getting that bouncy feeling rear tube conversion on MGB GT
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Tito
- Active Member
- Posts: 28
- Joined: Fri Dec 14, 2007 9:45 pm
getting that bouncy feeling rear tube conversion on MGB GT
Ok so I converted the rear of my gt to use the tube shocks that I got from a Vendor on ebay. The ride was impossibly bouncy and the rear shock seems to be overpowering the fronts by a wide margin. I switched those out to a Monroe Sensa trac 5877 and that softened it up a bit but its still pretty harsh. Would a front tube conversion fix this issue or should I just change them back?
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kiwimark
- Active Member
- Posts: 119
- Joined: Mon Feb 18, 2008 6:46 pm
- Vehicles Owned: 1958 MGA Coupe
1969 MGB Gt
1995 Ford Bronco - Location: Del Mar Ca
Rear Shock Conversion.
Hi
all the MG owners that I talked to that had coverted their cars to tube shocks have changed them back to the lever arms. Most of the racing MG's that I have seen, use an uprated version of the lever arm as well. The drivers unanomously seem to think they are better than tube for all situations. The only advantage I can see to tubes is that they in most cases are cheaper to replace. I have tube shocks on my BGT that came with the car when I bought it and I find them acceptable, just. It may be because the BGT is a bit heavier than the roadster but I am thinking along the lines of lever arm replacement with heavy duty valves to improve the ride. One of our club members has a BGT fitted with a ford 302 and he tried out tubes in the front in the theory that the extra weight of the engine would warrent the extra help. He went back to lever arms as he found the tubes pretty horrible. The only tube shocks I could really see working are those with adjustable valving for both compression and rebound as used in rally cars. If you have a bottomless wallet they might work ( they are really expensive )but would require a lot of tuning to get them right. I would stick with the stock shocks and play with the valving as these were taken into account when the car was designed. My old midget went way better after I cleaned and greased the rear spring leaves. The grease allowed the leaves to slide over each other better and it gave the car a more progressive and smoother action in the rear.
regards
Mark
all the MG owners that I talked to that had coverted their cars to tube shocks have changed them back to the lever arms. Most of the racing MG's that I have seen, use an uprated version of the lever arm as well. The drivers unanomously seem to think they are better than tube for all situations. The only advantage I can see to tubes is that they in most cases are cheaper to replace. I have tube shocks on my BGT that came with the car when I bought it and I find them acceptable, just. It may be because the BGT is a bit heavier than the roadster but I am thinking along the lines of lever arm replacement with heavy duty valves to improve the ride. One of our club members has a BGT fitted with a ford 302 and he tried out tubes in the front in the theory that the extra weight of the engine would warrent the extra help. He went back to lever arms as he found the tubes pretty horrible. The only tube shocks I could really see working are those with adjustable valving for both compression and rebound as used in rally cars. If you have a bottomless wallet they might work ( they are really expensive )but would require a lot of tuning to get them right. I would stick with the stock shocks and play with the valving as these were taken into account when the car was designed. My old midget went way better after I cleaned and greased the rear spring leaves. The grease allowed the leaves to slide over each other better and it gave the car a more progressive and smoother action in the rear.
regards
Mark
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Steve Simmons
- Site Admin
- Posts: 4106
- Joined: Thu Sep 07, 2006 9:45 pm
- Vehicles Owned: .
1937 MG SA Saloon
1946 John Deere AN
1949 MG TC
1953 MG TD
1958 MGA Roadster
1959 Morris Minor 1000
1965 MGB
1967 MGB GT (UK-Spec)
1967 Austin Healey 3000 BJ8
1969 MGC GTS - Location: Co-Nay-Ho Valley
- Contact:
Hi Tito, I know you just put time and money into your tube shock conversion but I have to agree with kiwimark. The problem is that the MGB chassis was never designed to fit a tube shock, and therefore you cannot achieve an optimal mounting angle for them. This can result in odd load angles which will prevent the shocks from working properly and also wear them out quicker.
Additionally, car manufacturers spend a lot of time researching and developing the proper shocks for each specific vehicle they manufacture. There has never been such research done for MGBs and therefore no tube shock exists which has the perfect characteristics for the car.
It's true that once you get past the cost of the conversion kit, tube shocks will be cheaper to replace when that time comes, but they lose this advantage when you consider that most lever shocks will outlast a tube shock by several times. In fact, rebuilt lever shocks from Worldwide come with a LIFETIME guarantee against leaks or failures. You can't get that kind of guarantee from any tube shock.
If you need adjustable shocks, you can get adjustable lever shocks from Worldwide as a special order. Honestly the softer you run the rear end on your B, the better off you will be. Many people make the mistake of stiffening the rear but this results in a really "hoppy" rear end on anything but the smoothest roads. The live axle need a compliant rear suspension to keep it under control.
Definitely do NOT put tube shocks on the front end unless you're converting to a completely modern suspension, such as a coil over kit from Hawk, Guzman, Fast Cars, etc. The tube shocks will never mount properly on the stock suspension parts and it's just added weight. If you need convincing, see here: http://www.motorheadltd.com/tubeshock.htm
The best thing you can do is to send all four of your levers to Peter at Worldwide and install his rebuilt and uprated units. You will never have to touch them again. He can install heavy duty valves if you need something a little stiffer. See here: http://www.nosimport.com/shoxcatalog.htm
Additionally, car manufacturers spend a lot of time researching and developing the proper shocks for each specific vehicle they manufacture. There has never been such research done for MGBs and therefore no tube shock exists which has the perfect characteristics for the car.
It's true that once you get past the cost of the conversion kit, tube shocks will be cheaper to replace when that time comes, but they lose this advantage when you consider that most lever shocks will outlast a tube shock by several times. In fact, rebuilt lever shocks from Worldwide come with a LIFETIME guarantee against leaks or failures. You can't get that kind of guarantee from any tube shock.
If you need adjustable shocks, you can get adjustable lever shocks from Worldwide as a special order. Honestly the softer you run the rear end on your B, the better off you will be. Many people make the mistake of stiffening the rear but this results in a really "hoppy" rear end on anything but the smoothest roads. The live axle need a compliant rear suspension to keep it under control.
Definitely do NOT put tube shocks on the front end unless you're converting to a completely modern suspension, such as a coil over kit from Hawk, Guzman, Fast Cars, etc. The tube shocks will never mount properly on the stock suspension parts and it's just added weight. If you need convincing, see here: http://www.motorheadltd.com/tubeshock.htm
The best thing you can do is to send all four of your levers to Peter at Worldwide and install his rebuilt and uprated units. You will never have to touch them again. He can install heavy duty valves if you need something a little stiffer. See here: http://www.nosimport.com/shoxcatalog.htm
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Tito
- Active Member
- Posts: 28
- Joined: Fri Dec 14, 2007 9:45 pm
going back
Well after switching them out to progressively softer and softer shocks I totally agree with you and will be changing them back on Weds. I do not like the sudden lane change when I hit a bump. Yes I did see Bill G's and Fast cars set ups and I will eventually do that. They are a little on the spendy side so I will wait to do it. Right now I am working on getting it running as best as possible so that I can use it as a daily driver. Now if only I can find a good AC cheap! 
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Steve Simmons
- Site Admin
- Posts: 4106
- Joined: Thu Sep 07, 2006 9:45 pm
- Vehicles Owned: .
1937 MG SA Saloon
1946 John Deere AN
1949 MG TC
1953 MG TD
1958 MGA Roadster
1959 Morris Minor 1000
1965 MGB
1967 MGB GT (UK-Spec)
1967 Austin Healey 3000 BJ8
1969 MGC GTS - Location: Co-Nay-Ho Valley
- Contact:
Don't be so quick to get rid of the stock suspension. MGBs were never known for handling faults, and in new condition the suspension on your car may really surprise you in terms of performance and comfort.
The Fast Cars setup and other conversion kits can offer better than stock performance, but they take away a part of what makes the MGB what it is. If you're seeking high levels of performance, it may be cheaper to buy a higher-end base car than to completely upgrade and modify an MGB!
My recommendation is to return the car to as near factory specs as possible using Peter's shocks. Superflex bushings will sharpen response and a slightly lower profile and wider tire will increase grip. My size of choice for performance is 195/60R15 or 195/65R14.
The Fast Cars setup and other conversion kits can offer better than stock performance, but they take away a part of what makes the MGB what it is. If you're seeking high levels of performance, it may be cheaper to buy a higher-end base car than to completely upgrade and modify an MGB!
My recommendation is to return the car to as near factory specs as possible using Peter's shocks. Superflex bushings will sharpen response and a slightly lower profile and wider tire will increase grip. My size of choice for performance is 195/60R15 or 195/65R14.
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Tito
- Active Member
- Posts: 28
- Joined: Fri Dec 14, 2007 9:45 pm
lesson learned
Well I changed them back out to the armstrong units(mine were still in very good condition) and the difference is like night and day. I no longer hit my head on the ceiling whenever I go over a pebble. The car is now smooth controllable and a joy to drive! I did look at the leaf springs and they are in very good condition as well. Now to tend to the other 200 things that I want to do to "improve" the car! 
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JerryB
- Active Member
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- Joined: Thu Sep 27, 2007 10:39 am
- Location: Corner Walk and Dont Walk...92707
Shocking developments.........!!
Tito Posted:
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Ok so I converted the rear of my gt to use the tube shocks that I got from a Vendor on ebay. The ride was impossibly bouncy and the rear shock seems to be overpowering the fronts by a wide margin. I switched those out to a Monroe Sensa trac 5877 and that softened it up a bit but its still pretty harsh. Would a front tube conversion fix this issue or should I just change them back?
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Just because something fits in the allotted space doesnt mean it will work right. The 5877 Monroe was designed for a 3300 pound Chrysler Corp car with around a 220 pound rear spring rate. the shock in that application probably has a motion ratio of maybe .8. That means the shok traveled less than the live axle travel on bump and rebound.
What all this above means is when a 250 pound person jumps up and down on a trampoline the trampoline "moves" with his body as he jumps and does not jar the jumper. Now take a 150 pound person and thicken the trampoline material to double the thickness of the "mat" so as to make it twice as stiff. Now the 150 # person has a really hard time banging his feet every time he bounces....and it hurts his legs.
The shock MUST be compatible with the spring rate and motion ratio of youre car.
Get it?
The tube shok that you put on (either the front or the back) MUST HAVE compatibility with your spring rate at the rear or the front springs. In addition, the shock MUST be mounted so as to have the correct motion ratio that the shock wants to see. Perfectly vertical mounting might not work. To find the correct mounting postion and the correct shock valving takes either a lot of trial and error or a shock dyno. It either that or jar your teeth out.
Working with only a pencil and paper, you can figure the weight of the car on each corner, the motion ratios availiable in postioning the shock and the spring rate on that corner. Comparing those figures with known figures of the "donor car shock" might produce the desired effect.
The broader issue is that shocks for very light cars and that fit in limited packaging areas are expensive. Koni and Spax for example...$125 each and you still have to determine placement and angle. And yes the bump is adjustable so you have some latitude.
Short answer and it was said above.....
If the lever shocks dont leak, get some 20 or 30W hydraulic oil and flush and recharge or have them resealed and then fill.
--------------------------------------------------------------------------------
Ok so I converted the rear of my gt to use the tube shocks that I got from a Vendor on ebay. The ride was impossibly bouncy and the rear shock seems to be overpowering the fronts by a wide margin. I switched those out to a Monroe Sensa trac 5877 and that softened it up a bit but its still pretty harsh. Would a front tube conversion fix this issue or should I just change them back?
==========
Just because something fits in the allotted space doesnt mean it will work right. The 5877 Monroe was designed for a 3300 pound Chrysler Corp car with around a 220 pound rear spring rate. the shock in that application probably has a motion ratio of maybe .8. That means the shok traveled less than the live axle travel on bump and rebound.
What all this above means is when a 250 pound person jumps up and down on a trampoline the trampoline "moves" with his body as he jumps and does not jar the jumper. Now take a 150 pound person and thicken the trampoline material to double the thickness of the "mat" so as to make it twice as stiff. Now the 150 # person has a really hard time banging his feet every time he bounces....and it hurts his legs.
The shock MUST be compatible with the spring rate and motion ratio of youre car.
Get it?
The tube shok that you put on (either the front or the back) MUST HAVE compatibility with your spring rate at the rear or the front springs. In addition, the shock MUST be mounted so as to have the correct motion ratio that the shock wants to see. Perfectly vertical mounting might not work. To find the correct mounting postion and the correct shock valving takes either a lot of trial and error or a shock dyno. It either that or jar your teeth out.
Working with only a pencil and paper, you can figure the weight of the car on each corner, the motion ratios availiable in postioning the shock and the spring rate on that corner. Comparing those figures with known figures of the "donor car shock" might produce the desired effect.
The broader issue is that shocks for very light cars and that fit in limited packaging areas are expensive. Koni and Spax for example...$125 each and you still have to determine placement and angle. And yes the bump is adjustable so you have some latitude.
Short answer and it was said above.....
If the lever shocks dont leak, get some 20 or 30W hydraulic oil and flush and recharge or have them resealed and then fill.