gingerprince
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| posted on 20/8/10 at 08:10 PM |
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Sierra Front Calipers, Wheels and a Grinder...
So after having bought one set of 13" wheels that won't clear my front calipers
(here) I bought a different set - Capri Laser 6J13 as I'm sure I read this
is the most common type that people fit: -
 
Description
However these ones didn't clear my calipers either! My brakes are 260mm vented - are these bigger than what people normally have (Haynes sierra
manual suggest 240 is standard)? Do I have a non-standard setup and is this why they don't fit??
Grrr.....so, I got angry with my grinder...but I'm worried I might have gone too far.
This is what the calipers used to look like: -
 
Description
So I spaced the wheels with washers and gradually ground the square-edge off a bit at a time (using tape and spinning the wheel to see where it
touched). When it finally fitted it looks like this: -
 
Description
The wheels now fit with a couple of mm clearance.
The square edge has basically been "rounded" to fit the profile of the inside of the wheel.
 
Description
But now I've dismantled the brake, I can see that the inside profile is square, so the thickness of "meat" between the inside corner
and the outside where it's been grounded is probably about 8mm: -
 
Description
What sort of force is this bit under? Are these now scrap or is that still ample "meat"? I don't have much experience with the amount
of meat on other calipers to be a judge of whether it's enough or not, and I'm not an engineer so don't understand the stresses etc
that this bit of a caliper is under.
I've got a trackday a week on Wednesday so I need to figure out now whether I need to get me some new calipers and forget the slicks for now.
I've been for a spirited drive with a few heavy braking tests, but obviously nothing like the abuse it gets on track.
Honest opinion please? I suspect I already know the answer, but thought I'd ask anyhow...
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austin man
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| posted on 20/8/10 at 08:13 PM |
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that a lot of metal to lose, the caliper will have exceptional forces on it as you are staopping a rolling mass
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
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Howlor
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| posted on 20/8/10 at 08:20 PM |
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I was always told and I still use today, that if something looks right it normally is and if it doesn't look right then it's probably not
going to last long!
From and engineering point of view I don't think that it looks right.
Steve
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PSpirine
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| posted on 20/8/10 at 08:20 PM |
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Not very easy to tell from the photos' but I'd be very concerned where you ground the corner off (if you imagine a line going down the
middle of the grey ground off bit in your penultimate photo).
I've ground calipers in the past on a mini, but that was literally to lose 3-4mm on an edge which maintained the chunky thickness.
I wouldn't feel comfortable with these in their current state (which is not the same as saying they will fail).
Pavs
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RichardK
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| posted on 20/8/10 at 08:33 PM |
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No body can tell without the proper equipment, but my 2 pennenth says if ford could save that amount of material they would and the other is that
there bits on a car that you can take a punt and "Risk" it, brakes aint one of those areas.
Sorry its not what you wanted to hear but I wouldn't....
Cheers
Rich
Gallery updated 11/01/2011
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v8kid
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| posted on 20/8/10 at 09:03 PM |
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I freely admit I'm a chancer but thats one chance I'd take a rain check on. Not that it's a bad idea just that the original designer
mucked it up.
The sharp internal corner is one mother of a stress raised and the original designer got away with it 'cos he added a load of extra stress
resistant material which unfortunately is now no longer with us  On the plus side the worst that will happen is that you come to a sudden stop as it
all jams up - hopefully.
You can fit 260mm or even 280mm discs in a 13" wheel but not with the standard caliper or wheels.
Easy one first is to fit split rim wheels. The internal clearances are substantially greater than standard cast wheels and you can pick tatty ones up
on ebay for £60 - £70 each - I have bought 8 in the last 3 months. You can vary the inner and outer rim widths and add spacers to give radial or axial
clearance to suit your hearts desire
Less clearance but more available are compomotive CXR wheels which sit in the middle ground clearance wise. However you cannot alter them so had
better be good at measuring! Forget other 1 piece wheels these have the most clearance.
Other options are slimmer calipers. I don't know any standard manufacturers calipers which are slimmer. Some say pug ones are the dogs
proverbials but I could not source collaborating data when I was purchacing.
Wilwood do slimmer calipers at a cost and the slimmest are Hitech which in combination with split rims can give 285mm, allegedly. but I could only
manage 280mm.
On the other hand fit 240mm discs and put up with a 15% drop in performance. They are not so sexy but def locost.
I plumped for 280mm discs, split rims and HiTech F3 calipers but it was not cheap - one heck of a lot cheaper than the AP or Brembo alternative but
compared to OE stuff expensive.
I wasted time and money on finding this out - hope you can avoid the same
Cheers
You'd be surprised how quickly the sales people at B&Q try and assist you after ignoring you for the past 15 minutes when you try and start a
chainsaw
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andrew
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| posted on 20/8/10 at 09:51 PM |
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for what its worth find somwhere quiet with some run off give the brakes hell see if you can bust them youve still got the handbrake
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PSpirine
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| posted on 20/8/10 at 10:32 PM |
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quote:
Originally posted by andrew
for what its worth find somwhere quiet with some run off give the brakes hell see if you can bust them youve still got the handbrake
I'm not an engineer, but my issue with that would be that it potentially will hold up to a test like that, even if it's on super sticky
tyres and a hot dry day.
The problem comes where there's very little metal left between the sharp inside corner and the now much closer exterior surface.
This won't necessarily fail immediately, but will flex a lot more, and I would be more worried about developing a stress fracture over x amount
of cycles, rather than it being so weak that it'll fail the first time the brakes are used.
As mentioned, non-engineer opinion.
Pavs
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Mix
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| posted on 21/8/10 at 04:37 AM |
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Hi
I have to disagree with V8kid:
'On the plus side the worst that will happen is that you come to a sudden stop as it all jams up - hopefully'.
In my opinion, should the calliper crack all hydraulic braking could be lost.
Regards Mick
[Edited on 21/8/10 by Mix]
[Edited on 21/8/10 by Mix]
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Simon_k695
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| posted on 21/8/10 at 10:01 AM |
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If you DO have a shunt, even a minor one and the insurance inspector comes calling? You just KNOW what they will say, don't risk it. Willwoods
or a.n. other will end up being far cheaper.
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gingerprince
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| posted on 21/8/10 at 12:00 PM |
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Thanks all, kinda the responses I expected but second opinion worth getting.
I've measured up and even the Wilwood setup won't fit under my wheels based on the measurements on Rally Design website due to the
agressive taper on the inside of the wheels, so it looks like I'm trawling ebay for some replacement calipers sharpish, or cancelling the track
day!
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gingerprince
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| posted on 31/8/10 at 04:05 PM |
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Well I've managed to get hold of some XR4 calipers for peanuts which are pretty much identical to the ones I took off, so at least I can now to
Cadwell, albeit still on R888's!
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