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An MX5 related query


jon.l
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Hi folks,

 

Just wondering if someone could explain to me the negatives and positives of fitting polyurethane suspension bushes, from a professional point of view?

 

I understand that stiffer bushes can provide more compliance and less unwanted suspension movement, at the cost of transferring more of the 'road' through the chassis of the car. I also learned recently that stock bushes are designed with some compliance in them to allow for a little bit of movement (to compliment a 'total' setup inc shocks/springs/tyres/ARB's if you will) as part of the complete package. Now obviously my car is stock and I intend to change the bushes at some point as it is nearing 130k miles, I also have the intention of renewing the suspension and tyres.

 

Now if I carry out these changes I would be interested to know what I can expect in terms of ride quality and general driving feel. In terms of communication I am more than happy with the feedback provided by the car at the moment, albeit a little hard as it has the Bilstein suspension. I would rather not compromise too much with ride quality but ould certanily be interested to know how the Gaz setup compares.

 

The other reason I am considering using poly bushes (as others do) is also cost. OE items generally aren't cheap, but then again I'd rather not save myself £100+ to find the ride is unbeareable.

 

Cheers :rolleyes:

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If you stiffen all the anchor points that articulate the chassis positions stay matter of fact meaning the general ride of the car is more precise. This makes calibrating the chassis easier since angles like toe are no longer absorbed into the bushing.

 

The ride is definitely harsher and the polly's can be high maintenance with squeaking and alike, it's for this reason i would only recommend polly's for the serious track day star.

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I seem to remember someone saying, can't remember who, that as the old bushing get older they stiffen up.

I agree with Tony, I would only polybush for serious track use. You're probably looking at £800 for a garage to do the work from what I've read.

Lexie has 170k km on the clock on the original bushes. GAZ shocks and WIM fast road alignment. I cannot feel any wear from the buses or have any indication that something is untoward.

If you do go the polybush, be aware that one of the bushes is softer that the rest, I think it's the one on the front of the lower rear wishbone. Can't think why, but there is a reason Anti-squat?

h

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Thanks for the info guys, pretty much confirmed what I was thinking :)

 

If I did rebush the car I'd probably do it myself anyways, but I think I'll leave it for now.

 

One other thing, have either of you driven with or been in an MX5 with the Bilstein setup? How does it compare to the Gaz setup for ride quality? I know the Bilsteins are reknowned for their stiffness on the bumpier roads (which Sussex is pretty much made up from :) )

 

Jon

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Lexie, as an S Special had billies on. Hard as hell.

Now with GAZ Gold, I have a nice comfortable set up for daily driving and some spirited driving, and can turn the shocks up for track when required. (although don't normally bother as she seems to cope well on track with the road settings I use.)

We have the Hornet on GAZ Gold Pro on full track and WIM track alignment. She's sublime on track, but on road too hard to be a daily driver. (Again on this we tend to leave the settings as they are and not change them for road/track.

GAZ adjustable for shock/rebound, Billies not.

GAZ adjustable for height, Billies not.

GAZ selectable spring rates, Billies, sort of.

AFAIC, there is no competition, GAZ Gold every time.

h

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Where do I sign then? :D

 

I think a PM to Tony is in order.

 

Thanks all

 

Jon

 

Fact is i don't associate to any old crap... Some years back GAZ asked to associate to us in regard to our nationally excepted wim fast road setup for the 5. In order for this to work i wanted certain changes to their current product, these changes where demanding and costly for GAZ to evolve but they did. There has been some problems along the way and i must say GAZ have been exemplary in resolving them... My attitude is if there's a problem hold your hand up and put it right.

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Just to complete the thread, about one bush being softer than the others.

 

(Found on the Nutz forum)

 

Main problem with the autolink bushes (and deflex etc) is that they simply ain't as good as the OEM affairs. Yes, they're p**s cheap. Yes, they're easy to fit. But you've got stiction (static friction), I very much doubt they'll survive 10 yrs/100k miles, and on top of that you just destroyed the passive rear wheel steering on the MX5. (The outer front bush on the lower rear wishbones is softer than the others, so the harder the rear is asked to corner the more the outside rear wheel toes in and the more grip it generates - make 'em both the same stiffness, or solid, and you've just undone the anti ditchfinding engineering)

 

h

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