Lighter wheels or coilovers for better body/wheel control and damping?

[Django91]

Hi guys,

Wondering if anyone would be able to comment on if lighter un-sprung mass(eg. wheels and tyres) would be a better means of improving wheel/body control than resorting to coil-overs, that may compromise ride quality/compliance?

If so how much mass would you want to lose to make a useful improvement? I believe the rx8 18'' wheels are around 10kg per corner, there are some after-market wheels in 18'' size at close to 8kg per corner, would these make a big difference.

Thanks and Regards.

[boosted]

I think 1kg of unsprung weight is worth 10kg on the car but i think a set off quality well set up coilovers would be my preference first over expensive lightweight wheels.

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[Django91]

I think 1kg of unsprung weight is worth 10kg on the car but i think a set off quality well set up coilovers would be my preference first over expensive lightweight wheels.

Sent from my SM-N950F using Tapatalk

Bola have a new flow forged range, which are about £700 quid/set in 18'' sizes I think, those are 8kg/corner. I don't know the quality/reputation of those wheels though.
Well what would you consider a good quality coil-over? I would prefer to have the car setup for fast road type driving, and most b-road's aren't very smooth, I guess you would need really good quality set like higher end Tein or Ohlins DFV or something like that which can cost more than the car itself.

[kopite72]

Lighter wheels defo but alot of people overlook the brakes. The stock calipers are a ton weight so going for a BBK can.knock a lot of weight off.

No need for coilovers unless you plan to take it on track. Top quality eibach springs will do just fine and are lighter than coilovers in any event

[Django91]

Lighter wheels defo but alot of people overlook the brakes. The stock calipers are a ton weight so going for a BBK can.knock a lot of weight off.

No need for coilovers unless you plan to take it on track. Top quality eibach springs will do just fine and are lighter than coilovers in any event

It's a good idea, but just wondering what options are best value. The rx8 brakes are pretty decent as standard, I've seen that just a set of good track pads themselves can make a big difference, so don't want to spend tooo much on brakes unless it really needs it. Don't plan on doing too many track days tbh.

You're right about the eibach springs they are pretty good, maybe roll bars as well?

[warpc0il]

More info here
viewtopic.php?f=58&t=82080
and here
viewtopic.php?f=19&t=58754
Prodrive went for Oz wheels to reduce the unsprung weight, as part of the package for the PZ.

The biggest benefit of reduced unsprung weight is in allowing the wheels to follow the contours of the road surface and maintaining grip, while not transmitting those forces to the chassis. This makes most difference when that surface is uneven, a very little difference if it were smooth.

Note that there can be a significant difference in tyre weights, that can make as much if not more difference than the wheels
viewtopic.php?f=24&t=51335

TBH for a road car none of this is going to make a difference sufficient to justify the cost, as you're talking about chasing that last 5% of performance.

Going back to your original question, most* aftermarket wheels are heavier than the Mazda OEM for the same size.
You have to watch the small print as some resellers quote weights for "popular sizes to enable comparison", so their entry for a 18" 8J may have a weight on that same page, that's for a 17" 6.5J

In the same vein, most* aftermarket coilovers would be a downgrade compared to the Mazda Sports Suspension, that was fitted to all our UK 8's (but as an option in US/JDM).

*"Most" as in numerically most common in the market, rather than most popular on this forum.

[kopite72]

Absolutely roll bars. I put eibach springs and Racing Beat ARB's on my 5 and it's a different car. Regarding a BBK, there are a lot of options, search on Google but if it were me I'd be looking at D2 performance kits and the kits on the Racing beat Europe site.

You say you don't want to spend a whole lot on a BBK but trust me on this you'll save a whole heap on unsprung weight by removing the stock calipers plus the BBK will look awesome

[Django91]

Absolutely roll bars. I put eibach springs and Racing Beat ARB's on my 5 and it's a different car. Regarding a BBK, there are a lot of options, search on Google but if it were me I'd be looking at D2 performance kits and the kits on the Racing beat Europe site.

You say you don't want to spend a whole lot on a BBK but trust me on this you'll save a whole heap on unsprung weight by removing the stock calipers plus the BBK will look awesome

Is that to do with aftermarket options being built out of lighter materials and maybe better manufacturing processes? Hmm, lets see, I want to keep my car for long if I can, and maybe later down the line might be tempting I am very much an OEM+ type of person, I respect Mazda's judgement on things as much as possible.

[Django91]

Again, you need to be careful choosing a Big Brake Kit, as most* are significantly heavier than the OEM brakes, and are more about posing than performance.

There are some BBK's that are lighter than OEM, but few of them include dust boots and other considerations that you'd apply to a road car. Some use light alloy caliper bodies and stainless steel pistons, which are fine on race tracks where salt is never applied, but can be a nightmare on UK roads.

An instructor at Anglesey Circuit was telling me about having to change their cars (MX-5 and Lotus) back to oem brakes because the sea air was causing issues with their race brakes.

Lighter brake discs can also reduce unsprung weight.

*Most common

[Django91]

More info here
viewtopic.php?f=58&t=82080
and here
viewtopic.php?f=19&t=58754
Prodrive went for Oz wheels to reduce the unsprung weight, as part of the package for the PZ.

The biggest benefit of reduced unsprung weight is in allowing the wheels to follow the contours of the road surface and maintaining grip, while not transmitting those forces to the chassis. This makes most difference when that surface is uneven, a very little difference if it were smooth.

Note that there can be a significant difference in tyre weights, that can make as much if not more difference than the wheels
viewtopic.php?f=24&t=51335

TBH for a road car none of this is going to make a difference sufficient to justify the cost, as you're talking about chasing that last 5% of performance.

Going back to your original question, most* aftermarket wheels are heavier than the Mazda OEM for the same size.
You have to watch the small print as some resellers quote weights for "popular sizes to enable comparison", so their entry for a 18" 8J may have a weight on that same page, that's for a 17" 6.5J

In the same vein, most* aftermarket coilovers would be a downgrade compared to the Mazda Sports Suspension, that was fitted to all our UK 8's (but as an option in US/JDM).

*"Most" as in numerically most common in the market, rather than most popular on this forum.

Hi Dave

Yes definitely agree with you on the merit of lighter wheels. In my opinion the PZ wheels don't look as nice as the standard rims, and I believe they have even larger +ve offset than the standard wheels making the wheel arches look weedy, maybe prodrive optimized the suspension geometry with this offset, but to me they don't look the part. They seem very sought after so they aren't going to be cheap either. I was hoping to go 8.5j at +35 or +40 offset, I would prefer close to the original offset in order to not alter the standard geometry too much. I was hoping to get a sort of flush to the fender look by having a slightly wider wheel, so it fills the arch better without compromising the roll centers/instant centers.

Well, if you're not driving on the track you're not looking for numbers, but just the way the car feels, and if it makes the car feel nicer/OEM+ then I'd be happy with that. I quite like the Bola FLB which is a flow forged wheel and they quote 8.1kg at maximum offset(+50) so seems decent to me.

I believe the Goodyear Eagle range is quite good tyre carcass weight wise, I feel the Asymmetric 5/SuperSport is a good lightweight option. I read a roadtest on tyrereviews where a set of these were about 10kgs lighter than the Vredestein Vorti in the compared size.

[SmuttyHutty]

I've got a PZ and a 192 so can comment a little here. The PZ has the standard PZ suspension with the Bilstein dampers and official springs and OZ wheels. And it rides hard, almost uncomfortably hard on some of the rural roads round East Anglia. I travel on the A1101 (the UK's lowest road as much of it is below sea level) to see BigPete and that road is bouncy, bumpy and undulating. I certainly do not hack along that road in the PZ.

The 192 had the standard (as Dave says UK Sports Suspension) but I swapped it out for the Mazda optional Sports Package suspension which is standard shocks and Eibach lowered springs. I did this because when I looked at the 192 next to the PZ it looked like a tractor with the massive wheel gap.

The end result of the suspension change is that the car still has the more comfortable ride of the original set up but a slightly lower stance which gives me more confidence in the corners. And I do bowl along the A1101 quicker in that car than the PZ. Oh, and I refurbed a set of PZ/OZ wheels and put them on the 192 because I prefer them to the standard rims.

[Django91]

I've got a PZ and a 192 so can comment a little here. The PZ has the standard PZ suspension with the Bilstein dampers and official springs and OZ wheels. And it rides hard, almost uncomfortably hard on some of the rural roads round East Anglia. I travel on the A1101 (the UK's lowest road as much of it is below sea level) to see BigPete and that road is bouncy, bumpy and undulating. I certainly do not hack along that road in the PZ.

The 192 had the standard (as Dave says UK Sports Suspension) but I swapped it out for the Mazda optional Sports Package suspension which is standard shocks and Eibach lowered springs. I did this because when I looked at the 192 next to the PZ it looked like a tractor with the massive wheel gap.

The end result of the suspension change is that the car still has the more comfortable ride of the original set up but a slightly lower stance which gives me more confidence in the corners. And I do bowl along the A1101 quicker in that car than the PZ. Oh, and I refurbed a set of PZ/OZ wheels and put them on the 192 because I prefer them to the standard rims.

This is quite interesting as I've read a lot of posts where the PZ is highly praised, but maybe it is really good on the track/smooth surfaces.
Yes the sports package came with the eibach pro-kit springs I believe and 235/40r18 tyres on a different wheel design.

I wouldn't recommend that tyre size over OEM though, to me on rough roads the lower sidewall makes it borderline harsh/rough and detracts from the plush feeling of the standard car, however that's just my experience and could be down to my tyre model choice, though this was a good brand/model.

[SmuttyHutty]

I'm sure some of our racing fraternity could get the best out of the PZ suspension on a track. But I drive on the UK roads and the 192 is brilliant.

[SmuttyHutty]

Controversial opinion incoming - I would wager that 99% of road-going RX8s will feel almost exactly the same with a slight reduction of unsprung (or sprung) weight beyond a little extra noise if losing interior weight. (ignoring placebo).

My 2c is that you'd be better off buying wheels that you think look nice, rather than something that you're buying just because it's light.

If you're a dialled in track driver and do so frequently then yeah, get the lightest wheels your wallet can stomach.

[warpc0il]

I justified my aftermarket wheels on the basis that;
- I liked them
- they're a brand I know and trust (Dotz Touge)
- they were (silly) cheap on Gumtree
- they're heavier than oem but lighter than OEM wheels with 23mm spacers, though the offset created the same effect.

20180703_105052.jpg

Currently running oem shocks, with Eibech ProSport springs and Racing Beat ARBs.
I have a set of PZ suspension units still sitting in a box, waiting for the last piece of the puzzle to arrive*

*

Spoiler:

tuit.jpg

[350matt]

I switched over to Pz shocks and it has been the single most effective mod I've done to the car
I was already on Tein springs which are very similar in rate to the PZ spring but I had to modify the shocks and make up new platforms in order to use the Teins ( meant for stock shocks) and the combination works very well
I found my cornering speed on my usual B road route was comfortably increased by 10 to 15mph

I'd strongly suggest that high quality shocks are the next step as lightweight wheels while nice will not be as big a step

[Django91]

I switched over to Pz shocks and it has been the single most effective mod I've done to the car
I was already on Tein springs which are very similar in rate to the PZ spring but I had to modify the shocks and make up new platforms in order to use the Teins ( meant for stock shocks) and the combination works very well
I found my cornering speed on my usual B road route was comfortably increased by 10 to 15mph

I'd strongly suggest that high quality shocks are the next step as lightweight wheels while nice will not be as big a step

I am sure the PZ suspension will be great on track, but whats it like on normal roads in the UK which are often rough and bumpy? There seem to be conflicting opinions about this.
You can make suspension stiffer with springs/ move to budget coil-overs in general, but without quality damping the car would struggle to keep contact with the road.

[SmuttyHutty]

Again, my tuppence worth here. If I were Dave (and I bow to his far greater knowledge and experience of these cars) I would stick with the set up he has. Standard shocks with Eibach ProSport coils gives the best of both worlds with a more comfortable ride and a lower stance and centre of gravity.

I've got a spare set of Eibach ProSport springs that I was looking to sell but I'll probably keep them in case anything happens to a spring on my 192.

Shame you're in Bath because I'd be happy for you to take both of my cars out and feel the difference for yourself. If you ever come to East Anglia for a long weekend give me a shout and the keys are yours.

[Django91]

Again, my tuppence worth here. If I were Dave (and I bow to his far greater knowledge and experience of these cars) I would stick with the set up he has. Standard shocks with Eibach ProSport coils gives the best of both worlds with a more comfortable ride and a lower stance and centre of gravity.

I've got a spare set of Eibach ProSport springs that I was looking to sell but I'll probably keep them in case anything happens to a spring on my 192.

Shame you're in Bath because I'd be happy for you to take both of my cars out and feel the difference for yourself. If you ever come to East Anglia for a long weekend give me a shout and the keys are yours.

Yes, so my car has both the Eibach springs and racing beat roll bars. I feel positively about the springs, but made changes to my tyres and roll bars together and since then the car started behaving quite poorly on bumps. Tyres in question are the Eagle F1 Supersport in 235/40r18 size, I understand these are at the extreme end of the 'road tyre' spectrum and there's the slimmer side wall so that may have been part of it, and then of course the roll bars increase the spring rate as well.

For reasons, my car currently needs some work done and at the moment I'm having to drive a completely standard car on GY Asymmetric 2 tyres, and to me the difference in compliance and just the tyres being connected to the road is night and day, on bumpy roads.So in hindsight, probably the best compromise is keep to the springs and roll bars but on the OEM size tyres and maybe a more road biased tyre like the AS2.

Forgot to update but I am based in Oxford currently, never been to Anglia but not too far out

[350matt]

I'm also in the oxford area so would be happy to take you out in mine, not sure on the how and the when at the moment of course

suspension feel is a very subjective and personal thing so there's no 'right' solution that suits everyone
and yes I'd agree tyre choice is critical I run the uniroyal rainsports on mine and made sure to go for the lower sidewall stiffness version to give a compliant primary ride
so I use a 235/40 R18 91Y rain sport 5 and rate them very highly for a road tyre however they do have a softer construction which reduces the steering precision so am considering some Vredestien Ultracs next or contisport contacts
is your version of goodyear eagle the 95 sidewall?
sadly the load rating number is only an indication of sidewall stiffness and not an exact figure so its not as cut an dried just going for lower sidewall number but 91 is 615 kg rating and 95 is 670kg so there's a reasonable step between the two

[Django91]

I agree with you on this being a subjective topic, unless you are really looking for certain things, most people won't notice the changes these things bring. I was just explaining tyre labels to someone yesterday, yeah you want to be looking for a spec close to the OEM tyre. Speed, load rating, ply these will affect tyre stiffness, rolling resistance, mpg's etc.

I believe thats what I'm guilty of, the Goodyears were atleast 95Y and XL rated, all of which probably made it a lot stiffer than normal.
Yeah I've never been in a PZ, would be cool to feel the difference even as a passenger.

Bit of a tangent but,I recently had the chance the drive the new MK8 VW Golf TSI, and this is probably not a fair comparison seeing the RX8 was conceived in the 90's and technology has moved on since then, but even if the car was softly sprung the damping was really amazing even in a non-GTI car and very good both on road and for spirited driving, granted it was on 16" wheels with more than generous 'padding'. Just made me wonder if there's ways to improve on the 8's suspension, which is sorta what got me thinking about the lighter rims and being careful to choose the right tyre etc.

[PJ_Parsons]

It is the tyres that are causing you problems. I use the Supersport, as they are a great track day tyre, wet and dry. The reason they are so good is that the the sidewalls are stiff and that does not translate to a comfortable ride. They are still a good road tyre, rain or shine if you can put up with the ride. I also use the Eagle F1 Assymetric 5 on my Swift Sport, a much better road tyre with nice ride compliance (softer sidewall). The Vredestein Ultrac Vorti, are quite a smooth riding tyre. You could also try a "touring tyre" like the new Bridgestone Touranza. I like to use the Tyre Reviews website. It has user and magazine tests, really helpful.