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Rear Tube Shock Conversions

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Andy Blackley

Andy Blackley

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The latest issue of Moss's "British Motoring" has an article on rear tube shock conversion. There appears to be at least three kit options available:
TRF TR250/6 Glove Box Companion, Page 74 shows the two most common: https://zeni.net/trf/TR250-6/index.php?menu=T&page=74

And there is this one from Blind Moose: https://www.blindmoosefab.com/rear_shock.htm
I am inclinded to the latter and wonder if anyone has used it.
The Mr. Runyon on TRF page says that he would be concerned about the direct bolt on conversion because of the stesses (some guy ripped the cross memeber off, and so on). If the shock does not bottom then I do not see how the stress would be worse then the stock arrangement. If either a lever shock or a tube shock reached full travel, and the rubber bump stop is missing, then there would be considerably more force transmitted to the two mounting bolts. But if the rubber stop is there the bottoming force does not move through the shock and the mount at all.
Thoughts?
 
I'm no engineer but my gut tells me the typical tube shock conversion may be asking for trouble. The stock lever shock transmits force perpindicular to the mounting bolts because it swivels at the top of the shock chambers. The tube shock conversions create a large (non moving) lever arm which transmits shock force at an angle to the mounting bolts. There is one tube shock setup I do like which only seems to be available from Moss Europe. It has a three position mount; the two standard shock mounting bolts plus a mount to the bump stop on the frame. This would be my choice for conversion. Check out the photo and look closely at the mounting points of the conversion.
 

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Hi Andy,

I have the VB 5-6025 kit. This comes with KYB shocks & is a direct bolt on replacement. It's design allows up to a 215 size tire on a 7" wide rim. The Blind Moose design is similar but I have never seen one in person. Revington also makes a replacment that fits inside the spring, great for those who use a rear sway bar. As all of there products , it's pricey.

I do not think the bolt through has any advantages but does have the disadvantage of having to drill through the body shell . In my opinon unnecessary & may transfer more vibration through the body. The lever arm bump stop is gone but unless your car is sitting unusually high on it's springs or you do some occasional off roading , it's unlikely you will exceed the shock travel. I have heard some converts complain of chassis cracks & bolt mount failure on the VB/Moose design, but I'd bet the metal was weak or rusted before. I don't see any more stress put to these points than before & I have not had any failures in over 4 years of hard driving.

I personaly think the ride is far superior. There is a quietness & more modern firmness that are immediatly evident. These perform best with slighty stiffer springs but any set-up will bennifit.There are staunch lever enthusiasts who will state that simple valve changes & altering oil vicosity will make levers perform well. The bump & rebound qualities of a modern gas shock is simply better. The gas & more modern oils react & surpress better & faster, yielding superior wheel control.
 
Correct me if I am wrong, but I think that the one-piece sold through various vendors and comes with the KYB shock is manufactured by Brit Parts Northwest. At least that is what they told me themselves. I have that conversion on my TR6 except that I changed the shock to a Spax adustable. I seems extremely stable to me. I asked around a variety of sources and no one had any real complaints. It is a snap to install. Works very, very well. I use BPNW's comp springs and they lowered the rear of the car 1", which I wanted. The geometry of the rear alignment did not change one iota. Good people and knowledgeable.

Bill
 
I've heard the same from BPNW, & my dealing with them have all been positive. These guys like what they do.
Same results with the lowering springs, no rear wheel alignment needed, car turns like a go kart.

Bill if you could pass along the Spax part # I'd appreciate it.
 
I've been using the Victoria conversion now for three or four years. They bolt into the same holes as the levers did, so there is no issue in that regard. Just this afternoon I had the rear wheels off to grease the rear ujoints and inspected the mounts; as always, they are still tight. Can give the highest recommendation to this part.
 
71Tr: Man, that Moss one looks nice and beefy.
Thanks for the replies everyone.
 
71Tr,

Is that your frame? Wow! Sure looks good! I see you're in Charlotte. I'm in Weddington. Are you in the TCOC? If so, we've probably met. I let my membership expire though. I need to get a check in to Tony.
 
Roadstr6,
Nope that's not my frame but I did model my rear diff mount reinforcements after this. Boxed in the mounts, gusseted the forward tower where the springs mount and added the 1-inch bar crossmembers between the diff bridges, very pleased with the results. I'm not a TCOC member but live just up the road from you in south Charlotte near Park Rd. Shop Ctr.
 
71Tr,

I agree that the shock conversion is the best I have seen. I went to the Moss Europe web site, but they state "The brackets used in this conversion are based on our very popular - and successful type 2 kit, TT3225X, which utilises the lever arm mounting points, that has stood the test of time. However, these conversion brackets, TT3225TUV, are of a much heavier and stronger construction. They also have an extra mounting point for them to be located directly to the wheel arch (which will require drilling. Please contact your nearest branch for details. (***These bracket kits are fitted to the inner arch at the same height as the tyre, care must be exercised to ensure clearance during suspension travel. If excessive negative camber is already used, this must be reset before use to ensure clearance)." and "These are one piece brackets that bolt to the lever arm mounting points on the chassis, and fit outside the inner wheel arch. They are easy to install, but if the body shell is not correctly aligned to the chassis, certain combinations of tyre and wheel sizes may cause problems. Please contact your nearest branch if in doubt. (***These bracket kits are fitted to the inner arch at the same height as the tyre, care must be exercised to ensure clearance during suspension travel. If excessive negative camber is already used, this must be reset before use to ensure clearance)." for two types of their units. Both kits reference attachment to the inner fender arch, buy not the third frame attachment shown in your attachment. Could you please clarify?

Thanks.

Alan
 
Tube shock conversion is good. Which conversion is best? I think you would have to test all of the conversions to know which one is best. My conversion has less than 600 miles on it while the OEM got near 75k before they failed. My tube shocks are working extremely well; however, I think if I replaced the OEM's with rebuilt ones, I would think they were great too.
 
I guess that's my question, in a round about way. Since rebuilt units are available, should that be the normal route to follow for a street driven TR6? I have no aspirations to drive really hard, but do want to have a nice smooth, but steady ride.
 
Mitch,
The Spax label says "Spax 28" and the body has GK5 stamped into the housing. I guess you can reference this off their website. I like the Spax because they are adjustable very easily with a flat-bladed screwdriver from the bottom rear, unlike the Koni shocks which are a pain to adjust (I have Koni's on the front).

Bill
 
Thanks Bill,

We seem to be building similar cars. So far the KYB's have performed very well but when it's time to replace them I would like the option of adjustment. I would just be cautious not to set these to stiff. Let the springs add stiffness & the shock control the spring.

Thanks for the numbers.
 
alansimon,
I looked thru the Moss Europe catalog and my findings were identical to your's, no reference to the three pronged mount. I must have been mistaken. The picture I posted was from a gentleman in Europe restoring a six and I just assumed the unusual parts came from Moss Europe. I've looked thru the websites of Rimmer, Racetorations, Revington etc. and cannot find this particular application. It's out there but I'm not sure whom is carrying it. Will keep you posted.
 
[ QUOTE ]
I guess that's my question, in a round about way. Since rebuilt units are available, should that be the normal route to follow for a street driven TR6? I have no aspirations to drive really hard, but do want to have a nice smooth, but steady ride.

[/ QUOTE ]

I would have to say the only really smooth part of these cars is the style. /ubbthreads/images/graemlins/wink.gif
 
I have the second kit shown in your first attachment, same as TR6Bill and TRboost.
I have used this for 8 years now (I think) with no problems. I also use Spax gas shocks as I felt the KYB were too soft with my upgraded springs.
The mounts bolt into the original positions and you are not transmitting suspension forces into sheetmetal, which seems to me to be a bad idea.
I have no comment on the Blind Moose kit as I have never seen it.
Simon.
 
Has anyone ever done a rear tube shock conversion on any of the solid axle TR's?? Would there be any advantage to it??
 
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