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TR4/4A Coil-over suspension upgrade
- Thread starter shoopal
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Tybalt
Jedi Warrior
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Operating on the assumption you are talking TR4A with IRS and that by coilover you mean adjustable spring perches fitted to the damper such that spring preload and vehicle ride height can be altered, I am not aware of one for front or rear on the TR4A/5/250/6 that can be readily purchased. Revington TR offers an rear damper kit that uses a telescopic damper with top mounts added to the frame by welding them in and lower mounts added by modifying the trailing arm and fixing them in place with fasteners. The damper then runs up through the middle of the rear spring.
It would probably easy enough to come up with an adjustable perch set for the front. On the rear probably not so easy as both the top and bottom of the springs are essentially in a well and adjusting spring perch location would require removal in all likelihood.
Here's a link to one of the Revington rear damper kits, it's one of three different versions offered. This one uses polyurethane bushings, the other two use spherical bearings in the lower mounts.
https://www.revingtontr.com/product/rtr3003spk/name/damper-conversion-kit-rear-tr4a-6
Overall, the quality of the kit is pretty good but I did not care for the fasteners supplied with the kit for attaching the lower mount plates to the trailing arm. I swapped them out for some MS24694 screws in the same diameter but don't remember which length fastener I used. This allowed the fasteners to be installed with no threads rubbing against the through holes in the trailing arm. This also required that I redo the countersinks in the mount plates since the countersink angle was different, but by the same token it minimized the chances of what we call "knife edging" bore of the hole at the bottom of the countersink.
It would probably easy enough to come up with an adjustable perch set for the front. On the rear probably not so easy as both the top and bottom of the springs are essentially in a well and adjusting spring perch location would require removal in all likelihood.
Here's a link to one of the Revington rear damper kits, it's one of three different versions offered. This one uses polyurethane bushings, the other two use spherical bearings in the lower mounts.
https://www.revingtontr.com/product/rtr3003spk/name/damper-conversion-kit-rear-tr4a-6
Overall, the quality of the kit is pretty good but I did not care for the fasteners supplied with the kit for attaching the lower mount plates to the trailing arm. I swapped them out for some MS24694 screws in the same diameter but don't remember which length fastener I used. This allowed the fasteners to be installed with no threads rubbing against the through holes in the trailing arm. This also required that I redo the countersinks in the mount plates since the countersink angle was different, but by the same token it minimized the chances of what we call "knife edging" bore of the hole at the bottom of the countersink.
For the rear...I custom made a scenario with adapters and some welding where the shockers fit inside the coil springs, not a true coil over, as the top mount of the shocker has to be offset slightly to clear the standard body unless there is some minor alterations done to the immediate area.
Use of true coil overs would entail more structural alterations to the body to accomodate the top mounts. You would still need an adaptor fitted to the bottom of the shockers to lengthen the shocker travel as the coil length is too short for an effective shocker.
Some guys would say that the shockers are easier and better fitted further out on a custom made bracket. I wanted a neater look.
Use of true coil overs would entail more structural alterations to the body to accomodate the top mounts. You would still need an adaptor fitted to the bottom of the shockers to lengthen the shocker travel as the coil length is too short for an effective shocker.
Some guys would say that the shockers are easier and better fitted further out on a custom made bracket. I wanted a neater look.
Foura
Jedi Hopeful
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I am one of those "some guys" who believe that mounting the shock at the back of the trailing arm, as Triumph did on the 2000/2500 saloons, is the best solution. It gives longer travel and does not require drilling or welding of parts that are 50+ years old. I used the 3 piece bracket that Malbaby mentions. https://mossmotors.com/triumph-tr2-3-4/suspension-steering/rear-tube-shock-conversion-kits
This mounts through the wheel well and back to the original lever arm mount, gives a wider choice of shocks and the longer travel allows the use of a softer shock while still giving good control.
My 4A has done about 25,000 miles on indifferent roads here in Oz with no problems. Shoopal, there are several threads on this and other forums on this topic. Well worth some research.
This mounts through the wheel well and back to the original lever arm mount, gives a wider choice of shocks and the longer travel allows the use of a softer shock while still giving good control.
My 4A has done about 25,000 miles on indifferent roads here in Oz with no problems. Shoopal, there are several threads on this and other forums on this topic. Well worth some research.