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Rubber quality

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I

ichthos

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Hello,
I have seen numerous posts on rubber quality. Is there any way to tell if it is a good rubber quality or not? Most of the rubber in my car is starting to rot from age. In some places the rubber quality would not matter much, for example with a floor plug. In other areas it would make a big impact, like with steering and suspension bushings. I would rather pay the extra money to get good rubber for bushings, but I have not found that spending more money has made a big difference at this point. Any suggestions?
Thanks, Kevin
 
The problem is that the majority of rubber products are made overseas and lack in quality. The floor plug, unless damaged beyond use, I would keep regardless because you will never pull it unless you forget to put the top up in a monsoon. Front end bushings, The dust seals will be gone within months, if not before you finish rebuilding the front end. The bushings will last 10-20,000 miles, if that. Your tie rod/steering rack boots will last 2-3 years. Ball joint boots 1-2 years.
One of the problems is there weren't enough of these cars built for decent production runs of parts. Another problem is that the suppliers are trying to keep the price down. And of course we complain when we have to pay the high price, encouraging them to keep the price down.
I am not aware of any distributor who sells higher quality rubber products. We have to put up with the current supplies or choose alternative parts when available. If you are able to find NOS parts, you will have to pay the price, but in a lot of cases, it's worth it.
 
Doug:
I don't understand why the actual material for bushings or boots would be sub par even in a short run of production. The material should be the same (composition wise) for what ever is produced (for Ford, Chevy, Toyota, etc) unless the specifications require a change in the composition of the material. I would understand that the injection molds might be "sub par" because of the cost vs. short run of parts resulting in more of a fit problem rather than a decomposition problem. I just don't understand why the short run would wind up with a decomposition problem. I am thinking my 37 year old bushings and boots may be better than new ones!
 
My thoughts are that because of the short runs and desires to keep the prices down, our suppliers are having to go to overseas manufacturers using inferior materials.
The worlds' automakers are keeping the big run manufacturers busy and are much more demanding on quality.
 
I think that one of theings that we are seeing is the reult of a change in the materials used.
(The following is my opinion and isn't based on any factual information that I have).
When our cars were new, I think that most of the elastomeric parts in them were made from a vulcanized rubber (either natural or synthetic). My guess, based on manufacturing economies is that most of the repro parts are now made from thermoplastic elastomers. The difference is that the thermoplastic compounds can be made in an injection molding machine by just about any plastic molding house (much more available than vulcanizing). That would apply to non-loadbearing parts (plugs, boots, gaiters, etc). The TPE materials are good materials but they won't hold up like a true thermoset rubber will.
For structural parts like bushings and engine mounts (which are still vulcanized rubber) I don't know what the reason is for the difference, but it could boil down to the amount of time that they hold the parts at temp and the rsulting level of vulcanization.
In the end it boils down to good economics; how much is a parts vendor willing to pay to his supplier for these parts? What makes it tougher is that I would guess that for a lot of our parts there is only one source, who then sells to all of the jobbers (VB, TRF, MM). The reason for that is that it is very difficult to recoup the cost of the mold tooling for these parts when the volumes are as low as what we use. It is not a big deal at all for a mold tool for low volume production to run over $30,000 and we have ones for production volumes that are over $500,000. These are not big or complicated tools either. So the end result is that in order to pay for the mold tool the molder needs to sell his parts to everyone he can and no single jobber can afford to have many parts made up just for him.

IMHO this is going to be a problem that we are going to have to continue to live with. One thing that may help some is that the newer thermoplastic rubbers are a lot better performing than the materials that were available even five years ago. So if our suppliers change to those rubbers we may see better life from our parts.

Dick
 
To replace the rotted rubber dust cover rings for the front bushes, I use black tie-wraps that are 1/4" wide. I wrap it around without any dis-assembly and clip off the excess. I make sure the area to be clipped off is out of sight.

I'm planning to replace all the rubbers on the front end and would like to know if the newer synthetic greases like Amsoil Red will allow the rubber to last longer. Any comments ?

https://www.britishcarforum.com/ubbthreads/photopost/showphoto.php/photo/1919/ppuser/4127
 
When I sell synthetic greases, I tell the customer that they will last longer if they are delayed in their lubrication intervals, but do not alter the interval periods.
What you will notice is that you will use less grease per interval. The synthetics have a higher melting point and stay in better. Most will be better against water. I use a synthetic on my TR3 water pump and have had great success with it.
I use a Bentonite based grease on everything else. A good grease on the market to try is The Lucas red grease. It is a high tack grease that should stay in where you need it.
Any time you change greases, you should get the old out. We have always been instructed not to mix especially synthetic with other types.
 
Oops. I got off on a tangent and didn't answer your question. Knowing that some rubbers react adversely to silicone brake fluid, while others do not, I would have to guess that it would depend on the rubber and the lubricant.
If it did, I don't believe that it would alter the rubber that much since the rubber is of poor quality.
 
Thinking like a chemist - which I am NOT:

Why does the rubber decompose? Is it just time? Exposure to air? Exposure to sunlight? Exposure to grease (i.e. the brake fluid mentioned above)? ...?

Step two is how to eliminate the offending element. Should we paint the rubber (hiding it from sun and air)? Should we use rubber cleaners and dressing like sold by Griot's? ( Link - no affiliation or endorsement) Armor All?

Thoughts? Any real chemists out here? (I'm just a mechanical guy who knows that chemistry does cool things)
 
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