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Triumph TR6 - Suspension Advise Wanted

I'm planning on rebuilding the suspension and considering the bolt-on KYB rear gas shock kit sold in Victoria British. Does anyone have experience with this unit, or am I better off trying to modify the lever shocks? I have 205 tires, and hopefully they will not interfere with them. I'm also considering using the heavy duty springs (not competition) instead of stock, and poly bushings. Your recommendations/warnings are appreciated.
DA Alesandro

I like the polyurethane bushings and the heavier springs part. I am unsure on the KYB setup you mention. On the plus side, it appears to bolt to the shock mounts so even though it is a circuitous route for the load path, it winds up in the right places (many earlier tube shock conversions were sandwich mounted to the sheet metal, lots of bad stuff going on there). On the down side, it also appears that it could potentially have a clearance problem with 205 width tires. I'd ask the seller and/or maker of the kit about that before purchase.

As for the lever shocks, they work reasonably well and I have stuck with them on all British cars that I have had save for one MGB where I put Konis on the rear. Truth be known, it didn't make much difference on that car. On the other hand, I am somewhat intrigued by the RevingtonTR rear tube shock kit and adjustable rear anti-roll bar. I just might have a candidate for that setup. It involves some welding and I've thought about taking a TR250 that I have (a sad example of one, but it is fairly complete and it does have a surrey top) and using it as a base for a vintage racer/solo car. If I go that route, the tub will come off the frame for some much needed work and welding can be done then with no problem.
SteveP

DA
I have the KYB shock conversion you speak of
and it is fantastic! I also have a wider tire than yours , 215/65 R15 and there is no problem with rubbing. New springs are a must as are poly bushings for the trailing arms.
Grease them well with silicone based grease and don't
do the final tightening until the car is back together
and fully loaded. Better yet, go for a complete four
wheel alinement.
Good luck,
Christopher
Christopher Trace

Thanks for your comments Christopher & Steve. I will likely start this job around the end of Summer. I intend to go for the four-wheel alignment when it is finished.
Dan A

Gentlemen: I must ask at the risk of appearing dumb (I'm only iignorant); HOW does the change in shock absorbers improve handling of the vehicle? I thought the function of the shock absorbers is to absorb the shocks experienced by the car when travelling over uneven terrain (poholes, bumps etc.) I can't figure out how they might enhance cornering ability. I'm obviously not an engineer. Understanding the functionality of the shocks may help me decide whether it's a conversion I want to make...I do want improved cornering ability. Hope this isn't TOO ELEMENTARY for this forum. Any references to materials otherwise posted that adresses the question is welcome.
J.T. Cruz

The question is a good question. The primary function of the shock absorber is to damp the spring oscillation. In the case of some cars, it is asked to do a bit more. On the TR6, it also serves to restrain the rear suspension. On an MGB, the front shocks provide the upper A-arm in addition to the damping function. To be honest, they really should not be called shock absorbers, they would more appropriately be known as spring dampers. Damping can simply be defined as the steady diminishing of amplitude in a vibration. In our case, the vibration is the compression and return of the suspension springs. While any spring system will eventually damp itself out from a single event, the shock absorber provides a viscous means of diminishing the amplitude by applying a resistive force. The result is that the number of cycles before the amplitude is dimished to zero is greatly reduced. This is at the root of the old "push down on a corner and see how many bounces before it stops" shock test.

The typical "stock" shock is biased more heavily toward rebound damping than bump damping. This means that the spring travel when you hit a bump will be faster than on the return travel since the damping is biased more on the rebound travel. When the damping rate is increased in bounce, the velocity of the spring is reduced in compression and spring travel is somewhat more limited. This is typically what a "performance" shock does. In the event that a gas shock, such as most KYBs or Bilsteins, is used there is also what amounts to a slight increase in spring rate. I have often joked that going stiff on the springs is the handling equivalent of chocolate sauce, you can hide a lot of sins and vices with chocolate. You can stiffen up a suspension and hide handling sins in the same manner. The higher rate springs and the gas shocks in the conversion should make for better handling on a TR6 in theory since the rear suspension goes through some odd geometry changes through the travel.
SteveP

Steve, I think I begin to get the picture. If performance shocks stiffen the spring action(?) does this necessarily mean a less comfortable ride through uneven road surfaces? And is that the necessry trade off? (Maybe I still don't get it).
J.T. Cruz

John Horton made mine. Costs about 110-120 dollars, comes with kyb shocks. Good quality, and only cost 1/2 of vitoria british.

johnehorton@yahoo.com
Adam Wilhite

J. T., there are a couple of things going on. First, the gas pressurized shocks such as the Bilstiens or most KYBs. Because of the gas pressure, they effectively raise the spring rate somewhat. Depending on the car, they can even impact ride height. Then you have the fact that the typical perfromance shock will inhibit the springs ability to accelerate from rest to a maximum velocity through a resistive force. Either can force a ride that is somewhat less confortable. The degree of decreased comfort is a function of how much resistance/increase in spring rate and your subjective feel. What is unacceptable to one person can be too soft for another (guess it depends on just how much of a hard ass you happen to be). The situation for improved handling would be similar. One person's greatly increased perfromance may draw a yawn form someone else.

The key is setting the car up for the way that you intend to use it. The higher rate springs at normal ride height along with a "normal" perfromance shock would still be streetable at the expense of some ride comfort. If you were to go to a higher rate and lowered spring along with a very heavily valved shock, then it would probably not be something that you would like to drive on the street.
SteveP

Steve et al, think I've got it. Having reviewed previous threads, seems there are three ways to achieve improvement in cornering; different shocks, replace springs or add sway (anti-sway?) bar or various combinations thereof. What effect does the addition of a sway bar have? How does it enhance cornering ability? And what effect does it have on ride comfort? I really hope this will be the last question I'll have on this topic.
J.T. Cruz

This thread was discussed between 28/06/2002 and 03/07/2002

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