»Hardrace Hinterachsgummis RTA

Thought it would be interesting to compare the stiffness of a few RTA bushes, so here goes...

I've just removed the RTA bushes from my car - original bushes AFAIK they have not been changed before. The car is ten years old and done about 80k miles.

Also to hand were a new Mugen bush and a new Hardrace bush.

Subjectively the OEM one feels very soft, it's really easy to deflect it with hand pressure. The Mugen one is much stiffer but can still be deflected reasonably easily. The Hardrace one just feels solid, very hard to deflect it at all by hand.

Here's a pic of the three lined up, left to right we have the old OEM, Mugen, Hardrace. The Mugen has similar construction to OEM, Hardrace has much more material and a harder plasticky quality to the rubber.



Here's my ghetto test rig: Trusty old Workmate, 6 pint milk carton full of water, cable tie, hook, spirit level and ruler



My plan was to hang the weight off the end of the bush and just measure the deflection - seeemples

This sort of replicates the load the bush will be under in practice, probably not that scientific but this isn't Honda/Mugen R&D exactly

First up, the tired OEM bush. Just for reference, with no load on it the distance from the spirit level to the corner of the tab was about 25mm in all cases. Hang the weight on it and we see about 45mm ie 20mm of deflection:


Mugen bush: 35-36mm distance or about 10mm of deflection, ie about half as much as the old OEM one:


Hardrace bush: no measurable deflection at all, it literally didn't move when I attached the weight


Shame I didn't have a new OEM one although the test is repeatable if I do ever get one.