14 replies to this topic

[Tao]

HI GUYS,

being a buget racer I never replaced the suspension bushing on my spec Miata......mazda speed has been advertising a bushing set (all 30 pieces) for $500.......these are competition grade (40% stiffer than stock).....

 

question; is it worth the expense/hassle to change the bushings?    will I notice a big improvement in handling?

                are they legal in spec Miata?

 

currently I have no handling complaints but than again I have nothing to compare it to.....also the car is a California car so it hasn't endured extrame temp changes and visualy they look good--no cracks, wear or worn areas.

 

thanks and happy new year 

[FTodaro]

If your car is high mileage and feel slop in the steering and you want to be more competitive than you are it may be worth it but the job is a PITA.

 

also the bushings that are 40% more stiff than stock are not legal for SM you need to replace with the OEM bushing except for the front upper bushings with the offset bushing which was just approved.

 

As the saying goes, under our rules it is not legal unless the rules say its legal.

[Ron Alan]

Original control arms and bushings(20yrs old!) in the 2014 NASA Western Championship SM car!

[Steve Scheifler]

Something interesting...

 

[Ron Alan]

20 questions?

[Tom Sager]

Something interesting...

 

Mazda bushings supplied 20 years apart? 

[Bench Racer]

When using two bushings from the left side of picture the bushings because of shorter mid section will be easier to align concentric to each other.

[Jim Drago]

I think what Steve is implying is the newer bushing and smaller mid section is much more likely to flex than the older one. I happen to agree with him. 

[Johnny D]

I made these up for a friend to replace OEM bushings a while ago.

 

http://mazdaracers.c...ng-press-tools/

 

J~

[Jim Boemler]

Looks like a new and used bushing -- they may have looked identical before the one on the right spent 20 years in a control arm.

[Steve Scheifler]

These are for a lower rear control arm, outer-trailing bushing. As Tom thought, the one on the left is new from Mazda and on the right is an original from an early 1.6. I pushed out quite a few including from a 2002 and the originals all look the same.

Bench may be correct on the reason for the replacement part having a different shape, it could make installation simpler, but does it also make later misalignment more likely?

More importantly, how much deflection of the arm do they allow under load?

Basic squish tests (not installed) show that the new one compresses radially much more than the old, I suspect partly due to the shape as it can pucker out the sides. And if you think in terms of PSI, the load from the car is pressing on fewer square inches of rubber with the new one. However, whether from shrinkage/memory of the old part, or by design in the new one, the new bushing is about 1.5 mm larger diameter so it gets more pre-load when installed. If I build that pre-load difference into my tests then the force required to compress them gets closer, but the old one still wins.

Unfortunately my testing is far from conclusive because I'm over simplifying the conditions. I can't spend much more time on this at the moment but I may get back to it.

I've looked at several other bushings and the basic old/new design appears to be the same throughout. Looking at pictures of the "comp" set on the Mazda site it is clear that all are of the tapered design.

For what it's worth.

[FTodaro]

I pressed new bushings into my new build. I only messed up one bushing on alignment, once you get the hang of what it is your looking for. I just wonder with the difference from old to new, if we are gaining that much from replacing them. i have never been able to feel the difference.

 

they say that you should have all the same vintage bushings in your car, I have had to replace control arms at the track and as a result was mixing oem bushings with new replacements and could not detect any issue with that either.

[Tao]

thanks guys, great feedback.......I know that ron's car is a front runner (with the right driver in it)..if the old ones are good enough for him, they're good enought

for me...........

I think I will get those new off-set bushings for the uppers.....I assume they are made to gain a little more negative camber.....right?

[Steve Scheifler]

A lot more, but yes.

You should at least check your outer-upper-rear bushings (top of rear hub/upright). They are larger and tend to shrink, perhaps because they get hot from the rear brakes, and get loose enough to cause significant slop back there, which can be very bad.

[Glenn Davis]

Wasn't the front upper the only arm that came "loaded"?  So now I need to but a loaded arm and replace with the offsets?