For the TR4 - there's a few vendors with alloy flywheels and a shop that lightens the cast iron piece. The end results are about the same price point, within a couple of oz of the same weight - going from around 32lbs to about 12lbs. Lightening the original takes some pretty aggressive machining. Any thoughts from the hive on a preference? Vintage race car - will be peaking around 6500rpm.
Does the alloy one have a replaceable friction surface? I'm guessing the stock one doesn't. How much are they charging you to lighten it? Because that's a lot of money for a bit of machining, seeing as alloy flywheels are usually around $500
I ran an aluminium flywheel on my racing Spitfire in the 70's and it was lighter than my machined one. It was regarded as the way to go even back then. Currently building up a TR8 for vintage racing and have an aluminium one.
Be careful if you machine a flywheel. I saw guys in my Spitfire days take too much metal off them and then they disintigrated.
I originally had my stock flywheel lightened then later replaced it with alloy (MG Midget vintage racecar). The alloy cost around $400 and the flywheel cost less than $100 to lighten. $75, IIRC. I think I would have been fine with the lightened flywheel, but all my buddies were using alloy so I had to get one, too.
I took a pair of OE cast iron flywheels (sc300/supra parts) to a shop here in Atlanta last week to have them resurfaced and asked about lightening them. This shop deals pretty much just in performance clutch assemblies. They said that they could only take off a few ounces safely and anything more would risk them coming apart. I was surprised because they looked like they could be trimmed down a little, but I trust their judgement. Here's what they look like:
If you don't have a good shop to take your flywheel to - someplace that will give you an honest opinion on whether it's safe, then I'd just go with a good aftermarket alloy setup. If both sound safe, then I would go with whichever will be easier/cheaper to resurface.
The other thing to consider is even if both weigh the same amount, the location of the weight is crucial to the rotational inertia. If, for example, one has a lot more material near the center and less around the outer diameter, then that setup will rev more freely and give better performance.
What's the name of the place you took it to? I'd be interested to have them look at mine as well.
In reply to sobe_death:
Not sure if you mean me or the OP. The place I go to is Clutch Specialty.
http://www.clutchspecialty.com/
How much do you like your feet? Seriously, I would be very concerned with removing that much metal from an OEM iron flywheel. Even at 6500 a failed flywheel is the automotive equivalent of a Claymore.
I looked into this when I had a 2002. First I whittled a bunch of material off the stock fly wheel and thought I was really taking the weight off. Nope, maybe 1/2 lb.
If the money is negligible, go with the aluminum aftermarket with replaceable steel surfaces and ring gear.
Dan
fastoldfart wrote: How much do you like your feet? Seriously, I would be very concerned with removing that much metal from an OEM iron flywheel. Even at 6500 a failed flywheel is the automotive equivalent of a Claymore.
This, this, this, this, and this.
I have never heard of THAT much metal being removed from a flywheel. Maybe if the Triumph used a 7" clutch disk and it had a 3" thick ring of useless metal on the outside, but otherwise HELL NO.
That said, I am very pleased with the 9lb flywheel on the RX-7. Nothing but good things to say about it, drivability on the street hasn't changed either.
Go for the aftermarket alloy flywheel, lightening stock flywheels always seemed sketchy as hell to me.
There are some cast iron flywheels that I would be comfortable in lightening, Mk 1 VW's for example. Most of the weight of the flywheel is non-structural and easily removed without compromising the overall strength. On a more conventional flywheel taking more then a pound or two will as someone posted turn it into a claymore mine.
Go alloy!
The TR4 has a 34lb OEM flywheel? Is it a tractor engine? I thought that 21 lb flywheel on my SAAB c900 was heavy!
I had my SAABs flywheel lightened down to 15 lbs. Both the machine shop that did the lightening and the shop that balanced it though that it looked safe.
If you buy an aftermarket flywheel, you still have the original as a backup.
HappyAndy wrote: The TR4 has a 34lb OEM flywheel? Is it a tractor engine?
Sort of - the TR3/4 engines were based on a design for ferguson tractors. Sounds like alloy is the way to go. I've seen a few going for around $350
Knurled wrote:fastoldfart wrote: How much do you like your feet? Seriously, I would be very concerned with removing that much metal from an OEM iron flywheel. Even at 6500 a failed flywheel is the automotive equivalent of a Claymore.This, this, this, this, and this. I have never heard of THAT much metal being removed from a flywheel. Maybe if the Triumph used a 7" clutch disk and it had a 3" thick ring of useless metal on the outside, but otherwise HELL NO. That said, I am very pleased with the 9lb flywheel on the RX-7. Nothing but good things to say about it, drivability on the street hasn't changed either.
It very much depends on how the metal was taken off.
My friend has come up with a way to lighten an Alfa flywheel, and what it does is take a big ring of iron out of it. The way he does it does not alter the safety of the flyweel.
Older mods took chunks of the ring out- that was very dangerous.
But his method is technically safer by the way it's removed.
Do you feel lucky? This is your legs we're talking about.
Kenny_McCormic wrote: Do you feel lucky? This is your legs we're talking about.
Hey, they make hand controls.
http://www.youtube.com/watch?v=rgJPpBvXSds
http://www.youtube.com/watch?v=NKwJcKvtw6Y
Get the one with the SFI rating. Steel vs aluminum is not a big deal.
In reply to Knurled:
Certainly not a pleasant transition though.
Consider that SFI flywheel specifications specifically prohibit the use of typical (gray) cast iron. There is a reason for that.
People frequently assume it's safe to take off the 'non-structural' areas from a flywheel, but I wonder how many of these have done any analysis or testing on the harmonics of the flywheel after removing any significant amount of mass from such an area? The more metal removed, the bigger the question mark. It's probably fine most of the time, on most flywheels, under most operating conditions. But the more metal removed, the more questionable it becomes. Think about what happens to a flywheel that happens to hit its harmonic resonance right around the peak horsepower rpm. Hint: It's not good.
https://www.youtube.com/watch?v=w-2KiubBNMQ
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