I was prepared to sell my Fiesta ST, it wasn't exciting me anymore and I had THOUGHT I was ready for a new experience. I had been compensating for symptoms of a failing rmm for close to a year at this point (without completely realizing that I was, in fact, compensating), clutch take-up was vague and it was hard to drive smoothly without really riding the clutch. Part of me just thought that since the car is coming up on 80k and I taught myself to drive stick on it that maybe it was time for a clutch so I was sort of planning on dumping the car before that bill came due.
On a whim, I decided to replaced the rmm. Part of me suspected something was going on with this due to all of the symptoms I'd learned to alter my driving habits to accomodate. I just sort of noticed one day that everything about how I was driving the car was different than it used to be, and it felt a lot less engaging. To be fair to me, this would be the third time since I've owned the car that I'd replace the rmm, so I wasn't entirely convinced this was the issue especially since I couldn't really rock the motor by hand. I bought the car with around 43k miles on the odometer, and she's currently sitting at around 76k miles so for anyone counting I've done a rmm once every 10k miles give or take a few thousand.
In that time span, I've eaten through rmms from both mountune and whoosh. When the mountune went, I'd assumed that I just had a bad batch of bushings but now that I've also destroyed a mountune in roughly the same mileage span I'm starting to believe that poly bushings just aren't a good material for the Fiesta given that the rmm is connectted to the trans and downpipe/catalytic convereter it just means theres a significant amount of heat soak back there. Reading through cPe's rmm descriptor, they suggest that polyurethane is specifically a bad material for the FiST for the aforementioned reasons, so I wanted to grab a rmm that used any material besides polyurethane. I'd initially elected to replaced the whoosh rmm (the most recent failure) with a cPe, which advertised as using EPDM rubber, but as luck would have it Ron had just sold the last one as I had placed the order.
Rather than wait, I went with a Vibra-Techincs unit that used rubber in the bushing material, and at Ron's recommendation I elected for the competition (not the fast road) bushing variant as he told me that would offer the most similar characteristics to the cPe unit. Install was NOT 100% straightforward. The only annoying bit was when I ended up having to drill out the factory mounting plate to get the dowel on the Vibra-Technics unit to fit (I went full caveman on this and sideloaded a 1/2 drill bit to ream the hole, in retrospect a cheap metal file would've probably been a better option).
Initial impressions: Vibrations are definitely noticeable, particularly below 2k rpm, but I'm digging it for now. I will update after I spend a few weeks doing my 90 mile round trip commute on whether or not I regret the... added sensory input. It seems livable right now. Clutch takeup is buttery smooth and I've already found 2 seperate occasions to take the car out even though I don't really have time for any joy rides right now and, most importantly, its gotten me excited about driving my FiST again!
So, a word of warning to new owners and other beings from the future: If you have a RMM with polyurethane bushings, you're gonna want to change that out.
On a whim, I decided to replaced the rmm. Part of me suspected something was going on with this due to all of the symptoms I'd learned to alter my driving habits to accomodate. I just sort of noticed one day that everything about how I was driving the car was different than it used to be, and it felt a lot less engaging. To be fair to me, this would be the third time since I've owned the car that I'd replace the rmm, so I wasn't entirely convinced this was the issue especially since I couldn't really rock the motor by hand. I bought the car with around 43k miles on the odometer, and she's currently sitting at around 76k miles so for anyone counting I've done a rmm once every 10k miles give or take a few thousand.
In that time span, I've eaten through rmms from both mountune and whoosh. When the mountune went, I'd assumed that I just had a bad batch of bushings but now that I've also destroyed a mountune in roughly the same mileage span I'm starting to believe that poly bushings just aren't a good material for the Fiesta given that the rmm is connectted to the trans and downpipe/catalytic convereter it just means theres a significant amount of heat soak back there. Reading through cPe's rmm descriptor, they suggest that polyurethane is specifically a bad material for the FiST for the aforementioned reasons, so I wanted to grab a rmm that used any material besides polyurethane. I'd initially elected to replaced the whoosh rmm (the most recent failure) with a cPe, which advertised as using EPDM rubber, but as luck would have it Ron had just sold the last one as I had placed the order.
Rather than wait, I went with a Vibra-Techincs unit that used rubber in the bushing material, and at Ron's recommendation I elected for the competition (not the fast road) bushing variant as he told me that would offer the most similar characteristics to the cPe unit. Install was NOT 100% straightforward. The only annoying bit was when I ended up having to drill out the factory mounting plate to get the dowel on the Vibra-Technics unit to fit (I went full caveman on this and sideloaded a 1/2 drill bit to ream the hole, in retrospect a cheap metal file would've probably been a better option).
Initial impressions: Vibrations are definitely noticeable, particularly below 2k rpm, but I'm digging it for now. I will update after I spend a few weeks doing my 90 mile round trip commute on whether or not I regret the... added sensory input. It seems livable right now. Clutch takeup is buttery smooth and I've already found 2 seperate occasions to take the car out even though I don't really have time for any joy rides right now and, most importantly, its gotten me excited about driving my FiST again!
So, a word of warning to new owners and other beings from the future: If you have a RMM with polyurethane bushings, you're gonna want to change that out.
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![[wink]](/images/smilies/wink.gif "Wink [wink]")
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