Lightweight wheels - do they make any difference on a Chim?
Discussion
I am coming from the miata world and this means that I strongly believe in the positive affects of lightweight wheels.
I used 6kg alloys on my first mx5 than one day when I found my car standing on bricks I decided to buy sexy looking wide wheels as others did.
Tramlining, scuttle shake, stubborn behaviour was the result. I ruined the legedary playful handling of the miata.
I sold those boat anchors and went through several sets of lighter and lighter wheels, the last set was lighter than 15kg. The whole set.
Now I have a Chimaera on OEM wheels. The alloys weigh between 8-10kg each while there are sub 5kg alloys available in the needed size for reasonable money.
I don’t want to spend money on something that was done by others and proved to be not working so I ask here first.
Anyone with any first hand experience about the affect of really lightweight ( <5kg ) wheels on a Chimaera?
Thanks in advance for your thoughts /advice!
I used 6kg alloys on my first mx5 than one day when I found my car standing on bricks I decided to buy sexy looking wide wheels as others did.
Tramlining, scuttle shake, stubborn behaviour was the result. I ruined the legedary playful handling of the miata.
I sold those boat anchors and went through several sets of lighter and lighter wheels, the last set was lighter than 15kg. The whole set.
Now I have a Chimaera on OEM wheels. The alloys weigh between 8-10kg each while there are sub 5kg alloys available in the needed size for reasonable money.
I don’t want to spend money on something that was done by others and proved to be not working so I ask here first.
Anyone with any first hand experience about the affect of really lightweight ( <5kg ) wheels on a Chimaera?
Thanks in advance for your thoughts /advice!
Edited by Supercharged5 on Saturday 22 May 19:21
Edited by Supercharged5 on Saturday 22 May 20:48
So few options and the fact most people quite like the original look suggests not.
As a road car light wheels get buckled easily on these cars due to the firm suspension and unforgiving chassis.
For the minimal performance gain you’d get from such light wheels the risk of damage is far greater IMO.
I noted how solid my Imola wheels were which sort of tells me Tvr knew this. They must surely absorb vibrations and deflections to some extent so keeping those vibrations from transmitting through the chassis of which you would notice.
That’s my theory
There’s only one way to find out.
Putting the cars on bigger wheels has a similar effect as you run lower profile tyres but I have found using a soft all weather tyre those vibrations can be negated so it depends on the tyres you run to some extent.
As a road car light wheels get buckled easily on these cars due to the firm suspension and unforgiving chassis.
For the minimal performance gain you’d get from such light wheels the risk of damage is far greater IMO.
I noted how solid my Imola wheels were which sort of tells me Tvr knew this. They must surely absorb vibrations and deflections to some extent so keeping those vibrations from transmitting through the chassis of which you would notice.
That’s my theory
There’s only one way to find out.
Putting the cars on bigger wheels has a similar effect as you run lower profile tyres but I have found using a soft all weather tyre those vibrations can be negated so it depends on the tyres you run to some extent.
Absolutely, GB's third world standard roads, they are truly shocking, as my daily inspection of various cars' wheels proves.
I've not driven in Hungary, but we have driven annually in Portugal since '98 where the roads (whilst not as good as they were immediately after they copped a truck load of Euros in the early noughties) are fantastic compared to here.
I've not driven in Hungary, but we have driven annually in Portugal since '98 where the roads (whilst not as good as they were immediately after they copped a truck load of Euros in the early noughties) are fantastic compared to here.
There are lightweight wheels available in 15x7 with the right offset but they look just not right on the chimaera.
OZ Ultra/superleggeras are about 5kg in this size.
For the rear there are options as well, König produces very good wheels in 16x7, and 8 with correct pcd and good enough offset.
16x8 et40 König Dekagram weighs 6,6kg, strong flow formed wheel.
But how will they form a set? And how they match the lines of the car? I have no idea.
This would look perfect on our cars, also the size 17x8 and et40 seems to be good. They are light for the size but the overall weight improvement would be small.
https://www.ebay.com/itm/4-New-17X8-Konig-Hexaform...
OZ Ultra/superleggeras are about 5kg in this size.
For the rear there are options as well, König produces very good wheels in 16x7, and 8 with correct pcd and good enough offset.
16x8 et40 König Dekagram weighs 6,6kg, strong flow formed wheel.
But how will they form a set? And how they match the lines of the car? I have no idea.
This would look perfect on our cars, also the size 17x8 and et40 seems to be good. They are light for the size but the overall weight improvement would be small.
https://www.ebay.com/itm/4-New-17X8-Konig-Hexaform...
Edited by Supercharged5 on Sunday 23 May 13:42
Edited by Supercharged5 on Sunday 23 May 14:16
I must admit i've never understood it when people say that a lighter wheel has made the ride better ..
if you think about it logically the first part of the bump is absorbed by the tyre, which is transferred into the wheel, which is transferred into the spring/damper then the body.
Anything which isolates the body from the bump will improve ride, so a very very very heavy wheel will mean more of the bump is absorbed by the tyre, and less is transferred into the suspension / body ... and vice versa.
There is the argument that with light wheels you need less damping, but unless you have multi adjust dampers you cannot separate out the high speed damping which is controlling the light wheel from the low speed damping which is controlling the heavy body mass. As such you would be hard pushed to achieve any meaningful damper changes by just a change to wheel mass.
critique my reasoning please
In other news, a light wheel is easier to accelerate, both linearly (as in it reduces the total mass of the car) and also radially .. so just like a light flywheel will effectively transfer more power to the rest of the drivetrain during acceleration in a low gear, so a light roadwheel will transfer more power to the tyre contact patch during similar low gear acceleration, its effect diminishing as the gear ratio lengthens.
Similarly a heavy wheel carries more inertia therefore modulating brake lock up point should be more easily achieved with a light road wheel, at least for people with good braking technique.
There are many benefits for light weight components .. just undecided if absolute ride quality is one of them ..
if you think about it logically the first part of the bump is absorbed by the tyre, which is transferred into the wheel, which is transferred into the spring/damper then the body.
Anything which isolates the body from the bump will improve ride, so a very very very heavy wheel will mean more of the bump is absorbed by the tyre, and less is transferred into the suspension / body ... and vice versa.
There is the argument that with light wheels you need less damping, but unless you have multi adjust dampers you cannot separate out the high speed damping which is controlling the light wheel from the low speed damping which is controlling the heavy body mass. As such you would be hard pushed to achieve any meaningful damper changes by just a change to wheel mass.
critique my reasoning please
In other news, a light wheel is easier to accelerate, both linearly (as in it reduces the total mass of the car) and also radially .. so just like a light flywheel will effectively transfer more power to the rest of the drivetrain during acceleration in a low gear, so a light roadwheel will transfer more power to the tyre contact patch during similar low gear acceleration, its effect diminishing as the gear ratio lengthens.
Similarly a heavy wheel carries more inertia therefore modulating brake lock up point should be more easily achieved with a light road wheel, at least for people with good braking technique.
There are many benefits for light weight components .. just undecided if absolute ride quality is one of them ..
Edited by spitfire4v8 on Thursday 27th May 09:07
I'm probably completely wrong, but won't a heavy wheel be better on bumpy roads. If a wheel leaves the surface won't the weight of a heavy wheel tend to extend the spring/damper faster because of the increased weight thereby restoring contact with the surface quicker . The lighter the wheel , the longer it will take for contact to be restored resulting in more bump steer and a bumpier ride .
It depends (as with lots of things ..)
if the wheel is very heavy, and the tyre is very very voluminous and soft sidewalled, then you could have all the bump being taken by the tyre and almost none transferred into the wheel, or further up the suspension.
If however you have a very low volume, stiff sidewalled tyre, then less of the bump will be absorbed by the tyre, and more will transfer into the wheel, and further up the suspension ..
There is a conflict between ride and handling in that in the situations ive talked about if you have a very heavy wheel which is resistant to movement then the tyre takes more of the bump absorption, this is bad for handling because what you try and achieve for stable handling and consistent grip levels is to minimise the tyre contact patch load changes, that means you need the wheel to follow the bump and the tyre to not distort and therefore disrupt the contact patch load very little to give consistent grip levels.
In effect you try to isolate the wheel from the body so that the body can remain stable but the tyre follow the bumps as faithfully as possible. This is why a high quality damper can give good ride and good consistent grip levels, because through complicated valving you can reduce the bump transmission into the body whilst allowing the wheel and tyre the ability to follow the road surface ..
if the wheel is very heavy, and the tyre is very very voluminous and soft sidewalled, then you could have all the bump being taken by the tyre and almost none transferred into the wheel, or further up the suspension.
If however you have a very low volume, stiff sidewalled tyre, then less of the bump will be absorbed by the tyre, and more will transfer into the wheel, and further up the suspension ..
There is a conflict between ride and handling in that in the situations ive talked about if you have a very heavy wheel which is resistant to movement then the tyre takes more of the bump absorption, this is bad for handling because what you try and achieve for stable handling and consistent grip levels is to minimise the tyre contact patch load changes, that means you need the wheel to follow the bump and the tyre to not distort and therefore disrupt the contact patch load very little to give consistent grip levels.
In effect you try to isolate the wheel from the body so that the body can remain stable but the tyre follow the bumps as faithfully as possible. This is why a high quality damper can give good ride and good consistent grip levels, because through complicated valving you can reduce the bump transmission into the body whilst allowing the wheel and tyre the ability to follow the road surface ..
Also do tyre weights vary by much.
Having fitted Brembo brakes to my Chim I’ve observed these changes which are purely feel based rather than scientific fact as I rather foolishly never weighed them up against the original caliper/disc/ pad combo.
The combined weight of the brembo set up with extra fitting bracket and 324 mm Brembo discs I feel is heavier overall but not by a huge amount.
I had 17 in wheels on my car before so it’s only the brake change I’m having to consider.
Basically the car does seem to hug the road more at the front over bumps but where there is a positive effect there has to be a negative so as the wheel / hub / brake set up is heavier you ideally want slightly harder bump settings but on my car on the road it seems to work really well as I try and have a more forgiving set up anyway so it just absorbs more with less movement. Softens it down sort of thing.
Decent shocks you wouldn’t notice it much at all.
Lighter wheels do give more feedback in my view and do exactly as Joolz mentions.
I do run RS3 tyres which have a big part to play. Tyre choice dictates other factors very much so.
Having fitted Brembo brakes to my Chim I’ve observed these changes which are purely feel based rather than scientific fact as I rather foolishly never weighed them up against the original caliper/disc/ pad combo.
The combined weight of the brembo set up with extra fitting bracket and 324 mm Brembo discs I feel is heavier overall but not by a huge amount.
I had 17 in wheels on my car before so it’s only the brake change I’m having to consider.
Basically the car does seem to hug the road more at the front over bumps but where there is a positive effect there has to be a negative so as the wheel / hub / brake set up is heavier you ideally want slightly harder bump settings but on my car on the road it seems to work really well as I try and have a more forgiving set up anyway so it just absorbs more with less movement. Softens it down sort of thing.
Decent shocks you wouldn’t notice it much at all.
Lighter wheels do give more feedback in my view and do exactly as Joolz mentions.
I do run RS3 tyres which have a big part to play. Tyre choice dictates other factors very much so.
Edited by Classic Chim on Tuesday 25th May 10:00
I was just referring to wheel weights assuming the same tyre and suspension characteristics . After all simply put it's a mass on the end of a spring with the single or two stage velocity damping.
You can get even more complicated taking into account fundamental modes of chassis vibration, pitch, heave and yaw
You can get even more complicated taking into account fundamental modes of chassis vibration, pitch, heave and yaw
Edited by glow worm on Tuesday 25th May 10:37
Scientific approach:
https://core.ac.uk/download/pdf/14697847.pdf
Sprung/unsprung weight ratio seems to be an important factor in the design of a vehicle.
If it is 100:1 for sprung weight or the opposite 100:1 for unsprung weight it is easy to imagine that the ride would be very different on not perfectly smooth surface.
It’s like a big heavy luxury vehivcle vs a light weight coach on big heavy wheels.
https://core.ac.uk/download/pdf/14697847.pdf
Sprung/unsprung weight ratio seems to be an important factor in the design of a vehicle.
If it is 100:1 for sprung weight or the opposite 100:1 for unsprung weight it is easy to imagine that the ride would be very different on not perfectly smooth surface.
It’s like a big heavy luxury vehivcle vs a light weight coach on big heavy wheels.
spitfire4v8 said:
I must admit i've never understood it when people say that a lighter wheel has made the ride better ..
if you think about it logically the first part of the bump is absorbed by the tyre, which is transferred into the wheel, which is transferred into the spring/damper then the body.
Anything which isolates the body from the bump will improve ride, so a very very very heavy wheel will mean more of the bump is absorbed by the tyre, and less is transferred into the suspension / body ... and vice versa.
There is the argument that with light wheels you need less damping, but unless you have multi adjust dampers you cannot separate out the high speed damping which is controlling the light wheel from the low speed damping which is controlling the heavy body mass. As such you would be hard pushed to achieve any meaningful damper changes by just a change to wheel mass.
critique my reasoning please
In other news, a light wheel is easier to accelerate, both linearly (as in it reduces the total mass of the car) and also radially .. so just like a light flywheel will effectively transfer more power to the rest of the drivetrain during acceleration in a low gear, so a light roadwheel will transfer more power to the tyre contact patch during similar low gear acceleration, its effect diminishing as the gear ratio lengthens.
Similarly a heavy wheel carries more inertia therefore modulating brake lock up point should be more easily achieved with a light road wheel, at least for people with good braking technique.
There are many benefits for light weight components .. just not sure ride quality is one of them ..
Some of your reasoning is good, some not so good...if you think about it logically the first part of the bump is absorbed by the tyre, which is transferred into the wheel, which is transferred into the spring/damper then the body.
Anything which isolates the body from the bump will improve ride, so a very very very heavy wheel will mean more of the bump is absorbed by the tyre, and less is transferred into the suspension / body ... and vice versa.
There is the argument that with light wheels you need less damping, but unless you have multi adjust dampers you cannot separate out the high speed damping which is controlling the light wheel from the low speed damping which is controlling the heavy body mass. As such you would be hard pushed to achieve any meaningful damper changes by just a change to wheel mass.
critique my reasoning please
In other news, a light wheel is easier to accelerate, both linearly (as in it reduces the total mass of the car) and also radially .. so just like a light flywheel will effectively transfer more power to the rest of the drivetrain during acceleration in a low gear, so a light roadwheel will transfer more power to the tyre contact patch during similar low gear acceleration, its effect diminishing as the gear ratio lengthens.
Similarly a heavy wheel carries more inertia therefore modulating brake lock up point should be more easily achieved with a light road wheel, at least for people with good braking technique.
There are many benefits for light weight components .. just not sure ride quality is one of them ..
“bumps“ come in lots of shapes and sizes. No bump is absorbed completely by the tyre, though smaller amplitude higher, higher frequency stuff has a tendency to not be as transmitted so perfectly into the body as very low frequency stuff.
So, back to your point...the tyre passes over a bump, the tyre is deformed, but to deform the tyre it needs to also generate a force on the wheel, the wheel is accelerated upwards, some of the force is transmitted through the damper (it also absorbs/decays/dissipates some of the bump energy) to the body, some through the spring into the body, and some through the suspension links into the body.
A very heavy wheel will not really cause a tyre to provide better ride, because tyres (contrary to popular opinion) don‘t have much damping really, so a heavy wheel will still be accelerated upwards and give the damper more work to do. A series of bumps could then also more easily excite the vibration of the wheel/unsprung mass... which makes the ride feel harsh, and isn‘t good for grip.
Dampers are not simple components. Every damper has low and high speed damping characteristics... and every oscillation of the damper passes through the low speed area... the lighter wheel/unsprung mass will have a higher natural frequency than the heavier wheel/unsprung mass. If you had a damper that was struggling to dampen wheel/unsprung mass frequency vibrations and you then fitted light wheels you might then see a huge improvement in ride. If you had a damper that was already having an easy time controlling the wheel/unsprung mass then fitting a heavier wheel, like you said, might have little or no perceptible effect on the ride.
So, it‘s not simple... but I think you knew that anyway.
Supercharged5 said:
Scientific approach:
https://core.ac.uk/download/pdf/14697847.pdf
Sprung/unsprung weight ratio seems to be an important factor in the design of a vehicle.
If it is 100:1 for sprung weight or the opposite 100:1 for unsprung weight it is easy to imagine that the ride would be very different on not perfectly smooth surface.
It’s like a big heavy luxury vehivcle vs a light weight coach on big heavy wheels.
Very interesting ... However seems very aimed at electric vehicles and motors in the wheel or not... and one main assumption with the 1/4 Model is that they assume the tyres don't loose contact with the ground and only model in 2 dimensions with no account for roll and yaw. if I'm understanding it correctly.https://core.ac.uk/download/pdf/14697847.pdf
Sprung/unsprung weight ratio seems to be an important factor in the design of a vehicle.
If it is 100:1 for sprung weight or the opposite 100:1 for unsprung weight it is easy to imagine that the ride would be very different on not perfectly smooth surface.
It’s like a big heavy luxury vehivcle vs a light weight coach on big heavy wheels.
Key outcome variable damping characteristics which I think the aircraft industry and Automotive Products discovered over 40 years ago with adaptive undercarriage design.
Kawasicki said:
No bump is absorbed completely by the tyre, though smaller amplitude higher, higher frequency stuff has a tendency to not be as transmitted so perfectly into the body as very low frequency stuff.
at high frequencies the heavy body cannot react quickly because of its inherent inertia, but also most dampers are much less resistive at low piston speeds anyway so those two are conflicting situations in that at low piston speeds the spring/damper absorbs proportionately more of the bump and at high piston speeds more of the tyre absorbs the bump - the upshot being that a manufacturer presumably chooses their tyres carefully as part of their package .. but what i was getting at is that the heavier the wheel the less any bump is transferred to the suspension thence body because of the wheel's inherent inertia .. I accept this as a flawed concept and really i was musing it in my mind thinking over the transmission path of the force from road surface through to car body, and what has to move and in what way ..however this was just a side show off the back of the point of lighter wheel = better ride, which I possibly both agree and disagree with
. Because of the myriad benefits to running a light wheel it would almost always be preferable to run the lightest you could keeping in mind structural integrity.Edited by spitfire4v8 on Thursday 27th May 09:06
Edited by spitfire4v8 on Thursday 27th May 09:09
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