Ross Goblin Professor
I put the correct tie rod ends on my car. The shorter tie rod ends go in the front.
This allowed me to shorten up the front A arms about 1/2" shorter.
My bottom A arm only has 1 thread left all 3 of the heim joint ends, the top A arm was used for the alignment.
The bottom A arms are tight to the body.
The wheel alignment angles are basically the same as before the change.
Springs are back to the same as before (125 lbs / inch) which is a very light spring, but our Goblin has a light front end.
Now that I can brake hard, I might want to get heavier springs up front... they dive a fair bit under braking.
This allowed me to shorten up the front A arms about 1/2" shorter.
My bottom A arm only has 1 thread left all 3 of the heim joint ends, the top A arm was used for the alignment.
The bottom A arms are tight to the body.
The wheel alignment angles are basically the same as before the change.
Springs are back to the same as before (125 lbs / inch) which is a very light spring, but our Goblin has a light front end.
Now that I can brake hard, I might want to get heavier springs up front... they dive a fair bit under braking.
Torchandregdoc
Goblin Guru
- Torchandregdoc Goblin Guru
Is that video with the wide tires or are those your old ones?
Torchandregdoc
Goblin Guru
- Torchandregdoc Goblin Guru
The r1r is what I'm looking at. I think tire and wheel selection has been the hardest part of our build. I'm looking at 275/40r17 17x9.5+22. I'm just concerned that the control arms on the Goblin can't handle the torque generated by the massive meats on your car. Im curious if the reduction in width is partly responsible for the reduced hop.
Torchandregdoc
Goblin Guru
- Torchandregdoc Goblin Guru
That's cool,well.....not cool, but I'm glad it wasn't tires. Looks like you probably have it figured out. How fast were you going in the above video? Looks like it stopped fairly effortlessly. A little shaking, but nothing violent. Thanks for the tire info.
- Lonny Administrator
The motion ratio of our front suspension is .65" shock travel to every one inch of suspension travel.
125lbs. x .65 = 81.25lbs of effective spring rate.
An Ariel Atom has an effective spring rate of 283lbs in the front, which is the equivalent of a Goblin using 435lb springs.
QA1 says that for a streetcar the springs should typically be compressed 25% of the free length when supporting the weight of the vehicle.
5.5" x 25%= 1.375"
300lbs front corner weight /.65 motion ratio = 462lbs at the shock.
462/1.375" =336 lbs
I think this means you should have a minimum of 336 lb spring rate for a streetcar and for a performance setup it should be more.
https://www.qa1.net/tech-center/spring-rate-tech
125lbs. x .65 = 81.25lbs of effective spring rate.
An Ariel Atom has an effective spring rate of 283lbs in the front, which is the equivalent of a Goblin using 435lb springs.
QA1 says that for a streetcar the springs should typically be compressed 25% of the free length when supporting the weight of the vehicle.
5.5" x 25%= 1.375"
300lbs front corner weight /.65 motion ratio = 462lbs at the shock.
462/1.375" =336 lbs
I think this means you should have a minimum of 336 lb spring rate for a streetcar and for a performance setup it should be more.
https://www.qa1.net/tech-center/spring-rate-tech
Dsteinhorst
Well-Known Member
- Dsteinhorst Well-Known Member
I was wondering this when I got longer shocks. I could tell it was between .5 and .75, but having the exact number is good.
Jlarson524
Active Member
- Jlarson524 Active Member
So I am just seeing this now. I don't believe I swapped out the Tie rod ends at all so I am still running the long ones on the front and short on the back. I remember hearing my alignment guy state something about they should be shorter in the front and longer in the back. I am assuming its highly recommended to swap them?
ctuinstra
Goblin Guru
- ctuinstra Goblin Guru
I was thinking about this the other day and forgot to post. It seemed as if your front was diving a heck of a lot. And if you have light springs, that would make sense. When it dives that hard, the tie rods will pull the rear of the tires in causing a heck of a lot of toe out during a hard stop. I could see the tires fighting the excessive toe out and causing this. While bringing the wheels and tires closer in will help control them more, it might be a 1-2 punch to also go with a stiffer spring and really get it under control.
Ross
Goblin Professor
- Ross Goblin Professor
I bought those light weight springs for the rear of the car, but swapped them front/rear as an experiment. Now that the brakes work without wheel hop, I do need stiffer front springs. I went to summit and bought these QA1 10HT225/475 - QA1 High Travel Coilover Springs
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