Brembo 4 pot brakes

[Sptwoman]

I need some basic advise on disc / caliper tolerances please. I have a full set of radial Boxster 4 pot calipers, which I intend to fit to my car. The Boxster disc spec is 292X20R and 298X24F. The 164 discs I'm considering are 284X22F 12V and 281X26F 24V. Is there anything I should consider when chosing the discs and are there other alternatives (5 stud) apart from having them made? One thing I have noticed on the calipers, they have what I call guides which restrict the thickness of disc. Could they be removed or shaved a few MM's?
Also when making radial mounts, using wood as a template, is there some easy process to follow / best practice I should follow?

[chris.richard]

I have a pair of adapters to fit Brembo 4 pot calipers to a 164. Brembo make discs, and you'd need a bell (top hat) to mount the disc on. I have no immediate need for the adapters, and would be happy to lend them so that they could be copied. Offsets etc would need to be calculated!

[chris.richard]

In place on a 164 strut

[chris.richard]

disc/bell combo. Discs ?308mm diameter?

[chris.richard]

P.S. Those are 17" wheels

[strat6v]

The pins are there to stop the pads moving and have no real use with the disc for centering. If you can mount the caliper on the mill ok, i'm sure you could take off a smidge but remember that as the pad wears and moves across it still needs to but up against the pin.

As far as a bracket goes, assemble your hub and disc (same size all round on mine), sit the caliper on and just shim it up a bit so it doesn't catch on the disc, make sure your rim fits over this. If thats ok, take off the rim, measure from bolt hole c/l on the hub carrier to the caliper body, machine a block to that size making sure the top and side are square. You can always shim a bit beween block and caliper. Once you have that done you can then mark the mounting holes exactly for the caliper. Just remember to leave the block full thickness till the caliper is mounted then skim some off the back.

Anybody know a suitable grad aluminium to make the caliper mounts from :confused:

[Sptwoman]

Thanks for the offer Chris, The pic is good enough to realise the general shape for the front. The back is less fiddly I believe. Where did yousource your ali blocks from and what size are they? I think Rally design stock them and I've seen a user on ebay too. What spec should the ali be?

Thanks for the advise John. By placing the caliper over the disc, I should be looking to have the disc centre but what kind of gap should I have between the disc outside circumference and the caliper? I also found out the Boxster's use an ehub on the rear for a handbrake!

[chris.richard]

Where did yousource your ali blocks from and what size are they?

I got them from somebody on the 164 forum - he had 2 sets made when he fitted them to his 164. They're 160 x 36 x 56mm. Holes are 12mm coarse thread.

[chris.richard]

Forgot to say, radial mounts are 130mm centres. Would fit Brembo 20.5187.30

[chris.richard]

Another photo

[Sptwoman]

Chris, Can I change my mind and lend the adapters please? Will PM my details

[Chris J]

Anybody know a suitable grad aluminium to make the caliper mounts from :confused:

I'll ask Mr. Ralloy

[colin artus]

HE30 is the stuff to use.

[strat6v]

Thanks for that Colin, took a flyer and bought some biggish billets of HE30 at Donnington, back end of last year. Looking forward to having a dabble making my brackets, first job for the milling machine (and myself) :eek:

[kens]

Also, you can consider an adapter from the following source. http://search.ebay.com/_W0QQsassZubraun64QQhtZ-1

example on ebay item 290075876372

[Sptwoman]

I've seen these on ebay but it's just as "easy" to have them made locally to your exact spec.
Good news, I've used a 12V front disc and offered the caliper to it and my coffin wheel fits with a good 10mm inside gap minimum :) So i've got a bit to play with.
Question: The calipers were originally to fit on discs 292X20R and 298X24F. Any comments on using The 164 discs 284X22F 12V on the rear and 281X26F 24V on the front? Maybe the same all round? What other production discs have people used without going to the great expensive of bells etc?

[strat6v]

As long as the pad sweeps as much of the disc as possible, stick with the 284 alfa discs all round, one less variable. My plan was use the same caliper front and rear, vary the master cylinder sizes as necessary and fine tune with the balance bar.

Comments please :confused:

[chris.richard]

Front and rear discs have completely different offsets.

[Sptwoman]

John, That's my plan. The Boxster calipers look identical front/rear apart from the piston sizes. I'm looking to use the same Alfa 164 front discs all round. Not too sure on the disk thickness though! Are there other options?

[kens]

Disk dimensions are available on the Brembo website. However, it is not so friendly to find the info. Disk dimensions are listed under Sports Catalogue.

The 284 discs are 22mm in width. If wheel size permits, and you are using the 5x98 pattern. The GTV disc goes to 305 mm with a 28 mm width.

Regards,
Ken

[Sptwoman]

Ken, I'm thinking on sub 300mm disk but I'm concerned with the disc thickness as the original spec for the calipers are for discs 292X20R and 298X24F. Is there a rule to bear in mind when using discs of lesser thicknesses? I'll have a look at other Alfa applications to check out the spec/offset.

[kens]

Here is a point of reference on the 305 mm discs. I have an Alfa spider with 305 mm discs and four pot Brembo calipers. The 305 mm brake disc requires at least a 16 inch wheel. Yesterday it was discovered that the spare tyre only mounts onto the rear and a 15 inch wheel won't clear the calipers in front.

Of course, there could be exceptions to my statement that 15 inch wheels do not work with 305mm discs. Yet, I would bet good money against a combination of 305 mm discs with 15 inch wheels using four pot Brembo calipers.

Ken

[Sptwoman]

I've made my wooden caliper adapter templates out of 25mm thick oak and could do with some advise before I convince a machinist to make them. I'm looking to use the Rally Design ali blocks 190X25X50 as the source of material. I've attached some pics of the templates. To ensure the caliper mounting holes are central to the adapter I'll need to machine a 10mm recess into the lug mounting area on the side. It's that or shelling out more dosh on custom made bells!!

[Sptwoman]

Pic in 3D ...

[Sptwoman]

Caliper mounting surface showing mounting hole positions if no recess made..

[strat6v]

Does that leave you 15mm of material? Should be ok but don't quote me on it!! I'm in the same boat so it's try it and see if it breaks :eek:

[Sptwoman]

John, I've asked Roger001 for advise since he's already done this without problems, in race conditions!! He mentioned that you should have approx 10mm thickness at the mounting face. With the recess I'll have 15mm at the face and then a full 25mm for the caliper mount / away from the mounting surface. Don't fancy the try it and see if it breaks / brakes approach !!

[strat6v]

I'm generally belt and braces so most things i make weigh way too much and are strong enough to take the weight of a double decker bus :D

[chris.richard]

Anybody know a suitable grad aluminium to make the caliper mounts from :confused:

Got this reply on PH

Use at least HE30 but preferably HE15, you don't compromise with brakes

[Sptwoman]

Well they're machined and fitted. The fronts were perfect 1st time...

[Sptwoman]

While the rears had to be tweeked...

[Sptwoman]

I'm quite happy with the results... now it's calculating the master cylinder sized :confused:

[Sptwoman]

I've been reading up on how to calculate the m/c sizes. Has anyone used this site (http://www.tiltonracing.com/content.php?page=faq&view=9)?
I've also been reading up on pedal ratios since I don't realy want to use a servo but the standard installation is 4:1.... apart from hacking away and fitting a hanging box, has anyone mod'd the existing install. The pedal to pivot in 8" and aft 2" so to move towards a 6.1 / 5:1 ratio is tricky :mad:

[strat6v]

Have you got the standard pedal set up or a tilton pedal box? I went through this scenario a long time ago. If you mod the standard pedal ratio then the travel is too much or there's not enough leverage on the pedal. Options are tilton pedal assembly which mucks up the front bulkhead area, 131 servo with Bob sharp mod( but you don't want a servo?) twin circuit remote servo or make a underdash linkage pedal box (a bit like mine :) ) i'm just about to start a mark two version out of sheet steel, suitably lightened of course. ;)

[Sptwoman]

I've been reading about mod'g the existing pedal setup and John Rutter has mod'd (http://www.stratossupersite.com/forum/showthread.php?t=1821&highlight=sharp) his and wrote an article!!! Can't find it in the newsletter or details on the forum !! Help!! Also, Bob Sharp is mentioned but think reverted back to servo(s)

[strat6v]

However you mod the pedal you won't get what you want, all swings and roundabouts. The only way is a servo or some longer pedals.

[Sptwoman]

John, I'm coming to that conclusion :mad:

[strat6v]

So if i'm making one for myself, do i make a second one at the same time? :)

[Sptwoman]

Looking at the quality of your fabrications to date, I'd certainly be interested in your design and how it fits into the existing space. Is it in your head or on paper? Something on the lines of the MK1??

[strat6v]

I'm going to keep it a linkage setup with the cylinders and balance bar in similar places but using a pull linkage instead of the overhead push linkage i made before. Definitely more compact, stronger and lighter. I'll be starting with it this week on evenings, once it's operational, i'll send you some pics. the pedal should be around 30% longer than standard,(using the pedals i already made up) allowing a 6 to 1 ratio with plenty of cylinder/piston travel and sensible pedal travel. All fully adjustable for pedal positions to suit different drivers. Pedal pivots on bearings etc. Leaves room for operational dash vents too.

[SUSIT]

Would it be possible to use the tilton floor mounted pedal assembly in a Hawk
If I remember its a 6:1 ratio

[Sptwoman]

After reading your description of the work you put in to install the box :eek: Saying that, it does look good ;) so i could be tempted...

[strat6v]

Steve, that right hand cylinder would go straight through the box section, next to the rh bottom arm pick up point, not good :eek: Are you fitting residual pressure valves on the cylinders with them being that low?

[SUSIT]

Steve, that right hand cylinder would go straight through the box section, next to the rh bottom arm pick up point, not good :eek: Are you fitting residual pressure valves on the cylinders with them being that low?


On the Allora the cylinders run under a box section that runs across the front of the bulkhead and just clears the bottom arm inner pickup. It was a close call to if we could make it fit.
My build manager is not convinced they will be necessary, however we are open to debate and could be convinced otherwise.
Has anyone experience of this type of setup?

Stephen

[strat6v]

I think it mentions it in think auto's catalogue, maybe rally design, not sure :confused: Something to do with the master cylinder being below the caliper height and having excessive flow of fluid back through the cylinder(pad knockback?) Would mean pumping the brakes to get a full pedal. I'm trying to keep my cylinders nicely between the height of the fluid res and the calipers, as you know can be difficult on some strat replicas.

[Sptwoman]

I used the Tilton site to request m/c sizes for my current set up and received this reply.
There is no good solution based on the dimensions provided with a
reasonable amount on pedal effort. Increasing caliper size and rotor diameter are expensive if you already have the parts. However, raising the motion
ratio at the pedal to 5:1 provides a reasonable amount of pedal effort with a
.625" master cylinder in the front and .700" master cylinder in the
rear.
We cannot guarantee 100% satisfaction with the results since we must
make estimates on the center of gravity height, tire friction coefficient,
brake pad friction coefficient, how much force you prefer on the pedal, and
other factors.

Therefore it's increasing the ratio or fitting a servo as agreed already!! If the current ratio is 4:1 and the twin remote is 1.91:1. Is it as simple as multiplying 4 X 1.91???

[Sptwoman]

OK, last stupid question then I'll quit. Can I fit 2 individual remote servos for F&R use rather than the SVC twin unit?

[strat6v]

Yes.But why? Have you got two single ones already?

[Sptwoman]

A couple of reasons... the SVC is 1.91:1 ratio, a little high considering the Tilton comments and it's a fair size and price!! I can get a 1.65:1 ratio and other ratios compact from here (http://cgi.ebay.co.uk/Remote-Servo-all-single-line-brake-systems_W0QQitemZ160117277605QQihZ006QQcategoryZ27 380QQssPageNameZWDVWQQrdZ1QQcmdZViewItem) which could provide a flexible and neater installation config at half the price...

[strat6v]

good find Allen. space is at a premium.

Don't know how you'd go on fitting one if you wanted/had throttle bodies :confused: Forced induction i think may be plumbed to the blower inlet?

[Sptwoman]

Is the 1.65:1 ratio ok? This would give a 6.6:1 result I believe. If I go to the expense of a complex induction set up then it'll be off for a full tilton mod I think.....I just want it reasonably simple at the mo so I can drive it soooon :o

[strat6v]

vac pump :)