Steering, Suspension, & Brakes

tips, technology, tools and techniques related to non-driveline mechanical components

Go to Thread: PreviousNext
Go to: Forum ListMessage ListNew TopicLog In


Moderator
Curtis Jacobson
Portland Oregon
(4495 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

authors avatar
bump stops, particularly on MGB rear suspension
Posted by: Moderator
Date: July 02, 2013 01:10PM

Bump stops are one of the few "original" aspects of my car. I'm thinking about improving them.

My MGB rear suspension produces an uncomfortable jolt on bumps, particularly when I have a passenger. I expect many of you have probably trimmed your bump stops, or at least removed the pads that clamp onto the top of the rear axle (held in place by the leafspring U-bolts), to permit more suspension travel.

For about twenty years, I've been thinking that maybe what I need isn't shorter bump stops, but instead more compliant ones. My idea is that it might be a good thing if they absorbed more energy when they compress. I haven't tested my theory, but I suspect that my bump stops don't compress very much at all.

What have you guys done? Got any thoughts about alternative bump stops?


roverman
Art Gertz
Winchester, CA.
(3149 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: bump stops, particularly on MGB rear suspension
Posted by: roverman
Date: July 02, 2013 04:23PM

Properly shaped or hollow pyramid shaped, can act as a rising-rate elastomer spring. I suggest looking at an Energy Suspension/etc. catalog, for whats available. Your results may vary. Good Luck, roverman.


tomsbad6
Tom Ahlstrom
Michigan
(129 posts)

Registered:
12/16/2012 03:16PM

Main British Car:
Triumph TR-6 347 Ford

Re: bump stops, particularly on MGB rear suspension
Posted by: tomsbad6
Date: July 04, 2013 05:57PM

Hello it's me, Tom Ahlstrom there are a lot of ways to do what you're talking about doing it's a very good idea from a standpoint of performance and comfort I believe the keyword in the process is adjustability there are some cheap easy ways to do it trial and error will be a factor stay away from the hard urethane stops tried to find natural rubber stops that are cheap there are two ways to adjust them one is having them screw up and down to try drilling different patterns of holes in them to soften how they hit I first saw this done when I was about 10 years old at the drag strip before the days of everything being 4 link the Mopar guys would run adjustable rubber bump stops on the pinion snuber and on the front of the traction bars which would soften how the rear end bottomed out under load and keep from breaking the tires loose my uncle had in his toolbox rubber bumpers all the same except different patterns and sizes of holes drilled in them I remember he had them all labeled from 1 to 10 one being very soft and 10 being very stiff he would change them to varying track conditions I don't know if that will help you at all but that's my two cents signed still waiting for the insurance adjuster


MGBV8
Carl Floyd
Kingsport, TN
(4120 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB, Buick 215

authors avatar
Re: bump stops, particularly on MGB rear suspension
Posted by: MGBV8
Date: July 06, 2013 06:03PM

I think it is best to stay off the bumpstops. Make more clearance and/or shorten them AND make them more compliant. I like the swiss cheeze idea. I may drill my shortened bumpstops.


DiDueColpi
Fred Key
West coast - Canada
(1308 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: bump stops, particularly on MGB rear suspension
Posted by: DiDueColpi
Date: July 11, 2013 10:15PM

There are quite a few vehicles old and new that use a bumpstop that is in constant contact.
Generally they have a pyramid, figure 8 or accordion shape to give a rising rate without shocking the suspension when contact is made.
My TGB uses ones that are 8" around and 10" high and they work really well.
Kits are available for RV's and trucks to enable them to handle heavy loads.
So no reason that the MGB shouldn't benefit as well. It will just need some experimentation.
It brings the old Austin elastic suspension to mind. Dead simple and it worked pretty well.
What about some sort of a folded lever assy. that would sandwich a rubber block in it's pinch area?
If the block had multiple mounting points it would be tuneable. You could even use multiple blocks in a row to provide a progressive rate.
A simple block change could adjust your spring rate from street to track day.
Probably a little more complex than needed but you know how the mind wanders.
Cheers
Fred


roverman
Art Gertz
Winchester, CA.
(3149 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: bump stops, particularly on MGB rear suspension
Posted by: roverman
Date: July 12, 2013 02:18PM

Or.... there are very small air bags/hmmm. Sites like "Baggit" list them,cheap/tunable. More than hot air, roverman.


MGBV8
Carl Floyd
Kingsport, TN
(4120 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB, Buick 215

authors avatar
Re: bump stops, particularly on MGB rear suspension
Posted by: MGBV8
Date: July 25, 2013 03:46PM

I"m still waiting for Curtis to tell us How much clearance he has on those rear bumpstops. Judging by the ride, it can't be much more than mine! ;)



MGBV8
Carl Floyd
Kingsport, TN
(4120 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB, Buick 215

authors avatar
Re: bump stops, particularly on MGB rear suspension
Posted by: MGBV8
Date: September 14, 2013 06:03PM

Okay, measured mine. Just under one inch before I hit the shortened bumpstops. Time to remove the lowering blocks.


tomsbad6
Tom Ahlstrom
Michigan
(129 posts)

Registered:
12/16/2012 03:16PM

Main British Car:
Triumph TR-6 347 Ford

Re: bump stops, particularly on MGB rear suspension
Posted by: tomsbad6
Date: September 29, 2013 11:55AM

A Carl I've got to say thank you your comment on bump stops it has haunted me for weeks it's had my brain going in circles you said quote keep it off the bump stops that's easier said than done on these lowered cars with very little travel I have 2 inches maybe more before I hit my bump stops which are very small the key to my cars traction is the rear end squatting digging and compensating to launch the car I noticed in some of my videos the car launches so hard it seems to rebound off the bump stops so I just keep thinking stay off the bump stops my bump stop bump stop adjustment is crucial to what direction the car goes you've had me thinking so this weekend I tested something new all they are is small shims clamped on the Springs that hit 1/2 inch before my car hits the bump stops I still have good movement so the car will hook up but I'm no longer rebounding off the bump stops when my shims hit with just two shams it adds approximately 20% to the spring rate by isolating coils but not affecting it anywhere else in its travel I spent the day on Saturday just doing some simple tuning at the racetrack I took my old war out drag radial's and turned them into toast testing I learned a lot my car no longer rebounds when he hits the bump stops I tried different amounts of shims and different sizes I believe I found the right combination the guys at the racetrack thought I was crazy with my homemade laser alignment tools and all different kinds of shims adjusting the car it ran very good I didn't bother to spray it it ran7.40 at 93 mph all day long on the old tires and no nitrous my new drag slicks will be here on Monday I have my rear till and bump stop height perfect I just have to move the toe about 1 inch left on the car any should go straight I'll see if I can post a video from behind the car notice how the car takes off when it leaves the launchpad and hits good old fashion asphalt my nitto tires love the Street but hate that launchpad we fix that on Monday signed keeping it off the bump stops thank you Carl PS I'm very sorry this doesn't help you leaf spring guys very much
b stop 2 002.JPG
b stop 2 003.JPG
b stop 2 001.JPG



Edited 1 time(s). Last edit at 09/29/2013 11:57AM by tomsbad6.


tomsbad6
Tom Ahlstrom
Michigan
(129 posts)

Registered:
12/16/2012 03:16PM

Main British Car:
Triumph TR-6 347 Ford

Re: bump stops, particularly on MGB rear suspension
Posted by: tomsbad6
Date: September 29, 2013 12:01PM



BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6069 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: bump stops, particularly on MGB rear suspension
Posted by: BlownMGB-V8
Date: September 29, 2013 04:44PM

Tom, I think conventional wisdom is that when launching you want the suspension to jack the body upwards to "plant" the tires and gain extra traction. No doubt you, Carl and others know a lot more about this than I do, but is there any way to make the TR6 suspension behave that way? Or maybe I should ask, is there any way to do it without totally destroying handling in the corners?

Jim


tomsbad6
Tom Ahlstrom
Michigan
(129 posts)

Registered:
12/16/2012 03:16PM

Main British Car:
Triumph TR-6 347 Ford

Re: bump stops, particularly on MGB rear suspension
Posted by: tomsbad6
Date: September 29, 2013 06:52PM

swing 002.JPG

I know this has nothing to do with bump stops and it is just a small part of the whole rear suspension picture IRS but this is why you want squat in the diagram you'll see point A wheel bearing center and point B trail arm pivot center point A is pushing point b in my car I made the two points closer together by 1 inch I move point A up 2 inches this changes the relative angle between the two with point a higher than point b it tries try to climb over it squatting the car compressing the Springs my spring rate loaded is 600 pounds per inch when the Springs compressed 2 inches the rate goes up and I have over 1800 pounds of spring load per side that load is driving the tires into the pavement solid axle cars depend on the weight transfer from the body of the car my car has that to but it is a secondary motion control completely by the differential and its ability to rotate the entire body of the car but the motion of the trail arm and the motion of the differential are not related in any way like in a solid axle car when I first started playing with this TR six I had never owned a British car but I fell in love with the smooth quick handling characteristics of that suspension I did not think it would ever drag race the stock characteristics include to really bad habits tire spin and wheel hop typical IRS it was not until I realized I basically had to motorcycle trail arms on the outside and a good old-fashioned rear axle in the middle all three parts separate in motion this is going to sound really stupid but in my head the most important connection between differential and the trail arms is timing the trail arms load up first and then the differential drops a car on top of them this is one of the most complicated automotive challenges I've ever faced and I've enjoyed every minute of it hopefully someday we can sit down in a bar have a few beers and I can explain all little details of why and how it works there is an added bonus to all this dragracing tuning the better it squats and digs going straight the better it turns with the throttle on another small bonus TR six toes in when it squats that makes a drag car go very straight it makes a road racer out turn the car next to them I worked all day on Saturday at the dragstrip trying to figure out how much inward toe is best the more told that I gave it in the straighter it went there has to be a sweet spot I have not found it yet


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6069 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: bump stops, particularly on MGB rear suspension
Posted by: BlownMGB-V8
Date: September 29, 2013 09:20PM

I'd enjoy that discussion Tom. Any chance you're going to Townsend? It's a different concept to be sure and I think I sort of see where you are going with it, just don't follow it too well.

Jim


tomsbad6
Tom Ahlstrom
Michigan
(129 posts)

Registered:
12/16/2012 03:16PM

Main British Car:
Triumph TR-6 347 Ford

Re: bump stops, particularly on MGB rear suspension
Posted by: tomsbad6
Date: February 05, 2014 09:30AM



MGBV8
Carl Floyd
Kingsport, TN
(4120 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB, Buick 215

authors avatar
Re: bump stops, particularly on MGB rear suspension
Posted by: MGBV8
Date: February 05, 2014 11:58AM

Jounce? Sounds British. That would be a big help if it is plug & play. Otherwise, increase clearance. My Camaro does not have bumps stops nor axle straps.



BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6069 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: bump stops, particularly on MGB rear suspension
Posted by: BlownMGB-V8
Date: February 05, 2014 12:25PM

Your Camaro is not designed for minimal ground clearance either. It has room for additional axle travel that the MGB does not. Plus the tubular shocks have an internal cushion or stop to limit downward travel of the axle that takes the place of the axle strap, which in the MG protects the Armstrongs.

So have you ever bottomed out the rear suspension in your Camaro? If you noticed that happening regularly then a bump stop might be a good idea. Your MGB can go the same way of course, take 'em off and see if you bottom out. The downside of that is, you might crumple the frame rail of the unibody before you decide you need the bump stop. Or not.

Jim


britcars
Phil Ossinger
New Brunswick, Canada
(344 posts)

Registered:
02/02/2009 07:58PM

Main British Car:
1977 MGB Roadster, Rover 3.5 ADVENTURE BEFORE DEMENTIA!

authors avatar
Re: bump stops, particularly on MGB rear suspension
Posted by: britcars
Date: February 13, 2014 10:10PM

My bumpstop was cut to 1 3/4" long, leaving 3 3/4" of axle travel before hitting. I have 1 1/2" lowering blocks. I can only remember once that the bump stop pedestal on the axle hit the bumpstop hard enough for me to feel it..........and it was VERY hard!

Phil
Bumpstop (Copy).JPG


mgb260
Jim Nichols
Sequim,WA
(2120 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: bump stops, particularly on MGB rear suspension
Posted by: mgb260
Date: February 13, 2014 10:56PM

Phil,I would remove the pedestal to give even more room. Especially with 1 1/2" lowering blocks.



Edited 1 time(s). Last edit at 02/13/2014 11:12PM by mgb260.


Sorry, only registered users may post in this forum.