BMW Z3 with Ferrari 250 SWB kit

[pingu393]

I'll ask the question here because it's relevant to building a kit car...

I'm building a Tribute, but basing it on an M Roadster (321 bhp). I can't use the standard M brakes as the calipers (not just the guides) would need to be ground too much. I'm looking at using E46 330 brake calipers, EBC Turbo Groove discs and EBC Redstuff pads.

Is there a calculator that I can use to determine if the braking force will be sufficient?

[Fastpedeller]

pingu393 said:

I'll ask the question here because it's relevant to building a kit car...

I'm building a Tribute, but basing it on an M Roadster (321 bhp). I can't use the standard M brakes as the calipers (not just the guides) would need to be ground too much. I'm looking at using E46 330 brake calipers, EBC Turbo Groove discs and EBC Redstuff pads.

Is there a calculator that I can use to determine if the braking force will be sufficient?

I thought the tribute panels fitted the z3 without problems - is it the wheel choice that's created the issue?

[pingu393]

Fastpedeller said:

pingu393 said:

I'll ask the question here because it's relevant to building a kit car...

I'm building a Tribute, but basing it on an M Roadster (321 bhp). I can't use the standard M brakes as the calipers (not just the guides) would need to be ground too much. I'm looking at using E46 330 brake calipers, EBC Turbo Groove discs and EBC Redstuff pads.

Is there a calculator that I can use to determine if the braking force will be sufficient?

I thought the tribute panels fitted the z3 without problems - is it the wheel choice that's created the issue?

Yes. 15" wheels are the smallest Z3 wheels available, but the car has calipers fitted that would only accept 17", maybe 16".

I want to know if 330 brakes can be upgraded to safely handle 300bhp / 350NM torque.

It looks like the braking force will be reduced by 10%, but the co-efficient of friction will be increased by 25%.

[V8RX7]

pingu393 said:

I want to know if 330 brakes can be upgraded to safely handle 300bhp / 350NM torque.

It looks like the braking force will be reduced by 10%, but the co-efficient of friction will be increased by 25%.

Of course they can - brakes don't handle power, they handle stopping, if after stopping 10 times from 100+ they start to fade - slow down for a minute !

Improve ducting and pad material if you want to drive it on track etc

[pingu393]

V8RX7 said:

pingu393 said:

I want to know if 330 brakes can be upgraded to safely handle 300bhp / 350NM torque.

It looks like the braking force will be reduced by 10%, but the co-efficient of friction will be increased by 25%.

Of course they can - brakes don't handle power, they handle stopping, if after stopping 10 times from 100+ they start to fade - slow down for a minute !

Improve ducting and pad material if you want to drive it on track etc

In that case I'll fit the ones from my pushbike !!

I've seen a website that shows some of the calculations. Not knowing Mu (co-efficient of friction) for the standard brakes is a bit of a problem. I can find Mu for Redstuff (0.5), but, strangely it's lower than Greenstuff (0.55) .


It looks like the calcs are...

Rubbing speed (@ 155mph) = 31 m/s (much more than 30 m/s means having to use ceramic brakes)

Current Piston Area = 2827 sq mm
330 Piston Area = 2552 sq mm

This means the force applied will be 90% of current force for the same brake pedal force (assuming I don't change the master cylinder)

Mu (Jurid) = 0.4
Mu (Redstuff) = 0.5

Clamping force = 2 . Mu . Piston Force

Piston Force = Piston Brake Pressure . Piston Area


Clamping Force (standard) = 2 . 0.4 . Piston Brake Pressure . 2827 = 2260 . Piston Brake Pressure

Clamping Force (330) = 2 . 0.5 . Piston Brake Pressure . 2552 = 2552 . Piston Brake Pressure


It looks like 330 brakes with Redstuff pads are 13% better than standard M brakes - but this is reliant upon accurate values for Mu.

[V8RX7]

pingu393 said:

In that case I'll fit the ones from my pushbike !!

It looks like 330 brakes with Redstuff pads are 13% better than standard M brakes - but this is reliant upon accurate values for Mu.

Yes if your pushbike weighs approximately the same as an M3 and has a similar top speed then they will be fine in exactly the same way 330 ones will.

You keep worrying / googling, what do I know - just been modifying cars for 30 years, those pesky 330's you see them crashing everywhere as they just don't stop

I know there's something wrong with your data / calc as there is no way on earth your conclusion is correct

[pingu393]

V8RX7 said:

pingu393 said:

In that case I'll fit the ones from my pushbike !!

It looks like 330 brakes with Redstuff pads are 13% better than standard M brakes - but this is reliant upon accurate values for Mu.

Yes if your pushbike weighs approximately the same as an M3 and has a similar top speed then they will be fine in exactly the same way 330 ones will.

You keep worrying / googling, what do I know - just been modifying cars for 30 years, those pesky 330's you see them crashing everywhere as they just don't stop

I know there's something wrong with your data / calc as there is no way on earth your conclusion is correct

Precisely my point. I can't find a conclusive way to calculate brake disc sizes and I can't find co-efficients of frictions for standard brake discs.

BMW fit 60mm pistons on M3s and 57mm pistons on 330s for a reason. That reason (I think) is because the 60mm piston will produce more clamping force for the same brake fluid pressure. The braking force is 2 x Mu x Clamping Force, so to regain the same braking force, I need to increase Mu by at least 10%. Will Redstuff do that? I THINK they will, but I can't prove it.

[V8RX7]

pingu393 said:

V8RX7 said:

pingu393 said:

In that case I'll fit the ones from my pushbike !!

It looks like 330 brakes with Redstuff pads are 13% better than standard M brakes - but this is reliant upon accurate values for Mu.

Yes if your pushbike weighs approximately the same as an M3 and has a similar top speed then they will be fine in exactly the same way 330 ones will.

You keep worrying / googling, what do I know - just been modifying cars for 30 years, those pesky 330's you see them crashing everywhere as they just don't stop

I know there's something wrong with your data / calc as there is no way on earth your conclusion is correct

Precisely my point. I can't find a conclusive way to calculate brake disc sizes and I can't find co-efficients of frictions for standard brake discs.

BMW fit 60mm pistons on M3s and 57mm pistons on 330s for a reason. That reason (I think) is because the 60mm piston will produce more clamping force for the same brake fluid pressure. The braking force is 2 x Mu x Clamping Force, so to regain the same braking force, I need to increase Mu by at least 10%. Will Redstuff do that? I THINK they will, but I can't prove it.

It's funny that when I doubled the power of my MX5 and left the brakes std - I didn't crash

Nor did I when I owned a Schnitzer supercharged BMW 330 - with completely standard brakes

It really is a non issue

[DonkeyApple]

It’s areguably much less of an issue with modern brakes. Historically it was rather important to ensure the brakes from the donor were suitable for the new use.

[pingu393]

I agree that there is PROBABLY nothing to worry about - that's why I'm so worried that I had already bought the discs and pads before I asked the question.

It was more a case of trying to prove through calculations that they should be ok, rather than doing a 100-0 brake test to find out .

They're here now, so I'll be going to my unit to find out what other modifications will be needed.

[V8RX7]

DonkeyApple said:

It’s areguably much less of an issue with modern brakes. Historically it was rather important to ensure the brakes from the donor were suitable for the new use.

Bearing in mind the MX5 is over 40 years old how historic do you wish to get ?

I had a Mark 1 Escort with 240 bhp around 5x it's original power, I upgraded to Capri legs / brakes because they were cheap and available

Equally I pulled into the drive with the front pads of my Starion Turbo on fire, after playing with some motorbikes 😂

[Fastpedeller]

pingu393 said:

V8RX7 said:

pingu393 said:

In that case I'll fit the ones from my pushbike !!

It looks like 330 brakes with Redstuff pads are 13% better than standard M brakes - but this is reliant upon accurate values for Mu.

Yes if your pushbike weighs approximately the same as an M3 and has a similar top speed then they will be fine in exactly the same way 330 ones will.

You keep worrying / googling, what do I know - just been modifying cars for 30 years, those pesky 330's you see them crashing everywhere as they just don't stop

I know there's something wrong with your data / calc as there is no way on earth your conclusion is correct

Precisely my point. I can't find a conclusive way to calculate brake disc sizes and I can't find co-efficients of frictions for standard brake discs.

BMW fit 60mm pistons on M3s and 57mm pistons on 330s for a reason. That reason (I think) is because the 60mm piston will produce more clamping force for the same brake fluid pressure. The braking force is 2 x Mu x Clamping Force, so to regain the same braking force, I need to increase Mu by at least 10%. Will Redstuff do that? I THINK they will, but I can't prove it.

As said up page, it's the weight of the car you are trying to stop, Some high performance cars are fitted with bigger brakes because the driver/car is expected to make repeated high-energy stops, therefore a more powerful car can get to high speed quicker suggesting it's more likely to get the brakes nearer to their limit in a given time. if you aren't prone to repeated, at-the-limit acceleration and braking then the extra power doesn't mean you need extra braking (for the same weight of vehicle) . It could be that a more powerful car (in the same manufacturer.s range) is fitted with larger brakes in order to 'differentiate' it/upgrade it from a 'lesser' model, even though the extra braking isn't needed?

[GTRene]

one came up for sale

https://www.ebay.co.uk/itm/Tribute-250-swb-Ferrari...

[saaby93]

GTRene said:

one came up for sale

https://www.ebay.co.uk/itm/Tribute-250-swb-Ferrari...

Is there anything else you can buy for £25k that looks like that?

[ukcerb]

pingu393 said:

I'll ask the question here because it's relevant to building a kit car...

I'm building a Tribute, but basing it on an M Roadster (321 bhp). I can't use the standard M brakes as the calipers (not just the guides) would need to be ground too much. I'm looking at using E46 330 brake calipers, EBC Turbo Groove discs and EBC Redstuff pads.

Is there a calculator that I can use to determine if the braking force will be sufficient?

If it helps the weight of the completed Tribute using front or centre laced wire wheels (a lot heavier than Z3 alloys) comes in at 60kgs less than a standard 2.8 Z3.

[pingu393]

I assume that you used 15" wheels.

What front brakes did you use? I'm trying to use 330 calipers on M Roadster carriers, and the amount of metal that I have had to grind off the calipers makes them dangerous. The thickness has had to be reduced from 22mm to 12mm. It's obviously not the way to go.

I've tried to...

1. 330 carrier, 330 caliper and 330 disc = carrier needs a spacer (5.75mm) to align it with the disc, and the caliper needs to be ground to allow the wheel to fit.
2. M carrier, 330 caliper, 330 disc = M carrier needed to be ground to allow the 330 disc to fit (M disc is 315mm, 330 disc is 325mm), and the caliper needs to be ground to allow the wheel to fit.
3. M carrier, 330 caliper, M disc = The caliper needs to be ground to allow the wheel to fit.

It looks like I may have two options...

1. Look at using 2.8 discs, carriers and calipers.
2. Look at using 16" rims

<edit>

I've looked at the 2.8 brakes and I don't think they will be up to the job.

2.8
Disc diameter = 286mm
Pad dimensions = 151 x 57
Power = 193bhp
Smallest steel wheel size = 15"

330 (E46)
Disc diameter = 325mm
Pad dimensions = 156 x 64
Power = 231bhp (and a heavier car)
Smallest steel wheel size = 16"

M
Disc diameter = 315mm
Pad dimensions = 156 x 63
Power = 321bhp
No steel wheels listed on RealOEM

Edited by pingu393 on Wednesday 22 July 21:29

[smash]

There's definitely been a Tribute coupe built based on a Z3M - it was the Dutch Tribute agent and it was on wires. Not sure if he's still around...

[GTRene]

smash said:

There's definitely been a Tribute coupe built based on a Z3M - it was the Dutch Tribute agent and it was on wires. Not sure if he's still around...

indeed, on a M roadster, was 'cheap' to buy, just 23k euro with just 117k km!, it made the roadster in a coupe.

Edited by GTRene on Thursday 23 July 01:05

[pingu393]

Thanks for finding that. I found this by reverse searching the images you posted...



I can't tell the size of the tyres, but they look like 17". I'm going to source a cheap 16" wheel and see if I can make it fit. At least I am now confident that 15" is too small, unless you are basing the build on a 2.8 (or smaller).

[GTRene]

pingu393 said:

Thanks for finding that. I found this by reverse searching the images you posted...

I can't tell the size of the tyres, but they look like 17". I'm going to source a cheap 16" wheel and see if I can make it fit. At least I am now confident that 15" is too small, unless you are basing the build on a 2.8 (or smaller).

http://www.righthanddrivesportscars.nl/page26.html