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Libra + GTM wheels + 304mm Disc/AP Racing 4pot? 
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Post Libra + GTM wheels + 304mm Disc/AP Racing 4pot?
Can you fit the MGF 160's 304mm discs with AP Racing 4pot calipers while using GTM standard wheels?

SAS

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2000 GTM Libra 1.8VVC 145BHP


Fri Oct 04, 2013 12:40 pm
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Post Re: Libra + GTM wheels + 304mm Disc/AP Racing 4pot?
No

Bob

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Bob S.
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Fri Oct 04, 2013 8:24 pm
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Post Re: Libra + GTM wheels + 304mm Disc/AP Racing 4pot?
google www ultimate mgf brakes this site will show which wheels have the offset to clear these brakes


Fri Oct 04, 2013 8:36 pm
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Post Re: Libra + GTM wheels + 304mm Disc/AP Racing 4pot?
Bob, any more info where the problem lies? Is it the wheel rim's inside surface or the back of the spokes etc?

Mark, yeah I've seen that info but if I really need new wheels then this project will be a non-starter.

SAS

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2000 GTM Libra 1.8VVC 145BHP


Sat Oct 05, 2013 11:58 am
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Post Re: Libra + GTM wheels + 304mm Disc/AP Racing 4pot?
I remembered later that you had done a lot of work to make the rear mk3 suspension arms fit your wheels so you won't want to replace the wheels. I have pro race 1.2 with 18mm offset as recommened by gtm under rdm do you know what the offset of your wheels are if the difference is not to much you my be able to space your wheel out to give the clearance you need. Rimmers were selling some metro rear wheel studs off cheap that are same as fronts but slightly longer these may do job with a spacer


Sat Oct 05, 2013 1:10 pm
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Post Re: Libra + GTM wheels + 304mm Disc/AP Racing 4pot?
I haven't done this conversion or researched it to much but I think it's to do with the thickness of the spokes. The only cars that I've seen with these calipers have 17'' wheels with [very] flat spokes or 16'' wheels that would suit an MGTF with these brakes.

Bob

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Sat Oct 05, 2013 3:45 pm
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Post Re: Libra + GTM wheels + 304mm Disc/AP Racing 4pot?
Indeed I did Mark and it paid off, I do like a challenge.

Thank you both gents for the info, I think it's time to bag me a cheap set of APs and fire up the Mission Impossible theme tune. 8)

SAS

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2000 GTM Libra 1.8VVC 145BHP


Sat Oct 05, 2013 7:16 pm
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Post Re: Libra + GTM wheels + 304mm Disc/AP Racing 4pot?
I have looked at how you fitted rear suspension again where you had almost no clearance on rear wishbone I can get 25mm thick wood in with room left with 18mm offset wheel so I think yours are 42mm offset which same as metro so will have even less room than you would with mgf wheel of 30 - 35mm offset so you may need a big spacer if that's what you are thinking of to get the caliper in.The variation in wheel offset will also affect the scrub radius.The info on rdm gtm web site said "to make the steering communicative without too much kickback the scrub radius is 11mm positive"but didn't say what wheel offset achieves this .Another option I have seen suggested is space the calliper inwards and use a two piece disc to move the centre line of disc inwards .You could use a metro solid disc machine most of the pad area area away except a small area left as a mtg flange to bolt the pad section of big disc behind it to move it inwards as there is room between existing disc and track rod end


Wed Oct 09, 2013 9:20 pm
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Post Re: Libra + GTM wheels + 304mm Disc/AP Racing 4pot?
Thanks for your further info Mark.

Studied my wheels which are Dytec 16 x 7.5J with 205/45 tyres. I measured the distance from the inside rim edge to the mounting face and got 145mm then I used this handy calc: http://www.rimsntires.com/specs.jsp which gave an offest of 36mm +ve.

I don't really want to have to faff about cobbling together custom discs (probably get spendy), if I can't do this with off shelf parts I won't bother.

My current thinking is i'm prepared to spacer out the wheel, spacer in the caliper and remove matarial from the caliper body to make these fit. Probably a combo of all three while trying to minimise 'uncentering' the caliper off the disc and making the wheels stick out to far.

SAS

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2000 GTM Libra 1.8VVC 145BHP


Thu Oct 10, 2013 1:59 pm
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Post Re: Libra + GTM wheels + 304mm Disc/AP Racing 4pot?
I thought your wheel would be 7inch wide same as mine this I why I was 6mm out estimating your wheel offset as you have about 6mm more wheel either side the centre line so the difference in offset between our wheels is 18mm so it looks like it will be easier to find the extra clearance you need. I wish I could find out what offset is best to give the best steering feel rather than what's best to fit the brakes in


Thu Oct 10, 2013 8:12 pm
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Post Re: Libra + GTM wheels + 304mm Disc/AP Racing 4pot?
Not sure if it helps at all to your situation but you might be able to calculate from what i mention below.

I have 7" team dynamics pro 1.2 16" on the front of mine with a 30mm offset wheels and the mg 4 pots fit behind the wheels fine with plenty of room to spare.
I have just bought two 8" team dynamics pro 1.2,17" (same wheel) with a 20mm offset for the rears and this has brought the wheel further out towards the road but also using every inch i have spare on the rear arms as i i am running the z cars rear arms.

If you need me to measure anything drop me a line or if the car is mobile you can pop down and physically try my rims on yours yourself?

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Fri Oct 11, 2013 2:21 pm
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Post Re: Libra + GTM wheels + 304mm Disc/AP Racing 4pot?
Well I got some cheapish used APs. 1st problem was seized pad pins - boy that's a bad design right there. Steel pins with a sprung expanding clip into ally holes, great. Still I got most of em out just two short bits left in one side (I cut them in half to make removal easier). Will offer them up to the hubs hopefully this weekend to see what i'm up against.

SAS

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2000 GTM Libra 1.8VVC 145BHP


Fri Oct 18, 2013 10:46 pm
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Post Re: Libra + GTM wheels + 304mm Disc/AP Racing 4pot?
Well, so far so failure. APR calipers fit straight on to the hubs no problem, as expected. However the 240mm discs surprisingly have to be removed first as they are overall too tall and won't allow the APRs to fit between the back face of the disc and the hub mount points.
Not a great issue but it did mean they had to be removed 1st and I had to make up 6mm spacers to put on the wheel studs to 'mimic' the disc being in place.
The 6mm spacer size I got from measuring the thickness of the 240mm disc's mounting faces and I've assumed the 304mm discs are the same thickness at that point as I can't find any size info for that dimension.
Anyway, I offer up the wheel and the problem is clear straight away, the back of the spokes hit the caliper's outer face. Slowly adding more spacers between my 'brake disc 6mm spacer' and the wheel itself indicates that 11mm (prob need 12mm to be on the safe side) is enough to clear the calipers.
The ID of the wheel presents no issue as there's enough space between it and the furthest out point of the caliper.
Studying how the caliper fits indicates I can't make any adjustments there to help solve this.
12mm spacers was maybe more than i'd wanted to have to use but that is not the only problem; 1, studs are too short & 2, the wheel no longer sits on the central hub.
This means just for them to fit i'd need 12mm thick spacers with built in wheel centres and either stud extenders or longer studs.
How this will affect suspension geometry & the actual driving of the car I've no idea as yet.
New wheels are not an option I want to consider.

Any thoughts other than clean em up, paint & resell em?

SAS

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2000 GTM Libra 1.8VVC 145BHP


Sat Oct 19, 2013 7:52 pm
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Post Re: Libra + GTM wheels + 304mm Disc/AP Racing 4pot?
Persistence pays off, 12mm thick hubcentric spacers (plus longer studs) provides just enough clearance to allow the APs to fit.
The 304mm discs have the same fixing face thickness as the 240mm (6mm), so my original figures for the spacer thickness required are unchanged.

The spacers I got were a bit of a mixed bag as trying to get the correct thickness & centre bore combination proved tricky on my set budget.
First I got a pair of 12mm thick but with 65.1mm (think they were for Citroen) CB but they were only £9 second hand. I ended up needing to buy some spigot ring adaptors to go between wheel/spacer(65.1 to 67.1) and spacer/hub(56.6 to 65.1) but with these they now fit perfect. I also had to slot the stud holes but that was easy on my miller.
Couldn't find another set of cheap ones so I then found some vauxhall 16mm thick with correct 56.6mm CB so these can fit direct to the hubs and use the originally fitted spigot rings that come with my GTM wheels. I will need to slot the holes to correct PCD and reduce the thickness down to 12mm on my lathe.

Attachment:
APR brake (1).JPG
APR brake (1).JPG [ 196.03 KiB | Viewed 10255 times ]


Rod is stainless steel to make new pad pins.

Attachment:
APR brake (4).JPG
APR brake (4).JPG [ 300.15 KiB | Viewed 10255 times ]


This is just temporary fitment so i can take measurements of effects to geometry etc and how well the wheel sits in the well.

SAS

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2000 GTM Libra 1.8VVC 145BHP


Mon Oct 28, 2013 7:35 pm
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Post Re: Libra + GTM wheels + 304mm Disc/AP Racing 4pot?
All parts fitted on front, just need to bleed the brakes and check for leaks. Then do a road test for general handling and any tyre/bodywork contact.
If all that goes ok i'll fit the rear spacers & longer studs.

Here's some pics sort of showing the difference (LHS spaced & RHS normal):
Attachment:
APR cal fitted (1).JPG
APR cal fitted (1).JPG [ 118.24 KiB | Viewed 10211 times ]


Top of the wheel is still well within the arch's overhang.

Looking at spaced wheel from rear:
Attachment:
APR cal fitted (4).JPG
APR cal fitted (4).JPG [ 152.06 KiB | Viewed 10211 times ]


Will probably need to make new slightly wider mudflaps.

SAS

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2000 GTM Libra 1.8VVC 145BHP


Sat Nov 02, 2013 8:31 pm
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