Compomotive haven't gone under, just the company that made the wheels for Compomotive have gone under. Compomotive are still trading / finding a new company to make wheels for them.

It would indeed.

I hope this explains it more - without having different style rims in the image.



Here, there is a larger positive offset but less spoke clearance than with the one on the right (which has smaller positive offset but larger spoke clearance).

And... here is the problem a bit with the Fiat Coupe... it has quite a large positive offset (40mm) but also needs large spoke clearance. The standard rims flow to the outside of the wheel (the spokes sit slightly proud if you lie the wheel on the ground with the backside on the surface), but many wheels have just straight spokes that don't go beyond the top surface of the barrel.

Kayjey is this why most people that buy the 17" team dynamic pro race 1.2's in a et 25 so there's room

Yups. Which is almost 50% out of spec.

On track cars I understand non-standard choices sometimes as going for lower offset will give you a wider track, which makes for changes in handling that may be positive. And parts are replaced on a regular basis so the extra wear and tear doesn't matter too much. But on a car used mainly on the road...

It's one of those thing I don't get about the lack of regulation with regards to MOT's. Sure, I don't get some of the regulations here neither, but at least it makes you think about 'why', rather that ''anything goed so I'll fit tires that are -80 offset and to make sure I comply with some weird rule about wheels sticking out I'll just pull out the wheel arches a good 6cm so all's well".

Klaas - despite my low offset figure, my track could not be any narrower - ultimately, we are looking at an increase in track of maybe 15mm each side - I doubt many people would notice the difference and I'm fairly confident that there have been no ill-effects on the handling on my car

Pretty sure many items contribute to the handling of your car Nigel! Anything written above should not be taking as extremely affecting the handling or causing instant failure. But it contributes to the general feel of the car. Indeed I doubt it would be instantly noticeable, but having had the joy of comparing a 17 inch (ET unknown) with extra spacers added and how it felt reluctant to turn in (admittedly also 245mm wide I believe and not the lightest wheels either) - and then the transformation and how much lighter and agile it felt on the way back...

Anyways... I always tend to be part of the gang that thinks a manufacturer has a lot of reasons to make a car as it is, and if you want to enhance the performance and handling, it'll be a case of meticulously investigating, measuring, trying and analysing (*). Trial and error WILL get you far, and the benefit of scale and many people trying different things here is a Big Plus. But I just want to say that there ARE drawback and you can't just lower the car 5cm, beef up the dampers and springs and get a 20mm wider track without affecting anything else.

Eg. as we've seen (and I believe you yourself were part of the thread) you can beef up the suspension to the point where you get rid of any compliance of certain parts (to the benefit of handling) but then concentrating the strain of the forces going through it all on other points which may then break or suffer wear. As said - a manufacturer will compromise on ALL parts, and if you want to get the best you will have to optimise ALL parts. People who run slick tires know which strains it can put on bearings, welds,... because of the added grip.

(*) Talking 'regular' cars here, not homologation specials where they deliberately turn down the power / disconnect extra injectors / ... I'm thinking Ford Cosworth RS500 for example, RX-7,... where a couple of magic tricks can do wonders because the manufacturers already prepared them for racing reasons.

I've been thinking about wheels again and got so fed up with the whole offset, track, caliper clearance thing, that I've drawn it p for my own clarity



Sick of seeing these types of images on the internet, I've tried to add some points of reference... i.e. car wheel arch bodywork, brake caliper, brake disc and, therefore, wheel mounting face.

I've done it for two wheels and (hopefully) it represents the difference between a standard 20vT wheel, and one of Nigel's wheels.

Standard wheel
7x16"
4x98
34ET
58.1CB

Team dynamics 1.2
7x17"
4x98
25ET
58.1CB

One of the things I found difficult to grasp was why a bigger offset brough the wheel into the car. I get it now!

I have also gained an appreciation of caliper clearance and now see that an important measurement for us, is the distance between the inside of the spokes and the wheel's inner mount surface. I measured it on my spare wheel set last night and it was 47mm. The caliper must stick out miles!

Another thing that was being touched on in this thread, was the increase in track due to an decrease in ET. Is it a fair statement that (for a wheel of equal width) the track increase by the same amount that the ET decreases?

I'm thinking a spreadsheet for wheel fitment will be created shortly...

Everyone knows that 15" are the future.

Going on with rolling circumference. It's easy to tell the difference on my lorry.

Our trucks are limited to 52mph.
My truck with worn tyres would do 51mph.
I had new rear tyres fitted and can now do 53mph.

I overtook another one of our lorries and when I got back to the depot, the other driver was complaining my truck was faster than his.
When I told him it was because I had new tyres fitted the whole place errupted in laughter.

They just couldn't understand the idea of a larger rolling circumference.
I had to draw a picture in the end.

The difference is significant on a lorry tyre.
My new tread depth is almost 25mm
plus they can have grooves cut into them as they wear down.
In effect reducing the circumference massively.
Thereby reducing the maximum speed irrespective of the speed limiter.
Which is why the tacho is calibrated fairly often.

Ok at last i have found a set of compomotive rims. They are 17 inch 98x4 with an ET 37.

Can anyone confirm that they will fit over the Brembo's please?

With that ET they should Joe. But I don't think anyone can say a resounding yes to your question! Is it possible to test fit?

Well the ET of a standard wheel is 34 so you'll be cutting it to close because you need a lower ET number to bring the wheel/spokes away from the caliper.

If my thinking is right they won't clear but I could be wrong

Remember that very important factor is what style are the spokes. Take a note that standard 16's have spokes curved to the outer side of the rim to clear the caliper.

This is with ET 35

But aren't the k sport calipers smaller in height but longer in length if you know what I mean. Standard calipers bulge out towards the spokes etc

True, forgot I had the Brembo's and these wheels, so here's a different picture

The wheel model number is MO1783 ET 37 17 x 8 inch.

I think i am going to take the coupe for a trial fit. Or are 8 inch to wide?

With a gap like that he should be fine then.

Seems like only a few months back that we had this conversation...

Anyway, here's a good website that allows you to tinker with the variables of a wheel to see how it all works and what it actually means. Helps my simple brain no end!!