Time to tackle the saggy rear suspension of my 1969 GT!!!

I got a bit more done today.

What's everyone's opinions on polyurethane suspension bushes???

I refreshed my rear bushings with poly a few years ago. I really like how the rear feels now. It is very tight. My preferences run toward a tight, responsive driving feel and I do some autocrossing. Most of what people might feel as “harsh ride” in my car would be due to the front stiff springs...not the rear.

Anyway, for me I would not go back to rubber. I’m happy.
Brad

I have just completed a rebuild of front and rear suspension and have used poly bushes and pads throughout. I was mainly interested in their apparent longevity when compared to new rubber. Like Brad I have noticed that the car feels taught and well planted. I have parabolics at the rear and custom coil springs at the front which together with a three quarter inch front ARB has given me both the quality of ride and handling that I wanted. I do not compete in the car. Maybe I was lucky but the work was very straightforward, everything came undone and went back together just as Haynes says it should.

What I see with the poly bushings in the front & back of the rear leaf spring, the poly bushings are egg shaping, not staying round. I have seen this in 5-6 Bs that I have parted out & with as little as 30,000 miles on the bushings. I run the factory V8 bushings in the ft. A arms & I have/need to change them around every 125, 135,000 miles, on my V8 & I have a small oil leak out the ft. seal & I get oil on the rubber bushings & this dose not help the bushings out. The stock rubber bushing @ the ft. of the rear leaf spring, I have never wore one out & the back ones I save to use when I replace the poly egg shaped ones. I have 3 GT with a stock 1.8 engine with over 300,000 miles on each, another GT V8 with 250,000 miles on it & my first V8 that I built 36 years ago that has 710,000 miles on her this week & I am after the life expectancy of the part & the RIDE!!!, I hate working on my MGs when I could be DRIVING!!!

Poly is not poly is not poly. Like any material, it is up to the designer to select it's parameters. Many brands, many properties.

Poly does not twist internally with the suspension movement, so it becomes a friction bearing. If it is not disassembled and greased often, it becomes a sloppy worn out mess. A few can be modified to fit Zerks. ( path through, groove to distribute etc. ) It would be hard on the rear springs without risking a weak point.

Rubber is an amazing material. All new cars come with rubber. You might gather, I am staying with rubber.

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Cogito ergo sum periculoso

"Poly is not poly is not poly. Like any material, it is up to the designer to select it's parameters. Many brands, many properties."

I'm pretty sure the same can be said for modern rubber "blends". They are NOT all created equal...

Even so, I haven't heard many complaints about poly bushings. Except that the ride is firmer; and guess what? It's a sports car, not a Cadillac!

I had NylaTron bushings in the front suspension of my GT for many years. Hard? Yes. Squeak? Yes, unless you squirted them with WD-40 once a week. But the front end was tight as a goose and I loved it!!

I have offered & let a LOT of people drive my GT V8 & NOT A ONE can believe it is a stock MGB ft. end! Over 600,000 miles on the king pin job I did on her before I put the V8 in her. I have had a few complaints about the free slop, in the steering wheel (U joint is sloppy & needs changed & I will do it next time the V8 comes out). I have soft springs, were the wheel goes up & down BUT I have a 1" sway bar to stop the body roll. In the rear I have composite/fiberglass springs, the rear has a stiff ride that I asked for because when I put 200 lbs in the rear hatch it rides good. I have a 3/4" sway bar in the rear. So I have a real good ride, just going down the road & when I hit the turns it GOES around the turn, real good & fast! All I do with this ft. end on my GT is EVERY 2,000 miles, I grease the 6 zerk grease fittings. I have greased the ft. wheel bearings every 75,000 miles & I STILL have the original wheel bearings on a car that now has 710,688 miles on her & I have a good ride, tight ft. end with no squeaks or WD 40 every week & tight as a goose but a sloppy U joint & a great ride!!!

Glen,
Sounds like you’re following a Colin Chapman philosophy - soft springs with good sized sway bars.

What spring rate are you running on the front springs?

(Emphasis added - Ed.)

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I am running a R/B GT that I built in 83, that is on the heavy side with a F/I & A/C, with a C/B cross member with wore out R/B B springs, that set the ft. end where a C/B car would set & I switched the left to right & right to left springs to try & balance the bachelor lean.

Glen,
Thanks.

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This subject certainly does seem to divide opinion!

Got the suspension finished tonight and just back from a drive, what a difference!!!

It's like a new car, very positive and ver comfortable

Well pleased!!!

Took the B on the 60 mile return trip to work today, it's like a magic carpet ride compared to the crashy old springs, so pleased!!!

If you had used a real lubricant, not a water displacer you could have gone a lot longer. That green waterproof grease might be a good choice. Some kits come with a silicone grease. Adding a zerk with through hole into a slot makes it work a lit better. Energy does this on some of theirs.

I ran Delrin on the rear outer bushings on my A-arms in my TVR as they put both ends in rubber. One end is enough. I did put in Zerks.

If you have not heard many complaints about poly, you have not been listening carefully. Agree, all rubber is not created equally, specifically the cheap replacements form China. The big difference is how they work. Rubber twists where poly is a bearing.

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Cogito ergo sum periculoso

Scott,

So where does one get good rubber bushing these days?

How would I know the difference between good and bad? Is there some sort of a test?

Thanks,

David

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74 Damask Red BGT
Davesmg@outlook.com