Moderator Curtis Jacobson Portland Oregon (4576 posts) Registered: 10/12/2007 02:16AM Main British Car: 71 MGBGT, Buick 215 |
bump stops, particularly on MGB rear suspension
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. (3188 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
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.
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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
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
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MGBV8 Carl Floyd Kingsport, TN (4511 posts) Registered: 10/23/2007 11:32PM Main British Car: 1979 MGB Buick 215 |
Re: bump stops, particularly on MGB rear suspension
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.
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DiDueColpi Fred Key West coast - Canada (1365 posts) Registered: 05/14/2010 03:06AM Main British Car: I really thought that I'd be an action figure by now! |
Re: bump stops, particularly on MGB rear suspension
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. (3188 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
Or.... there are very small air bags/hmmm. Sites like "Baggit" list them,cheap/tunable. More than hot air, roverman.
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MGBV8 Carl Floyd Kingsport, TN (4511 posts) Registered: 10/23/2007 11:32PM Main British Car: 1979 MGB Buick 215 |
Re: bump stops, particularly on MGB rear suspension
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! ;)
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MGBV8 Carl Floyd Kingsport, TN (4511 posts) Registered: 10/23/2007 11:32PM Main British Car: 1979 MGB Buick 215 |
Re: bump stops, particularly on MGB rear suspension
Okay, measured mine. Just under one inch before I hit the shortened bumpstops. Time to remove the lowering blocks.
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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
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
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
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BlownMGB-V8 Jim Blackwood 9406 Gunpowder Rd., Florence, KY 41042 (6468 posts) Registered: 10/23/2007 12:59PM Main British Car: 1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS |
Re: bump stops, particularly on MGB rear suspension
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
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 (6468 posts) Registered: 10/23/2007 12:59PM Main British Car: 1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS |
Re: bump stops, particularly on MGB rear suspension
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
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MGBV8 Carl Floyd Kingsport, TN (4511 posts) Registered: 10/23/2007 11:32PM Main British Car: 1979 MGB Buick 215 |
Re: bump stops, particularly on MGB rear suspension
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.
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BlownMGB-V8 Jim Blackwood 9406 Gunpowder Rd., Florence, KY 41042 (6468 posts) Registered: 10/23/2007 12:59PM Main British Car: 1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS |
Re: bump stops, particularly on MGB rear suspension
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 (346 posts) Registered: 02/02/2009 07:58PM Main British Car: 1977 MGB Roadster, Rover 3.5 ADVENTURE BEFORE DEMENTIA! |
Re: bump stops, particularly on MGB rear suspension
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mgb260 Jim Nichols Sequim,WA (2461 posts) Registered: 02/29/2008 08:29PM Main British Car: 1973 MGB roadster 260 Ford V8 |
Re: bump stops, particularly on MGB rear suspension
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. |