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BN2 axle travel

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Dave Russell

Dave Russell

Yoda - R.I.P
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BN2 axle travel

The early Healeys when compared to the late BJ8, had limited rear axle travel as compared to the later BJ8's. The increased axle travel of the late models somewhat improved the ride. I have about 1.5" of rebound travel with the body at normal ride height.

Has anyone ever considered modifying the earlier rear frames to dip down some more to increase the rebound travel? It would seem that this would be a major improvement in ride for the earlier cars. The very thin top out bumper is practically useless.

Are folks reluctant to disturb the originality of the stock design or is the advantage just not considered to be worth the extra work or is the existing limited rebound, topping out & axle hop just not considered that much of a problem.

How much do substitute telescopic tube stocks inprove rear axle control, if any, & how successful is this conversion?

How much would stiffer rebound valving on the stock lever shocks help the stock situation?

Tired of axle hop & frame top out when going over the slightest dip at any reasonable speed. Open to any suggestions. Interested in any experiences or thoughts about this. Thanks for any help.
D
 
Dave:

I'm a big fan of tube-shocks, at least on Sprites, but I have only my own empirical evidence of success.
Honestly, it's hard to see why tubes would be any better: the technology is basically the same. All the race-Spridgets that I see have tube-shocks.
I have observed that piston-stroke travel on lever shocks seems much shorter, due to the more compact design. Maybe the longer travel of pistons in tube-shocks is easier to control? Not sure.
In Spridgets, the lever shocks are dual pistons, but the total displacement still seems less than the tube shocks: that may account for the improved dampening in tubes (yes, I have cut these shocks apart to study them...I was curious about their construction).
In any event, the fixed-rate, bottom-of-the-line Monroe gas tube-shocks (about $18 USD each in my local discount auto parts store) were *much* better than the NOS lever shocks that were previously on my car. The "new" NOS lever shocks were freebies from a buddy, but they normally cost about $120 USD each. The "new" levers were hardly better than the well-used originals. The minute I installed the tubes, the axle-hop disappeared. It was like night and day.
The question about bottoming on your car is interesting. My car has tubes all-around and of course, the car has been lowered quite a bit. This year, I have had to raise the nose a bit, because the I am bottoming the front suspension, even with race-springs in the front . A friend has suggested that I install adjustable front tube-shocks, so I can stiffen the compression (thus resisting bottoming...allowing me to re-lower the car). I'm hoping adjustabilty may allow a setting that will emulate a "rising rate" sort of effect. This might be a good strategy for the rear of your car too. Adjustable SPAX or Carerra tube-shocks are about $100 each.
The idea of frame modification (to allow more travel) is intriquing, but seems very radical. The tube-shocks modification is easily reversible and I'd try that first. Also, the idea of raising the rear (to improve travel distance) is probably not appealing to you (it isn't to me either). Nevertheless, raising the rear an inch or so might be a very simple way to eliminate the bottoming. I doubt this would really spoil the "look" of your car too much. Softer, longer bump-stops might be an idea too.

Not sure if this is useful, but a page describing the addition of tube-shocks to the front of my car can be seen here:

https://npmccabe.tripod.com/spritetubeshock.htm
 
[ QUOTE ]
Dave:
The idea of frame modification (to allow more travel) is intriquing, but seems very radical. The tube-shocks modification is easily reversible and I'd try that first. Also, the idea of raising the rear (to improve travel distance) is probably not appealing to you (it isn't to me either). Nevertheless, raising the rear an inch or so might be a very simple way to eliminate the bottoming. I doubt this would really spoil the "look" of your car too much. Softer, longer bump-stops might be an idea too.


[/ QUOTE ]
Thanks for the suggestions. I guess I didn't make the problem too clear. On the Healeys, the rear frame goes under the axle & severely limits the rebound travel which is less than two inches now. As it is, raising the rear only decreases the rebound travel even more. Thus the consideration to lower the frame where it passes under the axle, ala BJ8, where they dipped the frame section under the axle to gain more REBOUND travel. I think that they then used part of this additional clearance to raise the car, & again decrease the rebound travel, at the expense of minimal rebound travel. When the axle contacts the frame on rebound, it just lifts the axle & wheel. TOPPING is actually the problem, not bottoming. There is only less than two inches of topping travel available. A problem peculiar mostly to big healeys. Makes quite a topping thump when going over bumps. There is a three inch compression bumper which works nicely for compression, but the rebound bumper is a tiny piece of rubber, between the axle & the frame which runs under it, that does nothing to decrease topping impacts. Most car designs have several inches of rebound travel, after all a wheel must be able to travel both up & down in order for the ride to be decent. Not so with the Big Healeys. The wheel is only free to travel up.
D
 
Dave--

As you know, I installed Udo Putske's Bilstein kit front and rear. There is much less tendency to "bounce-steer" while in turns, esp. on rough roads but I can't address your question about the rear axle travel.
 
Michael,
I believe that I recently read of you having trouble with the shock hardware coming loose while on your conclave trip. Any updates or words of wisdom on this?
D
 
[ QUOTE ]
Michael,
I believe that I recently read of you having trouble with the shock hardware coming loose while on your conclave trip. Any updates or words of wisdom on this?
D

[/ QUOTE ]

Dave--

The Putske shock kit is designed so that a bolt passes through the bottom end of the shock from inboard to outboard and fastens into a blind hole in the receiver which is bolted onto the leaf spring. Apparently the components were dimensioned for a stock rearend setup, whereas I had an already-installed DW anti-roll bar, and the person who installed the shocks for me tried to make it happen by passing the bolt through the shock and then through the link for the anti-roll bar, "sandwiching" it between the outer face of the shock and the inner face of the receiver. However, this caused the link to be slightly angled and to bind on the bolt and as the rear suspension worked under driving load the link undoubtedly caused the bolt to turn and back out of the receiver.

I first noticed that there was a problem before I left Maryland for Conclave last June when I was servicing the car prior to departure--I saw that the bolt for the right rear shock was backed out, did not really analyze the cause but instead figured it had not been properly torqued and simply retightened it. Several hundred miles into the trip I noticed that it had happened again, and when I visited a friend in Duluth, MN I made use of his garage, got under the car, trimmed about 3/8" off of the inboard face of the receiver to allow for the link's thickness and because the original bolt was slightly buggered I put in a new bolt which I set in Blue Locktite, figuring that this would solve the problem.

Less than 200 miles later the bolt had again backed out. We were someplace in western Minnesota or Eastern North Dakota and I found an auto parts shop with a machine shop, borrowed their jack, removed the right rear receiver and had them through-drill the receiver slightly oversize so that I could pass a bolt with a long shoulder all the way through and locknut it on the outboard face of the receiver. Just to make sure that this would not come apart I applied purple ("forever") locktite. The offending piece has given no more problems.

Though this problem would not have happened had the shocks been properly installed to begin with, I would nevertheless recommend to anyone who uses the Putske kit to consider modifying the receiver as I did--through drill it and use a bolt with a nut versus just turning into the threaded receiver. There's no downside to doing so and makes for a more secure mounting.

Hope this is longwinded explanation is clear.
 
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Dave,have you seen any good BJ8's for sale in your area??.---Keoke /ubbthreads/images/graemlins/laugh.gif
 
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