Need advice on suspension rebuild

[Flummoxed]

Guys-
I need some opinions on using rubber or polyurethane bushings on a susp. rebuild. Also, what's your opinion on the differential mounts (rubber or poly.). How did you guys decide? Is the longer lasting polyurethane worth it? Was installing the polyurethane much more difficult than the stock rubber? Thanks.

 

[bunzil]

There's a lot of discussion on this. Poly lasts longer, but costs more, and is more difficult to install since it's less pliable. I wrestled with this for a long time and decided to use rubber on the suspension and poly on the differential. Why? Because folks here said poly was prone to squeaking and would produce a harsher ride. I had driven on rubber for years and was completely satisfied. If it works, why change it I thought. Plus I was fearful I might not like the squeaks and ride change and then have to rip it all out again. Poly naturally is good for that extra degree of performance, but I gave up thrashing my TR years ago. I choose poly for the diff for it's extra durability and lifespan. But again, folks here argued that the less compliant poly would absorb less energy and pass same along to the already fragile mounts - especially the front right. But since I don't trash my 6 so I went with reliability. In my opinion therefore, I'd say it's a matter of driving tastes. I've been pleased having the rubber up front - it made a big difference getting it all secured properly again and I noticed a big improvement. I hope this helps, just the thoughts of one guy. Find a good alignment guy for the front and back once you are done.

 

[LastDeadLast]

Flummoxed,

Have you considered Nylatron? They're self lubricating, so you don't have to worry about squeaking. Personally, I haven't noticed a big difference in road harshness after their installation. I did, however notice a big difference with poly diff mounts.. they transmit a lot of vibration to the chassis...

Here's a nice writeup by Richard Good about his Nylatron bushings:

https://www.goodparts.com/tech_docs/Suspension_Bushings.html

I've also heard that the rubber that all the aftermarket houses use nowadays is a lot less durable than the OEM stuff.

Also, give a high amount of consideration to Richard Good's adjustable trailing arm brackets. Several members on this board have them and I've never heard any negative comments about them... my alignment guy loved them and turned a rear alignment that can last hours into minutes. Here's a link:

https://www.goodparts.com/shop/index.php?categoryID=13

 

[Brosky]

My original TR6 bushings lasted 54,000 miles and 34 years. And probably could have gone a lot mire, but I'm in the process of a complete restore, so they were next on the list.

My car rides and handles beautifully with the new stock bushings. Now, I don't rally or race it, but how many owners really do? I've driven in TR6's with the new poly bushings and I personally do not like the harsh ride.

JMHO and nothing else but that.

 

[Guest]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]my alignment guy loved them[/QUOTE]

so did mine when he was under there on Friday. He told me he was dreading the job until he got under there and saw them...

 

[KVH]

I agree you will hear differing opinions. And I've not tried prothane or nylatron.

But I would advise against rubber. I thought I'd be a purist and use rubber when I totally rebuilt my TR4A front suspension a few years back.

The upper bushings twisted and cracked in just 9 months.

I reinstalled polyurethane bushings and they have really been fine. I do wonder if they cause more wear on the fulcrum pins but I suppose no big deal.

 

[TexasKnucklehead]

I have urathane in the front and back, as well as the adjustable trailing brackets. The alignment guy broke one of the adjustment bolts trying to align it. You must follow the directions. With the old rubber bushes, the car was barely driveable -wondering all over the road at 65mph. Now it's straight and handles great. No squeaks. Replacing all those parts is something I wanted to do only once.

Jer

 

[Flummoxed]

I appreciate the great advice. I think with my novice mechanical ability (I am getting help from a more experienced mechanic)and the fact that I baby the car when I drive it, I will prob. go w/rubber. But, the fact that poly. would prob. never mean another susp. rebuild is very appealing. I'm going to pray I get lucky and these new rubber bushings "never" deteriorate like the stock ones in there now.

 

[Brosky]

A lot has to do with lubrication and how you put it together. I used Mobil Synthetic (red in color) chassis grease when I did mine. It "supposedly" is great for rubber parts and the trunnions, per several local guys who swear by it, rather than at it.

You'll see the can in some of the pictures below.

https://www.74tr6.com/framepartassembly.htm

 

[Opa]

Here's my set up, rear I used oem rubber in trailing arms with Richard Good brackets,tube shock conversion,uprated stock height springs and poly diff mounts.

I went with oem rubber mounts as the rubber is solid mounted and the flexing is done within the rubber sleeve.Poly bushes either move on the bolt or within the aluminum swing arm as I don't think poly flexes like rubber.

If you go to a tube shock conversion, check suspension travel with spring removed and make sure shock does not become your suspension stop.The frame is not designed to be a suspension stop as originaly the shock arm had a bump stop as well as the inner fender, which bottomed at the same time.I had to modify the bump stop on trailing arm as well as the inner fender stop so that the suspension bottemed before the shock did.

Front end I used poly through out, uprated, stock height springs and new shocks.

 

[DougF]

My thoughts are that bushings are for pivot points, not to absorb shock from the road. Let the springs and shocks take care of that.
I first tried rubber and had to replace after a couple years. Next came urethane. No problems with sqeeks and I felt the car handled better. When I restored the car, I installed Richard Good's nylatron bushings. I feel more through the steering wheel, but really like the upgrade.
If you use a lubricant with urethane or rubber, I would use a dry lube such as a moly. It won't attract the dirt and cause possible premature wear.
I just installed urethane bushings on a club member's car yesterday. They went on very easily. The car wasn't test driven due to a snow storm the previous night and the subsequent salt.

 

[Opa]

I see a little clarification is in order...yes the bushes are pivot points,but the OEM bushes pivot on the rubber between the small tube the bolt goes thru and the aluminum swing arm.The small tube is molded to the rubber and the outer is pressed into the swing arm.Hence the instructions in the manuals to not tighten thru bolts until car is lowered and loaded with 300 lbs on the seats to give a close to driving condition.
This is done so tube will centre itself to normal driving conditions, and give approx same amount of twist to the bushing without damage. If cross bolt is tightened with swing arm hanging down and tightened,the tube molded into the rubber will tear loose and damage the bushing.
Same principle applies to the front suspension.A arms are tightened after car is put on the floor and weighted, same damage will result to bushes causing premature failure.Some after market materials used may be somewhat inferior as well not helping the situation any.
I don't believe poly has this twist capabilty of rubber, which means it is moving on either the bolt or in the eye of the swing arm or A arm.Hence the squeaking. Just my opinion.....

I also put in Richard Goods solid steering rack mounts,but all said and done the biggest improvement imo and my particular TR, was the rear upgrade, tube shocks,springs,bushings and brackets.

 

[swift6]

Polys and Nylatrons should also use the metal sleeves. Though they are not 'bonded' like the rubber ones. When you tighten the brackets, they should still tighten up against the metal sleeve first and not the bushing material. Poly/nylatron are usually easier to install as they are usually two piece and do not require any special tools or techniques to install. There are some one piece poly/nylatron bushings out there and they can be a real bugger to install.

IMHO, THE most important place for a better bushing than stock rubber is in the trailing arm bushes. The rubber bushes there allow the trailing arms to track at different angles in corners which increases a rear steer affect and not in a good way. That's what makes the rear of a TR4A-IRS thru TR6 'twitchy' in long corners at high speeds. Poly or nylatron here will greatly improve the smoothness of the rear following the front in an appropriate manner.

If you really wanted a massive improvement then a solid roller bearing assembly can be fitted in place of the bushings. The use of the bearing assembly can increase ride harshness and is generally recommended for race use only but has been successfully used on fast road cars.

The use of nylatron or poly should have no effect on ride quality when used in the trailing arms. The greatest change in feel comes from using poly/nylatron in the front suspension. Even then, its mostly through the steering. Shock and spring choice have a far greater effect on ride quality than upgrading the bushings.

Of course, if you don't drive through corners quickly enough to feel the 'twitch', then there is also no reason to upgrade from the rubber. And NO, that's not an attack on anybody's testosterone levels.

 

[Opa]

for the most part,where does the pivot action take place in your opinion?The eye of the swimg arm or on the tube between the brackets?

 

[RobT]

Well my 2c -

I used a combination of poly and rubber. On the suspension, all poly except the lower front wishbones - so as to avoid some of the harshness/road noise at the front. The front uppers need poly IMO since as others have suggester, the rubber just does not last. (I forget what I did on the rack, but I think rubber also for the same reasons). And on the rear, the poly bushes stop the rear wheels "steering". I used rubber for the diff mounts since the diff supports can be a weak point, and it seems to me potentially increasing the shock & vibration at these points by uising stiffer mounts may not be such a great idea. Anyway this mix works for me, but every one is different, and its actually nice to be able to mix the materials used to suit your preferences.

Rob.

 

[swift6]

for the most part,where does the pivot action take place in your opinion?The eye of the swimg arm or on the tube between the brackets?

The metal sleeve is there to keep the bushing from being crushed but is also the pivot point. The rubber bushings twist, as do the poly/nylatron items, to allow the movement of the suspension arm, around that crush sleeve. The rubber bushings actually restrict movement more than the poly/nylatron as the rubber is bonded to the metal sleeve. The bushings job, however, is not to restrict movement but to facilitate it. Poly /nylatron bushings do not increase the stiffness of the suspension moving in the arc that they are supposed to move in. It makes it harder for those suspension pieces to move outside of the arcs they were designed to move in.

The rubber absorbs noise, vibration and harshness (NVH) better but stinks for handling. The rubber bushes also allow more deflection than the poly/nylatron which is what leads to the semi-trailing arms wandering around in different directions. When the bushings are getting weak, they not only track differently on long curves but will also flex enough to change the toe settings while under heavy acceleration in a strait line. When its really bad you might even have to counter steer to stay straight under initial heavy acceleration.

 

[foxtrapper]

There's plenty of junk polyurethane on the market. Just as there's plenty of junk rubber. Don't go thinking that poly means never repair/replace/maintain again.

Quite the opposite in fact, you need to regularly lubricate poly bushings. Otherwise they squeak and bind. So either fabricate a grease fitting at each location, or resign yourself to taking the suspension off and apart to lubricate it. Some lubes last longer than others, but they all need replenishment.

There is a matter of ride harshness. While polyurethane and rubber can be had in any type of hardness, it is typical in the US to find polyurethane bushings to be appreciably harder than rubber bushings. This makes the ride harsher. Not bone jarringly harsh or such, just harsher and not as syrupy soft as possible.

 

[swift6]

There's plenty of junk polyurethane on the market. Just as there's plenty of junk rubber. Don't go thinking that poly means never repair/replace/maintain again.