The Triumph Dolomite Club - Discussion Forum

Im probably going to get castigated here for asking? I would guess anybody on this hallowed forum who has a modified car, might want better brakes, I have a Trackerjack kit fitted, although they stop the car well enough but are a touch feel less, I would prefer some bigger discs so I can have some feel, is a PCD change to 100mm doable its only just over 3/16ths? has anybody done this, or even better has anybody got a set spare?????

I am hoping to get somewhere in the 300mm disc size, I have a pair of aftermarket discs for a cosworth 295mm I think, and a pair of ambassador 4 pots too, not shedding weight but better than some alloy bembros I have had,

ian.stewart wrote: ↑Fri Sep 08, 2023 10:53 pm I am hoping to get somewhere in the 300mm disc size, I have a pair of aftermarket discs for a cosworth 295mm I think, and a pair of ambassador 4 pots too, not shedding weight but better than some alloy bembros I have had,

Not sure about this...
Ambassador calipers are a four piston version of a T2000 caliper, offering no more braking force.

If you are not bothered by their weight,
Jaguar XJ12 have bigger four piston calipers intended for bigger discs.....



Ian

sprint95m wrote: ↑Fri Sep 08, 2023 11:23 pm

ian.stewart wrote: ↑Fri Sep 08, 2023 10:53 pm I am hoping to get somewhere in the 300mm disc size, I have a pair of aftermarket discs for a cosworth 295mm I think, and a pair of ambassador 4 pots too, not shedding weight but better than some alloy bembros I have had,

Not sure about this...
Ambassador calipers are a four piston version of a T2000 caliper, offering no more braking force.

If you are not bothered by their weight,
Jaguar XJ12 have bigger four piston calipers intended for bigger discs.....



Ian

First thing I will say is the clamping force is variable by altering the master cylinder bore size, fitting a servo, how hard you push the pedal or altering the pedal ratio to do so, they will all have an impact on clamping pressure, in reality its a balance between locking the wheels and knowing when they are about to lock.
Brakes, Generally, the area of pad is one of the benefits of 4 pots, by fitting big pads this gives more clamping area, and better heat dissipation. a bigger disc gives you more leverage against rotational forces and better heat dissipation, IMHO I will fit the biggest disc feasable just for that reason which in turn gives better feel too. for that reason. I never fit a servo either, they reduce pedal pressure but also reduce feel. and as they dont change the swept area of pad, or disc size, they dont actually improve your brakes ability to stop, just pedal pressure, and often forgotten in the equation, the final element of a braking system is tires, have small, skinny, hard, under or over inflated, that dont grip the road, the worlds best braking system aint worth a toss if the car is not gripping the tarmac. fit the best tires you can get.........
Princess callipers, they were the well known budget calliper that gave you bigger brakes, over the years I have had various brake setups, including princess callipers, which were superb, I, looking for a lighter setup changed the callipers to Porsche Bembros, almost the same swept area of pad and same piston displacement , the brakes went from stop on a sixpence ooooh im not liking this..........we eventually found out the Bembros flexed massively under load, where the cast iron princess ones did not,
Princess callipers,why I like them, they dont flex, there is a comprehensive range of pad material available, the pads are fairly big, piston volume is the same as a m16, so calculations for master cylinders is relatively easy, and the mounting the same as the M16
Braided brake lines normally have a impact too, as thy dont expand anywhere near as much as rubber ones,

xvivalve wrote: ↑Sat Sep 09, 2023 8:43 am https://www.ebay.co.uk/itm/132358921509 ... R4iNg47PYg

I have a pair, bought as an experiment, 15mm thick, TBH I wouldn't risk my life by using them, they are that badly made the tapered seat has only 3mm of contact before the nut can pull thru take that into account, in reality the wheel is only held on by 4 x 3mm ally rings and then, also, take into account the nuts need be machined so they will sit flush you are starting to run out of thread on the nuts too before the wheel will touch the surface of the adapter, lots of money and took 3 months to arrive.

ian.stewart wrote: ↑Fri Sep 08, 2023 12:43 pm Im probably going to get castigated here for asking? I would guess anybody on this hallowed forum who has a modified car, might want better brakes, I have a Trackerjack kit fitted, although they stop the car well enough but are a touch feel less, I would prefer some bigger discs so I can have some feel, is a PCD change to 100mm doable its only just over 3/16ths? has anybody done this, or even better has anybody got a set spare?????

SprintSpeed do some lovely alloy hubs that are Ford PCD so a variety of Ford PCD wheels could fit.

You can also get Alloy Wheels machined to your own PCD.
Image wheels is one company that springs to mind.


If you are not bothered by their weight,
Jaguar XJ12 have bigger four piston calipers intended for bigger discs.....


Jaguar XJ calipers will not fit directly to the Sprint upright as the mounting holes are slightly off.
They neeed to be plugged and re drill to suit.

My Project has XJS callipers which will be changed to possible WilWood at a much later date.

So do T2000 and Princess Calipers fit the Dolomite upright? I always thought not but happy to be corrected.

Sean

If the big princess calipers don't fit as they are, the solution might be the same as for the TR7, which they don't fit either - at least not properly. That was to dowel the mounting holes on the caliper body, and re-drill them a bit further in. The problem with mounting on the TR7 was that the pads hung over the outer edge of the disk by 3/16". That was still fine, but only until the pads wore down by half the thickness of the disc. Then braking became much more interesting.

I had those big Princess 4 pots on several TR7 Sprints, where they gave much more braking effort, due to the much larger piston area in relation to the TR7's 2 pot calipers - almost as much more as fixing the servo. But I also had wider tires so that I could access that extra brake force before the front wheels would lock - which always sets the limit on what brake force can be used, and hence the minimum distance in which the car can stop, etc.

As a note, pad area does not directly affect the braking effort (see Amonton's and Colomb's laws of friction), only thermal response and dissipation and hence fade (the pads allow for the maximum stopping force at their hottest temperature just below that where fade kicks in). There is, though, an indirect effect; in that they can allow for a softer (higher coefficient of friction) pad material for the same wear rate, and that will affect the maximum brake force.

Graham

new to this wrote: ↑Sat Sep 09, 2023 5:57 pm If you want 300mm disc your need 15 inch wheels minimum
as said Sprint Speed sell alloy hubs front and rear to be able to fit ford wheels

Im looking to see if I can get the front hubs undrilled then I can go for 4x100, or possibly CNC the stud holes out to 100 pcd and find some studs with a large spline, 4 x100 pcd really opens up the world of aftermarket wheels, I also have bought a set of early 80s alloy wheels that aesthetically I think work really well, plus I have had 3 other "Car People" look at my choice without any negative comments

ian.stewart wrote: ↑Sat Sep 09, 2023 10:07 pm

new to this wrote: ↑Sat Sep 09, 2023 5:57 pm If you want 300mm disc your need 15 inch wheels minimum
as said Sprint Speed sell alloy hubs front and rear to be able to fit ford wheels

Im looking to see if I can get the front hubs undrilled then I can go for 4x100, or possibly CNC the stud holes out to 100 pcd and find some studs with a large spline, 4 x100 pcd really opens up the world of aftermarket wheels, I also have bought a set of early 80s alloy wheels that aesthetically I think work really well, plus I have had 3 other "Car People" look at my choice without any negative comments

I asked them if they would make me hubs for my Stag wheels, but they said they couldn't , i couldn't use there alloy hubs as they were not big enough

Dave

What car uses 4 x 100 ?

new to this wrote: ↑Sun Sep 10, 2023 10:06 am
What car uses 4 x 100 ?[/color]

This what your after? 4X100 PCD list: https://www.wheel-size.com/pcd/4x100/

new to this wrote: ↑Sun Sep 10, 2023 10:06 am
What car uses 4 x 100 ?[/color]

Every 4 stud Vauxhall and Opel since 1980 and 4 stud VAG cars (VW/Audi/Skoda/Seat/Porsche) for almost as long. And a couple of less well known marques too. But just those 2 majors gives a gigantic choice of rims to use both in OE and aftermarket.

I understand Sprintspeed not being able to redrill their hubs to 114.3 for Stag wheels, that's upping the ante by 20+mm, over 3.4". But going from 95.25 to 100mm is nothing LIKE so fearsome a task, a radial increase at hole centre of only 2.375mm and might be possible.

Steve