Differential Bushes

The differential has been sqeaking and nods up and down under load so it was time to get some new bushes.

Both sets of bushes are from – the main rear diff bush is the E30 188mm part – PFR5-300H from the heritage series.

The front two bushes are the same ones used on the front wishbones which is a Ford TCA bush; PFF19-102H also a heritage bush.

The heritage bushes are polyurethane same a the normal purple ones but in a darker OEM black colour.

Here’s a small video clip of the rear diff bush on video which shows the seperation:

Step 1 remove the differential, this was relatively straightforward. Unbolt and drop down with the jack.

Removed diff looking a little dirty, good time to give it a bit of a clean.

The rear bush – the middle part is separating from the outer part leading to excessive movement.

Removing the old ford bushes with the press

There’s some surface rust but overall not too bad.

Old ford bush next to the new poly bush.

Test fitting the diff hanger with the new poly bushes (some foreshadowing going on here)

Used the power saw to chop out the old OEM bush

Fitting the new powerflex bush, these always go in so easily compared to OE bushes.

This one has a big washer either side of the bush to keep everything in place. In addition to this is need two more small washers to space the bolt to the diff hanger (more foreshadowing, there 7 layers that need to line up here).

While everything was taken to bits it was a good opportunity to powdercoat the diff hanger with a fresh layer. Some of the original had flaked off and there was a little surface rust. Not much easy to clean up. Here’s the coated part baking next to the heat lamp to cure the powder.

Finished part cooling down, this is the ‘matt black’ finish which is still a bit glossy but has a bit of a rough texture.

Fitted back on the diff with the new poly bushes looking very shiny again.

So, the foreshadowing. This is after trying to fit the diff the first time. Couldn’t get the large bolts in on both sides. Ended up bending these hangers, so took the diff out, and both hangers. Bent the one that got messed up back into shape. Both got a new layer of powdercoat too. Re-fitting took a long time, it was easier getting the mounts back into the chassis than bushes into the mounts. However it took a lot of fiddling to get them seated in. This was with the rear bush held up with a screwdriver so it could move around a bit.

The new rear diff bush has a much tighter tolerance than the OEM one and required two washers either side of the bush. Took a load of fiddling to get all 7 layers (hanger, small washer, large washer, metal rod the bush sits on, large washer, small washer and finally the hanger on the other side).

Yes it did go dark while getting the diff back in. Here it is back in place.

The squeaking is gone, power transfers through the drivetrain smoothly. Overall bit of a pain but well worth it.



Engine and Gearbox mounting bushes

Recently the alternator hit the chassis when I changed direction, a good indication that the engine and gearbox mounts might need some attention. Unfortunately the alternator bearings were damaged due to this impact. I therefore ordered a new alternator (with the aim to rebuild the old one as a spare).

I then also changed the engine mounts & gearbox mounts. I used polyurethane from Duraflex (they sent the wrong bushes first time, but did swap them out after I sent them back for the right ones, did take a while before they responded to emails though so you’re aware if you choose to get some of these). The original engine mounts were supplied by Marlin so I didn’t have specific part references for them.

They are 35mm thick with M10 studs, the closest I could find were Land Rover Defender gearbox mounts. I ordered the ‘soft’ variant which is 70 shore. They had mounts for BMW gearboxes, went for the ’80 shore a’ ones which is the normal hardness option for the bush.

Land Rover gearbox mounts:–duraflex-urethane—-nrc9560-284-p.asp
BMW Gearbox mounts:–gearbox-mounting-257-p.asp

The engine is under much better control now, I get less oscillation / vibration into the front wings and feel better now when driving.

I also had two worn out cracking ball joint boots so I changed those too.


Gearbox Mounts

Old BMW bushes compared to the new poly bushes. The new bushes are a bit chunkier (same height)

Here’s the gearbox mount cross member – had to take this all the way out to get the new bushes in place, a little bit fiddly.

After some swearing the new bushes are in place with the cross member bolted back in.

As the new bushes are more chunky than the old one ones I had to use the deathwheel to grind down this spanner to fit between the chassis and the bush to hold the bolts when doing up the nuts inside the car.

Engine Mounts

Removed the bonnet and both side panels for this job:

Jacked up the engine after undoing the lock nuts until there was enough clearance to get the old bush out.

A comparison between the now deformed bushes and the new poly bushes. The studs are a bit longer on the new one so the engine needs to be lifted a little higher to get the new bush in (on the passenger / intake side)

On the driver/exhaust side the steering column linkage is in the way of lifing the engine high enough to get the bush out. It was much easier to take the 4 bolts out that hold the engine mount to the block and pivot it out the way.

Here with the new bush fitted and bolted down:

Alternator Change

Big ol hole where the old alternator was removed, added a small notch in the chassis here to allow more clearance in future.

I got the new alternator from in Denmark, mostly because I needed a glow plug control module for my daily and they were the only people in Europe that had stock at the time! The new one is very shiny!

New alternator in place, added a new v-belt while I was at it as the old one wasn’t brilliant anymore.   

Here’s the new alternator hiding away among intake and water pipes!

The really nice thing about the new alternator is that it charges straightaway after starting the engine. The old alternator needed you to rev up past 3000 rpm before it would start charging.

Ball Joints

These don’t last super long every few years I need to replace them, these were not damaged from dirt ingress yet so I was able to just change the boot (sourced from ebay ej-parts size 16/31/23). I did fit one new ball joint as I didn’t have enough time to wait for the boots to get it through the MOT this year so I was able to pick one up from Euro Car Part locally.

Yeahy rotten rubber (this is now an MOT failure, these might have squeaked through as they were not cracked all the way though, but it was time to change them):

One new ball joint fitted:

This ones pretty bad, but the ball part of the joint was still good.

New boot from ebay with the mounting hardware from the old boot

Reassembled, old ball joint with new boot:

Still to do are the differential bushes – the stock BMW M bush (from the Z3M) has a lot of movement, the centre mount hold is tearing out of the rubber. Additionally the ford TCA bushes used to mount the front of the diff to the chassis feel soft and are squeaking quite a lot. If you move the car by hand with a gear selected the diff does a nodding dog impression. I’ve got some poly bushes to install in the near future for that too.


New front wing stays

The front wing stays rusted and broke again, did a temporary fix a few months ago, but finally it’s time to make some new ones which will hopefully be more resiliant to the elements.

Started with two 1 meter 10mm diameter solid rods

A piece of bar to turn into the bracket that will hold the rod on to the front uprights with a U clamp (51mm u clamp)

Bracket cut shown with U clamp.

Test fitted to the uprights

Used a clamp to hold the round bar to the bracket to get a it roughly lined up.

Used a caliper to evenly space the round bar away from the alloy wheels

Held in by hand for a better view of the bracket and round bar

Tack welded the round bar to the bracket

My temporary workshop setup – don’t recommend using a workmate for welding due to the risk of burning wood and fire. Use a metal welding table, which I don’t have in my garage. Grabbed the round bar quite far away from the weld so it was fine. Also used a TIG so no splatter.

I’m still a total amature at welding but these are OK

The main thing is that is holds together well. The angle grinder hides the bad.

One of the most time consuming parts of the build was creating a jig so that all four final bends ended up very similar.

It may only look like two bends, but there are hours of measuing, eyeing up and carefully deciding where the bends need to go.

The rod lines up with the holes on the carbon wings.

Now here’s one of those things that happens all too often on a project – the rods ended up 10mm too high on the first go. This is jig MK2 with the height adjusted. It did mean having to straighten out the rod and rebend it to the right position.

Here’s a test fit of the front of the rod bent into place

The jig is holding the back up.

Left to right the mount positions are little way off on the back, so some creative bending and P clip positioning evens out the rod placement.

The back bent into shape, again two bends took many hours to get to the right position.

Here are the P clips that will mount the wings to the rod

First test fit of the driver side, got some really nice new A4 grade cup washers, bolts and nuts from Westfield Fastners to finish it off.

Test fit on the passenger side. The wing was too close to the tyre so this one needed a bit more fine tuning to get it right.


A view from underneath with the wheel off.

There is enough gap between the tyre and the carbon, looks quite close from this angle. If there are problems it is easy to tweak the bends to create more clearance.

Before and after, the before is version 3 of the mounts which also failed eventually.

Ahh shiny parts!

Engine Work

Fuel pipe refresh, car pee’d all over the floor!

Car pee’d on the floor…

It’s a bit drippy here at the back, but also at the front on to the start motor – not overly safe and smelled pretty strongly of fuel.

The main leak is here at the back between the hardline and the hose. The hoses have gone quite hard with age. There is a flare on the copper pipe.

All the fuel hose is 12-14 years old, this was visually the worst – the main picked pipe which is most exposed to the elements. The rest hard gone hard but were not cracked yet.

Emptied 25ltrs of fuel out the car using the Power Probe – all power disconnected on the car, hooked the probe up to the battery and switched 12v on the the positive side of the pump. Drained the tank very quickly into fuel cans.

Brand new hose up front for both the feed and return. Although these pipes all looked OK it was worth changing everything while the fuel system was drained.

New pipe from the tank to the first filter, to the pump, the next filter and then down the copper pipe where it was leaking. Also replaced the return rubber line.

Here are the rest of the old pipes that when in the bin, these had gone pretty stiff especially when compared to the new pipes.

All back together again! Used the power probe to prime the whole fuel system and check for leaks before starting the engine – fired up instantly, no waiting for the fuel pressure to build up when you prime the systems.

If you’re going to do any work on rubber hose, this tool from Sealey is invaluable, cuts nice straight ends every time!


Front indicator stalks refresh

The front indicators were starting to rot pretty badly, replacements are not very expensive so I decided to change them for new.

The new ones are little bit shorter than the originals:

Old indicator:

New indicator stalk – I like to proportions of the placement much better between the headlights, spots and indicators:





Seat Repair

The Cobra Roadster 7 look nice, but the construction quality is questionable at best. After 6500 miles the driver seat broke in two. I’m very happy the nice SVA man insisted on the seat belt bar as one of the major fail points on the first pass at the SVA test:

I took the vinyl and padding completely off the base, the back rest I only removed about 1/2 as it looked it was going to be difficult to get it all back in the orignal positions:

Just welding the pipe back together would likely have resulted in a failure quite quickly. Therefore I added extra metal inside the tubes for strengthening, here before being cut to length checking for fitment, the one other otherside as a bend due to the position in the break:

I then drilled some holes through the tube for welding the metal to the tube, the extra metal is visible through them: 

Time to fire up the welder:

I welded in the extra metal to the tube through the holes, and around the tube to join it back up again:

In addition to the metal in the tubes I also added plates either side of the seat over the whole bend:

Both sides completed with some paint over the top

Finally the seat needed reassembly, the vinyl stapled to the wood backing

Getting the vinyl back in place with the least amount of wrinkles was a bit of challenge

Next sides went on, these are connect with hog rings. I bought a specific set of pliers for installing the hot rings but it was still quite challenging to get them in place.

Finally I install the seat back in the car, this one will be the passenger seat for now:


Upper wishbone refresh and wishbone mounting rod

I changed the upper bushes today. They were rally design ones, which I’ve now replaced with Powerflex. I thought the bushes had worn as things didn’t look straight anymore. Turns out it was actually the rod which was bent and the bushes are OK. I’m going to use two of them on the diff mount (still original rubber mounts) and keep the other two as spares:

It’s pretty clear this is not so good, both sides were bent:

As I don’t have replacement materials to hand as a temporary measure I’ve straightend out the rods. Here are some sizes for reference:

Installation of new bushes:



There are powerflex product number PFF19-10 – also available in the black series which is a higher shore hardness: PFF19-102BLK


Reassembly, paint, lighting, electrics

The rear wings, tub and spare cover are back from for some touch up work and removal of all the stone chips on the wings! The wings were starting to look more stone chip hole than paint on the front. To protect the wings this time I purchased some 3M VentureShield from – I made a pattern using paper first then cut out the 3M stone chip protection film and applied. It took a lot of soapy water and work with the squeegee to get everything stuck down.

After fitting the stone chip protection film, I installed the new 3D printed light covers:

Wiring updated for the new inner LED lights:

Stuck the rear tub back on, this time using A316 stainless ‘A4’ nuts and bolts, these shouldn’t go rusty as easily as the previous 304 stainless ones. Got the nuts and bolts from

Decided to use vinyl wing piping from instead of the rubber trim that’s been on there since 2005 (that had started to go solid). The texture on the trim is very nice.

Next it was time to tackle some electrical, this tool from (via is an invaluable tool for dealing with 12v car electrics. It will tell you if you have a ground, or a positive (and how many volts), plus you can use the switch to send a ground or 12 volts to the item your are connected to. A good way to test relays, bulbs, LED polarity etc.

Reconnected the 4 pin water proof connectors and tied up the excess cables out of the way of the tyres.

These are new two pole Lucas 403 bulb holders and a very cool set of LED lights that output both white and red light spending on which pins you connect up. They cover reverse and fog, which means I can run twin fog / twin reverse lights! The old Lucas 403 holders were starting to look a bit rusty so the new ones were good to get anyway.

Finally, an extra cross over cable is needed to bring the 12v+ fog/reverse to both sides of the car:

Reverse on!

Fog on!

Finally, due to the indicators now being LED they ran in super insane broken bulb mode. As such the flasher relay needed to be swapped out. I had gotten an LED flasher from S-V-C it’s pin out is reversed from the BMW flasher relay and the ground is on a wire from the top. The flasher relay comes with a polarity swapping attachment so it goes right into the same connector as the stock flasher. The ground I’ve attached to the same location as the horn and other steering wheel wiring grounds.

Finally, some assembled shots:


Rear rust clear up

Doing some clean up work, the Sportster has been on the road for a while now so it was time to check for rust and clear anything up

Little bit inside the shock tower area, most was on the metal upright towards the back of the car.

More from inside the shock tower

This part is covered by the tub down to where the E30 A arms mount.

Under and below the tub area in the rear

The good news is that it was all surface, no structural issue. The worst part was the end of square bar under the back runs along the tank.

Cleaned everything up with a wire brush on the angle grinder, treated with loctite rust remedy and painted with chassis and rollbar paint. Also to go on later some underseal with waxoil.


Alloys are ready for rubber

It took 1 halfords referb kit (minus paint as there was not enough), 6 1200 grit wet and dry sheets, 2 cans of primer, 3 cans of Honda Nobel Silver and 2 cans of laquer + hours and hours and hours and hours of sanding!! But the alloys are finally ready to have some tyres added. A set of Bridgestone RE720 in 205/65/R15 are ready to go on these 15x7J rims.

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