Hot Rod Forum banner

Rear Axle Bump Stops

21K views 59 replies 9 participants last post by  sedanbob 
#1 ·
I need to add bump stops to the rear axle of my sedan. I have a Pete & Jakes chassis with a Ford 9 inch rear on parallel 4-bar/panhard bar setup with coilovers. I purchased a pair of the Energy Suspension polyurethane bump stops. They are about 1 1/2" in diameter and about 2" tall. They seem to be as hard as a rock! Is there a softer bump stop? It seems like these wouldn't be much different than steel on steel.
 

Attachments

See less See more
1
#4 ·
I assume that the picture up top is the car we are talking about? How much has the car been lowered and how much travel do you have in your suspension. If it's been dropped a lot and little room for travel, bump stops aren't going to readily solve the problem. When a car is lowered and not enough room allowed for the suspension to travel it's got few options but to hit somewhere on the frame. A softer bump stop may soften the blow somewhat but it's still going to hit the frame and with a softer stop, it will hit the frame sooner.
 
#5 ·
With the full weight of the car (and full tank) there is 3 1/2" between the frame rail and the top of the rear axle housing. Obviously that would be reduced by the height of the bump stop, but if that stop were progressive, it would function like an additional progressive rate spring.
 
#6 ·
It would to a degree, but going over the same bump at the same speed, expect the same results or maybe worse with a softer stop. Now your frame is hitting the stop...with a softer stop you may be hitting axle to frame sooner. You have 3 1/2 inches of travel before your axle hits your frame rail. I would think your suspension is capable of more travel than that. I'm not trying to be a critic and offend but 3 1/2 inches, less 2 inches for the stop equals 1 1/2 inches...not much movement before impact. You could try going to a "non urethane" stop, they are softer but, I don't think it's going to give you a fix for your problem. It will still bottom out, in fact I believe sooner with a possibility of doing damage.
 
#11 ·
I've got a TCI '32 chassis and I'll be using Vintique rubber bump stops. As you can see the chassis has the C notch and these fit perfectly up in there (not installed yet), you just have to bend the tab a little to match the curvature. The rubber is pretty hard but not like urethane and it can be cut down to fit your needs.

You can see the need for bump stops on mine, if I hit a bad whoopdedoo and bottomed out the panard bar bracket would hit the upper 4 bar:pain: Anywho the part number is messed up but it looks like ??-5783. Here's a pic.....
 

Attachments

#12 ·
I'm getting a much better view now, I do have a better understanding of what your saying. Still, I'm very interested in the end result. I did a 37 Chevy a few years ago with a similar problem and had to modify the frame rails to allow for suspension travel. That was a few years ago, technology changes and maybe I can learn something. Please keep me informed.

Ray
 
#13 ·
Thanks 327Nut! I don't have a C-notch, but if I did, I could have the same issue. As it is, my axle housing could sit up against the frame rail and the panhard bar and 4-bar would still miss - just. I haven't heard back from Energy Suspension yet, hoping they have a solution. I'll post what they tell me, and post a picture once I've installed whatever it turns out to be.
 
#14 ·
sedanbob
i used those same bump stops on my truck
not a good pic but i welded an angle bracket on the side of my frame next to my c-notch
i have about an inch of rubber below the c-notch, i hit them hard occasionally, they do their job well
any oem bump stop appears as hard as a rock and are usually a lot wider
these are progressive by nature of the taper

 
#16 ·
OK, I need to understand a few things...(sorry Sedanbob" but, this has been bugging me all night)...As I mentioned earlier in a post on this thread, I had a similar problem on a 37 Chevy I did a few years ago. Well I went and dug through some old records I had (I can't believe I found them as I had a fire about 4 years ago and a bunch of stuff got lost in the blaze) and I was running just over 5 inches of clearance between the axle and frame and still required to do more frame mods to resolve the bottoming out effect and get the full use of my suspension travel. Now, this is the last pre-war Rod that I did the complete design and build and I finished in 1999. It ran a Ford 9", with a 4 link rear.

I hope this question doesn't sound outlandish but, has suspension technology improved and changed that much for the 30's Rods in 1 and 1/2 decades or am I missing something. I am trying to understand how 3 1/2 inches of clearance less a 2 inch bump stop is going to do anything but bottom out?

Very seriously I would love to understand this.

Ray
 
#17 ·
You are correct - 1 1/2" of travel is not enough. That's why I thought these bump stops were too tall, unless they were much softer and progressively got stiffer. I am still waiting to hear back from my e-mail to Energy Suspension, but have been looking at other bump stops that are shorter. The clearance under full load also equates to the amount of travel left in the coilovers. I could change the height of where the coilover mounts to the rear end (it is adjustable) but the travel in the coilovers would remain the same. They would bottom out before the axle would. This might be a much stiffer suspension than you had? This is the standard rear suspension package (one of several) from Pete and Jakes for '33/'34 rods. I should probably also give them a call after the weekend for their recommendation.
 
#18 ·
OK, I feel much better now, The 37 that i built did have a nice ride without giving up height. It has a 454 lS6, lots of power but, in all honesty it could have hooked better with more aggressive rear suspension. Thank you, this has been bothering me all night and I lost sleep. I would love to hear what Pete and Jake's have to say as well, it might be good information for both of us and all on this forum.

Ray
 
#19 ·
69-Widetrack, Thanks for your interest and questions - they have made me look further into this. I just visited the Aldan American coilover website for more information. The total suspension travel on many of their units (not completely sure which I have - I'll find that out too) is in the 3.8" range, with the most being around 5". One page they have on how to set up your coilover shocks say if the travel is 3", plan on 2" compression and 1" rebound. They also said the shocks will be compressed about 1 1/4" to 1 1/2" at ride height. They also said the suspension should hit the bump stops before the shock bottoms out. Here is a link to that page: Aldan Eagle Shock Absorbers | Carson California | All Parts Made In America
 
#20 ·
This does all make sense...3 inches of travel with 2 inches compression and 1 inch rebound. My question is the limit of travel you have with 3,5 inches clearance and a 2 inch bump stop, with 0 travel being your center point, you have exactly 1.5 inches of travel either way and that's exactly when your suspension hits your stop...I hope I'm not missing something but it would appear as though your suspension is not being allowed to do it's full job. To me, and I could be wrong. it looks like a clearance issue. Upward travel is also dependent on load so when you've got a full tank of gas and passengers I would think the problem would be more noticeable, am I correct in that assumption?

I've thought about this so long and hard, I wish I was there to actually see it. Seeing it has got to be worth a 1,000 posts. Oh well hopefully they will get back to you tomorrow and have an answer.

Yet again, PLEASE, keep us informed.

Ray
 
#41 ·
This does all make sense...3 inches of travel with 2 inches compression and 1 inch rebound. My question is the limit of travel you have with 3,5 inches clearance and a 2 inch bump stop, with 0 travel being your center point, you have exactly 1.5 inches of travel either way and that's exactly when your suspension hits your stop...I hope I'm not missing something but it would appear as though your suspension is not being allowed to do it's full job. To me, and I could be wrong. it looks like a clearance issue. Upward travel is also dependent on load so when you've got a full tank of gas and passengers I would think the problem would be more noticeable, am I correct in that assumption?
...

Ray
this is my suspension without the bed and the bump stops located
i mounted the bump stop on the side of the frame so it into the c-notch 1''
with the bed on and a full tank of gas i have approx 2'' between the axle and the rubber stops
with the bed loaded for a couple of power tours i had to add air shocks to handle any load



truk was level before the air shocks, now it has a one inch rake to it
i know i messed up, i should have raised my bed 2'' and done a 6'' c-notch
this is my first build, i have learned a lot thru out the build, mostly what not to do :D

 
#21 ·
Just a short note, I sincerely want your situation to get resolved but I have my own motives as well. I'm in the process of designing and building a project for a customer and the entire suspension is being upgraded to current and better handling components. I want to make sure that I'm not missing anything or have a misunderstanding.

Beautiful car you have...looks awesome and I know it will get resolved.

Ray
 
#22 ·
Thanks Ray! I agree that with the tall bumpstops, the suspension can't travel as it was designed to, perhaps with a shorter stop. The link to Aldan, and sites like Fatman's Fabrication, and Pete and Jakes should help you design what you need for your customer. There are some good instructions on the Pete and Jakes site to help you figure out different suspension designs. Fatman's has some really smart engineers that could help you determine what you need. Naturally, as you work that out, please share!
 
#23 ·
I will share as soon as I can...I just have this customer that came up with a very unique idea that's never been done before. When he told me about it I kind of looked at him funny but I couldn't help but keep nodding. It probably wasn't until I did an artist's rendering for him that I bought into the idea completely, it makes total sense and to be honest with you, it's consumed me for the past three months. I've done work for this fellow in the past and he is a rare breed, after we come up with a budget he has never complained about price, any extras or changes he understand cost money and has complete comprehension of time lines being guide lines....not set in stone.

Every build I've done for this guy has been extremely enjoyable but he is particular about fit, finish, performance, looks...the whole package. This is the first time he has asked to keep everything quiet and if he's paying I can't argue.

I haven't pick up a wrench yet and I have well over 100 hours into the project...all I can say is that it's a 69 Pontiac and parts will be rolling in soon. I just wish I could say more.

I thank you for all the information and I am spending many hours doing research in all these area's and one area that many people neglect is suspension. To many people buy a big motor and put on fancy paint and feel they have the complete package, they don't understand as you said about "smart engineers" required to create a user friendly build.

Thanks for the information and I will follow up, as I'm sure you've guessed, my suspension is not carved in stone yet.

I love it when I can throw my heart and sole into a project...so much more fun than painting the front clip on a Honda Civic.

Ray
 
#24 ·
I called the Energy Suspension tech line - not much help. I told them which ones I had purchased and why I didn't think they were right for the job, thinking shorted would be a better fit for me. The guy told me that they were all "about the same" hardness-wise and that I could cut the ones I had shorter. Cutting them would remove the tapered tip, which seems to be the softest part. So... I called Jason Slover at Pete and Jakes. He is sending me a pair of the bump stops they recommend. They are shorter, but I don't know yet how hard they are. He is shipping them today. As soon as I get them I will post a picture of them, and another once they are installed. Good guy to work with!
 
#25 ·
Thank You so much for keeping us posted.....I've been doing some research on my own and will let you know the results when I get something definitive. This post has been of great help to me and for the build I'm embarking on. It has made me revisit a potential problem I haven't seen in many years...Thanks Again
 
#27 ·
Ray, I ordered the chassis from Pete and Jakes, and the fiberglass body from ******* Streetrods. From there I plumbed it, wired it, figured out the steering column and linkage, and everything else. I built the dash extension and console out of fiberglass. I turned it over to Fast Eddies Streetrods (sister shop to *******) for paint, after I spent two weeks there getting it prepped for primer. They shot the color and clear, cut and buff, then gave it back to me to finish. I still have upholstery to do. My seats are being made as we speak. When they are done I'll turn the car over to the local trim shop to finish the interior. It's been about 4 1/2 years since I order the chassis, but managed to pay for everything out of pocket as I went along. Got it licensed last year and have a little over 900 miles on the odo. It's been a lot of fun! A '33 sedan has always been my dream car.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top