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740/940 XC90 T6 brake conversion info/reference

Swedbrick

Active member
Joined
Oct 12, 2016
Location
Netherlands, Source of Grolsch
Since I'll be upgrading the brakes on my 7-series to a set of XC90 T6 ones, for which I'll also be designing the brackets, dust shields and e-brake adapters, I created this tread for reference to anyone looking to do the same.

The setup I'll be working with 336mm rotors front, 308mm rotors rear
sMQW9Kll.jpg


These are vented both rear and front
LRShJIPl.jpg


The front shown here with the ruler of a total width of 36cm
fbDZvZTl.jpg


The rear as well
9n7TedPl.jpg


The fitment with the wheels I'll be running also shown below, these are 17 inch Revolution Motorsport Millenium Rally wheels, with a stepped inside barrel to allow for bigger brakes
QV613edl.jpg


rg81Dhul.jpg
 
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The front setup

The original bracket from the kit I'll be replacing, its from what I can tell the old version of the l-m-r.se kit. I'll be replacing it since it rotates the caliper upwards, which I dislike due to the weight not being centered on the steering axis as well as the suspension and I will also get rid of the nut behind the bracket, which was pretty hard to access.
XvxkokXl.jpg


I found a new rotation for the caliper I liked (approximately vertical on center taking caster into account, after modifying the old dustcover.
1lta48al.jpg


Here are the dimensions on paper based on the center of the hub, for those planning to make these themselves.
ixlATNSl.jpg


Got my new bracket designed and got it printed in PLA for testing.
4SF00adl.jpg


Clearance looks good, the bracket should also be a bit stronger. Both original caliper bolt holes on the strut were now tapped to M14x2.0 for a simpler setup and install. The original 15mm spacers from the previous kit were used, which I'll be finetuning later, to center the caliper bracket (expecting to go to a 14mm spacer).
jo7wH6al.jpg


Clearance to my 17 inch wheels also looks great.
phnuLVal.jpg


A little side by side of old versus new, I also checked but not shown here, and as expected the bracket also works for the other side.
2hR8CmKl.jpg


Stoked for the preview of my new setup:-P
6kYC8Jxl.jpg
 
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Rear setup part 1

Hi, thanks for the positive comments all!

I'll probably orde a couple more by the time I get around to the order since with steel that's usually pretty affordable. So if you want a set by the time I'm done, let me know via a message. Brake lines could probably be adopted from stock, but for the rear a bit of hard-line rework would be required.

Anyway, I continued last week with using my brother's 740 as a test for the fitment. Starting off with the discs:
jTooz02l.jpg


Those fit so I continued with trying if I could fit the new discs over the old ones to be able to retain the stock handbrake setup, unfortunately machining would be required. So I'll move towards adapting the xc90 setup, which looked about the same except for the diameter:roll:
8HTuCY3l.jpg


With the new disc back on in checked the caliper fitment
k6Ol4vHl.jpg


The brake line clears the shock, and should be able to be routed in parallel to the trailing arms, with a bracket and a little shortening of the stock copper lines. I'd rather avoid it, but this looks to be the most suitable solution.
0wMrttxl.jpg


I then went to cad and worked out some bracket ideas, also for my brother's drift setup, since that was part of the deal for stealing his car:-P
IfrBDzkl.jpg


When those were fitted on the car I realized my mistake haha, so I'll be sourcing a second rear axle for the prototyping soon, that will also go towards the drift project when I'm done designing, at least the diameters I measured were correct:-D
EYPvnaml.jpg
 
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Axle sourced, rear setup design continues

With a little trip to a local friend, who has plenty of 7/9-series around for Banger racing, I sourced a fresh 1:3.54 open diff axle to be used as a measurement jig. About a weeks worth of coffee and head-scratching later, I came up with these :oogle:
lqtJcQCl.jpg


The hardware was stuff I had laying around, but sufficed for a fitment check. The whole ordeal bolts up to the XC90 rear caliper as shown below.
sZ0JhdEl.jpg


As for the front, here the dimensions I ended up with for the caliper placement, for those trying to make their own adapters:
00EIbMFl.jpg


And yes the stock caliper spacing is actually exactly 83mm (3 1/4"?), this confused me a bit so I printed an idiot check :lol:
LgDBsvWl.jpg


This placed the calipers on the disc with about 2mm clearance between the caliper and the disc as desired:
s6UoXLHl.jpg


Here shown with me holding the somewhat floppy PLA print, but the dimensions should be perfect.
j88jd5Ql.jpg


Ending with the rear view of the setup, wherein it seems that the brackets would clear the axle, but they actually do not, since that ended up requiring too little mounting surface to the stock caliper location, so that is why the design is split.

The center circle on the axle is tapered and could not be used for support, but if the brackets decide to move, the clearance is sufficiently small that the ring can be used for some emergency support under heavy breaking if that makes sense. The two flats in the design are made to have a slight interference, so they can be sanded to a perfect fit.
GjxiB5Xl.jpg


The next step will be to create fitting dust shields and getting the xc90 e-brake adapted to the 530 axle, I'll be ordering new brake shoes and a spring kit somewhere in the coming weeks, to get the ball rolling
 
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More rear fitment pictures, now with daylight

Since I was wondering about the fitment within the wheels of the calipers I fitted up the to be used 17x8j et13 wheels for the rear to the axle:)
BC5Hkbnl.jpg


Plenty of clearance all the way round, with the discs even looking a bit tiny:lol:
n4jB3XIl.jpg


The brake line end on the caliper just pokes past the edge of the wheel, and should clear any extra width tires nicely as well
kavH3Fgl.jpg


For comparison the dust shield for the stock brakes in the opening
8kPHicrl.jpg


And a little overview of the new setup for fun, those poor axles with the new amount of rubber haha:roll:
IGOUHXOl.jpg
 
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E-brake parts are in

The brake parts arrived yesterday, so I got straight to some measurements on the old dust shield and proceeded to come up with the setup as below:-P
nyAlDhml.jpg


I also ordered a full drum brake spring kit to make the install as legitimate as possible, and was able to reuse the stock spacer fork thing, since the xc90 is a little more complex, which should not be needed. The spacer block had a width of 40mm compared to the 7/9-series stock 33mm so that will have to change, as well as the separator device, going from a minimum width of 45mm -> 58mm.

It's a slightly complicated mechanism to recreate, as I want to retain my standard cable for the sake of maintenance, and would like about 6-8mm of expansion, since the xc90 pads have about 3mm of exterior material available. I've created this little overview below for the explanation of how the mechanism works, with the black cable being connected to the lever in the car.
w4Sbtgpl.jpg


I left the cover slightly loose in the space to prevent binding with the disc, with this plate being about 4mm thick, the rest of the dust shield will be added in thinner sheet metal, with some dimples/recesses for strength:)
QeYJOr2l.jpg


The setup inverted in the disc for an idea of the fit:p
btKuepjl.jpg
 
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I just got the front setup installed, and the rear setup prototyped in v4 by now:-P ready for installation, the front brakes really well thusfar. I also installed a faster 95+ booster from the later 940 which has a different brake input response for less braking effort.

When I get the rear in order, I'll update here!
 
I just got finished testing v4, which will work, including the parking brake, attaching to the axle by means of the axle retaining plate bolts
DiBsy4Al.jpg


The xc90 puller was modified to work, and it all fits up like so:
4YhpJ9Dl.jpg

3gMtnLNl.jpg


The puller mechanism got filled by a weld, and recieved a new 6mm hole for the puller pin.
OpZ7FBKl.jpg


Which I found out is available in 2 versions, of which I got the non compatible one on the car:lol:
3bTlboUl.jpg


It fits up like this for now, aluminium for the dust shields and new parking brake cables are on the orde list, the fronts have already been fitted with 12mm thick steel versions of the test print:nod:
IWnOsvNl.jpg
 
Sorry for not updating here for a while, but here to round off this thread:)

The front steel arrived in 12mm thick, along with 10 and 4mm spacers, ready to be painted and bolted on after sandblasting.
NegR4Yvl.jpg


As you can see, it all fit up great as expected.
hJCtPotl.jpg


The brake hangers had to be adapted slighly for my shorter lines, which shouldn't be necessary, so make sure you get extended brake lines if you want full lock, this is on my to do list:-P I swapped my 16v booster to a 95+ one from a 940 so only a deletion of the secondary brake lines was needed in my case to make the lines work after some rearranging at the distribution block.
T5ethd2l.jpg


I ordered the rear setup in 8mm steel, which arrived as such
OtjfgDil.jpg


The support for the parking brake recieved a little weld bead with teh mig to keep it in place and the holes got tapped to receive the m10 bolts.
2r7oL8Vl.jpg


The total setup then got a pre fit before paint to confirm correct fitment.
pPJbfocl.jpg


I also welded on support brackets for the parking brake retention springs so it worked out like this:-D
OI9M0Yxl.jpg


The plates also received custom aluminium dust shields to keep out the splashes and a plate was added to receive the stock 740 parking brake cable dust boot
Oe322Xel.jpg


It all fitted up like so to my relief:cool:
Qt1FyO3l.jpg


I routed the brake lines to just above the axle stand supports, and will be adding brackets and p clips with rivet nuts to keep it in place.
wWdwzcFl.jpg


For those willing to work out their own setup, I'd be willing to provide the dxf files for the plates in exchange for a small contribution and a promise to keep the design only for personal use;-)
 
For those willing to work out their own setup, I'd be willing to provide the dxf files for the plates in exchange for a small contribution and a promise to keep the design only for personal use;-)

You should just sell the parts. With your name engraved on it or something
 
Great work. Very useful to see what's involved in adapting to a different rear e-brake setup.
 
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