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Vented disc conversion


Nick Jones
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Having now cooked several sets of pads on my Vitesse 2L, including some Ferodo DS2500, I'm forced to conclude that vented discs are the way forward. It's the track days..... and the Alps..... that do it.

I've bought a pair of Capri 2.8i discs and a spacer kit for the 16P callipers. I've also got full rebuild kits incl. SS pistons as the poor old callipers are looking a bit cooked too.

Usual procedure seems to be to

- space the callipers,

- redrill the discs and fit to the hubs ( centering is an issues a s Capri disc has 2mm larger ID)

- remove the dust shields (spacers used to maintain the original steering arm position

- refit hub/disc

- fit callipers with suitable spacers to centre the them on the disc (5mm supplied with spacer kit)

- find some method stopping the TRE gaiter rubbing on the disc......

 Lacks a certain engineering elegance....

I've measured a 4mm difference between bell height of the OE and Capri disc, with the Capri disc being the larger. On the face of it, machining 4mm off the inside of the hub would appear to correct matters and allow creation of a proper 64mm centring spigot as well. No need to discard the dust shield and no issues with TRE clearance.

obvious drawbacks

- Not directly reversible (spacers would be needed to refit OE discs)

- All of the extra calliper width will be outboard, which may lead to clearance issues with some wheels

So what haven't I thought of? Anyone done it like this before?

Got some spare hubs and enough stray bits to mock it all up..... but have used all my "stood up" time for today........

 Nick

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Nick I got the hub face machined off. The actual amount eludes me, but I didn't leave the spigot as you have suggested (doesn't seem an issue though)

I centred the discs rather crudely, using a tip from the courier mag. an O-ring sat on the hub, and IIRC the disc has a chamfer so it self-centred. A drill down the hub to mark teh discs, then drill. All seems to work just fine. And I have loads of clearance between disc and TRE. I used thick hard washers as spacers, including behind the steering arm (I think, can check later, but feeling hot/bothered and miffed as a nice lady has reshaped the back of my spitfire) Will take some pics too....

 

(beware, machining hubs went wrong first time. Can't work out why, but second time fitted hubs to a stub axle to prevent run-out, which worked fine)

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You're quite right, Nick, that this mode and the need to remove stone guards leaves the TRE very close to a hot disc.    This rots the boot, and of course any boot defect is an MoT failure ( if you get an MoT, which you should!)

I've moved to TREs that are enclosed and have a grease nipple on top.  I believe they are Standard Vanguard parts, bolt on, andbi was told inhad the last my supplier had but surely another can be found?

John

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1 hour ago, JohnD said:

if you get an MoT, which you should!

Already been MoT'd after the cut-off date.  I intensely disapprove of the moronic VOSA/DVLA MoT exemption.  Should have been changed to an MoT "light" to test the safety related features that the older cars actually have fitted with commensurate reduction in time slot length and maybe even modest cost reduction.

Returning to the original question, I also note that although the actual increase in disc thickness is ~ 7mm, the spacer kit spacers are actually 10mm - implication being that I either actually need to move the disc out 5.5mm to centre the calliper - or bin the nasty looking spacers that came in the kit and make some nice ones that are 7mm!

Nick

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Should that be an MoT "lite" as in American beer?   A gentler, more considerate estimation of the car's capacities, rather than roughly gripping it's underside private parts and prodding it with a sharp stick?

Can you turn down the spacers to 7mm?   Or are they too nasty?    I've bought wheel spacers that were apparently made from compressed sawdust, lightly dipped in aluminium paint, that didn't stand up to being run around the block.  They would fly apart in a lathe.

JOhn

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5 hours ago, Nick Jones said:

Should have been changed to an MoT "light" to test the safety related features that the older cars actually have fitted with commensurate reduction in time slot length and maybe even modest cost reduction.

Trouble is, the market is not that big for that sort of inspection, so it would come at a premium not a reduction.

There is a market for it for sure, but not big enough for the chains to train up their inspectors with the vagaries of classic cars which they might get, what, one a week?

If there was, then the scheme promoted by Fuzz would have more members. 

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On 7/23/2018 at 3:41 PM, clive said:

Nick I got the hub face machined off. The actual amount eludes me, but I didn't leave the spigot as you have suggested (doesn't seem an issue though)

I centred the discs rather crudely, using a tip from the courier mag. an O-ring sat on the hub, and IIRC the disc has a chamfer so it self-centred. A drill down the hub to mark teh discs, then drill. All seems to work just fine. And I have loads of clearance between disc and TRE. I used thick hard washers as spacers, including behind the steering arm (I think, can check later, but feeling hot/bothered and miffed as a nice lady has reshaped the back of my spitfire) Will take some pics too....

 

(beware, machining hubs went wrong first time. Can't work out why, but second time fitted hubs to a stub axle to prevent run-out, which worked fine)

Clive,

How did you get around the issue of the calliper sticking out past the wheel mounting face of the hub  if you move the disc outwards by machining the hub? Wheel spacers? I can't used spacers as the wheel/tyre combination I have is on the limit of poke already.

Been mocking things up this morning. There are a number of ways to skin this cat, but they all have drawbacks.

This supplied "kit" has 10mm calliper spacers plus 5mm washers to move the callipers inboard. This does basically work. The drawbacks of remain as per original post plus the calliper is very close (less than 1mm) from the hub. The kit does not include longer calliper fixing bolts,  which are sorely needed. Not in itself an issue, but kit incomplete!

The 10mm calliper spacers are 3mm bigger than they need to be to accommodate the extra disc thickness (7mm). We've knocked up some 6.8 mm ones from some aerospace Alu alloy we had in stock. Fitted with 2.5mm washers the callipers are now well clear of the hub but disc not central in the calliper. Machining 4mm  from the back of the hub would sort that and allow me to ditch the washers and even fit the dust shields, but then will need to relieve the hub and maybe the calliper slightly and the calliper will again be outboard of the wheel mounting face, though only by 2 - 3mm........

Had not realised there is so little to spare in the OE install. No wonder the TRs have big wheels!

Nick

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Nick, without taking a wheel off (been playing with the spit today after its rear was rearranged by a Alfa Mito....) I can make a few points 

I have approx 2mm washers between calipers and brackets.

I have spaced the steering arms, 3mm?

The callipers have signs of me using a grinder to give clearance. Not on the main faces..

Which reminds me, I currently run 14" K+N minilitish wheels. A few months ago I refitted the wheels after new tyres had been fitted. One front wheel caught the calliper. I relieved all 4 wheels, just an edge. The car has run GT6 type 5.5j wheels with no issues.

I can take the wheels off tomorrow, as long as it doesn't tip it down with rain here (though Gill would appreciate that for the garden)

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Bumper seems unscathed, bootid a bit crumpled along the rear edge and has become mis-shaped (probably not repairable, a shame as rust free) Rear light panel and valance shoved in, but now the assessor has been that has been substantially sorted with the aid of a hydraulic ram (brilliant, but potentially naughty bit of kit) He suggested that, so the car is OK for Border Raiders next weekend...

Oh, it was a stationary queue of traffic, A43 near Cherwell Valley. Not moved for a while, but a space opened up on the other lane. She went for it, forgetting we were there! Ho hum.

 

Back to brakes. If it stops throwing it down I will take the wheels off... Gill is very happy ?

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Senior Management also very happy about the rain as she was getting very bored with watering all her pots (well, if you will have 70-odd pots!) and water butts mostly empty.

Should you be in need of a new and unused OE Spitfire rear lamp panel........ I have one.  Hopefully not bad enough to need one as removing and refitting those is serious effort!

Very bad news about boot lid......  New ones very expensive and wrong curvature.

Nick

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