Pondering a "launch group buy" on a 4 pot brake kit for Mk2 15" OEM wheels...

[Keri-WMS]

As the title says, I designed a 280mm 4-pot front brake kit that just fits inside the Rev2> ("Turbo") 15" front wheels, but due to a lack of interest the bracket has never been machined!

This is a shame (especially as if there's a run of brackets made I can also have a set of WMS brakes on my own Mk2 under 15's! ), all I need is 2 or ideally 3 buyers to cover the cost of a run of brackets and make it worth doing - then I would have brackets on the shelf for the future.

So, we don't do group buys, BUT it now makes sense to me to offer a bigger discount to the first batch of customers to get this kit off the ground, as a complete one-off

After the initial sales, the price would then go back up to normal. I'm thinking an extra 2.5% discount on top of the existing discount I give IMOC members.

Any thoughts / interest?

Link to 280mm/15" info, pads/lines are extra as with the other kits:
http://www.imoc.co.uk/forums/viewtopic. ... c&start=46

This is probably for the 280x22 and 280x28 one-piece disc version - if people want the alloy bells+rotors version I'll need more buyers to justify it as putting the bells and rotors on the shelf ties up a lot more of our capital than just the brackets.

[Kongaroo]

Hi Keri,

As mentioned before I'm interested but just have a lot of things competing for the same modificaion budget at the moment (most recent one following the busted gt3071r is a slipping clutch ). However some extra discount is always going to be welcome

I'm a little confused by all the different options. I noticed from the original thread that the kit roughly maintained the stock brake bias but gave slightly better braking than the standard rev 3 setup. It was also significantly lighter.

How do these 2 new 15" setups compare with regard to the previous one that fit under 16" wheels in terms of performance, bias and weight saving?

What are the pros and cons between these 2 setups:

F: 4P158 bracket (side A) - 280x22 disc WMS 4-pot. Should be £435.34+vat
F: 4P158 bracket (side B) - 280x28 disc WMS 4-pot. Should be £492.71+vat

Also when you write in the original thread about keeping the calipers clean - what does this entail exactly? Curently I only jet wash my car periodically and the wheels/brakes are no exception - would this be an acceptable way to keep the calipers clean?

Sorry if these are dumb questions

[Keri-WMS]

Hi Kong - all reasonable questions!

These 280mm kits will be similar to the earlier 300mm ones in terms of weight, pedal feel etc etc - and of course are still a lot lighter and nicer in use than OEM.

The bias will still be very close to standard, and the drop from just under 300mm to 280mm isn't a major change and still slightly bigger than Rev 2>. Piston area changes have a much bigger effect on bias than slight changes in disc size.

In comparison between 280x22 and 280x28:

- 280x22 is lighter = better handling
- 280x28 is heavier = better thermal mass (=lower temperatures)
- 280x22 has better wheel clearance, but both fit the OEM 15" so this doesn't matter for this wheel, only deep-dish aftermarket ones maybe.
- 280x22 is cheaper!

To be honest for most people it'll be personal preference, we make the options available because if we can, we may as well (one bracket fits them all anyway!).

The occasional jetwash should be fine (the best time to give them a clean is before pushing the pistons back in when replacing pads).

[Kongaroo]

Thanks for answering my qustions Keri

So just to clarify - will the smaller/cheaper setup still have a peformance advantage in terms of more stopping power and less brake fade over the stock setup?

[Keri-WMS]

This is the "on paper" bias effect comparison of the calipers+discs only.

Rev 1 OEM = 60.5% f / 39.5% r

Rev 2 OEM = 58.0% f / 42.0% r

Rev 2 WMS = 57.0% f / 43.0% r < 280.0mm WMS front / Rev 2 OEM rear

Rev 2 WMS = 59.0% f / 41.0% r < 298.5mm WMS front / Rev 2 OEM rear

In reality you get a bit more from the WMS calipers as they work better (less losses in pad clip and slider friction).

As for fade, the 298.5x18 WMS seems to match or slightly beat the Rev 2 OEM with the same pad compound (I swapped the two setups over a few times on my car) - the WMS disc is lighter but bigger=better cooling.

The 280mm ones will have similar cooling to the Rev 2 disc, but less thermal mass (the 280x28mm one isn't too much different to Rev 2 though), but the pads get an easier life in a 4-pot caliper, plus the caliper cools faster being aluminium which conducts heat away from the pads faster.

So hard to call on the fade one other than "very similar" - but remember you can get better pads for your money with a WMS caliper, so the "fade resistance per £ spent on pads" will be better than OEM for sure and this is what matters at the end of the day for most people - the performance they get for their money.

[Kongaroo]

Cheers Keri - just a few more questions:

I notice the front brake bias on the 280mm kit is slightly less than the rev 2+ setup. Does this equate to longer stopping distance or does it not work like that?

What are the respective weights of the rev 2+ rotor in comparison to the 298 kit rotor and the thick and thin 280 kit rotors?

Lastly did you do a comparision between stopping distances between the 298 kit and the stock rev2+?

[Keri-WMS]

We can't infer stopping distances, these are affected more by road conditions, road coef of friction, shock rates, spring rates, wheel and tyre mass, tyre type, tyre width front, tyre width rear, tyre temurature, tyre pressure, tyre coef of friction and about a million other things.

What we CAN say is that you have better driver input with a 4-pot setup, and that your brakes are going to stop your car in a shorter distance if they are still working after abuse instead of overheated and faded.

Also as I mentioned, the loss of bias on paper is (A) tiny and (B) in the real world overcome by the more effecient mechanical function of the 4-pot caliper.

As for weight:

298.5x18 WMS disc = 5.0kg
296x28 WMS disc = 8.0kg
280x22 WMS disc = 5.7kg
280x28 WMS disc = 7.0 ish estimated

275x30 Rev2 disc = "7.6kg" according to Brembo

298.5x18 WMS when caliper is included:


Rev 2 when caliper is included:

[Kongaroo]

Ok no worries - I was referring more to a controlled conditions comparison on the same car/road/tyre setup. For eg. I know from my g-tech or racelogic Performance box that my Mr2 with stock brakes stops in a shorter distance than my MX5 with yellowstuff pads - but I do appreciate what you are saying.

Will the main difference in weight between the original kit and the new 280mm kits be in the weight of the diffierent rotors then?

If you could let me know the weights of the two 280mm disk options (when you get a chance to weigh them) I should be able to decide whether I want to go for one of the new 280 setups or not

[Keri-WMS]

Ok no worries - I was referring more to a controlled conditions comparison on the same car/road/tyre setup. For eg. I know from my g-tech or racelogic Performance box that my Mr2 with stock brakes stops in a shorter distance than my MX5 with yellowstuff pads - but I do appreciate what you are saying.

What I 'm getting at is that GRIP is the limiting factor in stopping distances, not brakes....unless of course you can't lock the wheels.

Will the main difference in weight between the original kit and the new 280mm kits be in the weight of the diffierent rotors then?

All the Mk2 MR2 WMS kits use the same calipers/pads/lines and brackets are within a few grams, so the only difference in weight is the various discs.

If you could let me know the weights of the two 280mm disk options (when you get a chance to weigh them) I should be able to decide whether I want to go for one of the new 280 setups or not

Done, see above (the 280x28 will only be machined when I sell a kit, so 'til then I don't know exactly what it will weigh, but very close to 7kg probably).

[Kongaroo]

Ok, I think I can see what you are getting at now - you'll have to excuse my noob questions as I have never used a big brake kit before.

Are you saying it's not really possible to do a controlled test stopping distance comparison of say 60mph to 0 in x feet (eg. as per my MX5 vs MR2 comparison) because both the stock brakes and the WMS brakes can lock the wheels?

Regarding the 280mm set - it's a tough call because to get the similar to stock fade resistance it would appear you need to gain 2kg in the rotor over the 298x18 rotor while losing a little bit of braking force (on paper anyway)?

I think on balance I would prefer to go with 298x18 and run a small spacer to fit inside the 15" TE37 or buddyclub if necessary. Car is currently at SBITS (where it seems to spend most of its life this past year for one reason or another - it's been a real shi*bag and I'm fast falling out of love with it ). Once I know what the damage is for the clutch/gearbox job I'll see if I can get the order placed

[Keri-WMS]

Ok, I think I can see what you are getting at now - you'll have to excuse my noob questions as I have never used a big brake kit before.

No problem!

Are you saying it's not really possible to do a controlled test stopping distance comparison of say 60mph to 0 in x feet (eg. as per my MX5 vs MR2 comparison) because both the stock brakes and the WMS brakes can lock the wheels?

That's basically it!

Regarding the 280mm set - it's a tough call because to get the similar to stock fade resistance it would appear you need to gain 2kg in the rotor over the 298x18 rotor while losing a little bit of braking force (on paper anyway)?

That's more or less it: Rev 2, WMS 298.5x18 and WMS 280x28 should all be very close to each other in terms of fade resistance - the Rev 2 has more thermal mass than the WMS 280x28, but the WMS caliper makes up for that by cooling faster. The WMS 298.5x18 has one step less mass again, but cools one step faster again due to the larger disc surface area.

I think on balance I would prefer to go with 298x18 and run a small spacer to fit inside the 15" TE37 or buddyclub if necessary. Car is currently at SBITS (where it seems to spend most of its life this past year for one reason or another - it's been a real shi*bag and I'm fast falling out of love with it ). Once I know what the damage is for the clutch/gearbox job I'll see if I can get the order placed

Fair enough, let me know how it goes.

[Keri-WMS]

I still want to do this - but I can't justify a batch just so I can get WMS 4 pots under 15" wheels on my own car...

I'm feeling underwhelmed!

[platmatt8]

Pm'd

[big_joe]

Just to give my experiences, I run the 298 4 pot set up with yellow stuff pads and the difference between this and stock brakes is night and day. I can lock the brakes at practically any speed, it gives serious braking force and great pedal feel (i run braided hoses allround too). The steering also feels a hell of a lot nicer thanks to the weight savings. Cant recommend this setup highly enough!

[Keri-WMS]

Cheers Joe!

[oddshoes]

Hi there

Could you PM me a price that you would be looking at for the set up for the stock 15s

many thanks

Dave

[Marmalade]

Just curious, has anyone fitted the full kit (front and rear) and if so, what did you do about the handbrake?

[Keri-WMS]

Sorry, only just spotted these replies!

This hasn't been run as a batch yet as the numbers weren't there - but:
A - There are a few more people intersted now
B - We have increased ability to run smaller CNC batches now, which makes it far more likely to happen.

There's a racecar running 298.5mm WMS 4-pot F+R in the Nippon Challange, but there's no current handbrake option. Again our increased CNC prototyping should help get an MR2 WMS handbrake rear caliper underway soon - apart from anything else I want this setup on my own car!

[chaos19810]

What would the cost for a front set up?

[greeny]

I'd be interested in a kit for front and rears aslong as they will fit under 15" wheels.

Handbrake isn't of major concern, an hydraulic one would suffice. (I know they're not road legal being hydraulic).